Question

a.) Speculate which variable: (a) reaction temperature, (b) conversion of monomer or (c) reaction mixture viscosity, would be the most important for tuning the degree of short chain branching in the high pressure process for making polyethylene using a batch reactor. Explain your reasoning.

b.) why is low density polyethylene (LDPE) low density?

Answer 1

A)This question is of research level which can be solved after performing actual experiments and analysing the results. Low Density Polyethylene(LDPE) is a high pressure process with the Free Radical Method technique. These radicals can attach to the chains and form branches in the length of the polymer unit. Typical conversion of the monomers to the final product is about 20%. The remaining unreacted product is recycled back to the reactor and again reacted. Since LDPE are synthesized by the mechanism of free radical transfer, thus conversion of monomers are of more importance than the other 2 variables for tuning the short chain branch. If the monomers are attached properly to the chains , then branching can be avoided.

B) Low Density in Low Density Polyethylene (LDPE) indicates the less number of monomer units present in the chain of polymer. This difference in the density from HDPE is due to the variation in the production method of both the polymers. LDPE is produced by free radical mechanism whereas HDPE polymers are synthesized using the ziegler-natta catalysts.

LDPE<0.943g/cm3

HDPE>0.943g/cm3