How does each of the following influence the tensile modulus of a semicrystallin

Question

How does each of the following influence the tensile modulus of a semicrystalline polymer? (a) Molecular weight decrease (b) Degree of crystallinity increase (c) Deformation by drawing (d) Annealing of an undeformed material (e) Annealing of a drawn material (a) - non-direct influence, (b) increase, (c) increase, (d) increase, (e) - decrease (a) non-direct influence, (b) increase, (c) - decrease, (d) decrease, (e) - decrease (a) - increase, (b) decrease, (c) - decrease, (d) increase, (e) - decrease (a) non-direct influence, (b) increase, (c) - decrease, (d) increase, (e) - decrease

Explanation / Answer

(a) The tensile modulus is not directly influenced by a polymer's molecular weight.

(b) Tensile modulus increases with increasing degree of crystallinity for semicrystalline polymers. This is due to enhanced secondary interchain bonding which results from adjacent aligned chain segments as percent crystallinity increases. This enhanced interchain bonding inhibits relative interchain motion.

(c) Deformation by drawing also incrcases the tensile modulus. The reason for this is that drawing produces a highly oriented molecular structure, and a relatively high degree of interchain secondary bonding.

(d) When an undeformed semicrystalline polymer is annealed below its melting temperature, the tensile modulus increases.

(e) A drawn semicrystalline polymer that is annealed experiences a decrease in tensile modulus as a result of a reduction in chain-induced crystallinity, and a reduction in interchain bonding forces.

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