Interface Of Fiber Reinforced Thermoplastic Polyurethane Composites

Composite materials usually possess a much more excellent performance thaneach component. Fiber reinforced thermoplastic composite materials are distinguishedbecause of easy producing, good processing and recycling compared withthermosetting composites. In recent years, there are a lot of researches focus on thefiber reinforced composites thatareused in the military, industrial and civil fieldsgradually.Through controllingthe interface between the two phases in compositematerials, we canget specific structure and adhesion force. It is of vital significanceforthe preparation of high performance composite materials.This paper selected aramid fiber and carbon fibers as the reinforcing fibers, TPUas the matrix.The interface properties of the composite materials have beencharacterizedby TGA, DSC, POM, SEM, XPS and so on. The isothermalcrystallization kinetics of composite materials, non-isothermal crystallizationconditions,interfacial strength control conditions and phase separation controlconditions etc have been tested. Some preliminary conclusions are summarized asfollowings.(1) With the increase of crystallization temperature, the mismatch of thecarbon fiber thermal conductivitydecreases, it drastically recedes the promoting effectof the material crystallization efficiency. The carbon fiber pre-treated with nitric acidhas the certain promoter action on the material crystallization at high temperaturebecause of the larger surface activity than the first one. Between the aramid fiber andmatrix,there is a strong bond which can significantly improve the efficiency of thematerial crystallization, and it is not affected by the temperature.(2) Under thenon-isothermal condition, the fiber reinforced TPU resin matrix composites show aphase separation induced by crystallization.Along with the phase separation, there isanother effect called crystallization nucleation induced by concentration fluctuations.In composite materials, the reinforcedfibers can induce crystallization on itself. Thethree effects lead to crystals of two sizes generated in the system. They also changethe microscopic state of aggregation and phase structure of the system.(3) The microphase separation degree and the crystallization degree of TPU resin matrix compositescan be controlled by changing the treatment.(4) The conditions of the fiber surface is the key factors to decide the interface shear strength of the fiber reinforced compositematerial. In addition, the crystal propertyof composite material has a closerelationshipwith thefiber surface state, processing conditions and micro phaseseparation degree of TPU resin.The content of this paper has the theoretical significance for understanding thechange rule of thefiber reinforced thermoplastic polyurethane composites interface. Itcan provide the basic theory for interfacial crystallization, thermal and mechanicalproperties of the composites. It’s of guiding significance on the performanceimprovement and the new polyurethane composite materials’ development.