Conductive polyolefin–rubber nanocomposites with carbon nanotubes

Polyolefin–rubber composites of differing compositions were formed by melt mixing linear low density polyethylene (LLDPE) and functionalised rubber particles (FRP) through interactions of pre-functionalised polymers in the interface. Following the incorporation of carbon nanotubes to the polymeric composites the nanocomposites filaments were extruded for fused deposition modelling (3D printing). The mechanical properties of the composites (tensile and flexural modulus, yield stress, tensile strength, elongation at break) were compared with respect to how the test specimens were made: compression moulding versus 3D printing. The results showed that increasing the rubber content concentrated the nanotubes in the LLDPE phase forming electrically conductive pathways. The use of maleic anhydride as a compatibilizer improved the mechanical properties of the composites overall. The 3D printed specimens had lower mechanical properties than the compression moulded specimens, though they had the same electrical conductivity.     

Preparation and characterization of poly(methyl methacrylate)-clay nanocomposites via melt intercalation: Effect of organoclay on thermal, mechanical and flammability properties

The PMMA nanocomposites were prepared by melt processing method. The influence of organoclay loading on extent of intercalation, thermal, mechanical and flammability properties of poly(methyl methacrylate) (PMMA)-clay nanocomposites were studied. Three different organoclay modifiers with varying hydrophobicity (single tallow vs. ditallow) were investigated. The nanocomposites were characterized by using wide angle X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), and tensile tests. The intercalation of polymer chain within the silicate galleries was confirmed by WAXD and TEM. Mechanical properties such as tensile modulus (E), tensile strength, percentage elongation at break and impact strength were determined for nanocomposites at various clay loadings. Overall thermal stability of nanocomposites increased by 16-17 °C. The enhancement in T_g of nanocomposite is merely by 2-4 °C. The incorporation of maleic anhydride as compatibilizer further enhanced all the properties indicating improved interface between PMMA and clay. The flammability characteristics were studied by determining the rate of burning and LOI.     

The effects of a silane coupling agent on properties of rice husk-filled maleic acid anhydride compatibilized natural rubber/low-density polyethylene blend

Blends of natural rubber and low-density polyethylene were prepared in different weight compositions in presence of dicumyl peroxide and maleic acid anhydride. The effects of rice husk (RH) content and a silane coupling agent, that is, 3-aminopropyl triethoxy silane (3-APE, 1 wt% of filler content) on the physicomechanical properties and mass swell of the tested blend were investigated. The incorporation of untreated RH into the blend improved Young’s modulus, hardness but decreased tensile strength, elongation at break, impact strength, and mass swell. Incorporation of 3-APE has produced composite with improved tensile strength, Young’s modulus, hardness and impact strength with a sharp decrease in elongation, and better mass swell in comparison with untreated one. The effect of γ-irradiation doses on retained physicomechanical properties of RH (30 phr) filled blend samples before and after silane treatment was investigated at ambient temperature. The efficiency of silanized RH (30 phr) was also evaluated by the studies of the surface morphology (scanning electron microscopy) and thermal properties (thermal gravimetric analysis and thermal mechanical analysis).     

Structure–fracture properties relationship for Polypropylene reinforced with fly ash with and without maleic anhydride functionalized isotactic Polypropylene as coupling agent

The deformation and fracture behavior of PP/ash composites with and without maleic anhydride functionalized iPP (MAPP) as coupling agent was investigated, focusing on the effect of ash content and loading conditions. A decreasing trend of tensile strength and strain at break values with filler content was observed for unmodified composites, whereas these properties were roughly independent of ash content for the composites with MAPP. In quasi-static fracture tests, all materials displayed ductile behavior. Most composites exhibited improved fracture properties with respect to the matrix as a result of the toughening mechanisms induced by the ash particles. Under impact loading conditions, in contrast, all materials displayed fully brittle behavior. Impact critical fracture energy values of the composites were higher than those of PP and they also presented a maximum which was explained in terms of the comprehensive analysis of the crystallinity development in PP. The incorporation of MAPP led to better dispersion of ash particles in the matrix but was detrimental to the material fracture behavior independently of loading conditions. Increased interfacial adhesion promoted by MAPP hindered particle-induced toughening mechanisms.     

Influence of mesoporous silica and hydroxyapatite nanoparticles on the mechanical and morphological properties of polypropylene

This paper presents the effect of different types of additives on the morphology and mechanical performance of polypropylene (PP). Three different types of nanoparticles, containing mesoporous silica (MCM-41), Hydroxyapatite (HA) and the composite of MCM-41 and HA (MH) were used. Nanocomposites containing PP, 3 wt.% of maleic anhydride grafted polypropylene (PP-g-MA) and 3 wt.% of different nanoparticles were prepared using the melt-compounding technique in a twin-screw extruder. The bulk mechanical response of the nanocomposites such as tensile, flexural and Izod impact properties were studied. The results of mechanical tests show that at the same nanomaterial content, all the nanofillers cause better tensile, flexural and impact strength than neat PP. The MH nanoparticle improves the mechanical properties of PP, better than the other nanoparticles because this nanofiller contains good properties of both MCM-41 and HA nanoparticles in itself. In order to investigate the effect of foam agent on the mechanical properties of neat PP and nanocomposites based on PP, inorganic azodicarboxamide was added to the aforementioned mixtures as chemical blowing agent and the foamed specimens were resulted using the melt-compounding technique. The results reveal that addition of foam agent to mixtures, leads to increase the flexural characteristics of samples, but the tensile properties and impact strength decrease. Scanning electron microscopy (SEM) was used to assess the fracture surface morphology and the dispersion of the nanoparticles. X ray diffractometry (XRD) was used to examine the intercalation effect on the nanocomposites. The observations show that the nanomaterials were well dispersed in the polymer matrix and the enhancement of the interface between the matrix and fillers was obtained by the incorporation of MH, MCM-41 and HA nanoparticles into PP matrix.     

聚乙二醇改性物对高交联度不饱和聚酯的增韧改性

合成了一种含有反应活性端基的聚乙二醇,并用之对高交联度不饱和聚酯进行增韧。结果表明,含有反应性马来酸酐端基的聚乙二醇参与了不饱和聚酯的固化反应,可在交联网络中构成不同长度的柔性链段,从而显著地提高了不饱和聚酯的韧性。将其应用于BMC材料的增韧也获得了满意的增韧效果。     

草鱼鳞片的多级结构及力学性能

经过长时间的自然进化,硬骨鱼鳞片变得超薄、超轻,并具有很好的柔韧性。为研制新型柔性防护体系,对草鱼鳞片的多级结构及力学性能进行了研究。首先,按3个不同方向(0°、45°和90°)在鳞片中心区域裁取鳞片和胶原层2组试样;然后,进行了轴向拉伸测试并对不同含水量的鳞片以及不同应变率下鳞片和胶原层的力学性能进行了对比研究。结果显示:草鱼鳞片主要由坚硬的骨质外层和软质的胶原层组成,其中胶原层由胶原纤维层交错叠加组成,交错角约为28°~31°;鳞片的力学性能为平面内各向异性,而胶原层的力学性能为各向同性;脱水鳞片的弹性模量和拉伸强度显著增加,分别约为饱水鳞片的10倍和3倍,但极限应变减少了约50%。饱水鳞片和胶原层的力学性能与应变率有很大相关性。所得结论为新型仿生复合材料及柔性防护体系的研究提供了思路。      

超韧尼龙11合金的力学性能和相态研究

研究了尼龙11和POE的共混物，制备了不同的马来酸酐接枝率的尼龙11／POE－g－MAH和尼龙11／POE／POE－g-MAH共混物，研究了共混物的力学性能和相态。结果表明，引入POE－g-MAH能够提高相容性和共混物的韧性，并且马来酸酐接枝率越高效果越为明显，与此同时，拉伸强度却降低得很少。     

Mechanical properties of injection-moulded styrene maleic anhydride (SMA): Part I: Influence of weldline and reprocessing

This paper presents the results from the first part of a study on the influence of reprocessing and weldlines on the properties of styrene maleic anhydride (SMA) polymer. Specimens for this study were injection moulded and reprocessed up to five times. It was found that while mechanical properties such as strength and modulus in both tension and flexure tests were virtually independent of the number of reprocessing cycles, the energy to fracture decreased as a result of reprocessing. Fracture parameters such as fracture toughness and strain energy release rate also showed little variation with reprocessing; although at times a reduction in these parameters was obtained for the fifth cycle. We found that tensile strength, fracture energy and fracture toughness were all reduced substantially in the presence of the weldline. However, none of these properties showed any significant variation with the number of reprocessing cycles. © 1998 Chapman & Hall     

Mechanical properties of basalt fibers and their adhesion to polypropylene matrices

This work is aimed to study the mechanical properties of basalt fibers, and their adhesion to polypropylene (PP) matrices. Single filament tensile tests were used to calculate the strength of different types of fibers, characterized by different providers and surface treatment. Single fiber fragmentation tests (SFFT) were used to calculate the critical length of the fibers, in a homopolymer PP matrix and in a maleic anhydride modified PP matrix. It was shown that the tensile strength of the fibers is not significantly influenced by the origin or the surface treatment. Only fibers without any sizing show very reduced mechanical properties. On the other hand, the tensile strength was shown to be severely dependent on the filament length. Weibull theory was used in order to calculate the fitting parameters σ₀ and β, which were necessary in order to extrapolate the tensile strength to the critical length determined by SFFT. This allowed calculating the adhesion properties of the basalt fibers. It was shown that fiber–matrix adhesion is dependent on both the presence of sizing on the fiber surface, as well as on the modification of the matrix.     

Bio‐Inspired,Self‐Toughening Polymers Enabled by Plasticizer‐Releasing Microcapsules

A new concept for the design of self‐toughening thermoplastic polymers is presented. The approach involves the incorporation of plasticizer‐filled microcapsules (MCs) in an intrinsically rigid and brittle matrix polymer. The intriguing adaptability that this simple tactic enables is demonstrated with composites composed of a poly(lactic acid) (PLA) matrix and 5–20% w/w poly(urea‐formaldehyde) (PUF) MCs that contained hexyl acetate as plasticizer. At low strain (<1.5%), the glassy PLA/MC composites remain rigid, although the intact MCs reduce the Young's modulus and tensile strength by up to 50%. While the neat PLA shows brittle failure at a strain of around 2.5%, the composites yield in this regime, because the MCs rupture and release their plasticizing cargo. This effect leads up to 25‐fold increase of the elongation at break and 20‐fold increase of the toughness vis‐à‐vis the neat PLA, while the impact on modulus and ultimate stress is much smaller. Ballistic impact tests show that the self‐toughening mechanism also works at much higher strain rates than applied in tensile tests and the operating mechanism is corroborated through systematic thermomechanical studies that involved dynamic mechanical testing and thermal analysis.     

改性马来酸酐橡胶接枝物增韧尼龙6的制备及表征

为了促进橡胶接枝物与尼龙6(PA6)的相容性并提高增韧效果,利用马来酸酐和对苯二胺合成了一种含酰胺键的二元羧酸,命名为对苯马来二酰胺二酸(改性马来酸酐,MDMA),并将MDMA接枝到三元乙丙橡胶(EPDM)上,制备出不同接枝率的改性马来酸酐橡胶接枝物(EPDM-g-MDMA),以EPDM-g-MDMA与PA6质量比为30∶70,通过共混挤出制备了含不同接枝率接枝物的EPDM-g-MDMA/PA6共混物。通过核磁共振和红外光谱对MDMA进行了测试,表明成功合成了所需要的二元羧酸。对共混物进行了相容性测试、DSC、熔融指数(MI)、SEM、拉伸和冲击力学性能测试。结果表明:随着接枝率的增大,共混物的熔融峰温度略有降低,其熔体黏度不断增大,橡胶接枝物在PA6基体中有良好的分散性,使EPDM-g-MDMA/PA6共混物的冲击强度提高了5.5倍,说明EPDM-g-MDMA对PA6的增韧效果较为明显。     

Glass-fiber reinforcement of in situ compatibilized polypropylene/polyethylene blends

Polypropylene and low-density polyethylene (LDPE) were melt-blended at proportions 75/25, 50/50, and 25/75 w/w, respectively. These blends were reinforced with two types of glass fibers added at an amount of 20 wt %: the E-type fibers without any surface treatment and the M-type fibers, which were treated with y-methacryloxy propyltrimethoxy silane coupling agent. Poly(propylene-g-maleic anhydride) with 0.8 mol % maleic anhydride content and poly(ethylene-co-vinyl alcohol) with 7.5 mol % vinyl alcohol content were added at a 50/50 w/w proportion as in situ reactive compatibilizers at an amount of 10 wt %. The thermoplastic composite materials have higher tensile strength as well as impact strength compared to the unreinforced blends. The simultaneous process of the in situ blend compatibilization, along with the incorporation of glass fibers in the thermoplastic matrix, leads to a significant improvement of the mechanical properties as compared to the properties of the composite materials with the uncompatibilized matrix. Scanning electron microscopy and micro-Raman spectroscopy have been used to study the adhesion of the thermoplastic matrix onto the glass fibers. Significantly better adhesion characteristics were observed in the composites containing M-type glass fibers, with LDPE adhering the most on the fibers. This better adhesion was reflected in the improved mechanical properties of the composites.     

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.     

Grafting effects of polypropylene/polyethylene blends with maleic anhydride on the properties of the resulting wood-plastic composites

In the presented study, polypropylene (PP) and high density polyethylene (PE) were blended at the ratios of 80/20 and 20/80 to simulate recycled waste thermoplastic mixtures. The effects of in situ grafting of PP/PE blends with maleic anhydride through the extruder on the mechanical and rheological properties of resulting wood/plastic composites were investigated. Different ratios of PP and PE in the blends created distinct properties in the resulting composites. Grafting of PP and PE blends improved the tensile and flexure properties of the resulting composites. The composites exhibited a reduced water uptake and resultant dimensional swelling due to grafting with maleic anhydride. Grafting of the blends also considerably improved the interfacial bonding and enhanced the dispersion of wood in the matrix, as evidenced by rheological analysis and scanning electron microscopy.     

Mechanical and Antibacterial Properties of Injection Molded Polypropylene/TiO2 Nano-Composites:Effects of Surface Modification

Polypropylene (PP)/titanium dioxide (TiO2) nano-composites were prepared by melt compounding with a twin screw extruder. Nanoparticles were modified prior to melt mixing with maleic anhydride grafted styrene-ethylene-butylene-styrene (SEBS-g-MA) and silane. The composites were injection molded and mechanical tests were applied to obtain tensile strength, elastic modulus and impact strength. Antibacterial efficiency test was applied on the injection molded composite plaques by viable cell counting technique. The results showed that the composites including SEBS-g-MA and silane coated TiO2 gave better mechanical properties than the composites without SEBS-g-MA. Antibacterial efficiency of the composites varied according to the dispersion and the concentration of the particles and it was observed that composites at low content of TiO2 showed higher antibacterial property due to the better photocatalytic activity of the particles during UV exposure.     

Effect of a novel coupling agent,alkyl ketene dimer,on the mechanical properties of wood–plastic composites

The objective of this study was to investigate the incorporation of poplar wood fibers both with and without a novel coupling agent, alkyl ketene dimer (AKD), on the mechanical properties of wood fiber/polypropylene (PP) composites. The resulting properties were compared to those obtained with the most commonly used coupling agent, maleic anhydride grafted PP (MAPP). Tensile and impact strengths of the composites decreased with increasing poplar wood fibers content. Tensile modulus of the composites increased by the incorporation of the wood fibers content up to 70 wt% but further increment in the wood fibers decreased the tensile modulus. At the constant content of poplar wood fibers (70 wt%), the tensile strength determined for the coupled composites with 5% AKD increased by 41% in comparison with the non-coupled composites while the tensile modulus increased by 45%, the impact strength of the coupled composites increased by 38%. The performance of 5% AKD on the mechanical properties of the composites is a little better than 3% MAPP. The good performance of 5% AKD is attributed to the enhanced compatibility between the poplar wood fibers and the polymer matrix. The increase in mechanical properties of the composites demonstrated that AKD is an effective coupling agent for wood fiber/PP composites.     

Modified treatment for carbonized cellulose nanofiber application in composites

In the present study, carbon nanofibers (CNF) from carbonized cellulose nanofibers (CCNF) were prepared by carbonizing freeze-dried cellulose nanofibers first, then preparing acrylonitrile-butadienestyrene (ABS)/CCNF nanocomposites by extruder. To increase the dispersibility and operability of the CCNF, the ultrasound-assisted master batch method was adopted to make an ABS/CCNF master batch. Dicumyl peroxide and maleic anhydride were added to increase the interface compatibility between the CCNF and the ABS by reactive extrusion. The surface morphology, chemical structure, and mechanical properties of the ABS/CCNF nanocomposites were characterized by SEM, FTIR, and DMA/tensile tests, respectively. The tensile strength of ABS/CCNF was improved 36% compared to that of ABS. The improved properties demonstrated that the approach used in this study has the potential to solve the bottleneck issues of mass producing and applying CNF in a green way.     

胶原蛋白/低密度聚乙烯复合材料的制备与性能

为了探讨胶原蛋白（HC）和相容剂马来酸酐接枝低密度聚乙烯（LDPE-g-MAH）对聚合物材料性能产生的影响,以低密度聚乙烯（LDPE）为基体,用共混挤出的方法制备了HC/LDPE复合材料和HC/LDPE-MAH复合材料,并将复合材料注塑成不同规格样条。通过力学性能测试、SEM和热分析等表征方法研究了HC和LDPE-g-MAH含量对HC/LDPE及HC/LDPE-MAH复合材料结构和性能的影响。结果表明：当HC加入量为5wt%时,HC/LDPE复合材料拉伸强度达到最大值15.824 MPa;LDPE-g-MAH的加入可明显改善界面粘结性,提高材料力学性能及热稳定性,当HC含量为20wt%,LDPE-g-MAH含量为4wt%时,HC/LDPE-MAH复合材料的拉伸性能最优。     

The effect of types of maleic anhydride-grafted polypropylene (MAPP) on the interfacial adhesion properties of bio-flour-filled polypropylene composites

The effect of processing temperature on the interfacial adhesion, mechanical properties and thermal stability of bio-flour-filled, polypropylene (PP) composites was examined as a function of five different maleic anhydride-grafted PP (MAPP) types. To investigate the effect on the interfacial adhesion of the composites, the five MAPP types were subjected to characterization tests. The MAPP-treated composites with sufficient molecular weight and maleic anhydride (MA) graft (%) showed improved mechanical and thermal stability. The enhanced interfacial adhesion, and mechanical and thermal stability of the MAPP-treated composites was strongly dependent on the amount of MA graft (%) and the MAPP molecular weight. The morphological properties of the MAPP-treated composites showed strong bonding and a paucity of pulled-out traces from the matrix in the two phases. In addition, the improved interfacial adhesion of the MAPP-treated composites was confirmed by spectral analysis of the chemical structure using attenuated total reflectance (FTIR-ATR). The crystallinity of PP, MAPP, MAPP-treated composites and non-treated composites was investigated using wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC).