RTM成型玻璃纤维增强阴离子聚合尼龙6复合材料及其性能

针对己内酰胺阴离子聚合反应特性,通过自行设计的适合该反应体系的树脂注射成型机和搭建的热塑性树脂传递模塑(T-RTM)成型实验平台,在恒压注射条件下,成功地制备了玻璃纤维(GF)体积分数高达48vol％的GF增强阴离子聚合尼龙6(APA-6)复合材料.研究了不同进料方式和压力、模具温度和纤维含量等工艺条件对GF/APA-...     

苎麻纤维增强原位阴离子聚合尼龙6复合材料的制备及性能研究

以己内酰胺为单体,经热处理的苎麻纤维(RF)为增强材料,采用真空辅助树脂传递模塑成型工艺(VARTM)成功制备了苎麻纤维增强原位阴离子聚合尼龙6(APA6)复合材料。主要研究了热处理前后苎麻纤维表面官能团、结晶性能、力学性能和微观形貌的变化,并对复合材料的冲击断面、力学性能和热性能进行了考察。研究表明:当热处理温度为280℃时,苎麻纤维表面的羟基数量显著减少,结晶度略有降低,拉伸强度和模量有所下降,但苎麻纤维的形貌未有明显变化。RF/APA6复合材料中苎麻纤维与树脂的界面结合良好,与APA6相比,复合材料的拉伸强度略有提高,拉伸模量和弯曲性能得到明显提升,同时热稳定性显著提高。     

阴离子原位聚合碳纤维增强尼龙6界面的研究

碳纤维表面可接枝上高聚物活性官能团,以调节复合材料中纤维与树脂之间的界面效应,从而改善复合材料的性能,通过控制接枝高聚物的结构可以很好的设计具有预定性能的界面层。热处理对纤维的强度不会造成影响,其表面官能团含量在1h附近达到最大值。未经异氰酸酯接枝处理的碳纤维表面没有聚合接枝尼龙大分子,热处理后再经过异氰酸酯处理,能明显看到尼龙分子接枝到纤维表面。当聚合单体中不添加活化剂,纤维表面的树脂接枝率可达到18.8%;单体中添加0.003的活化剂(占单体摩尔比),碳纤维表面的尼龙6接枝率只有7.65%,这是单体基体与纤维界面反应竞争的结果。碳纤维表面对原位聚合生成的尼龙以及改性尼龙结晶有很大影响,碳纤维未接枝处理时表面形成的横晶比较少;碳纤维接枝处理后可以看见纤维附近存在大量晶体结构,结晶体密度高,有利于材料性能改良。     

碳纤维增强尼龙复合材料渗透模型的研究

建立了热塑性树脂熔体渗透浸渍纤维的理论模型,由此表征了工艺参数、熔体黏度和纤维结构对浸渍时间的影响规律.结果表明,熔融尼龙树脂复合材料的理论纤维体积率很难达到70%以上.采用原位聚合方法能使尼龙树脂熔体黏度降低几个数量级,并能提高树脂基体熔体对纤维的浸渍效率.     

天然纤维增强阴离子聚合尼龙6复合材料的加工与性能EI北大核心CSCD

采用真空辅助树脂传递模塑(VARTM)法制备了天然纤维增强阴离子聚合尼龙6(APA-6)复合材料,并将其与玻璃纤维复合材料进行比较。首先对天然纤维进行预处理,然后对反应加工过程进行优化,选取了低活性和弱碱性的己内酰胺溴化镁(C1)作为引发剂,制备得到天然纤维复合材料。采用差示扫描量热仪分析了样品的结晶度,结果显示,天然纤维复合材料有更高的结晶度。扫描电镜观察2种复合材料的界面情况表明,天然纤维复合材料有更好的界面性能。对纯APA-6及其复合材料的弯曲性能和拉伸性能测试表明,天然纤维的加入使材料的力学性能有了较大幅度的提高,并且拥有较高的比强度和比模量。     

短切碳纤维增强尼龙66复合材料注塑成型工艺模拟

采用毛细管流变仪和自制小型模具,对不同质量分数的短切碳纤维增强尼龙66(CF/PA66)复合材料颗粒进行了熔体流动性能分析和注塑成型工艺模拟,实现少量原料快速模拟CF/PA66的注塑成型工艺参数。研究表明:短切CF/PA66复合材料的熔体属于幂律流体,熔体黏度随温度、压力和CF质量分数变化显著,当温度和压力升高到临界值后熔体流变特性从假塑性区进入牛顿区;随着CF质量分数的增加,CF/PA66复合材料适宜成型温度提高。实验中PA66、CF质量分数为10wt%和20wt%的CF/PA66三种颗粒的适宜成型温度分别为278~285℃、280~287℃、290~298℃,通过对熔体进行Bagley压力校正,三种颗粒适宜成型的最小注塑压力分别为24.3MPa、29.4MPa、35.1MPa;将流变仪模拟所得参数应用于注塑成型工艺,所得样品的拉伸强度与流变仪制备的试样非常接近,进一步说明了毛细管流变仪模拟CF/PA66注塑成型过程的可行性和有效性,为其注塑成型工艺条件提供了理论依据。     

阴离子聚合尼龙6的改性研究进展

介绍了阴离子聚合尼龙改性的研究发展,重点介绍了阴离子聚合尼龙6的填充和共聚改性研究,并规纳最新动向及发展趋势。     

苎麻纤维增强原位阴离子聚合尼龙6复合材料的制备及性能研究

以己内酰胺为单体,经热处理的苎麻纤维(RF)为增强材料,采用真空辅助树脂传递模塑成型工艺(VARTM)成功制备了苎麻纤维增强原位阴离子聚合尼龙6(APA6)复合材料.主要研究了热处理前后苎麻纤维表面官能团、结晶性能、力学性能和微观形貌的变化,并对复合材料的冲击断面、力学性能和热性能进行了考察.研究表明:当热处理温度为280℃时,苎麻纤维表面的羟基数量显著减少,结晶度略有降低,拉伸强度和模量有所下降,但苎麻纤维的形貌未有明显变化.RF/APA6复合材料中苎麻纤维与树脂的界面结合良好,与APA6相比,复合材料的拉伸强度略有提高,拉伸模量和弯曲性能得到明显提升,同时热稳定性显著提高.     

阴离子原位聚合尼龙6/ABS合金的研究

采用HDI缩二脲封端端羟基丁腈橡胶预聚物,制备大分子橡胶改性活化剂,以氢氧化钠为催化剂,选择不同配比的ABS树脂加入熔融己内酰胺单体中,确定聚合温度为160℃~180℃,通过阴离子聚合制得ABS/PA6共混物。耐水性和吸水后力学性能分析得知,合金共聚物吸水率比纯PA6明显降低,合金吸水后力学性能有不同程度的降低,但吸水后力学损失量比纯PA6低很多。电镜测试表明原位反应增容因PA6与ABS两相界面张力降低,使ABS分散颗粒变小并更均匀地分散于PA6中。     

聚醚砜／MC尼龙6原位复合材料的制备和性能

用阴离子原位聚合法制备聚醚砜／MC尼龙6原位复合材料,研究了聚醚砜与已内酰胺、尼龙6各组分之间的相互作用．结果表明,依靠其组分之间强烈的作用力,使PES能以较小的相畴均匀的分散在尼龙6基体中;酰胺基团上的氢原子能与聚醚砜中的砜基之间产生氢键作用,从而促进了聚醚砜在已内酰胺熔体中的溶解．聚醚砜与尼龙6之间的这种氢键互作用,强烈抑制了尼龙6的分解过程,提高了复合材料的热稳定性,2％PES时,其分解温度提高了79℃．较小含量的PES对复合材料的力学性能影响较小,当其含量超过4％时,尽管复合材料的强度有所下降,但韧性显著提高,体现了刚性有机粒子增韧的作用．     

Polyamide-6/vegetal fiber composite prepared by extrusion and injection molding

The interest for the use of vegetal fibers as polymers reinforcement has recently increased because of their unique environmental and technological advantages. This work evaluated the use of Curauá fibers in polyamide-6 composites aiming at glass fiber replacement. Fiber content of 20, 30 or 40 wt% and fiber lengths of 0.1 or 10 mm were studied. Fibers were treated with N₂ plasma or washed with NaOH solution, to improve their adhesion to PA-6. Samples with 20 wt% of short or long fibers, with or without pre-treatment, were compounded in two different co-rotating intermeshing twin-screw extruders. These samples were submitted to mechanical and thermal tests. In conclusion, non-dried raw materials improved fiber/matrix interfacial adhesion. Tensile and flexural properties of this composite are better than unfilled, but lower than glass fiber reinforced polyamide-6. However, its impact resistance and heat deflection temperature are similar to the glass fiber reinforced polyamide-6 and its lower density, enable it to replace this latter in specific non-critical applications.     

The fracture energy and acoustic emission of a short carbon fiber reinforced nylon 66 composite

Two knee points which are found in the cumulative plotting of acoustic emission (AE) events on a semi-log sheet in a monotonically increasing tensile load system of the center notched carbon fiber reinforced nylon 66 composite (FRTP) are applied to the estimation of the energy value required for the beginning of the stable crack propagation, the one for the stable crack propagation and also the one for the final fracture. They have been examined with regard to the dependence of some mechanical properties of the material on the gauge length, the fiber content and the crack length to width ratio of the specimen. Correlations between the AE characteristic nature such as AE activity (the number of AE events per unit area) and the above energy values are also investigated with regard to the results of the fractographic measurement of the fracture surface. It has been found that the energy required for the stable crack propagation decreases with an increase in the crack length to width ratio and increases with an increase in the gauge length. However, for an unstable crack propagation, it decreases with an increase in the fiber content. The dependence of the energy value on crack length to width ratio disappears in the results for a 30% specimen and this value becomes constant.     

有一定取向性的碳纤维增强尼龙6复合材料弹性模量的实验和理论研究

纤维增强热塑性聚合物基复合材料注塑成型后往往被认为是各向同性复合材料。然而,注塑成型后纤维会具有一定的取向性,从而使复合材料试样呈现各向异性的特点。为了合理预测此类复合材料的弹性模量,本文对碳纤维增强尼龙6复合材料注塑试样内部的纤维长度和取向分布情况进行了测试和分析,得出了纤维取向的分布规律。随后结合单向纤维增强聚合物基复合材料力学模型和层叠理论,构造出了适用于有一定取向性的纤维增强树脂基复合材料弹性模量预测理论模型,其理论结果和拉伸实验结果吻合较好,表明该预测模型的准确性比较高。      

Effects of moisture and UV exposure on liquid molded carbon fabric reinforced nylon 6 composite laminates

Liquid molding of thermoplastics has been limited by high resin viscosity, high temperature processing requirements, and a short processing window [Sibal PW, Camargo RE, Macosko CW. Designing nylon 6 polymerization for RIM. In: Proceedings of the second international conference on reactive processing of polymers, Pittsburgh, PA; 1982, p. 97–125.]. The processing parameters for vacuum assisted resin transfer molding (VARTM) developed by the authors and previously reported [Pillay S, Vaidya UK, Janowski GM. Liquid molding of carbon fabric-reinforced nylon matrix composite laminates. J Thermoplast Compos Mater 2005;18:509–27] have been adapted to process carbon/nylon 6 composite panels. The present work addresses the effects of moisture and ultraviolet (UV) exposure on the static and dynamic mechanical properties of carbon fabric reinforced, thermoplastic polyamide 6 matrix panels processed using VARTM. The Bao and Yee dual diffusivity model [Bao LR, Yee AF. Moisture diffusion and hygrothermal aging in bismaleimide matrix carbon fiber composites: Part II – Woven and hybrid composites. Compos Sci Technol 2002;62:2111–9] was applied to evaluate the moisture uptake for the C/PA6, fully immersed in distilled water at 100 °C. SEM results show that moisture exposure result in surface micro-cracks compromise of the fiber–matrix interface. The flexural strength is lowered by 45%, after exposure to moisture at 100 °C. UV exposure up to 600 h causes yellowing of the samples and an increase in crystallinity from 40% to 44%.     

Development of slate fiber reinforced high density polyethylene composites for injection molding

During the last decade the use of fiber reinforced composite materials has consolidated as an attracting alternative to traditional materials due to an excellent balance between mechanical properties and lightweight. One drawback related to the use of inorganic fibers such as those derived from siliceous materials is the relative low compatibility with conventional organic polymer matrices. Surface treatments with coupling agents and the use of copolymers allow increasing fiber–matrix interactions which has a positive effect on overall properties of composites. In this research work we report the use of slate fiber treated with different coupling agents as reinforcement for high density polyethylene from sugarcane. A silane (propyltrimethoxy silane; PTMS) and a graft copolymer (polyethylene-graft-maleic anhydride; PE-g-MA) were used to improve fiber–matrix interactions on HDPE-slate fiber. The effect of the different compatibilizing systems and slate fiber content were evaluated by scanning electron microscopy (SEM), dynamic thermomechanical analysis (DTMA) as well as mechanical properties (tensile, flexural and impact). The results show that the use of silane coupling agents leads to higher fiber–matrix interactions which has a positive effect on overall mechanical properties. Interesting results are obtained for composites containing 30 wt.% slate fiber previously treated with propyltrimethoxy silane (PTMS) with an increase in tensile and flexural strength of about 16% and 18% respectively.     

注塑成型纤维增强热塑性树脂复合材料刚度预测方法

基于Hsueh模型的应力场分布,采用代表性体积单元(RVE)平均近似方法,推导出可以退化成Halpin-Tsai模型的泊松比v12的显性表达式,与桥联模型基本重合.结合Fu模型和Giner模型,引入与纤维长径比(l/a)相关的指数衰减函数得到横向模量E22修正的Halpin-Tsai模型,与自洽模型重合.基于泊松比各向...     

Creep properties of fatigued short carbon fibre reinforced nylon 6 plastics

The effect of low-cycle fatigue on the creep properties of a fibre-reinforced thermoplastic has been examined from the standpoint of the stress dependence and cycle ratio, which is the fraction of the mean life cycles to fracture. The time dependence of the strain and the strain rate of a virgin specimen can be described by a straight line on a logarithmic scale, therefore the deformation process seems to be ruled by a flow law. In addition the time dependence of the strain rate does not indicate the stress dependence for each stress level, which shows the same value as in the gradient of these relations. In the case of fatigued specimens, however, a knee point which divides the creep process into a primary region and a secondary one appears in the creep relation. The gradient in the primary region is less than that for the virgin material, and the magnitude and the timing of its appearance show either a stress dependence or a cycle ratio dependence. A weak stress dependence of the relation for log against logt can also be found; however, the results do not indicate a dependence on the cycle ratio. The reason for these results and the relationship of the structural changes of the materials are discussed using a McLean model.     

碳纤维增强聚苯硫醚复合材料激光加热原位成型过程中的温度场

连续纤维增强热塑性复合材料（Thermoplastic Composite,TPC）自动铺放（Automated Fiber Placement,AFP）可以实现铺层原位成型,因此在制造大型结构件、降低加工成本及提升生产效率方面潜力巨大。原位成型过程中铺层温度场分布对复合材料构件成型质量具有较大影响,且激光加热过程中又涉及激光能量场与预浸料吸收光能后产生的温度场之间相互耦联,机理复杂,因此结合传热模型,通过有限元模拟仿真研究激光辅助加热自动铺放成型连续碳纤维增强聚苯硫醚（CF/PPS）复合材料过程中铺层经历的温度历程。同时构建铺层温度场测量系统,对铺层经历的温度历程进行实时采集和存储。研究结果表明,铺放过程中黏合区域前方存在激光辐照阴影区,使压辊下方黏合区域的温度急剧下降;随着铺放速度的增加,黏合区域峰值温度逐渐降低,且成型速度越快,铺层间黏合区域峰值温度差越小,而热电偶测量结果与仿真结果相差越大;随着激光输出功率的增大,铺层峰值温度逐渐升高;为提高原位成型效率,当激光输出功率选择最大6kW时,最大铺放速度为0.75 m/s。通过对比,试验结果中的峰值温度与仿真模拟结果变化趋势相近,证明了有限元仿真模型的正确性。