Mechanical Properties of Injection Molded PP/PET-Nanofibril Composites and Foams

Abstract

The creation and application of PET nanofibrils for PP composite reinforcement were studied. PET nanofibrils were fibrillated within a PP matrix using a spunbond process and then injection molded to test for the end-use properties. The nanofibril reinforcement helped to provide higher tensile and flexural performance in solid (unfoamed) injection molded parts. With foam injection molding, the nanofibrils also helped to improve and refine the microcellular morphology, which led to improved performance. Easily and effectively increasing the strength of a polymeric composite is a goal for many research endeavors. By creating nanoscale fibrils within the matrix itself, effective bonding and dispersion have already been achieved, overcoming the common pitfalls of fiber reinforcement. As blends of PP and PET are drawn in a spunbond system, the PET domains are stretched into nanoscale fibrils. By adapting the spunbonded blends for use in injection molding, both solid and foamed nanocomposites are created. The injection molded nanocomposites achieved increased in both tensile and flexural strength. The solid and foamed tensile strength increased by 50 and 100%, respectively. In addition, both the solid and foamed flexural strength increased by 100%. These increases in strength are attributed to effective PET nanofibril reinforcement.

Lightweight and High Impact Toughness PP/PET/POE Composite Foams Fabricated by In Situ Nanofibrillation and Microcellular Injection Molding

“…First, PET nanofibrils can enhance the heterogeneous nucleation efficiency at interfaces, which improves cell nucleation. Second, PET fibrils can not only promote the viscoelasticity and strain hardening behavior of PP [ 48 ], but also increase the crystallization rate, which in turn improves the melt strength of PP in relatively high temperature. Both reasons can contribute to the reduction of cell coalescences and collapses.…”

“…For one thing, the refined crystals caused by PET fibrils can promote the flexibility and toughness of PP matrix. Due to the weak cohesive forces between PET molecular chains, the PET fibrils can enhance the sliding ability of PP crystals [ 48 ]. Previous studies have demonstrated that PET nanofibrils could induce flexible transcrystalline layers around them, leading to greatly improvement of the interfacial adhesion between PET nanofibril and polymer matrix [ 51 ].…”

In Situ Nanofibrillar Polypropylene-Based Composite Microcellular Foams with Enhanced Mechanical and Flame-Retardant Performances

“…Compared with PP/PET(F) composite, the average diameter of PET fibrils remains at 270 nm, but the proportion of the fibrils distributed in 100~250 μm is increased. These results indicate that the incorporation of PDPP particles has no negative effect on the formation of PET nanofibrils and can generally effectively improve the microcellular foaming properties [ 35 ].…”

“…Pure PP exhibits huge, regular-like polygonal shapes with closed cell structures. The introduction of spherical PET domains endows a reduction in cell size, an increase in cell density, and an improvement in cell homogeneity due to the heterogeneous cell nucleation effect [ 35 ]. After PET domains transformed from spherical droplets to fibrils, the cell size became much smaller and cell density increased dramatically.…”

Characteristics of Composite Materials of the Type: TPU/PP/BaTiO3 Powder for 3D Printing Applications

“…This significant interest is due to the remarkable properties of polymeric nanocomposite materials compared to the current polymers and conventional macro- or micro-composites [ 1 ]. The properties of polymeric nanocomposites (much improved over those conventional materials) refer to elasticity [ 2 , 3 , 4 , 5 , 6 , 7 ], mechanical resistance, thermal resistance [ 8 ], low gas permeability [ 9 , 10 , 11 , 12 , 13 , 14 ], flammability [ 15 , 16 , 17 , 18 , 19 ], and a high degree of degradability [ 20 ].…”