Study on processing of ultrahigh molecular weight polyethylene/polypropylene blends: Capillary flow properties and microstructure

Abstract

ABSTRACT:The capillary flow properties and morphologies of ultrahigh molecular weight polyethylene/polypropylene (UHMWPE/PP) blends were studied. The results show that UHMWPE is difficult to process. The melts flowed unsteadily at lower shear rate. With 10 wt % PP contained in the UHMWPE/PP blends, the apparent melt viscosity was much lower than that of UHMWPE. When the PP content increased to 20 and 30 wt %, no pressure vibration occurred throughout the whole shear rate range. Microstructure analysis showed that PP prefers to locate in the amorphous or low crystallinity zones of the UHMWPE matrix. The flowability of UHMWPE increased substantially with the addition of PP. The addition of PE could not effectively reduce the chain entanglement density of UHMWPE. The improvement of processability of UHMWPE by the addition of PE was rather limited.

Metastable region of phase diagram: optimum parameter range for processing ultrahigh molecular weight polyethylene blends

“…When χ is in the range of 9.0×10 -3 ∼ 4.1×10 -3 , no UHMWPE is located in the NMWP rich phase, which prevents the viscosity of NMWP from increasing. However, there is a significant amount of NMWP in the UHMWPE rich phase, which favors the swelling of UHMWPE powders [16,17]. When χ is lower than 3.7×10 -3 , interfacial thickness markedly increases with decreasing χ.…”

“…Due to the thick interfaces of the UHMWPE/NMWP blends, there was no substantial decrease of its excellent mechanical properties such as tensile strength and impact strength [15]. Similarly, in the UHMWPE/PP blend, the molten PP preferred to flow into the gaps between UHMWPE particles instead of wholly penetrating into the UHMWPE particles [16,17]. Consequently, the addition of PP significantly improved the melt flowability of UHMWPE and the die pressure was very stable during extrusion.…”

“…According to Takeshi S, Liu GD and others, some NMWP like LDPE and PP can conveniently and effectively reduce the viscosity of UHMWPE as well as retain or even enhance its mechanical properties [15][16][17][18]. Unfortunately, most other NMWP may cause a marked decrease in some of its desirable properties such as izod notched impact strength [19].…”

Influencia de la viscosidad en la incompatibilidad de mezclas de residuos de materiales plásticos en el proceso de reciclado

“…La miscibilidad de dos polímeros viene regida por las leyes de la termodinámica ( [18] Paul and Barlow, 1984). Si ∆G m es negativa en todo el rango de composiciones de la mezcla a una temperatura dada, los dos polímeros serán miscibles para cualquier composición.…”

“…Desde el punto de vista termodinámico, se define un parámetro representativo de la interacción entre los polímeros que forman la mezcla; se trata del parámetro B, o energía de interacción polímero-polímero ( [18] Siempre y cuando los valores de B sean inferiores a un valor crítico, B crit , el sistema mostrará solubilidad. Este valor crítico está relacionado con los pesos moleculares medios en peso de las especies que forman el blend a través de la expresión:…”