Transcrystallisation in PP/flax composites and its effect on interfacial and mechanical properties

The effect of flax fibre reinforcement on the crystallisation behaviour of polypropylene (PP) was investigated using a hot-stage polarising optical microscope. To follow the crystallisation kinetics, crystallisation temperature and time were varied. At crystallisation temperatures between 130 and 138 °C the most uniform and thickest transcrystalline layers were formed. The effect of transcrystallisation on the interfacial shear strength (IFSS) in micro-composites was studied by the fibre pull-out test method. It was found that the IFSS of the PP/flax system is slightly decreased with the presence of a transcrystalline interphase. Finally, the influence of the formation of a transcrystalline zone on the macromechanical properties of compression moulded PP/flax composites was studied.     

PP/POE/BaSO4三相复合体系的形态控制和力学性能的研究

用扫描电镜（SEM），动态力学分析（DMA）及力学性能表征等方法，研究了组分特性对PP／POE／BaSO4三相复合体系形态的影响以及形态与复合材料力学性能的关系，结果表明，弹性体（POE）经过马来酸酐接枝改性后，无机粒子与弹性体之间的相互作用加强，在熔融加工过程中填料粒子倾向于进入橡胶相，即形成橡胶包覆无机粒子的结构，而当POE未经接枝改性时，橡胶相与无机粒子倾向于形成相互分离的相结构，力学性质的研究表明，两种形态的三相复合体系的冲击强度和杨氏模量的比纯PP，PP／POE和PP／BaSO4两相复合体系有显著的提高，即同时实现了增强和增韧。     

PP/POE/BaSO4共混体系界面相互作用表征与拉伸断裂形态研究

设计了三种具有不同界面相互作用的PP/POE/BaSO4三元复合体系，SEM观察和DSC分析证明三元复合体系中形成了两种形态结构。即完全分离结构与核壳包覆结构。采用拉伸屈服强度定量表征了界面相互作用的强弱，研究了界面相互作用对三元复合体系拉伸断裂形态的影响。研究结果表明，体系的界面相互作用对其拉伸屈服强度和断裂伸长率有明显影响。     

Effect of composition on phase morphology and mechanical properties of PP/PA66 in situ composites via extrusion-drawing-injection method

The reinforced and toughened PP/PA66 in situ composites were prepared via extrusion-drawing-injection method. The relationship among composition, phase morphology and mechanical properties, together with their functional mechanism, was investigated. The results show that in the range of PA66 weight fraction (f _w) from 0 to 20% and under the experimental processing conditions, the main changes in phase morphology of the composites with f _w are that the number of in situ formed PA66 microfibers and remained PA66 particles increases with f _w whereas the fiber transverse size and its dispersity decrease till f _w = 15% and then increase. This can be attributed to the combined effect of break-up, coalescence and deformation of the PA66 phase in the PP phase in the course of extrusion and drawing. The tensile strength of composites has a maximum value at f _w of 15% and Young's modulus increases with f _w up to a plateau level, while impact strength continuously rises with f _w, an effect which can be ascribed to the distinct dependence of these properties on the phase-morphological factors mentioned above.     

Effect of interfacial features on the mechanical and electrical properties of rGO/Al composites

This study investigates the effect of interfacial features on the mechanical and electrical properties of reduced graphene oxide (rGO)/aluminum (Al) composites. The composites were fabricated using a hybrid process that includes chemical and mechanical methods. First, GO was uniformly dispersed on the surface of Al powder via a solution process. A strong interface was formed between GO and Al via several chemical bonds by using polyvinyl alcohol (PVA) as an organic binder during the solution process. Then, GO was thermally reduced to rGO, wherein the interfacial features were varied according to the atmosphere (vacuum or H₂(10%)/N₂(90%) mixed gas). Subsequently, rGO was mechanically embedded and further dispersed within soft Al powder through the plastic deformation of Al. Vacuum was found to be more effective than the mixed gas at removing functional groups containing oxygen in GO and therefore generated a tighter interface. As a result, the composites containing rGO that were reduced under vacuum showed higher strength and lower ductility compared with those reduced under the mixed gas. Conversely, the interfacial features rarely affected the electrical conductivity of the composites because the electrical conductivity of rGO was considerably lower than that of Al. Consequently, compared with their monolithic counterparts, the composites containing only 0.2 vol% rGO showed a 374-MPa yield strength without a significant loss of electrical conductivity, thereby demonstrating their potential feasibility in electrical and electronic applications.     

Effect of transcrystalline morphology on interfacial adhesion in cellulose/polypropylene composites

A study was conducted on the effect of cotton cellulose fibres on the crystallization behaviour of isotactic polypropylene (PP) from the melt and the resulting morphology. When the PP was allowed to crystallize isothermally at 131° C, the cotton fibres acted as nucleating agents and a transcrystalline phase was created around the fibres. Quench cooling of the melt prevented the occurrence of such a phase. Transcrystalline layers of different thicknesses were created by interrupting the isothermal crystallization at certain intervals and quenching the melt. The effect of these morphologies on interfacial shear stress transfer was investigated using the single-fibre fragmentation test. It was found that the transcrystalline morphology at the fibre/matrix interface improved the shear transfer considerably when a tensile load was applied in the fibre direction. One mechanism is proposed to be particularly responsible for this increase: slow cooling favours the kinetics of the approach of PP molecules, and hence interfacial adsorption, which yields an ordered transcrystalline PP interphase having a high density of intermolecular secondary bonds with the cellulose surface. An increase in the shear transfer efficiency with increasing thickness of the transcrystalline layer was also observed.     

Creep and dynamic mechanical behavior of PP–jute composites: Effect of the interfacial adhesion

The dynamic mechanical response and the short term creep-recovery behavior of composites made from bi-directional jute fabrics and polypropylene were studied. In order to improve the compatibility of the polar fibers and the non-polar matrix, two alternatives were compared: the addition of coupling agents and the chemical modification of the fibers. In the first case, two commercial maleated polypropylenes and lignin, a natural polymer, were used. In the second approach, the fibers were esterified using a commercial alkenyl succinic anhydride. The degree of interfacial adhesion was inferred from the measured properties and confirmed by the observation of the composite fractured surface. The maleated polypropylenes acted as compatibilizers since they were able to join the fibers to the neat PP, locating themselves in the interphase region. On the other hand, a clear separation between fibers and matrix could be observed when lignin was used as compatibilizing agent and when the chemically modified fibers were used to prepare the composite. The creep deformation could be directly related to the interfacial properties. Bürgers model parameters were calculated from the creep part of the curves, and the recovery part was modeled using these values. A very good agreement between experimental data and theoretical curves were obtained in the creep region, although small discrepancies were found in the recovery part. The feasibility of the construction of a master curve (using the time–temperature principle) to predict long term creep behavior of the composites was investigated.     

制备工艺对纳米有机蒙脱土／聚酰胺6-聚丙烯复合材料分散相形态及力学性能的影响

通过熔融挤出法制备了纳米有机蒙脱土OMMT／聚酰胺6（PA6）母粒M1和OMMT／聚丙烯（PP）母粒M2,将这两种母粒分别与PA6-PP熔融共混,制备了不同OMMT含量的纳米OMMT／PA6-PP复合材料,同时采用直接共混法制备了相同配比的该纳米复合材料。利用TEM和SEM表征了OMMT在复合材料中的分散、分布和复合材...     

PET-MFIAA/ PP原位成纤复合材料的形态结构及力学性能

用钉挂预埋多功能界面活化剂(MFIAA)的PET(PET-MFIAA)与PP共混 - 挤出 - 拉伸,制备了PET-MFIAA/PP原位成纤复合材料,采用扫描电镜、偏光显微镜观察和力学性能测定的方法,研究了PET-MFIAA/PP的PET微纤形态、试样断面形态及力学性能,并与PET/PP、MFIAA/PET/PP两种原位成纤复合材料进行对比。结果表明: PET-MFIAA/PP PET微纤与PP基体间具有强的相互作用,PET微纤呈粗细不均匀、凹凸不平的异形形态及柔性界面等结构特征,形成了强的界面结合,其刚性、韧性均比纯 PP明显提高,含7.00% MFIAA的PET-MFIAA/PP复合材料的拉伸屈服应力、弯曲弹性模量和悬臂梁缺口冲击强度分别达到了纯PP的1.04倍、1.23倍和1.79倍。     

含硫偶联剂对木粉/橡胶-塑料三元复合材料力学性能及耐热性能的影响

以再生高密度聚乙烯（HDPE）、沙柳木粉和废轮胎胶粉为原材料,含硫偶联剂Si69为界面相容剂,采用模压法制备木粉/橡胶-塑料三元复合材料。考察Si69对木粉/橡胶-塑料三元复合材料力学性能及耐热性能的影响,并采用FTIR和SEM分析Si69改性前后废轮胎胶粉的表面特性及木粉/橡胶-塑料三元复合材料的微观断面形貌。结果表明:Si69与废轮胎胶粉发生了化学反应。当Si69添加量为5wt%时,木粉/橡胶-塑料三元复合材料的界面结合较佳,力学性能及耐热性能较优,其中弯曲强度、弯曲模量、拉伸强度较未添加Si69的木粉/橡胶-塑料三元复合材料分别提高了13.85%、7.24%和6.63%;维卡软化温度和热变形温度较未添加Si69的木粉/橡胶-塑料三元复合材料分别提高了6.95℃和8.70℃,Si69可在一定程度上提高木粉/橡胶-塑料三元材料的耐热性能。Si69添加量为7wt%时,木粉/橡胶-塑料三元复合材料的缺口冲击强度可达到3.99 k·Jm-2。      

Effect of blend composition on the morphology and mechanical properties of microfibrillar composites

Various blend compositions of polyethyleneterphthalate (PET) and polyamide 6 (PA 6) were used to prepare microfibrillar composites (MFC's) in form of thin ribbons. Steps for preparation were: (1) blending, (2) extrusion, (3) fibrillation, and (4) isotropization. The latter step was performed at a temperature condition above the melting temperature of PA 6, but below that of PET. In this way PET microfibrils remained as reinforcing elements in the PA 6-matrix. Depending on the actual PET/PA 6 ratio, various fibril arrangements in terms of fibril length and uniformity of fibril distribution could be achieved. A reasonable improvement in mechanical properties was reached already at 30 wt. % PET in PA 6 which was in terms of tensile strength higher than a 30 wt. % short glass fiber filled PA 6 system.     

Effect of EVOH on the morphology,mechanical and barrier properties of PA6/POE-g-MAH/EVOH ternary blends

Polyamide 6 (PA6)/maleated poly(ethylene-1-octene) (POE-g-MAH) blends with various ethylene–vinyl alcohol (EVOH) concentrations were prepared via melt-blending. The morphology, mechanical and barrier properties of the blends were investigated in terms of scanning electron microscope (SEM), impact/tensile testing, dynamic mechanical analysis (DMA) and oil absorption rate. The SEM images indicated that the compatibility between PA6 and POE-g-MAH was improved significantly after the incorporation of EVOH. The toughness of blends was correlated with the morphology of the POE-g-MAH and EVOH dispersion phase. It has also demonstrated that the incorporation of EVOH increased evidently the tensile strength, storage modulus and barrier properties, which were contributed to the strong interactions formed through the reaction among PA 6, POE-g-MAH and EVOH.     

Effect of pimelic acid on the crystallization, morphology and mechanical properties of polypropylene/wollastonite composites

The pimelic acid (PA) was used as a new surface modifier for wollastonite. The effects of PA treatment on the crystallization, morphology and mechanical properties of polypropylene/wollastonite composites were investigated. The Fourier transform infrared spectroscopy analysis revealed that the PA bonded to the wollastonite's surface and formed the calcium pimelate after reacting with the wollastonite. The results of wide angle X-ray diffraction, differential scanning calorimetry and polarized light microscopy proved that the PA treated wollastonite induced more β-crystalline form and decreased the spherulites sizes of polypropylene. The results of scanning electron microscopy showed that the PA treatment enhanced the interfacial adhesion between the filler and the matrix, indicating the improvement of the compatibility between polypropylene and wollastonite. The toughness of the composites was improved by the more ductile β-form spherulites. When 2.5 wt% of PA treated wollastonite was added, the Izod notched impact strength reached its maximum, a value of 17.33 kJ/m², which was 3.19 times greater than that of the blank polypropylene.     

The effect of molecular weight on the interfacial properties of GF/PP injection molded composites

It is well established that the molecular weight of recycled PP decreases significantly as compared to the virgin material. Hence this study involved 2 PP grades of different molecular weights in order to simulate the recycling process. The effect of weight–average molecular weight on interfacial adhesion between GF and PP was investigated. Tensile test was done and the fiber length distribution around the fracture zone in both composites was compared with the distributions from similar locations of unstressed composites. The effect of PP-grafted maleic anhydride coupling agent was also studied. It was found that a decrease in weight–average molecular weight of PP improved interfacial adhesive strength between GF/PP. The lower molecular weight matrix has a lower viscosity that enables its molecules to penetrate easily into the silane interphase. In that case, the interfacial area that is available for coupling is higher, leading to a more effective coupling. The higher interfacial shear strength between the glass fiber and the lower molecular weight matrix induced more breakage of the glass fiber during tensile test.     

Novel manufacturing process for improving mechanical properties of flax/PP composites

Many attempts have been made in the recent past to improve the mechanical properties of flax/polypropylene (PP) thermoplastic composites. Most of these attempts have not been translated at industrial level due to additional chemical treatment process involved. In the present work, needle-punched nonwoven preforms which can be readily used for composite manufacturing was prepared. To improve the interfacial bonding of the composites, a new modified route for composite preparation is proposed. The modified processing strategy implemented to produce flax with polypropylene composite using compression molding machine. The nonwoven preforms were heated to elevated temperatures followed by quenching. The composite samples were then hot consolidated and their mechanical properties were studied and compared with the samples produced by the conventional method. 154, 75, 37, and 9.6% of improvement have been observed for peel strength, compressive strength, hardness, and impact strength, respectively. The reasons for the improvement are discussed in detail using various analytical tools.     

Effect of ternary solute interaction on interfacial segregation and grain boundary embrittlement

Effect of ternary solute interaction on interfacial segregation and grain boundary embrittlement in an M–I–J system is modeled on the basis of combined Guttmann and Rice–Wang approaches. It is clearly shown that repulsive I–J interaction strengthens interfacial segregation of the impurity I, suppresses segregation of the solute J, and substantially enhances intergranular embrittlement. Attractive interaction exhibits an opposite effect. Generally, the effect of the ternary interaction is weaker than that of the binary one. Although there are only rare experimental data in this respect, their comparison to model calculations shows a very good agreement.     

Kevlar缝线表面处理对炭纤维/双马来酰亚胺树脂缝合复合材料界面性能的影响

为了改善Kevlar缝线缝合复合材料的耐湿热性能, 采用化学接枝烯丙基的方法对Kevlar缝合线进行表面改性处理。通过力学测试、 扫描电子显微镜(SEM)、 光电子能谱分析(XPS)对表面改性的纤维进行表征。实验结果表明, 化学处理的Kevlar缝线表面变得粗糙, 缝线表面氧元素的含量提高23%, 在合适的处理条件下, 缝线的拉伸强度降低很小。同时通过测试干、 湿态下炭纤维/双马来酰亚胺树脂缝合复合材料层压板的层间剪切强度, 研究了化学表面处理的Kevlar缝线对缝合炭纤维/双马来酰亚胺树脂复合材料界面性能的影响。测试结果显示, 表面处理后Kevlar缝线缝合的复合材料的吸湿率降低约52%, 湿态层间剪切强度保持率提高15%。      

Effect of CuO nanostructure morphology on the mechanical properties of CuO/woven carbon fiber/vinyl ester composites

The effect of CuO nanostructure morphology on the mechanical properties of CuO/woven carbon fiber (WCF)/vinyl ester composites was investigated. The growth of CuO nanostructures embedded in the surface of woven carbon fibers (WCFs) was carried out by a two-step seed-mediated hydrothermal method; i.e., seeding and growth treatments with controlled chemical precursors. CuO nanostructural morphologies ranging from petal-like to cuboid-like nanorods (NRs) were obtained by controlling the thermal growth temperature in the hydrothermal process over a growth time of 12 h. The Cu²⁺/O⁻ ratio and the rate of reaction greatly influenced the formation of CuO nanostructures as self-assembled shapes on the crystal planes in the order L[0 1 0] > L[1 0 0] > L[0 0 1]. Morphological variations were analyzed by scanning electron microscopy, X-ray diffraction, and Brunauer–Emmett–Teller surface area analysis. The impact behavior, in-plane shear strength, and tensile properties of the CuO/WCF/vinyl ester composites were analyzed for different CuO NR morphologies at various growth temperatures and molar concentrations. The CuO/WCF/vinyl ester composites had improved impact energy absorption and mechanical properties because the higher specific surface area of CuO NRs grown as secondary reinforced nanomaterials on WCFs enhanced load transfer and load-bearing capacity.     

Effects of silsesquioxane coating structure on mechanical interfacial properties of carbon fibre/polyarylacetylene composites

Carbon fibres (CF) were treated with different coatings, including [3-(methacryloxy)propyl]trimethoxylsilane (MPMS), [3-(methacryloxy)propyl]silsesquioxane (MPMS-SSO), and (methacryloxy)propyl polyhedral oligomeric silsesquioxane (Methacryl-POSS), to improve the interfacial properties of carbon fibre reinforced polyarylacetylene (PAA) matrix composites. MPMS-SSO was obtained from the hydrolytic condensation of MPMS. The complicated structure, including cage and ladder one, of MPMS-SSO may be assigned by Fourier transforms infrared (FT-IR) spectra, ¹H, ¹³C and ²⁹Si nuclear magnetic resonance (NMR) and ultraviolet matrix-assisted laser desorption ionization time-of-flight mass spectrometry (UV-MALDI-TOF MS). Interlaminar shear strength (ILSS) was tested to investigate the effect of coating structure on the interfacial bonding. The values of ILSS of untreated and treated CF/PAA composites with different coatings (MPMS, MPMS-SSO and Methacryl-POSS) show that the treatment effect of Methacryl-POSS coating is the best one and the MPMS-SSO coating is better than that of MPMS coating. SEM micrographs of shear fracture of CF/PAA composites also suggested the different coating treatment effects. The differences of increasing degrees of ILSS indicate that the structure of coating is important when silsesquioxanes are used as coatings to treat fibre surface for building up the adhesion and improving interfacial properties of fibre reinforced polymer matrix composites.