聚烯烃／木纤维发泡复合材料的研究进展

本文介绍了聚烯烃／木纤维发泡复合材料中的三种主要的材料——聚乙烯(PE)／木纤维发泡复合材料、聚丙烯(PP)／木纤维发泡复合材料、聚氯乙烯(PVC)／木纤维发泡复合材料的最新研究成果，涉及制备方法、生产工艺、材料结构和性能，以及它们之间的相互影响。     

不同种类木纤维对PE基微孔发泡木塑复合材料的性能影响

采用挤出、注塑成型工艺制备PE基木纤维/塑料微孔发泡复合材料.从不同木纤维的种类对PE基木纤维/塑料微孔发泡复合材料的密度、冲击强度、弯曲强度、拉伸强度进行研究.实验结果表明:以木粉为填料所制得的木塑微孔发泡复合材料密度最佳;竹粉和秸秆粉的冲击强度都优于木粉,且竹粉所制得的复合材料具有最佳的力学性能.     

PVC/木塑复合材料挤出发泡的研究进展

由于木塑复合材料的独特优点,使其需求迅速增长,很多国家正着手建立本国的木塑工业体系。总结了国内外在PVC木/塑复合材料挤出发泡研究上取得的进展,分别从木粉处理、配方、成型工艺及成型设备等关键技术上介绍PVC木/塑发泡复合材料研究取得的成就。并就当前的发展情况,提出了PVC木/塑发泡材料的发展方向。     

PVC／木粉复合材料挤出发泡成型的研究

介绍木塑复合材料挤出发泡成型的发展和加工难点，并针对聚氯乙烯（PVC）／木粉复合材料挤出发泡的成型方法，从原料、配方、工艺、设备等方面作了详细分析。最后简述了PVC／木粉复合材料挤出发泡制品的性能及影响制品性能的主要因紊。     

化工专利

一种微发泡聚苯乙烯基木塑复合材料及其制备方法公开(公告)号:CN101153098公开(公告)日:2008.04.02本发明解决了目前木塑复合材料耐冲击性能差、易于燃烧的问题。本发明由木质纤维材料、偶联剂、增韧剂、润滑剂、聚苯乙烯、发泡剂、助发泡剂、阻燃剂和抑烟剂按质量份混合制成。制备方法为:①热混;②冷却、混合;③挤出成型,即得到微发泡聚苯乙烯基木塑复合材料。本发明的微发泡聚苯乙烯基木塑复合材料具有密度小、阻燃抑烟效果好、耐冲击的优点。     

PVC/木粉复合材料挤出发泡成型的研究

介绍木塑复合材料挤出发泡成型的发展和加工难点,针对聚氯乙烯(PVC)／木粉复合材料挤出发泡的成型方法,从原料、配方、工艺、设备等方面作了详细分析。简述了PVC／木粉复合材料挤出发泡制品的性能及影响制品性能的主要因素。     

木粉对PVC发泡木塑复合材料性能的影响

采用PVC树脂和木粉加入发泡剂制得PVC/木粉发泡复合材料。本文对木粉进行了热重分析,考察木粉粒径及含量对PVC/木塑发泡材料性能的影响,考察了木粉含量对发泡、熔融指数、转矩加工流变性以及耐候性的影响。结果表明:TG分析表明PVC/木塑复合材料加工的最佳温度200℃左右。随着木粉粒径的减小,PVC/木粉复合材料的冲击强度和弯曲强度出现先上升后下降的趋势,100目木粉,力学性能最好。随着木粉用量的增加,体系的拉伸强度、冲击强度和弯曲强度均呈降低的趋势,材料的发泡效果变差,流动性、稳定性、耐候性变差,因此PVC木塑复合材料应该控制其木粉含量。     

PE木塑发泡生产工艺研究

将发泡技术引入了聚乙烯(PE)木塑复合材料的制备过程中,研究了发泡剂种类、发泡剂用量、成核剂及发泡加工工艺等因素对PE木塑复合材料发泡质量的影响;分析了不同发泡条件下,复合材料各项性能的变化.结果表明,采用复合发泡剂、纳米无机成核剂及渐扩法挤出发泡技术可制得泡孔细密、均匀且综合性能较好的发泡木塑复合材料.     

PVC／木粉复合材料用新型偶联剂

木纤维和塑料之间有效的界面粘附对于木塑复合材料的加工和极限性能至关重要。把偶联剂加入木塑复合材料可促进亲水木材表面和憎水聚合物母体之间的粘附。不过，迄今为止还未见报道可明显改善PVC／木纤维复合材料的性能并且成本低的偶联剂。本文报道了使用甲壳质和脱乙酰甲壳质两种天然聚合物作为PVC／木粉复合材料新型偶联剂的研究结果。和未使用偶联剂比较，PVCY木粉复合材料中加入甲壳质和脱乙酰甲壳质偶联剂，挠曲强度增加约20％，挠曲模量增加约16％，储能模量增加约33-74％。使用0．5％（重量）的脱乙酰甲壳质和6．67％（重量）的甲壳质，复合材料的性能会有明显改善。     

木粉填充PVC树脂复合材料力学性能的研究

木塑复合材料主要的发展趋势是木塑复合材料微发泡技术。大型宽幅度较厚的板材制品技术等成套设备及制品成型技术的开发,改善木塑制品应用中存在的诸如密度大、尺寸不能满足实际需要等问题,不断扩大木塑制品的应用领域。通过调节粉料含量的不同、粒径的不同及粉料种类的不同,制备木粉及短纤维/PVC复合材料,进而研究木粉/PVC复合材料的各种性能。实验中粉碎的木屑,在进行实验之前进行烘干,这样有利于实验中对木屑粉碎、筛选。将木粉烘干,除去木屑中可能存在的水分、易挥发成分以及易分解成分,保证加工顺利、制品光亮、色泽正常、制品强度高。随着实验中木粉加入量的增大,复合材料的冲击性能有所下降,木粉含量为45%,冲击性能达到最佳。木粉含量越高,使木塑复合材料的粘结性能和流动性能均变差,因而影响木塑复合材料的拉伸和冲击等力学性能。     

Factors That Affect Diffuse Reflection Performance of Microcellular Foamed Plastics

The structure of microcellular foamed plastics causes optical, acoustic, and electrical properties. The diffuse reflection performance of microcellular foamed plastics can be applied as a high performance diffuse reflector. To improve microcellular foaming process, a simulation was conducted. It was to analyze the factor affecting when microcellular foamed plastics realized the diffuse reflection performance. Cell morphology of microcellular foamed plastics can be expressed through four factors. From result of simulation made a data base about cell morphology and diffuse reflectance. And the statistical method was used for identify contributions by factors.     

CHARACTERIZATION OF MICROCELLULAR FOAMED POLYOLEFIN BLEND COMPOSITES WITH WOOD FIBER

The effects of wood fiber content on the void fraction, cell morphology, and notched Izod impact strength of microcellular foamed HDPE/PP blend composites with wood fiber were studied. The influence of wood fiber content on the carbon dioxide adsorption and desorption in the samples was also examined. Adsorption of carbon dioxide decreased with increased wood fiber content. Gas diffusion rates were faster as wood fiber content increased. The void fraction decreased dramatically when wood fiber was introduced in the blend. Environmental scanning electron microscopy (ESEM) was used to investigate the effects of wood fiber content on cell morphology. The 30:70 HDPE/PP polymer blend without wood fiber resulted in a high void fraction, with a uniform and well-developed microcellular structure, but when wood fiber was introduced, a uniform and well-developed microcellular structure could not be produced. The effects of foaming on Izod impact strength were dependent on wood fiber content.     

Microcellular foam of polymer blends of HDPE/PP and their composites with wood fiber

In this study, the effects of batch processing conditions (foaming time and temperature) and blend composition as well as the effect of incorporating wood fiber into the blends on the crystallinity, sorption behavior of CO₂, void fraction, and cellular morphology of microcellular foamed high‐density polyethylene (HDPE)/polypropylene (PP) blends and their composites with wood fiber were studied. Blending decreased the crystallinity of HDPE and PP and facilitated microcellular foam production in blend materials. The void fraction was strongly dependent on the processing conditions and on blend composition. Foamed samples with a high void fraction were not always microcellular. The addition of wood fiber inhibited microcellular foaming. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2842–2850, 2003     

超临界CO2微孔发泡塑料的研究进展

利用超临界CO2发泡制备微孔发泡塑料是当前的研究热点,具有发泡效率高、绿色环保、对制品的机械性能及外观影响小等优点.综述了超临界CO2微孔发泡塑料的研究进展.介绍了超临界CO2的三种发泡机理:均相成核、非均相成核与外力场加强成核机理.概述了间歇式、半连续式和连续式发泡工艺,阐述了发泡过程中防止泡孔黏结、破裂的方法及发泡...     

Cell morphology and property relationships of microcellular foamed pvc/wood-fiber composites

Wood-fiber composites make use of cellulose fibers as a reinforcing filler in the polymer matrix and are known to have a lower material cost and a higher stiffness than neat polymers. However, the lower material cost and enhanced stiffness of wood-fiber composites are achieved at the expense of other properties such as the ductility and impact strength. Since microcellular plastics exhibit a higher impact strength, higher toughness, and increased fatigue life compared to unfoamed plastics, microcellular foaming of wood-fiber composites will improve the mechanical properties of the composites and therefore increase the usefulness of the materials. In this paper, microcellular foamed PVC/wood-fiber composites with unique cell morphology and material composition are characterized. Microcellular structures are produced in PVC/wood-fiber composites by first saturating the composite samples with CO₂ under high pressure followed by rapidly decreasing the solubility of gas in the samples. The void fraction of the microcellular foamed PVC/wood-fiber composites is controlled by tailoring the composition of materials and the foaming process parameters. The results indicate that tensile and impact properties of microcellular foamed PVC/wood-fiber composites are most sensitive to changes in the cell morphology and the surface modification of fibers.     

微孔发泡注塑技术研究进展

介绍了微孔发泡塑料的定义及优点,阐述并对比了物理微孔发泡和化学微孔发泡等2种微孔发泡注塑成型工艺;详细介绍了近年来微孔发泡注塑技术在工艺优化、开模二次发泡、表面质量改善和力学性能预估等方面的最新研究进展;最后,对微孔发泡注塑技术未来的研究方向进行了展望。     

Investigation on microstructure and properties of foamed (wood fiber)/(recycled polypropylene) composites

Microcellular foamed (wood fiber)‐reinforced recycled polypropylene composites (MFWPCs) were prepared by an injection molding process where azodicarbonamide was used as a chemical foaming agent. The influence of injection parameters (injection temperature, dwell pressure) on the microcellular structure (cell diameter and cell density) and the mechanical properties of the MFWPCs were investigated. The results indicated that when the melting temperature was 180°C and the dwell pressure was 12.5 MPa, a uniformly distributed microcellular structure of MFWPCs was obtained. Compared with solid wood plastic composites, the density of the MFWPCs decreased by 24.5%, and its impact strength of MFWPCs increased by 53%, because the propagation direction of the crack changed to the “skip” or “bifurcation” mechanism as a result of the microcellular structure, and the surrounding matrix of this structure made it easy to produce forced high‐elastic deformation. The toughening mechanism of the microcellular structure was analyzed. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Microcellular Foamed Wood‐Plastic Composites by Different Processes: a Review

Wood fiber reinforced polymer composites represent a relatively small but rapidly growing material class, extensively applied in interior building applications and in the automotive industry. The polymer‐wood fiber composites utilize fibers as reinforcing filler in the polymer matrix and are known to be advantageous over the neat polymers in terms of the materials cost and mechanical properties such as stiffness and strength. Wood fiber reinforced polymer composites are microcellularly processed to create a new class of materials with unique properties. Most manufacturers are evaluating new alternatives of foamed composites that are lighter and more like wood. Foamed wood composites accept screws and nails like wood, more so than their non‐foamed counterparts. They have other advantages such as better surface definition and sharper contours and corners than non‐foamed profiles, which are created by the internal pressure of foaming. This paper represents a review on microcellular wood fiber reinforced polymer composites obtained by different processes (batch, injection molding, extrusion, and compression molding process) and includes an overview of foaming agents (physical and chemical) and the foaming of wood fiber‐polymer composites (changes in phase morphology, formation of polymer‐gas solution, cell nucleation, and cell growth control).

     

微孔发泡聚乳酸/木纤维复合材料的泡孔结构

引言聚乳酸(PLA)因具有环境友好性和降解性而被用于制备不同泡孔结构的泡沫制品[1],然而PLA呈现低的熔体强度和窄的加工窗口,这不利于以超临界流体(如超临界二氧化碳Sc-CO2)发泡制备微孔PLA材料[2-3]。加入填料(如二氧化硅[4]、羟基磷灰石[5]和蒙脱土[6]等)可改善PLA     

A model for the unfoamed skin on microcellular foams

In microcellular plastics, an unfoamed skin that is integral with the foamed core can be created by allowing the nucleating gas to diffuse from the surfaces of a gas saturated specimen prior to foaming. In this paper, a semi-empirical model is proposed that predicts the skin thickness variation in microcellular foams as a function of gas desorption time. The model shows good agreement with experimental results on the polycarbonate–carbon dioxide system.