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| | Polymer engineering FAQ - Eng-Tips |
 | | Crystalline polymers, such as polyethylene and polypropylene, exist as composites of regularly-ordered, closely-packed, hard, crystalline segments in a matrix of unordered, rubbery, amorphous polymer. |
 | | It is possible for entangled “loose loops” to occur --- looped segments of the same molecule which initiate and terminate within the same crystalline entity, with the central portion forming a loop in the amorphous matrix. |
 | | It is the molecular segment which initiates in one crystalline domain, crosses the amorphous region and, yet, has enough length to become securely locked in an adjacent crystalline phase, the so-called “tie molecule”, which provides the strength to keep the crystalline and amorphous phases from separating under even the slightest load. |
| www.eng-tips.com /faqs.cfm?fid=1000 (550 words) |
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