Abstract
The performances and microstructure of long glass fibre-reinforced polyamide 10T (PA10T/LGF) composites that experienced different ageing temperatures (160 and 200°C) with increasing ageing time are characterized by differential scanning calorimetry (DSC), mechanical analysis, thermogravimetric analysis (TGA) and scanning electron microscopy to probe the correlation between properties of the composites and thermo-oxidative ageing. The DSC results show that PA10T/LGF composites occur on degradation, the fracture of molecular chains and the destruction of crystallization structure, which leads to the crystallization and melting peaks of PA10T/LGF composites to shift to high temperature. On the basis of dynamic mechanical analysis data, the reduction of the interfacial bonding between the glass fibre and PA10T matrix and the motion of molecular chain segments result in the thermo-oxidative ageing of composites. According to the calculation of activation energy (E), thermo-oxidative temperature and ageing time can bring about the decline of the E value, proving the deterioration in performance of PA10T/LGF composites. In view of TGA, the increase in the thermo-oxidative temperature and ageing time promotes the degradation of PA10T/LGF composites. The tensile, flexural and notched impact strengths of PA10T/LGF composites decline with prolonging the ageing temperature and time. The surface of materials produces some microcracks and the cross-section surface of PA10T/LGF composites becomes rougher.
Highlights
Polyamide (PA), an important engineering thermoplastic, is composed of a large quantity of repeated amide groups in the molecular chains
It is of importance that the poorly integrated molecular chain impairs the ability of crystallization of PA10T in the PA10T/long glass fibre (LGF) composites
The LGF-reinforced PA10T composites are prepared by the melt extrusion method, and injection splines are subjected to thermo-oxidative ageing with different exposure times (160 and 200°C)
Summary
Polyamide (PA), an important engineering thermoplastic, is composed of a large quantity of repeated amide groups in the molecular chains. Some researchers [5,6] reported that the physiochemical properties of PA and suitability for specific applications are largely dependent on the structure of the main chains. Because the aromatic rings are grafted to the PA10T molecular backbone, PA10T embraces much better thermal stability than other aliphatic PAs. At the same time, methylene is linked with the PA10T closely and the polymer chain can endow the matrix with melting machinability and flexibility. PA10T can maintain the strength, high rigidity and high size stability, and improve other properties, the PA10T materials can be applied to a wide range of fields. Glass fibre-reinforced PA composites are increasingly important engineering materials due to their high level of mechanical performances and temperature resistance [12,13,14]
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