1. There are 2 thermoplastic polymers: 1) HDPE and 2) PP. Which of
them will keep its initial properties while being exposed to the sun
for a longer time and why?
2. A HDPE sheet, 50 microns thick, is produced in one of the two
following ways: 1)Blowing or 2) Casting. Which process will produce a
more transparent sheet and why?

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Clarification of Question by shaynr-ga on 06 Jul 2005 21:46 PDT

Rephrasing Question 1:
For 2 thermoplastic polymers, HDPE and PP (Polypropylene), which one
will retain its initial properties longer while being exposed to the
sun, and why?