Effects of fungal decay on properties of mechanical,chemical, and water absorption of wood plastic composites

This study investigated the associations between wood species and fungal resistance, as well as the effects of fungal decay on the properties of mechanical, chemical, and water absorption of wood polypropylene composites (WPCs) filled with white poplar, moso-bamboo, Chinese fir, Ramin, white pine, and rubber wood. Experimental results on weight losses and surface morphology both showed that fungal resistance of WPCs varied significantly with wood fiber species. Chinese fir and rubber wood filled composites separately presented the most and least durability against Coriolus versicolor (white rot) and Poria placenta (brown rot). In addition, fungal decay produced great differences in the properties of mechanical, chemical, and water absorptions between non-decayed and decayed composites. The decayed composites showed lower MOR, tensile strength, and impact strength, as well as higher MOE and water absorptions compared with non-decayed samples. These findings suggest that fungal decay could bring out dramatic influences on various properties of WPCs.     

Mechanical and thermal properties of wood‐plastic composites reinforced with hexagonal boron nitride

Mechanical, thermal, and morphological properties of injection molded wood‐plastic composites (WPCs) prepared from poplar wood flour (50 wt%), thermoplastics (high density polyethlyne or polypropylene) with coupling agent (3 wt%), and hexagonal boron nitride (h‐BN) (2, 4, or 6 wt%) nanopowder were investigated. The flexural and tensile properties of WPCs significantly improved with increasing content of the h‐BN. Unlike the tensile and flexural properties, the notched izod impact strength of WPCs decreased with increasing content of h‐BN but it was higher than that of WPCs without the h‐BN. The WPCs containing h‐BN were stiffer than those without h‐BN. The tensile elongation at break values of WPCs increased with the addition of h‐BN. The differential scanning calorimetry (DSC) analysis showed that the crystallinity, melting enthalpy, and crystallization enthalpy of the WPCs increased with increasing content of the h‐BN. The increase in the crystallization peak temperature of WPCs indicated that h‐BN was the efficient nucleating agent for the thermoplastic composites to increase the crystallization rate. POLYM. COMPOS., 35:194–200, 2014. © 2013 Society of Plastics Engineers     

Effect of accelerated weathering on discoloration and roughness of finished ash wood surfaces in comparison with red oak and hard maple

This study investigated the discoloration and roughening of finish and unfinished ash (Fraxinus americana), red oak (Quercus rubra), and hard maple (Acer nigrum) wood surfaces exposed to artificial weathering, with the aim of assessing the potential for ash wood for interior and exterior applications. Ash wood surfaces were treated with several coats of satin and high gloss polyurethane finishes in order to evaluate their potential for value added products from waste ash wood generated from an exotic insect (emerald ash borer) infestation. Red oak and red maple wood specimens were included in the study for comparison purposes. The weathering experiment was performed by cycles of UV light irradiation with and without water. Surface discoloration was measured according to ISO 2470 standard with a micro flash reflectometer in the CIELAB system. The surface roughness was measured with a surface profilometer and a roughening profile developed for each weathered surface. Results obtained showed that ash wood exposed to a combination of UV light and water spray had a color change pattern very similar to that of maple, and both species had a faster and higher levels of discoloration compared to red oak. However, when exposed to continuous UV radiation without water, ash had a higher level of discoloration than maple and red oak. Evaluation of changes in the roughness showed that maple had the lowest roughness after weathering, but finished ash surfaces also showed roughness characteristics similar to that of maple after 450 h exposure.     

Shear strength and water resistance of modified soy protein adhesives

Soy protein polymers recently have been considered as alternatives to petroleum polymers to ease environmental pollution. The use of soy proteins as adhesives for plywood has been limited because of their low water resistance. The objective of this research was to test the water resistance of adhesives containing modified soy proteins in walnut, maple, poplar, and pine plywood applications. Gluing strength and water resistance of wood were tested by using two ASTM standard methods. Glues with modified soy proteins had stronger bond strength than those containing unmodified soy proteins. Plywood made with glue containing urea-modified proteins had higher water resistance than those bonded with glues containing alkali-modified and heat-treated proteins. After three 48-h cycles of water-soaking, followed by 48 h of air-drying, no delamination was observed for either walnut or pine specimens glued with the urea-modified soy protein adhesives. Gluing strength for wood species with smooth and oriented surface structure was lower than for those with rough, randomly oriented, surface structures. Wood species with greater expansion of dimensions during water-soaking had a higher delamination rate than those showing less expansion.     

Effects of Defibration Conditions on Mechanical and Physical Properties of Wood Fiber/High-Density Polyethylene Composites

Defibration conditions influence wood fiber characteristics and thereby properties of fiber-based materials. In this study, the effects of several defibration conditions on mechanical and physical properties of fiber-based wood-plastic composites (WPCs) are illustrated. Various WPCs were tested containing different thermo-mechanical pulps (TMPs) or groundwood pulp (GWP), whereby material composition (50 wt% wood fibers, 47 wt% polymer, 3 wt% coupling agent) and the production process (internal mixer, injection molder) were kept consistent. The data from the experiment revealed that differing defibration conditions led to statistically significant differences in the tested flexural, tensile, and impact properties as well as in the water absorption of WPC. Overall, the GWP and the TMP which was produced under the mildest defibration conditions performed best in fiber-based WPCs. Therefore, grinders and refiners may be equally suitable to produce pulp for WPC usage. As a side-effect within this study, the reinforcing effect of fiber application on flexural and tensile properties was on an extraordinarily high level.     

Urea-Modified Soy Globulin Proteins (7S and 11S): Effect of Wettability and Secondary Structure on Adhesion

This investigation characterized wettability and adhesive properties of the major soy protein components conglycinin (7S) and glycinin (11S) after urea modification. Modified 7S and 11S soy proteins were evaluated for gluing strength with pine, walnut, and cherry plywood and for wettability using a bubble shape analyzer. The results showed that different adhesives had varying degrees of wettability on the wood specimens. The 7S soy protein modified with urea had better wettability on cherry and walnut. The 11S soy protein modified with 1M urea had better wettability on pine. The 1M urea modification gave 11S soy protein the greatest bonding strength in all the wood specimens. The 3M urea modification gave 7S soy protein stronger adhesion on cherry and walnut than did 11S protein; but with pine, 11S soy protein had greater adhesion strength than 7S soy protein. Measurement of protein secondary structures indicated that the β-sheet played an important role in the adhesion strength of 3M urea-modified soy protein in cherry and walnut, while random coil was the major factor reducing adhesion strength of 7S soy protein modified with 1M urea.     

Thermal Behavior of Deteriorated Wood Waste

Abstract

This paper investigates the thermal behavior of woody biomass waste—demolition wood of Japanese cedar (Cryptomeria japonica) and insect-attacked forest residue of Japanese red pine (Pinus densiflora)—using proximate analyses, thermogravimetry (TG), and differential thermal analysis (DTA), with comparison to virgin wood. For the pine samples, there was no significant difference in thermal behavior or elemental composition between the virgin pine and pine that had been damaged by insects, indicating that insect-damaged pine received here can be treated as virgin pine in terms of energy utilization. The cedar demolition wood used here was partly degraded by termites or fungi. Its degraded part had a lower weight loss rate under nitrogen and a broader exothermic peak in the char combustion stage under air than cedar virgin wood. The changes in the relative levels of the chemical components and the resultant chemical changes that occur upon fungal degradation might complicate char formation.     

Effect of Coupling Agent Concentration,Fiber Content,and Size on Mechanical Properties of Wood/HDPE Composites

In this study, the influence of coupling agent concentration (0 and 3 wt%), wood fiber content (50, 60, 70, and 80 wt%), and size (40–60, 80–100, and 160–180 mesh) on the mechanical properties of wood/high-density-polyethylene (HDPE) composites (WPCs) was investigated. WPC samples were prepared with poplar wood-flour, HDPE, and polyethylene maleic anhydride copolymer (MAPE) as coupling agent. It was found that the tensile properties and the flexural properties of the composites were improved by the addition of 3 wt% MAPE, and the improved interfacial adhesion was well confirmed by SEM micrographs. It was also observed that the best mechanical properties of wood/HDPE composites can be reached with larger particle size in the range studied, while too-small particle size was adverse for the mechanical properties of wood/HDPE composites. Moreover, the tensile modulus, tensile strength, and flexural strength of WPCs decreased with the increase in fiber content from 50 to 80 wt%; the flexural modulus of WPCs increased with the increase in fiber content from 50 to 70 wt% and then decreased as the fiber content reached 80 wt%. The variances in property performance are helpful for the end-user to choose an appropriate coupling agent (MAPE) concentration, wood fiber content, and particle size based on performance needs and cost considerations.     

Wood flour/polylactide biocomposites toughened with polyhydroxyalkanoates

Polylactide (PLA)‐based wood–plastic composites (WPCs) were successfully manufactured by extrusion blending followed by injection molding. The effects of polyhydroxyanoates (PHAs) on the mechanical and thermal properties and the morphologies of the PLA‐based WPCs were investigated with mechanical testing, thermal analysis, and scanning electronic microscopy (SEM). The inclusion of PHAs in the PLA‐based WPCs produced an increase in the impact resistance and a decrease in the tensile strength. The brittle–ductile transition of the impact strength for the PLA‐based WPCs toughened with PHAs was confirmed when the wood flour content was between 15 and 35 wt %. SEM images showed that the fracture surfaces of the PLA‐based WPCs toughened with PHAs were rougher than that of their nontoughened counterparts. The ternary PLA‐based WPCs exhibited ductile fracture during mechanical testing. Differential scanning calorimetry (DSC) showed that addition of PHAs into the composites caused deviations of the cold crystallization temperature and melting temperature of PLA. Thermogravimetric analysis indicated that the PHAs reduced the thermal stability of the PLA‐based WPCs. PHAs can be a green toughening agent for PLA‐based WPCs. The specific properties evidenced by the biocomposites may hint at their potential application, for example, in the automotive industry and civil engineering. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The effects of clay dispersion on the mechanical,physical, and flame‐retarding properties of wood fiber/polyethylene/clay nanocomposites

In this study, nanosized clay particles were introduced into wood fiber/plastic composites (WPCs) to improve their mechanical properties and flame retardancy, which are especially important in various automotive and construction applications. A high degree of exfoliation for nanoclay in the wood fiber/high density polyethylene (HDPE) composites was successfully achieved with the aid of maleated HDPE (PE‐g‐MAn), through a melt blending masterbatch process. The structures and morphologies of the composites were determined using X‐ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. This article presents the effects of clay content and degree of clay dispersion on the mechanical and physical properties and flame retardancy of wood fiber/HDPE composites that contained a small amount of clay, in the range of 3–5 wt %. We concluded that achieving a higher degree of dispersion for the nanosized clay particles is critical to enhance the mechanical properties and the flame retardancy of WPCs when small amounts of clay are used. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Hygrothermal aging properties of wood plastic composites made of recycled high density polypropylene as affected by inorganic pigments

The objective of this study is to investigate the hygrothermal aging properties of wood plastic composites (WPCs) made of a recycled high density polyethylene (HDPE) highly filled with wood waste, inorganic filler and pigments with a resin/filler ratio of 27/73. Hygrothermal ageing test of the prepared WPCs with three different colors (original, red, and chocolate) was carried out by immersing specimens in distilled water at 45°C for 70 days. The hygrothermal ageing properties including water absorption, moisture diffusion coefficient, surface color change, and flexural properties of the WPCs were investigated. It was found that pigment colored WPCs have better hygrothermal aging properties including lower water absorption, less total color changes, and higher mechanical property retention rate after 70 days hygrothermal aging test. POLYM. ENG. SCI., 55:2127–2132, 2015. © 2015 Society of Plastics Engineers     

A comparative study of using allyl alcohol based copolymers in the preservation of wood: Oak vs. cedar

Wood is an important raw material that is cheap and easily worked. However, wooden objects are subject to environmental attack and mechanical shocks. In this study, our aim is to preserve wooden objects against envrironmental deterioration and mechanical shocks on to consolidate objects already degraded. Allyl alcohol (AA), acrylonitrile (AN), methyl methacrylate (MMA) and AA/AN, AA/MMA monomer mixtures were impregnated into oak and cedar. Polymerization was accomplished by gamma irradiation. The mechanical properties and the dimensional stability of the wood‐copolymer composites were determined. The presence of polymer and copolymer in the wood increased the mechanical durability of the wood. The results of the hardness tests and the compressive strengths determined in parallel and perpendicular directions to the fibers revealed that P(AA/MMA), P(AA/AN) copolymers are effective in increasing the mechanical durability of pristine‐oak and cedar woods. Similar results were also obtained from hardness tests. The decrease in the mechanical durability of pristine‐oak and cedar woods after aging for 28 days is slight. The water uptake capacity of wood + copolymer composites was observed to decrease by more than 50% compared with the original samples. In the cedar wood, where the density is low and the quantity of copolymer is high, this decrease ranged from 100% to 50%.     

Mechanical,thermal and morphological properties of heat-treated wood-polypropylene composites and comparison of the composites with PROMETHEE method

ABSTRACT

The aim of the paper was to determine the mechanical, thermal, and morphological properties of heat-treated wood-polypropylene polymer composites (WPCs) and to select the composites having the optimum properties with the PROMETHEE method. In this study, polypropylene (PP) as a matrix, wood thermally treated at 180°C and 220°C as reinforcement filler were examined for preparing composites. The PP composites were compounded using a twin-screw extruder and test specimens were prepared by compression moulding. According to the test results, the thermal and mechanical properties of the WPCs generally increased with the addition of heat-treated wood fillers. The SEM images showed that the wood fillers dispersed better in the PP matrix as the particle size decreased from 40 mesh to 100 mesh. The WPCs having the optimum mechanical and thermal properties were determined for 40 mesh heat-treated wood at 220°C and 20?wt-% loadings with PROMETHEE method.     

Waste pine cones as a source of reinforcing fillers for thermoplastic composites

In this study, we evaluated some physical and mechanical properties of polypropylene (PP) composites reinforced with pine‐cone flour and wood flour. Five types of wood–plastic composites (WPCs) were prepared from mixtures of cone flour, wood flour, PP, and a coupling agent. The water resistance and flexural properties of the composites were negatively affected by an increase in cone‐flour content. Extractives in the cone flour had a significant effect on the flexural properties of the WPCs. However, the flexural properties and water resistance of the WPC samples were not significantly affected by the addition of 10 wt % of the cone flour when compared to the WPC samples made from wood flour. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Chemical ecology of the luna moth

The effects of food plant on larval performance and midgut detoxification enzymes were investigated in larvae of the luna moth,Actias luna. Neonate larvae were fed leaves of black cherry, cottonwood, quaking aspen, white willow, red oak, white oak, tulip tree, paper birch, black walnut, butternut, or shagbark hickory. First instar survival, larval duration, and pupal weights were monitored as indices of food quality. Midgut enzyme preparations from fifth instars were assayed for -glucosidase, quinone reductase, polysubstrate monooxygenase, esterase, and glutathione transferase activities. Larval survival on seven of the 11 plant species, including several recorded host plants, was extremely poor. Larvae performed well, and quite similarly, on birch, walnut, butternut, and hickory. Activities of all enzyme systems except -glucosidase were significantly influenced by larval host plant. Of the systems assayed, quinone reductase and glutathione transferase activities were especially high. Comparisons of these values with published values for other Lepidoptera support the hypothesis that these enzyme systems are involved in conferring tolerance to juglone and related quinones occurring in members of the plant family Juglandaceae. Results suggest that host plant utilization by luna is more specialized at the individual or population level than at the species level and that biochemical detoxification systems may play a role in such specialization.     

Mechanical properties of composites from sawdust and recycled plastics

Mechanical properties of wood plastic composites (WPCs) manufactured from sawdust and virgin and/or recycled plastics, namely high density polyethylene (HDPE) and polypropylene (PP), were studied. Sawdust was prepared from beech industrial sawdust by screening to the desired particle size and was mixed with different virgin or recycled plastics at 50% by weight fiber loading. The mixed materials were then compression molded into panels. Flexural and tensile properties and impact strength of the manufactured WPCs were determined according to the relevant standard specifications. Although composites containing PP (virgin and recycled) exhibited higher stiffness and strength than those made from HDPE (virgin and recycled), they had lower unnotched impact strengths. Mechanical properties of specimens containing recycled plastics (HDPE and PP) were statistically similar and comparable to those of composites made from virgin plastics. This was considered as a possibility to expand the use of recycled plastics in the manufacture of WPCs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3641–3645, 2006     

加工助剂TKM80在木塑复合材料中的应用研究

研究了加工助剂60NSF,TKM80,WB16对聚丙烯(PP)基木塑复合材料机械性能和流变性能的影响。结果表明,60NSF,TKM80,WB16这3种助剂中TKM80对木塑复合材料机械性能的提高最大,与未加TKM80比较,当TKM80用量为7.5份时,木塑复合材料的拉伸强度提高20.9%,冲击强度提高55.6%,加工流变性得到很大的提高;从试样的冲击断裂面的扫描电镜照片,可以看出TKM80能够提高木粉在PP基体中的分散性,并改善PP与木粉之间的相容性。     

Effects of vinyltrimethoxy silane on thermal properties and dynamic mechanical properties of polypropylene–wood flour composites

The viability of vinyltrimethoxy silane was investigated as a coupling agent for the manufacture of wood–plastic composites (WPC). The effect of silane pretreatment of the wood flour on the thermal and the dynamic mechanical properties and thermal degradation properties of the composites were studied. Moreover, the effect of organosilane on the properties of composites was compared with the effect of maleated polypropylene (MAPP). DSC studies indicated that the wood flour acts as a PP-nucleating agent, increasing the PP crystallization rate. In general, pretreatment with small amounts of silane improved this behavior in all the WPCs studied. Thermal degradation studies of the WPCs indicated that the presence of wood flour delayed degradation of the PP. Silane pretreatment of the wood flour augmented this effect, though without significantly affecting cellulose degradation. Studies of dynamic mechanical properties revealed that the wood flour (at up to 30 wt %) increased storage modulus values with respect to those of pure PP; in WPCs with a higher wood flour amount, there was no additional increase in storage modulus. Pretreatment of the wood flour with silane basically had no effect on the dynamic mechanical properties of the WPC. These results show that with small amounts of vinyltrimethoxy silane similar properties to the MAPP are reached. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Phenolic Compounds in Red Oak and Sugar Maple Leaves Have Prooxidant Activities in the Midgut Fluids of <Emphasis Type="Italic">Malacosoma disstria</Emphasis> and <Emphasis Type="Italic">Orgyia leucostigma</Emphasis> Caterpillars

Phenolic compounds are generally believed to be key components of the oxidative defenses of plants against pathogens and herbivores. However, phenolic oxidation in the gut fluids of insect herbivores has rarely been demonstrated, and some phenolics could act as antioxidants rather than prooxidants. We compared the overall activities of the phenolic compounds in red oak (Quercus rubra) and sugar maple (Acer saccharum) leaves in the midgut fluids of two caterpillar species, Malacosoma disstria (phenolic-sensitive) and Orgyia leucostigma (phenolic-tolerant). Three hypotheses were examined: (1) ingested sugar maple leaves produce higher levels of semiquinone radicals (from phenolic oxidation) in caterpillar midgut fluids than do red oak leaves; (2) O. leucostigma maintains lower levels of phenolic oxidation in its midgut fluids than does M. disstria; and (3) phenolic compounds in tree leaves have overall prooxidant activities in the midgut fluids of caterpillars. Sugar maple leaves had significantly lower ascorbate:phenolic ratios than did red oak leaves, suggesting that phenolics in maple would oxidize more readily than those in oak. As expected, semiquinone radicals were at higher steady-state levels in the midgut fluids of both caterpillar species when they fed on sugar maple than on red oak, consistent with the first hypothesis. Higher semiquinone radical levels were also found in M. disstria than in O. leucostigma, consistent with the second hypothesis. Finally, semiquinone radical formation was positively associated with two markers of oxidation (protein carbonyls and total peroxides). These results suggest that the complex mixtures of phenolics in red oak and sugar maple leaves have overall prooxidant activities in the midgut fluids of M. disstria and O. leucostigma caterpillars. We conclude that the oxidative defenses of trees vary substantially between species, with those in sugar maple leaves being especially active, even in phenolic-tolerant herbivore species.     

Mechanical and thermo-chemical properties of wood-flour/polypropylene blends

The main objective of this research was to study the potential of waste polypropylene and waste wood for making wood plastic composites (WPCs). The effects of nanoclay (NC), microcrystalline cellulose (MCC), and coupling agent (MAPP) on the mechanical and thermal properties were also studied. The results showed that mechanical properties of the composites made with MCC were significantly superior to those of unfilled. Addition of MAPP could enhance the mechanical and thermal properties of the blends, due to the improvement of interface bond between the filler and matrix. The significant improvements in tensile properties of the blends composites made with MAPP and NC were further supported by SEM micrographs. The thermogravimetric analysis indicated that the addition of 5 wt% MAPP and 3 wt% NC significantly increased the thermal stability of the blends compared to the pure PP. MCC could not improve the thermal stability. The experimental results demonstrated that the waste materials used are promising alternative raw materials for making low cost WPCs.