Luo Luo,Yi Wang,Tianxiang Lv,Shuni Ying,Chunhua Zhou,Xiaodong Zhou,Huihuang Ma
Due to the difficulty in infusing resin into interiors of fiber bundles by prevalent pre-impregnation methods like melt impregnation and the substantial polarity difference between glass fibers (GF) and polypropylene (PP), the application of continuous glass fiber reinforced polypropylene (CGF/PP) composites has been restricted. In this study, a hybrid emulsion is prepared to address the polarity difference through coating process. And further by optimizing coating process parameters, composites glass fibers with excellent performance can be obtained. The study demonstrates that the composite glass fiber with coating amount of 15.34% exhibits good bunching and flexibility. The monofilament tensile strength and interfacial shear strength (IFSS) are increased by 2.53% and 109.74%, respectively compared to the desized glass fiber (GF0). Furthermore, after the hot-pressing process, the composites glass fiber bundles show fully filled gaps and a completely wrapped surface. This study lays the foundation for producing CGF/PP prepreg composites conveniently, efficiently, and commercially.
In this study, aiming at the problem of low strength and high creep caused by medium–low modulus flexible resin based on the formulation design idea of high-molecular-weight epoxy resin (E12)-reinforced flexible epoxy-terminated urethane resin (EUR), a flexible epoxy prepreg resin with high strength and low bending creep was prepared to be suitable for hot melt processing technology. Flexible EUR was synthesized by grafting flexible polyurethane segments onto the epoxy side chain by urethane bonding. By adjusting the ratio of E12 and EUR, the effects of different ratios of the two components on the mechanical properties and viscoelasticity of the resin were systematically studied with dicyandiamide as the latent curing system. Research has found that when the E12 content is between 20%wt and 40%wt, the resin system has the best coating viscosity at 65 °C to 85 °C. The molecular weight and the content of aromatic heterocyclic groups of the resin determine the strength and creep behavior of the resin. When the content of E12 in the system is less than 50%wt, modulus and strength increase linearly, but after more than 50%wt E12 content, the modulus is almost unchanged and the strength begins to decrease. By increasing the content of E12 in the resin, the creep behavior of the resin is greatly reduced. When the content of E12 increases to 50%wt, the bending creep is the lowest.
Zefei Cheng,Huakun Zhao,Lulu Lei,Sixian Yang,Jieyu Chen,Tao Yu,Jinhong Fan
Flax fiber-reinforced thermosetting poly (lactic acid) (PLA) composites, a fully degradable plant fiber-reinforced composites, were prepared by hot-melt pre-impregnation, which consists of two processes, the preparation and curing of the prepreg. Firstly, thermosetting PLA with intrinsic flame-retardancy was synthesized and its molecular structure was verified by Fourier transform infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy. The non-isothermal viscosity of the thermosetting PLA resin system was investigated to determine the film-formation temperature (55°C) and the impregnation temperature (65°C) during the preparation of the prepreg. On this basis, novel flax fiber-reinforced thermosetting PLA prepreg was prepared and its curing kinetics was investigated using differential scanning calorimetry (DSC). A curing simulation model of the prepreg was developed using the finite difference method, which was used to design and optimize the curing cycle of the flax fiber-reinforced thermosetting PLA prepreg. Finally, the flax fiber-reinforced thermosetting PLA composites with different lay-ups were prepared using the optimal curing cycles and their mechanical and flame retardant properties were investigated, with tensile and flexural strengths up to 128 MPa and 98.8 MPa, and flame retardant ratings up to UL-94 V-1. Overall, the results of this study can provide an important basis for expanding the application of flax fiber reinforced thermosetting PLA composites.
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