Interfacial compatibility of wood flour/polypropylene composites by stress relaxation method

Enhancing Stiffness and Oil Resistance of Fluorosilicone Rubber Composites through Untreated Cellulose Reinforcement

Fluorosilicone rubber, essential in automotive and aerospace owing to its excellent chemical resistance, plays a pivotal role in sealing technology, addressing the industry's evolving demands. This study explores the preparation and properties of fibrillated cellulose-reinforced fluorosilicone rubber composites to enhance their stiffness and oil resistance. Fibrillated cellulose sourced as a wet cake and subjected to processing and modification is incorporated into a fluorosilicone rubber matrix. The resulting composites are analysed by tensile and compression tests, along with compressive stress-relaxation testing in air and in an oil-immersed environment. The findings demonstrate significant improvements in the mechanical properties, including an increased Young's modulus and elongation at break, whereas the tensile strength remained uncompromised throughout the testing procedures. Morphological analysis of the fracture surfaces revealed a remarkable interfacial affinity between the fibrillated cellulose and rubber matrix, which was attributed in part to the modified fatty acids and inorganic nanoparticles. The presence of fibrillated cellulose enhanced the stress-relaxation characteristics under oil-immersion conditions. These results contribute to the domain of advanced elastomer materials, with potential for applications requiring enhanced mechanical properties and superior oil resistance.

Effect of phenyltrimethoxysilane coupling agent (A153) on simultaneously improving mechanical, electrical, and processing properties of ultra-high-filled polypropylene composites

The improvement of mechanical properties, electrical properties, and processing properties of ultra-high-filled thermal insulation polypropylene (PP) composites has been plagued by high filling amount of heat-conducting fillers such as alumina powder (Al2O3) and expanded graphite. In order to improve its properties, this article uses a high-temperature-resistant coupling agent (A153) to modify the PP composite. The results of this study show that when the content of A153 reaches 7.5 phr, the tensile strength of PP composite can reach 5 MPa, the elongation at break can reach 25%, and the volume resistivity can reach 12.8 × 1012 Ω·m, and the maximum thermal conductivity is 1.82 W·m−1·K−1. The processability also shows that the introduction of A153 can increase the melt flow rate and effectively improve the processability of the material.

Understanding the Stress Relaxation Behavior of Polymers Reinforced with Short Elastic Fibers

Although it has been experimentally shown that the addition of short-fibers slows the stress relaxation process in composites, the underlying phenomenon is complex and not well understood. Previous studies have proposed that fibers slow the relaxation process by either hindering the movement of nearby polymeric chains or by creating additional covalent bonds at the fiber-matrix interface that must be broken before bulk relaxation can occur. In this study, we propose a simplified analytical model that explicitly accounts for the influence of polymer viscoelasticity on shear stress transfer to the fibers. This model adequately explains the effect of fiber addition on the relaxation behavior without the need to postulate structural changes at the fiber-matrix interface. The model predictions were compared to those from Monte Carlo finite-element simulations, and good agreement between the two was observed.