Ruijun Gu

Characteristics of wood–plastic composites reinforced with organo-nanoclays

Nanomer and Cloisite are the popular commercial nanoclays (NC) available in the market. The mechanical properties of wood—plastic composite (WPC) based on linear low density polyethylene with or without wood fiber are compared for different added nanoclays. In addition, the moisture uptakes at 23°C and 45% RH and water uptake/loss after immersion in water are evaluated. I.34TCN type nanoclay as well as Cloisite Na+ lead to composites with superior mechanical properties and better water resistance behaviors compared to the other kinds of nanoclays. It should be noted that the discoloration occurs in WPC reinforced with unmodified NC.

Effects of Wood Fiber and Microclay on the Performance of Soy Based Polyurethane Foams

Various polyurethane (PU) foams were prepared by in situ reaction of isocyanate and soy-based polyol. The effects of wood fiber and microclay on the foam morphologies, mechanical properties and thermal behaviors of PU foams were investigated. NCO index had fundamental impacts on the influences of wood fiber and microclay on the performance of PU foams. The reinforcement behavior of flexible foams was different to that of both semi-rigid and rigid foams. Both fiber and microclay improved the compressive strength at a high NCO index of 140–250, and contributed to relative high decomposition temperatures. Unlike the compressive strength, the tensile strength was decreased due to the amount of hard polyurea formation from secondary reactions at the highest NCO level. In addition, wood fiber had different reinforcement mechanism from microclay. Wood fiber desired to form chemical bonds during foaming while microclay had potential to form physical insertions. This difference was expressed by the change of their thermal degradation temperature.

Mechanical Properties of PP Composites Reinforced with BCTMP Aspen Fiber

In this work we investigated the effect of incorporating wood fibers (bleached chemi-thermo-mechanical pulp of aspen, BCTMP) on the properties of a hybrid composite material made from maleated polypropylene (MAPP) and Nanoclay (NC) or not. The effects of morphological structure of polypropylene (PP) and the molecular weight (Mw) and maleic anhydride graft level (MA%) of MAPP were also performed to evaluate the improvements of each independent factor (MAPP, Dicumyl peroxide-DCP and NC). In our case, the size of wood fiber had little effect on the impact and tensile strength. High Mw and low MA% MAPP contributes homo-PP hybrids with better performance, either impact or tensile. In addition, wood fiber gives the hybrids, based on both homo-polypropylene (homo-PP) and co-polypropylene (co-PP), without the presence of coupling agent, similar behaviors of impact and tensile strengths. However, the impact and tensile strength of the hybrids mentioned above are improved in the presence of coupling agent. NC weakens the impact strength of composites with/without the reinforcement of wood fiber, coupling agent, and DCP. It shows different behaviors of tensile with improvement of tensile for hybrids with wood fiber, coupling agent, and DCP but impartation for nanocomposites without additives. Moreover, the behavior of tensile is in concordance to the changes of elongation as well as toughness. Furthermore, DCP leads to negative effects on the impact and tensile, as well as toughness of the hybrids when fiber is present, but exhibits better resistance deformation extension which is in concordance with the increase of modulus. In addition, there is a little increase in plasticity.

Effect of variables on the mechanical properties and maximization of polyethylene-aspen composites by Statistical Experimental Design

Systemic studies of the effects of the concentrations of maleated polyethylene (MAPE) loading, the content and addition sequence of dicumyl peroxide, the content and type of nanoclay (NC), and aspen fiber loading on the mechanical properties of PE—aspen composites were undertaken with the objective to increase the impact strength as well as the tensile properties. In this article, the formation of an optimal compatibilizing system for the hybrid composite PE—aspen—NC by combining basic principles for compatibilization was investigated. Statistical approach experimentation using Statgraphics Centurion® with the objective to maximize both the tensile strength as well as the impact properties of natural fiber and nanoclay filled PE was applied to reach values well above that of virgin PE.

Effect of Independent Variables on Mechanical Properties and Maximization of Aspen—Polypropylene Composites

Study on the effect of concentration of maleated polypropylene (MAPP), dicumyl peroxide (DCP), nanoclay (NC), and aspen fiber loading on the mechanical properties of Aspen—PP composites has been undertaken with the objective to protect or increase the impact strength without losing or weakening the tensile strength. The central composite design of Statgraphic plus is used to determine the optimum concentration of additives and to maximize both the impact as well as tensile strength properties to be superior to that of pure PP. Finally, the material price of PP composites with an optimal composition of filler (aspen fiber and NC), coupling agent (MAPP), and initiator (DCP) is compared to that of pure PP and PP reinforced with glass fibers.

Development and characterization of flexible epoxy foam with reactive liquid rubber and starch

Flexible foams are prepared using carboxyl-terminated butadiene-acrylonitrile rubber (CTBN), diglycidyl ether of bisphenol A epoxy resin and a chemical blowing agent. Central composite design experiments are conducted to investigate the influences of three independent variables, i.e., the ratio of CTBN to epoxy resin, the amounts of curing agent (dicyandiamide) and blowing agent (azodicarbonamide), on the foam performances. After that, epoxy foams are also characterized for mechanical properties to explore the effects of the aforesaid ratio, accelerator type, starch and foaming methods. SEM analysis is used to evaluate the changes in cell characterizations.

Maximization of the Mechanical Properties of Birch-Polypropylene Composites with Additives by Statistical Experimental Design

A systematic study of effects of concentrations of maleated polypropylene (MAPP), dicumyl peroxide (DCP), Nanoblend concentrate (MB1001) and birch fibers on the mechanical properties of birch-polypropylene (PP) composite was undertaken with the objective to protect or increase the impact strength without losing tensile strength. Using Stagraphic Plus, the Central Composite Design made it possible to determine the optimum concentrations of additives and to maximize both the impact as well as tensile properties to reach values well above that of virgin PP.

Effects of Antioxidant and Initiator on the Mechanical Properties of Polypropylene—Aspen Composites

Studies on the effect of blending method, the introduction method of initiator (dicumyl peroxide, DCP), and the blending time with antioxidant (Irganox) added on the mechanical properties of PP—Aspen composites with and without DCP, respectively are undertaken. An optimum blending time for the composite with Irganox is obtained. The optimum content of Irganox as well as pre-mixing and the final-step feeding-method of DCP are compared to that of conventional method of blending in order to achieve the optimum values of impact and tensile strength properties.

Morphological changes and surface reactions of wood fibers in wood composites

This work addressed questions regarding the fate of wood pulp fibers in the composite manufacturing process, for instance whether the processing induced fiber damages, and the improved interfacial adhesion accelerated this function. A number of wood fibers were blended with various maleic anhydride-grafted polymers fully and partially to study their morphological changes. The fractured fibers were separated from wood composites with aromatic hydrocarbons and analyzed using Fiber quality analyses, Scanning electron microscope, Fourier transform infrared analysis and X-ray photoelectron spectroscopy to validate the degree of fiber fractures and the esterification reaction. The fiber damages were related to the maleic anhydride grafting degree, molecular weight and molecular structures of maleated polymers.

The role of nanoclay formations and wood fiber levels on central composite designed polyethylene composites

Central composite designed experiments are conducted to study the independent effects of maleated polyethylene, dicumyl peroxide and nanoclay in the forms of natural (Cloisite® Na+) and masterbatch (Nanoblend™ concentrates MB2001) on the mechanical properties of fiber reinforced PE composites with different fiber levels. The optimum values are predicted on the results of designed experiments and there are linear regressions between fiber content and their mechanical properties. The deposition and formation of nanoclay particles in PE composites are ascertained by scanning electron microscope and transmission electron microscope observations. Both natural nanoclay and MB2001 can be delaminated and even exfoliated in polarized PE matrix. As wood fiber is introduced, natural nanoclay particles (nanoclay-natural) are deposited on fiber surface even loaded in fiber lumens, but the nanoclay particles of MB2001 (nanoclay-concentrate) are mostly dispersed in the matrix. In addition, the different reinforcements between nanoclay-natural and nanoclay-concentrates are also investigated to find out the influence of particle formation on the quality of composite materials.