Wood particle/high‐density polyethylene composites: Thermal sensitivity and nucleating ability of wood particles

Abstract

ABSTRACT:The thermal sensitivity, nucleating ability, and nonisothermal crystallization of high-density polyethylene (HDPE) with different wood fillers during wood/HDPE melt processing were investigated with thermogravimetric analysis and differential scanning calorimetry. The results showed that the wood degraded at a lower temperature than HDPE. The thermal decomposition behavior was similar across wood species. The most remarkable dissimilarities were observed between wood and bark in the decomposition rate around a processing temperature of 300 C and in the peak temperature location for cellulose degradation. The higher degradation rate for bark was explained by the devolatilization of extractives and the degradation of lignin, which were present in higher amounts in pine bark. The nucleating ability for various wood fillers was evaluated with the crystalline weight fraction, crystal conversion, crystallization halftime, and crystallization temperature of the HDPE matrix. The nucleation activity improved with the addition of wood particles to the HDPE matrix. However, no effect of wood species on the crystal conversion was found. For composites based on semicrystalline matrix polymers, the crystal conversion may be an important factor in determining the stiffness and fracture behavior.

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

“…It has been widely accepted that wood particles in contact with a polyolefin melt favors heterogeneous nucleation and accelerates the crystallization rate. [8][9][10][11] The induction time of polyolefin matrix in the isothermal crystallization of wood particles depends on the surface roughness, rather than the various wood species, which agree well with polarized optical microscopy (POM) findings. [9,12,13] A thick transcrystalline layer forming on the wood surface shows a different crystal morphology compared with polyolefin in the matrix.…”

“…[8][9][10][11] The induction time of polyolefin matrix in the isothermal crystallization of wood particles depends on the surface roughness, rather than the various wood species, which agree well with polarized optical microscopy (POM) findings. [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.…”

Enhanced antioxidant activity of polyolefin films integrated with grape tannins

“…The emergence of the second peak suggests the rearrangement of shorter polymer chains in these HDPE blends, where GT at a higher concentration might have acted as a nucleating agent. The increase in crystallinity resulting from the addition of wood particles and an accompanying increase in nucleation in the HDPE was seen by Bouafif et al Nucleation can also lead to the formation of small areas of crystallinity, which melt faster, thereby producing a distinct peak in the thermal trace. Alternatively, shifting of the melting peak towards a higher temperature is indicative of the formation of more stable polymer molecules, and suggests a possible increase in the main crystalline sections.…”

Rheological and mechanical characterization of polypropylene-based wood plastic composites

“…Neglecting lignin degradation, thermal degradation of natural fibers occurs as a two‐stage process at two different temperatures: hemicellulose degradation starts at 195°C while cellulose at 255°C, as reported by Bouafif et al . The temperature of hemicellulose degradation onset is commonly assumed as the upper limit for WPC processing.…”