| The effect of Micro-Fibrillated Cellulose (MFC) on the crystallization of polypropylene (PP) was investigated by studying the crystallization kinetics. Basing on the Avrami equation and Hoffman theory, an equation was established. In that equation, three parameters (τ, Tuc and Tlc) were used to describe the crystallization of crystalline polymer. Among them, Tuc and Tlc are closely related to the crystallization temperature;τ is dependent on the rate of crystallization, and the way of working out the value of τ, Tuc and Tlc is given. Furthermore, the problems, "the Avrami parameter n can hardly be an integer" and "the Avrami equation is not suitable to describe non-isothermal crystallization", were discussed, and some explanations were given. Furthermore, τ, Tuc, Tlc and the Avrami equation were successfully used to predict the processes of isothermal and non-isothermal crystallization of PP, PE and PEO.The crystallization of PP-MFC composite was studied using this method, and PP-MFC and PP-WBG (WBG-Ⅲ is a typical nucleating agent) were compared. Basing on the value of τ, Tuc and Tlc, it’s highly believed that MFC and WBG have totally different effect on PP. Although PP crystal will grow around MFC visibly, the inducement is not the structure of the surface of MFC. Instead, it is more probably caused by stress. From the result the rate of crystallization will increase with the increase of MFC content.According to tensile test, when 5% MFC was added to PP, elasticity modulus was enhanced while breaking strength and elongation at break reduced. Of PP-MFC film, the breaking strength reduced from 31.8 MPa to 29.2 MPa. More obviously, the elongation at break of PP-MFC reduced from 742% to 40%. To enhance the elongation at break of PP-MFC,3% PPR polypropylene random copolymer) was added to PP-MFC, and the elongation at break of the film increased from 40% to 779%. On PP-MFC plate, when 3% PPR was added to PP-MFC plate, the elongation at break increased from 550% to 691%. |
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