Composites based on maleated polypropylene and methyl cellulosic fiber: Mechanical and thermal properties

Composites based on maleated polypropylene and methyl cellulosic fiber were prepared by extrusion followed by injection molding. The methyl cellulosic fiber was pretreated with tetrabutyl orthotitanate prior to compounding. The mechanical and thermal properties, as well as morphology of composites, were investigated by means of tensile, impact, dynamic mechanical analysis, thermogravimetric measurements, and scanning electron microscopy. Static tensile tests showed that the stiffness and tensile strength of composites tend to increase with increasing fiber content. However, the elongation at break appeared to decrease with increasing fiber content. In contrast, the impact strength of composites increased slightly with increasing fiber content. The improvements in tensile and impact properties were attributed to the interaction between the functional group of maleic anhydride and tetrabutyl orthotitanate. Such interaction tended to improve the interfacial bonding between the methyl cellulosic fiber and polypropylene matrix. Thermogravimetric measurements revealed that the incorporation of methyl cellulosic fiber into maleated polypropylene results in a marked reduction of thermo‐oxidative stability. The effects of coupling agent additions on the mechanical properties of composites are discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1647–1653, 1999     

Influence of Fiber Characteristics and Manufacturing Process on the Structure and Properties of Aramid Paper

The influence of fiber characteristics and calendering on the structure and properties of aramid paper was investigated. Laboratory aramid handsheets were prepared, and the structure and properties of them were investigated by Field Emission Scanning Electron Microscopy (FESEM), Dynamic Mechanical Analysis (DMA), X-ray Diffractometer (XRD) and strength test. A comparison with commerical Nomex papers showed that overdrawn fibers with high initial modulus and film-like fibrids were helpful for improving the interface bonding and mechanical strength of aramid paper. Hot calendering improved the crystallinity, storage modulus and interface bonding of aramid materials, thereby greatly improving the mechanical strength of aramid paper.     

Study of jute fiber reinforced polyester composites by dynamic mechanical analysis

Cyanoethylation of jute fibers in the form of nonwoven fabric was studied, and these chemically modified fibers were used to make jute–polyester composites. The dynamic mechanical thermal properties of unsaturated polyester resin (cured) and composites of unmodified and chemically modified jute–polyester were studied by using a dynamic mechanical analyzer over a wide temperature range. The data suggest that the storage modulus and thermal transition temperature of the composites increased enormously due to cyanoethylation of fiber. An increase of the storage modulus of composites, prepared from chemically modified fiber, indicates its higher stiffness as compared to a composite prepared from unmodified fiber. It is also observed that incorporation of jute fiber (both unmodified and modified) with the unsaturated resin reduced the tan δ peak height remarkably. Composites prepared from cyanoethylated jute show better creep resistance at comparatively lower temperatures. On the contrary, a reversed phenomenon is observed at higher temperatures (120°C and above). Scanning electron micrographs of tensile fracture surfaces of unmodified and modified jute–polyester composites clearly demonstrate better fiber–matrix bonding in the case of the latter. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1505–1513, 1999     

木粉增强HDPE复合材料的制备及其性能研究

以废弃木粉为增强材料,采用双螺杆挤出机,制备木粉增强高密度聚乙烯复合材料,研究改善木粉增强高密度聚乙烯复合材料力学性能的途径。结果表明,随着木粉加入量的增加复合体系的力学性能得到明显改善;通过适当的方法对木粉进行表面处理、对基体树脂进行改性,可以有效地提高复合体系的界面粘接强度,大幅度改善复合体系的力学性能;采用短切玻璃纤维与木粉组合,可以获得力学性能很高,能作为结构材料使用的复合材料。     

Recycled polypropylene reinforced with curaua fibers by extrusion

Curaua fibers were studied as reinforcing agents for postconsumer polypropylene. The composites were processed by extrusion. The composite properties were investigated by mechanical tests, thermal methods, melt flow index, surface morphology, and water uptake. The variables studied were as follows: fiber contents (10 to 40 wt %), fiber surface treatment, initial fiber length, and modification of the polypropylene matrix. The treatment of the fiber with 5 wt % NaOH aqueous solution did not improve fiber‐matrix adhesion and the composites using 20 wt % of untreated curaua fibers presented the better mechanical properties. Feeding the extruder with fibers having shorter lengths (0.01–0.4 mm) produced better fiber dispersion, improving the mechanical properties of the composites. Composites prepared using fibers without surface treatment with postconsumer polypropylene and with polypropylene modified with maleic anhydride showed mechanical properties and water uptake similar to composites using the same polymer reinforced with other lignocellulosic fibers. The extrusion process caused also partial fibrillation of the fibers, improving their aspect ratio. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A comparative study on the mechanical and degradation properties of plant fibers reinforced polyethylene composites

Coir and abaca fiber‐reinforced linear low density polyethylene (LLDPE) composites (30 wt% fiber) were prepared by compression molding. Coir and abaca fibers were treated with methyl methacrylate (MMA) using ultraviolet radiation to improve the mechanical properties of the composites. Concentration of MMA and radiation dose was optimized. It was found that 30% MMA in methanol along with photoinitiator Darocur‐1173 (2%) and 15th pass of radiation rendered better performance. Chemically treated fiber‐reinforced specimens yielded better mechanical properties compared to the untreated composites, whereas coir fiber composites had better mechanical properties than abaca fiber reinforced ones. For the improvement of the properties, optimized coir (coir fiber treated with 30% MMA) and abaca (abaca fiber treated with 40% MMA) fibers were again treated with aqueous starch solution (2%–8%, w/w) for 2–7 min. Composites made of 3%‐starch‐treated coir fiber (5 min soaking time) showed the best mechanical properties than that of abaca‐fiber‐based composites. Water uptake and soil degradation tests of the composites were also performed. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

玻璃纤维对PTFE/SiO2复合基板材料性能的影响

采用表面改性、物料混合、压延成型、高温真空热压烧结工艺,得到了不同含量玻璃纤维(GF)增强聚四氟乙烯(PTFE)/二氧化硅(SiO2)复合基板材料,考察分析了GF含量对复合材料微观形貌、密度、吸水率、拉伸性能、压缩性能以及微波介电性能的影响情况。结果表明,随着GF含量的增加,PTFE/SiO2复合材料的密度逐渐减小,吸水率和损耗因子逐渐增大,拉伸模量、压缩模量和相对介电常数呈现出先增大后减小的趋势。当PTFE/SiO2复合材料中加入2%的GF时,复合材料具有良好的综合性能,密度为2.085 g/cm3,吸水率为0.094%,拉伸模量为1351 MPa,压缩模量为1643 MPa,相对介电常数为2.93,损耗因子为1.04×10–3。     

Fluorinated aramid fiber reinforced polypropylene composites and their characterization

Polymer fibers are one of the main substances used for the reinforcement of plastic composites. Surface modification of aramid fiber was performed by direct fluorination. The crystallinity and the decomposition temperature of the modified fiber were increased. Scanning electron microscope shows that the roughness increases in the modified fiber. Composites were prepared by using modified and unmodified fibers. It was shown that the mechanical and thermal properties increase for modified fiber reinforcing composites. To reduce the fiber degradation or breakdown, composites were prepared by solution casting method. POLYM. COMPOS., 28:462–469, 2007. © 2007 Society of Plastics Engineers     

Polyamide‐6 composites reinforced with cellulose fibers and fabricated by extrusion: Effect of fiber bleaching on mechanical properties and stability

We prepared polyamide‐6 (PA‐6) composites using bleached and semibleached cellulose fibers from Eucalyptus species by processing in a corotating interpenetrating twin‐screw extruder. PA‐6 is a challenging matrix because of its high processing temperature, which overlaps the thermodegradation temperature of the fibers. The selection of the processing conditions for extrusion and the use of the lubricant ethylene bis (stearamide) permitted the production of composites with 20, 30, and 40 wt% of bleached fibers, which are lighter than the corresponding glass fiber composites. Composites with 30 wt% of bleached fibers yield the best mechanical properties and good fiber/matrix interaction, as demonstrated by mechanical tests and scanning electron microscopy. X‐ray photoelectron spectroscopy studies showed that the natural moisture in the fibers promotes the fiber/matrix interaction through the formation of ester bonds. We assessed the effect caused by the presence of lignin in the fibers. Composites containing 30 wt% of semibleached fibers maintained the flexural properties and showed small improvements in thermal stability when compared with bleached fiber composites; however, there is a slight decrease in the tensile properties. Through accelerated aging tests, we observed that increased lignin concentration in the fibers reduced the formation of carbonyl compounds on sample surfaces, indicating a stabilization effect. POLYM. COMPOS., 38:299–308, 2017. © 2015 Society of Plastics Engineers     

Preparation of rubber composites from ground tire rubber reinforced with waste‐tire fiber through mechanical milling

Composites made from ground tire rubber (GTR) and waste fiber produced in tire reclamation were prepared by mechanical milling. The effects of the fiber content, pan milling, and fiber orientation on the mechanical properties of the composites were investigated. The results showed that the stress‐induced mechanochemical devulcanization of waste rubber and the reinforcement of devulcanized waste rubber with waste‐tire fibers could be achieved through comilling. For a comilled system, the tensile strength and elongation at break of revulcanized GTR/fiber composites reached maximum values of 9.6 MPa and 215.9%, respectively, with 5 wt % fiber. Compared with those of a composite prepared in a conventional mixing manner, the mechanical properties were greatly improved by comilling. Oxygen‐containing groups on the surface of GTR particles, which were produced during pan milling, increased interfacial interactions between GTR and waste fibers. The fiber‐filled composites showed anisotropy in the stress–strain properties because of preferential orientation of the short fibers along the roll‐milling direction (longitudinal), and the adhesion between the fiber and rubber matrix was improved by the comilling of the fiber with waste rubber. The proposed process provides an economical and ecologically sound method for tire‐rubber recycling. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4087–4094, 2007     

Fatigue life of coir fiber reinforced PP composites: Effect of compatibilizer and coir fiber contents

The fatigue behavior of polypropylene/coir fiber composites was investigated. Composites were prepared according to an experimental statistical design, in which the independent variables coir fiber and compatibilizer content were varied. The compatibilizer used was maleic anhydride grafted polypropylene (PP‐g‐MA). Compatibilizer free composites were also prepared. Composites were prepared in a corotating twin‐screw extruder and the mechanical behavior of polypropylene/coir fiber composites were assessed through monotonic (tensile) and cyclic (fatigue) tests. Fatigue load controlled tests were conducted under tension–tension loads at a frequency of 6 Hz. The fracture mechanism was accompanied by surface fracture analyses using scanning electron microscopy (SEM). The results indicated the need for using compatibilizer in the composites; however, increase in compatibilizer content did not affect composite fatigue lifetime. Coir content was the variable with the strongest effect on composite properties; increasing this variable caused significant increase in fatigue life. POLYM. ENG. SCI., 53:2159–2165, 2013. © 2013 Society of Plastics Engineers     

Effect of different fiber loadings and sizes on pultruded kenaf fiber reinforced unsaturated polyester composites

Application of the available natural resources became crucial for developing sustainability recently. The use of natural fiber as reinforced materials in polymer composite materials is gaining new interest from within industry. In this research, the effect of different fiber loadings and different types of kenaf yarns, used on the properties of Pultruded Kenaf Fiber Reinforced Composites (PKFRC), was studied. The pultruded composite samples were prepared with different fiber loadings and sizes (tex) of kenaf fiber. Three different fiber loadings, i.e., 60, 65, and 70% were used during the preparation of the PKFRC samples. Flexural and compression testing was performed, to study the effect of different fiber loadings and different kenaf fiber yarns, on the mechanical properties of kenaf fiber pultruded composites. The results show that the highest fiber loading of 70% gave more desirable flexural and compression properties to the PKFRC. The use of twist kenaf yarn fiber showed lower mechanical properties of PKFRC as compared to the single kenaf yarn. Damage configurations and accumulations for each loading case were examined. A morphological study, using optical microscopy (OM) revealed the type of fracture that occurred in the pultruded samples after mechanical testing. POLYM. COMPOS., 36:1224–1229, 2015. © 2014 Society of Plastics Engineers     

Cure characteristics and mechanical properties of short nylon fiber‐reinforced nitrile rubber composites

Acrylonitrile butadiene rubber (NBR)‐based composites were prepared by incorporating short nylon fibers of different lengths and concentration into the matrix using a two‐roll mixing mill according to a base formulation. The curing characteristics of the samples were studied. The influence of fiber length, loading, and rubber crosslinking systems on the properties of the composites was analyzed. Surface morphology of the composites has been studied using Scanning Electron Microscopy (SEM). Addition of nylon fiber to NBR offers good reinforcement, and causes improvement in mechanical properties. A fiber length of 6 mm was found to be optimum for the best balance of properties. It has been found that at higher fiber loadings, composites show brittle‐type behavior. Composites vulcanized by the dicumyl peroxide (DCP) system were found to have better mechanical properties than that by the sulfur system. The swelling behavior of the composites in N,N‐dimethyl formamide has been analyzed for the swelling coefficient values. Composites vulcanized in the DCP system were found to have higher rubber volume fraction than that in the sulfur system, which indicates better rubber–fiber interaction in the former. The crosslink densities of various composites were also compared. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1023–1030, 2004     

Influence of chemical treatments on cellulose fibers for use as reinforcements in poly(ethylene‐co‐vinyl acetate) composites

This work evaluates different chemical treatments on cellulose fibers as reinforcement agents in poly(ethylene‐vinyl acetate) (EVA) composites. The cellulose fibers were prepared with three chemical modifications using triethoxyvinylsilane, acetic anhydride (AA), and glycidyl methacrylate (GMA). Composites were prepared with 10 phr of cellulose fibers by means of extrusion and hot press conformation. The fiber treatment levels were successfully demonstrated through Fourier transform infrared spectroscopy with the appearance of characteristic bands in each chemical group, and scanning electron micrographs showed altered textures on the surfaces, polymerized material and fiber agglomerations after the chemical treatments that were most evident in the AA and GMA treatments. The composites reinforced with treated fibers showed improvement in their mechanical properties at the yield points and were reduced in deformation. When activated with dicumyl peroxide, the mechanical properties were even more improved and the interface regions exhibited better interactions between the cellulose fibers and the EVA matrix. POLYM. COMPOS., 37:1991–2000, 2016. © 2015 Society of Plastics Engineers     

Injection molding of polypropylene reinforced with short jute fibers

Composites with polypropylene (PP) and jute fiber were prepared by injection molding technique. Maleic anhydride-grafted polypropylene was added as coupling agent to improve the adhesion between jute fiber and PP. A high fiber attrition was noted during injection molding, which had negative effects on the mechanical properties of the composites. The coupling agent improved the tensile and bending strengths, however the elastic and bending moduli were found not to be influenced by the coupling agent. The role of the average fiber length in strengthening of the composites was interpreted with help of the critical fiber length. Fracture surfaces of the composites, and the fiber orientations, were investigated by scanning electron microscopy and light microscopy, respectively. © 1996 John Wiley & Sons, Inc.     

A comparison of compounding processes for wood-fiber/thermoplastic composites

This study was carried out to investigate the feasibility of developing a continuous compounding process for wood-fiber/thermoplastic composites using the Szego mill, a unique, high speed planetary ring-roller grinding mill. Prior to compounding, air-dried sawdust was ground to evaluate the grinding effect in the mill. As the feed rate and the mill speed increased, the particle size increased and decreased, respectively. Sawdust particles were successfully compounded in linear low-density polyethylene using the Szego mill without any major heat application. A Gelimat mixer, used for the compounding of wood fiber through a high-shear thermokinetic mixing process, was also employed for comparison. Composites with 30 wt% wood fiber were prepared by both compounding processes, and their mechanical properties were evaluated. The use of a compatibilizer in compounding improved the mechanical properties of the composites regardless of the compounding process. The composites prepared by Szego mill compounding showed comparable strength properties with their counterparts from the Gelimat mixer. Power consumption during mill compounding was in the range of twin-screw extruder processing.     

Cure characteristics and mechanical properties of styrene-butadiene rubber/hydrogenated acrylonitrile-butadiene rubber/silica composites

Composites of styrene butadiene rubber (SBR), hydrogenated acrylonitrile–butadiene rubber (HNBR) and silica were prepared. Sulfur (S), dicumyl peroxide (DCP) and a combination of S and DCP (M) were used as curing agents, respectively. The morphology of the composites with different blend ratio was examined to correlate with observations on mechanical properties by scanning electron microscopy. The effects of blend ratio and curing systems on the curing characteristics and mechanical properties, such as stress–strain behavior, tensile strength, elongation at break and hardness of SBR/HNBR/Silica composites, were studied. Composites prepared by M curing systems showed comparatively better mechanical properties, wet traction and rolling resistance than S and D curing systems. The tensile strength, tear strength, and elongation at break were improved by adding HNBR for M curing systems. The wet traction of the vulcanizates containing HNBR was better than that of the vulcanizates without HNBR. A relatively uniform dispersion of silica was observed for SBR/HNBR/silica compositions compared with SBR/silica composites.     

Effect of nonionizing radiation on the physicomechanical properties of banana fiber/pp composites with HEMA

Banana fiber‐reinforced polypropylene (PP)‐based unidirectional composites (40% fiber by weight) was manufactured by compression molding. Banana fibers and PP sheets were treated with UV radiation at different intensities and then composites were fabricated. It was found that mechanical properties of irradiated banana fiber and irradiated PP‐based composites were found to increase significantly compared to that of untreated counterparts. Irradiated banana fibers were also treated with 2‐hydroxyethyl methacrylate (HEMA) mixed with methanol (MeOH) under thermal curing method at different temperatures (30–70°C) for different curing times (20–60 min). A series of solutions of different concentrations of HEMA in methanol along with 2% benzyl peroxide were prepared. Monomer concentration, curing temperature and curing time were optimized in terms of polymer loading and mechanical properties. Composites made of 15% HEMA, 50°C and 40 min curing time showed the best mechanical properties than those of untreated composite. Scanning electron microscopy (SEM), water uptake, and simulating weathering test of the composites were also investigated. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Comparative experimental measurements of jute fiber/polypropylene and coir fiber/polypropylene composites as ionizing radiation

Jute and coir fiber‐reinforced polypropylene (PP) composites (45 wt% fiber) were prepared by compression molding. Composites were fabricated with irradiated jute fiber/irradiated PP and irradiated coir fiber/irradiated PP at different doses (250–1,000 krad). It was revealed that jute‐based composites had better mechanical properties as compared to coir‐based composites. Interfacial shear strength of jute/PP and coir/PP systems was measured by using the single‐fiber fragmentation test. Scanning electron microscopy investigation shows poor fiber matrix adhesion for coir‐based composites than that of jute‐based composites. Water uptake and soil degradation tests of the composites were also performed. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Mechanical,thermal, and morphological properties of maleic anhydride‐g‐polypropylene compatibilized and chemically modified banana‐fiber‐reinforced polypropylene composites

Composites were prepared with chemically modified banana fibers in polypropylene (PP). The effects of 40‐mm fiber loading and resin modification on the physical, mechanical, thermal, and morphological properties of the composites were evaluated with scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Infrared (IR) spectroscopy, and so on. Maleic anhydride grafted polypropylene (MA‐g‐PP) compatibilizer was used to improve the fiber‐matrix adhesion. SEM studies carried out on fractured specimens indicated poor dispersion in the unmodified fiber composites and improved adhesion and uniform dispersion in the treated composites. A fiber loading of 15 vol % in the treated composites was optimum, with maximum mechanical properties and thermal stability evident. The composite with 5% MA‐g‐PP concentration at a 15% fiber volume showed an 80% increase in impact strength, a 48% increase in flexural strength, a 125% increase in flexural modulus, a 33% increase in tensile strength, and an 82% increase in tensile modulus, whereas the heat deflection temperature increased by 18°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010