Please explain the process in detail and how option 1 was determined to be the b
ID: 2088364 • Letter: P
Question
Please explain the process in detail and how option 1 was determined to be the best answer. Explain in great detail
A linear partially crystalline polymer is heated from-150 Cto the Tm +100 C and cooled back to 150 C. Tm is the melting temperature of the crystals. If the rate of cooling is changed it is observed that the faster the cooling the lower the crystallization temperature. This temperature dependence is due to: When the temperature decreases the critical radius crystal nuclei needs to obtain for growth to be favorable decreases. This effect will speed up crystallization. The time needed for form a stable crystal nuclei is a decreasing function of the nuclei radius When the temperature decreases the critical radius crystal nuclei needs to obtain for growth to be favorable increases. This effect will slow down crystallization. The time needed for form a stable crystal nuclei is a decreasing function of the nuclei radius When the temperature decreases the critical radius crystal nuclei needs to obtain for growth to be favorable decreases. This effect will speed up crystallization. The time needed for form a stable crystal nuclei is an increasing function of the nuclei radius When the temperature decreases the critical radius crystal nuclei needs to obtain for growth to be favorable increases. This effect will slow down crystallization. The time needed for form a stable crystal nuclei is an increasing function of the nuclei radiusExplanation / Answer
Crystalline polymers have high shrinkage rates as they cool from their melted state. Almost all molten polymers have a completely amorphous structure lacking in molecular orientation. However, crystalline polymers develop a partially crystalline structure upon cooling, which is their natural or relaxed state. Crystallization causes the polymer to increase its density as the crystal structure forms. The molecules form a more ordered and more tightly packed structure than the amorphous structure.
Crystallization proceeds very rapidly at a temperature midway between the melting point and glass-transition temperature of the polymer. As the temperature is reduced below that maximum, the rate of crystallization decreases rapidly because the molecules have reduced freedom of movement to achieve their relaxed state. In most processes 60% to 80% of the crystallization takes place during the cooling phase of processing, and as much as 90% occurring within a week of processing. Remaining crystallization can take months to complete, depending on temperature. However, crystallization continues until a stable crystal structure is achieved.