Effect of entanglement on brittle‐ductile transition in polyethylene

Abstract

The brittle ductile transition temperature (BDTT) of polyethylene with different degrees of entanglement density produced by crosslinking was evaluated using the Charpy impact test. BDTT was defined as the temperature at which the Charpy impact value Et changed abruptly from low to higher values. The increase in entanglement density brought about only a slight fall in BDTT, although that led to an increase in Et at ambient temperature corresponding to the occurrence of a dimple type fracture. A transition model between brittle fracture, patchwork type fracture (craze‐like) and yielding deformation, depending on the degree of crosslinking, was proposed to explain those experimental results.

Silane grafting and moisture crosslinking of polypropylene

“…Interestingly, unlike the other compositions, the crosslinked specimen made with Process 3 (54 wt% gels) did not exhibit a plateau modulus above the 168°C melting point of the polypropylene. Instead, its storage modulus in the melt state increased with temperature, consistent with the theory of rubber elasticity, E = 3ρ RT / M c (where E is the elastic modulus; ρ is the density; R is the gas constant; T is the temperature; and M c is the number‐average molecular weight of the polymer between crosslinks) [16].…”

Effects of ethylene‐octene copolymer (POE) on the brittle to ductile transition of high‐density polyethylene/POE blends

“…Toughening modification is to change the polymer from brittle to tough behavior, that is, to improve the toughness and even to realize the brittle to ductile transition (BDT). [9][10][11] The transition of the blends is related to the matrix, [12] the dispersed phase, [5,6] the operating temperature, [12] the strain rate, [13] and so on. There are sufficient studies on the transition of polypropylene (PP)/ POE and other polymers.…”