polymers: strength variation with additives
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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
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