Preliminary study of viscoelastic properties of MAPP-modified wood flour/polypropylene composites

Viscoelastic properties of maleated polypropylene (MAPP)-modified wood flour/polypropylene composites (WPC) were investigated by both a compression stress relaxation method and dynamic mechanical analyses (DMA). Three wood to polymer ratios (40:60, 60:40, and 80:20) and five MAPP loading levels (0, 1, 2, 4 and 8%) were used to study their effects on the viscoelastic properties of MAPP-WPC. The results show that: 1) higher wood to polymer ratio corresponds to higher stress relaxation levels for unmodified WPC. The modification with MAPP has an obvious effect on the stress relaxation of MAPP-WPC at higher wood to polymer ratios (60:40 and 80:20), but almost no effect at the 40:60 wood to polymer ratio. The optimal MAPP loading level for the wood to polymer ratio of 60:40 appears at 1%; 2) the storage modulus reaches its maximum at a MAPP loading level of 1% for wood to polymer ratios of 40:60 and 60:40, while for the 80:20 wood to polymer ratio, a higher storage modulus is observed at higher MAPP loading levels, which is quite consistent with the stress relaxation results. The results suggested that a suitable loading level of MAPP has a positive effect on the viscoelastic properties of WPC at higher wood to polymer ratios. Excessive MAPP loading would have resulted in adverse effects.     

Improvement in compatibility and mechanical properties of modified wood fiber/polypropylene composites

To improve the interfacial compatibility between wood fibers and polypropylene and the toughness of wood-fiber/polypropylene composites, maleic anhydride grafted polypropylene (PP-g-MAH) and maleic anhydride grafted styrene-ethylene-butadiene-styrene copolymers (SEBS-g-MAH) were used as modifiers. Mechanical properties of wood-fiber/polypropylene (WF/PP) composites were improved when PP-g-MAH or SEBS-g-MAH was added. When either of these copolymers was added, the composites had better interfacial compatibility than the unmodified composite. This was verified by scanning electron microscope (SEM) observations and dynamic mechanical analysis (DMA). The mechanical properties of the composites were significantly improved because of the good interfacial bonding between wood fibers and polypropylene when PP-g-MAH and SEBS-g-MAH were added. __________ Translated from Journal of Beijing Forestry University, 2007, 29(2): 133–137 [译自: 北京林业大学学报]     

Dynamic-mechanical analysis and SEM morphology of wood flour/polypropylene composites

Introduction It is well known that over the past few decades, polymers have replaced many conventional materials, such as metal and wood in many applications. This is due to the advantages of polymers over conventional materials (Maurizio et al. 1998; Adr…     

Properties of PEG/thermally modified wood flour/polypropylene (PP) composites

In order to improve the dimensional stability of wood-polymer composites, wood flour pre-treated by polyethylene glyco1 (PEG) at two different concentrations and then thermally treated at 140°C, was used as raw material to produce wood flour/polypropylene (PP) composites at a wood content of 40%. The structure of modified wood flour was analyzed with a scanning electron microscope (SEM) and its effect on the physical and mechanical properties of wood flour/PP composites was evaluated. The SEM results indicated the "bulking" effect of PEG on wood flour, which resulted in reduced water uptake. The combination of PEG and heat treatment further improved the moisture resistance of the composites. However, PEG modification had a negative effect on the flexural modulus of rupture (MOR) and the modulus of elasticity (MOE); whereas heat treatment partly compensated for this reduction. For dynamic mechanical properties, PEG treatment decreased the storage modulus (E′). However, the heat treatment resulted in an increase of E′ of the wood flour/PP composites, with the temperature of loss factor peaks shifting to a higher temperature.     

Toughening wood/polypropylene composites with polyethylene octene elastomer （POE）

Introduction Wood-Plastic Composite (WPC), due to its high stiffness, low density, low cost, environment friendly characteristics such as recyclablity and biodegradability, is gaining more and more interests, both in research and application. However, one…     

Photodegradation of wood flour/polypropylene composites incorporated with carbon materials with different morphologies

ABSTRACT

In this study, wood flour/polypropylene (WF/PP) composites were prepared by incorporating 2?wt% carbon materials with different morphologies, including carbon black (CB), graphite (G), and multi-walled carbon nanotubes (CNTs). WF/PP composite without any additives was included as a reference. All composites were placed in the accelerated UV weathering tester for a total of 960 h. The physical and mechanical properties of composites were compared. The changes in surface morphology and surface chemistry were characterized by SEM AFM, and ATR-FTIR. The results showed that: (1) the addition of CNTs improved both flexural and impact properties of composites; (2) composites containing CNTs exhibited better color stability and less severe surface cracking during weathering; and (3) ATR-FTIR results revealed that all the additives alleviated surface photo-oxidation of composites due to their UV-screening effect. Overall, due to the improved interfacial bonding between WF and PP, CNTs were more effective in protecting wood–plastic composites from photodegradation.     

Synergistic effect of melamine polyphosphate and aluminum hypophosphite on mechanical properties and flame retardancy of HDPE/wood flour composites

In this paper, the influence of melamine polyphosphate (MPP) and aluminum hypophosphite (AHP) on mechanical properties, flame retardancy and thermal degradation of high-density polyethylene/wood flour composites (HDPE/WF) was investigated. The synergistic effect of MPP and AHP was investigated. Polyethylene grafted with maleic anhydride (PE-g-MAH) was used as coupling agent. The experimental data demonstrated that the HDPE/WF composites with 35 wt% MPP/AHP (3:2) could achieve a LOI value of 29.6 % and UL-94 V-0 rating. In addition, the cone value also revealed that the heat release rate and the smoke production rate were clearly reduced. SEM results showed that the synergistic system (MPP/AHP = 3:2) could form a dense and thick char layer and good adhesion between wood flour and HDPE matrix, which prevented the transfer of heat flux and fuel gases. Incorporation of MPP and AHP improved the thermal stability of HDPE/wood flour as observed from the thermogravimetric analysis results and also enhanced the thermal resistance of char layer at high temperature based on scanning electron microscopy observation.     

不同材料增强苄基化木粉复合材料的制备

研究了球磨胡桑木粉苄基化改性后的增重率与材料热塑性以及力学性能的关系。随着增重率的增加,即胡桑木粉苄基化反应程度的提高,产物的热塑性变好,但材料的拉伸强度和弯曲强度增加到一定程度后,反而随着增重率的增加而下降。以胡桑木粉苄基化产物为基体,分别以球磨胡桑木粉、蒙脱土为增强材料进行共混制备复合材料,探讨增强材料与木粉苄基化产物基体的质量比对复合材料力学性能的影响。试验结果表明,复合材料的力学性能优于胡桑木粉苄基化产物,其拉伸强度和弯曲强度随增强材料质量分数的增加而先增加后降低。     

Dielectric properties of Simon poplar wood flour/polypropylene composite at oven-dry state

Interfacial compatibility is a crucial factor to the performance of wood-plastic composites （WPCs）. Yet, so far, the coupling mechanisms of WPC have not been completely understood. In order to further clarify the interfacial coupling mechanism, the dielectric constant and dielectric loss factor of Simon poplar wood flour/polypropylene composites without additives at different wood contents were measured at oven-dry state, and parameters and thermodynamic quantities of the relaxation process were also analyzed and calculated. Consequently, an obvious relaxation process based on the reorientation of methanol groups in amorphous region of wood cell wall was observed exactly that its dielectric loss factor peak decreased with the decreasing wood content within the measured range of 50%-100%. With the trend of dielectric relaxation strength, the two changing trends both revealed that the existence of polypropylene could hinder reorientation of methanol groups. Following the decreasing wood contents, the effect of the hindrance on the dielectric properties turned obvious gradually. It elucidated that introduction of polypropylene caused the quantities of hydrogen bonds formed between each methanol group and the groups around it change. The same conclusion could be drawn from the analysis of thermodynamic quantities during the dielectric relaxation progress.     

Effect of natural flake graphite on triboelectrification electrostatic potential of bamboo flour/high-density polyethylene composites

Wood Science and Technology - The influence of flake graphite (FG) content on the mechanical properties, triboelectrification electrostatic potential, and electrical resistivity of the bamboo flour...     

STUDY ON WOOD COMPOSITES DENSITY UNIFORMITY BY X-RAY

X-ray is irradiated in some wood composites(multi-layer particleboard.sin-gle-layer particleboard,reconsolidated wood,).According to the gray degree principle(0-255 grade degree)and the corresponding relation between density and gray,X-raynegatives are scanned.The numbers and pictures of every degree density are obtained andaccurate composite densities are counted.     

木纤维PP/PE共混物复合材料的流变和力学性能(英文)

For evaluation of the rheological and mechanical properties of highly filled wood plastic composites （WPCs）, polypropylene/polyethylene （PP/PE） blends were grafted with maleic anhydride （MAH） to enhance the interfacial adhesion between wood fiber and matrix. WPCs were prepared from wood fiber up to 60 wt.% and modified PP/PE was blended by extrusion. The rheological properties were studied by using dynamic measurement. According to the strain sweep test, the linear viscoelastic region of composites in the melt was determined. The result showed that the storage modulus was independent of the strain at low strain region （〈0.1%）. The frequency sweep resuits indicated that all composites exhibited shear thinning behavior, and both the storage modulus and complex viscosity of MAH modified composites were decreased comparing to those unmodified. Flexural properties and impact strength of the prepared WPCs were measured according to the relevant standard specifications. The flexural and impact strength of the manufactured composites significantly increased and reached a maximum when MAH dosage was 1.0 wt%, whereas the flexural modulus after an initial decreased, also increased with MAH dosage. The increase in mechanical properties indicated that the presence of anhydride groups enhanced the interracial adhesion between wood fiber and PP/PE blends.     

Effect of adding steam-exploded wood flour to thermoplastic polymer/wood composite

The effect of steam-exploded wood flour (SE) added to wood flour/plastic composite was examined using SE from beech, Japanese cedar, and red meranti and three kinds of thermoplastic polymer: polymethylmethacrylate, polyvinyl chloride, and polystyrene. Addition of SE increased the fracture strength and water resistance of the composite board to an extent dependent on the polymer species and the composition of wood/SE/polymer. However, water resistance decreased with the increasing proportion of SE when SE meranti was added. Effects of the wood species of SE on the properties of resulting board were small. An increased moisture content of wood flour or SE (or both) increased the variation of board performance.     

Effect of chemical modification on the properties of wood/polypropylene composites

对以铝酸酯为偶联剂对木粉进行表面改性处理后制备的木粉/聚丙烯复合材料的力学性能和形态学特征进行了研究。结果表明:铝酸酯偶联剂可以增加木塑复合材料的抗冲击强度,但会对复合材料的抗拉强度和抗弯强度造成负面的影响。对木塑复合材料的动态力学性能和微分扫描热量分析研究表明,以铝酸酯作为偶联剂,对木塑复合材料的储存模量和损失模量有少许增加,同时可降低材料的熔点和熔解热。利用扫描电镜观察木塑复合材料的木材与塑料界面发现,经铝酸酯处理过的木材与聚丙烯复合界面之间具有更好的相容性。这些研究结果表明,在木塑复合材料制造过程中利用廉价的铝酸酯作为木材化学改性剂,对改善复合材料的性质同样起作良好的作用。图6 表2 参16。     

Properties of PP/wood flour/organomodified montmorillonite nanocomposites

In this research, composites based on polypropylene (PP), beech wood flour, and organomodified montmorillonite (OMMT) were prepared and characterized for their properties. The blend nanocomposites were prepared by melt mixing of PP/WF at 50% weight ratios with various amounts of OMMT (0, 3, and 6 per hundred compounds (phc)) in a Hakee internal mixer. Then the samples were made by injection molding. The influence of organomodified montmorillonite contents on clay dispersion, physical and mechanical properties of PP/wood flour composites were investigated. Results indicated that the flexural strength and modulus, tensile strength and modulus increased by addition of 3 per hundred compounds (phc) of organomodified montmorillonite (OMMT), but decreased with 6 phc OMMT addition. However, impact strength, water absorption and thickness swelling of the composites decreased with increasing nanoclay loading. X-ray diffraction patterns (XRD) and transmission electron microscopy (TEM) revealed that the nanocomposites formed were intercalated. Also, morphological findings showed that samples containing 3 phc of OMMT had higher order of intercalation.     

Preservative properties of vapor-boron-treated wood and wood-based composites

The treatability of wood (sapwood ofCryptomeria japonica D. Don) and wood-based composites (particleboard, waferboard, medium-density fiberboard, plywood) with vapor-boron was good, and the treated materials proved to be resistant to decay fungi and subterranean termites in laboratory bioassays. No difference in effectiveness was noted between vapor-boron and liquid-boron treatment of wood. Toxic threshold values determined for solid wood were 0%–0.24%, 0.26%–0.51%, and 0.26%–0.51% BAE (boric acid equivalent), respectively, against the white-rot fungusTrametes versicolor (L.: Fr.) Pilat, the brown-rot fungusFomitopsis palustris (Berk. et Curt.), and the subterranean termiteCoptotermes formosanus Shiraki. A concentration of less than 1% BAE seemed sufficient to control biological attacks on composites, although the toxic limits could not be determined more accurately because of the tested range of boron retention. High boron retention was needed to meet the performance requirements for slow-burning materials when a fire-retardant agent was not incorporated into the glue line.     

Development of wood and wood ash-based hydroxyapatite composites and their fire-retarding properties

For making efficient use of waste wood ash emitted from wood biomass plant, the wood and wood ash-based hydroxyapatite (HAp) composite was produced and their flammability characterization was studied by thermogravimetric (DTA-TG) analysis, oxygen index (OI) measurement and cone calorimeter test. The results show that the exothermic and weight loss peaks in DTA-TG combustion profiles due to their significant thermal decomposition were weakened by the HAp agent impregnation. In addition, the OI value of HAp composites was increased by the HAp combining and the OI showed a correlation with the HAp contents. Also, the cone calorimeter study revealed that the heat release rates were decreased with increasing amount of HAp injection and accordingly their total heat release has an inverse relationship to the HAp contents. These results indicate that the treatment with wood ash-based HAp agents can enhance the flame retardancy of the treated woods.     

Effect of carbon nanotube on physical and mechanical properties of natural fiber/glass fiber/cement composites

The objective of this investigation was to introduce a cement-based composite of higher quality. For this purpose new hybrid nanocomposite from bagasse fiber,glass fiber and multi-wall carbon nanotubes(MWCNTs)were manufactured. The physical and mechanical properties of the manufactured composites were measured according to standard methods. The properties of the manufactured hybrid nanocomposites were dramatically better than traditional composites. Also all the reinforced composites with carbon nanotube, glass fiber or bagasse fiber exhibited better properties rather than neat cement.The results indicated that bagasse fiber proved suitable for substitution of glass fiber as a reinforcing agent in the cement composites. The hybrid nanocomposite containing10 % glass fiber, 10 % bagasse fiber and 1.5 % MWCNTs was selected as the best compound.