For an application of high strength components including gears cams and rollers the desired properties in a plastic would be high tensile and impact strength, stability at high temperature, and machine ability. Potential materials which are suitable for these applications are nylon phenolics, TFE filled acetals, PET, and poly carbonate. True or false.

Reaction injection molding is used for which one of the following plastic types: thermoplastics thermosets

1. Explain in 1-3 bullets how as a practicing engineer you determine the yield strength of a thermoplastic polymer from a tensile stress-strain curve. 2. Explain what is happening at the yield strength for a thermoplastic polymer from a physical standpoint in 1-3 bullets. (e.g. what are the atoms or polymer chains doing?)

An unknown polymer sample was found to have the following molecular weight distribution: Molecular weight range Xi Wi 8,000 – 20,000 0.05 0.02 20,000 – 32,000 0.15 0.08 32,000 – 44,000 0.21 0.17 44,000 – 56,000 0.28 0.29 56,000 – 68,000 0.18 0.23 68,000 – 80,000 0.10 0.16 80,000 - 92,000 0.03 0.05 What would the weight average molecular weight of the sample be if, we had filtered the monomer mixture with a 44 kDa dialysis tubing before preparation? (Hint: a dialysis tubing of a known molecular weight, only keeps molecules larger than that size)