Influence of surface morphology of the kraft pulp fibers on the growth of the transcrystalline layer of polypropylene

Abstract

The objective of this study was to evaluate the influence of the wood fiber surface on the crystallization behavior of thermoplastic polymers. Unbleached and bleached kraft pulp fibers were used for this study with 100% polypropylene (PP), 95% PP/5% maleic anhydride polypropylene (MAPP), and 100% MAPP at 150 C. Nuclei were induced at the ends of the fibers and on damaged surfaces while poor crystallization behavior was observed on the fiber surfaces using 100% PP. Enhanced MAPP induced transcrystallization on the wood fiber surfaces; the nucleation density also increased with the addition of MAPP. Oxygen/carbon (O/C) ratios of smooth surfaces, damaged surfaces, and the ends of wood fibers also indicated that the oxidation process of both wood fiber and thermoplastic polymer affected the crystallization process without MAPP addition. It was observed that the MAPP played a role in increasing numbers of nuclei on the linear fiber surface to induce transcrystallization. Dynamic mechanical properties increased 52% with 100% MAPP compared to the use of 100% PP. Therefore, the increased thickness of transcrystalline layer and nucleation density on the surface of wood fiber positively correlated with the dynamic mechanical properties of wood fiber-plastic composites.

Comparative Research between Rhizome and Culm of Phyllostachys pubescens Based on Thermal Analysis

“…Given its best repeatability, the temperature at this point is used to express the heat stability of materials. Research has shown (Lee and Via 2010) that the cumulative weight loss of a pure bamboo powder sample at a final temperature of 700 °C was mainly divided into the following three stages: (1) when the sample reached approximately 260 °C from the normal temperature, the absorbed water of bamboo material was evaporated; (2) from 260 °C to 370 °C, the polymer, mainly hemicellulose, degraded; and (3) from 370 °C to 700 °C, the sample presented partial weight loss (mainly the decomposition of lignin), and pyrolysis was basically stable (Li et al 2006). Table 1 and Fig.…”

Isothermal Crystallization Kinetics of Highly Filled Wood Plastic Composites: Effect of Wood Particles Content and Compatibilizer

“…Spherulitic growth from wood particle surface has been observed. [11,13,14] It was also found that the surface topography of wood particles was the decisive factor on the development of crystallinity. There is a tendency for the nuclei to be initiated from a coarse wood surface, such as the ends of wood fibers and damaged fiber surfaces.…”

“…[9,12,13] A thick transcrystalline layer forming on the wood surface shows a different crystal morphology compared with polyolefin in the matrix. [11,13,14] Wood particles generate a decrease in basal interfacial free energies with respect to pure polyolefin. [3] Lubricants, such as zinc stearate N,N'-ethylene-bisstearamide waxes or polyester-based wax that tend to interfere with wood-PP coupling, are dispersed throughout the transcrystalline region around the particle.…”

“…Regardless of the properties of the wood surface, the incorporation of MAHPP in WPC lead to increased nucleation and decreased the thickness of transcrystalline layer on the wood particles surface. [11,14] Actually, POM is only capable of studying the primary crystallization process of the matrix near single and unattached wood particles. In the actual composites with high wood fraction, distances between wood particles are small and the particles may even aggregate or touch each other.…”

The thermo-oxidative stability and flammability of wood/polypropylene composites

“…According to some authors [25][26][27][28][29][30], chemical modification of the filler leads to a decrease in its nucleation abilities, while according to others [31,32], it leads to an increase in the filler nucleation ability. An important problem in the context of determination of nucleation ability of lignocellulosic fillers can be the polymorphism of cellulose contained in the natural fillers.…”