Synchronous toughening and reinforcing of polypropylene with ultrahigh‐molecular‐weight polyethylene via melt blending: Mechanical properties, morphology, and rheology

Abstract

ABSTRACT:Blending systems based on polypropylene (PP) and ultrahigh-molecular-weight polyethylene (UHM-WPE) were prepared via a melt extrusion by the four-screw and the twin-screw extruders, respectively. The mechanical evaluation demonstrated that the synchronous toughening and reinforcing effects could be achieved from the combination of the PP and the UHMWPE, in which the toughness and the tensile properties could be improved with increasing the UHMWPE content, and achieved optimal values at a weight ratio of PP/UHMWPE (85/15). EPDM can be used as a compatibilizer to improve the compatibility and the interfacial adhesion between the PP and the UHMWPE. This resulted in more effective toughening and reinforcing effects. In contrast, for the PP/UHMWPE blends prepared by the normal twin-screw extruder, the poor dispersion capacity for the UHMWPE resulted in a deterioration of all mechanical parameters. Morphological observation revealed that the UHMWPE domain was well distributed as tiny particles in the PP matrix, which was confirmed by the differential scanning calorimetry analysis. The toughening effect was attributed to the energy dissipation caused by these rigid tiny particles that detached from the matrix to initiate the local matrix shear yield and formed the void. Rheological investigation demonstrated that there was an interesting composition dependence of viscosity, for which the melt viscosities of the PP/UHMWPE blends decreased when 5 wt % UHMWPE was added, and then began to increase as the UHMWPE content continued to increase. However, this dependence on composition became weaker because of the compatibilization of the EPDM.

Ultra‐high‐molecular‐weight polyethylene reinforced polypropylene and polyamide composites toward developing low‐noise automobile interior

“…Again, it can be noticed that the crystallinity of U60 phase was decreased by PP phase. The U60 chains were surrounded by PP phase and were difficult to form the crystalline structure compared to the neat U60 . The heating enthalpy (Δ H ) and crystallinity ( X c ) of PP phase were decreased with increase of U60 content, as shown in Table .…”

“…This is due to the toughening effect of UHMWPE. The UHMWPE is a flexible macromolecule; thus, the increase of UHMWPE content resulted in more effective deformation by absorbing high energy . Therefore, the impact strength of PP composites was increased with increasing the UHMWPE content.…”

“…The UHMWPE is a flexible macromolecule; thus, the increase of UHMWPE content resulted in more effective deformation by absorbing high energy. 8,13 Therefore, the impact strength of PP composites was increased with increasing the UHMWPE content. Izod impact strength of PA6 composites is shown in Figure 4(b), as a function of UHMWPE content.…”

“…9 In particular, UHMWPE has a relatively low friction coefficient, good self-lubrication performance, and excellent impact toughness, 8 due to its nonpolar, extremely long, and highly entangled molecular chain. 10,11 Some investigations for reducing the friction 8,[10][11][12] and improving the impact strength 8,10,13 by addition of UHMWPE into polymer materials have been reported. Li et al 10 and Wang et al 8 investigated the tribological and mechanical properties of UHMWPE/PA composites.…”

“…Liu et al 14 reported that appropriate ratio of PP and UHMWPE improves the tribological properties of the composites. Wang et al 13 employed the UHMWPE as an impact modifier for PP and found that the higher UHMWPE content can result in more effective deformation and high energy absorbing efficacy. These studies showed the positive effects of UHMWPE on tribological and mechanical properties of PP or PA composites.…”