木粉/低熔点尼龙6复合材料的非等温结晶动力学

利用LiCl改性尼龙6(PA6),并将其与木粉熔融共混制备了木粉/低熔点PA6复合材料,通过DSC法研究了木粉/低熔点PA6复合材料的非等温结晶动力学行为.结果 表明,LiCl降低了PA6的熔点、结晶温度、结晶度和结晶速率,提高了PA6的结晶活化能.木粉是良好的成核剂,能够加快PA6的结晶速率,但却降低了其结晶度.通过...     

Tribological properties of solid lubricants filled glass fiber reinforced polyamide 6 composites

The main purpose of this paper is to further optimize the tribological properties of the glass fiber reinforced PA6 (GF/PA6,15/85 by weight) for high performance friction materials using single or combinative solid lubricants such as Polytetrafluroethylene (PTFE), ultra-high molecular weight polyethylene (UHMWPE) and the combination of both of them. Various polymer blends, where GF/PA6 acts as the polymer matrix and solid lubricants as the dispersed phase were prepared by injection molding. The tribological properties of these materials and the synergism as a result of the incorporation of both PTFE and UHMWPE were investigated. The results showed that, at a load of 40 N and a velocity of 200 rpm, PTFE was effective in improving the tribological capabilities of matrix material. On the contrary, UHMWPE was not conductive to maintain the structure integrity of GF/PA6 composite and harmful to the friction and wear properties. The combination of PTFE and UHMWPE showed synergism on further reducing the friction coefficient of the composites filled with either PTFE or UHMWPE only. Effects of load and velocity on tribological behavior were also discussed. To further understand the wear mechanism, the worn surfaces were examined by scanning electron microscopy.     

热处理对碳纤维/聚酰胺6复合材料界面结晶及力学性能的影响

探究了热处理对聚酰胺6（PA6）在碳纤维（CF）表面的结晶行为及其界面力学性能的影响。利用差示扫描量热法（DSC）、偏光显微镜（POM）观察法等分析手段考察了热处理对PA6在CF表面结晶行为的影响,揭示了在热处理过程中,PA6进行链段重排,形成小且不完善的新结晶,导致结晶度的上升以及界面横晶形貌的完善;进一步通过单丝微球脱粘实验和单向CF/PA6复合材料横向拉伸实验考察了热处理对PA6与CF的界面结合性能的影响,揭示了经退火热处理的试样由于弱界面和应力集中的减少使界面剪切强度增加且单位体积断裂能下降。     

改性碳纤维增强尼龙6复合材料的制备及性能

通过硝酸酸化处理及尼龙溶液浸渍上浆处理对碳纤维(CF)进行表面改性,制备高强度、高模量,同时具有低熔指和优异加工性能的CF增强尼龙6(PA6)复合材料。采用扫描电镜(SEM)、差示扫描量热仪(DSC)和熔融指数仪等方法,对复合材料的微观结构、力学性能和结晶行为进行测试和表征。结果表明,经过PA6溶液浸渍上浆处理后的CF表面形成了一层PA6薄膜覆盖层,大大增强了CF与PA6基体的结合力,改善了CF的分散性,提升了复合材料整体的强度与模量,改性CF加入量为8%(质量分数)时复合材料拉伸强度提升80.8%,弹性模量提升513.9%。进一步对复合材料结晶行为的分析表明,改性CF的加入能够促进PA6由γ晶型向更稳定的α晶型转变,提高其结晶温度及结晶速率,使复合材料的结晶更加均匀、完善,从而提高体系黏度,降低复合材料熔融指数,显著提升了复合材料的加工性能。     

Tensile and thermomechanical properties of short carbon fiber reinforced polyamide 6 composites

In this study, carbon fiber (CF) reinforced polyamide 6 (PA6) composites were prepared by using melt mixing method. Effects of fiber length and content, on the mechanical, thermal and morphological properties of CF reinforced PA6 composites were investigated. Fiber length distributions of composites were also determined by using an image analyzing program. It was seen that the maximum number of fibers were observed in the range of 0–50 μm. Mechanical test results showed that, increasing CF content increased the tensile strength, modulus and hardness values but decreased strain at break values of composites. DSC results showed that T_g and T_m values of composites were not changed significantly with increasing CF content and length. However, heat of fusion and the relative degree of crystallinity values of composites decreased with ascending CF content. DMA results revealed that storage modulus and loss modulus values of composites increased with increasing CF content.     

连续玻璃纤维和玻璃微珠共增强尼龙6复合材料的抗冲击性能

低速冲击是聚合物基复合材料在运输和服役过程中常见损伤方式,常造成复合材料结构损伤、性能降低、承载能力下降,影响使用。针对2D纤维增强聚合物基复合材料在冲击载荷作用下抗分层能力差的问题,本文采用熔融挤出结合热压成型法制备了二元和三元尼龙6(PA6)基复合材料,对比研究了连续玻璃纤维(GF)、玻璃微珠(GB)及两者共增强PA6基复合材料的摆锤冲击性能和落锤低速冲击响应。结果表明：(1) GF和GB能显著提高PA6的抗冲击性能,且GF的增强效果明显高于GB;(2) GB增强PA6基复合材料(GB/PA6)的冲击强度随GB加入量增大而先增大后降低,加入量为25wt%时冲击强度最大;冲击载荷作用下,25wt%GB/PA6的耗能机制除了界面脱粘和钉扎效应之外,还发现GB在PA6基体中的滑移耗能新机制;(3) GF和GB共增强PA6复合材料(GB-GF/PA6)中纤维起主要的增强作用,摆锤冲击实验和落锤冲击实验均证明存在协同增强效应;(4) GF和GB共增强的协同增强效应是由于共增强复合材料在冲击载荷作用下,抗Ⅱ型裂纹扩展能力提高,使复合材料抗分层能力得到强化;从而证明在基体中引入适量球形GB是提高...     

Iron-montmorillonite and zinc borate as synergistic agents in flame-retardant glass fiber reinforced polyamide 6 composites in combination with melamine polyphosphate

This paper presents a preliminary investigation on the effects of organically modified iron-montmorillonite (Fe-OMT) and zinc borate (ZnB) on thermal degradation behaviors and flame retardancy of melamine polyphosphate (MPP) flame-retarded glass fiber reinforced polyamide 6 (GFPA6). The samples were characterized using limiting oxygen index (LOI), UL-94 tests, thermogravimetric analysis (TGA), Fourier transform infrared coupled with the thermogravimetric analyzer (TG-FTIR) and Microscale Combustion Calorimeter (MCC) measurements. The residue after LOI test was also analyzed by Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and Raman spectroscopy. A substitution of a certain fraction of MPP with ZnB or Fe-OMT can significantly improve the UL-94 rating of GFPA6/MPP composites from no rating to V0 rating, exhibiting excellent flame retardacny. Based on the investigations, different flame retardant mechanisms were proposed for the two effective flame-retardant formulations.     

连续碳纤维/尼龙6热塑性复合材料的吸湿及力学性能

利用热压工艺制备了三种不同等温结晶时间的连续碳纤维（CF）增强尼龙6（PA6）单向复合材料,并分别研究了吸湿前后连续CF/PA6复合材料单向板的0°拉伸、90°拉伸、弯曲和层间剪切性能变化。结果发现,CF/PA6复合材料的0°拉伸、90°拉伸、弯曲和层间剪切强度（模量）分别下降了10%~37%（0~0.6%）、35%~46%（62%~64%）、53%~61%（16%~28%）和5%~31%。结合SEM断面观察和抛光金相显微学给出了吸湿对CF/PA6复合材料性能的影响机制。      

Non-isothermal crystallization of polyamide 6 matrix in all-polyamide composites: crystallization kinetic, melting behavior, and crystal morphology

The difference in the melting points of polyamide 66 (PA66) fiber and polyamide 6 (PA6) film permits the preparation of all-polyamide (all-PA) composites by film-packing. Good interface performance and integrated consolidation structure in this all-PA composite are contributed to the similar chemical composition between PA66 fiber and PA6 matrix. In this paper, the non-isothermal crystallization kinetics and melting behaviors of PA6 matrix in all-PA composite are studied by differential scanning calorimetry (DSC), in which the modified Avrami equation, Ozawa model, and Mo equation combining Avrami and Ozawa equation are employed. It is found that the Mo equation exhibits great advantages in treating the non-isothermal crystallization kinetics for both neat PA6 and PA6 matrix in all-PA composite. The crystal morphologies of single PA66 fiber–PA6 composite by polarizing microscope (POM) clearly show a transcrystallinity layer of PA6 around PA66 fiber that proves a remarkable nucleation effect of PA66 fiber surface on the crystallization of PA6 matrix.     

Isothermal crystallization kinetics of the Ni63Cr18Si13B6 alloy

Isothermal crystallization kinetics of the Ni₆₃Cr₁₈B₁₃Si₆ alloy was carried out by differential scanning calorimetry. The JMA approach was used and the mean Avrami exponent values obtained were found to be consistent with a primary precipitation and a polymorphic crystallization, respectively, for the two crystallization stages. The novel concept of the local value of the Avrami exponent was also applied. The n _loc–x plot was seen to be independent of the temperature of isothermal crystallization for the two stages, indicating that the crystallization processes depend only on the volume fraction transformed. Finally, the time-scaling law in the kinetic plots was verified.     

Mechanical behavior of carbon fiber reinforced polyamide composites

The purpose of this work is to compare tensile, compressive and interlaminar shear properties of different carbon reinforcement/polyamide composites obtained by interfacial polymerization and hot compression molding techniques. Two types of composite matrices were studied: polyamide 6 and polyamide 6/6, both reinforced by fabric and unidirectional carbon fibers. The effects of the fiber volume fraction and the matrix on mechanical properties were analyzed through tensile, interlaminar shear and compressive tests. In general, the results have shown a slight increase of the composite elastic modulus, tensile and compressive strength with the increase of carbon fiber content. The microscopic damage development within selected composites during the loading has been observed through optical and scanning electron microscope techniques and has shown that shear failure at the fiber/matrix interface has been mostly responsible for damage development, initiated at relatively low stress.     

Preparation and properties of continuous glass fiber reinforced anionic polyamide-6 thermoplastic composites

Continuous glass fiber (GF) reinforced anionic polyamide-6 (APA6) composites were prepared via in situ ring-opening polymerization of caprolactam monomers. The effects of catalyst content, polymerization temperature and time on the viscosity average molar mass (M_v) and degree of crystallinity (X_c) were investigated in detail. The final mechanical properties of GF/APA6 composites were also studied. The results indicated that both high molecular weight and the high degree of crystallinity of resin matrix lead to the high mechanical properties of composites. Furthermore, the mechanical test results showed that the composites of plain woven fabric had tensile strength of 434 MPa and flexural strength of 407 MPa. The morphologies of tensile fracture surfaces of the composites specimens were observed through Scanning Electron Microscope (SEM). The SEM analysis showed that many disorganized nano-fiber crystals appear in the tensile fracture surfaces, which improve the mechanical properties of the matrix resin. The mechanical properties of the composites with different post-heat treatments were further investigated. The mechanical properties of the composites are significantly reduced after quenching treatment, but hardly improved after annealing.     

Nanoclay assisted strengthening of the fiber/matrix interface in functionally filled polyamide 6 composites

This study describes the contribution of a nano-filler, i.e. an organically modified layered silicate, in respect of the fiber/matrix interfacial shear strength (IFSS) of a short glass fiber reinforced and functionally filled polyamide 6, given an exfoliated nanocomposite morphology. Apparent IFSS values are determined using a continuum micromechanical method. Polymer chains in the nanoconfined environment of an exfoliated clay nanocomposite are found to crystallize preferentially in the form of a specific crystalline phase with increased degree of crystallinity. Strong dependence of IFSS on polymer crystallinity is found which is related to enhanced shrinkage stresses associated with increased degree of crystallinity.     

Isothermal crystallization kinetics of Ni60Nb4o-xCrx,glasses

Isothermal crystallization kinetics of Ni₆₀Nb_40-xCr_x (x = 0, 5, and 13 at %) glasses was investigated by differential scanning calorimetry. It was possible to separate out the kinetics of formation of various phases which are obtained on crystallization of these glasses. The results are compared with the earlier investigations [1] in which the data were obtained by constant heating rate experiments. The crystallization of M-phase, Ni₃Nb and NbCr₂ phases could be described by Johnson-Mehl-Avrami kinetics. The activation energies for the formation of these phases were found to decrease in the same order. A decreasing activation energy with increasing transformed fraction (time) was also observed. The results are interpreted in light of the values obtained for Avrami exponents.     

玻璃纤维/聚丙烯复合材料界面研究

采用γ射线预辐照固相接枝和偶联剂分别对聚丙稀粉粒 (PP)和玻璃纤维 (GF)进行表面改性 .研究接枝PP在基体中的含量、玻璃纤维经偶联剂处理对复合材料层间剪切强度 (ILSS)、拉伸强度的影响 .通过SEM对复合材料的拉伸断口进行了分析 .     

聚酰胺胺改性碳纤维/尼龙复合材料制备及性能

为改善碳纤维增强尼龙复合材料(CFRPA)的加工流动性和力学性能,采用聚酰胺胺(PAMAM)树枝状高分子作为改性剂,通过熔融共混制备出碳纤维(CF)增强尼龙66(PA66)复合材料.采用DSC、万能试验机和SEM分别对改性后PA66的结晶行为、CFRPA的拉伸性能及微观组织形貌进行测试表征.结果表明,添加PAMAM可以...     

The influence of a polymeric nucleating additive on the crystallisation in glass fibre reinforced polyamide 6 composites

Short glass fibre reinforced polyamide 6 composites compounded with a polymeric nucleating additive based on polyamide 2.2 of different content (0, 0.1 and 0.2 wt%) and processed by injection moulding have been studied to characterise the additive effect on the crystallisation kinetics and morphology. Differential scanning calorimetrical and optical hot stage experiments have shown a significant increase in the overall crystallisation rate as well as the spherulitic growth, respectively with nucleating additive content. Additionally, the presence of glass fibres is proven to enhance crystallisation. Atomic force microscopy confirms the existence of a transcrystalline layer in the vicinity of the glass fibres. The nucleating additives have significantly decreased the spherulitic size from about 15 to 20 μm towards less than 5 μm, which leads to an improved fibre-to-matrix contact. Those morphological changes are seen as the reason for a strong increase in the Martens heat deflection temperature from 145 to 164 °C characterising an improved thermal stability.