加工条件对芳纶/PP复合材料横向拉伸性能的影响

本文主要对芳纶 /聚丙烯混纤复合材料的横向拉伸性能进行了研究 ,讨论了不同的加工条件 (成型温度、时间、压力 )以及芳纶的体积含量等对复合材料体系横向拉伸强度的影响     

纳米蒙脱土对木粉/聚丙烯复合材料发泡性能的影响

采用高压釜间歇式发泡法,结合超临界CO2微孔发泡技术制备了发泡木粉-纳米蒙脱土(NMMT)/聚丙烯(PP)复合材料.通过对复合材料的结晶行为、流变性能、泡孔形貌及压缩性能进行分析,主要研究了NMMT对其微孔结构及力学性能的改善作用.结果 表明:NMMT的引入使木粉/PP复合材料中PP基体的结晶速率加快,结晶度减小,有利...     

Study of the effective parameters on mechanical and electrical properties of carbon black filled PP/PA6 microfibrillar composites

In this study the electrical and mechanical properties of microfibrillar polypropylene (PP)/polyamide6 (PA6) blend filled with super conductive carbon black (CB) have been investigated. In situ microfibrillar PP/PA6 composites filled with CB are produced using a single screw extruder equipped with a spinneret. Glycidyl methacrylate (GMA) grafted polypropylene (PP-g-GMA) is used as the compatibilizer. To investigate the effects of extensional flow on the microstructure, electrical and mechanical properties, three adaptors with various convergence angles were designed, prepared and applied between the extruder and the spinneret. To optimize the effects of processing and material parameters on the electrical and mechanical properties, the Taguchi method of experimental design is used. Material and processing factors which are studied include: concentration of PA6, compatibilizer level, CB concentration, drawing speed of melt spinning line, adaptor angle, order of mixing and temperature profile along the extruder. The results show an increase in DC conductivity of up to 10¹¹ times in comparison with pure PA6, by increasing the concentration of CB, drawing speed, adaptor angle and optimizing other parameters. By optimizing processing and material factors studied here, strength of microfibrillar structured composites is increased of up to 80% in comparison to pure PP.     

Effect of graphene oxide nanosheets on the physico-mechanical properties of chitosan/bacterial cellulose nanofibrous composites

In this work, novel chitosan/bacterial cellulose (CS/BC) nanofibrous composites reinforced with graphene oxide (GO) nanosheets are introduced. As cell attachment and permeability of nanofibrous membranes highly depend on their fiber diameter, the working window for successful electrospinning to attain sound nanofibrous composites with a minimum fiber diameter was determined by using the response surface methodology. It is shown that the addition of GO nanosheets to CS/BC significantly reduces the average size of the polymeric fibers. Their mechanical properties are also influenced and can be tailored by the concentration of GO. Fourier transform infrared spectroscopy reveals hydrogen bonding between the GO nanosheets and the polymer matrix. A decrease in the hydrophilicity of the electrospun nanofibers and their water vapor permeability with the addition of GO are also reported. The prepared nanofibrous composites are potentially suitable candidates for biomedical applications such as skin tissue engineering and wound dressing.     

石墨烯微片/聚丙烯导热复合材料的制备与性能

通过熔融共混法制备了两种不同型号石墨烯微片（GNPs）填加的GNPs/聚丙烯（PP）导热复合材料,研究了GNPs型号（KNG180,KNG150）和含量对其导热性能、密度、结晶性能和热稳定性能的影响。结果表明,KNG180 GNPs/PP复合材料密度高于KNG150 GNPs/PP,同时KNG180对提高聚丙烯结晶度的效果优于KNG150。随着石墨烯微片含量的增加,两种复合材料导热系数均明显增大,而且KNG180填充的复合材料导热性能明显优于KNG150;当KNG180的添加量为60%（质量分数）时,GNPs/PP复合材料的导热系数从纯聚丙烯的0.087 W/（m·K）提高到1.32 W/（m·K）,提高了14倍多。石墨烯微片的加入显著提高了聚丙烯的热稳定性,当KNG180或KNG150的质量分数为10%时,聚丙烯达到最大热失重速率时的温度从345.1 ℃分别提高到374.6 ℃和397.9 ℃,但是当石墨烯微片超过一定含量时,热稳定性会下降。     

PET-MFIAA/ PP原位成纤复合材料的形态结构及力学性能

用钉挂预埋多功能界面活化剂(MFIAA)的PET(PET-MFIAA)与PP共混 - 挤出 - 拉伸,制备了PET-MFIAA/PP原位成纤复合材料,采用扫描电镜、偏光显微镜观察和力学性能测定的方法,研究了PET-MFIAA/PP的PET微纤形态、试样断面形态及力学性能,并与PET/PP、MFIAA/PET/PP两种原位成纤复合材料进行对比。结果表明: PET-MFIAA/PP PET微纤与PP基体间具有强的相互作用,PET微纤呈粗细不均匀、凹凸不平的异形形态及柔性界面等结构特征,形成了强的界面结合,其刚性、韧性均比纯 PP明显提高,含7.00% MFIAA的PET-MFIAA/PP复合材料的拉伸屈服应力、弯曲弹性模量和悬臂梁缺口冲击强度分别达到了纯PP的1.04倍、1.23倍和1.79倍。     

Mechanical properties of textile-inserted PP/PP knitted composites using injection–compression molding

This paper concentrates on the experimental investigation of the self-reinforced all-polypropylene composites. There exists an optimum processing condition to produce high quality specimens by injection–compression molding. Tensile and 3-point bending properties of the virgin PP materials were nearly unaffected by the introduction of reinforcing knit layer(s) due to very low fibre content of the knitted fabrics used. 3-point bending properties were also unaffected by the surface of indentation-flexure. The applied impact energy was maintained at 5 J for the homo-PP and 27 J for the block-PP materials, respectively, to cause penetration during drop-weight impact tests. It is interestingly noteworthy that the self-reinforced homo-PP composites exhibited superior energy absorption capability when compared with the virgin matrix materials. The corresponding plate bending performances of the self-reinforced homo-PP composites also revealed consistent improvement as compared to their virgin counterparts. On the other hand, although virgin block-PP material exhibited better impact performances than its composite reinforced by the homo-PP knitted fabric, a notably small increase in the reinforcement fibre content revealed considerable improvement in the impact properties comparable to those of the virgin block-PP matrix materials. These self-reinforced homo-PP/block-PP materials have clearly indicated that they have the potential to out-perform the block-PP materials via modification and/or manipulation of the reinforcement knit structural/geometrical parameters and the content of reinforcement fibres. Both static and dynamic impact properties are likely to be affected by the local area properties of the tested face under indentation, and thereby contributing to the improved performances of the composite specimens with the knit face under the impact.     

Influence of foaming process on the structure–properties relationship of foamed LDPE/silica nanocomposites

In this paper LDPE/silica nanocomposites are foamed by two different processes. First one is the pressure quench method which is based on the use of a physical blowing agent and second one is the improved compression moulding technique. As the latter process uses a chemical blowing agent, both types of foamed nanocomposites will provide very useful information about the relationship between foaming process-microstructure and macroscopic properties. Results have revealed how silica nanoparticles are able to act as nucleating sites during foaming step in both processes; however, the optimum amount of particles strongly depends on the foaming route. Thermal and mechanical properties of solid and foamed nanocomposites have been analyzed by means of thermogravimetric analysis and compression tests. Results have revealed that nanosilica particles act as effective nucleating agents, not only reducing cell size and increasing cell density but also achieving more homogeneous cellular structures. Thermal and mechanical properties are improved due to the presence of silica nanoparticles. It has been found that the improvement degree reached for samples produced using chemical blowing agents is greater than that achieved for samples produced using physical blowing agents.     

Transcrystallisation in PP/flax composites and its effect on interfacial and mechanical properties

The effect of flax fibre reinforcement on the crystallisation behaviour of polypropylene (PP) was investigated using a hot-stage polarising optical microscope. To follow the crystallisation kinetics, crystallisation temperature and time were varied. At crystallisation temperatures between 130 and 138 °C the most uniform and thickest transcrystalline layers were formed. The effect of transcrystallisation on the interfacial shear strength (IFSS) in micro-composites was studied by the fibre pull-out test method. It was found that the IFSS of the PP/flax system is slightly decreased with the presence of a transcrystalline interphase. Finally, the influence of the formation of a transcrystalline zone on the macromechanical properties of compression moulded PP/flax composites was studied.     

Effects of processing methods and parameters on the mechanical properties and microstructure of carbon/carbon composites

The influence of the fabrication parameters during carbonization and densification processes on the mechanical properties and the microstructure of carbon/carbon (C/C) composites were investigated. The C/C composites were made by using phenolic resin as precursor and two-dimensional carbon fabrics as reinforcements for the first carbonization. The effects of heating rate and heat-treatment temperature during the initial carbonization process on the properties of C/C composites are presented. Further densification treatment was completed by chemical vapour infiltration (CVI) and a liquid-resin impregnation process. The CVI route was found to be more efficient than the resin-impregnation process. The interlayer spacing of C/C composites did not change after resin re-impregnation for several times. However, the interlayer spacing of the C/C composites was reduced when the processing temperature in the CVI process was increased. Higher flexural strength and flexural modulus were obtained because the densities of the composites were enhanced either by the chemical vapour infiltration process or by the resin-impregnation route. The variation in thickness of the CVI deposited carbon within the preformed composite was studied and the morphology of the fracture surface of the C/C composites was also examined.     

PP/PP-g-MAH/MMT纳米复合材料微孔发泡的研究

通过熔融共混法制备聚丙烯/马来酸酐接枝聚丙烯/蒙脱土(PP/PP-g-MAH/MMT)纳米复合材料母粒。利用"二次开模"法注塑成型制得PP/PP-g-MAH/MMT纳米复合微孔发泡材料。研究了MMT和PP-g-MAH的用量对纳米复合微孔发泡材料发泡质量的影响。结果表明:5%的MMT和6%的PP-g-MAH有较好的协同效应,微孔发泡材料发泡倍率最大,泡孔平均直径最小,泡孔密度较大,泡孔尺寸分布范围较窄。     

PP镁盐晶须复合材料的性能研究

研究了镁盐晶须填充改性聚丙烯(PP)材料的力学性能以及PP-g-MAH和PP-g-GMA为相容剂对复合材料的影响等.结果表明:镁盐晶须能明显改善PP材料的拉伸强度、弯曲强度和弯曲模量等力学性能;PP-g-MAH和PP-g-GMA作为相容剂改善镁盐晶须对PP的增韧补强作用.     

Novel manufacturing process for improving mechanical properties of flax/PP composites

Many attempts have been made in the recent past to improve the mechanical properties of flax/polypropylene (PP) thermoplastic composites. Most of these attempts have not been translated at industrial level due to additional chemical treatment process involved. In the present work, needle-punched nonwoven preforms which can be readily used for composite manufacturing was prepared. To improve the interfacial bonding of the composites, a new modified route for composite preparation is proposed. The modified processing strategy implemented to produce flax with polypropylene composite using compression molding machine. The nonwoven preforms were heated to elevated temperatures followed by quenching. The composite samples were then hot consolidated and their mechanical properties were studied and compared with the samples produced by the conventional method. 154, 75, 37, and 9.6% of improvement have been observed for peel strength, compressive strength, hardness, and impact strength, respectively. The reasons for the improvement are discussed in detail using various analytical tools.     

Surface modification of wood flour and its effect on the properties of PP/wood composites

The surface of wood flour used as reinforcement in PP/wood composites was successfully modified by benzylation in NaOH solution of 20 wt% concentration at 105 °C. The time of the reaction was changed between 5 and 360 min in several steps. The progress of modification was followed by the measurement of weight increase and by diffuse reflectance infrared spectroscopy (DRIFT). The structure of the wood was characterized by X-ray diffraction (XRD) and its surface tension was determined by inverse gas chromatography (IGC). PP composites containing 20 wt% filler were prepared from a PP block copolymer and the modified wood flour. The mechanical behavior of the composites was characterized by tensile testing. The majority of the active hydroxyl groups at the surface were replaced by benzyl groups in about 2 h under the conditions used. Further increase in reaction time did not influence the properties of the filler. Both the structure of the wood flour and its surface tension changed as an effect of modification. The reduction of surface tension led to significant changes in all interactions between the wood flour and other substances resulting in a considerable decrease of water absorption, which is the major benefit of this modification. All measured mechanical properties of the composites decreased slightly with increasing degree of modification. A detailed analysis of the results proved that the dominating micromechanical deformation process of these PP/wood composites is debonding, which is further facilitated by the decrease in the surface tension of the filler. Chemical modification of wood flour slightly improved processability and the surface appearance of the composites prepared with them and considerably decreased the water absorption of these latter.     

Effect of interfacial interaction on morphology and mechanical properties of PP/POE/BaSO4 ternary composites

Ternary composites of Polypropylene (PP)/ethylene-octene copolymer (POE)/Barium Sulfate (BaSO₄)(PP/POE/BaSO₄) were prepared through a two-step process: BaSO₄ master-batches were first prepared through blending of BaSO₄ and POE, then blending with PP. Two families of phase structure were confirmed through SEM and DSC, depending on their interfacial interaction. Separation of POE and BaSO₄ filler was found when untreated or titanate coupling agent treated BaSO₄ filler were used. Encapsulation of BaSO₄ particles by POE elastomer was achieved by using BaSO₄ master-batch prepared through reactive blending of BaSO₄ with POE in the presence of maleic anhydride (MAH) and dicumyl peroxide (DCP). The mechanical properties of the composites greatly rely on the morphology. The yield strength and the impact toughness of a composite with core-shell morphology are higher than those of composites with separated morphologies, but the former has lower flexural modulus and elongation at break than the latter. The interfacial interaction was evaluated by semi-empirical equations developed previously. The deformation and toughening mechanisms of the composites were also investigated.     

Influence of fiber length on the mechanical properties of wood-fiber/polypropylene prepreg sheets

Natural fiber based composites have the potential to improve the mechanical properties of plastics while reducing the cost and weight. This study shows a practical method of blending natural-fiber with polypropylene to form a mat and then consolidated into a sheet by hot pressing. The natural fibers assessed were Pinus radiata and Eucalyptus regnan high temperature thermomechanical pulps and sisal (Agave sisalana) fibers. The tensile strength was shown to decrease with an increase in fiber content, while the tensile modulus was shown to increase. Tensile and flexural modulus were positively influenced by fiber length. The water performance tests of the sheets generally showed approximately 20% weight gain and approximately 3% thickness swell at 30% fiber content. The natural fiber surface chemical composition was determined by X-ray photoelectron spectroscopy and shown to be primarily covered with hydrophobic material such as lignin and extractives, while polypropylene was shown to be partially oxidized. Received: 18 September 2000 / Reviewed and accepted: 20 September 2000     

炭黑/聚氨酯泡沫导电复合材料的开发

制备了以聚氨酯软泡为基体的炭黑 /聚氨酯泡沫导电复合材料 ,研究了炭黑的用量及交联剂、扩链剂、偶联剂等助剂对复合材料电学及力学性能的影响。