Mechanical,electrical, and dielectric properties of polyvinylidene fluoride/short carbon fiber composites with low‐electrical percolation threshold

In this investigation, polyvinylidene fluoride (PVDF)/short carbon fiber (SCF) composites have been prepared by solution casting technique to enhance electrical and dielectric properties with very low‐electrical percolation threshold (0.5 phr SCF). The effect of SCF content on mechanical, thermal and morphological properties of the composites have also been investigated. The mechanical properties of the composites are found to reduce compared to neat PVDF due to poor polymer–filler interaction which can be concluded from FESEM micrographs showing poor bonding between PVDF and SCF. The PVDF/SCF composites exhibit either positive temperature coefficient effect of resistivity or negative temperature coefficient effect of resistivity depending on the loading of SCF in the polymer matrix. The change in conductivity during heating–cooling cycle for these composites shows electrical hysteresis along with electrical set. The melting point of the composites marginally increases with the increase in fiber loading in PVDF matrix as evidenced from DSC thermograms. X‐ray diffraction analysis reveals the crystallinity of PVDF decreases with the increase in SCF loading in matrix polymer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39866.     

基于聚偏氟乙烯复合结构色材料的制备与性能

以聚偏氟乙烯(PVDF)为黏结剂，将其填充于三维PS@SiO₂光子晶体中，锁定PS@SiO₂微球组装的有序阵列，成功构建了结构稳定且柔韧的新型PVDF/PS@SiO₂结构色材料。使用纳米粒度与电位分析仪对PS@SiO₂微球的多分散性指数以及Zeta电位进行了测试，采用SEM、TEM、固体紫外-可见光谱仪、预置式色牢度摩擦仪及拉伸测试仪对PVDF/PS@SiO₂结构色材料的形貌、光学性质及稳定性进行了表征和测试。结果表明，该结构色材料在摩擦测试100次后，结构保持稳定，颜色稳定存在。同时材料易于图案化，具有优异的抗拉伸性能和柔性，材料的拉伸断裂应力达到22.28 MPa，断裂应变为28.49%，在卷曲100次后，依旧保持微观结构稳定。     

Mechanical properties of carbon nanotube/carbon fiber reinforced thermoplastic polymer composite

Carbon nanotube (CNT)/carbon fiber (CF) hybrid fiber was fabricated by sizing unsized CF tow with a sizing agent containing CNT. The hybrid fiber was used to reinforce a thermoplastic polymer to prepare multiscale composite. The mechanical properties of the multiscale composite were characterized. Compared with the base composite (traditional commercial CF), the multiscale composite reinforced by the CNT/CF hybrid fiber shows increases in interlaminar shear strength (ILSS) and impact toughness. Laminate containing CNTs showed a 115.4% increase in ILSS and 27.0% increase in impact toughness. The reinforcing mechanism was also discussed by observing the impact fracture morphology. POLYM. COMPOS., 38:2001–2008, 2017. © 2015 Society of Plastics Engineers     

The effect of the interface/interphase on fiber composite properties

The interfacial region between fibers and matrix in fiber composites governs the transfer of forces between the relatively weak and compliant matrix and the reinforcing fibers. An effective interphase can ensure that the mechanical properties of the composite reflect the high strength and modulus of the fibers. Although composites can be made with the expected strengths and moduli, it is not entirely clear why this is achieved: Tests with critical composites, i.e., those containing very short aligned fibers, do not show the expected stress-strain behavior. This paper examines the effect of an interphase having a shear modulus that is less than that of the matrix. It is found that to explain the Young's moduli of the short fiber composites, the interphase must have a very low modulus indeed; i.e., a few kPa at most. In addition, the strength results can be accounted for only if we assume that the short lengths of fiber used in the experiments had higher strengths than anticipated. Although agreement between experiments and theory is thus not very good, the small amount of experimental evidence available indicates a need for further systematic experiments on critical (i.e. short aligned fiber) composites before firm conclusions are drawn.     

玄武岩连续纤维及其复合材料

介绍了玄武岩连续纤维及其复合材料在国内外发展的历史和现状,以及该新材料的主要特点、应用领域。     

Effect of fiber size on structural and tensile properties of electrospun polyvinylidene fluoride fibers

We use electrospinning to obtain polyvinylidene fluoride (PVDF) fibers and demonstrate simultaneous improvements in β‐crystal microstructure and in tensile properties of fibers with reduction of their diameter. PVDF fibers with average diameters ranging from 70 to 400 nm are obtained by controlling the concentration of the polymer in the electrospinning solution. The amount of β‐crystals present is found to be greater for finer diameter fibers, yielding a maximum β‐phase fraction of 0.86 in the 70‐nm fibers. Moreover, the deformation behavior of the fibers reveals that the tensile modulus and strength improve with reductions in fiber size. Sharp increases in tensile properties are demonstrated when the size of the fibers is reduced below 175 nm. We attribute the enhanced concentration of β‐crystals and the tensile behavior of finer diameter fibers to the extensional forces experienced by the material during electrospinning. POLYM. ENG. SCI., 55:1812–1817, 2015. © 2014 Society of Plastics Engineers     

从制备光纤预制棒产生的废料中回收白炭黑

为了从制备光纤预制棒产生的废料中提取得到白炭黑,采用烘干、研磨、煅烧、酸处理、水洗等手段对废料进行无害化处理,除去杂质部分,使超细二氧化硅颗粒再生出来。重点探究了最佳的煅烧条件,通过对不同煅烧条件下产品的失重分析以及杂质（Fe元素）含量、产品粒径分布等分析,得出了最佳的煅烧温度为500 ℃,煅烧时间大约为1 h。所得产品的质量技术参数基本达到或接近国家标准。     

Mechanical,morphology, and thermal properties of carbon fiber reinforced poly(butylene succinate) composites

Biodegradable poly(butylene succinate) (PBS)/carbon fiber (CF) composites were prepared by melt blending method using twin‐screw extruder followed by injection molding. Mechanical properties, crystallization behavior, morphology, crystal structure, and thermal stability of PBS/CF composites were investigated with different CF contents (0, 5, 10, 15, and 20 wt%). It was found that the tensile and impact properties of the composites were improved markedly with the addition of CF; while too much CF would lead to agglomeration and thus weaken the improvement. Scanning electron microscopic photographs on the fracture surfaces showed superior interfacial adhesion between fibers and PBS matrix. Crystallization peak temperature of PBS in its composites was increased due to the heterogeneous effect of CF. The spherulite size of PBS/CF composites decreased and the nucleation density increased drastically. The crystal structure was not affected by the incorporation of CF, as confirmed from the wide‐angle X‐ray diffraction analysis. thermogravimetric analysis showed that the thermal stability of PBS/CF composites was also enhanced. POLYM. COMPOS., 36:1335–1345, 2015. © 2014 Society of Plastics Engineers     

Porous carbon nanotube/polyvinylidene fluoride composite material: Superhydrophobicity/superoleophilicity and tunability of electrical conductivity

Porous carbon nanotube/polyvinylidene fluoride (CNT/PVDF) composite material can be fabricated via formation and freeze-drying of a gel. The field emission scanning electron microscopy, nitrogen adsorption–desorption and pore size distribution analysis reveal that the introduction of a small amount of carbon nanotubes (CNTs) can effectively increase the surface roughness and porosity of polyvinylidene fluoride (PVDF). Contact angle measurements of water and oil indicate that the as-obtained composite material is superhydrophobic and superoleophilic. Further experiments demonstrate that these composite material can be efficiently used to separate/absorb the insoluble oil from oil polluted water as membrane/absorbent. Most importantly, the electrical conductivity of such porous CNT/PVDF composite material can be tuned by adjusting the mass ratio of CNT to PVDF without obviously changing the superhydrophobicity or superoleophilicity. The unique properties of the porous CNT/PVDF composite material make it a promising candidate for oil-polluted water treatment as well as water-repellent catalyst-supporting electrode material.     

Recycling leather waste: Preparing and studying on the microstructure,mechanical, and rheological properties of leather waste/rubber composite

Leather tanning processes cause environmental impact as a result of the generation of solid waste, wastewater, and release of gases. The improper disposal of such waste may promote the oxidation of chromium, for example, changing it from chromium (III) to chromium (VI), in which becomes extremely toxic. In this study, composites were prepared from natural rubber (NR) with industrial leather waste (L_w), varying the waste amount from 20 to 80 phr, with the aim of recycling leather waste. The microstructure, mechanical properties and rheological properties of composites were investigated. The results showed that L_w increased tensile strength and hardness, with good reproducibility, and uniformity of residuals distributed as fillers (miscible materials). These properties indicate that this composite material can be used as raw material for the manufacture of shoes, bags, upholstery, etc. POLYM. COMPOS., 36:2275–2281, 2015. © 2014 Society of Plastics Engineers     

Facile preparation and properties of polyvinylidene fluoride dielectric nanocomposites via phase morphology control and incorporation of multiwalled carbon nanotubes conductive fillers

A novel PVDF dielectric nanocomposite was achieved by controlling phase morphology and incorporating conductive fillers simultaneously, and the mechanical, thermal, dielectric properties of the resultant dielectric nanocomposites were investigated. Mechanical analysis showed that incorporation of modified MWCNTs (MWCNTs-COOH) in the PVDF nanocomposites resulted in significant improvements on the tensile strength (T_s) and elasticity modulus (E_m). When the filler content was 12 wt%, the T_s of MWCNTs-COOH/PVDF could reach 64.6 MPa. XRD test showed that the addition of MWCNTs-COOH and MWCNTs promoted the formation of β-phase of PVDF. DMA analysis showed that the glass-transition temperature of the PVDF nanocomposites slightly increases on loading of original MWCNTs and this effect was more pronounced on loading MWCNTs-COOH. The dielectric property analysis showed that the original MWCNTs were more likely to form local conductive networks in the PVDF matrix, promoting the electron displacement polarization, and improving the dielectric constant. When the contents of MWCNTs was 12 wt%, the percolation threshold was obtained and the dielectric constant (ε′) reached 286, which was 36 times of pure PVDF. Our work provides a simple way to fabricate polymer blends with excellent dielectric performances, good mechanical properties as well as good processing capability but low cost. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48463.     

A compatibilized composite of recycled polypropylene filled with cellulosic fiber from recycled corrugated paper board: Mechanical properties,morphology, and thermal behavior

This article deals with the feasibility of using recycled corrugated paper board (rPF) as the reinforcing material for recycled plastics. The composites of recycled polypropylene (rPP) and rPF were prepared by extrusion compounding and injection molding, and the rPP/rPF composites compatibilized by maleic anhydride grafted PP (PP‐g‐MA), maleic anhydride grafted ethylene‐1‐octene copolymer (POE‐g‐MA), and maleic anhydride grafted styrene‐ethylene‐butylene‐styrene copolymer (SEBS‐g‐MA) were also prepared. The crystallization and melting behavior, mechanical properties, thermal stability, and morphology of these composites were studied. The results indicated that rPF promoted the crystallization, enhanced the strength and toughness of rPP/rPF composites to some extent while decreased thermal stability at the same time. PP‐g‐MA and POE‐g‐MA improved the dispersion and interface adhesion of rPF, and further upgraded the mechanical properties and vicat softening temperatures. Among these compatibilizers, PP‐g‐MA was most favorable to the strength improvement while POE‐g‐MA was most favorable to the toughness improvement. As for SEBS‐g‐MA, it had no obvious modification effect. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical and electromagnetic interference shielding properties of carbon fiber/graphene nanosheets/epoxy composite

Graphene oxide (GO) was introduced into carbon fiber/epoxy composite using a wet process for impregnating carbon fiber by epoxy added with GO, which resulted in an enhancement in the interfacial performance and electromagnetic interference shielding effectiveness (SE) of composite. To investigate the reinforcing mechanism, we compared the reinforcing effect between graphene oxide and reduced graphene oxide through interlaminar shear strength test, microdrop test, scanning electron microscopy, and transmission electron microscopy. The results indicate that toughening effect plays the key role for the interfacial improvement of carbon fiber/graphene nanosheets/epoxy composite. By adding only 0.1 wt% GO, the composite achieved an 11% enhancement of interlaminar shear strength at the maximum of 117.45 MPa and a SE improvement about 10 dB in the range of 5–20 GHz in the meantime, giving rise to a highly practicable potential for industrial utilization. POLYM. COMPOS., 37:2494–2502, 2016. © 2015 Society of Plastics Engineers     

Mechanical properties of wood plastic composite panels made from waste fiberboard and particleboard

The possibility of producing wood‐plastic panels using a melt blend/hot press method was studied in this research. The studied panels were compared with conventional medium density fiberboard (MDF) and particleboard (PB) panels. Wood‐plastic panels were made from high density polyethylene (as resin) and MDF waste and PB waste (as natural fiber) at 60, 70, and 80% by weight fiber loadings. Nominal density and dimensions of the panels were 1 g/cm³ and 35 × 35 × 1 cm³, respectively. Mechanical properties of the panels including flexural modulus, flexural strength, screw and nail withdrawal resistances, and impact strength were studied. Results indicated that the mechanical properties of the composites were strongly affected by the proportion of the wood flour and polymer. Maximum values of flexural modulus of wood plastic panels were reached at 70% fiber content. Flexural strength, screw and nail withdrawal resistance, and impact strength of wood plastic composites declined with the increase in fiber content from 60 to 80%. This was attributed to the lack of compatibility between the phases. The produced panels outperformed conventional PB panels regarding their mechanical properties, which were acceptable when compared with MDF panels as well. The best feature in the produced panels was their screw withdrawal resistance, which is extremely important for screw joints in cabinet making. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

无机复合涂层对碳纤维性能的影响

采用溶胶-浸渍法在碳纤维表面制备了二氧化钛-二氧化硅复合涂层。考察了钛溶胶与硅溶胶体积比、浸渍方式、浸渍次数对涂层的影响。利用X射线衍射（XRD）、扫描电镜（SEM）和透射电镜（TEM）分析了涂层的相组成及形貌。通过静态等温氧化实验考察了复合涂层碳纤维的抗氧化性能。结果表明：钛溶胶与硅溶胶体积比为15∶1条件下采用真空超声浸渍3次,制备的复合涂层均匀、完整、致密,与碳纤维表面结合良好,涂层抗氧化性能好,涂层二氧化钛为锐钛矿型、二氧化硅为无定型。将复合涂层碳纤维在400 ℃连续氧化15 h,其质量损失率仅为5.91%。     

环氧/碳纤维复合材料性能研究

本文主要分析了碳纤维帘子布复合材料的性能,并与T300单向碳纤维复合材料性能进行对比。结果表明,碳纤维帘子布复合材料性能低于T300单向碳纤维复合材料性能。     

Effect of annealing on the structure and properties of polyvinylidene fluoride hollow fiber by melt‐spinning

Polyvinylidene fluoride hollow fibers were prepared by melt‐spinning technique under three spinning temperatures. The effects of annealing treatment on the structure and properties of hollow fiber were studied by differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), tensile test, and scanning electron microscopy (SEM) measurements. DSC and WAXD results indicated that the annealing not only produced secondary crystallization but also perfected primary crystallization, and spinning and annealing temperature influenced the crystallinity of hollow fiber: the crystallinity decreased with the increase of spinning temperature; 140°C annealing increased the crystallinity, and hardly influenced the orientation of hollow fiber; above 150°C annealing increased the crystallinity as well, and furthermore had a comparative effect on the orientation. The tensile tests showed that the annealed samples, which did not present the obvious yield point, exhibited characteristics of hard elasticity, and all the hollow fiber had no neck phenomenon. Compared with the annealed sample, the precursor presented a clear yield point. In addition, the annealed samples had a higher break strength and initial modulus by contrast with the precursor, and the 140°C annealed sample showed the smallest break elongation. SEM demonstrated the micro‐fiber structure appeared in surface of drawn sample. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 935–941, 2007     

碳纤维镀铜及其对铜基复合材料界面影响

碳纤维与铜之间的润湿性很差，导致碳纤维-铜复合材料的界面问题十分突出，给碳纤维增强铜基复合材料具有的优异性能带来很大的影响.用化学反应法在碳纤维表面镀铜,然后再与铜复合，可以有效地解决上述问题.但由于碳纤维具有纤细疏水、表面惰性的特点，对它镀铜很难.本文以CuSO₄为主盐，锌粉为还原剂，研究了4种不同类型添加剂: A（烷基苯磺酸盐）、B（烷基磺酸盐）、C（十二烷基脂肪酸盐）和D（十二烷基脂肪酸盐+乙酸钠）对碳纤维镀铜的影响.结果表明：D型添加剂最有利于碳纤维镀铜, 它能有效地解决碳纤维镀铜时经常发生的碳纤维束“黑心”问题.在实验中观察到整束碳纤维被均匀、连续地镀上了铜.通过扫描电镜观察：在镀铜碳纤维的断面上可以看到镀层和碳纤维结合得很牢固;在镀铜碳纤维与铜复合所得的复合材料中碳纤维与铜之间的界面结合得十分紧密.     

SCRIMP用环氧树脂体系及其复合材料的性能研究

采用粘度、凝胶时间及力学性能测试以及示差扫描量热分析和扫描电镜研究了上纬环氧树脂2511-A体系的工艺性能,固化反应行为及其采用西曼树脂浸渍膜塑成型工艺(Seeman Composites Infusion Molding Process,SCRIMP)制成的环氧玻璃纤维复合材料的性能。结果表明:2511-A体系在25～35℃下粘度保持在600 mPa.s以下的时间长达120 min,满足SRCIMP成型工艺要求,其玻璃化转变温度为112℃。复合材料的孔隙率仅为0.19%,且具有良好的力学性能。     

Effect of the filler morphology on the crystallization behavior and dielectric properties of the polyvinylidene fluoride-based composite

Ceramic/polymer composites can be chemically stable, mechanically strong, and flexible, which make them candidates for electric devices, such as pressure or temperature sensors, energy storage or harvesting devices, actuators, and so forth. Depending on the application, various electrical properties are of importance. Polymers usually have low dielectric permittivity, but increased dielectric permittivity can be achieved by the addition of the ceramic fillers with high dielectric constant. With the aim to enhance dielectric properties of the composite without loss of flexibility, 5 wt% of BaTiO₃-Fe₂O₃ powder was added into a polyvinylidene fluoride matrix. The powder was prepared by different synthesis conditions to produce core/shell structures. The effect of the phase composition and morphology of the BaTiO₃-Fe₂O₃ core/shell filler on the structure and lattice dynamics of the polymer composites was investigated. Based on the results of the thermal analysis, various parameters of ceramic/polymer composites were determined. Differences in the phase composition and morphology of the filler have an influence on the formation of various polyvinylidene fluoride allomorphs and the degree of crystallinity. Furthermore, the dielectric performances of pure polyvinylidene fluoride and the polymer/ceramic composites were measured.