The Crystallization Behavior And Mechanical Properties Of Sisal/PP Composites

Using nature fibres replace synthetic fibres to produce fibre/thermoplastics composites is practicably rather important for alleviating burden of environment, energy saving, and so on. Sisal fibres for pulp usage and PP are selected to produce sisal/PP composites in this work. Crystallizaiton morphology, non isothermal crystallization kinetics, thermal and mechanical behavior of composites are stuied to probe the relationship between composites mophology and properties of the part. The addition of sisal fibres induced the formation of transcrystalline. Mechanical properties and decomposition temperature have increased at different extents. Main contents are as follows:1) By using hot stage polarzing microscope, we can observe the morphology of sisal fibres and PP at static conditions(constant temperature, variotherm, the different contents sisal fibres). The roughness of sisal fibres and crystallization temperature have some affect to the nucleation of PP on their surface; The addition of sisal fibres increased the crystallization onset temperature and the crystallization rate; the growth rate of transcrystallinity is conformed to unimodal curve at isothermal on different temperatures; at the same temperature, the grow rate of transcrystallinity is independent of cooling rate(20℃/min to 50℃/min), which relate to the setting temperature; but at cooling rate(2.5℃/min to 20℃/min) to room temperature, improving cooling rate, the on set crystallization temperature shift to low temperature; multi-sisal fibres also can induce the formation of transcrystallinity.2) Differential scanning calorimeter(DSC) was used to study non isothermal crystallization of composite materials. As the incresing of the fibre'contents, the peak temperature improved and the time of crystallization shorten, which displayed that sisal fibres have a good crystalline nucleation on PP, but the melt point of PP and the degree of crystallinity has no difference; with the elevating of cooling rate, the peak temperature shift to lower temperature, the extent of crystallization become wide. Jeziorny,Ozawa and Mo models were used to simulate the thermaldynamic mechanism of non isothermal crystallization for sisal fibres/PP composites and PP. which indicate that the crystallization of them include two steps, they are very different in kinetic parameters. The crystallization nucleation and crystal growth have changed. As the cooling rate increased, the paramaters of the two stages become smaller and smaller.3) Using injection molding method to obtain standard testing specimen and then to measure impact properties, tensile properties, bending properties. the result indicates that because of the additive of sisal fibres, the mechanical property of composites have improved with different extent.4) TG was used to measure decomposition temperature of composites contain different contents sisal fibres. With the increasing of sisal fibres contents, huge increase in decomposition temperature is occured, this may be explained as the thermal stress relaxation of the sisal fibres, and the adhesion of sisal and PP.