Polymers:Polymers:Strength Variation Strength Variation

with Additiveswith Additives

Ariunaa Bayarbat, Scott Steffin, and Travis Yaeger

SRJC Engr 45

12/05/05

Instructor: Younes Ataiiyan

How do different additions How do different additions to a polyester polymer to a polyester polymer

affect its strength?affect its strength?

PolymersPolymers

Monomer– The basic building block of a polymer– The smallest repeating unit in a polymer chain– A polymer has a linear, branched, or network

structure of chained monomers

Polymerization– Initiation: Creation of the free radical, giving instability to

a monomer– Propagation: Monomer additions to the chain, passing

along instability– Termination: Removal of instability (free radical) through

combination with another unstable chain or impurity, or passage of instability to another monomer

Polymers form a network of interconnected branches, like knots, held together by hydrogen bonding and weak forces

Resin– “Any of numerous physically similar polymerized synthetics or chemically modified natural resins including

thermoplastic materials such as polyvinyl, polystyrene, and polyethylene and thermosetting materials such as polyesters, epoxies, and silicones that are used with fillers, stabilizers, pigments, and other components to form plastics.”

Polymer CategoriesPolymer Categories

Thermoplastic Thermoset

– Thermoset polymers get hard and rigid upon heating

– They retain their shape once they are cooled– They have network molecular structures– The polymerization process is enhanced by

higher temperatures and it is not reversible

Polyester Thermoset Polyester Thermoset Casting ResinCasting Resin

Reasons for choosing– Inexpensive– Clear– Easy to make samples– Thick enough for tests

ExperimentExperiment

Base sample– We mixed 100 g of the resin with 28 drops of the

catalyst MEKP (Methyl Ethyl Ketone Peroxide)– We poured it into a mold of 5”x 4.5”– Samples were about 0.25” thick

Four different samples with additions– 2.5 g of sawdust– 2 g of vitamin C (from vitamin C tablets)– 5 g of cornstarch – 28 more drops of the catalyst

We let the samples set for a week

We cut them into small pieces and uniform thickness

We performed a compression test on the samples

Stress/Strain Curve for all five Samples

0

10

20

30

40

50

60

0 0.1 0.2 0.3 0.4 0.5 0.6

Strain, _ (in/in)

Stress, _ (MPa)

Base

Corn Starch

Saw Dust

x-catalyst

Vitamin C

Sample

Area in itial

(m2 ) Area fin al (m2 )

Thinkness in

itial (m)

Thickness fin al

(m)Change in

Thickness (%)Elastic Change in Thickness (%)

Plastic Change in Thickness (%)

Modulus of Elasticity, E (Mpa)

Base 1.64E-03 1.76E-03 0.220 0.205 54.55% 47.73% 6.82% 332Cornstarch 7.82E-04 8.45E-04 0.200 0.185 55.00% 47.50% 7.50% 135

Sawdust 7.73E-04 8.88E-04 0.155 0.135 35.48% 22.58% 12.90% 69Extra Catalyst 3.44E-04 4.42E-04 0.225 0.175 55.56% 33.33% 22.22% 41

Vitamin C 4.83E-04 6.39E-04 0.185 0.140 45.95% 21.62% 24.32% 78

AnalysisAnalysis

Theoretically, the base sample was supposed to have the lowest strength because the additives caused more strength

The data show the base sample having the greatest strength

Real conclusions cannot be drawn from the data because of the many variables besides just the additions

ConclusionsConclusions

The result was different from what we expected The reasons for inconclusive results

– Different sample areas– Different sample thicknesses– The uneven testing surface

Things we would do differently– Uniform size for all samples– Much greater percentage of additions in each sample– Use better testing surface

ResourcesResources

Shackelford, James F. Introduction to Materials Science for Engineers. Upper Saddle River, NJ: Pearson Education Inc., 2005.

http://members.tripod.com/sunfh/chem13.htm http://en.wikipedia.org/wiki/Main_Page http://dictionary.reference.com/search?q=resin http://www.deutsches-kunststoff-museum.de/optimal/eplast01.htm http://wwwcp.tphys.uni-heidelberg.de/Polymer/day1/p4.htm http://www.franklinparrasch.com/index.htm