Chemical change: Materials Nottingham, March 2006 Polymers · Chemical change: Materials Nottingham, March 2006 ... Polymers in use (project, ... Chemical change: Materials Nottingham,

Chemical change: Materials Nottingham, March 2006

CLIL Teacher Materials 3-1 Rosa M. Melià Avià

Polymers



Polymers

Introduction to polymers (first period) Activity number 1: Let’s burn polymers! (first pe riod) Activity number 2: Polymers for containers, polym ers for everything (first period) Activity number 3: Checking at home (project, hom ework) Activity number 3: Polymers in use (project, home work)

Polymer synthesis (second period) Activity number 5: Basic ideas about polymers (se cond period)

Addition Polymerization (second period) Activity number 6: Consolidating new knowledge (s econd period) Activity number 7: Methyl Acrylate, the monomer. Polymethylacrylate, the polymer (third period)

Condensation Polymerization (fourth period) Activity number 8: Questions about polymers (fou rth period) Activity number 9: To stretch is wonderful: Synthesis of nylon (fourth period)

Chemical structure and physical properties of polymers (fifth period) Activity number 10: Eating polymers (fifth perio d) Activity number 11: Physical properties (fifth p eriod)

A step to the future (fifth period) Activity number 12: Explaining the history of po lymers (fifth period) Activity number 13: Make the right decision (pro ject, homework) Activity number 14: The newest polymer (project, homework)



Polymer classification Activity number 15: Classifying objects (project , homework) Activity number 16: Modelling a polymer (project , homework)

Evaluation activities Continuos evaluation will go on during the credit but you can also choose some of these activities for on-going assessment:

� Card game � Project: recycling poster � Fill in the blank and multiple choice test � Rational question test

Not allow more that 1/2 hour to 1 hour for on-going assessment of this unit



We begin the unit using some introductory activities and proposing some others as homework for all the students, or as a project for a group (one or two small projects should be done at the end of the 4 central units of the credit by each student)

Introductory activities These activities will introduce students to the large variety of polymers, of their massive use, and how necessary it is to study them.

Activity number 1: LET’S BURN POLYMERS!

Objective: To identify polymers by burning them

Setting the first part of this activity:

• Write these two questions on the board:

• Whole group guided activity. • To introduce the vocabulary, distribute the handout with the word search below.

• Ask how many words students can recognize and understand. • There are 24 words. • Allow 15’ for this exercise. • Correct on the board and tell students to score a point for each correct word.

KEY: Melt, smoke, stink, yogurt, flame, pan, frying,

handle, container, bottle,

burnt, polystyrene,

methacrylate, polyethylene,

PVC, leak, texture, smell,

resin, polymer, monomer,

addition, condensation, and

additive

Is there only one type of polymer?

Are polymers widely used?



H E N O I T A S N E D N O C

F A K B U R N T

R N C O N T A I N E R E M Y L O P

Y D M P O L Y E T H Y L E N E

I L S T I N K T

N E M Y O G U R T B A

G E A O E M A L F

L T D T E X T U R E P Y P

L L D T V R A

E I L C N

M A T E N O I T I D D A

K I H

V T

E P O L Y S T Y R E N E

N I S E R R E M O N O M

Handout: Polymers word search

S H A N E E N O I T A S N E D N O C

F A T E K Z D B U R N T L I M E D A

R N C C O N T A I N E R E M Y L O P

Y D O E M N P O L Y E T H Y L E N E

I L L N S T I N K E R E A D E T I O

N E U M Y O G U R T N B A L E A C G

G A E T A X T E P K O H E M A L F E

L L A T D E T E X T U R E P A Y U P

L O L I D E S R T E L E S A V R C A

M E D A I L E L A T H W G I N C A N

M C A D T O E A N O I T I D D A U D

X A E K I Z B E E N C Y A R D H S A

Q U E K V X F Z D R E T S E Y T O O

N I C E E P O L Y S T Y R E N E W R

E N I S E R N S R R E M O N O M T A



Setting the second part of this activity:

• Pairwork activity to be carried out in the laboratory or in a well ventilated class. • Provide students with a plate, a lighter, wooden test tube holders, universal pH paper and water.

• Five pieces of different types of plastic, from the different containers suggested below. • Brainstorm with the students for a couple of minutes. Ask where the different pieces of plastic come from, before students look at the grid in their books.

• Ask a student to write the suggested objects on the board. • Complete the grids bellow.

First grid1:

Object Type of Polymer

Detergent bottle

Yogurt container

Water bottle (different types)

Decoration

Frying pan handle

KEY

Object Type of Polymer

Detergent bottle Polyethylene

Yogurt container Polystyrene

Water bottle (different types) PVC

Decoration Methacrylate

Frying pan handle Resin

• Ask students to predict what will happen to the plastics when being burned. • Give words to define colour/type of flame, smell, state of the plastic, etc… Write the words on the board.

• Provide students with the handout Classifying Polymers to help them. • Give students instructions to burn each given piece of plastic, and ask them to say orally in turns, what they observe: colour of flame, smell, what happens to the plastic, etc. Guide the activity.

• Ask them to fill in the first grid in their handout. Correct on the board. • To finish with, provide the students with two other different pieces of plastic each. • Ask them to identify the major polymer by burning. Ask them to complete the second grid with their results and those of other students.

1 The students material is presented as a booklet. But, if necessary, it could be given out lesson by lesson as separate sheets.



• Allow 20 to 25 minutes for the activity. • Finally, the whole class decides the best answer to the two opening questions. This can be written on a big card and hung on the wall.

Note: This activity can be used as an initial evaluation. Handout: second grid

Object (piece) FLAME ASPECT SMELL

Polymer

Protection for fruit

Clear plastic glass (soft)

Clear plastic glass (hard)

Hamburger container

Water bottle (PET)

Water pipe

Decoration (other colour)

KEY

Object (piece) FLAME ASPECT SMELL

Polymer

Protection for fruit

Polyethylene

Clear plastic glass (soft)

Polyethylene

Clear plastic glass (hard)

Polystyrene

Hamburger container

Polystyrene

Water bottle (PET) PVC

Water pipe PVC

Decoration (other color)

Polyethylene

The following handout: Classifying polymers can be given to the students at the beginning of the activity or some copies laminated and hung on the wall.



Classifying polymers

Polyethylene

· Translucid or opaque · Flexible, semi rigid

· Can be cut, but does not break · Low density · Does not react with acids and bases · Does not react with solvents · Thermoplastic

Very stable, flexible, it can be painted: plastic bags, flexible bottles, in-sulate protections, packages

· FLAME: brilliant, yellow or blue. It melts and leaks. Wax smell

Polystyrene

· Transparent or opaque · Rigid or semirigid · It can be cut, it breaks · High density

· Does not react with acids and bases · It will react with solvents mainly · Thermoplastic

Easy to mould, cheap, breakable: boxes and non returnable containers (yogurts)

· FLAME: easy to maintain. Yellow with black smoke and unpleasant smell

PVC

· Transparent or opaque · Flexible, semi-rigid · It can be cut, does not break · High density · Does not react with acids and bases · It will react with some solvents

· Thermoplastic

Diverse aspect: pipes, window blinds, plastic curtains, water bottles

· FLAME: difficult to maintain. Yellow with almost no smoke and acid vapors



Methacrylate

· Transparent, very brilliant

· Rigid, crystalline · It breaks · High density · Does not react with polar solvents · Thermoplastic

Security crystals, decoration, optics

· FLAME: stable, it burns without smoke. It melts and leaks. Characteristic

crepitating sound. Fruity smell

Resins PF/MF · Brilliant or mat. PF is dark

· Rigid and hard · It breaks · High density · PF will react with strong acids and bases · MF will react with weak acids and bases. · Thermostable

PF: obscure (bakelite) MF: electric material dishware, telephone (melamine)

· FLAME: No flame. PF smells like burnt wood and MF like ammonia.



Activity number 2: POLYMERS FOR CONTAINERS,

POLYMERS FOR EVERYTHING

Objectives: To recognize the major polymer in everyday objects

To be aware of the diverse aspects that polymers can have

Setting the activity

• Write these two questions on the board:

• Individual work. • Complete the Polymer grid: True or False. • Ask the students to tick the correct option. • Allow for the whole activity 15 to 20 minutes.

Polymer: True or False

Tick the correct option

TRUE FALSE

Polymers are substances formed by a large number of units, monomers

A monomer is a complex structural unit There are only natural polymers All polymers are vegetal Man can modify natural polymers

Polymers are widely used due to their properties

A covalent bond joins simple structural units

KEY

TRUE FALSE

Polymers are substances formed by a large number of units, monomers x

A monomer is a complex structural unit x

There are only natural polymers x

All polymers are vegetal x

Man can modify natural polymers x

Polymers are widely used due to their properties x

A covalent bond joins simple structural units x

• Correct the exercise on the board. • Explain the polymer theory. (Teacher explanation to students is in red). • Ask students to take notes.

Does a polymeric compound have different aspects?

Can everyday objects, such as food containers, be made of different polymers?



Polymers are substances formed by a large number of simple structural units (monomers) joined by a covalent bond. In nature there are polymers such as starch, cellulose, and rubber. They have been known and used since the beginning of the world. The complete range of polymers has only been studied since the 19th; those that come from nature, those that we modify and those that man produces artificially, mainly from a sub product of crude oil. Polymers, due to a wide range of properties, are some of the most used materials in our world.

Note to the teacher: The following main activity can be done as homework or in class.

� As homework: A folder with images of different objects made of polymers will be produce by students.

• Include 8 different polymers. • For each polymer is needed: name of monomer/s, name of polymer, polymer formula, and the images of 8 different objects.

� In class:

• Pairwork. • Give each pair an envelope with the proposed laminated images, see file: images_activity 2 polymers.doc

• Ask pairs in class to classify different images / objects according to the polymer present in the highest proportion.

• Allow some time for discussion about the uses of different objects and their compositions, polymer wise.

• Ask students to write in the grid below 5 different objects, their major polymer and discuss advantages / disadvantages of its use.

Object Main polymer Advantages Disadvantages

Note: At the end of the activity, students will be aware that the same polymer can be used for different purposes and their aspect can differ in colour, texture, transparency, resistance, etc



KEY If it’s necessary: Polymers and their uses (Helping guide) can we distributed.

Object Main polymer Advantages Disadvantages

Window frames PVC durability, resistance recycling difficult

Dishwasher bottles PP resistance, price massive use

Yogurt containers PS moulding capacity recycling difficult

Medical bottles PET transparency

White foam PP resistance, protection recycling difficult

Note: It is possible that the disadvantages will be repeated or not clearly found.

Polymers and their uses (Helping guide)

Code Polymer Name Uses

Polyethylene

Terephthalate (PET

or PETE)

Soft drink bottles, salad dressing bottles,

mouth wash jars

Recycled Products: Liquid soap bottles, fibrefill

for winter coats, surfboards, paint brushes, fuzz

on tennis balls, soft drink bottles, film

High density

Polyethylene

(HDPE)

Milk, water, and juice containers, grocery

bags, toys, liquid detergent bottles

Recycled Products: Soft drink cups, flower pots,

drain pipes, signs, stadium seats, trash cans, re-

cycling bins, traffic barrier cones, toys

Polyvinyl Chloride

or Vinyl (PVC-V)

Clear food packaging, shampoo bottles

Recycled Products: Floor mats, pipes, hoses

Low density

Polyethylene

(LDPE)

Bread bags, frozen food bags, grocery bags

Recycled Products: Garbage can liners,

grocery bags, multi purpose bags

Polypropylene (PP)

Ketchup bottles, tubs, medicine bottles

Recycled Products: Videocassette storage

cases, ice scrapers, fast food trays, lawn

mower wheels, automobile battery parts

Polystyrene (PS)

Video cassette cases, compact disk jackets,

coffee cups, cutlery, cafeteria trays, grocery

store meat trays, fast-food sandwich

container, yogurt and margarine

Recycled Products: License plate holders, desk

top accessories, hanging files, food service

trays, flower pots, trash cans

and for all the other polymers.



Activity number 3: CHECKING AT HOME (homework)

Objective: To remind students of previous knowledge about polymers

Let’s introduce Gemma’s family and friend. They will help us through the unit.

Timothy, the father � Job: journalist � Work: TV3 � Hobbies: Sculpture among others

Tecla, the mother: � Job: chemist scientist � Work: Catalan Research Center � Hobbies: photography, classical music, and reading

Gemma, the daughter: � Age: 16 years old � Studies: 4t ESO in a state school in Barcelona � Hobbies: chemistry and physics, swimming and tennis, music…….

Joan, the son: � Age: 13 years old � Studies: 2n ESO in a state school in Barcelona � Hobbies: physics and art, reading, history, swimming……..

Caroline, the friend: � Age: 15 years old � Studies: 4t ESO in a public school in Sant Cugat � Hobbies: chemistry and biology, art and dance, photography, athleticism….

Homework instructions

• Give the students the handout: Home study, presentation and summary, and a little box with paper clips.

• They can work individually or in pairs. • Ask them to complete the handout and write explanations about polymers for the class. • Ask a few students to present orally what they have prepared.

Home study (at home):

Mother, why do we use so many plastic objects?

You mean polymers. There is a little difference between plastic and polymers



Mother:

Remember that it is impossible for us to get through a day without using dozen or more synthetic organic polymers. The word polymer means “many parts” (Greek poly, meaning “many”, and meros, meaning “parts”). Polymers are giant molecules with molar masses ranging from thousands to millions. Our clothes are polymers; our food is packed in polymers; our appliances and cars contain a large number of polymer components. To complete:

A ..polymer.. is a substance that will melt and flow under heat and pressure and

hence is capable of being molded into various shapes. All ..plastics.. are polymers,

but not all ..polymers.. are plastics. (Note: Use the words plastic and polymer) Mother says:

Here Gemma, take these paper clips, make a linear polymer with them and draw it. Now do the same for a cross – linked polymer.

Gemma: Does it look all right, mother? Mother: Yes, that’s good. Now, prepare the explanations for your next class. Isn’t that your homework? Your teacher said half a page, right?

LINEAR POLYMER

CROSS-LINKED POLYMER



Activity number 4: POLYMERS IN USE (homework)

Objective: To be aware of the wide use of polymers

This activity can be done as homework if students will only fill in the following grid or as one of the credit projects if the grid will be completed by more complete explanations about the polymers presented. Instructions:

• Give the students the following grid and explain, if needed, how to search and handle information in the Internet.

• Explain advanced image search, and how to decide about key words for the search.

• Ask them to save images in jpg and open them with a image/paint program and save them in a reasonable size.

• Explain how to insert in the image the internet URL where it comes from. • Ask students to fill in the grid with different objects and their major polymer, classified by fields.

• Students have to add some comments (about half a page) about the uses of polymers in one of the proposed fields.

Agriculture Medicine Transport Industry Construction Housing Clouding Packaging Sports



Polymer synthesis After introducing the polymers and theirs uses, let’s begin their chemical study. Polymers are divided according to their chemical synthesis into: Addition synthesis Condensation synthesis

• Allow 10 to 15’ for the initial explanation about addition polymerization and condensation polymerization and activity number 5.

• Remember teacher’s explanation in red.

Synthetic polymers can be classified as addition polymers, made by monomers units directly joined together. Others are condensation polymers, made by two different monomer units that join ……… A – B – A – B …….., generally losing a small water molecule to form the polymer.

Activity number 5: BASIC IDEAS ABOUT POLYMERS

Objective: To summarize knowledge about polymers

• Dictate the following sentences to the students. • Ask them to complete them. One student can write them on the board.

1.- Polymers are made of ............................

2.- Some synthetic polymers are: ..............................................

3.- Name some natural polymers: .................................

4.- Addition polymers are usually made of equal .................

5.- When two molecules join with loss of water, this is called ................ polymerization.

POLYMERIZATION Identify the addition reaction and the condensation reaction ......................... reaction .................................. reaction



• The information below will be distributed to the students, read and explained by the teacher.

• Allow 20 minutes to do it and answer students’ questions. • To complete the activity you can ask the students to write a short article, as a homework.

• It will contain images and the following information.

Addition Polymerization

Let me explain it to you: Polyethylene is the simplest example of an addition polymer, chain-reaction polymerization. In the process, the unsaturated hydrocarbon monomer, ethylene, changes into a long chain saturated hydrocarbon polymer, polyethylene. Linear chains of polyethylene can be long and closely packed: high-density polyethylene (HDPE), a polymer with high density and high molar mass, is hard, tough, and with certain rigidity. Plastic bottles, like milk and soap bottles, are examples of uses of HDPE

If during the polymerization we allow some lateral chains to grow, instead of a linear chain polyethylene, we end up with a branched chain of polyethylene. Branched chains of polyethylene cannot get too close together and the low-density polyethylene (LDPE), is lower in density, soft and flexible, ideal for plastic bags and some plastic films.

Gemma, Joan, pay attention

A monomer molecule in addition polymers contains one or more double bonds. Take ethylene, the first alkene CH2=CH2. Heated to 100 to 250ºC at 1000 to 3000 atm with a catalyst, polyethylene is formed.

C = C

H

H H

H

C - C

H H

H H

n

Mother is polyethylene the only polymer we use? And, what do we use it for?

Is polyethylene always the same?



Table of addition polymers

Mother: Summarizing: different monomers, differences in length, branching, and cross-linking produce different polymers with special properties for each addition polymer. Chemists try to find the right polymer with the desired properties by linking monomers through chemical polymerization.

I’ll look at the table of addition polymers that the teacher gave us and try to find some objects made of these polymers



Many of the addition polymers are copolymers. That means polymers obtained by the polymerization two or more monomers. Styrene with butadiene is the most important synthetic rubber produced.

Activity number 6: CONCEPTS CONSOLIDATION Note: The following activity could be used as a regular evaluation activity. Handout: POLYMERS

Complete the sentences

Hi boys, go to your father for checking

Gemma, Joan, Have you finished with the unit? Are you prepared for a short test?

1.- The individual molecules from which polymers are made are called ....................

2.- Monomers must have a ..................................... bond in their structure if they are to participate in an addition reaction.

3.- The double bond in ethylene is converted to a .................................. bond during an addition reaction.

4.- PVC is polyvinyl chloride. It is built from the monomer............................

5.- Stereoregulation catalysts are used to prepare synthetic ........................

6.- Two different types of polyethylene are LDPE and HDPE

a) LDPE stands for..........................

b) HDPE stands for.........................

7.- Thermoplastic polymers can be affected by .................................. and permit to .............................. them.

8.- Thermostable polymers cannot .................. at high temperature, thus they will be used in ............................ accessories.

9.- Copolymers are obtained by .......................................................................................

10.- Addition polymerization usually needs high ..................... and ......................, and the presence of a catalyst.



� Allow 20 to 25 minutes to answer if done in class or give the students the

handout to be answer at home. � To complete this exercise

• Work in threes: one student will be the father and the others, Gemma and Joan. • Students will use the handout POLYMERS. • “The father” can reformulate the sentences into questions. • “Gemma and Joan” will answer “the father’s” questions. • Ask the group to evaluate their use of English during the activity (1 to 10 max.)

Note: If you expect some difficulties, the activity could be held in the ICT class, so the students can look for some information on the Internet.

Notes for the teacher: Polymer Addition Addition polymerization is a three step process. Monomers, always a compound with at least one carbon-carbon double bond, add one to one with the help of another substance: the catalyst. Ethylene is the first example of a monomer. Their addition polymer, polyethylene, has a wide range of uses. The catalyst can be peroxide, in low concentration, that provides a free-radical: a chemical component that contains a free electron, as a result of the break of the covalent bond leaving one electron in each part of the molecule (free – radicals are extremely reactive).

The production of free –radical form peroxide gives the possibility to initiate the polymerization process 1.- Initiation (first step) Initiation of addition polymerization process occurs when the free-radical catalyst reacts with a double bonded carbon monomer, and that initiates the polymer chain. The double carbon bond opens in order to transfer one of its electrons to the free – radical, and that leaves the other electron of the double bond to the carbon that will act as a free – radical and follow the reaction.

2.- Propagation (second step) During the propagation process a repetitive reaction takes place. The propagating polymer chain, which is a free – radical, interacts with another molecule of monomer opening its double bond. The free electron is moving, at every addition, to the final carbon of the polymer growing chain.



This is a continuous reaction because the energy of the polymer is, itself, lower than the energy of all the monomers. So, the reaction is exothermic. 3,- Termination (third step) In order to stop the reaction two free –radical have to react together. See the reaction proposed below

In these two possibilities you can see the reaction of a peroxide radical with a polymeric growing chain (also free –radical) or between two complete polymeric growing chains. The addition polymerization is an exothermic reaction that takes place at high velocity and during the reaction, depending on reaction conditions, cross-links with other chains can occur.



Activity number 7: METHYL ACRYLATE, THE MONOMER. POLYMETHYLACRYLATE, THE POLYMER

Objectives: To introduce laboratory work and language

To analyze chemicals used and be aware of their potential danger

To consolidate knowledge about addition polymerization

Setting the activity

• Write these two questions on the board.

• This activity should be performed in the laboratory • First review polymer addition

Addition polymerization is a three step process. Monomers, always a compound with at least one carbon-carbon double bond, get added one to one with the help of another substance: the catalyst, which acts as an initiator 1.- Initiation by the catalyst (first step)

2.- Propagation to enlarge the polymeric chain (second step)

The energy liberated during the polymerization helps the reaction to continue

Does a polymer come from only one monomer in addition polymerization?

What is the role of an initiator in addition polymerization?



3,- Termination to end the polymerization process (third step) We need to trap the free radical to stop the reaction

Safety notes This can be performed as a demonstration under a laboratory hood and using protective gloves or done by different groups of students under the supervision of the teacher. The monomer, Methyl acrylate, has an acrid odour and irritates eyes, skin, and mucous membranes; it is a lachrymator. Do not inhale the vapour. Both methyl acrylate and acetone are extremely flammable; perform the experiment away from flames or any source of heat.

• Pairwork. • Remaind students to work carefully under the laboratory, to pay atten-tion to the teacher and to read all the information related to the chemicals used.

• If you want students to perform the experiment hand out the material for the groups near the laboratory hood.

• Distribute the spaces under the hood by sections where each group will allow their polymerization to take place.

• See a proposal in the picture below.



Interpretation of the picture: As shown in the picture, we suggestthe students work in the two front tables and leave the last one for multiple uses. In this activity we will see in red the materials needed for 5 groups of 3 three students; group number one at the end of the arrow and group number five at the beginning of it. The yellow circle is the teacher supervision point.

� Students, carrying their material, will arrive to the hood following the dark blue arrow. Under the hood, supervised by the teacher, they will add the reactants, and leave the hood following the cyan arrow.

� The preparations will be left in the hood as the green dots show. In this way, students can come back and find their preparation easily.

� To clean the polymer, the water sink is besides the hood. � On the teacher table students will find the chemicals use such as 5 mol�dm-3

NaCl solution and acetone (CH3COCH3), and a 2 mL pipette with sucker to measure the products.

� On each working place students will find a 100 mL graduated cylinder and dropper, and 100 mL and 250 mL beakers.

� Under the hood students will find: � methyl acrylate solution, 0.6 mol�dm-3 (5%), with a 100 mL graduate

cylinder and dropper � potassium bromate, 0.1 mol�dm-3, with a 1 mL pipette and sucker � sodium hydrogen sulfite solution, 0.45 mol�dm-3, with a 1 mL pipette and sucker

� All the process will take around 35 minutes, leaving the rest for the teacher to explain and to complete the written work.



3. Two students from each group will take the Erlenmeyer flask to the hood and under the supervision of the teacher they will add

� 60 ml of 5% methyl acrylate in the 250ml Erlenmeyer flask � 1 ml of 0.1 M potassium bromate solution and � 1 ml of 0.45 M sodium hydrogen sulfite solution

Swirl the flask to mix the contents thoroughly Place under the hood and leave

The third one will take care of the rest of the material 4. During the following 12 minutes allow the reaction to continue, shaking the

flask occasionally. The mixture turns milky. At this stage, only one person will be working at the hood each time.

5. After the 12 minutes one student in each group measures 60 mL of solution chloride and pours it into the 250 mL beaker and goes to the hood.

6. There the student pours the emulsion with the polymer into the beaker with the sodium chloride solution to allow to coagulate

7. Remove the polymer, solid mass, with tweezers and wash it clean of unreacted products under water. Repeat as many times as necessary.

8. Cut the polymer mass into pieces and dissolve it in acetone (about 1 g/10 ml) in the 100 mL beaker.

9. Stir the mixture to obtain a thick and viscous liquid. 10. Pour this liquid onto the Petri plate covered with polyethylene film and allow

it to dry for several hours. The polyacrlate film can be finally peeled off the polyethylene surface

What to observe

Change of temperature

Change of visual aspect

Velocity of this change

Change of aspect as NaCl is added

Physical characteristics of the product

Solubility in acetone



Key

Type of reaction After the temperature increase �� exothermic reaction

Polymerization After the change of aspect and milky appearance �� new product shape, insoluble in water

Since the main reactive was methylacrylate �� product should be polymethylacrylate

Reaction kinetics Milky appearance occurs fast �� high reaction rate

Terminate the reaction Since NaCl is needed to stop the reaction �� a secondary reaction could be needed to terminate the polymerization

What to conclude?

Type of reaction

Polymerization

Reaction kinetics

Terminate the reaction

Polymer uses

Type of bounding



Polymer uses Form a film �� Its capacity to form films makes it useful to cover surfaces. Paints and coatings are used in a variety of industrial applications: wood, automovile and fabric, and in lacquers and inks.

Polymethyl methacrylate may be use in a variety of ways, due to its resistance and transparency. It is used instead of glass, in laboratory instruments, and cameras.

Type of bounding Polymethylacrylate shows to be insoluble in water (milky appearance) and soluble in acetone �� covalent bounding

Notes for the teacher: Scientific Principles The polymerization reaction can be represented as:

Polymethylacrylate polymer is produce from the monomer, methylacrylate, with a radical generator as catalyst. Water is the solvent for the catalyst and is also used, as well, as moderator in fast exothermic reaction. Bromate ions and hydrogen sulfite ions react to produce hydroxyl radicals (OH.) and hydrogen bisulfite radicals (HSO3

.) that initiate the polymerization process. Sodium chloride solution is used to coagulate the polymer, and acetone can be used to dissolve the polymer and to produce the final film.

Ready to polymerize There are some ready to polymerize products in the market: � Discount stores: squirt string from aerosol can (polystyrene) � Hardware stores: aerosol foam insulation (polyurethane)



Condensation Polymerization

• Explain polymer condensation. • Ask students to take notes. Some information on the wall, like formulas and names of condensation polymers, can be of help.

• Allow 15 minutes for explanations.

Condensation polymerization is a chemical reaction in which two molecules react by eliminating a small molecule. The reaction of alcohols with carboxylic acids to give esters is an example of condensation, called esterification.

This important type of chemical reaction does not depend on the presence of a double bond in the reacting molecules. It rather requires the presence of two different kinds of functional groups on two different molecules. If each reacting molecule has two functional groups, both of which can react, it is possible through condensation reactions to produce long-chain polymers. Some examples of condensation polymers are: a) Polyesters

Polymerization of two monomers: a dicarboxylic acid (example terephthalic acid) and a dialcohol (example ethylene glycol) allows condensation polymerization through the esterification at both ends.

A large number of molecules of acid and of alcohol can react to produce a large polymer molecule, known as polyester.

CH3 – C

O

OH

+ CH3 –CH2OH CH3 – C – O – CH2 – CH3 + H2O

O



One example is Dacron, nontoxic, nonallergenic, noninflammatory polyester used as a substitute for human blood vessels in heart bypass operations (Dacron tubs) and as a skin substitute for burn victims (Dacron sheets). b) Polyamides (Nylons) Amines can be considered derivatives of ammonia, and most of them are weak bases, similar in strength to ammonia. An amine reacts with a carboxylic acid to split up a water molecule and form an amide.

A condensation reaction between a dicarboxylic acid and a primary diamine, produces polyamides, one of the best known is Nylon. Polyamides have had, and still have a great impact on our lives.

Polyamides can easily be extruded into fibers, stronger than natural fibers and chemically more inert. Natural fibers were not suitable for the demanding society of the 20th-century, because � Silk was not durable and very expensive � Wool is scratchy � Linen crushes easily and gives too much work � Cotton looks like an old-fashioned material This means that all four haved to be pressed after cleaning which is too much housework for a modern society. What’s more, polyamides came onto the stage. The hydrogen bonding explains the properties of nylon fibers: good tensile strength. The polymeric chains attract each other due to the hydrogen bounding, strong enough but not so strong that it doesn’t allow the polymer to form fibers. Nylon initiates a new era in the textile industries.



c) Polycarbonates The tough, clear polycarbonates can substitute glass due to their resistance and capacity to transmit visible light. The name polycarbonate comes from the linkage’s similarity to CO3

2-, the inorganic carbonate ion, as the repeating unit of polycarbonates

Polycarbonate is a very durable, resistant material, but can be attacked by some acids and a large number of organic solvents. Polycarbonate with characteristics like those of polymethyl methacrylate (PMMA) is the polymer that is chosen for glass windows, security glasses and eyeglass lenses.

Notes for the teacher: Polymer Condensation Condensation Polymerization can be called Step-Reaction Polymerization It produces polymers of lower molecular weight than chain reactions and needs higher temperature. From the different Nylon products, we take Nylon 6,6 as an example because of its massive use in clothing. The condensation of two monomers: hexamethylene diamine and adipic acid, form the dimer of Nylon 66.

The name of Nylon 6,6 comes from the two-monomer chains of six carbons atoms: hexamethylene diamine and adipic acid. The Nylon 6,6 dimer can grow on either sides, theoretically until no monomer or dimer is available. This process, relatively slow, avoids cross-linking chains unless a tri-functional monomer is added.



Some condensation polymers are:

Polyester clothing (dacron)

O ||

- C - O -

Polyamide

nylons

H O | ||

- N - C -

Polyurethane

foams

O H || |

- O - C - N -

Polyurea

foams

H O H | || |

- N - C - N -

Polyanhydride

not widely used

O O || ||

- C - O - C -

Polysilicone

silicones, heat exchange fluids

R |

- Si - O - | R

Some internet pages and sites to help you: � medical dacron applications http://www.fibrogen.com/collagen/uses.html http://arjournals.annualreviews.org/doi/full/10.1146/annurev.bioeng.3.1.225 � history of nylon http://www.cha4mot.com/e_lc_nyl.html � polycarbonates http://www.bpf.co.uk/bpfindustry/plastics_materials_Polycarbonate_PC.cfm And you will find some interesting information on http://en.wikipedia.org



Activity number 8: FIRST REPORT

Assess new knowledge

• Write these questions on the board.

• Explain how to summarize information and ask good questions:

• recall and knowledge questions (to remember previous information) • comprehension questions (to express the main ideas of the new knowledge), and

• application and analysis questions (to apply new knowledge to a everyday or hypothetic situation).

(See scaffolding materials)

• Stick charts on the wall, with explanations of how to summarize and about different types of questions.

• Pairwork. • Ask one or two students out of the whole group to make sure English is used during the astivity.

• Give each student the following hand out to fill in the blanks. • Correct it on the board and ask students to produce a summary containing the main ideas.

• Allow 5 minutes to fill in the blanks, and 10 minutes to correct and discus the summary.

� As homework, students will write a half page summary and write two recall

questions, two comprehension questions and two application / analysis questions about their own text.

Handout: Fill in the blanks

1.- Nylon is an example of a ............................ polymer.

2.- Polyesters are formed by a ...................... reaction, called ..........................

3.- A molecule with ............................ groups, and another molecule with two

alcohol groups, can react with each other at ...................... ends.

What is a polymerization reaction?

Can you differentiate addition polymerization from condensation

polymerization?

Can you give some examples of different polymers and their use?



4.- The reaction of terephthalic acid with ............................ gives a

........................... with the elimination of ............................

5.- Dacron is an excellent substitute for ............................ in heart bypass

operations, and Dacron sheets are used as a ........................... in ulcers and burn

victims.

6.- Amines can be considered derivatives of .......................... and they are

..........................., similar to ammonia in strength.

7.- One well known polyamide, ..........................., has set the introduction of a new

era in the .......................... industry.

8.- The name polycarbonate comes from the linkage’s similarity to an

.......................... ion, with the formula ...........................

9.- Polycarbonates are tough, .......................... and can substitute glass due to

their capacity to .......................................

10.- The .......................... bonding explains why nylons make such good fibers. If

the chains are linked together with .......................... bonds, the strength of the

linkage does not allow nylon to stretch.

KEY

1.- Nylon is an example of a ...condensation ..polymer.

2.- Polyesters are formed by a ..condensation… reaction, called …esterification. 3.- A molecule with … two acid ….. groups, and another molecule with two alcohol

groups, can react with each other at …. both... ends.

4.- The reaction of terephthalic acid with .. ethylene glycol.. gives a

...polyamide... with the elimination of ..a water molecule....

5.- Dacron is an excellent substitute for ...blood vessels.... in heart bypass

operations, and Dacron sheets are used as a ...skin substitute ... in ulcers and burn

victims.



6.- Amines can be considered derivatives of ...ammonia…. and they are ..bases...,

similar to ammonia in strength.

7.- One well know polyamide, … nylon 6,6….., has introduce a new era in the …..

textile…. industry.

8.- The name polycarbonate comes from the linkage’s similarity to an

...inorganic...... ion, with the formula .... CO32-......

9.- Polycarbonates are tough, ……clear….. and can substitute glass due to their

capacity to …….transmit visible light…...

10.- The ....hydrogen... bonding explains why nylons make such good fibers. If the

chains are linked together with ...covalent..... bonds, the strength of the linkage

does not allow nylon to stretch.

Note: You may evaluate the activity and hang the results on the wall.



Activity number 9: TO STRETCH IS WONDERFUL (fourth period)

Objectives: Evaluate the potential of the properties of synthetic fibres

Differentiate addition polymerization from condensation polymerization

• Hang the following piece of news on the wall. • Read the information of the social event, which allows every woman to wear clear stockings to show off perfect legs.

• Allow 5’ to discuss.



Notes for the teacher: Review polymer condensation Condensation polymerization

Remember that condensation polymerization is a chemical reaction between two molecules that react by eliminating a small molecule. Instead of the presence of a double bond in the molecule, difunctional substances with matching groups at the end are needed. As an example see esterification.

Diamines can react with diacids or diacid chlorides to produce a condensation polymere; these polymers have the generic name of nylon. Nylon, polyamides are named by a numeric system that indicates the number of carbon atoms in its precursors. The first represents diamine and the second dicarboxylic acid: nylon 6,6 monomer are an hexamethylenediamine (first) and 1,6-hexanedioic acid (adipic acid) (second) The equation in this experiment is:

Safety notes: This can be performed as the addition polymerization by different groups of students. They can work as in activity number 7 or every group in their working place due to the small quantities used. Hexamethylenediamine and adipoyl chloride (caustic) are irritating to the skin, eyes, and respiratory system and sodium hydroxide is extremely caustic. The solvent, hexane is extremely flammable.

• Work in pairs or groups of three. • Work carefully in the laboratory, pay attention to the teacher and read all the information related to the chemicals that are being used.

• Remember the possibility to work as the schema in activity number 7.

• Place one 100 mL beacker (tall and thin) and a 10

CH3 – C

O

OH

+ CH3 –CH2OH CH3 – C – O – CH2 – CH3 + H2O

O



mL graduated cylinder, paper clip and stirring rod in each group working place. • Ask students to read the experiment text. • Teacher will be in control of chemical products:

• 1,6-hexanediamina, 5% solution and 10 ml graduated cylinder and dropper. • sodium hydroxide, 20% solution and dropper • adipoyl chloride, 5% solution in hexane and dropper

• At the beginning, after a brief explanation by the teacher, one student from each group will go to the teacher’s table with a 100 mL beaker and pour into it 10 mL 1,6-hexanediamina. They return to the working place.

• Sodium hydroxide, 20% solution, and a dropper will then pass around. Students will help to add 10 drops to the reactive, pass it to the next group, and stir their solution.

• Next, the adipoyl chloride, 5% solution in hexane with another dropper, will do the same circuit to add to the second monomer.

• Remind students not to disturb the interphase. • Allow 35’ to do this experiment and finish it completely. Write a report.

Objective Obtain a condensation polymer from its monomers

Observe nylon proprieties

Materials and supplies: � 10 ml of 1,6-hexanediamina, 5% solution (water soluble) � 10 drops of sodium hydroxide, 20% solution � 10 mL of adipoyl chloride, 5% solution in hexane � 10 mL graduated cylinders and droppers. 100 mL beaker � 1 paper metallic clip and glass stirring rod

Procedure: 1. Wearing gloves, place 10 mL of 1,6-hexanediamina, 5% solution, in a 100mL

or smaller beaker. 2. Add 10 drops of sodium hydroxide, 20% solution, and mix. 3. Slowly add 10 mL of adipoyl chloride (it can be used instead of adipic acid),

5% solution in hexane, to the first solution. Take care, both solutions should stay separate, and you should see two layers.

4. Open a paper clip and with one end catch a little bit of the substance formed between the two layers.

5. Pull it up and roll up around a glass stick as shown in the picture. 6. Look at the schema and write on it:

a) What is in each part, up and down?

b) Where does the reaction take place?

c) What is the name of the substance produced?

7. Clean the substance you have obtained with enough water. Try to unroll and dry it with a paper towel.

8. Observe and write the name and the properties of our new product. 9. Finally with the glass stick mix the substances in the beaker and write down

your observations.



What to observe

Change of temperature

Change of visual aspect

Velocity of this change

Layers

Where the reaction takes place

Physical characteristics of the product: stretch, strength

What to conclude

Type of reaction

Polymerization

Reaction kinetics

Products solubility Possible bonds

Affection to kinetics

Polymer uses



Key

Type of reaction After the temperature increase �� exothermic reaction

Polymerization After the change of aspect; film in the interphase �� new product form, insoluble, nor in hexane

Since the monomers are a diamine and a dichloride �� product should be a polyamide (condensation polymer)

Reaction kinetics Film in the interphase appears very fast �� high reaction rate

Products solubility Possible bonds

Diamine is water soluble �� polar covalent bond.

Adipoyl chloride needs to be dissolved in hexane (organic solvent) �� apolar covalent bond.

Nylon 6,6 insoluble in both solvents �� polymeric substance

Affection to kinetics Since nylon is formed in the interphase �� for products to react, they have to be in contact. Importance of the rate of division and to work with solutions

Polymer uses As textile fibre �� its capacity to stretch makes it useful as synthetic fibre to substitute silk

Due to its strength �� wiedely used in ropes and in construction, industry, etc ……



Notes for the teacher: Scientific Principles Using a diamine and a diacid chloride to produce nylon, some catalyst is needed or NaOH has to be added to produce some adipic acid. The reaction mechanism can be summarized thus:

And finally the dimmer



Dimmers can grow by incorporating other molecules in both ends, or even incorporating another dimmer. The result is the process of nylon production by condensation polymerization.

Easy to stretch There are some possibilities for a follow up: � Give students the Internet URL to learn about the origin of the name NYLON and to think about the urban myth. http://www.snopes.com/business/names/nylon.htm � You can suggest your students to help carry out a short investigation about the stretching capacity of nylon, by buying a cheap pair of stockings and stretching them as much as possible. They can work in a qualitative or quantitative way.

Chemical structure and physical properties of polym ers

• Teacher explains chemical structure and physical properties of polymers. • Allow 20 minutes for explanations • Students take notes. • Chemical structure of the polymers will refer to the arrangement of the monomers in the polymer.

Chemical structure

Homopolymers are formed by only one type of monomer, and Copolymers are formed by the union of more than one type of monomer (condensation polymers are always copolymers) The copolymer can lead to different configurations depending on the relative situation of the monomer: random (aabbabbbaaba), alternating (ababababab) (nylon is an example) bloc (aaaaaabbbbbb) or graft (bbbbbbbbbbbbbb) a a a a But monomers can join forming linear chains, branched or cross-linked ones: Linear polymers � continuous long chain polymer Branched polymers � continuous long chain polymer with small branched chains hanging from it Cross-linking polymers � bond are formed in between continuous chains polymers (Vulcanization is an example of cross-linking polymerization. Bonds between the chains give strength to an elastomer)



Physical properties of polymers

Molecular weight increases Melting or softening temperature rises

Molecular shape more coils Elastic properties increases

Chains structure more crosslink / network

Strength / thermal stability rises

Elasticity (stress-strain) � The capacity of being deformed, and eventually fracture, with an increasing tension load that is applied along the long axis of a specimen. In elastomers, elongation capacity is related to helical or zigzag chain, acting as a spring. Fracture � The polymers resistance to fracture is higher that those of metals and ceramics. Fracture effect increases with thickness and affects the covalent network and cross-linked bonds. Hardness � Polymer hardness is evaluated as resistance to localized plastic deformation through penetration techniques. Polymer crystalline structure Due to its size and complexity most of the solid polymers have both crystalline regions and amorphous ones. Amorphous regions are zones with great disordered chains. The degree of crystalline structure in a polymer depends on the rate of cooling during solidification that allows the chain to grow. Branched and cross-linked polymers tend to have more amorphous regions.



Activity number 10: PAPER CLIPS TO MODEL

Objectives: To model addition polymers and condensation polymers

To visualise crystalline and amorphous structure

To analyse different properties

• Pairwork. Allow 15 minutes. • Hang these two images as laminated cards on the wall.

• Remind students about addition polymerization and condensation polymerization, homopolymers and copolymers; and crystalline and amorphous structure.

• Distribute boxes with different colour paperclips and explain that they will be used as models of monomers.

• Explain that some clips can be chained together easily, but for some others to take out first the two pieces of paper is needed. Some are simple and some have a little object join at them.

• Ask them to decide which are suitable to model addition polymerization, and which condensation polymerization, and which will be monomers of branched polymers.

• Distribute the grid bellow. • Ask them:

� to model three addition polymers: a) a single chain polymer, b) a branched polymer, c) a cross-linked polymer, and also d) a condensation polymer.

� to draw the models on the grid or glue a photo of it. • Now, one student will explain to their partner about the characteristic of each type of polymer.

• Finally, ask them to model, using linear polymers, an amorphous region and a crystalline one, and discuss the characteristics of the two polymer structures.



Grid II: Modelling polymers According to the images decide which colour and size of paper clips will be used to model different monomers

Addition polymers with

Condensation polymers with

Branched addition polymers with Key

Addition polymers with c e f

Condensation polymers with a b d

Branched addition polymers with e f

• Ask the students to write the answer to the following questions: 1) Explain the difference between linear, branched and cross-linking polymers. 2) Relate elasticity, hardness and fracture to the chemical structure of a

polymer. 3) Explain the dependence of the degree of crystalline structure in a polymer on

the cooling rate. Key

• Ask the students to write the answer to the following questions: 1) Explain the difference between linear, branched and cross-linking polymers. Linear polymers � continuous long chain polymer Branched polymers � continuous long chain polymer with small branched chains hanging from it Cross-linking polymers � bond are formed in between continuous chains polymers 2) Relate elasticity, hardness and fracture to the chemical structure of a polymer. In elastomers, elasticity is related to helicoidal or zigzag chain. Helicoidal chains increase elasticity. Fracture effect increases with material thickness. Hardness increases as covalent and cross-linked bonds are formed, but on the other hand fracture effect increases too, and elasticity decreases. 3) Explain the dependence of the degree of crystalline structure in a polymer on

the cooling rate. As the cooling velocity decreases it gives enough time for the polymer to order its chains.



Grid II: Modelling polymers Draw the polymers propose on the grid below

Linear polymer Branched polymer

Cross-linked polymer Condensation polymer

Polymer structure: amorphous crystalline zones



Finally they perform a conversation between the two friends to allow them to fill in the next grid relating the physical proprieties of a polymer to their chemical structure.

How to predict the strength and flexibility of polymers

Molecular weight …………… Melting or softening temperature rises

Molecular shape …………… Elastic properties increase

Chains structure …………… Strength / thermal stability rises

Chain structure …………… Fracture rises

Chain structure …………… Flexibility/fluidity decreases

Key

Molecular weight increases Melting or softening temperature rises

Molecular shape more coils Elastic properties increase

Chains structure more crosslink / network

Strength / thermal stability rises

Chain structure more crosslink Fracture rises

Chain structure more crosslink Flexibility/fluidity decreases

Hi, Gemma. Can you explain to me the relationship between the softness of a polymer and its structure?

Sure, Carolina I have to fill in this grid. Let’s do this exercise together



Activity number 11: PHYSICAL PROPERTIES

To analyse the effect of the oriented chains in linear polymers

both in strength and their behaviour to light

• Hang the image below on the wall.

• Explain to the students the three points, represented in the light blue balls, to consider in order to produce a polymer for a certain use:

• Ask them about the meaning: • central situation of Base Polymers: polyolefins, polyesters • situation of LUBUTENE ® • situation of OPTIMIDE ® • what can be the use of LUBOTENE ® and OPTIMIDE ®

Key

Optatech Corporation (http://www.optatech.fi/default.asp) strategy is to focus on adding valuable properties to the two most versatile base polymer families: polyolefins and polyesters.



Polyolefins and polyesters are the base versatile polymers that this company uses to modify them in order the achieve some interesting properties. LUBOTENE ® and OPTIMIDE ® are two registered trade marks of polymers. LUBOTENE is useful due to its functionality as adhesive and OPTIMIDE due its mechanical and chemical resistance, as you can see due to its situation in the previous figure

• Pair Work. Allow 10 minutes. (Note: this activity can be performed as a demonstration with the overhead projector)

Objective

To observe the relationship between the strength of the polymer and the

chain orientation

To visualize the relationship with polymeric chains and optical properties

Materials and supplies:

� newspaper, cellophane tape, plastic film, plastic bags � iridescent plastic film � polarizing lenses, and flashlight

Procedure 1. Take a sheet of newspaper and tear it, first longways and after widthways. Observe the torn border. In which case it is more regular?

2. Polymers always break easily in the direction of the chain. Decide which is the direction of the natural polymer cellulose in the newspaper.

3. Do the same with a piece of cellophane tape, to know the direction of the polymer chain.

4. Use an inexpensive 1 layer plastic bag. Try to penetrate the bag, with a pointed instrument, and tear it, first longways and after widthways.

5. Write your comments in the grid below.

6. Look at the flash light through one polarizing lens. Use the second polarising lens, crossed (90 degrees to the other), to see that no light is coming through.

7. Now use pieces of plastic to show that they will rotate the polarized light due to the presence of the polymer chains.

8. Place diverse strips of cellophane tape crossed randomly over of overhead transparency. See the colour appear as they will rotate: polarised light.



Key

TEAR

Along the chain direction Across the chain direction

Newspaper

Cellulose fibres in the newspaper are not held together through a chemical reaction. Instead of that, paper sheets are the result of pressing the natural fibres, oriented in the same direction, together to expel the excess of water.

If you tear a newspaper perpendicularly to the printed letters, the border is clean and straight; you tear following the fibre direction.

Otherwise, if you tear it across, the cut looks more random; you are working against the fibre direction.

Cellophane tape

Observe that cellophane tape tears smoothly and easily, widthways.

And it is very difficult and usually a sharp instrument is needed to tear across the chains

Plastic bag

Along the polymeric chains it is easy to tear and the bag will rip without difficulty.

Across the chains it is more difficult to rip it.

TEAR

Along the chain direction Across the chain direction

Newspaper

Cellophane tape

Plastic bag



A step to the future It is interesting to spare some time to introduce the history of polymers. Students need to realize that polymers have always been in nature and that chemical research is carried out to improve material properties for a wide range of uses. Moreover, chemistry teachers had to make sure that their students are aware that chemistry improvements are not only due to good luck. Introducing polymer historical facts

• Allow 15 minutes for the initial explanation. • Hang the recommended timeline about polymer history on the wall. • Show the Power Point: Polymer_History.ppt • Introduce your own comments.

Polymer timeline

1000 BC Lacquer work in China

800 Records from a tree natural resin Gutta percha (Malayan)

1550 Valdes describes First reference to natural rubber: Valdes expeditions to Central America

1731 Charles Marie de la Condamine reports the use of rubber in the Amazon

1839 Charles Goodyear (USA) discovers 'vulcanisation'.

1863 Phelan and Collander, a billiard ball manufacturer, offers prize of $10,000 to find a substitute for ivory in billiard balls

1869 Hyatt brothers (USA) develop 'Celluloid'

1880 Shellac (Germany) used to produce phonograph

1884 Louis Bernigaud discover Rayon

1903 Stern and Charles Topham develop production of viscose (artificial silk).

1905 J. Edwin Brandenberger invents 'Cellophane'.

1909 Leo Baekeland (USA) patents Bakelite (thermoset)

1910 Herbert Faber and Daniel O'Conor (USA) first produced 'Formica'

1922 Hermann Staudinger (Germany) synthesizes rubber.

1926 PVC is discover Hermann Staudinger (Germany) starts its works on 'macromolecules'

1929 Dunlop Rubber Co. (Britain) produces the first foam rubber.

1930 BASF / I.G.Farben (Germany) develops polystyrene and Dow Chemical Co. (USA) polystyrene.

1931 Carothers develops Neoprene. Imperial Chemical Industries - ICI (Britain) develops polyethylene.

1933 ICI workers (R.Hill and J.W.C. Crawford) start synthesis of poly(methyl methacrylate) or PMMA

1934 Wallace Hume Carothers at Du Pont (USA) develops nylon

1938 Roy Plunkett (Du Pont) accidentally discovers PTFE (polytetrafluoroethylene).

1941 I.G.Farbenindustrie (Germany) starts polyurethanes production Announcement of first commercial PET polymer



1942 'Super Glue' (methyl cyanoacrylate) discovered by Dr Harry Coover (Kodak)

1949 'Lycra' is invented by Joe Shivers (DuPont).

1952 PVC appear - replacing shellacs and phenolic polymers in records.

1953 First production of high density polyethylene (Du Pont).

Karl Ziegler (Germany) and Giulio Natta (Italy) develop metal ion catalysts for regular polymerization Hermann Staudinger wins Nobel Prize for Chemistry for the study of polymers. Herman Schnell at Bayer first synthesizes polycarbonate

1963 Ziegler and Natta share Nobel Prize for Chemistry for the synthesis of

polymers.

1974 Oil crisis: 300% increase in price of crude oil prices increase.

1983 ICI and Bayer launch PEEK, PES and PPS (thermoplastics)

1990 Warner Lambert develops Novon and ICI launches Biopol (bio-degradeable plastics)

2000 New polymers emphasis is now on composites to improve polymer properties. Summarizing, we can use the image of the polymer timeline proposed by The American Plastics Council

Activity number 12: EXPLAINING THE HISTORY OF POLYM ERS

Objectives: To realise the importance of polymers in our world

To know some of the greatest steps in chemical synthesis

Project instructions:

• Ask the students to make a Power Point presentation about some important fact or a relevant scientist in the history of polymers. Propose some:

• One polymer, natural or man made: Natural Rubber, Shellac, Polystyrene, Cellulose Nitrate or Celluloid, Polytetrafluoroethylene or Teflon, Nylon, Neoprene, or Saran Wrap

• Or one of the scientists that has worked on polymers: Leo Hendrick Baekeland, Wallace Hume Carothers, Charles Goodyear, John Wesley Hyatt, Giulio Natta, Hermann Staudinger, or Karl Ziegler.

• Work in threes. Do not allow two groups with the same topic. • Power Point presentation: between 12 al 16 slides, images, schema, chemical clues, and short text.

• Explain there is necessity of uniform stile for the whole presentation. • Remind them how to search the net: advanced search (web and images) • Give them one week for the project.



Recommended points for Polymer history presentation

Project Evaluation Student 1 Student 2 Student 3

No more that 16 slides 1 point

Title name and

introduction 1 point

Uniform clear style 1 point

Reference and

bibliography 1 point

Chose of representative

facts 2 points

Relevancy of images 2 points

Personal explanations 2 points

Student own proposed

park (orientative)

Increase of 10 % due to

global evaluation

max. 1 point

Final mark (maximum) 11 points

Activity number 13: MAKE THE RIGHT DECISION

Objectives: To design some research to be done at home

To decide the most sustainable option, using scientific knowledge

Optional project instructions:

• Propose two different options for research at home: Which will be the most sustainable option? The use of paper or plastic bags The use of disposal or cotton diapers

• Project will be done in groups of three. • Explain students that their proposed research has to include:

• A reasonable and argued hypothesis. • Materials used and experimental process. • Observation notes followed during the research. • Conclusions (led by these observations) and discussion. • Final recommendations.

• Allow them a week to complete the project.



Recommended key for project rubric

Project Evaluation Student 1 Student 2 Student 3

Complete explanation 1 point

Title name and

presentation 1 point

Scientific methods

applied 2 point

Argued hypothesis 2 point

Reliance between

observation and

conclusions

2 points

Final discussion and

recommendations 2 points

Student own proposed

park (orientative)

Increase of 10 % due to

global evaluation

max. 1 point

Final mark (maximum) 11 points

Activity number 14: THE NEWEST POLYMER (optional p roject)

Objective: To analyse the future of polymers

• Write on the board

• Present the future.

Polymers proprieties can be changed by using polymers derivatives of composites. Therefore, a large number of materials are developed for food processing and packaging, health, housing, transportation and construction. In addition to polymer uses and due to its particular modified properties, they have an important role as structural

Plastics are used in many different items

A polymer can be presented in many different aspects

Plastic precursors are produced from crude oil

Plastic is an inexpensive product



materials, well known in orthopedics, trauma and, in general, in medical applications.

• Ask students to read the following text. • Pair work. Ask them to write: 2 comprehension questions, 2 analysis questions and 2 synthesis questions.

• Ask them to answer the questions.

Skin Substitutes Skin is the largest organ in the body and its lost is an important medical problem that occurs, yearly, to millions of people. In case of skin lost there are two important medical points:

Solve the problem and replace the skin

In minor affections skin from the patient is used to replace the damaged zone, but larger surfaces need donors. In this situation, skin from a human donor or other species is being used with limited success, due to rejection problems or the short supply of human donors. Useful skin and skin substitute, as well, have to meet the following requirements:

Be bacterially balanced

Allow nutrition and hydration

Keep the zone vascularized

In addition, it needs a suitable cosmetic and functional effect. Skin substitute research is a new field. Actually, there are some skin substitutes that provide temporary coverage for tissue: protection and stimulation. Furthermore, these substitutes minimize the rejection problems and transmission of diseases from the donor. Approaches to the use of skin substitutes consist of synthetic polymers or collagen products that act as a matrix to human cells culture. Therefore, these are the cells that secrete the growth factors that allow the tissue to be repaired.

Two current products2 on the market are:

Dermograf®, Smith and Nephew Inc. Fibroblasts culture on a synthetic absorbable matrix.

Transcyte®, Smith and Nephew Inc. A two layer semi-permeable product that allow fluid and gas exchange. The inner layer presents a high adherence to human tissue.

Integra®, Integra Life Sciences (Allied with Johnson and Johnson) Bilayer, biodegradable matrix, made of a porous matrix of fibers of cross-linked fibers with a controlled porosity and degradation rate. The temporary epidermal substitute layer is made of synthetic polysiloxane polymer (silicone) with a moisturizing function.

• Individual work. • Ask students to write a short article about one new polymer or new research on polymers.

• First they can search the internet for two or more article about a new polymer of their choice.

• Encourage them to look for a comprehensive text.

2 Information base on http://woundhealer.com/Sknsub/Skin%20Sub%201.htm



• Recommended topics:

• Plastics in building materials • Plastics in optics • Plastic laser • Plastics in orthopedics • Plastics as substitutes for skin and veins • Fireproof plastics • Chemical resistant plastics • New drug delivery

• In their article or summary, students should answer the following questions: • What do they tell us about the use of plastic in the article? • Who is explaining it? • In which properties depend on the use on the analyze plastic? • What is improved by using a plastic?

Polymer classification

• Allow 15 minutes for the explanation. • Ask the students to take notes.

Types of Polymers Plastics are polymers that can be moulded or shaped by temperature and pressure. They do not have elasticity (compare to elastomers) All plastics are polymers but not all polymers are plastics

Some plastic polymers: nylon, cellulose acetate …….., can be obtained in fibre form. Elastomers (rubber) have a loose cross-linked structure. They possess memory and as the proportion of cross-link rises the material becomes more rigid and brittle. Thermoplasts

Thermoplasts can be softened or hardened by temperature. As temperature increases they soften and harden when decreases. That is a reversible process that can be repeated and allow thermoplasts to be remolded. Thermoplasts are usually linear polymers with a less branched structure which increases its flexibility.



Thermosets

Thermosets become permanently hard and do not soften when heated. When a thermoset is produced, initial heat treatment allows cross-link covalent bonds to be formed and harden the polymer permanently. Thermoset polymers are usually harder and stronger than thermoplastics. Cross-linked and network polymers are mainly thermosets.

To the teacher: Scientific Principles Depending on their behaviour when heated, polymers are classified as: Thermoplastics soften and remodel by heating. Easily recycled. Semi-crystalline or amorphous linear polymers. Thermoplastics are synthesized through addition or condensation polymerization. They have covalent bonds (strong) within the chains and Van der Waals bonds (weak) between the chains. These Van der Waals bonds break as temperature increases and allow reorganization by moulding, retaining new shape after cooling. Common applications of thermoplastics include: household appliances, bottles, cable insulators, tape, medical appliances, textiles, packaging, and insulation. Thermosets, do not soften as headed, and resistant to pressure. Difficult to recycled and, therefore, usually destroyed by incineration (energy production). They have covalent bonds (strong) within the chains and Van der Waals bonds (weak) between the chains, But they have covalent bonds (strong) that hold together the polymer chains, creating a crosslink structure and giving resistance to head. Thermosets must be machined into a new shape or its power use as a filler. Therefore, the most extreme option for rejected thermosets is incineration in thermic power plants. Although these difficulties they present certain properties that made them advantageous:

• High thermal stability • Insulating properties. • High rigidity and dimensional stability. • Mechanical resistance. • Chemical resistance. • Light-weight.

Common applications of thermosets include epoxies (glues), automobile body parts, and matrix for composites in construction and transport.



Activity number 15: IN THE STORE NEXT DOOR (homewor k, optional)

Revise knowledge and identification of polymers

• Individual work. • Suggest that students look around a grocer’s discount store searching for objects and uses of plastics.

• Remind them that a plastic object does not have to look like it is made of plastic. • Recommend them to use a digital camera to take photos of the objects. • Give a grid with space for the photos, symbols and names of the polymer, and use of the object.

• If they cannot use a digital camera ask them to draw or describe it.

Note: Plastic could be painted, like some decorative figure, or even can look metal.lized. Remember that most paint, glues, etc are polymers, and that nature is full of polymeric structures.

Grid

Hi, Gemma. Have you hear your brother?

Yes………………… All right Joan. Ask father for the camera and let’s go to the store.

Sis, could you help me with my homework? My chemistry teacher wants me to make a collection of pictures of plastic objects.



Key

Remember that this is the same grid as the one used in activity number 2. Teacher can expect something similar to this.

Activity number 16: MODELLING A POLYMER

Objectives: To observe properties of thermoplastic polymers

To analyse processing of thermoplastic polymers

• Remind the students about the difference between thermoplastic and thermoset polymers. Write on the board.

• Ask students these two questions. Allow some time for discussion. � Can a thermoplastic polymer be used in electrical accessories? Why? Whiy not? � Which ones, thermoplastics or thermosets can be easily recycled?

Key

Thermoplastic polymers, as they get softened by an increase in temperature, are not useful for electrical appliances, that could get melted through the regular lost of thermal energy in electricity transport. On the other hand, this capacity to soften easily made it simple to recycle them shaping in another form. Thermosets do not have this capacity and, therefore, they are mainly destroyed by incineration in power plants.

• Pair work in the laboratory. • Allow 12 minutes. • Explain that they will work with a thermoplastic that can be moulded at low temperature. It only needs hot water to soften and, therefore, it can be moulded by hand.

• Distribute the materials, including a small amount of Shapelock3 polymer. • Ask them to think about a little object that then want to mould.

Note: Shapelock is a plastic that it is hand moldable after soften it in hot water. Shapelock is a polymer similar to polypropylene that has a very low softening point. It can be softens around 55 to 60ºC. Therefore students can mold the softened plastic with their own hands. After molding, allow the plastic to cool and it takes-on its hard form.

3 Shapelock polymer can be ordered through the URL http://www.shapelock.com/

Thermoplastic polymers (they melt) are affected by temperature

and can be modeled.

Thermosets are polymers that can be burned but they don’t melt.



Key

Being low temperature thermoplastic, accepting acrylic paint, dyes and pigments, it is excellent for modeling hobbies and reconstruction of decorative objects. You can suggest your students enter the URL (http://www.shapelock.com/) and find out about the polymer appliances (it would be a nice and short writing practice)

Notes for the teacher This is some information from the ShapeLock website. ShapeLock, thermoplastic polymer is: Super Tough, Safe and Non-Toxic. Reusable - Just reheat to remold again and again. ShapeLock is a low molecular weight, low temperature thermoplastic polymer. It is a super strong, similar to Nylon or Polypropylene. At the present, they offer to send you a free 35 g sample charging 4,95$ for shipping expenses. It’s a limited offer, and you should ask for information about shipping it abroad.

Objective

Apply thermoplastic polymer properties

Observe the processing and recycling possibilities of a thermoplastic

polymer

Materials and supplies:

� Kettle to heat water � 250 mL beaker, forceps and thermometer � Shapelock®

Procedure 1. Design a little figure about 1 cm3 to mould.

2. Pour some hot water in the beaker and control the cooling temperature.

3. At 60ºC introduce the thermoplastic polymer in the hot water to soften it.

5. When it is soft enough take it out of the hot water using forceps and mould the figure with your hands.

Discussion

Discus with your partner which the polymer properties that allow us to work this way are, and what the uses of such a polymer would be. Focus on two questions:

� Can every thermoplastic polymer be moulded by hand? � Why can this polymer be modelled so easily?

Documents

Chemical change: Materials Nottingham, March 2006 Polymers · Chemical change: Materials Nottingham, March 2006 ... Polymers in use (project, ... Chemical change: Materials Nottingham,