Rheology and Processing of HDPE/Wood Flour Composites

Abstract

Rheological and mechanical properties of extruded wood plastic composites have been investigated for the purpose of providing a better understanding of processing conditions in profile extrusion for this novel class of thermoplastics composites. The basic formulations prepared for the study were comprised of 60 wt.% HDPE, with or without LLDPE-MAH as coupling agent, compounded with up to 40 wt.% of wood flour and lubricant. Capillary and rotational rheometers were employed to measure the rheological properties of the melt composite. A cooled die at the end of a single screw extruder was used for the extrusion of rectangular profiles having smooth surfaces and edges. Finite element flow simulation was used for the interpretation of the experimental data. Once extrusion steady conditions were achieved in the die, linear output was monitored and profile samples were cut for determination of flexural modulus and strength. The results showed that flexural properties can be influenced by many factors such as, coupling agents, lubricants, processing conditions, die pressure drop and cooling at the die. Linear speed of HDPE wood-plastic profile extrusion and end-use properties are strongly influenced by combination of these factors.

Experimental Study for Extrusion of Polypropylene/Wood Flour Composites

“…Figure 3 shows that die pressure increases with an increase of the wood content in the composite, and it is interesting that an effect of the screw speed on the die pressure weakens with an increase of the wood content. Figure 4 shows that an increase of the wood content reduces the extrudate swell which is consistent with literature data (Maiti and Hassan, 1989;Maiti et al, 2004;Santi et al, 2009).…”

“…Some fundamental studies have been done and summarized by Xiao and Tzoganakis (2002;2003a;2003b;, Li and Wolcott (2005;2006a;2006b), Hristov et al (2006), Vlachopoulos and Hristov (2006), Oksman Niska and Sain (2008), Santi et al (2009), andSolfaghari et al (2010).…”

“…In industrial practice, however, die cooling is frequently used for production of smooth profile surfaces. Surface tearing may be also eliminated at higher shear rates and high loading of wood flour Santi et al, 2009). Recently, Santi et al (2009) modeled the flow of WPC through the die trying to explain these phenomena.…”

Effects of lubricants on the rheological and mechanical properties of wood flour/polypropylene composites

“…One the one hand, the presence of low‐molecular‐weight lubricant decreases the PP intermolecular interaction and increases the ability of relative intermolecular movement. On the other hand, the action of the lubricant improves the dispersion of the WF and slightly decreases the PP crystallinity . Among the lubricated samples, the W40Wax1SA3 showed the smallest reduction in tensile and flexural strength, which were 11.7 and 14.8%, respectively.…”

Natural Fiber Polymer Composites Technology Applied to the Recovery and Protection of Tropical Forests Allied to the Recycling of Industrial and Urban Residues

“…In a previous study, Bettini et al (2008) observed that conventional PPgMA concentrations in PP/sawdust composites, when in the presence of ester-based lubricants, were insufficient to achieve the required mechanical properties. Santi et al (2009) also noticed that the mechanical properties of HDPE/sawdust composites can be reduced when ester-based lubricant and PE-g-MA compatibilizer are used simultaneously. The influence of an ester-based lubricant on the compatibilization effect of PP/sawdust composites, both in the presence and absence of PPgMA, were assessed through the analysis of mechanical and rheological properties (Bettini et al, 2010b).…”