凯芙拉纤维/尼龙6热塑性复合材料的研制

研究了凯芙拉纤维与尼龙 6单体通过阴离子原位聚合制备热塑性复合材料的方法。以氢氧化钠为引发剂 ,甲苯二异氰酸酯 (TDI)为活化剂 ,确定体系的聚合温度为 160℃ ,引发剂、活化剂用量为6.42 m ol/L ,聚合时间 60 min,在此条件下聚合速度较快 ,单体转化率 1h后达 95 %以上。研究发现 ,凯芙拉纤维经酰化处理后 ,基本上不会对己内酰胺阴离子聚合体系产生阻聚作用     

Studies in the properties of nylon 6–glass fiber composites

Caprolactam has been anionically polymerized within the planar-random continuous glass mat reinforcement using a technique similar to reaction injection molding and up to 55% (w/w) [i.e., 33% (v/v)] glass fiber loading was achieved. The fiber volume fraction distribution across the diameter of the composite was observed to be reasonably uniform. The tensile stress–strain properties were determined. Composite modulus and strength appeared to be linearly dependent on the fiber volume fraction and increase with fiber volume content. The type of composite material studied has been used for compression molding of articles. Therefore, some tensile data were redetermined after compression molding and possible changes in degree of crystallinity resulting from the change in the thermal history monitored by differential scanning calorimetry. A 50% drop in the percent degree of crystallinity (monoclinic modification) of the as-polymerized composite and a deterioration in the tensile properties of the composite were observed after compression molding. On compression molding the mold surface needs to be completely covered with the composite sheet material; otherwise, matrix polymer flows out of the composite, and areas deficient in reinforcement result.     

Natural fiber eco‐composites

The natural fiber (NF) reinforced composites, so called eco‐composites, are subject of many scientific and research projects, as well as many commercial programs. The growing global environmental and social concern, high rate of depletion of petroleum resources, and new environmental regulations have forced the search for new composites and green materials, compatible with the environment. The aim of this article is to present a brief review of the most suitable and commonly used biodegradable polymer matrices and NF reinforcements in eco‐composites, as well as some of the already produced and commercialized NF eco‐composites. POLYM. COMPOS. 28:98–107, 2007. © 2007 Society of Plastics Engineers     

Styrene butadiene rubber-short nylon fiber composites

The cure characteristics and mechanical properties of short nylon fiber reinforced styrene butadiene rubber were studied at varying fiber concentration. The plasticity of the composite was adversely affected by nylon short fibers. The minimum torque increased with fiber concentration. Scorch time and cure time showed a reduction in presence of short fibers. The tensile strength, tear strength, elongation at break and abrasion resistance were studied in both the orientation of fibers. Tensile strength, tear strength and abrasion resistance increased with fiber concentration and were higher in the longitudinal direction. Resilience showed a reduction with fiber content and compression set increased with fiber loading.     

Conducting aluminum‐filled nylon 6 composites

This work is concerned with the preparation and characterization of composite materials prepared by compression molding of a mixture of aluminum flakes and nylon 6 powder. The electrical conductivity, density, hardness and morphology of composites were investigated. The electrical conductivity of the composites is < 10⁻¹¹ S/cm unless the metal content reached the percolation threshold, beyond which the conductivity increased markedly by as much as 10¹¹. The volume fraction of conductive filler at the percolation threshold was calculated from experimental data, by fits to functions predicted by the percolation theory. Decreasing the average particle diameter of filler leads to increased percolation threshold (it varies from 23 to 34 vol% for the three different fillers studied) and decreased maximal conductivity of composites. The density of the composites was measured and compared with values calculated assuming different void levels within the samples. Furthermore, it is shown that for certain sizes of particle filler, the hardness decreases initially with the increase of metal concentration, possibly because of poor surface contact with the nylon matrix, but, starting from a certain value, there is a hardness increase. For the smallest particle filler, the hardness of samples is not influenced by the presence of the filler.     

Microstructural characterization of short glass fiber and PAN based carbon fiber reinforced nylon 6 polymer composites

Microstructural characterization of nylon 6/short glass fiber (SGF) and nylon 6/polyacrolonitrile based carbon fibers (PAN‐CFs) of 10 to 40 wt% has been performed by positron lifetime technique (PLT). The positron lifetime parameters viz., o‐Ps lifetime (τ₃), o‐Ps intensity (I₃), and fractional free volume (F_v) of nylon 6/SGF and nylon 6/PAN‐CF composites are correlated with the mechanical properties viz., tensile strength and Young's modulus. The F_v shows negative deviation with the reinforcement of 10 to 40 wt% of PAN‐CF and show positive deviation in nylon 6/SGF from the linear additivity relation. The negative deviation in nylon 6/PAN‐CF composite suggests the induced molecular packing due to the chemical interaction between the polymeric chains of nylon 6 and PAN‐CF. The positive deviation in nylon 6/SGF composite indicates the formation of interface between the polymeric chains of nylon 6 and SGF. The increased crystallinity of nylon 6/SGF and nylon 6/PAN‐CF composites shows the improved mechanical properties of the composites. The hydrodynamic interaction parameter (h), which shows more negative values in nylon 6/SGF than nylon 6/PAN‐CF composites. However, the extent of chemical interaction in nylon 6/SGF is less compare to nylon 6/PAN‐CF composites. This is evident from Fourier transform infrared spectrometry studies. POLYM. ENG. SCI., 58:1428–1437, 2018. © 2017 Society of Plastics Engineers     

废聚丙烯/废轮胎胶粉/废尼龙短纤维复合材料Ⅱ.工艺条件

采用反应挤出方法制备了废聚丙烯／废轮胎胶粉／废尼龙短纤维(WPP／GRT／WSF)复合材料,讨论了螺杆转速、机头温度对WPP／GRT／WSF复合材料力学性能的影响。结果表明,当螺杆转速为15r／min,机头温度为185～195℃时,WPP／GRT／WSF复合材料的力学性能达到最佳,拉伸强度为13．6MPa,冲击强度为25．2kJ／m^2。按照最佳配方和工艺挤出管材的拉伸强度为4,6MPa,冲击强度为5．4kJ／m^2,爆破压力为0．69MPa。     

Melt blending of polypropylene‐blend‐ polyamide 6‐blend‐organoclay systems

The melt blending of polypropylene‐blend‐polyamide 6‐blend‐organoclay (PP/PA6/organoclay) systems has been investigated using an internal mixer without any traditional compatibilizer. In the presence of organoclay, the melting of PA6 phase is accelerated and the dimension of the dispersed phase in the matrix is reduced. Transmission electron microscopy results reveal clay‐rich interface zones formed between the PA6 dispersed phase and the PP matrix in the PP/PA6/organoclay system. An interface blending approach has been designed to investigate the interface zones between the immiscible polymers, and the interface zones have been characterized by Fourier transform infrared and X‐ray photoelectron spectroscopy. In the presence of the organoclay, the PA6 component in interface zones is stable even after etching extraction with formic acid, suggesting a strong interaction takes place among PP, PA6 and the organoclay. Such clay‐rich interface zones act as a compatibilizer for the two immiscible polymers, resulting in a better dispersion of PA6 phase in PP matrix. Copyright © 2006 Society of Chemical Industry     

Electroconductive nylon 6 and copper composites

A study is reported on the effect of the filler size and concentration on the electrical resistivity, density, and hardness of composites made of copper powder embedded in nylon 6 matrix by means of compression molding. The electrical resistivity of the composites is > 10¹¹ ohm·cm unless the metal content reached the percolation threshold, beyond which the resistivity decreased markedly by as much as 10¹². The percolation concentration was found to decrease with a decrease in the average particle diameter. The density of the composites was measured and compared with values calculated assuming different void levels within the samples. However, there is no sharp variation in the density due to the onset of percolation. Furthermore, it is shown that a percolation concentration can be also defined in the hardness/metal concentration curves as the intercept of linear regression curves of the low and high metal content regimes, respectively.     

Conducting polymer composites of zinc‐filled nylon 6

The present work is concerned with the effect of processing variables and filler concentration on the electrical conductivity, hardness, and density of composite materials prepared by compression molding of a mixture of zinc powder and nylon 6 powder. The electrical conductivity of the composites is <10^?12 S/cm, unless the metal content reaches the percolation threshold at a volume fraction of about 0.18, beyond which the conductivity increases markedly by as much as 10 orders of magnitude. The density of the composites was measured and compared with values calculated by assuming different void levels within the samples. Furthermore, it is shown that the hardness increases with the increase of metal concentration, but for values of filler volume fraction higher than about 0.30 the hardness of samples remains almost constant. Two parameters of molding process, temperature and time, were shown to have a notable effect on the conductivity of composites, whereas pressure has no influence on this property in the pressure range considered. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1449–1454, 2001     

A comparative study of short nylon fiber—Natural rubber composites prepared from dry rubber and latex masterbatch

A novel method for the preparation of short nylon fiber–natural rubber composites was developed in which short fibers chopped to approximately 6 mm were incorporated in the latex stage and processed into sheet form. By this method, mixing cycle time was reduced without compromising the fiber dispersion. Fiber breakage during mixing was reduced. The new composites when compounded with a dry bonding system based on hexamethylenetetramine, resorcinol and hydrated silica (HRH) showed improved modulus, tensile strength and abrasion resistance compared to conventional composites. Tear strength, resilience, and compression set were similar to the conventional composites. SEM analysis indicated better interaction between matrix and fibers in the case of latex master batch. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Multi-walled carbon nanotubes reinforced nylon 6 composites

Multiwalled carbon nanotubes (MWNT) were functionalized with amine groups using a ‘grafting to’ technique. The oxidized MWNT (MWNT-COOH) were converted to the acyl chloride functionalized MWNT (MWNT-COCl) by treating them with thionyl chloride (SOCl₂), and then MWNT-COCl was reacted with hexamethylenediamine to prepare MWNT-NH₂. The formation of MWNT-NH₂ was confirmed through the FTIR observation. MWNT-NH₂/nylon 6 composites with different MWNT loadings were prepared by the simple melt compounding approach. A fine dispersion of MWNTs throughout nylon 6 matrix was observed by SEM and TEM. The fractured surface of the composites showed not only a uniform dispersion of MWNTs but also a strong interfacial adhesion with the matrix, as evidenced by the presence of many broken but strongly embedded MWNTs in the matrix in the absence of debonding of MWNTs from the matrix. Incorporation of MWNTs improved the mechanical properties significantly. Higher thermal stability was obtained for the composites with better dispersed MWNTs.     

Thermoplastics composites with ductile fiber coatings based on UHMWPE: A study on short fiber GR nylon 6

Glass microscope slides were initially used to develop a technique for bonding UHMWPE films on to glass and polyamides respectively, as well as to provide a simple physical model for interlayered fiber composites. Further experiments were carried out on glass fibers coated with UHMWPE from a xylene solution, in order to evaluate the applicability of the above technique and of the physical model in actual composite systems. Although great difficulties were encountered in achieving a well boned uniform coating on the glass fibers the results have confirmed the viability of the approach: the impact strength of compression molded glass reinforced Nylon plaques, measured with an instrumented falling weight apparatus, was increased considerably with only a corresponding small loss in flexural modulus. Dynamic mechanical analysis results indicate that a UHMWPE interlayer substantially increases the tan δ of the short fiber composite over a wide temperature range, albeit with some reduction in modulus.     

Characterization of mixed fiber nylon composites incorporating composite scrap

Recycling of engineering thermoplastics and their composites represents both a challenge and an opportunity in today's material science. A study on nylon 6,6 based composites with mixed glass-fiber and carbon-fiber reinforcement, including nylon composite scrap in their formulation, is reported. Several formulations were prepared by injection molding and were characterized by stress-strain-measurements, impact testing, simultaneous differential thermal analysis and thermogravimetry (DTA-TG), density measurements and scanning electron microscopy (SEM). No dependence on mechanical properties due to increasing amounts of scrap in the composites was found up to 10.4 wt%. The generated recycled composites generally showed lower mechanical properties as compared with the virgin composite because of a poor matrix-fiber adhesion.     

尼龙短纤维接枝橡胶复合材料增强胎面胶

将用γ-(甲基丙烯酰氧基)丙基三甲氧基硅烷(A174)或γ-氨丙基三乙氧基硅炕(A1100)处理后的尼龙短纤维分别加入到特软羧基丁苯胶乳中,浸泡10min后于110℃烘箱中干燥90min,可制备尼龙短纤维接枝橡胶复合材料。结果表明,经接枝改性的尼龙短纤维橡胶复合材料的拉伸强度超过了18．00MPa,100％定伸应力和300％定伸应力为未处理尼龙短纤维橡胶复合材料的1．5～2．0倍,撕裂强度提高了约82％。将该复合材料加入载重轮胎胎面胶中,可提高胎面胶的抗湿滑性。     

Miscibility in poly-p-phenylene terephthalamide/nylon 6 and nylon 66 molecular composites

Miscibility and crystallization of poly-p-phenylene terephthalamide (PPTA)/nylon 6 and nylon 66 composites prepared by coagulation of isotropic ternary sulfuric acid solutions were studied. The apparent crystallinity of nylon 6 and nylon 66 in molecular composites was investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The solvation of nylon 6 crystals in PPTA matrix was observed when the PPTA content exceeds 70 wt%. Cross-hydrogen bonding seems to be responsible for the virtual disappearance of nylon 6 crystals. Specific interaction between PPTA and nylon 6 macromolecules and phase separation during thermal treatment has been discussed.     

Epoxy—phenol—cardanol—formaldehyde systems: Thermogravimetry analysis and their carbon fiber composites

Systems consisting of epoxy resin and phenol-cardanol-formaldehyde (PCF) were prepared. The thermal characterization of the systems, investigated by thermogravimetry analysis, indicated that the increase of PCF content improves the thermal stability. Chemical resistance as well as mechanical properties of their carbon-fiber composites were also determined. The matrix-fiber interfacial study by scanning electron microscopy showed that the higher the PCF amounts in the system products, the better the interfacial bonding. © 1996 John Wiley & Sons, Inc.     

Preparation of porous nylon 6 fiber via electrospinning

Porous nylon‐6 fibers were obtained by electrospinning of ultra‐high molecular polyamide 6 (UHMW‐PA6). First, UHMW‐PA6/calcium formate composite nanofibers were prepared as precursors by electrospinning UHMW‐PA6 solutions containing different contents of calcium formate particles. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the surface morphology and inner structure of composite nanofibers. It was found that calcium formate particles were distributed both inside and on the surface of nanofibers. Fourier transform infrared (FTIR), differential scanning calorimetry, and thermal gravimetric analysis (TGA) were used to study the structure and properties of these nanofibers. Then, porous UHMW‐PA6 nanofibers were obtained by soaking the electrospun web in water for 24 h, to remove calcium formate particles. The removal of calcium formate particles was confirmed using FTIR and TGA tests. SEM and TEM observations revealed the formation of porous structure in these nanofibers. In addition, CaCl₂ was used instead of calcium formate to prepare the UHMW‐PA6 nanoporous fiber. POLYM. ENG. SCI., 55:1133–1141, 2015. © 2014 Society of Plastics Engineers     

Dynamic viscoelastic behavior of styrene-grafted nylon 6 fiber

Styrene-grafted nylon 6 fibers which had been prepared by the UV irradiation method were investigated by dynamic viscoelasticity and dilatometry. It was found that nylon 6 is relaxed and polystyrene is simultaneously plasticized by nylon 6 during grafting. These phenomena are interpreted as follows. The grafting process causes nylon 6 to have a lower glass transition temperature and increases grafting frequency of polystyrene to nylon 6 by increasing the chemical junctions between the two components, so that they necessarily become more compatible.     

High electrical conductivity of nylon 6 composites obtained with hybrid multiwalled carbon nanotube/carbon fiber fillers

The synergetic effect of multiwalled carbon nanotubes (MWNTs) and carbon fibers (CFs) in enhancing the electrical conductivity of nylon 6 (PA6) composites was investigated. To improve the compatibility between the fillers and the PA6 resin, we grafted γ‐aminopropyltriethoxy silane (KH‐550) onto the MWNTs and CFs after carboxyl groups were generated on their surface by chemical oxidation with nitric acid. Fourier transform infrared spectroscopy and thermogravimetric analysis proved that the KH‐550 molecules were successfully grafted onto the surface of the MWNTs and CFs. Scanning electron microscopy and optical microscopy showed that the obtained modified fillers reduced the aggregation of fillers and resulted in better dispersion and interfacial compatibility. We found that the electrical percolation threshold of the MWNT/PA6 and CF/PA6 composites occurred when the volume fraction of the fillers were 4 and 5%, respectively. The MWNT/CF hybrid‐filler system exhibited a remarkable synergetic effect on the electrically conductive networks. The MWNT/7% CF hybrid‐filler system appeared to show a second percolation when the MWNT volume fraction was above 4% and a volume resistivity reduction of two orders of magnitude compared with the MWNT/PA6 system. The mechanical properties of different types of PA6 composites with variation in the filler volume content were also studied. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40923.