Improvement of impact property of natural fiber–polypropylene composite by using natural rubber and EPDM rubber

In this research, vetiver grass was used as a filler in polypropylene (PP) composite. Chemical treatment was done to modify fiber surface. Natural rubber (NR) and Ethylene Propylene Diene Monomer (EPDM) rubber at various contents were used as an impact modifier for the composites. The composites were prepared by using an injection molding. Rheological, morphological and mechanical properties of PP and PP composites with and without NR or EPDM were studied. Adding NR or EPDM to PP composites, a significant increase in the impact strength and elongation at break is observed in the PP composite with rubber content more than 20% by weight. However, the tensile strength and Young’s modulus of the PP composites decrease with increasing rubber contents. Nevertheless, the tensile strength and Young’s modulus of the composites with rubber contents up to 10% are still higher than those of PP. Moreover, comparisons between NR and EPDM rubber on the mechanical properties of the PP composites were elucidated. The PP composites with EPDM rubber show slightly higher tensile strength and impact strength than the PP composites with NR.     

Novel toughened polylactic acid nanocomposite: Mechanical,thermal and morphological properties

The objective of the study is to develop a novel toughened polylactic acid (PLA) nanocomposite. The effects of linear low density polyethylene (LLDPE) and organophilic modified montmorillonite (MMT) on mechanical, thermal and morphological properties of PLA were investigated. LLDPE toughened PLA nanocomposites consisting of PLA/LLDPE blends, of composition 100/0 and 90/10 with MMT content of 2 phr and 4 phr were prepared. The Young’s and flexural modulus improved with increasing content of MMT indicating that MMT is effective in increasing stiffness of LLDPE toughened PLA nanocomposite even at low content. LLDPE improved the impact strength of PLA nanocomposites with a sacrifice of tensile and flexural strength. The tensile and flexural strength also decreased with increasing content of MMT in PLA/LLDPE nanocomposites. The impact strength and elongation at break of LLDPE toughened PLA nanocomposites also declined steadily with increasing loadings of MMT. The crystallization temperature and glass transition temperature dropped gradually while the thermal stability of PLA improved with addition of MMT in PLA/LLDPE nanocomposites. The storage modulus of PLA/LLDPE nanocomposites below glass transition temperature increased with increasing content of MMT. X-ray diffraction and transmission electron microscope studies revealed that an intercalated LLDPE toughened PLA nanocomposite was successfully prepared at 2 phr MMT content.     

Polycarbonate/Polypropylene/Fibrillar Silicate Ternary Nanocomposites： Morphology and Mechanical Properties

Polycarbonate （pc）/polypropylene （pp）/silicate attapulgite （AT） ternary nanocomposites were first prepared via the two-step melt blending process. Phase structure of the ternary composites was characterized by transmission electron microscopy （TEM） and dynamic mechanical analysis （DMA）, in which the morphology of encapsulation of AT by PP in the PC matrix were observed. The mechanical properties of the ternary composites were investigated using the tensile tester and Izod impact tester. The results show that encapsulation of AT by PP in PC enhances the toughness of the matrix effectively and give the best tensile and impact strength.     

Effects of maleated polypropylene on the morphology,thermal and mechanical properties of short carbon fiber reinforced polypropylene composites

The aim of this study was to determine the effect of the maleic anhydride grafted polypropylene (PP-g-MAH) on the properties of short carbon fiber (CF) reinforced polypropylene (PP) composites. The composites were prepared by melt blending and injection molding techniques at different percentages of CF. Tensile tests, hardness, differential scanning calorimeter (DSC) and scanning electron microscopy (SEM) were performed to characterize the physical and morphological properties of the prepared composites. It was observed from SEM photographs that modification with PP-g-MAH improved the interfacial adhesion between the carbon fibers and PP matrix. The ultimate tensile strength, hardness and modulus values of modified PP composites were higher compared to the values of CF reinforced PP composites. Melting temperature of all composites was not changed significantly with increasing CF content; however degree of crystallinity values were decreased with the increasing CF content level.     

汉麻纤维表面改性对其增强聚丙烯复合材料性能及挥发性有机化合物释放影响

通过非织造-热压工艺制备了汉麻纤维增强聚丙烯（HF/PP）复合材料。采用热重-质谱联用仪（TG-MS）研究了HF/PP复合材料的挥发性有机化合物（Volatile organic compounds,VOC）释放来源及汉麻经聚乙烯醇（PVA）改性和尿素改性对HF/PP复合材料VOC释放的影响,同时研究了两种改性方法对HF/PP复合材料热学性能和力学性能的影响。结果表明：HF/PP复合材料中的VOC主要来源于汉麻纤维,改性后的HF/PP复合材料力学性能相比未处理的均有不同程度的提升,尿素改性后,HF/PP复合材料的拉伸强度和弯曲强度达到最大值,较未处理时分别提升了19.32%和15.04%。PVA改性后,HF/PP复合材料的拉伸模量、弯曲模量和剪切强度达到最大值,相比未改性时分别提升了17.72%、15.94%和24.72%。改性后HF/PP复合材料热稳定性能和VOC释放相较未处理时均得到了优化：PVA改性后HF/PP复合材料热稳定性最优,三个阶段总活化能较未处理时提高了121.99%,达到了392.56 kJ·mol^-1,并且HF/PP复合材料热稳定性与界面性能密切相关;尿素及PVA改性后HF/PP复合材料的总VOC（TVOC）释放量相较未处理时均降低。     

Hygromechanical properties of composites of crosslinked allylglycidyl-ether modified starch reinforced by wood fibres

In a previous work a new family of thermoset composites of allylglycidyl ether modified starch as matrix, an ethylene glycol dimethacrylate as cross-linker and a wood fibre as reinforcement were prepared. The aim of the present work was to study the hygromechanical properties of the new composites including density, dimensional stability in water, water uptake, stiffness, and ultimate strength in three-point bending. It was shown that the samples with a starch matrix of a high degree of substitution (DS = 2.3), HDS, absorbed less water, were more stable in water and had also higher stiffness and strength than corresponding composite samples with a starch matrix of low degree of substitution (DS = 1.3), LDS. Overall, the fibre addition improved water stability. An increased fibre content from 40 to 70% by weight had a negligible impact on the water uptake. An increase in fibre content did, however, improve the mechanical properties. The HDS-sample with highest fibre content, 70% by weight showed the highest Young’s modulus (3700 MPa) and strength (130 MPa), which are markedly higher compared with the samples based on the pure HDS matrix (Young’s modulus of 360 MPa and strength of 15 MPa). The measured Young’s modulus and tensile strength values were roughly one order of magnitude higher than earlier reported cellulosic fibre reinforced natural polymer composites.     

微注射成型高密度聚乙烯-线性低密度聚乙烯共混物的微结构及力学性能

为提高线性低密度聚乙烯（LLDPE）的拉伸强度和模量,扩大其应用领域,将三种不同相对分子质量的高密度聚乙烯（HDPE）分别与LLDPE共混,通过微注射成型技术制备HDPE-LLDPE制品。综合利用DSC、广角X射线衍射（WAXD）、小角X射线散射（SAXS）和拉伸性能测试研究了共混物在微注射成型过程中的结构演化及力学性能。拉伸测试结果表明,与纯LLDPE相比,HDPE-LLDPE的拉伸强度和模量随HDPE分子量的增加而增加。微结构分析结果显示,随HDPE分子量的增加,HDPE-LLDPE制品的分子链和片晶取向度增大、结晶度增加,且制品内形成了较多取向的Shish-Kebab晶体结构。通过分析微结构的表征结果,解释了HDPE-LLDPE的拉伸强度和模量显著提高的原因。     

功能化石墨烯/埃洛石纳米管对聚丙烯的协同强韧化改性研究

以功能化氧化石墨烯(GO)-埃洛石纳米管(HNTs)杂化材料(GO@HNTs)为纳米填料,以聚丙烯(PP)为基体,通过熔融共混法制备了不同GO@HNTs 含量的GO@HNTs/PP纳米复合材材料,并对所得杂化填料和PP纳米复合材料的结构与性能进行系统研究。研究结果表明,功能化GO与HNTs之间存在化学相互作用,二者之间形成的“屏障效应”抑制了彼此在PP基体中的团聚。仅添加0.5%GO@HNTs杂化纳米填料后,PP复合材料的拉伸强度和冲击强度分别较纯PP提高了17.5%和80.4%,与单独添加相同含量的GO或HNTs所得复合材料的力学性能相比,GO@HNTs杂化纳米填料对PP基体具有明显的协同增强增韧改性作用。与纯PP相比,GO@HNTs/PP试样表现出更高的储能模量、损耗模量和玻璃化转变峰值。由于GO@HNTs的“异相成核效应”和“物理热阻效应”,有效提高了PP纳米复合材料的结晶温度、熔融温度、结晶度和耐热分解温度。     

枣核/低密度聚乙烯复合材料的力学性能

为充分利用红枣精深加工产生的废弃物,以枣核(JP)和低密度聚乙烯(LLDPE)为主要材料,采用注塑成型法制备JP/LLDPE复合材料,并对其静态力学性能(拉伸、弯曲和冲击)和动态力学性能(动态黏弹性、蠕变行为和应力松弛行为)进行系统测试分析.静态力学性能分析表明,随JP含量的增加,JP/LLDPE复合材料的拉伸强度和冲...     

Sugarcane bagasse cellulose/HDPE composites obtained by extrusion

Natural fibers used in this study were both pre-treated and modified residues from sugarcane bagasse. Polymer of high density polyethylene (HDPE) was employed as matrix in to composites, which were produced by mixing high density polyethylene with cellulose (10%) and Cell/ZrO₂·nH₂O (10%), using an extruder and hydraulic press. Tensile tests showed that the Cell/ZrO₂·nH₂O (10%)/HDPE composites present better tensile strength than cellulose (10%)/HDPE composites. Cellulose agglomerations were responsible for poor adhesion between fiber and matrix in cellulose (10%)/HDPE composites. HDPE/natural fibers composites showed also lower tensile strength in comparison to the polymer. The increase in Young’s modulus is associated to fibers reinforcement. SEM analysis showed that the cellulose fibers insertion in the matrix caused an increase of defects, which were reduced when modified cellulose fibers were used.     

Reinforcement of polyethylene with polypropylene by a blending and deformation process

The blending of polymers to achieve either unique or intermediate properties has become a rather common practice. High density polyethylene (HDPE) and isotactic polypropylene (PP) are immiscible in the melt state and phase segregate. This behaviour and their difference in melting point (132 against 165° C) has been exploited to produce a uniaxial reinforcement of HDPE with PP fibres by a process of melt blending, and tensile drawing followed by annealing. Tensile drawing of the blends results in the transformation of each phase to a fibrous structure having an increased modulus and tensile strength. The annealing of this material to melt and recrystallize the HDPE converts it to a lower modulus ductile lamellar structure which is reinforced with the fibrous PP regions. Both the modulus and tensile strength in the fibre direction fit simple composite theory for isotropic HDPE filled with higher modulus PP fibres over the entire composition range.     

Characterization of polypropylene–polyethylene blends made of waste materials with compatibilizer and nano-filler

Waste polypropylene and polyethylene were blended by a twin-screw extruder with two compatibilizers (PE-g-MAH and EPDM) and an additive (O-MMT). The mechanical properties were measured firstly. By adding O-MMT, the tensile strength showed a decline while the impact strength made a promotion. The phase morphology was observed by scanning electron microscopy (SEM) to explore the fracture toughness of blends. The blend with EPDM had a better compatibilization than PE-g-MAH. X-ray diffraction was used to investigate the crystallization behavior and the result showed no change by blending. Moreover, further measurements such as thermogravimetric (TGA) and differential scanning calorimetry (DSC) were taken to show the thermal stability and crystallization temperature of the blend. Additionally, the storage modulus and loss modulus are measured by dynamic mechanical analysis (DMA), the presence of O-MMT caused the increases of the storage modulus and loss modulus.     

PP-g-Si与KH550对聚丙烯/滑石粉体系的增容效果

硅烷接枝聚丙烯（ＰＰ－ｇ－Ｓｉ）对聚丙烯／滑石粉（ＰＰ／Ｔａ）混合体系有一定的增容作用,可使复合材料的力学性能得以提高,占复合材料总质量３．５％的ＰＰ－ｇ－Ｓｉ（相当于含硅烷０．２％）对ＰＰ／Ｔａ体系的增容效果与含０．８％（质量分数）的ＫＨ５５０的增容效果相当,ＫＨ５５０对复合材料中聚丙烯（ＰＰ）的结晶熔融行为基本上无影响。而ＰＰ－ｇ－Ｓｉ能进一步使材料中ＰＰ的结晶峰温和熔融峰温提高。     

Vetiver–polypropylene composites: Physical and mechanical properties

Injection molded vetiver–polypropylene (PP) composites at various ratios of vetiver content and vetiver length were prepared. When compared to PP, vetiver–PP composites exhibited higher tensile strength and Young’s modulus but lower elongation at break and impact strength. An increase in vetiver content led to an increase in viscosity, heat distortion temperature, crystallization temperature, and Young’s modulus of the composites. On the other hand, the decomposition temperature, tensile strength, elongation at break, and impact strength decreased with increasing vetiver content. The chemical treatment of the vetiver grass improved the mechanical properties of the composites.     

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.     

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.     

Effect of fiber surface modification on the mechanical and water absorption characteristics of sisal/polyester composites fabricated by resin transfer molding

Sisal fibers were subjected to various chemical and physical modifications such as mercerization, heating at 100 °C, permanganate treatment, benzoylation and silanization to improve the interfacial bonding with matrix. Composites were prepared by these fibers as reinforcement, using resin transfer molding (RTM). The mechanical properties such as tensile, flexural and impact strength were examined. Mercerized fiber-reinforced composites showed 36% of increase in tensile strength and 53% in Young’s modulus while the permanganate treated fiber-reinforced composites performed 25% increase in flexural strength. However, in the case of impact strength, the treatment has been found to cause a reduction. The water absorption study of these composites at different temperature revealed that it is less for the treated fiber-reinforced composites at all temperatures compared to the untreated one. SEM studies have been used to complement the results emanated from the evaluation of mechanical properties.     

功能化石墨烯-SiO2协同增强增韧聚丙烯复合材料的制备与性能

先采用溶胶-凝胶法制备了氧化石墨烯（GO）-SiO₂杂化材料,再与聚丙烯（PP）进行熔融共混制备了GO-SiO₂/PP复合材料。分别采用FTIR、XRD、XPS、DSC、SEM、动态热机械分析（DMA）、拉伸及冲击等测试手段对填料及GO-SiO₂/PP复合材料的结构与性能进行了表征。FTIR和XPS分析表明,GO已经成功获得功能化。力学性能测试结果证实,GO-SiO₂对PP基体具有良好的强韧化协同改性作用,且优于SiO₂/PP及GO/PP复合材料体系。固定GO-SiO₂中GO与SiO₂的质量比为1∶1,当填料GO-SiO₂的质量分数为0.1wt%时,GO-SiO₂/PP复合材料的拉伸强度和冲击强度分别为38.9 MPa和7.6 kJ/m²,与纯PP基体相比分别提高了29.4%和66.3%。DSC测试表明,GO-SiO₂/PP复合材料中PP的熔融温度和结晶温度分别为167.4℃和111.7℃,与纯PP相比分别提高了4.7℃和5.2℃。DMA测试表明,GO-SiO₂的加入使GO-SiO₂/PP复合材料的储能模量增大,损耗模量峰向更高温度移动。SEM观察表明,当加入少量的GO-SiO₂时,填料能均匀的分散在基体中,但GO-SiO₂过多时,则容易形成团聚。     

Mechanical Properties of Thermoplastic and Thermoset Composites Reinforced with 3D Biaxial Warp-knitted Fabrics

In this study, two types of thermoplastic matrices (low melting point polyethylene terephthalate (LPET) fiber and polypropylene (PP) fiber) and glass fiber/epoxy resin/multi-walled carbon nanotubes (MWCNTs) were used to fabricate the thermoplastic and thermoset composite materials with 3D biaxial warp-knitted fabrics. Thermoplastic and thermoset composites were fabricated using hot-press and resin transfer molding (RTM) methods. The fabricated samples were tested with tensile and three-point flexural tests. In thermoplastic composites, samples in the 90° direction and LPET matrix showed the best tensile and flexural properties with an improvement of 39 and 21% tensile modulus and strength, 16 and 8% flexural modulus and strength compared to the PP samples in the same direction. In thermoset composites, samples in the 90° direction and MWCNTs showed the best improvement of the flexural modulus and strength with 97 and 58% compared to the samples without MWCNTs. This improvement can most likely be attributed to an increase in interfacial adhesion due to the presence of the carbon nanotubes.     

Mechanical properties and flame-retardant of PP/MRP/Mg(OH)2/Al(OH)3 composites

The flame retardant and mechanical properties of polypropylene (PP) composites filled with microencapsulated red phosphorus (MRP) and magnesium hydrate (Mg(OH)₂)/aluminum hydrate (Al(OH)₃) were measured. It was found that the synergistic effects between the MRP and Mg(OH)₂/Al(OH)₃ on the flame retardant and tensile properties of the composites were significant. The limit oxygen index and smoke density rank of the composites increased nonlinearly while the horizontal combustibility rate decreased nonlinearly with increasing the MRP weight fraction. The Young modulus and the tensile elongation at break increased while the tensile yield strength and tensile fracture strength decreased slightly with increasing the MRP weight fraction. Both the V-notched Izod and Charpy impact strength increased with increasing the MRP weight fraction. Moreover, the tensile yield strength of the composites estimated using an equation published previously was roughly close to the measured data.