✦ LIBER ✦
Mechanisms for axial thermal contraction in polymer crystals: polyethylene vs isotactic polypropylene
✍ Scribed by Daniel J. Lacks; Gregory C. Rutledge
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 759 KB
- Volume
- 49
- Category
- Article
- ISSN
- 0009-2509
No coin nor oath required. For personal study only.
✦ Synopsis
We show that the mechanism for the negative axial thermal expansion is fundamentally different in polyethylene (PE) and isotactie polypropylene (iPP) crystals. For PE, axial contraction increases the entropy, thereby leading to negative axial thermal expansion. In contrast, for iPP, axial expansion increases the entropy, which alone would lead to positive axial thermal expansion. The negative axial thermal exoansion in iPP occurs as an elastic re.sDonse to the positive transverse thermal expansion. and is based on potential energy effects.