NaBF4 as a hygrothermal durability enhancer for glass fibre reinforced polypropylene composites

The long term performance of composite materials is highly desired for their expanding application range. Tuning the interphase properties has been proven to be a practical way to enhance the performance of composites. In this study, short glass fibre (GF) reinforced polypropylenes (PPs) with improved hygrothermal durability were obtained by incorporating NaBF₄ into the sizing and thus the interphases of GF/PP composites. Detailed investigations were performed on the surface properties of sized GFs and the mechanical properties of virgin and aged composites. It was found that the retention in both ultimate tensile strength and Charpy impact toughness of aged composites monotonically increased with increasing NaBF₄ content. The improvement in hygrothermal durability was related to the enhanced fibre/matrix adhesion strength induced by the presence of NaBF₄ as indentified by fracture surface analysis using field-emission scanning electron microscopy and single fibre pull-out test.     

GF/PP towpregs production, testing and processing

A recently developed coating-line (Nunes et al., Thermoplastic Composite Materials 17(6), 523, 2003) was used to fabricate low-cost glass fibre reinforced polypropylene (GF/PP) towpregs, which were subsequently processed into composites by compression moulding and filament winding. The mechanical properties determined on the final composites are compared with the theoretical predictions. Filament wound prototypes of domestic gas pressure vessels were also produced from the GF/PP towpregs and submitted to internal pressure burst tests. These prototypes have shown accomplishing easily all requirements of the applicable European standards. The excellent obtained results clearly demonstrated that the thermoplastic matrix towpregs have potential to enlarge significantly future applications of composites in large consumption end-use markets.     

连续纤维增强PPESK树脂基复合材料的界面性能

用SEM观察了复合材料的微观断面结构,用横向拉伸强度和层间剪切强度表征玻璃纤维(GF)、T700碳纤维(CF)、芳纶纤维(F-12)增强PPESK树脂基复合材料的界面性能,研究了界面性能对三种复合材料耐湿热性能的影响.结果表明,T700/PPESK和F-12/PPESK复合材料的界面粘接性能均优于GF/PPESK复合体系.三种纤维复合材料的破坏机理不同:玻璃纤维发生纤维与树脂的界面脱粘破坏,碳纤维复合材料在破坏时,树脂与纤维并没有完全脱粘,破坏发生在树脂内;而芳纶纤维复合材料的破坏总伴随着纤维本身横向的撕裂破坏.三种复合材料体系均具有较低的吸湿率和良好的耐湿热性能,T700/PPESK复合材料在湿热条件下的性能保持率最高.     

Fabrication and mechanical properties of glass fibre–carbon fibre polypropylene functionally gradient materials

Hybrid fibre mat reinforced polypropylene (PP) composites with carbon(CF) and glass fibre (GF) were prepared and four kinds of functionally gradient materials (FGM) were fabricated by changing the spatial distribution of GF and CF. To measure the mechanical properties of FGMs and hybrid composites, flexural tests and instrumented impact tests were performed. The flexural strengths and the flexural moduli of hybrid composites increased following the rule of mixture as the relative volume content of CF increased. On the other hand, the total impact absorption energy of hybrid composites decreased with the increment of CF relative volume content. Compared with GF–CF PP isotropic hybrid composite, the composites with compositional gradient showed similar flexural strengths, but characteristic flexural moduli. Especially, sandwich-type FGMs with a CF-rich outer layer and a GF-rich inner layer exhibited higherflexural moduli than others. Total impact absorption energies of four FGMs were also similar, but the ratios of crack initiation energy,Ei, to crack propagation energy, Ep, or ductility index, were quite different.     

纤维表面处理与基体改性对连续玻纤增强聚丙烯力学性能的影响

考察了连续玻纤的表面处理、基体的接枝改性及接枝单体的种类和接枝产物的加入量对连续玻纤毡增强聚丙烯(CGFRPP) 力学性能的影响, 并通过红外光谱、扫描电镜对CGFRPP 的界面化学作用及界面粘结进行了研究。结果表明, 马来酸酐接枝改性聚丙烯与未经偶联剂处理的玻纤不能形成有效的化学结合, 而与经硅烷偶联剂表面处理的玻纤可发生明显的化学作用, 形成良好粘结, 显著提高CGFRPP 的力学性能; 硅烷偶联剂的种类对以改性PP 为基体的CGFRPP 力学性能的影响不大; 马来酸酐接枝聚丙烯比丙烯酸接枝聚丙烯对CGFRPP 力学性能的改善更为有效。      

Impact properties of glass fibre/impact modifier/polypropylene hybrid composites

The impact properties of glass-fibre/impact-modifier/polypropylene (GF/IM/PP) hybrid composites were characterized using a number of impact test methods. For the IM/PP blends, the impact fracture toughness can be measured using linear elastic fracture mechanics (LEFM) approach. For the GF/IM/PP hybrids, due to their non-compliance with LEFM, the essential work of fracture approach was employed. The impact properties of the IM/PP blends increased with IM concentration, while that of the GF/IM/PP hybrids did not change very much with IM content. It was concluded that cavitation of the PP matrix around the IM particles was the major toughening mechanism in the IM/PP blends. However, in the GF/IM/PP hybrids, the toughening effect due to cavitation was suppressed due to the introduction of short glass fibres (15 vol%). It is believed that the local stress in the matrix was relieved by fibre/matrix debonding of the relatively weak fibre/matrix interface. Thus, the presence of the IM particles was rendered insignificant in the GF/IM/PP hybrids.     

GF对SPTW/PP电商包装复合材料力学性能的影响

目的研究玻璃纤维(GF)对聚丙烯(PP)/六钛酸钾晶须(SPTW)复合材料力学性能的影响。方法首先选用硅烷偶联剂KH550对六钛酸钾晶须进行改性,采用聚丙烯接枝马来酸酐(PP-g-MAH)作为相容剂,通过在PP/SPTW复合材料中引入不同质量分数的玻璃纤维(GF),利用熔融共混法制得一系列PP/SPTW/GF复合材料。采用SEM观察冲击断面结构和XRD观察复合材料晶型结构,并比较引入不同质量分数的GF后PP/SPTW复合材料力学性能的变化。结果当复合材料中GF质量分数为5%时,复合材料的弯曲强度、拉伸强度和冲击强度达到最佳,分别提升了18.38%,16.31%,20.24%;当复合材料中GF质量分数大于5%时,复材料的力学性能开始下降。结论在复合材料中引入GF后,能够明显改善复合材料的力学性能,且随着GF质量分数的逐渐增加,复合材料的力学性能整体呈现出先上升后下降的趋势。     

Mechanical behaviour of textile-reinforced thermoplastics with integrated sensor network components

The embedding of sensor networks into textile-reinforced thermoplastics enables the design of function-integrative lightweight components suitable for high volume production. In order to investigate the mechanical behaviour of such functionalised composites, two types of bus systems are selected as exemplary components of sensor networks. These elements are embedded into glass fibre–reinforced polypropylene (GF/PP) during the layup process of unconsolidated weft-knitted GF/PP-preforms. Two fibre orientations are considered and orthotropic composite plates are manufactured by hot pressing technology. Micrograph investigations and computer tomography analyses show different interface qualities between the thermoplastic composite and the two types of bus systems. Mechanical tests under tensile and flexural loading indicate a significant influence of the embedded bus system elements on the structural stiffness and strength.     

Study on interfacial adhesion strength of single glass fibre/polypropylene model composites by altering the nature of the surface of sized glass fibres

Polypropylene (PP) compatibly sized glass fibres (GFs) were treated with boiling water and toluene, respectively, to reveal the interactions of water and toluene with different components in the sizing of sized GF and their influences on the interfacial adhesion strength of GF/PP model composites. Compared to control GF/PP model composites, about 30% increase of interfacial adhesion strength was achieved for composites with water-treated GF, whereas a small decrease of interfacial adhesion strength was revealed for composites with toluene-treated GF. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Zeta-potential measurement, and water contact angle measurement demonstrated that the boiling water-treated GFs posses a more polar and hydrophilic surface with homogeneously distributed derivatives of 3-aminopropyltriethoxysilane, which is related to a higher interfacial adhesion strength for water-treated GF/PP model composites. In contrast, hot toluene-treated GFs led to a more hydrophobic surface with low molar mass PP and surfactants enriching on the outermost surface.     

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.     

Early prediction of the failure of textile-reinforced thermoplastic composites using hybrid yarns

In this study, the manufacturing of core-sheath hybrid yarns consisting of steel fibres and glass filament yarn (GFY) using a friction spinning technique and their usability for failure prediction in composites is reported. With the DREF-2000 friction spinning technique, it is possible to manufacture hybrid yarns having a core-sheath structure. Steel fibres are used as the sheath and the GFY is used as the core of the yarns. These hybrid yarns are embedded between two layers of glass/polypropylene (GF/PP)-based knitted fabric composites. By varying the steel fibre content, it is possible to adjust the initial resistance as well as the sensitivity of the hybrid yarns to measure the interphase strain in the thermoplastic-based knit composite during tensile loading. The hybrid yarns with lower steel fibre content are found to be more sensitive in the prediction of the early damage in the composite. By performing a quasi-static and gradual increase of loading during the tensile tests, it is possible to identify the critical load for the composite. The before mentioned hybrid yarns show their suitability for the structural health monitoring and the potential to be integrated into thermoplastic-based composites by textile processing.     

A novel processing technique for thermoplastic manufacturing of unidirectional composites reinforced with jute yarns

This paper primarily investigates the fabrication process of long-fibre reinforced unidirectional thermoplastic composites made using jute yarns (both untreated and treated). Tubular braiding technique was used to produce an intermediate material called “microbraid yarn” (MBY) with jute yarn as the straightly inserted axial reinforcement fibre and polymer matrix fibre being braided around the reinforcing jute yarns. Microbraid yarns were then wound in a parallel configuration onto a metallic frame and compression molded to fabricate unidirectional composite specimens. In this study, two types of polymeric materials (biodegradable poly(lactic) acid and non-biodegradable homo-polypropylene) were used as matrix fibres. Basic static mechanical properties were evaluated from tensile and 3 point bending tests. Test results were analyzed to investigate the effects of molding temperature and pressure on the mechanical and interfacial behaviour. For the unidirectional jute fibre/poly(lactic) acid (PLA) composites, the results indicated that the molding condition at 175 °C and 2.7 MPa pressure was more suitable to obtain optimized properties. Improved wettability due to proper matrix fusion facilitated thorough impregnation, which contributed positively to the fibre/matrix interfacial interactions leading to effective stress transfer from matrix to fibre and improved reinforcing effects of jute yarns. For the jute/PP unidirectional composites, specimens with only 20% of jute fibre content have shown remarkable improvement in tensile and bending properties when compared to those of the virgin PP specimens. The improvements in the mechanical properties are broadly related to various factors, such as the wettability of resin melts into fibre bundles, interfacial adhesion, orientation and uniform distribution of matrix-fibres and the lack of fibre attrition and attenuation during tubular braiding process.     

MCA-MMT的制备及其对玻璃纤维增强聚丙烯复合材料阻燃性能的影响

为了提高玻璃纤维(GF)增强聚丙烯(PP)复合材料(GF/PP)的阻燃性能,通过在蒙脱土(MMT)悬浮液中进行三聚氰胺氰尿酸盐(MCA)分子自组装制备了新型协效成炭剂MCA-MMT,并采用FTIR、XRD、SEM和TGA对MCA-MMT的结构及热性能进行了表征;将MCA-MMT、无卤膨胀型阻燃剂与GF/PP熔融共混制备了阻燃复合材料MCA-MMT/(GF/PP),通过极限氧指数(LOI)测试、垂直燃烧试验和锥形量热测试研究了MCAMMT对GF/PP的阻燃效果和阻燃机制,并测试了复合材料的力学性能。结果表明:MMT的加入会影响氰尿酸和三聚氰胺在MCA合成过程中的氢键作用,干扰和抑制大平面氢键网络的形成,减少MCA氢键复合体的分子体积,使颗粒变小。MCA-MMT/(GF/PP)的UL-94防火等级达到V-0级,LOI为31.3%。MCA-MMT的阻燃效率高于传统MCA的,可降低材料燃烧的热释放程度和总烟释放量,使复合材料的阻燃性能提高,其阻燃机制为片层结构的MMT可提高MCA的成炭量,使MCA-MMT/(GF/PP)燃烧后能形成致密的残留炭层。MCA-MMT/(GF/PP)的拉伸、冲击强度与MCA/(GF/PP)的相比并未下降。     

Penetration impact resistance of hybrid composites based on commingled yarn fabrics

The penetration impact resistance of hybrid composites based on commingled yarn fabrics was investigated. The commingled yarn fabrics were composed of E-glass fibres (GF) and thermoplastic fibres blended together within the fibre bundles. Various thermoplastic fibres such as polypropylene (PP), polyamide (PA) and modified polyethylene terephthalate (mPET) were studied. Various resin matrices with different cure cycles were studied such as Quickcure polyester, Cycom X823 RTM epoxy, and Shell Epikote 828 epoxy resin. Depending on the crystalline melting temperature (T_m) of the thermoplastic fibres, the hybrid composites can be categorised as fibre-hybrid composites or matrix-hybrid composites. Fibre-hybrid composites refer to those in which the thermoplastic fibres remain in the fibre form after curing, for example the GF–PP and GF–PA hybrid composites. For matrix-hybrid composites, the thermoplastic fibres melt and dissolve into the thermosetting matrix during curing such as the GF-mPET hybrid composites. The results from the penetration impact showed that the total absorbed energy of the fibre-hybrid composites were significantly higher than for the plain glass composites. Plastic deformation in the thermoplastic fibres is the key factor that improves the absorbed energy of the hybrid composites. When the thermoplastic fibres dissolved into the thermosetting matrix as in matrix-hybrid composites, the total absorbed energy was similar to that of the plain glass fibre composites. This suggests that the total absorbed energy is dependent on the properties of the fibres rather than the matrix. However, the fibre-hybrid composites showed slight differences in the total absorbed energy for different matrices. The differences are thought to be related to the differences in the bonding between the thermoplastic fibres and the thermosetting matrix which have yet to be investigated.     

Mechanical properties of flax fibre/polypropylene composites. Influence of fibre/matrix modification and glass fibre hybridization

The effect of fibre treatments and matrix modification on mechanical properties of flax fibre bundle/polypropylene composites was investigated. Treatments using chemicals such as maleic anhydride, vinyltrimethoxy silane, maleic anhydride-polypropylene copolymer and also fibre alkalization were carried out in order to modify the interfacial bonding between fibre bundles and polymeric matrix. Composites were produced by employing two compounding ways: internal mixing and extrusion. Mechanical behaviour of both flax fibre bundle and hybrid glass/flax fibre bundle composites was studied. Fracture surfaces were investigated by scanning electron microscopy. Results suggest that matrix modification led to better mechanical performance than fibre surface modification. A relevant fact is that silanes or MA grafted onto PP matrix lead to mechanical properties of composites even better than those for MAPP modification, and close to those for glass fibre/PP.     

Processing, compatibilization and properties of ternary composites of Mater-Bi with polyolefins and hemp fibres

Ternary composites of a biodegradable thermoplastic matrix, Mater-Bi® (MB), with various polyolefins (PP, HDPE and PS) and hemp fibres (H) were obtained by melt mixing and characterized by SEM, OM, DSC, TGA and tensile tests. The properties of composites were compared with those of MB/polyolefin and MB/H blends. Maleic anhydride functionalized polyolefins were employed as compatibilizers. Crystallization behaviour and morphology of the composites were found to be affected by the composition, phase dispersion and compatibilizer. Thermogravimetric analysis indicated that the thermal stability of the polyolefin phase and fibres was influenced by the composition and phase structure. A significant improvement of tensile modulus and strength was recorded for composites of MB with PE and PS as compared to MB/H composites. The results indicate that incorporation of polyolefins in the biodegradable matrix, compared to binary matrix/fibre system, may have significant advantages in terms of properties, processability and cost.     

连续玻璃纤维/聚丙烯热塑性复合材料拉挤成型中的工艺参数

采用复合纱拉挤方法制备连续玻璃纤维/聚丙烯(GF/PP)热塑性复合材料,研究了复合纱拉挤成型过程中模具温度及拉挤速度对GF/PP复合材料截面中心温度的影响。以傅里叶定律为理论基础,分析了拉挤过程中模腔内的瞬态传热过程;建立了工艺参数矩阵,通过有限元数值计算,预测了不同模具温度、拉挤速度下GF/PP复合材料截面中心的温度变化,优选了工艺参数组合。通过实验制备不同温度、不同拉挤速度的GF/PP复合材料,并进行弯曲模量测试及截面形貌观察。结果表明:在GF/PP复合纱拉挤过程中,拉挤速度不宜超过350 mm/min,模具熔融区温度设定应高于180℃;GF/PP复合材料在150℃-230℃-50℃成型温度、100 mm/min拉挤速度的工艺参数设定下获得最优的制品力学性能;在设定拉挤参数时,拉挤速度相较于熔融区温度更重要。      

Thermoplastic filament winding with online-impregnation. Part B. Experimental study of processing parameters

In part A of this paper, a novel process technology was presented which allows to combine thermoplastic filament winding with online melt impregnation of fibre bundles. In this part, a comprehensive study of process parameters was conducted. Circular glass fibre (GF) reinforced polypropylene (PP) or polyamide 12 (PA12) tubes were produced as sample component. Processing speeds of up to 15 m/min could be achieved in case of GF/PP before a drop in quality of the parts had to be accepted. The present limitation in winding speed is not attributed to impregnation problems but to an excessive rise in force required to pull the fibre tow off the impregnation device. Measures for process improvement and increase in productivity were proposed.     

Jute/polypropylene composites I. Effect of matrix modification

Natural fibre-reinforced polymers can exhibit very different mechanical performances and environmental aging resistances depending on their interphase properties, but most studies have been focused on fibre surface treatment. Here, investigations of the effect of maleic anhydride grafted polypropylene (MAHgPP) coupling agents on the properties of jute fibre/polypropylene (PP) composites have been considered with two kinds of matrices (PP1 and PP2). Both mechanical behaviour of random short fibre composites and micro-mechanical properties of single fibre model composites were examined. Taking into account interfacial properties, a modified rule of mixture (ROM) theory is formulated which fits well to the experimental results. The addition of 2 wt% MAHgPP to polypropylene matrices can significantly improve the adhesion strength with jute fibres and in turn the mechanical properties of composites. We found that the intrinsic tensile properties of jute fibre are proportional to the fibre’s cross-sectional area, which is associated with its perfect circle shape, suggesting the jute fibre’s special statistical tensile properties. We also characterised the hydrophilic character of natural fibres and, moreover, humidity environmental aging effects. The theoretical results are found to coincide fairly well with the experimental data and the major reason of composite tensile strength increase in humidity aging conditions can be attributed to both improved polymer–matrix and interfacial adhesion strength.     

Short Fibre Reinforced PP/PANI-Complex Blends and their Mechanical and Electrical Properties

This study deals with the mechanical and electrical properties of polypropylene (PP)/ polyaniline (PANI)-complex blends and their short glass fibre (GF) composites. In particular, the surface resistivity, the electrical conductivity and its profile were characterized. Tensile modulus, tensile strength and impact resistance of the materials were also measured as a function of GF- and PANI-complex content. The miscibility and microstructure of the blends could be studied by using light optical and scanning electron microscopy. While a steady increase in tensile modulus with increasing GF content was observed in all material combinations, an improvement in the tensile strength could only be achieved in case of the glass fibre reinforced unmodified PP-matrix composites. The conductivity of the materials increased with increasing PANI-complex content. The low percolation threshold for conductivity could be explained by the formation of a PANI-complex network near the surface of the samples.