The influence of hoop shear field on the structure and performances of glass fiber reinforced three-layer polypropylene random copolymer pipe

Polypropylene Random Copolymer Based Composite Used for Fused Filament Fabrication: Printability and Properties

Fused filament fabrication (FFF) is one of the most commonly used additive manufacturing technologies. However, the applied material for commercial FFF is limited. Presently, though being one of the most used polymer materials, polypropylene (PP) is rarely used in FFF because of its serious warpage and shrinkage problems. This study investigated the impact of addition of short glass fibers (GF) and ethylene propylene diene monomer (EPDM) on the printability of polypropylene random copolymer (PPR) based FFF and mechanical properties of the printed samples, as well as other properties including rheology, thermal behaviors, and morphology. The results show that the modified PPR has excellent printability, as the printed samples are of good geometrical accuracy. The addition of GF can significantly improve the strength and modulus of the composite, but it also leads to serious decrease in toughness. EPDM addition can effectively improve the toughness of the composite, showing a complementary effect with GF. This work has important meaning in expanding the FFF applicable material and in broadening the application of PP.

Mechanical and Processing Enhancement of a Recycled HDPE/PPR-Based Double-Wall Corrugated Pipe via a POE-g-MAH/CaCO3/HDPE Polymer Composite

With the people's awareness of the "3Rs" in recent years, using recycled high-density polyethylene (HDPE) and random copolymer polypropylene (PPR) as the base materials for piping fabrication has become a mainstream in scholastic path and industrial engineering. In this study, the modified maleic anhydride-grafted polyethylene (POE-g-MAH) compatibilizer was fabricated to increase the interfacial adhesion and dispersion. With the surface modification of calcium carbonate, a POE-g-MAH/CaCO3/HDPE polymer composite has been prepared. Such modified polymer composites can further reinforce the processing performance and mechanical properties of recycled HDPE and PPR materials. The results indicated that with the introduction of the polymer composite, significant enhancement of the recycled materials in the aspects of processability, tensile strength, flexural performance, and impact force could be obtained, and the POE-g-MAH/CaCO3/HDPE polymer composite would contribute to the impressive balance between high rigidity and toughness. In addition, the feasibility and mechanical properties of the recycled HDPE-PPR-POE-g-MAH/CaCO3/HDPE blended system were also studied: with the help of a composite microcapsule, the gap of mechanical capacity between recycled and non-recycled materials was further reduced, and such a blended system was capable of being commercialized in the piping industry.

Role of Melt Plasticizing Temperature in Morphology and Properties of PE100 Pipes Prepared by a Rotational Shear System

To increase the maximum internal pressure that a polyethylene (PE) pipe can withstand, a novel rotational shear system (RSS) was constructed in this study to fabricate PE pipes with enhanced hoop strength by applying hoop shear on the pipes using a rotational mandrel. The microstructure and morphology with the influences of melt plasticizing temperature on PE pipes processing under rotational shear were investigated indirectly using small-angle X-ray scattering and wide-angle X-ray diffraction (SAXS/WAXD) measurements. In the SAXS patterns, equatorial streaks and meridional scattering peaks were clearly observed in all three samples prepared at different melt plasticizing temperatures, 215, 235, and 255 °C. Their presence indicated that shish-kebab crystals form in rotational shear. Compared to those at the low melt temperature, the increase in the melt temperature enhanced the amount and the dimensions of shish formed. However, the shish also relaxed faster at the high melt temperature. This behavior was attributed to the enhancement of the molecular chain's athletic ability. The hoop tensile strength and the heat resistance of the pipes peaked at the melt plasticizing temperature of 235 °C, 75.2 MPa, 102.4 °C, up 1 MPa, 0.2 °C (compared to the 215 °C) and 7.8 MPa, 3.2 °C (compared to the 255 °C). The axial strength increased with an increase of melt plasticizing temperature. However, the increase of melt plasticizing temperature worsens the inherent good tensile toughness of PE100 pipes as the axial elongation at break decreases.