Effect of Ultra-High-Molecular-Weight Molecular Chains on the Morphology, Crystallization, and Mechanical Properties of Polypropylene

Abstract

The effects of the ultra-high-molecular-weight (UHMW) component of polypropylene (PP) on its rheological properties, crystallization behavior, and solid-state mechanical properties were investigated using various measurement techniques. The terminal relaxation time—determined by measuring the linear viscoelasticity—was increased by adding the UHMW component. The increase in the melt elasticity produced by adding the UHMW component was observed by measuring the steady-state shear flow, although the shear viscosity was not greatly affected. Owing to the long characteristic time of the Rouse relaxation of the UHMW component, PP with the UHMW component formed highly oriented structures through a shear-induced crystallization process. The addition of the UHMW component enhanced the orientation and regularity of crystalline structure for extruded films. Therefore, the Young′s modulus, yield stress, and strength were higher in the PP film containing the UHMW component than in one without the UHMW component, irrespective of the direction of tensile deformation.

Optimum processing conditions for the maximum crystallization rate of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

“…A camera was set up on the other eyepiece to investigate the morphology. The details and some experimental results obtained by this machine were reported in our previous papers 36,37 . Figure 1 illustrates the experimental protocols for temperature and shear.…”

Ultra-High-Molecular-Weight Poly(Dioxolane): Enhancing the Mechanical Performance of a Chemically Recyclable Polymer

“…This phenomenon, which is also observed in polyethylene, is attributed to the rise in tie-segments. Tie-segments refer to lengthy polymer chains that cross the amorphous regions as well as numerous crystalline domains. , A UHMWPE (∼5000 kg/mol) sample (Figure a) subjected to identical testing conditions endured a lower ultimate stress than 1656 kDa pDXL and lower ultimate strain than 1320 kDa pDXL. The mechanical performance of UHMW pDXL achieved here demonstrates the potential for pDXL as a chemically recyclable alternative to current thermoplastics (Figure a).…”

Anomalous Mechanical Response of Stretched Film of Poly(3-Hydroxybutyrate-co-3-Hydroxyhexanoate)

“…The present result suggested that rubber-like deformation occurred during the reloading process. It was also demonstrated that stress/strain-induced crystallization barely occurred for PHBHHx at 25°C, which is quite different from the case for conventional crystalline polymers such as polyethylene and PP [48][49][50][51].…”