Fiber-Matrix Interfacial Adhesion Improvement in Carbon Fiber-Bisphenol-A Polycarbonate Composites by Polymer Grafting

Fiber-matrix interfacial adhesion in thermoplastic composites is generally poor due to the lack of formation of strong covalent and/or ionic bonds between the generally inert thermoplastic resins and the surface of the reinforcing fiber. Adhesion can be improved by forming covalent linkages between the fiber and the matrix by grafting a polymer of appropriate compatibility, molecular weight, and sufficient density onto the surface of the fiber. We have grafted low molecular weight polycarbonate and polymethyl methacrylates onto the surface of carbon fibers and measured an improvement in the level of adhesion ranging from 25% to100% over the ungrafted composites. It was also observed that the level of improvement in adhesion appears to be independent of the molecular weight of the grafted polymer. Examination of the fracture surface of these composites reveals that the failure is cohesive in the matrix for the polymer grafted fiber composites, while it is adhesive for the ungrafted composites.     

利用单纤维碎裂法评价复合材料中纤维-基体界面剪切强度

1前言纤维增强复合材料必须具有较高的纤维一基体界面剪切强度,这是因为复合材料承受的载荷是通过纤维一基体界面剪应力传递给纤维的。不过,由于复合材料所要求的性能不尽相同,往往过高的界面剪切强度反而引起不利。例如,在纤维增强复合材料破坏过程中,龟裂面上纤维的拔起可以吸收破坏能,此时,如果界面剪切强度过高,纤维便不能被拔起只能断掉,这样一来,吸收的破坏能自然地会减少。因此,要提高复合材料的破坏能,就存在着最佳的界面剪切强度问题[1]。同样地,单向纤维增强复合材料的纤维轴向拉伸强度也存在着最佳的界面剪切强度,…     

Adhesion Improvement by UV Grafting onto Polyolefin Surfaces

High Density Poly(ethylene) (HDPE) and Poly(propylene) (PP) were subjected to several surface treatments, namely UV grafting of hydroxyethylmethacrylate (HEMA), plasma deposition of HEMA and oxygen plasma treatment. Treated surfaces were subjected to two post-treatment routines (extraction with ethanol and high temperature aging). The effect of these treatments on the adhesion of HDPE and PP to epoxy coated studs was evaluated by a pull test. No adhesion at all was recorded on untreated samples. On the other hand, all the treatments yield high bond strength in the case of HDPE: an average bond strength of about 290 kg/cm² and of about 200 kg/cm² was observed after UV grafting and plasma treatments. The treated samples were practically insensitive to post-treatments. As to PP, which undergoes chain scission in plasma, it is best treated by the comparatively milder conditions of UV grafting, which yields an average bond strength similar to that observed on HDPE. O₂ and HEMA-plasma-treated PP show a mean bond strength close to 50 kg/cm², and are deeply affected by the post-treatment routines.     

Adhesion Improvement by UV Grafting onto Polyolefin Surfaces

High Density Poly(ethylene) (HDPE) and Poly(propylene) (PP) were subjected to several surface treatments, namely UV grafting of hydroxyethylmethacrylate (HEMA), plasma deposition of HEMA and oxygen plasma treatment. Treated surfaces were subjected to two post-treatment routines (extraction with ethanol and high temperature aging). The effect of these treatments on the adhesion of HDPE and PP to epoxy coated studs was evaluated by a pull test. No adhesion at all was recorded on untreated samples. On the other hand, all the treatments yield high bond strength in the case of HDPE: an average bond strength of about 290 kg/cm² and of about 200 kg/cm² was observed after UV grafting and plasma treatments. The treated samples were practically insensitive to post-treatments. As to PP, which undergoes chain scission in plasma, it is best treated by the comparatively milder conditions of UV grafting, which yields an average bond strength similar to that observed on HDPE. O₂ and HEMA-plasma-treated PP show a mean bond strength close to 50 kg/cm², and are deeply affected by the post-treatment routines.     

多壁碳纳米管复合聚碳酸酯/苯乙烯系聚合物复合材料导电性能的研究

采用一步法将聚苯乙烯（PS）、苯乙烯-丙烯腈共聚物（SAN）和甲基丙烯酸甲酯-苯乙烯共聚物（MS）分别与聚碳酸酯（PC）、多壁碳纳米管（MWCNTs）熔融混合,得到PC/PS/MWCNTs、PC/SAN/MWCNTs和PC/MS/MWCNTs三种复合材料。透射电子显微镜和场发射扫描电子显微镜观察表明,MWCNTs选择性分散在PC相中,这与Sumita模型预测的结果完全吻合,且随着PS、SAN或MS含量的增加,体系的体积电阻率-苯乙烯系聚合物含量曲线能够很好地拟合到PC/MWCNTs体系的体积电阻率-MWCNTs有效体积浓度曲线上,体系的体积电阻率变化符合有效浓度的概念。     

Regeneration of Interfacial Adhesion in Fiber Reinforced Composites

Our studies of the regeneration of interfacial adhesion in micro-composites have shown that fiber/thermoplastic (aramid/polycarbonate) bonds can be completely regenerated, the degree of regeneration depending on both time and temperature of heating. Complete regeneration requires high temperatures, suggesting that mechanical interlocking resulting from flow of heat-softened resin into fiber surface crevices may be the primary mechanism of bond strength regeneration. Only partial regeneration of fiber/thermosetting resin (epoxy with aramid and carbon fibers) bond strength has been achieved, and this appears to be independent of fiber and reheating time. Apparently, the viscoelastic behavior of the resin is a critical factor in bond strength regeneration.     

Evidence of Acid-Base Interfacial Adducts in Various Polymer/Metal Systems by IRAS: Improvement of Adhesion

The physical interactions of polymers with inorganic substrates are determined by two major contributions: Van der Waals forces and acid-base interactions, taken in the most general “Lewis” electron acceptor-donor sense. The present work shows that the work of adhesion can be very appreciably increased by the creation of interfacial acid-base interactions. Practically, polymers such as poly(ethylene-co-vinyl acetate) (EVA), terpene-phenol resins (TPR), and their blends, were solution cast on basic and acidic substrates. The nature of the interfacial bonds and the enthalpy of adduct formation through electron exchange are evidenced by Fourier transform infrared reflection-absorption spectroscopy (IRAS). Moreover, it is shown that, on the one hand, modification of the electron donor ability of the polymer functionalities reveals the amphoteric character of the substrate and, on the other hand, modification of the electron donor ability of the substrate changes the nature of the species involved in interfacial adduct formation. Then, practical adhesion tests were carried out in order to correlate the nature and strength of interfacial acid-base bonds with simultaneous increases in adhesive strengths. Thermodynamic considerations allowed us to propose estimated values of the acid-base work of adhesion, W^ab, and of the density of acid-base sites, n^ab.     

Evidence of Acid-Base Interfacial Adducts in Various Polymer/Metal Systems by IRAS: Improvement of Adhesion

The physical interactions of polymers with inorganic substrates are determined by two major contributions: Van der Waals forces and acid-base interactions, taken in the most general “Lewis” electron acceptor-donor sense. The present work shows that the work of adhesion can be very appreciably increased by the creation of interfacial acid-base interactions. Practically, polymers such as poly(ethylene-co-vinyl acetate) (EVA), terpene-phenol resins (TPR), and their blends, were solution cast on basic and acidic substrates. The nature of the interfacial bonds and the enthalpy of adduct formation through electron exchange are evidenced by Fourier transform infrared reflection-absorption spectroscopy (IRAS). Moreover, it is shown that, on the one hand, modification of the electron donor ability of the polymer functionalities reveals the amphoteric character of the substrate and, on the other hand, modification of the electron donor ability of the substrate changes the nature of the species involved in interfacial adduct formation. Then, practical adhesion tests were carried out in order to correlate the nature and strength of interfacial acid-base bonds with simultaneous increases in adhesive strengths. Thermodynamic considerations allowed us to propose estimated values of the acid-base work of adhesion, W^ab , and of the density of acid-base sites, n^ab .     

电泳沉积纳米粒子增强树脂基碳纤维复合材料界面性能的研究进展

介绍了电泳沉积的基本原理,纳米粒子悬浮液的分散机制,并详细讨论了电泳沉积碳纳米管、氧化石墨烯、二氧化硅、纳米纤维等纳米粒子在碳纤维增强树脂基复合材料界面改性方面的研究进展。     

炭黑填充型导电树脂的应用研究进展

综述了炭黑填充型导电树脂的特性,介绍了影响炭黑填充型导电树脂导电性的重要因素,包括加工工艺,基体与填料的关系等,讨论了研究现状及其技术进展,对其导电理论作了简要的介绍.     

聚合物接枝纳米碳纤维/聚苯乙烯复合材料的制备与力学性能研究

采用自由基聚合方法,在纳米碳纤维(CNF)表面接枝聚丙烯酸正丁酯(PnBA)和聚苯乙烯(PS),利用接枝的嵌段聚合物作为大分子偶联剂制备CNF/PS复合材料。红外傅里叶变换光谱(FT-IR)研究表明,嵌段聚合物PnBA-b-PS被成功地接枝到CNF表面。扫描电子显微镜(SEM)和力学性能测试结果显示,CNF与PS复合材料界面结合得到改善,力学性能明显提高。     

电化学氧化表面处理提高粘胶基碳纤维的界面粘结性能

通过动力学的方法研究了电化学处理前后接触角的变化 ,并用其表征碳纤维表面润湿性能的改变 ;通过拔出实验测定电化学处理前后碳纤维与树脂之间粘结性能的变化。结果表明 ,电化学处理后 ,碳纤维表面的润湿性大大改善 ,碳纤维与树脂的粘结程度提高至原来的 14 0 %～ 160 % ;研究还发现 ,不同种类的电解质电化学处理后对碳纤维表面的润湿性及其拔出强度的影响不同 ,( NH4) 2 SO4处理的碳纤维的润湿性能和拔出强度最好 ,H2 SO4处理的润湿性较之 Na OH的好 ,但拔出强度却不如 Na OH处理的高。且拔出强度越高 ,其断裂的模式趋向于单剪切断裂 ,拔出强度降低 ,其断裂变为多剪切断裂甚至为粉碎性断裂。     

Adhesion: Comparison Between Physico-chemical Expected and Measured Adhesion of Oxygen-plasma-treated Carbon Fibers and Polycarbonate

The adhesive interaction between oxygen-plasma-treated, polyacrylonitrile-based, high-tensile-strength carbon fibers and a polycarbonate matrix has been studied. Several models have been used to predict the impact of the plasma treatment process on the strength of adhesion between both jointing partners. These approaches have been the thermodynamic work of adhesion which was calculated from the solid surface tensions, based on the results of contact angle measurements versus test liquids, the contact angle which was directly obtained via polycarbonate melt droplets on single carbon fibers and the zeta (?)-potential data provided by streaming potential measurements. The results have been compared with the interfacial shear strength determined from the single-fiber fragmentation test. Additionally, the single-fiber tensile strength of the oxygen-plasma-treated carbon fibers was determined.

We confirmed that any physico-chemical method on its own fails to describe exactly the measured adhesion. However, for the investigated system, the conscientious interpretation of the data obtained from wetting measurements, in conjunction with the thermodynamic approach, is sufficient to predict the success of a modification technique which has been applied to one component in order to improve adhesion.     

Adhesion: Comparison Between Physico-chemical Expected and Measured Adhesion of Oxygen-plasma-treated Carbon Fibers and Polycarbonate

The adhesive interaction between oxygen-plasma-treated, polyacrylonitrile-based, high-tensile-strength carbon fibers and a polycarbonate matrix has been studied. Several models have been used to predict the impact of the plasma treatment process on the strength of adhesion between both jointing partners. These approaches have been the thermodynamic work of adhesion which was calculated from the solid surface tensions, based on the results of contact angle measurements versus test liquids, the contact angle which was directly obtained via polycarbonate melt droplets on single carbon fibers and the zeta (ς)-potential data provided by streaming potential measurements. The results have been compared with the interfacial shear strength determined from the single-fiber fragmentation test. Additionally, the single-fiber tensile strength of the oxygen-plasma-treated carbon fibers was determined.

We confirmed that any physico-chemical method on its own fails to describe exactly the measured adhesion. However, for the investigated system, the conscientious interpretation of the data obtained from wetting measurements, in conjunction with the thermodynamic approach, is sufficient to predict the success of a modification technique which has been applied to one component in order to improve adhesion.     

Interfacial Bonding and Environmental Stability of Polymer Matrix Composites

Recently developed adsorption-interdiffusion (A-I) theory of adhesion is employed to isolate the (London) dispersion γ_i,j^d and (Keesom) polar γ_i,j^p components of the excess interfacial free energy γ_i,j=γ_i,j^d+γ_i,j^p at the fiber-matrix interface in polymer matrix composites. For adsorption bonded interfaces the theory defines a new method of mapping the surface energy effects of an immersion phase upon the Griffith fracture energy γ_G. The stability of interfacial bonding between graphite fiber-epoxy matrix is defined in terms of the theoretical model and experimentally evaluated by accelerated aging studies which monitor changes in fracture energy for crack propagation perpendicular to the fiber axis. Applications of the model to control fiber surface treatments and select matrix components for optimized bond strength and environmental resistance is discussed.     

Interfacial Bonding and Environmental Stability of Polymer Matrix Composites

Recently developed adsorption-interdiffusion (A-I) theory of adhesion is employed to isolate the (London) dispersion γ_i,j ^d and (Keesom) polar γ_i,j ^p components of the excess interfacial free energy γ_i,j=γ_i,j ^d+γ_i,j ^p at the fiber-matrix interface in polymer matrix composites. For adsorption bonded interfaces the theory defines a new method of mapping the surface energy effects of an immersion phase upon the Griffith fracture energy γ_G. The stability of interfacial bonding between graphite fiber-epoxy matrix is defined in terms of the theoretical model and experimentally evaluated by accelerated aging studies which monitor changes in fracture energy for crack propagation perpendicular to the fiber axis. Applications of the model to control fiber surface treatments and select matrix components for optimized bond strength and environmental resistance is discussed.     

Properties of Recycled Polycarbonate/Waste Silk and Cotton Fiber Polymer Composites

Polymer-based composite structures have advantages over many other materials. The most important advantage is the higher mechanical properties obtained from the composites when supported by fiber reinforcement. The mechanical and thermal properties of fiber-reinforced composite structures are affected by the amount of fibers in the structures, orientation of the fibers and fiber length. Silk and cotton fibers are used in many fields but especially in clothing and textiles. However, there is not enough research on their usage as reinforcement fibers in composite structures. Silk fibers as a textile material have better physical and mechanical properties than other animal fibers. The improvement of the mechanical and physical properties of the composite structures allows them to be used in many areas. From economical, technological and environmental points of view, the improvement of mechanical and physical properties of polymeric materials are receiving much attention in recent studies.

In this study, different application areas were chosen to evaluate the waste silk and waste cotton rather than classic textile applications. Waste silk and cotton and recycled polycarbonate polymer were mixed and as a result composite structures were obtained. Silk and cotton waste fiber dimensions were in between 1 mm, 2.5 mm and 5 mm. The recycled PC/silk and cotton wastes were mixed in the rates of 97%/3%. Mixtures were prepared by twin-screw extruder. Tensile strength, % elongation, yield strength, elasticity modulus, Izod impact strength, melt flow index (MFI), heat deflection temperature (HDT) and Vicat softening temperature properties were determined. To determine the materials' thermal transition and microstructure properties, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used.     

Adhesion Improvement of Glass-Fibre-Reinforced Polyester Composites by Gliding Arc Discharge Treatment

A gliding arc is a plasma that can be operated at atmospheric pressure and applied for plasma surface treatment for adhesion improvement. In the present work, glass-fibre-reinforced polyester plates were treated using an atmospheric pressure gliding arc discharge with an air flow to improve adhesion with a vinylester adhesive. The treatment improved wettability and increased the polar component of the surface energy and the density of oxygen-containing polar functional groups at the surfaces. Double cantilever beam specimens were prepared for fracture mechanics characterisation (fracture resistance as a function of nominal mode mixity) of the laminate adhesive interface. It was found that gliding arc treatment significantly increases the interfacial fracture energy and fracture resistance in comparison with a standard peel ply treatment, although the mixed mode fracture energy of the gliding arc treated specimen was not as high as that of the laminate itself.     

碳纳米管/聚合物复合材料的研究进展

综述了碳纳米管/聚合物复合材料的研究进展,介绍了碳纳米管/聚合物复合材料的制备方法,特别强调了碳纳米管在聚合物基体中的分散和排列;综述了碳纳米管/聚合物复合材料研究在力学、电学、热学、阻燃性能等方面所取得的进展,并详细讨论了碳纳米管的长径比、碳纳米管在聚合物基体中的分散效果及排列对碳纳米管/聚合物复合材料性能的影响;最后探讨了碳纳米管/聚合物复合材料进一步发展所面临的机遇和挑战.     

炭黑填充复合型导电聚合物的研究进展

在聚合物基体中添加导电炭黑以降低聚合物的电阻率,是目前最为常用的制备导电聚合物的方法。综述了炭黑填充复合型导电聚合物的研究进展。对影响复合材料导电性能及渗滤阈值的因素进行了讨论。重点介绍了使用共混聚合物作基体,并利用炭黑在共混基体中的非均相分布来降低炭黑用量的研究。