Eugene Chang Chem 4491 Dr. Buckley Fall 2010 MANIPULATING CROSSLINK DENSITY OF EPM/EPDM POLYMER EPM/EPDM is an ethylene propylene (diene) monomer that is a synthetic rubber and has a wide range of applications. The difference between the two compounds is found in the diene, in which a double bond is formed during the vulcanization process and increases the crosslink density; this will increase tensile strength without subtracting from any other properties. During the special problems class with Dr. Buckley, we performed several tests to refine data from previous experiments. Small samples of EPM/EPDM, containing various cured content, was placed in a soxhlet extractor with a xylenes solution. The samples were immersed in fresh xylenes solution at intervals proportional to the setting of the potentiometer. This provided continuous extractions over the course of a week. Samples were allowed to dry for a week and the xylenes pot was distilled using a simple distillation apparatus and recycled for additional soxhlet extractions. The EPM/EPDM samples no longer contained traces of the cured packages, assisted in the homozygous blending of the polymer, and was immersed in cyclohexane for a week. Cyclohexane would cause the polymer to swell and the samples could then be weighed to determine the gel fraction. The gel fraction would reveal the cross link density or the double bond formation from the blending process. DATA Table 1 – Swelling data SAMPLE initial mass gel mass SWELLING MASS EPM50C200GB#2 EPDMC30GB2 EPM0C200GB EPM50C60GB EPDMC80GB2 EPM50C125GB EPM50C2256B EPM50C40GB 0.3014 0.3806 0.2936 0.2508 0.398 0.39 0.3983 0.3607 0.1775 0.3521 0.2715 0.1542 0.383 0.2354 0.2327 0.226 0.9463 2.5075 0.9031 1.016 1.6017 1.2668 1.26 1.7717 Table 2- Gel fraction determination volume rubber 0.20882353 0.41423529 0.31941176 0.18141176 0.45058824 0.27694118 0.27376471 0.26588235 mass of solvent 0.7688 2.1554 0.6316 0.8618 1.2187 1.0314 1.0273 1.5457 molar volume volume volume network solvent fraction solvent density 0.986906 0.174641 108.0359 0.007404 2.766881 0.130217 108.0359 0.005776 0.810783 0.282617 108.0359 0.011553 1.10629 0.14088 108.0359 0.006166 1.564442 0.223614 108.0359 0.009239 1.324005 0.172986 108.0359 0.007343 1.318742 0.171908 108.0359 0.007303 1.984211 0.118165 108.0359 0.005335 Figure 1 – Network density The network density was determined by using the equation: -[(LN(1-Vr)+ Vr+X Vr2) = V Vs(Vr1/3-2 (Vr/f)) The term Vr is the volume fraction of the rubber sample, X is a constant of 0.35, v is the network density, and Vs is the molar volume of the solvent. The density of the polymer is 0.85 g/cc and the solvent was 0.779 g/cc. Dimensional analysis was used to determine the molar content of the solution and polymer. The equation was rearranged to solve for v (network density). The numbers of crosslinks have now been identified and the samples can be placed under a tensile stress test to determine the ideal blending process.