Plastics / Elastomers question?

Question

Discuss the similarities & differences in natural rubber(NR) and polybutadiene rubber(BR) and their non-elastomeric analogues, polyethylene & polypropylene. Why are PE & PP analogues of NR & BR?

thanks for your help

Answer 1

1. Similarity: they are both long chain hydrocarbons, composed entirely of C and H (neglecting impurities).

2.  Differences:

a)  The rubbers contain unsaturation, -(CH=CH)-, throughout the chain, whereas PE and PP are fully saturated, contain only -(CH2-CH2)- and/or -(CHCH3-CH2)- groups.

b)  This unsaturation enables the rubbers to be cross-linked across the double bond to make useful elastomers...whereas PE and PP are used as made, molded into rigid/flexible products.

c)  Rubbers are used where elasticity is needed, PE and PP for their shape-retaining quality.

3.  They fit the definition of analogues because they are similar in structure, but contain a difference...as discussed above.