PP/PET原位成纤复合材料的增强效应

用挤出-拉伸-注塑法制得了PP/PET原位成纤增强复合材料,以不拉伸的普通共混材料作对照,研究了PET质量含量(C_m)对PET成纤性和材料拉伸强度(σ_t)及模量(E)的影响及其作用机制。结果表明,C_m由0增至20%时,PET纤维数量增多,纤维直径及其分散性以C_m=15%为界先减少后增大;材料的σ_t、E在C_m=15%时有最大值,分别比纯PP提高约20%和70%。熔体拉伸时分散相液滴的聚结-形变成纤对PET相形态随C_m的变化起关键作用,分散相对基体增强效应与两相界面缺陷效应的相互竞争,纤维对基体增刚作用受纤维数量和细度的双重控制,分别是决定材料σ_t~C_m、E~C_m关系的支配因素。     

生物可吸收性甲壳素纤维增强聚(ε-己内酯)复合材料的动态流变特性研究

用短切甲壳素纤维增强聚(ε-己内酯)(PCL)制备出新型生物可吸收复合材料,通过高级流变扩展系统(ARES)对不同纤维含量(C_f)的复合材料熔体进行了动态流变特性的研究。结果表明:纤维含量的增加可以明显提高复合材料熔体的复数模量(G*)和复数粘度(η*)。当C_f从45%增加到55%时,复合材料熔体在低频区出现了明显的类似于力学性能的"屈服行为",即G*不再随频率的改变而变化,同时材料的弹性(G')要明显高于粘性(G″)。这种行为可能与纤维在熔体内形成刚性的粒子网络有关,对材料的加工成型不利。从双对数坐标下的G'~G″曲线和η″~η'来看,纤维的加入明显提高了熔体的弹性,延长了熔体的主松弛时间。     

表面改性对Cf/HA-PMMA混杂生物复合材料的结构及性能的影响

采用原位合成与溶液共混相结合的方法,制备了短切碳纤维(C_f) 增强纳米羟基磷灰石(HA)-聚甲基丙烯酸甲酯(PMMA)生物复合材料。重点研究了短切碳纤维和纳米HA粒子表面改性前后对C_f/HA-PMMA复合材料微观结构和力学性能的影响。采用XRD、FTIR、XPS和SEM等对纳米HA粒子、碳纤维和复合材料的组成结构及断面的微观形貌等进行测试和表征,使用万能材料试验机测试其弯曲、压缩性能。结果表明：经表面氧化的碳纤维和用卵磷脂改性后的纳米HA与PMMA基体的界面结合性明显得到改善;采用卵磷脂表面改性后的纳米HA及表面预氧化后的碳纤维制备的C_f/HA-PMMA复合材料的弯曲性能得到显著提高,与采用未表面改性纳米HA和未表面氧化碳纤维所制备的C_f/HA-PMMA复合材料相比,弯曲、压缩强度和弹性模量分别提高1.6倍、2倍和4.3倍。     

热模压辅助先驱体浸渍裂解制备Cf/SiC复合材料研究

以聚碳硅烷为先驱体,采用热模压辅助先驱体浸渍裂解工艺制备3D-B C_f/SiC复合材料,研究了热模压辅助对3D-B C_f/SiC复合材料致密度和力学性能的影响。结果表明:先驱体浸渍裂解制备陶瓷基复合材料第一次浸渍后引入高温热模压工艺可以改善材料微观结构,显著提高材料的致密度和力学性能。其中1600℃,10MPa,1h下热模压辅助先驱体浸渍裂解6次制备的3D-B C_f/SiC复合材料的密度为1.79g/cm3,弯曲强度高达672MPa,断裂韧性达18.9MPa·m1/2,剪切强度接近50MPa,且具有较好的抗热震性和高温抗氧化性。     

先驱体硅树脂高温连接Cf / SiC 复合材料——-惰性及活性填料对连接性能的影响

对先驱体硅树脂高温转化陶瓷接头连接C_f / SiC 复合材料进行了研究。探讨了硅树脂固化裂解过程、惰性及活性填料对连接性能的影响。研究表明, 硅树脂的交联固化主要通过消耗Si —OH 来完成。适当加入惰性填料SiC(5 % ,质量分数) 或活性填料(纳米Al 、Si 粉) 可以大幅度提高硅树脂对C_f / SiC 复合材料的连接性能。     

化学气相浸渗2D Cf/(SiC-C)复合材料的微观结构与强韧性

采用等温等压化学气相浸渗法(ICVI)制备了二维碳纤维增韧碳化硅碳二元基复合材料(2D C_f/(SiC-C)).利用扫描电镜(SEM)和背散射电子成像(BSE)研究了其基体的微观结构, 并与二维碳纤维增韧碳化硅陶瓷基复合材料(2D C_f/SiC)比较了室温力学性能和断口形貌.结果表明：2D C_f/(SiC-C)复合材料的基体是由SiC与热解碳(PyC)组成的多层结构, PyC基体层分布均匀而连续, 且与SiC基体层结合紧密.纤维束内部PyC基体层较厚的2D C_f/(SiC-C)复合材料具有较高的强韧性, 其拉伸强度、断裂应变、断裂韧性和断裂功分别比2D C_f/SiC复合材料的提高了3%、142%、22%和58%.SiC与PyC组成的多层基体使2D C_f/(SiC-C)复合材料的纤维在拔出过程中发生了两次集中拔出, 且第一次集中拔出的纤维对复合材料的强韧性起主要作用.     

氧化铝体积分数对Al2O3f+Cf/ZL109混杂复合材料干滑动摩擦磨损行为的影响

利用挤压铸造法制备了Al₂O_3f+C_f/ZL109短纤维混杂金属基复合材料,并探讨了Al₂O₃纤维对该混杂复合材料干滑动摩擦磨损行为的影响。结果表明:混杂复合材料的摩擦系数以及从轻微磨损到急剧磨损转变的临界载荷均随着Al₂O₃体积分数的增加不断增大。在轻微磨损阶段,复合材料的主要磨损机制为犁沟磨损和层离,且Al₂O₃体积分数为12%时混杂复合材料的磨损率最低。发生严重磨损时,基体和复合材料的磨损机制均为严重的粘着磨损。     

热处理对Al2O3f+Cf/ZL109混杂复合材料干滑动摩擦磨损性能影响的统计学研究

利用挤压铸造法制备了Al₂O_3f+C_f/ZL109短纤维混杂增强金属基复合材料,并利用统计学方法对比研究了在滑动速度为0.837 m/s、压力为196 N的条件下热处理对该混杂复合材料干摩擦磨损性能的影响。研究结果表明:铸态和热处理态复合材料的磨损率和摩擦系数均服从正态分布,铸态复合材料的磨损率和摩擦系数均值都大于热处理态复合材料,热处理有利于复合材料摩擦磨损性能的提高。铸态复合材料的磨损机制主要为犁沟磨损和层离,热处理后复合材料抗层离的能力增强,磨损机制主要为轻微的犁沟磨损。     

Cf-ZrW2O8/9621复合材料制备及碳纤维和ZrW2O8含量对其热膨胀的影响

热膨胀是影响复合材料性能和使用寿命的主要因素之一。为研究具有低/负热膨胀的复合材料,本文以碳纤维粉、ZrW₂O₈颗粒和环氧树脂为原料,采用模压法制备了C_f-ZrW₂O₈/9621环氧树脂基复合材料,研究了碳纤维粉和ZrW₂O₈颗粒含量对复合材料热膨胀行为的影响规律,并分析了不同温度区间内C_f-ZrW₂O₈/9621环氧树脂基复合材料热膨胀的变化规律。研究结果表明:在30~200 ℃范围内,当ZrW₂O₈颗粒含量不变时,随着碳纤维粉含量的增加复合材料的平均热膨胀系数逐渐降低,其中碳纤维粉含量增加到12%时,复合材料的平均热膨胀系数最低,为29.9×10^{-6/℃,降低了约60%;当碳纤维粉含量不变时,ZrW₂O₈颗粒含量逐渐增加到12%时,复合材料的平均热膨胀系数呈现先减小后增加的趋势,当ZrW₂O₈颗粒含量为9%时,复合材料的热膨胀系数最低,为40.8×10-6}/℃,降低了约28%。在30~200 ℃范围内,C_f-ZrW₂O₈/9621复合材料在热膨胀过程中,温度升高后试样长度的变化量dL与试样原始长度L₀的比值出现增加、减小和增加3个阶段。碳纤维粉和ZrW₂O₈颗粒均能够降低复合材料的热膨胀系数,但碳纤维粉降低复合材料热膨胀的效果比ZrW₂O₈颗粒更好些。     

三维整体编织物增强陶瓷基复合材料的制备工艺及性能表征

本文研究了以连续碳纤维(C_f)三维整体编织物(3D-B)为增强体,以聚碳硅烷(PCS)裂解转化成碳化硅(SiC)为基体的陶瓷基复合材料(CMC)的制备工艺,探讨了不同工艺方法对复合材料微观和宏观性能的影响,并提出进一步改善制各工艺,提高复合材料性能的途径。研究结果表明,采用聚碳硅烷/二乙烯基苯(PCS/DVB)体系浸渍经交联固化后可以大大缩短裂解时间,致密化效率较聚碳硅烷/二甲苯溶液(PCS/Xylene)体系有着显著提高。对于3D-B C_f/SiC CMC用PCS/DVB体系浸渍经7个浸渍裂解周期后试样密度为1.65g/cm3,弯曲强度达326MPa,断裂韧性K_IC为13.72MPa·m1/2;用PCS/Xylene体系浸渍的试样密度为1.54g/cm3,弯曲强度为243MPa,断裂韧性K_IC为8.19MPa·m1/2。研究中利用扫描电镜观察了弯曲试样的断口以分析材料破坏时纤维的断裂、拨出形貌。     

膨胀石墨/聚酯导电复合材料的制备与导电行为

采用熔融共混法制备了膨胀石墨 ( EG) /聚酯 ( PET) 导电复合材料。利用扫描电镜及电导率测试等研究了复合材料的制备方法对其结构形态和导电性能的影响。结果表明, EG与聚合物基体间的相互作用和机械剪切力使PET分子能够进入EG的片层和孔隙中 , 促进了导电网络的形成, 导致EG/PET复合材料具有较低的逾渗值, 仅为3. 14 %。环氧树脂 ( ER) 与EG间的强相互作用使其易于对EG插层和剥离, 使ER-EG/PET体系的逾渗值进一步降低到1. 80 %。运用统计逾渗理论分析了材料的导电机制。发现复合材料电导率的各向异性、复杂的微观结构以及在高于逾渗值仍存在隧道导电是临界指数高于普适值的主要原因。      

镀Ag玻璃微珠-膨胀石墨/聚氯乙烯导电复合材料的制备与表征

采用一种无Pd无SnCl₂化学镀Ag新工艺对空心玻璃微珠（HGB）表面进行化学镀Ag,然后通过熔融共混方法制备镀Ag玻璃微珠（Ag-GB）-膨胀石墨（EG）/聚氯乙烯（PVC）复合材料。借助SEM、EDS和XRD测试手段对Ag-GB镀层的表面形貌与结构进行了表征,研究了Ag-GB和EG作为复合填料对Ag-GB-EG/PVC复合材料导电和力学性能的影响。结果表明:预处理的HGB的表面更易于Ag层的沉积,镀覆的镀层更为均匀、致密;Ag-GB表面的Ag层质量分数为81.15%;固定Ag-GB的质量分数为15%,随着EG质量分数的增加,Ag-GB（15%）-EG/PVC复合材料的体积电阻率呈非线性降低趋势,当EG的质量分数达到逾渗阈值12%时,Ag-GB（15%）-EG/PVC复合材料的体积电阻率为2.18×103 Ω·cm,满足抗静电PVC材料的应用要求。添加质量分数为12%的EG,Ag-GB（15%）-EG/PVC复合材料的体积电阻率与单独填充质量分数为50%的Ag-GB时Ag-GB/PVC复合材料的体积电阻率相当,此时其拉伸强度达到最大值。      

Conductive composites based on exfoliated graphite

Conductive composites of exfoliated graphite (EG) and coal-tar pitch have been prepared by mixing the components. The electrical properties of the composites have been studied, and the results have been interpreted in terms of the percolation theory. The threshold EG content for electrical conduction is determined to be ? 1.5 wt %, independent of the properties of the pitch and EG.     

Thermal-Diffusivity Measurements of Conductive Composites Based on EVA Copolymer Filled With Expanded and Unexpanded Graphite

In this research, the thermal diffusivity of composites based on ethylene- vinyl acetate (EVA) copolymer filled with two kinds of reinforcement graphite materials was investigated. The reinforcement graphite fillers were untreated natural graphite (UG) and expanded graphite (EG). Composite samples up to 29.3 % graphite particle volumetric concentrations (50 % mass concentration) were prepared by the melt- mixing process in a Brabender Plasticorder. Upon mixing, the EG exfoliates in these films having nanosized thicknesses as evidenced by TEM micrographs. Thus, the thermal diffusivity and electrical conductivity of composites based on the ethylene-vinyl acetate matrix filled with nanostructuralized expanded graphite and standard, micro-sized graphite were investigated. From the experimental results it was deduced that the electrical conductivity was not only a function of filler concentration, but also strongly dependent on the graphite structure. The percolation concentration of the filler was found to be (15 to 17) vol% for micro-sized natural graphite, whereas the percolation concentration of the filler in nanocomposites filled with expanded graphite was much lower, about (5 to 6) vol%. The electrical conductivity of nanocomposites was also much higher than the electrical conductivity of composites filled with micro-sized filler at similar concentrations. Similarly, the values of the thermal diffusivity for the nanocomposites, EG-filled EVA, were significantly higher than the thermal diffusivity of the composites filled with micro-sized filler, UG-filled EVA, at similar concentrations. For 29.3 % graphite particle volumetric concentrations, the thermal diffusivity was 8.23 × 10^?7 m² · s^?1 for EG-filled EVA and 6.14 × 10^?7 m² · s^?1 for UG-filled EVA. The thermal diffusivity was measured by the flash method.     

Preparation and properties of electrically conductive PPS/expanded graphite nanocomposites

Nanocomposites based on poly (phenylene sulfide) (PPS) and expanded graphite (EG) or ultrasonicated EG (S-EG) were prepared by melt blending. Morphologies of the nanocomposites were examined using both SEM and TEM. Electrical conductivity and thermal stability of PPS were notably enhanced by the introduction of EG. The percolation threshold values are 1 wt% (S-EG) and 2 wt% (EG) for PPS/S-EG and PPS/EG nanocomposites, respectively. The variation of mechanical strength with the weight fraction of EG and S-EG in the nanocomposites showed somewhat correlation with the threshold filler concentration. The crystallization behavior of PPS matrix in the nanocomposites was investigated using DSC, and the results indicated that the crystallization process was significantly accelerated, leading to an increase in crystallinity.     

Dispersion of nanoplatelets of graphite on PMMA matrix by in situ polymerisation technique

Poly(methyl methacrylate)/expanded graphite (PMMA/EG) composites were prepared by the incorporation of EG in various proportions (1%, 2%, 3%, 4% and 5%) with PMMA by in situ polymerisation technique. The polymer composites were characterised by ultraviolet–visible (UV–vis) and Fourier transform infra-red spectroscopies. The structural property of PMMA/EG nanocomposites was studied by X-ray diffraction. The scanning electron microscopy and transmission electron microscopy of synthesised composites were taken in order to study their morphological properties. The conductivity of composites was measured as function of EG concentration. It was found that conductivity of composites gradually increased with the increase in EG loading. Oxygen permeability of PMMA/EG nanocomposites was calculated and it was found that the property was reduced substantially with rise of EG proportion. The thermal stability of PMMA/EG nanocomposites was improved by dispersion of EG with PMMA matrix.     

Structure–property relationships in isotactic polypropylene/multi-walled carbon nanotubes nanocomposites

In this work, the influence of multi-walled carbon nanotubes (MWCNT) on electrical, thermal and mechanical properties of CNT reinforced isotactic polypropylene (iPP) nanocomposites is studied. The composites were obtained by diluting a masterbatch of 20 wt.% MWCNT with a low viscous iPP, using melt mixing. The morphology of the prepared samples was examined through SEM, Raman and XRD measurements. The effect of MWCNT addition on the thermal transitions of the iPP was investigated by differential scanning calorimetry (DSC) measurements. Significant changes are reported in the crystallization behavior of the matrix on addition of carbon nanotubes: increase of the degree of crystallinity, as well as appearance of a new crystallization peak (owing to trans-crystallinity). Dynamic mechanical analysis (DMA) studies revealed an enhancement of the storage modulus, in the glassy state, up to 86%. Furthermore, broadband dielectric relaxation spectroscopy (DRS) was employed to study the electrical and dielectric properties of the nanocomposites. The electrical percolation threshold was calculated 0.6–0.7 vol.% MWCNT from both dc conductivity and dielectric constant values. This value is lower than previous mentioned ones in literature in similar systems. In conclusion, this works provides a simple and quick way for the preparation of PP/MWCNT nanocomposites with low electrical percolation threshold and significantly enhanced mechanical properties.     

聚乙烯/有机蒙脱土纳米复合材料结晶动力学

采用熔融插层法制备了聚乙烯/有机蒙脱土纳米复合材料,利用示差扫描量热法(DSC)研究了复合材料的等温及非等温结晶行为,并与纯聚乙稀进行了比较.通过Avrami方程,修正Avrami方程的Jeziorny法及Ozawa法分别对等温及非等温结晶过程进行了处理.结果表明:蒙脱土片层在复合材料结晶过程中起到了异相成核作用,复合材料的成核机理与生长方式已不同于聚乙烯;在相同结晶条件下,复合材料的结晶速率明显比聚乙烯快;纯PE的表观活化能为142.14 kJ/mol,而复合材料为158.38 kJ/mol,复合材料的活化能有一定程度提高;对非等温结晶过程分析,Jeziorny方法适用,而Ozawa方法不适用.     

抗静电PET/ATO纤维的制备及材料的性能

采用原位聚合的方法制备了抗静电涤纶(PET)/锑掺杂二氧化锡(ATO)纳米复合材料。结果显示,ATO在PET中分散良好,团聚体尺寸小于200 nm;加入ATO没有影响PET的流动曲线类型,随着ATO含量的增加,在相同的剪切频率下,熔体黏度均呈先增加后减小的趋势;加入ATO提高了材料的热性能,利于熔融纺丝。采用熔融纺丝法制备了抗静电纳米复合纤维。ATO含量为1.0%(质量分数,下同)时纤维的比电阻由2.7×1013Ω.cm下降到4.9×108Ω.cm。抗静电纤维的渗滤阈值为1.05%,低于传统抗静电填料。     

Itaconic acid and amino alcohol functionalized polyethylene as compatibilizers for polyethylene nanocomposites

The compatibilization provided by itaconic acid (IA) and 2-[2-(dimethylamino)-ethoxy] ethanol (DMAE) functionalized polyethylene for forming polyethylene-based nanocomposites was studied and compared. IA was grafted into PE by melt mixing to obtain PEgIA (compatibilizer 1), thereafter, PEgIA was reacted with DMAE also by melt mixing to obtain PAgDMAE (compatibilizer 2). PE-clay nanocomposites were prepared by melt mixing polyethylene with each of the two quaternary ammonium modified montmorillonite clays (Cloisite 30B and Nanomer I28E) plus each of the two previously prepared compatibilizers (PEgIA and PEgDMAE). FTIR characterization confirmed the formation of these two compatibilizers. All the compatibilized nanocomposites had better clay exfoliation–intercalated compared to the uncompatibilized PE nanocomposites. X-ray diffraction and transmission electron microscopy results, as well as the mechanical properties attained showed that the PEgDMAE with the I28E clay produced the better exfoliated–intercalated nanocomposites. Samples with C30B clay did not show any intercalation improvement, as compared to the uncompatibilized samples, which was attributed mainly to the smaller initial intergallery spacing of this clay. Finally, it is concluded that the PEgDMAE offers an outstanding capability for preparing highly exfoliated PE clay nanocomposites.