Exploring the entangled state and molecular weight ofUHMWPEon the microstructure and mechanical properties ofHDPE/UHMWPEblends

Abstract

Three types of ultra‐high molecular weight polyethylene (UHMWPE) with different entangled state and molecular weight were blended with high‐density polyethylene (HDPE) matrix by melt blending. Rheology, 2D‐SAXS, 2D‐WAXD, DSC, and mechanical tests were used to study the evolution and difference of microstructure and mechanical properties of the blends. The addition of weakly entangled UHMWPE enhanced the chain diffusion and chain orientation ability under a specific flow field. Thus, the rheological properties and mechanical properties of the blends were improved with the mix of weakly entangled UHMWPE. The mechanical properties enhancement effect of HDPE/UHMWPE blends with weakly entangled UHMWPE was owing to the shish‐kebab structure formed in the injection molding process. The molecular chains of UHMWPE with a low degree of entanglement and high molecular weight increased the lamella size and crystallinity of the blends during processing. This leads to the formation of more oriented shish structures and more kebab lamella. Besides, the molecular chains of weakly entangled UHMWPE were better interlocked and intertwined with other polyethylene chains in the amorphous region, acting as the tie molecules, significantly improving the impact resistance.

Morphology evolution and mechanical property enhancement of linear low‐density polyethylene by adding disentangled ultrahigh molecular weight polyethylene

“…The downward bending degree of Cole–Cole curve indicates the miscibility of UHMWPE/LLDPE, of which smooth semicircle shows good miscibility. Deviations from this shape indicate uneven dispersion and phase separation due to immiscibility 21–23 . It is obvious in the Figure 2b that LLDPE matrix and UHMWPE with the content of below 1 wt% have excellent miscibility, which is very close to the shape of pristine LLDPE sample.…”

The in situ synthesis of weakly entangled ultrahigh‐molecular‐weight polyethylene/polyethylene wax blends and its synergetic disentanglement effect on LLDPE reinforcement

“…The strong motion ability of the PE wax chains might influence the crystallization behavior and entanglement state of the growing polyethylene chains, which will be explained in the following section. [25][26][27] Besides, the particle size distribution index (PDI, $2.0, see Table 2) of UHPE-X% samples exhibit nearly no changes with PE wax addition, illustrating the similar coating effect on the particles of different sizes. UHPE-X% sample with 30 min of polymerization time (i.e., UHPE-20%-30 min in Table 1) was also synthesized for comparison of the average particle size.…”

Twist springback and microstructure analysis of PEEK sheets in ultrasonic-assisted thermal incremental forming

“…In the forming process of semi-crystalline polymers, a series of changes occur, such as reorientation of molecular chain, crystal breakage and microcrystal rearrangement. In addition, the mechanical properties of semi-crystalline polymers are closely related to the orientation of molecular chains, crystallinity and crystal structure [21,22]. Therefore, it is of great signi cance to investigate the microstructure evolution of semi-crystalline polymers during the SPIF process.…”