PET/凹凸棒土复合材料的结晶行为研究

通过双螺杆熔融共混法制备PET/凹凸棒土(AT)复合材料,用示差扫描量热计(DSC)研究了PET、PET/AT复合材料的结晶行为.非等温分析结果表明:在PET中引入AT提高了PET基体结晶温度和PET结晶速率.PET及PET/AT复合材料的结晶温度随降温速率的增大而移向低温.半结晶时间及结晶度随降温速率的增大而减小.基于Avrami方程的动力学分析表明:PET/AT复合材料的非等温结晶过程是带有异相成核的三维增长过程.     

PET/iPP复合材料非等温结晶动力学研究

采用示差扫描量热仪(DSC)研究了不同含量PET(聚对苯二甲酸乙二醇酯)纤维的PET/iPP(全同立构聚丙烯)复合材料的非等温结晶特性,考察了降温速率及PET纤维含量对PET/iPP复合材料非等温结晶性能的影响.结果表明,PET纤维可提高iPP的结晶温度.减少结晶时间,增大结晶速率.     

改性多壁碳纳米管/PET纳米复合材料的非等温结晶行为

采用原位复合方法制备出纯PET、MWNTs-COOH/PET和MWNTs-OH/PET纳米复合材料.通过红外测试发现PET以共价键形式接枝到碳纳米管上;用扫描电镜(SEM)观察了改性碳纳米管在PET基体中的分散性;通过差示扫描量热法(DSC)研究3种纳米复合材料的非等温结晶行为,使用Jeziomy法和莫志深法分析3种样品的非等温结晶动力学.结果表明:COOH/OH官能化MWNTs可以较好地分散在PET基体中并且能够作为一种有效的成核剂,改变PET的成核机理;同时可以使PET在较高的温度下结晶,提高了PET的结晶速率并且MWNTs-COOH/PET复合材料起始结晶时间更早,而MWNTs-OH/PET复合材料结晶速率更快.     

结晶度和pH值对PVDF/PET/CB/GR复合材料体积电阻率的影响

通过熔融共混方法制备聚偏氟乙烯(PVDF)/炭黑(CB)/石墨(GR)和PVDF/聚对苯二甲酸乙二醇酯(PET)/CB/GR复合材料,并采用差示扫描量热仪和电阻率测量仪对复合材料的熔融行为、结晶行为和导电性能进行了表征和分析。结果表明,复合材料的结晶度越高,电阻率越低,这是由于结晶造成的体积收缩所致。而且,复合材料在硫酸溶液中(pH=3)处理9 d后,其电阻率出现下降,这是由于PET分子中的酯基发生水解,产生了大量的极性基团—COOH和—OH,但是这种水解只是发生在PET的局部。     

PET中添加MWNT对其性能及结构的影响测定

将多壁碳纳米管(MWNT)在聚对苯二甲酸乙二醇酯(PET)聚合时加入,制备包含MWNT不同含量的MWNT/PET复合材料,并通过扫描电子显微镜(SEM)分析了复合材料的结构;借助差示扫描量热仪对MWNT/PET复合材料的结晶性能进行测试。     

PET/纳米凹凸棒土复合材料的流变性能

采用不同硅烷偶联剂对纳米凹凸棒土(简称纳米凹土)进行了改性,通过熔融共混法制备了聚对苯二甲酸乙二醇酯（PET）/纳米凹土复合材料,用毛细管流变仪和旋转式流变仪及扫描电子显微镜研究了PET/纳米凹土复合材料的流变特性、动态黏弹性以、动态力学性能及复合材料的微观形态。结果表明,纳米凹土的加入降低了PET的熔体黏度和玻璃化转变温度;使复合材料呈现假塑性流体特征;纳米凹土颗粒间不存在相互作用;硅烷偶联剂使纳米凹土能降低熔体的表观黏度,在PET中分散得较好。     

PET/纳米凹凸棒母料复合材料性能与结构研究

制备了纳米凹凸棒母料(NAMB),并将其与聚对苯二甲酸乙二酯(PET)共混,利用X射线衍射仪、扫描电子显微镜研究了PET/NAMB复合材料的微观结构,并测试了其力学性能。结果表明,NAMB均匀分散在PET基体中呈"海-岛"结构,它的加入较大程度地提高了复合材料的缺口冲击强度,而对拉伸强度影响不大;同时提高了复合材料的结晶度。     

PET/TiO2复合材料非等温结晶行为的研究

采用表面接枝和聚合改性的方法,分别以γ-缩水甘油醚氧丙基三甲基硅烷(GPS)和甲基丙烯酸甲酯(MMA)对纳米二氧化钛(TiO_2)进行表面修饰,通过熔融共混制得聚对苯二甲酸乙二醇酯(PET)/GPS- TiO_2和PET/聚甲基丙烯酸甲酯(PMMA)-TiO_2纳米复合材料,用差示扫描量热法研究了其复合材料的非等温结晶行为,利用不同动力学模型对其结晶过程进行处理。结果表明：未处理的纳米TiO_2提高了PET的熔融温度和结晶温度;而经表面接枝的GPS-TiO_2和PMMA-TiO_2对PET的熔融温度和结晶温度的影响并不显著;不同表面特性的纳米TiO_2降低了PET的结晶度,但经表面接枝后的纳米TiO_2其影响程度减弱;用Jezi- omy法和莫志深法处理PET/TiO_2纳米复合材料的非等温结晶过程比较理想,PET,PET/PMMA-TiO_2,PET/ TiO_2,PET/GPS-TiO_2复合材料的结晶速率依次减小。     

PET/PTT/MMT复合材料的制备及其非等温结晶行为

采用双螺杆挤出机制备了聚对苯二甲酸乙二醇酯/聚对苯二甲酸丙二醇酯(PET/PTT)合金以及该聚酯合金基蒙脱土(MMT)复合材料。采用扫描电镜(SEM)观察了聚酯合金以及聚酯合金基蒙脱土复合材料的结构,通过差示扫描量热仪(DSC)对其非等温结晶行为进行了研究。结果表明:PET/PTT/MMT复合材料结构比聚酯合金致密,并且MMT的分散比较均匀;相同的降温速率下,随着蒙脱土含量的增加,PET/PTT/MMT复合材料的结晶温度向高温方向移动。随着降温速率增大,聚酯合金与聚酯合金基复合材料的结晶峰温度都向低温方向移动。     

PET/纳米SiO2复合材料发泡行为和光学性能

为研究纳米二氧化硅(Si O₂)和基体黏度对聚对苯二甲酸乙二酯(PET)复合材料发泡行为和光学性能的影响,选择两种不同黏度的PET为基体(PET2比PET1黏度高),与不同质量分数的Si O₂复合制备PET/Si O₂复合材料,然后利用CO₂釜压发泡制备PET/Si O₂复合发泡材料。首先,利用扫描电子显微镜(SEM)研究了Si O₂和基体黏度对PET/Si O₂复合发泡材料泡孔结构的影响;其次,研究了Si O₂和基体黏度对PET/Si O₂复合材料发泡温度窗口的影响;最后,研究了Si O₂和基体黏度对PET/Si O₂复合发泡材料光反射性能的影响。结果显示,随着Si O₂含量增加,PET/Si O₂发泡材料泡孔尺寸变小,泡孔密度变大。相较于PET1/Si O₂体系,PET2/Si ...     

Effect of microstructure induced by microcellular injection molding on electromagnetic interference shielding properties

Preparing lightweight and versatile products is the unremitting goal of industry to save resources and energy. Lightweight carbon fiber reinforced polypropylene (CF/PP) composite foams with high-performance electromagnetic interference (EMI) shielding materials were fabricated by microcellular injection molding (MIM) technology. The average length and distribution of CF in CF/PP composite foams were examined. Thanks to the introduction of foaming process, the average CF length of composite foams was 33.98% longer than that of solids, which effectively enhanced the electrical conductivity and EMI shielding properties. The effect of shot size, gas content, and injection rate on the electrical conductivity and EMI properties was investigated. With melt shot size of 2/3 of the cavity volume, gas content of 0.5 wt% N₂ and injection rate of 100 mm/s, optimal cellular structure of the composite material was obtained. The EMI shielding effectiveness (SE) reaches 36.94 dB, which is the highest value achieved by using MIM technology to the best of the authors' knowledge. In addition, the mechanical properties of cellular structure can still maintain good values, with the tensile strength and impact strength improved by 15.3% and 14.03%, respectively.     

A review of vapor grown carbon nanofiber/polymer conductive composites

Vapor grown carbon nanofiber (VGCNF)/polymer conductive composites are elegant materials that exhibit superior electrical, electromagnetic interference (EMI) shielding effectiveness (SE) and thermal properties compared to conventional conductive polymer composites. This article reviews recent developments in VGCNF/polymer conductive composites. The article starts with a concise and general background about VGCNF production, applications, structure, dimension, and electrical, thermal and mechanical properties. Next composites of VGCNF/polymer are discussed. Composite electrical, EMI SE and thermal properties are elaborated in terms of nanofibers dispersion, distribution and aspect ratio. Special emphasis is paid to dispersion of nanofibers by melt mixing. Influence of other processing methods such as in-situ polymerization, spinning, and solution processing on final properties of VGCNF/polymer composite is also reviewed. We present properties of CNTs and CFs, which are competitive fillers to VGCNFs, and the most significant properties of their composites compared to those of VGCNF/polymer composites. At the conclusion of the article, we summarize the most significant achievements and address the future challenges and tasks in the area related to characterizing VGCNF aspect ratio and dispersion, determining the influence of processing methods and conditions on VGCNF/polymer composites and understanding the structure/property relationship in VGCNF/polymer composites.     

Microcellular Conductive Carbon Black or Graphene/PVDF Composite Foam with 3D Conductive Channel: A Promising Lightweight,Heat-Insulating,and EMI-Shielding Material

In this study, a lightweight microcellular carbon-based filler/poly(vinylidene fluoride) (PVDF) composite foam is fabricated with a 3D conductive network that is thermally insulating, electrically conductive, and fabricated on a large scale. This composite can be used for high-efficiency thermal insulation and electromagnetic interference (EMI) shielding applications. The prepared composite demonstrates low density, high electrical conductivity, and excellent thermal insulation properties. The structure and density of the conductive network and the carbon-based filler content has a significant influence on the electrical conductivity of the prepared composite foam. Although the composite comprises microcellular PVDF beads of the same density, the conductivity of the composite-comprising strip beads is greater than that comprising spherical beads. In the same conductive network structure, as the size of the microcellular PVDF beads decrease, the conductive network becomes denser, which results in a higher conductivity. Furthermore, with an increase in the conductive filler content, the conductivity improves significantly. Excellent EMI shielding materials with optimal filler content and particle shapes, exhibiting EMI shielding effectiveness of up to 40–50 dB, are developed. The prepared composite foam possesses excellent application potential in the fields of ultra-light thermal insulation, conductivity, and EMI shielding.     

Studies on processing parameters and thermal stability of ENCF/ABS composites for EMI shielding

Electroless nickel coated carbon fibers (ENCF) were blended with acrylonitrile-butadiene-styrene (ABS) to prepare composites for electromagnetic interference (EMI) shielding. The effects of processing parameters, such as additives, temperature, and fiber loading amount, on EMI shielding effectiveness (SE) were researched. The thermal stability of EMI SE of ENCF/ABS composites was tested by heat treating composites in a drying oven at 60°C, and SE was measured at an interval of one week to consider the degradation of SE. The best SE of ENCF/ABS composites could be reached was 44 dB at optimum processing parameters. The thermal stability of ENCF/ABS composites for EMI shielding was steady without obvious degradation after 60°C heat treatment for five weeks. © 1997 John Wiley & Sons, Inc.     

Electromagnetic Interference Shielding Foams Based on Poly(vinylidene fluoride)/Carbon Nanotubes Composite

Polymeric electromagnetic interference (EMI) shielding foaming materials are found and applied in many frontier fields such as aerospace, transportation, and portable electronics. In this paper, a foam based on a composite system of poly(vinylidene fluoride) (PVDF) filled with carbon nanotubes (CNTs) is prepared for EMI shielding properties by using a solid-state supercritical CO₂ foaming strategy. PVDF is chosen as the matrix because of its excellent chemical resistance, thermal stability, and flame retardancy. The inclusion of CNTs renders this composite system enhanced complex viscosity and storage modulus by about two orders of magnitude. The electrical conductivity and EMI specific shielding effectiveness of obtained foams can be adjusted and reached the optimum value of 0.024 S m⁻¹ and 29.1 dB cm³ g⁻¹, respectively, originating from the gradual development of interconnected CNTs and conductive CNTs network as well as the introduction of cell structure in PVDF matrix. Interestingly, the reorientation of CNTs caused by foaming process results in electrical conductivity percolation threshold of PVDF/CNTs foams markedly decreases, in comparison to their unfoamed samples. This study provides a facile, efficient, green, and economic route for the preparation of EMI shielding foams consisted of fluorinated polymers and carbonaceous fillers.     

Electrical,rheological and electromagnetic interference shielding properties of thermoplastic polyurethane/carbon nanotube composites

Electrically conducting rubbery composites based on thermoplastic polyurethane (TPU) and carbon nanotubes (CNTs) were prepared through melt blending using a torque rheometer equipped with a mixing chamber. The electrical conductivity, morphology, rheological properties and electromagnetic interference shielding effectiveness (EMI SE) of the TPU/CNT composites were evaluated and also compared with those of carbon black (CB)‐filled TPU composites prepared under the same processing conditions. For both polymer systems, the insulator–conductor transition was very sharp and the electrical percolation threshold at room temperature was at CNT and CB contents of about 1.0 and 1.7 wt%, respectively. The EMI SE over the X‐band frequency range (8–12 GHz) for TPU/CNT and TPU/CB composites was investigated as a function of filler content. EMI SE and electrical conductivity increased with increasing amount of conductive filler, due to the formation of conductive pathways in the TPU matrix. TPU/CNT composites displayed higher electrical conductivity and EMI SE than TPU/CB composites with similar conductive filler content. EMI SE values found for TPU/CNT and TPU/CB composites containing 10 and 15 wt% conductive fillers, respectively, were in the range ?22 to ?20 dB, indicating that these composites are promising candidates for shielding applications. © 2013 Society of Chemical Industry     

Electromagnetic interference shielding mechanisms of CNT/polymer composites

The electromagnetic interference (EMI) shielding mechanisms of multi-walled carbon nanotube (MWCNT)/polymer composites were analyzed experimentally and theoretically. For the experimental analysis, EMI shielding effectiveness (SE) of MWCNT/polypropylene (PP) composite plates made in three different thicknesses and at four different concentrations were studied. A model based on the shielding of electromagnetic plane wave was used to theoretically study the EMI shielding mechanisms. The experimental results showed that absorption is the major shielding mechanism and reflection is the secondary shielding mechanism. The modeling results demonstrated that multiple-reflection within MWCNT internal surfaces and between MWCNT external surfaces decrease the overall EMI SE. The EMI SE of MWCNT/PP composites increased with increase in MWCNT content and shielding plate thickness.     

Strong and Flexible Carbon Fiber Fabric Reinforced Thermoplastic Polyurethane Composites for High‐Performance EMI Shielding Applications

Electromagnetic shielding materials play a significant role in solving the increasing environmental problem of electromagnetic pollutions. The commonly used metal‐based electromagnetic materials suffer from high density, poor corrosion resistance, and high processing cost. Polymer composites exhibit unique combined properties of lightweight, good shock absorption, and corrosion resistance. In this study, a novel high angle sensitive composite is fabricated by combining carbon fiber (CF) fabric with thermoplastic polyurethane elastomer (TPU). The effect of stacking angle of CF fabric on EMI shielding performance of composite is studied. When the stacking angle of CF fabric changed, the electromagnetic interference (EMI) shielding effectiveness (SE) of CF fabric/TPU composite can reach a maximum of 73 dB, and the tensile strength can reach 168 MPa. In addition, the composite has anisotropic conductivity, which is conductive along the plane direction and nonconductive along the thickness direction. Moreover, the CF fabric/TPU composite manifests exceptional EMI‐SE/density/thickness value of 383 dB cm² g^?1, which is higher than most of current EMI shielding composites reported in literature. In summary, CF fabric/TPU composite is an excellent EMI shielding material that is lightweight, highly flexible, and mechanically robust, which can be applied to the field of aerospace and some intelligent electronic devices.     

Electrical conductivity and electromagnetic interference shielding effectiveness of carbon black/sisal fiber/polyamide/polypropylene composites

The effects of hybrid fillers on the electrical conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) of polyamide 6 (PA6)/polypropylene (PP) immiscible polymer blends were investigated. Carbon black (CB) and steam exploded sisal fiber (SF) were used as fillers. CB was coated on the surface of SF, and this was exploded by water steam to form carbon black modified sisal fiber (CBMSF). CB/SF/PA6/PP composites were prepared by melt compounding, and its electromagnetic SE was tested in low‐frequency and high‐frequency ranges. We observed that SF greatly contributed to the effective decrease in the percolation threshold of CB in the PA6/PP matrix and adsorbed carbon particles to form a conductive network. Furthermore, an appropriate CB/SF ratio was important for achieving the best shielding performance. The results indicate that CBMSF was suitable for use as electronic conductive fillers and the CB/SF/PA6/PP composites could be used for the purpose of EMI shielding. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42801.     

Fabrication and electromagnetic interference shielding effectiveness of carbon nanotube reinforced carbon fiber/pyrolytic carbon composites

Carbon nanotube reinforced carbon fiber/pyrolytic carbon composites were fabricated by precursor infiltration and pyrolysis method and their electromagnetic interference shielding effectiveness (EMI SE) was investigated over the frequency range of 8.2–12.4 GHz (X-band). Carbon nanotubes (CNTs) were in situ formed through catalyzing hydrocarbon gases evaporating out of phenolic resin with nano-scaled Ni particles. The content of CNTs increased with the increase of Ni loadings (0.00, 0.50, 0.75 and 1.25 wt.%) in phenolic resin. Thermal gravimetrical analysis results showed that the carbon yield of phenolic resin increased with the addition of Ni catalyst. With the formation of CNTs, the EMI SE increased from 28.3 to 75.2 dB in X-band. The composite containing 5.0 wt.% CNTs showed an SE higher than 70 dB in the whole X-band.