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

On the Mechanical, Thermal, and Rheological Properties of Polyethylene/Ultra-High Molecular Weight Polypropylene Blends

The novel ultra-high molecular weight polypropylene (UHMWPP) as a dispersed component was melt blended with conventional high-density polyethylene (PE) and maleic anhydride grafted-polyethylene (mPE) in different proportions through a kneader. Ultra-high molecular weight polypropylene is a high-performance polymer material that has excellent mechanical properties and toughness compared to other polymers. Mechanical, thermal, and rheological properties were presented for various UHMWPP loadings, and correlations between mechanical and rheological properties were examined. Optimal comprehensive mechanical properties are achieved when the UHMWPP content reaches approximately 50 wt%, although the elongation properties do not match those of pure PE or mPE. However, it is worth noting that the elongation properties of these blends did not match those of PE or mPE. Particularly, for the PE/UHMWPP blends, a significant drop in tensile strength was observed as the UHMWPP content decreased (from 30.24 MPa for P50U50 to 13.12 MPa for P90U10). In contrast, the mPE/UHMWPP blends demonstrated only minimal changes in tensile strength (ranging from 29 MPa for mP50U50 to 24.64 MPa for mP90U10) as UHMWPP content varied. The storage modulus of the PE/UHMWPP blends increased drastically with the UHMWPP content due to the UHMWPP chain entanglements and rigidity. Additionally, we noted a substantial reduction in the melt index of the blend system when the UHMWPP content exceeded 10% by weight.

Formulating Polypropylene with Desired Mechanical Properties through Melt Compounding of Homopolymer and Impact Copolymer

Many grades of homopolymer polypropylene (HPP) and impact copolymer PP (ICPP) with a wide range of mechanical properties have been developed for a variety of applications in different industrial sectors. Management of this wide range of materials is a challenge for material suppliers and manufacturers and product developers. This research was to provide insights for managing material supplies through formulating PP with specific mechanical properties using melt compounding of ICPP and HPP. ICPP and HPP were compounded with an internal mixer at different ratios and then the mixtures were injection molded into specimens for characterization. The mechanical behaviors, fracture surfaces, and thermal properties of the mixtures were then characterized. The fracture surface results indicated that the morphologies of the rubber particles in ICPP changed after compounding with HPP, leading to different mechanical and thermal behaviors of the mixtures. Notched and unnotched impact strengths increased linearly with increasing ICPP contents. The crystallization peak temperatures increased linearly with increasing ICPP contents while the degrees of crystallinity of the mixtures decreased linearly. The thermal compounding process and the original material properties mainly determine the final mixture behaviors, and the mixture properties can be predicted based on the weight ratios of the two components.

Ultra-High-Molecular-Weight-Polyethylene (UHMWPE) as a Promising Polymer Material for Biomedical Applications: A Concise Review

Ultra-High Molecular Weight Polyethylene (UHMWPE) is used in biomedical applications due to its high wear-resistance, ductility, and biocompatibility. A great deal of research in recent decades has focused on further improving its mechanical and tribological performances in order to provide durable implants in patients. Several methods, including irradiation, surface modifications, and reinforcements have been employed to improve the tribological and mechanical performance of UHMWPE. The effect of these modifications on tribological and mechanical performance was discussed in this review.