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A SEMINAR ON A SEMINAR ON Characterization of PolymerCharacterization of Polymer

PRESENTED BY PRESENTED BY Mr. A.V.PATIL Mr. A.V.PATIL

I st sem M. pharm (Pharmaceutics) I st sem M. pharm (Pharmaceutics)

GUIDED BYGUIDED BYMr . S.G.BIDKARMr . S.G.BIDKAR

Department of PharmaceuticsDepartment of Pharmaceutics

AISSMS COLLEGE OF PHARMACYAISSMS COLLEGE OF PHARMACYPUNEPUNE

23/09/200923/09/2009

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CONTENTS INTRODUCTION

History of Polymers    Definition

  TYPES OF POLYMER Classification of Polymers    Characteristics of Polymers Properties of Polymers

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1. Characterization of Polymer1. Chemical properties

2. Thermal properties

3. Mechanical properties

4. Other techniques

References

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INTRODUCTIONHistory of Polymers     

In 1920 that German chemist Hermann Staudinger (1881–1965)

• Rewarded with the 1953 Nobel Prize in Chemistry

Made his macromolecular hypothesis, suggesting that polymers are molecules formed by the permanent attachment of countless smaller molecules.

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Definition Polymers are substances whose molecules

have high molar masses and are composed of a large number of repeating units 

The number of repeating units in one large molecule is called the degree of polymerization. Materials with a very high degree of polymerization are called high polymers. Polymers consisting of only one kind of repeating unit are called homopolymers. Copolymers are formed from several different repeating units.

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TYPES OF POLYMER

NATURAL POLYMER EX- proteins, starches, cellulose, and latex

SYNTHETIC POLYMER

EX- Polymethyl methacrylate

Polystyrene Polyvinyl Chloride

Polystyrene

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Classification of Polymers         

According to the mechanical response at elevated temperatures

•Thermoplasts

polymers soften when heated and harden when cooled

•Thermosets: Thermosetting polymers become soft during

their first heating and become permanently hard when cooled. They do not soften during

subsequent heating.

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Characteristics of Polymers:

           Low Density Low coefficient of friction Good corrosion resistance Good mouldability Excellent surface finish can be

obtained

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Can be produced with close dimensional tolerances

Economical Poor tensile strength Low mechanical properties Poor temperature resistance Can be produced transparent or in

different colors

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Properties of Polymers:            Chain length - in general, the longer the

chains the stronger the polymer; Side groups - polar side groups give stronger

attraction between polymer chains, making the polymer stronger;

Branching - straight, unbranched chains can pack together more closely than highly branched chains, giving polymers that are more crystalline and therefore stronger;

Cross-linking - if polymer chains are linked together extensively by covalent bonds, the polymer is harder and more difficult to melt.

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Polymer characterization

1 Chemical structure 2 Thermal properties 3 Mechanical and dielectric spectroscopy 4 Morphology 5 Other techniques

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Chemical properties

Molecular weight distribution Additives analysis Volatile organic compounds and odors Residual monomers Identification and quantitation of formulation

components Water content Identification and determination of structural

polymer design (branding, copolymer, composition, functionality and end capping)

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complex chemical structure of polymers polymeric material typically consists of a distribution

of molecular sizes and sometimes also of shapes Chromatographic methods like size exclusion

chromatography often in combination with Low-angle laser light scattering (LALLS)

viscometry can be used to determine the molecular weight distribution as well as the degree of long chain branching of a polymer,

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Thermal properties THREE MAIN THERMAL ANALYTICAL TECHNIQUES

•THERMOGRAVIMETRY (TG). THERMOGRAVIMETRY (TG).

•DIFFERENTIAL SCANNINGCALORIMETRY (DSC).DIFFERENTIAL SCANNINGCALORIMETRY (DSC).

• DYNAMIC MECHANICAL ANALYSIS (DMA)DYNAMIC MECHANICAL ANALYSIS (DMA)

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Thermogravimetry (TG)

“It is a technique whereby the weight of the substance, in an environment heated or cooled at controlled rate, is recorded as function of time or temperature.”

Types of Thermogravimetry: 1. Isothermal thermogravimetry. 2. Quasistatic thermogravimetry. 3. Dynamic thermogravimetry.

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Principle In this method a substance is heated from

lower temperature to higher temperature at a fixed rate of heating. The changes in weight of the substance as it is heated to higher temperature are recorded as a function of sample temperature.

The graphical representation of weight as a function of temperature is called as thermogram.The weight should be plotted on ordinate with weight decreasing downwards & temperature on the abscissa increasing from left to right.

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It can be concluded that thermogravimetry is concerned with change in weight of the material as its temperature changes.

First, this determines the temperature at which the material loses weight. This loss indicates decomposition or evaporation of the sample.

Second, the temperature at which no weight loss takes place indicates stability of the material. These temperature ranges are physical properties of the chemical compounds & can be used for their identification.

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Instrumentation of Thermogravimetry

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Differential Scanning Calorimetry (DSC) Differential scanning calorimetry or

DSC is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference are measured as a function of temperature. Both the sample and reference are maintained at nearly the same temperature throughout the experiment. Generally, the temperature program for a DSC analysis is designed such that the sample holder temperature increases linearly as a function of time.

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Heat flux DSC

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Principle

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APPLICATION

Changes in the compositional and structural parameters of the material usually affect its melting transitions or glass transitions and For semicrystalline polymers it is an important method to measure crystallinity.

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Interpretation:- Tolbutamide and PEG 6000 form a eutectic with a

composition of 30 % TBA and 70 % PEG 6000 with the same melting point as the PEG 6000 used.

The peak A at about 39 0c corresponds to a solid – solid transition of tolbutamide.

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Evaluation :- The onset temperatures and the heats of fusion ΔH are evaluated from the melting curves.

Sample onset/ΔH Peak A0c

Peak A

J/g

Peak B0c

Peak B

J/g

Peak C0c

Peak C

J/g

TBA 100 % 39 8 - - 127 93

TBA 90%PEG 10 % 39.1 7.4 53.7 19.8 121.1 75

TBA 70%PEG 30 % 39.3 5.8 53.2 51.6 109 48

TBA 50%PEG 50 % 39.4 3.9 54.3 93.9 81.6 22.8

TBA 30%PEG 70 % 39.5 1.5 55.9 138.8 - -

TBA 10%PEG 90 % 39.5 0.3 55.3 166.7 - -

PEG 100 % - - 55 178 - -

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Phase Diagram.

It describes relationship between melting temperature and composition of multi component system.

To construct phase diagram mixtures of components with different composition are measured with DSC & data is evaluated.

Samples:- Tolbutamide and PEG 6000 as well as mixtures.

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The phase diagram can be constructed by plotting the onset temperature against the concentration of TBA (in weight present) The solid –solid transition of TBA occurs at about 390c Above 54 0c either the liquid or the solid phase is present

depending on the TBA concentration The dotted lines are extrapolations.

Conclusion:- Phase Diagram of Binary mixtures can be determined by DSC

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Dynamic Mechanical Analysis

The Q800 utilizes state-of-the-art, noncontact,

linear drive technology to provide

precise control of stress, and air bearings for

low friction support. Strain is measured using

optical encoder technology that provides

sensitivity and resolution. The Q800 is ideal

for high-stiffness applications including

composites.

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Morphology Morphological parameters- Osmometery Light Scattering Viscometry Gel permeation chomatography mesoscale (nanometers to microns) are very

important for the mechanical properties of many materials.

Transmission Electron Microscopy in combination with staining techniques,

Scanning Electron Microscopy, Scanning probe microscopy

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OSMOMETRY

Method Is used to determine number average molecular weight Mn.

Only osmatic pressure is sensitive enough to measure high molecular weight characteristic of polymer.

Semipermiable membrane through which solvent can pass ,which exclude polymer molecule.

One filled with pure solvent and one filled with polymer solution

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Activity of solvent in two compartment is different bcoz polymer molecule

Osmatic pressure driving solvent into polymer solution compartment will develop.

Osmatic pressure for ideal solution ∏∕C≈RT/Mn

To obtain Mn, ∏/c is plotted as function of C and extrapolated to C=0

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Osmometers (UIC) The Model 833 Vapor Pressure Osmometer is an

effective, easy to use tool for the determination of number average molecular weights of any non-volatile solute in the range of 100-25,000 Daltons.

The Model 231 Membrane Osmometer has the ability to determine number average molecular weights of any solute in the range of 20,000-1,000,000 Daltons

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Light scattering Scattering of light by liquid can be related to

local fluctuation in density due to thermal motion of molecule

With solution addition scattering arises from local fluctuations in the conc. Of the solute.

Measurement of light scattering of dilute polymer solution it is possible to drive the average molecular weight Mw.

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Simultaneous dynamic and static light scattering system

The ALV / CGS-8F Compact Goniometer is the common platform for a variety of different goniometer systems. Based on a rotary disk allowing finest angular steps to be performed (rather than a rotary arm) it has four detection angles separated each by 34° in angular space to allow simultaneous measurement of Staticand Dynamic Light Scattering at higher solution.

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Rheometer(TA Instruments)

The AR-G2 Rheometer is equipped with an environmental chamber for determining the rheology of a sample under controlled conditions. It has a built in viewer so that samples can be monitored through out the

experiment.

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Gel permeation chomatography Polymer molecules separated according to

their size Sephadex, Bio-Gel (cross-linked

polyacrylamide), agarose gel and Styragel are often used based on different separation

Measuring not only molecular weight but also molecular weight distribution

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Dilute polymer solution pumped through a series of columns containing porous beds with different pore sizes.

Small molecule take longest path and largest molecule take shortest path through columns

Highest molecule weight species emerges first and lowest mol.wt species will emerges last.

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Mechanical properties Determined by stress-strain relationship Stress-stretching force applied to sample Strain-elongation of sample under a given

stress. stress-strain relation in polymer are time

dependent Specimen clamped to Instron tester and

measuring force that specimen exerts on load cell

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STRESS

STRAIN

Fig-stress-strain curve for thermoplastic material (polyethylene)

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Fig-characteristic stress-stain curve for five different type of polymeric material

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Other techniques Solid state NMR Spectroscopic techniques: IR, FTIR etc.

The VERTEX 70 FTIR has a spectral range from 30 cm-1 in the far IR, through the near IR and up to the visible spectral range at 25,000 cm-1. The large sample chamber allows for a wide range of accessories with temperature and environmental controls.

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References Alb, A.M.; Drenski M.F.; Reed, W.F. "Perspective automatic

continuous online monitoring of polymerization reactions (ACOMP)" Polymer International,57,390-396.2008

US patent 6052184 and US Patent 6653150, other patents pending

Retrieved from http://en.wikipedia.org/wiki/Polymer_characterization

Instrumental Methods of Chemical Analysis by B.K.Sharma, Twenty first edition 2002 Page No.232-249

Instrumental Methods Of Chemical Analysis By Gurdeep R.Chatwal,Sham K Anand,Reprint 2005 Page No.2.701-2.738

Remington’s Pharmaceutical Sciences,20th Edition,Lippincott Williams & Wilkins 649,709

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Chemical structure