Lignocellulosic fibers nucleation

Observations of polypropylene crystallization by polarized light microscopy helped to understand phenomena on interphase of polymer-filler. When analyzing the influence of the filler, many researchers noted transciystallization of the polypropylene as a result of high enough nucleation density rai the filler s surface and also in the presence polypropylene fibers. The addition of both mineral substances and natural composites containing lignocellulosic material can induce formation of TCL. 

The effect of flax fiber modification and the effect on the presence of TCL were also studied by Arbelaiz et al. [17]. In his studies, fibers were subjected to maleic anhydride, vinyltrimetoxy silane, and aUcali with addition of MAPP-grafted polypropylene. All applied modifications produced improvement in the thermal stability of lignocellulosic material. Analysis of the crystalline structure showed the increase of crystallinity as a result of fiUer addition. Nucleation density around unmodified fibers was higher than around fibers modified with maleic anhydride. Surfaces of unmodified fibers had the surface active for initialization of transcrystaUization, which, in the case of modified fibers, did not occur. Son et al. [32] explained this phenomenon as... 

The consequence of lignocellulosic material addition, not only in the form of fibers but also in the form of wood flour or wood particles, is the nucleating effect. Numerous reports prove that the presence of wood origin lignocellulosic filler has an influence on crystallization of polymeric matrix. 

Many factors such as adhesion between components, fiber topography, and kinetic parameters of crystallization of semicrystalline matrix have been reported to influence transciystallinity. The transcrystallinity phenomenon in the natural fibers/polypropylene system is affected by the different type of chemical treatment of lignocellulosic materials. Moreover, the ability of natural filler to induce nucleation in polypropylene matrix is also dependent on the kind of chemical modification of surface fibers. Predominant nucleation ability was found for unmodified fibers. However, chemical modification of fiber surface slightly depressed the nucleation of polypropylene matrixes. 

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