An investigation of glass fibre/polypropylene interface strength and its effect on composite properties

The structure and properties of the fibre/matrix interface region play a major role in determining the performance of structural composites. One of the main factors which influences the interface region is the fibre surface coating applied by the manufacturer. The influence of these coatings on the interfacial strength of glass fibre/polypropylene composites has been evaluated using the single fibre pull-out test. Results indicate that silane coupling agent alone has little effect on the interfacial strength. However, in combination with some other component of the coating, significant effects were found. The level of glass fibre/polypropylene interfacial strength varied by an order of magnitude depending on the nature of the fibre coating. Furthermore, the flexural strength of a unidirectional glass-reinforced polypropylene laminate varied by a factor of two depending on the type of glass fibre coating. The flexural strength results correlated well with the level of interfacial shear strength as measured by the single fibre pull-out test. The interfacial shear strength could also be correlated with the level of fibre surface coverage given by the fibre coating as measured using X-ray photoelectron spectroscopy.     

Mechanical and thermal properties of filamentary-reinforced structural composites at cryogenic temperatures 2: Advanced composites

The low-temperature mechanical and thermal properties of advanced-fibre reinforced structural composites are reviewed. The magnitude and range of particular properties are discussed with respect to composite type and temperature. A property-material cross reference is given with a 128-entry bibliography. This is Part 2 of a two-part series Part 1 considered glass-reinforced composites.     

Chopped glass and recycled newspaper as reinforcement fibers in injection molded poly(lactic acid) (PLA) composites: A comparative study

Natural/bio-fibers are replacing synthetic reinforcements traditionally used for the preparation of the environmentally friendly composites. Composite materials are also replacing conventional materials in various fields due to their ease of processability. Chopped glass fiber- and recycled newspaper cellulose fiber (RNCF)- reinforced poly(lactic acid) (PLA) composites were processed using a full size twin-screw extruder and an injection molder. Additionally, a glass-reinforced polypropylene (PP) composite was compounded and molded, and compared to PLA/RNCF and PLA/glass fiber composites. The tensile and flexural moduli of RNCF- reinforced composites were significantly higher when compared to the virgin resin. The morphology, evaluated by scanning electron microscopy, indicated uniform dispersion of both fibers in the PLA matrix. The mechanical and thermo-physical properties of PLA/RNCF, PLA/glass and PP/glass fiber composite were studied and compared using dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). DMA results confirmed that the storage and loss moduli of the PLA/RNCF composites increased with respect to the pure polymer, whereas the mechanical loss factor (tan delta) decreased. The results of the TGA experiments indicated that the addition of fibers increased the thermal stability of the biocomposites compared to neat PLA. The heat defection temperature of PLA/RNCF was found to be comparable to that of the glass fiber-reinforced PLA composites. Such studies are of great interest in the development of environmentally friendly composites from biodegradable polymers.     

Biocomposites from Musa textilis and polypropylene: Evaluation of flexural properties and impact strength

Abaca (Musa textilis)-reinforced polypropylene composites have been prepared and their flexural mechanical properties studied. Due to their characteristic properties, M. textilis has a great economic importance and its fibers are used for specialty papers. Due to its high price and despite possessing very distinctive mechanical properties, to date abaca fibers had not been tested in fiber-reinforced composites. Analysis of materials prepared showed that, in spite of reduced interface adhesion, flexural properties of the PP composites increased linearly with fiber content up to 50 wt.%. Addition of a maleated polypropylene coupling agent still enhanced the stress transfer from the matrix to the reinforcement fiber. As a result, composites with improved flexural properties were obtained. The mechanical properties of matrix and reinforcing fiber were evaluated and used for modelling both the flexural strength and modulus of its composites. In addition, the impact strength of materials was evaluated. Comparison with mechanical properties of composites reinforced with fiberglass points out the potentiality of abaca-reinforced polypropylene composites as suitable substitutes in applications with low impact strength demands.     

聚丙烯/CaCO_3复合材料组织性能分析

为了拓展聚丙烯材料的应用,在对CaCO3粉体进行表面偶联处理后,混入聚丙烯中,制成聚丙烯/CaCO3复合材料。通过透射电镜、X射线衍射仪、偏光显微镜、电子万能试验机等仪器设备研究了样品的显微组织及其力学性能。结果表明:CaCO3粉体有异相成核剂的作用,使球晶尺寸变小,结晶度有所提高,在聚丙烯基体中产生明显的增强增韧效果。经改性后的聚丙烯/CaCO3复合材料显微组织得到改善,力学性能有所提高。     

无机组合粒子/聚丙烯复合材料的制备与协同效应

提出了利用无机组合粒子的协同效应增强增韧聚丙烯的新思路。硅灰石(W)、滑石(T)、重晶石(B)、碳酸钙(C)、石英(Q)与纳米氧化铝(N)等无机粒子经组合、超细并表面处理制得无机组合粒子(CIPs)；CIPs与聚丙烯(PP)混合、挤出并注射成型制备CIPs／PP复合材料标准试件，并按相应国标检测材料性能。结果表明，无机组合粒子填充PP材料的综合性能明显高于相应单一粒子填充的PP材料；纳米氧化铝的添加降低了熔体粘度，改善了填充体系的流变性能，实现了聚丙烯塑料的同时增强增韧。     

Post-fire mechanical properties of marine polymer composites

Changes to the tensile and flexure properties of marine-grade glass-reinforced polyester, vinyl ester and resole phenolic composites after exposure to radiant heat are investigated. The properties were determined at room temperature after the composites had been exposed to heat fluxes of 25–100 kW/m² for 325 s or to a heat flux of 50 kW/m² for increasing times up to 1800 s. The stiffness and failure load of all three composites decreased rapidly with increasing heat flux or time due mainly to the thermal degradation of the resin matrix. The post-fire tension and flexure properties of the resole phenolic composite were similar to the properties of the other composites, despite its superior fire resistance. Models are presented for determining the post-fire mechanical properties of fire-damaged composites, and are used to estimate the reductions in failure load of composite ship materials caused by fire.     

Mechanical performance optimization through interface strength gradation in PP/glass fibre reinforced composites

A new design for thermoplastic composites based on the gradation of the interlaminar interface strength (IGIS) has been developed with the aim of coupling high impact resistance with high static properties. IGIS laminates have been prepared by properly alternating layers of woven fabric with layers of compatibilized or not compatibilized polymeric films. To prove the new concept, polypropylene (PP) and glass fibres woven fabrics have been used to prepare composites by using the film stacking technique. Maleated PP, able to compatibilize polypropylene with glass fibres, has been used to manage the interface strength layer by layer.The flexural and low-velocity impact characterizations have shown that the presence of the coupling agent in conventional composite structures (prepared with fully compatibilized polymeric layers) improves the static flexural properties through the strengthening of the matrix/fibre interface but considerably lowers the low velocity impact resistance of the composite, in terms of maximum load before fibre breakage and recovered energy after impact. The use of the IGIS design, that grade the interface strength through the laminate thickness, allows to prepare composites with both high flexural properties and high impact resistance, without affecting the balance and type of the reinforcement configuration.     

Effect of glass fiber hybridization on properties of sisal fiber–polypropylene composites

Natural fiber reinforced polymer composites became more attractive due to their light weight, high specific strength, and environmental concern. However, some limitations such as low modulus, poor moisture resistance were reported. This study aimed to investigate the effect of glass fiber hybridization on the physical properties of sisal–polypropylene composites. Polypropylene grafted with maleic anhydride (PP-g-MA) was used as a compatibilizer to enhance the compatibility between the fibers and polypropylene. Incorporating glass fiber into the sisal–polypropylene composites enhanced tensile, flexural, and impact strength without having significant effect on tensile and flexural moduli. In addition, adding glass fiber improved thermal properties and water resistance of the composites.     

Mechanical properties of wood–fiber reinforced polypropylene composites: Effect of a novel compatibilizer with isocyanate functional group

Natural fibers are increasingly being used as reinforcement in commercial thermoplastics due to their low cost, high specific properties and renewable nature. While the maleic anhydride modified polypropylene (MAPP) is most commonly used as compatibilizer to improve interfacial adhesion between hydrophilic wood–fibers and hydrophobic polypropylene, in this study, a novel compatibilizer (m-TMI-g-PP) with isocyanate functional group was synthesized by grafting m-isopropenyl-α,α-dimethylbenzyl-isocyanate (m-TMI) onto isotactic polypropylene (PP) in a twin screw extruder. The effect of filler concentration on the mechanical properties of wood–fiber filled composites, prepared by using m-TMI-g-PP as the compatibilizer, was investigated. The addition of the compatibilizer resulted in greater reinforcement of composites, as indicated by the improvement in mechanical properties. Tensile strength of composites so prepared increased by almost 45%, whereas 85% increase in flexural properties was observed. However the addition of wood–fibers resulted in a decrease in elongation at break and impact strength of the composites.     

聚丙烯基纳米复合材料的物理性能

综述了聚丙烯(PP)基纳米复合材料的动态力学性能、结晶性能、阻燃性能、导电性能、分散性等物理性能的国内外研究进展。相对纯高分子材料或传统填充复合材料，聚丙烯纳米复合材料具有快的结晶速率、高的结晶温度和阻燃性能，纳米复合材料中聚丙烯结晶速率和结晶温度的提高归结于高表面积的纳米粒子存在强的异相成核作用，阻燃性能的提高归结于热稳定性提高和在少量填料时就可形成绝缘不燃炭层。     

PP/Talc复合材料的非等温结晶动力学

用差示扫描量热法(DSC)研究聚丙烯(PP)及PP／Talc复合材料的非等温结晶过程,加入滑石粉后,PP／Talc的结晶速率、结晶度得到明显提高。结合Avrami和Ozawa方程得出一个适合于非等温的结晶动力学方程,并由此获得PP／Talc复合材料的非等温结晶动力学参数,计算表明Talc能促进PP材料的结晶。     

Correlation of constitutive response of hybrid textile reinforced concrete from tensile and flexural tests

This papers addresses the disparities that exist in measuring the constitutive properties of thin section cement composites using a combination of tensile and flexural tests. It is shown that when the test results are analyzed using a simplified linear analysis, the variability between the results of tensile and flexural strength can be as high as 200–300%. Experimental results of tension and flexural tests of laminated Textile Reinforced Concrete (TRC) composites with alkali resistant (AR) glass, carbon, aramid, polypropylene textile fabrics, and a hybrid reinforcing system with aramid and polypropylene are presented. Correlation of material properties is studied analytically using a parametric model for simulation of flexural behavior using a closed form solution based on tensile stress–strain constitutive relation. The flexural load carrying capacity of TRC composites is computed using a back-calculation approach, and parameters for a strain hardening material model are obtained using the closed form equations. While the parametric model over predicts the simulated tensile response for carbon and polypropylene TRCs, predictions are however consistent with experimental trends for aramid and glass TRCs. Detailed discussion of the differences between backcalculated and experimental tensile properties is presented. Results can be implemented as average moment–curvature relationship in the structural design and analysis of cement composites.     

Debonding and friction at fibre-polymer interfaces. I: Criteria for failure and sliding

Renewed interest in the interface or interphase between fibres and composites has recently led to the development of new methods for measuring interface properties. These are providing useful comparative data, with relatively simple techniques. The stresses and energies associated with some of these tests are critically reviewed, and it is shown that the different tests are measuring different properties. For example, the single fibre ‘composite’ test, in which the fibre is fragmented, appears to be providing frictional data only. In contrast, the fibre pull-out test can provide debonding energies, and data on friction after debonding. The results of this test suggest that the governing criterion for interface failure in carbon-epoxies and glass-reinforced epoxy and polyester resins is based on energy rather than stress.     

Interply hybrid composites with carbon fiber reinforced polypropylene and self-reinforced polypropylene

The focus of the present study is on hybrid composites with interplied carbon fiber reinforced polypropylene (CFRPP) between self-reinforced polypropylene (SRPP) layers. SRPP is produced by hot compaction of a woven fabric of highly oriented polypropylene and has an intrinsic behavior of shrinkage under high temperatures. The aim of this research is to enhance the tensile properties of the CFRPP/SRPP hybrid composites by using the SRPP shrinkage to introduce a compressive pre-strain in CFRPP. The results from tensile testing show that the failure strain of the hybrid composites is improved in comparison with CFRPP. The modulus and strength are noted to be lower than the ones expected from the rule of mixture. This may be attributed to the introduction of local misalignment (waviness) of carbon fibers caused by the SRPP shrinkage during consolidation.     

Extrusion and mechanical properties of highly filled cellulose fibre–polypropylene composites

This study focused on manufacturing of highly filled cellulose fibre–polypropylene composites and evaluation of the mechanical properties of the composites. Cellulose fibre reinforced polypropylene composites with up to 60 wt% of fibres with and without coupling agent were manufactured by extrusion. In order to achieve consistent feeding of the fibres into the extruder a pelletization technique was used where the fibres were pressed into pellets. Two commercial grades of cellulose fibres were used in the study, bleached sulfite and bleached kraft fibres. Fibre dimension measurements showed that the pelletization process and extrusion at high fibre loading caused the most severe fibre breakage. Flexural testing showed that increased fibre loading made the composites stiffer but reduced the toughness. Addition of maleic anhydride grafted coupling agent (MAPP) increased the stiffness and strength of the composites significantly. In general, there was no significant difference in the mechanical properties between the composites with kraft and sulfite fibres. An interesting finding was that the flexural modulus and strength of the MAPP modified cellulose fibre–polypropylene composites were not higher than what has previously been reported for wood flour–polyolefin composites. Scanning electron microscopy showed that addition of coupling agent improved the interfacial adhesion between the fibres and polypropylene matrix.     

Fabrication of the new structure high toughness PP/HA-PP sandwich nano-composites by rolling process

In this study a designed rolling setup was used to fabricate new structure polypropylene/hydroxyapatite-polypropylene (PP/HA-PP) sandwich nano-composites. To check the effect of rolling process and PP layers content on the structure and mechanical properties of these sandwich composites, different mechanical tests and analysis were performed on these composites. Results of tensile, bending and buckling tests show the rolling process improves the strength, modulus and flexural rigidity of composites significantly while with increasing the PP layers content from 10 vol.% to 20 vol.% decreases the stiffness, flexural rigidity and modulus of composites slightly. Results of impact test demonstrate the rolling process and increasing the volume percentage of the PP layers in sandwich composites cause a dramatic improve in impact absorbed energy of the PP/HA-PP sandwich composites. The results of Differential Scanning Calorimetry (DSC) analysis confirm the rolling process increases the crystallinity and molecular alignment of polypropylene in composites. The results of mechanical tests and DSC analysis show the increasing of polypropylene molecular alignment by rolling process is the most dominant reason of improvement the mechanical properties of sandwich composites.     

Mechanical and thermal properties of filamentary-reinforced structural composites at cryogenic temperatures 1: Glass-reinforced composites

This article is an extensive review of the literature on the mechanical and thermal properties of glass-reinforced structural composites at cryogenic temperatures. The objective is to provide an understanding of the general magnitude of property values obtainable within the cryogenic temperature range, to provide a feel for the relative literature ranking of specific composite types with regard to a specific property, and to impart an understanding of the temperature sensitivity of the property of interest. A bibliography and bibliography-property cross-reference is included. This is Part I of a two-part series. Part II will consider advanced composites.     

聚对苯二甲酸乙二醇酯/锡氟磷酸盐玻璃复合材料原位成纤对聚丙烯的增强效果

采用低玻璃化转变温度的锡氟磷酸盐玻璃(Pglass)改性聚对苯二甲酸乙二醇酯(PET),制备低黏度高模量的PET基复合材料(PET/Pglass);以PET/Pglass或PET为成纤相,聚丙烯为基体,利用实验室自主设计的多级拉伸挤出装置,制得原位成纤增强聚丙烯复合材料,并研究成纤相形态及其对复合材料力学性能的影响。结果表明,与PET相比,PET/Pglass在多级拉伸挤出过程中原位成纤更容易,纤维长径比更大,分散更均匀,从而进一步提高聚丙烯的拉伸强度和模量,而且能保持聚丙烯较高的断裂伸长率,表明具有低黏高模的PET/Pglass对聚丙烯的原位成纤增强效果更显著。     

不同改性剂对PP/木粉复合材料性能的影响

研究了苯甲酸(BA)、硬脂酸(SA)、甲苯-2,4-二异氰酸酯(TDI)对聚丙烯/木粉复合材料的改性效果。结果表明,木粉经改性剂处理后,表面极性减弱,与聚丙烯的界面张力降低,相容性提高;所有改性剂均可提高复合材料的拉伸强度、冲击强度以及熔体流动性能,但对弯曲强度影响不大。用TDI/SA复合处理木粉,复合材料的综合性能最好。扫描电镜(SEM)分析表明,木粉经过处理后,木粉与聚丙烯间界面较模糊。