短玻璃纤维增强聚丙烯复合材料的制备及其力学性能的研究

采用双螺杆挤出机通过熔融共混的工艺路线制得短玻璃纤维增强聚丙烯(PP)复合材料,通过激光粒度分布仪对复合体系中的玻璃纤维的长度进行了测试,同时对复合材料的主要力学性能进行了表征。结果表明:随着短玻璃纤维含量的增加,复合材料中短玻璃纤维的长度平均径有所减小;随着短玻璃纤维含量的增大,复合材料的拉伸强度、冲击强度都大幅度增加,硬度有所增加;当短玻璃纤维质量分数为40%时,短玻璃纤维增强PP复合材料拉伸强度为64.39 MPa,与纯PP相比提高了74%,冲击强度为5.8 kJ/m~2,与纯PP相比提高了174%,硬度为85,与纯PP相比提高了11%。     

Parameters regulating interfacial and mechanical properties of short glass fiber reinforced polypropylene

The performance of thermoplastic composites is known to depend on the intrinsic properties of the two composite components, the quality of the fiber–matrix interface, and the crystalline properties of their matrix. The objective of this work is to characterize the effect of the addition of modified polypropylene (PP) and silane coupling agent on the mechanical and interfacial properties of short fiber reinforced PP composites. Differential scanning calorimetry (DSC), single fiber composite fragmentation tests (SFC), and mechanical testing are used to understand the different parameters regulating the interfacial properties of composites. No influence of the modified PP on the level of crystallinity is observed. Some differences in the size of the spherulites are observed for acrylic acid grafted PP (PP‐g‐AA). Those samples also show lower mechanical properties in spite of good interfacial interactions. Maleic anhydride grafted PP (PP‐g‐MAh) leads to better mechanical performances than PP‐g‐AA. A high MAh content PP‐g‐MAh grade with low viscosity is the best polymeric additive used in the present work. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2047–2060, 2000     

Impact fracture behavior of injection molded long glass fiber reinforced polypropylene

In this work the variation in Izod impact strength with spatial location was examined for injection molded long glass fiber polypropylene composite plaques. These plaques were fabricated at different sets of processing conditions, with injection speed and melt temperature being varied. By carefully machining test specimens, fifteen different plaque locations both in the in-flow and cross-flow directions were tested. The part morphology was described with the use of characteristic layer thickness ratios, i.e., the shell and the core to part thickness ratios, which were measured experimentally. It was shown that the variation in impact strength with sample location strongly correlates to shell to part thickness ratio. In addition, it was observed that different failure mechanisms exist for different fiber orientations, i.e., for fibers oriented transversely to the crack plane or on the crack plane itself. Scanning electron microscopy (SEM) of the fracture surface was conducted and the results supported our findings on the microstructural level.     

Impact behavior of a short glass fiber reinforced thermoplastic polyurethane

The temperature dependence of critical strain energy release rate (G_c′) and standardized Charpy notched impact strength (CNIS) were measured for a thermoplastic polyurethane (TPUR) reinforced with 30 wt% of short glass fibers (SGF) over a temperature interval ranging from −150°C 23°C (RT) at two strain rates, 70 and 150 s⁻¹, respectively. Fractographic observation of fracture planes was used to qualitatively assess the fracture modes and mechanisms. Adhesion between the reinforcement and the matrix was excellent and the integrity of the fiber‐matrix interfacial contact was relatively insensitive to exposure to hydrolysis during the immersion in boiling water for 100 hours. At temperatures above −30°C, there was a large extent of plastic deformation in the vicinity of crack planes while at temperatures below −50°C, the extent of plastic deformation was substantially reduced. This resulted in a change in the major energy dissipation mechanism and led to a decrease of both CNIS and G_c′ values for SGF/TPUR composites. It was suggested that the plastic deformation of TPUR matrix in the immediate vicinity of glass fibers was the primary source of energy dissipation at temperatures above −30°C, while the friction and fiber pull‐out was the main dissipative process below −50°C. Over the whole temperature interval investigated, greater G_c′ values were obtained at higher strain rate of 150 s⁻¹, without any significant change in the fractographic patterns observed on the fracture planes. The CNIS/G_c′ ratio, used to assess suitability of CNIS for comparison of materials, changed with temperature substantially suggesting that the functional dependences of CNIS and G_c′ on temperature differ substantially. Hence, CNIS data do not provide a reliable base for material selection and for design purposes in this case.     

玻璃纤维增强聚丙烯复合材料的研究进展

综述了长、短玻璃纤维增强聚丙烯（GFRPP）复合材料的研究进展,总结出纤维含量、纤维长度及分布、纤维取向及分布、纤维与基体界面结合和改性等均为影响GFRPP性能的因素。在复合材料中,长度大于临界长度的玻璃纤维对材料的强度才有作用;增强玻璃纤维与聚丙烯的界面结合也是提高增强效果的有效手段。     

玻纤增稿聚丙烯的研制

通用热塑性增强复合材料玻璃纤维增强聚丙烯（PP）性价比高，应用广泛。本文讨论了偶联剂、增容剂、加工工艺条件等因素对玻璃纤维增强PP性能的影响。结果表明，运用正确的偶联剂和增容剂处理玻璃纤维、增加玻璃纤维长度、适当提高玻璃纤维增强PP的挤出加工温度、适当降低挤出螺杆转速和注射速率均可提高玻纤增强PP的综合性能。     

长玻璃纤维增强聚丙烯复合材料的韧性

以玻璃纤维和聚丙烯为原料,制备了长玻璃纤维增强聚丙烯(LFT-PP)复合材料,研究了基体韧性、纤维长度和界面相容剂对LFT-PP韧性的影响。结果表明LFT-PP韧性随基体韧性增加而增加;当玻璃纤维长度从2.06mm增加到4.66mm时,LFT-PP的悬臂梁缺口冲击强度从134.4J/m提高到238.0J/m,增加了约80%;添加界面改性剂降低了LFT-PP悬臂梁缺口冲击强度,从311.4J/m降为181.8J/m。     

Microscopical damage mechanisms in glass fiber reinforced polypropylene

The damage mechanisms in two structurally different glass mat reinforced polypropylene materials were studied. In situ microscopy was applied during the tensile testing of thin notched sheets. Micrographs of the damage processes in the two materials are presented. The major points of damage initiation were transversely oriented fibers and fiber bundles. In the swirled mat material, cracks grew along the fiber bundles; crack formation and growth was relatively unaffected by macroscopical stress concentration. In the short fiber material, crack growth occurred at the notch. In both materials the maximum load was determined by the fibers oriented in the longitudinal direction. The different damage mechanisms were interpreted in terms of damage zone size. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1319–1327, 1998     

Fracture toughness of injection molded glass fiber reinforced polypropylene

The fracture behavior of polypropylene reinforced with 30% by weight of short glass fibers was studied using single and double feed plaque moldings. Plaques were injection molded using several gate types and gate positions. Fracture toughness K_c, was calculated at different positions in the plaque moldings using single edge notched tension specimens. Fracture toughness was assessed in the directions parallel and perpendicular to the mold fill direction through measurements of the load to produce complete fracture. Results indicated that the value of fracture toughness is affected by the type of gate as well by size of gate. Position of the specimen also affected fracture toughness. Generally, specimens taken from positions near cavity walls gave higher toughness values than those taken from the center of the moldings. Furthermore, fracture toughness in the transverse direction was consistently higher than in the melt flow direction. Finally, in the case o double feed moldings, a much higher fracture toughness was obtained when the initial crack was perpendicular to the weld line than when it was placed inside the weld line.     

短玻纤增强ABS复合材料的研制

介绍短玻纤维增强ABS复合材料的生产工艺,实验对比了处理玻纤用偶联剂种类和加入量、玻纤含量、ABS种类及抗冲改性剂加入量对复合材料性能的影响,结果表明,玻纤用质量分数为1.5%的偶联剂KH550处理,可增强9715A ABS,同时加入质量分数为2%抗冲改性剂的可得到综合性能较好的复合材料。     

The prediction of flow and orientation behavior of short fiber reinforced melts in simple flow systems

A model for the prediction of changes in fiber orientation in simple flows of fiber suspensions is proposed. Fiber interactions are modeled as randomizing forces over the rotation of fibers in closed orbits in simple shear. The resulting Fokker-Planck type convection-diffusion equation in orientation space is solved using a finite difference technique. The solution technique permits the use of periodic boundary condition for the convection-diffusion equation and different initial conditions for the orientation distribution. The model predictions for simple shear flow demonstrate the interaction between the structural changes and the bulk rheological properties. The effect of non-Newtonian fluid properties on the orientation distribution was also incorporated at the slow flow limit. Structural changes are assumed to be irreversible. The irreversibility is incorporated through an orientation distribution dependent diffusion coefficient.     

Thermal conductivity of glass fiber reinforced polypropylene under high pressure

The thermal conductivities of molten polypropylene and its glass fiber composites were measured by the compensating hot wire method. The testing apparatus empolyed was designed and tested in our laboratory. The measurements were carried out with temperatures ranging from 170 to 230°C and pressures from 1 to 2000 kg/cm². The results show that the thermal conductivity increases with increasing pressure and glass fiber content, but is almost independent of temperature. The thermal conductivity data were fitted satisfactorily with a proposed empirical equation for polypropylene and Lewies-Nielsen equation for the composites, respectively.     

Modulus of short carbon and glass fiber reinforced composites

A theoretical model for a short fiber reinforced composite is proposed. The composite is assumed to consist of an aggregate of sub-units, each sub-unit possessing the elastic properties of a reinforced composite in which the fibers are continuous and fully aligned. The elastic constants of a partially oriented composite are then calculated by the Voigt and Reuss averaging procedures, giving upper and lower bounds respectively for the composite modulus. Comparison is made with experimental data for such composites. The measured modulus of glass and carbon fiber composites is found to be given by the Reuss or lower bound, to a good approximation compared with the difference between the bounds, for fiber orientations ranging from almost isotropic to highly aligned.     

Fracture behavior of glass fiber reinforced polymer composite

Chopped strand glass fiber reinforced particle-filled polymer composite beams with varying notch-to-depth ratios and different volume fractions of glass fibers were investigated in Mode I fracture using three-point bending tests. Effects of polyester resin content and glass fiber content on fracture behavior was also studied. Polyester resin contents were used 13.00%%, 14.75%, 16.50%, 18.00% and 19.50%, and glass fiber contents were 1% and 1.5% of the total weight of the polymer composite system. Flexural strength of the polymer composite increases with increase in polyester and fiber content. The critical stress intensity factor was determined by using several methods such as initial notch depth method, compliance method and J-integral method. The values of K_IC obtained from these methods were compared.     

Performance-property of novel glass fiber reinforced polypropylene compounds and their applications

The objective of this work was to investigate the property enhancement of polypropylene compounds due to glass fiber reinforcement at various levels. General trends in properties, performance and application were carefully established and surveyed. Second generation metallocene-based glass fiber reinforced polypropylene compounds were also studied in terms of their “property-performance” characteristic and compared to the original series. Addition of nylon to glass fiber reinforced polypropylene compounds was investigated as a further possible avenue for creating a new family of polymer alloys. Comparisons of properties, advantages, and applications were made.     

Mechanisms of fatigue in short glass fiber reinforced polyamide 6

An adaptation to existing failure models for fatigue fracture of short fiber reinforced thermoplastics is presented, based on results using some new experimental methods. These results lead to the following conclusion: Cracks in polyamide remain bridged (by plastically drawn matrix material and/or fibers) until just before final fracture. Important is the conditioning of the polyamide: conditioned to equilibrium water content, this mechanism occurs, but not when it is dry as molded. Fatigue damage measurements were done on thin foils cut from the fatigued specimen. When tensile tested, these foils show a change in both strength and fracture strain after fatigue. Further observations during the experiments and SEM fractography strengthen the conviction that fatigue damage initiates and grows in the form of bridged cracks. A correlation between tensile strength and fatigue strength was found; the degree of fiber alignment has a similar effect on both tensile and fatigue properties.     

Mixed-mode fracture behavior of glass fiber reinforced polymer concrete

Fracture toughness of chopped strand glass fiber reinforced particle-filled polymer composite beams was investigated in Mode I and Mode III loading conditions using three-point bend tests. Effects of crack angles on fracture behavior were also studied. The specimens, which have inclined crack at an angle θ to the axis of the specimens, were used to carry out the tests. The specimens were tested with inclination angles 30°, 45°, 60° and 75°. The results are compared with the values of K_IC obtained using conventional (θ=90° ) specimens. In addition, J integrals were also determined. J_IC increases continuously with increasing in crack angle from θ=30° to θ=90°. In contrast, J_IIIC decreases with the crack inclination angle θ from 30° to 90°.     

短切玻璃纤维增强环氧树脂胶粘剂的耐温性能研究

以短切玻璃纤维作为环氧树脂(EP)的增强剂,并以PA650/T31(聚酰胺650/改性胺类曼尼希型固化剂)作为复合固化剂,制备了综合性能良好的胶粘剂。研究结果表明:复合固化剂可有效改善胶粘剂的性能,当m(EP)∶m(PA650)∶m(T31)=10∶4∶2、常温固化时间为18 h时,胶粘剂的拉伸剪切强度相对最大(15.64 MPa);加入1.2%玻璃纤维的胶粘剂在230℃时的拉伸剪切强度提高了32.06%;玻璃纤维增强EP使得胶粘剂的热分解温度提升至300℃,同时热失重率从63.55%下降至56.09%。     

A comparison of short glass fiber reinforced polypropylene plates made by conventional injection molding and using shear controlled injection molding

This paper describes a comparison of the fiber orientation structures and resulting elastic properties of samples of short glass fiber filled polypropylene made by conventional injection molding and by the SCORIM (Shear Controlled Orientation in Injection Molding) process developed at The University of Brunel. The 3D fiber orientation distributions of the composites were measured using a unique transputer based image analysis system developed at The University of Leeds. The mechanical properties of the samples were characterized using an ultrasonic velocity technique, which allows a full set of elastic constants to be determined for each material. The link between fiber orientation distributions and measured elastic properties was then investigated using theoretical models developed in this laboratory.