Effects of two modification methods on the mechanical properties of wood flour/recycled plastic blends composites: addition of thermoplastic elastomer SEBS-g-MAH and in-situ grafting MAH

The effect of maleic anhydride grafted styrene-ethylene- buty-lene-styrene block copolymer （SEBS-g-MAH） and in-situ grafting MAH on mechanical, dynamic mechanical properties of wood flour/recycled plastic blends composites was investigated. Recycled plastic polypro-pylene （PP）, high-density polyethylene （HDPE） and polystyrene （PS）, were mixed with wood flour in a high speed blender and then extruded by a twin/single screw tandem extruder system to form wood flour/recycled plastic blends composites. Results show that the impact properties of the composites were improved more significantly by using SEBS-g-MAH compatibilizer than by using the mixtures of MAH and DCP via reactive blending in situ. However, contrary results were ob-served on the tensile and flexural properties of the corresponding com-posites. In General, the mechanical properties of composites made from recycled plastic blends were inferior to those made from virgin plastic blends, especially in elongation break. The morphological study verified that the interfacial adhesion or the compatibility of plastic blends with wood flour was improved by adding SEBS-g-MAH or in-situ grafting MAH. A better interfacial bonding between PP, HDPE, PS and wood flour was obtained by in-situ grafting MAH than the addition of SEBS-g-MAH. In-situ grafting MAH can be considered as a potential way of increasing the interfacial compatibility between plastic blends and wood flour. The storage modulus and damping factor of composites were also characterized through dynamic mechanical analysis （DMA）.

Reinforcing effects of modified Kevlar~ fiber on the mechanical properties of wood-flour/polypropylene composites

Kevlar fiber （KF） is a synthesized product with strong mechanical properties. We used KF as a reinforcement to improve the mechanical properties of wood-flour/polypropylene （WF/PP） composites. KF was pretreated with NaOH to improve its compatibility with the thermoplastic matrix. Maleated polypropylene （MAPP） was used as a coupling agent to improve the interfacial adhesion between KF, WF, and PP. Incorporation of KF improved the mechanical properties of WF/PP composites. Treatment of KF with NaOH resulted in further improvement in mechanical strength. Addition of 3% MAPP and 2% hydrolyzed KF （HKF） led to an increment of 93.8% in unnotched impact strength, 17.7% in notched impact strength, 86.8% in flexure strength, 50.8% in flexure modulus, and 94.1% in tensile strength compared to traditional WF/PP composites. Scanning electron microscopy of the cryo-fractured section of WF/PP showed that the HKF surface was rougher than the virgin KF, and the KF was randomly distributed in the composites, which might cause a mechanical interlocking between KF and polypropylene molecules in the composites.

Creep Behaviour of Wood Flour/Poly(vinyl chloride) Composites

The experimental creep data were focused on wood-flour （WF）/poly vinyl chloride （PVC） composites with the variations in additive concentrations of wood flour, silane coupling agent, organomodified montmorillonite （OMMT） and nano-cacium carbonate （nano-CaCO3）. Their effects were analyzed using the Four-element Burger Model incorporating microscopic mechanisms. Total creep strain was low with increasing WF while elastic strain was high and plastic flow strain was low in modeling. Modification of WF with silane was beneficial to creep resistance, so did adding low ratio of OMMT （1.5 wt%） and nano-CaCO3 in composites. Thus, it was effective in reducing creep either by stiffening the PVC matrix using rigid nano-particles or by improving their adhesion with resin. However, superfluous quantity of any additament did not benefit the improvement owing to either earlier destruction of their agglomerates or stress-concentrated cracks in the over-incrassated interface.

Microwave Irradiation Treatment of Wood Flour and Its Application in PVC-Wood Flour Composites

The technique of microwave irradiation induced free radical bulk- polyaddition reactions in porous wood flour was used to modify wood flour. The behaviors of the modified wood flour under microwave irradiation, such as thermal stability and moisture sorption properties, were studied. A kind of semiinterpenetrating polymer network wood four （Semi-IPN-WF） can be formed through polymerization of MMA in the porous wood flour by microwave irradiation, and the thermal decomposition temperature of the semi-IPN-WF is considerably increased. PVC/Semi-IPN-WF composites were prepared by melt mixing in double rolls, which exhibit improved rheological properties, lower water sorption properties and outstanding mechanical performances.

Properties of paper mill sludge–wood fiber–HDPE composites after exposure to xenon-arc weathering

We used paper mill sludge（PMS） to substitute for part of the wood fibers（WF） used to reinforce high density polyethylene（HDPE）.The resulting composites were subjected to xenon-arc weathering.The composite filled with limited PMS（under 10 %） had mechanical properties and aging resistance similar to those without PMS.The composites containing more PMS faded and cracked more readily than those without PMS.Based on the carbonyl index,crystallinity,and wood index,PMS appeared to accelerate the degradation of composites during weathering.Adding PMS to WF–HDPE composites reduced the weathering resistance,and this reduction was not significant if the PMS content did not exceed 20 % of the wood fibers.Therefore,PMS could be used as a reinforcement in wood-plastic composites at levels less than20 % of the wood fiber content.

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 prop- erties 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.

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.

Mechanical properties of wood flour/recycled-thermoplastic-blends composites

The mechanical properties of composites prepared from wood flour and thermoplastic blends were investigated. Thermoplastic mixtures of polypropylene (PP) and high-density polyethylene (HDPE) and polystyrene (PS), virgin or recycled, were mixed with wood flour in a high speed blender and then extruded by a specially designed twin/single screw extruder system to form wood-flour/thermoplastic-blends composites (WTBCs). Comparative studies were made to evaluate the effectiveness of the two modification methods of the thermoplastic blends, the one of the addition of maleic anhydride grafted styrene-ethylene-butylene-styrene block copolymer (SEBS-g-MAH) as compatibilizer and the other of blend grafting of maleic anhydride (MAH) using dicumyl peroxide (DCP) as initiator by reactive extrusion. The results showed that the impact properties of WTBCs using SEBS-g-MAH as compatilizer were better improved than that of the blend grafting. However, adverse results were observed on the tensile and flexural properties of the corresponding WTBCs. The mechanical properties of WTBCs prepared from recycled plastic blends were poorer to some extent than that from virgin plastic blends in general, especially in elongation break. The morphology of WTBCs breaking section was analyzed by scanning electron microscopy (SEM) and the results showed that a good interfacial adhesion between wood flour and polymer matrix was observed with both of the two modification methods. However, by blend grafting of adding DCP as initiator and MAH as monomer, a better interfacial bonding between wood and plastic matrix was obtained than that of the addition of SEBS-g-MAH. Blend grafting can be considered as a potential way of increasing the interfacial compatibility of different plastics and between plastic blends and wood.

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

A study was conducted to investigate the effects of compatibilizers, including Maleic anhydride grafted polypropylene （MA-PP） and maleic anhydride grafted ethylene-propylene-diene copolymer （MA-EPDM）, on wood-flour/polypropylene （WF/PP） composites. WF/PP composites were prepared by direct extrusion profiles using a twin-screw/single-screw extruder system. DMA analysis showed that the loss factor of composites decreased and the storage modulus improved in the presence of MA-PP, which indicated much better interfacial adhesion between the PP matrix and wood flour filler than in the absence of compatibilizer. Morphological feature based on SEM observation showed that MA-PP and MA-EPDM improved the dispersion of the wood particles in the plastic matrix. MA-EPDM is a soft segment, although it improved the interfacial adhesion, storage modulus decreases with adding of MA-EPDM. As compatibilizer of wood-flour/polypropylene composites, both DMA analysis and SEM feature proved that MA-PP was superior to MA-EPDM.

Study on Water Resistance of Polydopamine Treatment Wood Flour/Polypropylene Composites

This paper aims to investigate the water absorption of wood flour/polypropylene composites and its effects on dimensional stability and crystallization properties. Wood-plastic composites (WPCs) makes using polydopamine modified wood flour (WF-D), virgin polypropylene, maleic anhydride-grafted polypropylene (MA) and antioxidant, by using hot-pressing moulding. Water absorption (WA), thickness swelling (TS) and failure of flexural properties of the composites have studied for a range of immersion times. It is found that the WA and TS have increased with WF content and immersion time. The water absorption and thickness swelling of WPCs are 0.85% and 0.99%, respectively, after 8 days immersion. With the prolonging of immersion time, the impact strength, flexural strength and flexural modulus of WPCs increase first and then decrease. The impact strength decreases from 3.32 kJ/m2 to 2.94 kJ/m2, the retention rate is 88.55%;the flexural strength and flexural modulus by 68.58 Mpa and 3.92 Gpa, respectively. WPCs crystallization and thermal properties decrease slightly. Microstructures of the composites are examined to understand the mechanisms for the wood-plastic interaction which affects the water absorption and thickness swelling. Our work demonstrates that using polydopamine treatment wood flour for preparing WPCs can be an efficient way to improve the water resistance of WPCs.

The effect of Poly-ethylene-co-glycidyl methacrylate efficiency and clay platelets on thermal and rheological properties of wood polyethylene composites.

Global ecological concerns have resulted in an interest in renewable natural materials. Composites based on high density polyethylene (HDPE), wood fiber (Veneer) and containing coupling agents like nanoclay (NC) and poly-ethylene-co-glycidyl methacrylate (PEGMA) were made by melt compounding and then injection molding. In this study, the effects of two variable parameters namely nanoclay and coupling agent on the rheological and thermal properties of wood polyethylene composites (WPECs) were investigated. The study investigates the morphology phase, rheology behaviors and thermal properties by scanning electron microscope, capillary rheometer and thermal gravimetric analyzer. The SEM micrographs of the composites showed that the outer surfaces of the wood were coated by a section of amorphous lignin. The state of dispersion in HDPE/pine/clay composites was improved by EGMA because it could interact with pine flour in addition to clay. The interaction of reinforcement with coupling agent and HDPE matrix is strong based on the observation of the fracture surface of composites when EGMA is present. However the addition of 2.5% clay slightly lowered the initial degradation temperature (Td) but did not improve the thermal stability. Obviously, all the composites materials exhibit viscoelastic values greater than those of neat HDPE.

多功能磷酸酯共聚物阻燃HDPE木塑复合材料的性能

以1-氧基磷杂-4-羟甲基-2,6,7-三氧杂双环[2.2.2]辛烷、多聚磷酸、1,4-丁二醇二缩水甘油醚、双酚A型环氧树脂和三聚氰胺为原料合成磷酸酯共聚物,以其为阻燃剂对高密度聚乙烯(HDPE)/木粉(WF)木塑复合材料进行阻燃改性,并评价了阻燃剂含量对复合材料阻燃性能、力学性能和热性能的影响。结果表明:集酸源、气源和碳源为一体的磷酸酯共聚物的热稳定性明显高于常规磷系阻燃剂,阻燃剂含量为20%(w)时,HDPE/WF复合材料的垂直燃烧等级达到UL 94 V-0级,极限氧指数高达31.5%,残炭量提高了21.5%(w);随阻燃剂含量增加,复合材料的拉伸强度呈先上升后下降的趋势。

APP对木粉-HDPE复合材料阻燃和力学性能的影响

以聚磷酸铵(APP)对木粉-HDPE复合材料(WF-HDPE)进行阻燃处理,用锥形量热仪系统评价复合材料的阻燃性能,并进行等温燃烧反应动力学分析,用万能力学试验机进行静态力学试验。结果表明,在35 kW/m2热辐射流量下,APP添加量达到15%时,WF-HDPE燃烧热释放速率(RHR)峰值和总热释放量(THR)均降低约50%、成炭率提高150%,表现出显著的阻燃作用;可用动力学模型ln(1-α)=-kt+C描述WF-HDPE的等温燃烧反应,APP的加入使反应速率常数k降低、半衰期延长。APP对WF-HDPE的冲击性能有显著的不利影响,但能改善刚性,对弯曲强度和拉伸强度影响不大。综合阻燃性能与力学实验结果,APP的适宜添加量为15%左右。

木粉/HDPE复合材料的力学性能与流动性能

用木粉与高密度聚乙烯 (HDPE)复合制备了能代替木材的复合材料。考察了木粉含量、粒度、界面相容剂用量对复合材料力学性能、流动性的影响。结果表明 ,复合材料的弯曲强度随木粉含量的增加而提高 ,冲击强度随木粉含量的增加而下降 ;弯曲强度随木粉粒度减小显著降低 ,而冲击强度先有所升高而后降低 ;界面相容剂能有效改善材料的性能 ,其较佳用量约为 5 % (质量分数 )

硅烷偶联剂对HDPE/木粉复合材料性能的影响

使用经硅烷偶联剂HP-172和HP-174改性的木粉制备了HDPE／木粉复合材料。研究了偶联剂用量对其性能的影响。实验结果表明：当使用1．5％的HP-172处理木粉后。可使复合材料的各项力学性能提高30％以上；HP-174的用量为1％-1.5％也得到了较好的改性效果。通过FIR和SEM分析发现，硅烷偶联剂可与木粉表面发生化学反应，从而提高了HDPE与木粉的界面粘合强度，使复合材料的力学性能得以提高.

改性橡胶木粉/HDPE复合材料结构和力学性能的研究

用硅烷偶联剂A-171和天然橡胶胶乳(MGL-30)改性碱处理后的橡胶木粉。研究了木粉粒径、改性剂和木粉质量分数对橡胶木粉填充HDPE复合材料力学性能的影响,并对复合材料的断面形貌和木粉的表面结构进行了SEM分析。结果表明:木粉粒径、改性剂及木粉质量分数对复合材料力学性能有较大的影响。改性后木粉与基体HDPE的界面粘结强度提高,从而有效地提高了复合材料的力学性能。

磷酸脒基脲与聚磷酸铵协同阻燃的木粉/HDPE复合材料

采用锥形量热仪(CONE)、极限氧指数(LOI)、热重分析(TGA)和力学试验等研究手段,分析聚磷酸铵(APP)、磷酸脒基脲(GUP)及二者复配(GUP/APP)对木粉/高密度聚乙烯(WF/HDPE)复合材料燃烧性能、热降解行为以及力学性能的影响。CONE研究结果表明:APP可显著降低WF/HDPE复合材料的热释放,但同时也使得复合材料的烟释放增加;将GUP与APP按适当比例复配不仅可以有效抑制复合材料的热释放,而且可以降低烟释放速率,表现出较好的协同阻燃和抑烟作用。TGA结果表明:GUP与APP复配使得WF/HDPE复合材料的初始热分解温度降低,残炭产率提高。此外,GUP和APP复配阻燃WF/HDPE复合材料具有较高的氧指数和较小的力学性能损失。

废纸浆/HDPE复合发泡材料的流变行为及发泡形态

将废旧瓦楞纸板粉碎制浆,与HDPE(高密度聚乙烯)通过模压成型制备了废纸浆/HDPE发泡复合材料。利用英国Rosand双料筒毛细管流变仪,在线研究了发泡剂AC含量、废纸浆含量、温度以及吸热、放热和平衡发泡剂对废纸浆/HDPE复合发泡材料的流变行为的影响,并在SEM下观察了不同AC含量和废纸浆含量对发泡形态的影响。结果表明:废纸浆/HDPE复合发泡材料熔体表现为假塑性流动特征,当剪切速率达到600s-1时,出现管壁滑移现象。发泡剂AC能明显降低熔体黏度,随着AC含量的增加,熔体黏度下降。随着废纸浆含量的增加,熔体黏度增加。当剪切速率小于275s-1时,随着温度的升高,熔体黏度降低;当剪切速率大于275s-1时,熔体黏度反而随着温度的升高而升高。当剪切速率小于325s-1时,吸热型发泡剂(NaHCO3)熔体黏度最高;当剪切速率大于325s-1时,放热型发泡剂AC熔体黏度最高。通过SEM观察发现,随着发泡剂AC含量的增加,泡孔数量增加,孔径变小;随着废纸浆含量的增加,泡孔数量减小,孔径增大,泡孔合并现象严重。