Wear behavior of straw fiber-reinforced polyvinyl chloride composites under simulated acid rain conditions

In order to investigate the effect of simulated acid rain (SAR) corrosion on the wear-resistance properties of straw fiber/polyvinyl chloride (SPVC) composites, four types of straw fibers (wheat straw (WS), rice straw (RS), corn straw (CS), and sorghum straw (SS) fibers) were utilized and incorporated into poly(vinyl chloride) (PVC). The results show that the SS fibers have high levels of cellulose, lignin and crystallinity, and it also exhibited high adhesion strength with PVC matrix, which endow the SS/PVC with high wear-resistance compared with other three SPVC composites. After SAR corrosion, SPVC composites exhibited severe degradation of the physical, mechanical, and thermal properties, and the fibers were easily pulled out from the matrix to form abrasive particles. The high-speed fiber debris in high-temperature and high-loading environments can be deemed a kind of “incompressible lumps” that will form a certain abrasive wear.     

Effects of Rice Straw Powder (RSP) Size and Pretreatment on Properties of FDM 3D-Printed RSP/Poly(lactic acid) Biocomposites

To develop a new kind of environment-friendly composite filament for fused deposition modeling (FDM) 3D printing, rice straw powder (RSP)/poly(lactic acid) (PLA) biocomposites were FDM-3D-printed, and the effects of the particle size and pretreatment of RSP on the properties of RSP/PLA biocomposites were investigated. The results indicated that the 120-mesh RSP/PLA biocomposites (named 120#RSP/PLA) showed better performance than RSP/PLA biocomposites prepared with other RSP sizes. Infrared results showed that pretreatment of RSP by different methods was successful, and scanning electron microscopy indicated that composites prepared after pretreatment exhibited good interfacial compatibility due to a preferable binding force between fiber and matrix. When RSP was synergistically pretreated by alkaline and ultrasound, the composite exhibited a high tensile strength, tensile modulus, flexural strength, and flexural modulus of 58.59, 568.68, 90.32, and 3218.12 MPa, respectively, reflecting an increase of 31.19%, 16.48%, 18.75%, and 25.27%, respectively, compared with unmodified 120#RSP/PLA. Pretreatment of RSP also improved the thermal stability and hydrophobic properties, while reducing the water absorption of 120#RSP/PLA. This work is believed to provide highlights of the development of cost-effective biocomposite filaments and improvement of the properties of FDM parts.     

Withdrawal strength of fasteners in rice straw fibre-thermoplastic composites under dry and wet conditions

The withdrawal strength of nail and screw fasteners has been studied in rice straw fibre-thermoplastic composites. Two types of thermoplastic, virgin polyethylene (PE) and polypropylene (PP), were selected as separate composite matrices. Three levels of dry rice straw fibre, 45%, 60% and 75%, based on the composition by weight and passed through a 40-mesh size screen was mixed with the polymeric matrices without and with 2% (based on weight) maleic anhydride grafted polypropylene (MAPP) as coupling agent. A dry-blending method was used for compounding the materials. The 12 formulations for the polymer composites were used to prepare samples with dimensions 25 cm by 15 cm by 1 cm. The final composites were made by pressing the prepared mats between the hot plates of a compression press by employing combinations of temperature and pressure in three stages. After keeping the composites at room temperature for 15 days, the withdrawal strengths of nails and screws were measured according to BS Standard (CEN/TS 15534–1:2007) for dry composites. Withdrawal strengths were also measured after immersion of the composites for 24 h in distilled water (wet condition). The results showed that the withdrawal strength of screws is more than that of nails. Also, irrespective of the type of polymer, the percentage of rice straw fibre may significantly influence the withdrawal strength of fasteners, especially at the higher fibre to polymer ratios. Furthermore, it was found that in the wet condition the withdrawal strengths of the nail fasteners are reduced more (73.66%) than for the screws (28.9%).     

秸秆预处理工艺对秸秆基人造板性能的影响

随着木材工业的快速发展,以及木材原料的日益减少,利用农作物秸秆代替木材生产复合材料十分必要。 本文以水稻秸秆为原料,以脲醛树脂为粘合剂,通过湿热法、偶联剂表面化学改性的方法,对秸秆表面进行改性,从而提高了树脂和秸秆之间的结合力,探索了水稻秸秆板的制作工艺。 实验表明较好的制备工艺为:温度150 ℃,压强15 MPa,热压时间8 min,树脂胶粉和水的质量比为1:1,脲醛树脂胶含量为15%(质量分数),发现秸秆表面预处理采用γ-缩水甘油醚氧丙基三甲氧基硅烷(KH560)偶联剂后,所制得的秸秆板的诸多性能优于未经预处理及采用γ-氨丙基三乙氧基硅烷(KH550)进行改性后所制的秸秆板。     

Synergistic effect of polyfunctional silane coupling agent and styrene acrylonitrile copolymer on the water‐resistant and mechanical performances of glass fiber–reinforced polyamide 6

Adverse effects of a high‐water absorption rate on properties of a glass fiber–reinforced polyamide 6 (GF‐PA6) composite significantly reduce performance and limit application in humid environments. In this paper, a polyfunctional silane (PFS) coupling agent with amino (–NH₂) and imino (–NH) groups and styrene acrylonitrile copolymer (SAN) were added to a composite, GF‐PA6, to prepare GF‐PA6/SAN/PFS composites via melt blending in a twin‐screw extruder. The effects of SAN and PFS content on the static and dynamic mechanical properties of the composites before and after water absorption were investigated in detail. The microstructure of the fracture surface was analyzed by a scanning electron microscope (SEM). The results show that the addition of SAN and PFS could effectively inhibit water absorption of the GF‐PA6 composites. The alkoxyl groups on PFS reacted chemically with the nitrile groups of SAN, which enriched SAN on the interface between the fiber and matrix during the extrusion and mixing process to improve the effect of water prevention. Therefore, the mechanical properties of the wet state were notably improved while preventing water from permeating the interface by only the addition of a small amount of SAN and PFS. Dynamic mechanical analysis (DMA) results showed that the addition of PFS improved the compatibility of PA6 with SAN and enhanced the interface adhesion between fiber and PA6. In terms of test result of the comprehensive performance, 10 phr SAN with 0.6 phr PFS was the best dosage.     

钛酸酯偶联剂的结构对PVC/木质素复合材料性能的影响

本文采用钛酸酯系列偶联剂对造纸工业废渣──木质素磺酸盐进行处理，然后填充聚氯乙烯（PVC）制成复合材料．结果发现用钛酸酯类偶联剂处理的木质素磺酸盐，填充PVC体系，其拉伸强度随使用钛酸酯偶联剂不同，拉伸强度下降幅度不同，而冲击强度和伸长率都不同程度上升，尤以冲击强度的提高最为明显．     

共混方法对聚氯乙烯/聚丙撑碳酸酯相容性影响

本文分别用溶液法和熔融法制得聚氯乙烯（PVC）与聚丙撑碳酸酯（PPC）共混试样，用DSC证明PVC／PPC共混物不相容，但它们不相容的程度受分子量、共混比例等因素的影响，并根据玻璃化转变温度（Tg）计算出溶液共混试样PPC富相中PVC的重量百分含量。NBR／PPC弹性体作偶联剂对PVC／PPC共混体系具有较好的增容作用，共混物中PPC的用量及分子量对共混体系性能有一定的影响。     

偶联剂对聚氯乙烯－聚丙撑碳酸酯共混体系力学性能的影响

偶联剂对聚氯乙烯－聚丙撑碳酸酯共混体系力学性能的影响王胜杰，黄玉惠，丛广民（中国科学院广州化学研究所广州５１０６５０）关键词聚氯乙烯，聚丙撑碳酸酯，偶联剂，丁腈胶，过氧化苯甲酰，共混聚氯乙烯（ＰＶＣ）是用量巨大的通用塑料，其软性制品需用大量的增塑剂，...     

Properties of poly(vinyl chloride)/wood flour/montmorillonite composites: Effects of coupling agents and layered silicate

Organomodified montmorillonite (OMMT) was prepared using cetylalkyl trimethyl amine bromide. OMMT and wood flour (WF) were surface-modified by silane coupling agent. They were melt-blended with polyvinyl chloride (PVC) and extruded into wood-plastic composite samples using one conical twin screw extruder. The effects of their contents on the composite mechanical properties were investigated. X-ray diffraction, transmission electron microscopy and scanning electron microscopy observed intercalation and dispersion of the OMMT. FTIR and X-ray photoelectron spectroscopy were used to analyze the silane-modification effects. The possible reaction mechanisms were proposed. After wood flour was modified by 1.5 phr silane, the impact strength and the tensile strength of wood flour-PVC composite were increased by 14.8% and 18.5%, respectively. Mechanical tests showed that the addition of OMMT did not enhance the untreated wood flour-PVC composites. However, adding 0.5% OMMT did improve the mechanical properties of the treated ones. The grafting improved the interfacial compatibility between components producing higher properties of the composites. Further addition of OMMT reinforced the composites. Too higher contents of silane and OMMT impaired some properties because of weak interfacial layer and higher concentrated stress. Cone calorimetry showed that the fire flame retardancy and smoke suppression of composites were strongly improved with the addition of OMMT.     

弹性体偶联剂结构对PVC/PPC性能的影响

NBR－PPC弹性体偶联剂能促进PPC（聚丙撑碳酸酯）与PVC（聚氯乙烯）之间的相容性，改善共混物的力学性能，并在共混体系中产生轻度交联。偶联剂组成在NBR／PPC比例为70／30，NBR（丁腈橡胶）含腈量为34％，BPO过氧化苯甲酸用量为2．5份时，共混物的综合力学性能最佳，但偶联剂预先硫化时间不宜过长．     

Morphology and fracture behavior of toughening‐modified poly(vinyl chloride)/organophilic montmorillonite composites

Toughening‐modified poly(vinyl chloride) (PVC)/organophilic montmorillonite (OMMT) composites with an impact‐modifier resin (Blendex 338) were prepared by melt intercalation, and their microstructures were investigated with wide‐angle X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy. The mechanical properties of the PVC composites were examined in terms of the content of Blendex and OMMT, and the fracture toughness was analyzed with a modified essential work of fracture model. Intercalated structures were found in the PVC/OMMT composites with or without Blendex. Either Blendex or OMMT could improve the elongation at break and notched impact strength of PVC at proper contents. With the addition of 30 phr or more of Blendex, supertough behavior was observed for PVC/Blendex blends, and their notched impact strength was increased more than 3319% compared with that of pristine PVC. Furthermore, the addition of OMMT greatly improved both the toughness and strength of PVC/Blendex blends, and the toughening effect of OMMT on PVC/Blendex blends was much larger than that on pristine PVC. Blendex and OMMT synergistically improved the mechanical properties of PVC. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 286–295, 2004     

纳米TiO2/聚N-异丙基丙烯酰胺复合水凝胶的合成及其表征

通过利用偶联剂和超声分散将TiO₂表面功能化, 在其表面引入烯键, 与聚N-异丙基丙烯酰胺在交联剂存在下共聚, 制备了不同纳米TiO₂含量的聚N-异丙基丙烯酰胺复合水凝胶．采用红外光谱、扫描电镜、紫外光谱、热重分析、动态粘弹谱仪等表征了复合水凝胶的微观结构和形貌, 测试了复合凝胶材料对紫外线的吸收、热稳定性、机械强度及其韧性. 结果表明: 纳米TiO₂粒子的引入, 使得复合凝胶材料对紫外线吸收效果显著, 凝胶的稳定性、机械强度及韧性得到明显改善.     

MMA接枝改性PVC/CaCO3纳米复合材料的力学性能

采用熔融共混法制备PMMA接枝改性纳米CaCO3增韧PVC（PVC/CaCO3）复合材料,并研究了复合材料的力学性能.结果表明,通过表面PMMA的接枝改性,可以显著提高纳米CaCO3增韧聚氯乙烯复合材料的拉伸强度和拉伸模量,在纳米CaCO3颗粒表面PMMA包覆层厚度为2nm时,复合材料的拉伸强度和拉伸模量达到极大值.对比于未处理纳米CaCO3和钛酸酯偶联剂处理纳米CaCO3,PMMA接枝改性纳米CaCO3增韧PVC复合材料的拉伸强度得到较大幅度提高.SEM显示,经过PMMA接枝改性后的碳酸钙在PVC基体中分散均匀,与基体界面结合良好.     

氯化聚丙撑碳酸酯增容聚丙撑碳酸酯/秸秆粉复合材料的制备及性能

聚丙撑碳酸酯(PPC)是一种新型热塑性生物降解材料,但其热性能及力学性能较差,应用受到限制。以秸秆粉这种农作物副产品作为增强体改性PPC,既可以提高PPC的力学性能同时又可开发利用秸秆资源。氯化聚丙撑碳酸酯(CPPC)是聚丙撑碳酸酯(PPC)经过氯化得到的,对天然纤维表面具有良好的浸润性和粘结性。本文以CPPC为增容剂,通过熔融共混法制备了PPC/秸秆粉复合材料。采用扫描电子显微镜(SEM)、拉伸实验、动态力学性能测试(DMA)及转矩流变仪对复合材料的结构及性能进行了表征,重点考察了CPPC的添加量对复合材料力学和流变性能的影响。结果表明,当CPPC质量分数为1.8%时,可使添加质量分数为30%秸秆粉的PPC复合材料拉伸强度提高38%,模量提高30%。同时,CPPC的引入使复合材料的粘度下降,改善了PPC/秸秆粉复合材料的加工性能。因此,作为增容剂的CPPC为制备高性能PPC/天然纤维复合材料提供了新的解决办法。     

新型软质抗静电聚氯乙烯材料的研究

合成了一种长链季铵盐类化合物, 将其用作抗静电剂添加到软质聚氯乙烯(PVC)材料中, 测试了材料的表面电阻、力学性能, 并采用扫描电子显微镜测试研究了其结构. 结果表明: 随合成长链季铵盐的添加量增大, PVC材料的表面电阻率降低, 较小的添加量(4.5%)即可使材料的表面电阻率降低至3.0×10⁸ Ω以下, 达到了煤矿行业对高分子材料抗静电性能的要求. 在上述抗静电PVC材料中添加一定量的聚氧化乙烯(PEO), 可以降低抗静电材料对环境湿度的依赖性, 并提高PVC材料的力学性能和抗静电性能.     

Structural and mechanical studies on modified reused tyres composites

Reused tyres powder was used as reinforcement in HDPE-reused tyre composites. In order to improve the compatibility between both components, several pre-treatments performed over the rubber tyres were applied: sulphuric acid etching, use of a silane coupling agent and chlorination with trichloroisocyanuric acid (TCI). Mechanical properties of the resulting materials (e.g. tensile strength, Young’s Modulus, toughness and elongation at break) were studied and compared. Chemical modifications on the surface of reused tyres were monitored by FTIR and physical modifications and behaviour to fracture were followed by means of SEM. The influence of rubber pre-treatment was assessed by comparing the results of treated and untreated composites with those for neat HDPE. Reused tyre rubber, added to the HDPE in small quantities, acts as a filler, improving the stiffness and providing a more brittle behaviour. Pre-treatment with TCI gave poor results in terms of mechanical properties obtaining lower values than neat HDPE in some cases and always worst properties than sulphuric or silane coupling agent. Treatments with H₂SO₄ and silane coupling agent improve the ability of rubber to interact with the HDPE, increasing the material’s stiffness and its tensile strength. Sulphuric acid modificates chemical and physically the particles’ surface improving mainly mechanical adhesion, whereas silane acts as a compatibilizer developing chemical matrix-reinforcement interactions.     

连续纤维增强含二氮杂萘酮联苯结构聚芳醚砜酮树脂基复合材料的界面

利用射频感性耦合冷等离子体(ICP)处理技术改性连续纤维表面,分别采用X射线光电子能谱(XPS)、原子力显微镜(AFM)及动态接触角分析(DCA)系统研究了等离子体处理时间、放电气压、放电功率等工艺参数对连续碳纤维、芳纶纤维和对亚苯基苯并二噁唑(PBO)纤维的表面化学成分、表面形貌、表面粗糙度及表面自由能的影响.研究结...     

Wear behavior of wood–plastic composites in alternate simulated sea water and acid rain corrosion conditions

To investigate the effect of alternate simulated sea water and acid rain corrosion on the wear resistance properties of wood–plastic composites, sorghum straw fiber-reinforced polyvinyl chloride (SPVC) composites prepared through extrusion molding were studied. The most detrimental alternating corrosion parameters were evaluated with the orthogonal design method, and the samples were then processed considering superimposed corrosion with the worst parameters. The results show that the worst alternating corrosion parameters were: sea water salinity 3.5% × sea water temperature 55 °C + acid rain pH 2.5 × acid rain temperature 55 °C. Longer alternating corrosion periods resulted in worse physical, mechanical, and thermal properties of the SPVC composites, a PVC matrix that was more easily softened in the frictional environment, and fibers more easily pulled-out to form abrasive particles. Debris of broken or pulled-out fibers moving with high-speed in a high-temperature and high-load frictional contact environment can cause severe abrasive wear.     

聚氯乙烯/纳米水滑石复合材料的形态与力学性能

对由原位悬浮聚合制备的聚氯乙烯(PVC)纳米水滑石复合树脂加工得到的纳米复合材料的形态和力学性能进行了研究,并与直接熔融加工得到的PVC纳米水滑石复合材料进行比较.发现由前一方法得到的PVC纳米水滑石复合材料中纳米水滑石的分散性明显优于由后一方法得到的PVC纳米水滑石复合材料,水滑石以初级粒子形式存在,分散良好,无明显团聚体;与之对应,由前一方法得到的PVC纳米水滑石复合材料的力学性能也明显优于由后一方法得到的PVC纳米水滑石复合材料,当纳米水滑石含量小于5wt%时,复合材料的杨氏摸量、拉伸强度和缺口冲击强度均随水滑石含量增加而增大;纳米水滑石的引入可显著提高复合树脂的热稳定性;PVC纳米水滑石复合材料的储能和损耗模量略大于纯PVC材料,而损耗因子和玻璃化温度变化不大.     

Plasma-Assisted Pretreatment of Wheat Straw

O₃ generated in a plasma at atmospheric pressure and room temperature, fed with dried air (or oxygen-enriched dried air), has been used for the degradation of lignin in wheat straw to optimize the enzymatic hydrolysis and to get more fermentable sugars. A fixed bed reactor was used combined with a CO₂ detector and an online technique for O₃ measurement in the fed and exhaust gas allowing continuous measurement of the consumption of O₃. This rendered it possible for us to determine the progress of the pretreatment in real time (online analysis). The process time can be adjusted to produce wheat straw with desired lignin content because of the online analysis. The O₃ consumption of wheat straw and its polymeric components, i.e., cellulose, hemicellulose, and lignin, as well as a mixture of these, dry as well as with 50% water, were studied. Furthermore, the process parameters dry matter content and milled particle size (the extent to which the wheat straw was milled) were investigated and optimized. The developed methodology offered the advantage of a simple and relatively fast (0.5–2 h) pretreatment allowing a dry matter concentration of 45–60%. FTIR measurements did not suggest any structural effects on cellulose and hemicellulose by the O₃ treatment. The cost and the energy consumption for lignin degradation of 100 g of wheat straw were calculated.