Dielectric properties of copper-ethanolamine treated Chinese fir (Cunninghamia lanceolata Hook.)

In order to clarify the interaction between copper and wood substances in wood treated with copper containing water-borne wood preservatives, the dielectric constant ε′ and dielectric loss factor ε″ of untreated wood and wood treated with four concentration levels of copper-ethanolamine (Cu-EA) solutions were determined within a temperature range from –100 to 40°C and a frequency range from 100 to 1 MHz. Three dielectric relaxation processes were observed in the ε″ spectrum; among them R-I is based on the reorientation of methylol groups in the amorphous region of wood cell walls and R-II is related to wood extractives. R-III appeared in Cu-EA treated wood, and its magnitude decreases with the concentration of Cu-EA solutions used in this experiment. This relaxation process was considered to be based on the reorientation of copper-ethanolamine-wood complexes in wood cell walls. At low copper retention, the hydrogen in the complex can form hydrogen bonding with adjacent hydroxyl groups, which results in a strong bonding state between copper and wood; at high copper retention, the numerous copper-ethanolamine complexes not only hinder them from forming hydrogen bonding with adjacent wood molecules due to steric hindrance, but also weaken the interaction between wood molecules themselves, which corresponds to reducing ε″ values of both R-I and R-III processes. The results explain the fact of in-creasing copper leaching in wood treated with high concentration copper-based water-borne preservatives.     

木粉加入量对木／塑复合材料性能影响的研究

研究了聚丙烯与木粉以不同比率复合而成的材料的物理力学性能和复合形态特征。结果表明：不同混合比率的聚丙烯与木粉进行复合后所得的复合材料，除冲击强度有所降低外，其它力学性能均比纯聚丙烯的有较大幅度的提高。木粉表面的酯化处理可以改善木塑界面之间的相容性和复合材料的均匀性。在木塑复合过程中木塑之间发生镶嵌现象使木塑之间产生物理结合。     

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.     

Effect of organoclay platelets on the mechanical properties of wood–plastic composites formulated with virgin and recycled polypropylene

Abstract

This study investigated the effects of organoclay platelet contents (0, 3 and 5 wt%) and polypropylene type (virgin and recycled) on the mechanical properties of polypropylene/wood flour composites. Composite samples were made by melt compounding and consequent injection moulding. The tensile, flexural and impact properties of resultant composites were determined. X-ray diffraction (XRD) analysis of composites with 3 and 5% nanoclay content was also conducted. The results indicated that tensile and flexural properties of the composites increased with the addition of nanoclay particles up to 3 wt% and decreased thereafter. The impact strength of the composites, however, decreased with the incorporation of nanoclay. The mechanical properties of the recycled polypropylene-based nanocomposites were statistically comparable with those based on virgin polypropylene. XRD analysis revealed that the degree of intercalation in the nanocomposites containing 3% nanoclay was higher than in those containing 5%. Based on these results, it can be concluded that recycled polypropylene could be used instead of virgin polypropylene in the production of value-added products with no significant adverse effects on the mechanical properties.     

Overlapping of dielectric relaxation spectra in oven-dry yellow birch at temperatures from 20 to 100°C

Summary The existence of three overlapping dielectric relaxation spectra from oven dry yellow birch was found over the frequency range from 20 Hz ... 2 GHz and at the temperature range from 20 ... 100°C. Origin of the spectra is largely attributed to hindered reorientation of various dipolar groups in the material. The spectra were resolved in terms of the super-position principle for dielectric loss and permittivity, and the distribution of relaxation times. The spectral resolution was checked by the Cole-Cole plot. The values for the activation energies indicate, as expected, that the dipolar groups are imbedded by hydrogen bonding in the solid structure. The crystalline portion of native cellulose in the wood estimated from the spectra agrees with such data from other sources.     

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 Wood Variables on the Properties of Wood Fiber-Polypropylene Composites

The effect of wood species (Chinese fir and Poplar), wood fiber content (10%, 25%, 40%) and wood fiber sizes (16 to 32 mesh, 32-65 mesh, above 65 mesh) on the properties of the wood fiber-Polypropylene composites were studied in this paper. The results indicate that the effect of wood fiber content and size in composite were more important than that of chosen wood species. Compared with polypropylene without wood fiber, the flexural strength of the composites increased when adding wood fiber into polypropylene, but the tensile and unnotched charpy impact strength decreased. And the above strength decreased with the wood fiber content increasing. When the wood fiber size becoming smaller (in higher mesh), the strength increased. In the comparison of wood species, the properties of composite using Chinese fir wood were better than that of Poplar, but not significant. The dynamic mechanical properties of the composites and PP were also tested and analyzed in this paper.     

木/麻/PP纤维含量对复合材料性能的影响

采用无纺织气流成型织坯再热压的工艺,研究汽车内饰用木/麻/PP纤维三元复合材料中,3种纤维含量对复合材料性能的影响.研究结果表明,增加PP纤维含量,可以提高复合材料的静曲强度和耐水性;麻纤维含量增加对提高材料的强度影响显著,但耐水性略有下降.当PP纤维含量为40%、麻纤维为30%、木纤维30%时,复合材料的性能较佳.     

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…     

Dynamic Mechanical Properties of Wood Powder /Polypropylene Composites

The dynamic mechanical properties of wood powder/polypropylene composites with different wood content treated and untreated with the compatibilizer have been studied. It has been found that addition of wood powders and the compatibilizer can both improve the viscoelasticity of composites. Glass transition temperature (Tg) of appropriate wood powder-filled composites decreased. The value for the storage modulus (G') increased gradually with increasing wood powder content. The addition of the compatibilizer made glass transition temperature shift to a higher temperature. DSC (Differential Scanning Calorimetry) results showed that, for pure PP, the addition of the compatibilizer decreased its melting point, and increased its Calorie of Melt at the same time. For the composite with 50 % wood powder treated with the compatibilizer, the melting point was almost unchanged, but its Calorie of Melt decreased.     

MAPP改性木粉/聚丙烯复合材料的物理力学性能

木塑复合材料的界面相容性是决定其性能的关键因素,通过添加偶联剂的方法能够改善其界面相容性,从而提高其性能。通过测定毛白杨木粉/聚丙烯复合材料的物理力学性能来研究木粉含量和偶联剂添加量对木塑复合材料物理力学性能的影响,为进一步研究木塑复合材料的界面相容性提供理论依据。研究结果表明:随着木粉含量的增加,复合材料的物理力学性能下降,并且在高木粉含量阶段影响显著;高木粉含量复合材料的性能较差,添加MAPP能显著改善其物理力学性能。     

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.     

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。     

木/塑复合强化木地板基材复合机理研究

采用扫描电镜显微分析及热分析研究相容剂改性后的木纤维增强聚丙烯复合材料,结果表明相容剂可提高木纤维与塑料基体的浸润性,提高复合材料的相变温度及热稳定性。     

SEBS-g-MAH和原位接枝MAH对木粉/废旧塑料混合物复合材料力学性能的影响研究

由聚丙烯（PP）、高密度聚乙烯（HDPE）和聚苯乙烯（PS）组成的混合废旧塑料与木粉经高速混合机混合后,采用双螺杆/单螺杆串联挤出机组制备了木粉/混合废旧塑料复合材料。探讨了马来酸酐接枝苯乙烯-乙烯/丁烯-苯乙烯嵌段共聚物（SEBS-g-MAH）和原位接枝马来酸酐（MAH）对木粉/混合废旧塑料复合材料力学性能的影响。结果表明,与使用MAH和DCP的原位反应共混相比,SEBS-g-MAH显著提高了复合材料的抗冲击性能,但对拉伸和弯曲性能的改善不如原位反应共混显著。总的来说,混合废旧塑料制备的复合材料的力学性能要低于纯塑料混合物制备的复合材料,尤其是拉伸断裂伸长率。微观形态研究表明,添加SEBS-g-MAH和原位接枝MAH均可提高木粉与塑料混合物之间的界面相容性,但与添加SEBS-g-MAH相比,原位接枝MAH能更好的改善PP、HDPE、PS与木粉之间的界面结合。原位接枝MAH可被看作是一种改善木粉与塑料混合物间界面相容性的有效途径。此外,采用动态力学分析（DMA）进一步表征了复合材料的储能模量和阻尼因子。     

汽车用木粉/聚丙烯复合板的研制

通过气味检测、红外光谱和热失重法,分析出木粉/聚丙烯复合材料产生刺激性气味的原因在于材料的热稳定性较差;应用碱处理、预涂偶联剂、掺入吸附剂和增容剂等方法对木粉进行预处理,测试结果表明,采用碱处理木粉压制的WPC,其气味等级可达到上海某汽车制造企业PV 3900标准3.0级要求.     

可膨胀石墨与聚磷酸铵对木粉/聚丙烯复合材料的协同阻燃作用(英文)

采用锥形量热仪(CONE)研究可膨胀石墨(EG)与聚磷酸铵(APP)对木粉/聚丙烯复合材料的协同阻燃作用。CONE测试结果表明:EG和APP均可降低木粉/聚丙烯复合体系的热释放速率(HRR)、总热释放(THR)和烟释放速率(RSR),提高成炭率;与APP相比,EG表现出更好的抑烟效果。当EG与APP的总添加量为15%、复配比例为2∶1时,能形成稳定致密的膨胀炭层,阻燃协同效应显著。力学性能测试结果表明:即使在马来酸酐接枝聚丙烯相容剂(MAPP)的存在下,EG和APP阻燃剂的添加对复合材料的冲击强度和弯曲强度仍有不利影响,但EG的添加可提高复合材料的弯曲模量。     

Current Research and Development on Deformation and Fixation of Bended Wood and Wood-based Composites

There are many advantages of bended wood,such as good-looking shape,simple process and low cost.The product,however,is easy to get recovery,which is urgent to be dealt with.This paper concludes the features of deformation and recovery of bended wood and wood-based composites and summarizes four treating methods to keep dimensional stability.Compared to bended solid wood,some elementary perspectives on the research of bended wood-based composites are presented.The purpose of this paper is to suggest:1)to investigate the optimum heating time and temperature that bended wood and wood-based composites need from the formation of deformation to the recovery and to the permanent fixation,according to its changes of dimensional stability such as curvature radius;2)to measure the composites comprised of wood and adhesives on the changes of stress relaxation,dynamic viscoelasticity and crystal1ization field;3)to quantitatively analyze changes of the major components in wood cell wall polymers as well as the composites under heat/steam treatment and untreated conditions.It will be helpful for subsequent research to clarify on the mechanisms of permanent fixation of bended wood and also contribute to that of wood-based composites.     

马来酸酐接枝PP/PE共混物及其木塑复合材料

通过聚丙烯(PP)与聚乙烯(PE)机械混合来模拟废旧塑料混合物,利用马来酸酐(MAH)对PP/PE混合物进行接枝改性,然后以接枝共混物作为基体与木纤维复合制备木塑复合材料。通过对比接枝前后的红外光谱图,证明MAH已成功接枝在PP/PE共混物上。力学测试结果显示:基体经过接枝改性后,复合材料的弯曲强度和无缺口冲击强度均大幅度升高,当MAH用量为1%时,弯曲强度提高了50.4%,无缺口冲击强度提高了90.8%,而以废旧塑料为原料制备的复合材料的弯曲强度和无缺口冲击强度分别提高40.2%和53.4%。微观相形态分析表明:通过接枝改性不仅改善了PP/PE共混体系的相容性,同时也显著改善了木纤维与PP/PE共混物之间的界面结合状况,因而宏观上表现为力学性能提高。这表明,共混接枝改性方法可能是利用混合废旧塑料制备高性能木塑复合材料的一条可行途径。