Thermal conductivity of polyethylene: The effects of crystal size, density and orientation on the thermal conductivity

Abstract

Thermal conductivity measurements were made on polyethylene samples which had been crystallized at different tem eratures in order to vary density and lamellar crystal oriented by mechanical shearing and by crystallization in a temperature gradient. The thermal conductivity increased linearly by 50% as the density went from 0.96 to 0.99 gm/cc. By orientation the conductivity was increased ten fold in the direction of molecular orientation and decreased two fold in the perpendicular direction. For samples oriented by deformation at different temperatures, the conductivity apparently correlates with birefringence. thic E ness. Tests were also made on polyethylenes which were

Residual stresses in gas-assisted injection molding

“…Such observations were reported by, e.g., Hansen and Bernier (1972) and van den Brule and O'Brien (1990) and explained on the basis that the heat conductance is much higher along covalent bonds than throughout weak secondary bonds. Furthermore, the anisotropy resulting from the frozen-in molecular orientation can differ substantially according to the molecular structure of the polymer, being favored by linear compact polymers, and for polymers with higher relaxation times and molecular weight.…”

Photoinduced p‐ to n‐type Switching in Thermoelectric Polymer‐Carbon Nanotube Composites

“…[ 12,13 ] Interestingly, the thermal conductivity of bulk polymers as well as conjugated macromolecules can be tuned by controlling molecular orientation. [14][15][16] In order to increase the modest electrical conductivity of polymers, a number of strategies have been proposed, including careful doping, [ 4,11,[17][18][19][20][21] making composites of polymers with conductive fi llers such as CNTs, [22][23][24] or fabricating multilayer composite A broad range of organic electronic applications rely on the availability of both p-and n-type organic semiconductors, and the possibility to deposit them as sequential layers or to form spatial patterns. Examples include transport layers in diodes (OLEDs, photovoltaics, etc.…”

Development of Highly Thermal Conductive Liquid Crystalline Epoxy Resins for High Thermal Dissipation Composites

“…l은 재료의 기하학적 구조에 따른 phonon의 정적 산란과, 분자 및 격자진동의 비조화성에 의한 phonon간의 충돌에 따른 동적 산란에 의해 결정된다 [4]. 따라서 [11].…”