Effect of chemical treatment on the properties of coir fiber reinforced polypropylene and polyethylene composites

Chemical treatment of reinforcement material is one of the main ways of improving the mechanical properties of natural fiber reinforced polymer composites. In the present study, coir fiber was used as reinforcement material, while polypropylene (PP) and polyethylene (PE) polymer were used as matrix material. Before reinforcing with polymer, raw coir fiber was chemically treated with basic chromium sulfate and sodium bicarbonate in a sieve shaker. Hot‐pressed method was used for composite manufacturing during which the fiber loading was varied at 0, 5, 10, 15, and 20 wt%. Comparison of the properties of raw and chemically treated coir fiber reinforced PP and PE was conducted. Mechanical characteristics of the composites were evaluated using tensile, flexural, impact, and hardness tests. Water absorption test was conducted to know water uptake characteristics. Microstructural analysis using a scanning electron microscope was performed to observe the adhesiveness between the matrix and the fiber. Thermogravimetric analysis was done to observe the physical and chemical changes in fiber and composites. The results showed that chemical treatment improved the physical, mechanical, and thermal properties of the manufactured composites. PP composites had better properties as compared to PE composites, while higher fiber loading resulted in better mechanical properties of the resultant composites. POLYM. COMPOS., 38:1259–1265, 2017. © 2015 Society of Plastics Engineers     

黄麻纤维增强聚丙烯的力学性能

本文讨论了注塑成型黄麻纤维增强聚丙烯的制备方法和力学性能.将纤维重量含量分别为10%、20%和30%的复合材料进行比较,分析纤维含量对复合材料拉伸、弯曲和冲击性能的影响;将纤维分别切成约3mm、5mm和10mm长制成复合材料进行比较,分析纤维长度对复合材料拉伸、弯曲和冲击性能的影响.掺入黄麻纤维能使聚丙烯的拉伸和弯曲性能提高,但使其冲击强度降低;随纤维含量的增加或纤维长度的增加,复合材料的强度和模量是递增的,而冲击强度是递减的.     

Experimental investigation and numerical simulation of granite powder filled polymer composites for wind turbine blade: A comparative analysis

This paper describes the mechanical, thermo‐mechanical, and thermal behavior of unfilled E‐glass fiber (10–50 wt%) reinforced polymer (GFRP) composites and granite powder filled (8–24 wt%) GFRP composite in different weight percentages, respectively. The void fraction of unfilled glass epoxy composite is decreased from 7.71% to 3.17% with the increase in fiber loading from 10 to 50 wt%. However, void fraction for granite powder filled GFRP composites show reverse in trend. The granite powder addition in glass‐epoxy composites show significant improvement in hardness (37–47 Hv), impact strength (31.56–37.2 kJ/m²), and stress intensity factor (by 14.29% for crack length of 5 mm) of the composites. The thermo‐mechanical analyses also show strong correlation with the mechanical performance of the composites. The minimum difference of 0.17 GPa in storage and flexural moduli are observed for unfilled 20 wt% glass epoxy composite; whereas, maximum difference of 0.71 GPa is recorded for unfilled 50 wt% glass epoxy composite. Moreover, the numerical and experimentally measured thermal conductivity of unfilled and granite powder filled epoxy composites are within the lower and upper bound values. Hence, a successful attempt is presented for mechanical analysis of full scale model by finite element analysis. The results show that finite element analysis predicted reasonably actual stress value and tip deflection of wind turbine blade. POLYM. COMPOS., 38:1335–1352, 2017. © 2015 Society of Plastics Engineers     

A lexicographic multiobjective genetic algorithm for optimization of mechanical properties of crab carapace impregnated coir–polyester composites

This work is aimed at determining the possibility of using crab carapace materials as reinforcing fillers in the coir fiber reinforced polyester composite. The sample preparation was carried out with three levels of fiber length (10, 30, & 50 mm), fiber weight content (10, 25, and 40%), and additive weight content (2, 4, and 6%). The composite sheets were prepared by impregnating crab carapace additive obtained from crab shell with coir fiber reinforced polyester composite using compression molding machine. The tensile, flexural, and impact strength of the composites were determined as per ASTM standards and regression models were developed to predict the mechanical behaviors of the composites using statistical technique. The fabrication parameters considered in this investigation has significantly contributed toward the mechanical properties of the composites. The developed regression models were optimized to obtain the maximum values of mechanical properties using single objective genetic algorithm and multiobjective lexicographic method in this investigation. POLYM. COMPOS., 37:844–853, 2016. © 2014 Society of Plastics Engineers     

Characteristics of murta bast fiber reinforced epoxy composites

The growing global concern over environment protection has led to the application of natural fiber reinforced polymer composites as alternative materials in manufacturing sectors. Various natural fibers are therefore being explored for reinforcement of polymer matrices. In the present work, murta bast fibers of varying length and weight percent are mixed randomly with the epoxy matrix and the composites are prepared from these mixtures by using the hand lay‐up method. The composites are characterized on the basis of density, thermal gravimetric analysis, infrared spectroscopy, scanning electron microscopy, tensile strength, flexural strength, compressive strength, impact strength, and Rockwell hardness studies. Tensile, flexural, and compressive moduli of the composites are also determined. The tensile strength of the composite was analyzed in the light of the different analytical models. Composites containing 30 weight % fibers of length 25 or 35 mm have the optimum mechanical properties. Murta bast fiber has the characteristics to become a good natural material for reinforcement. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44142.     

A comparative analysis of woven jute/glass hybrid polymer composite with and without reinforcing of fly ash particles

The objective of this research article is to compare the mechanical and tribological properties of jute‐glass‐fiber‐reinforced epoxy (J‐G‐E) hybrid composites with and without fly ash particulate filler. A dry hand lay‐up technique is used to fabricate all the laminates. The properties including flexural strength, tensile strength, flexural modulus, and erosion behavior of all the composites are evaluated as per American Society for Testing and Materials (ASTM) standards. The fly ash particulate‐filled hybrid composite shows a better mechanical and tribological property. The maximum flexural strength and flexural modulus are obtained for GJGJ+ 5 wt% fly ash filler epoxy composites. Whereas the maximum tensile strength is obtained for GJJG+ 10 wt% fly ash filler epoxy composites. Scanning Electron Microscopy (SEM) analysis also has been carried out to categorize mechanical and tribological behavior of composites. POLYM. COMPOS. 37:658–665, 2016. © 2014 Society of Plastics Engineers     

The influence of fiber surface modification on the mechanical properties of coir‐polyester composites

Coir, an important lignocellulosic fiber, can be incorporated in polymers like unsaturated polyester in different ways for achieving desired properties and texture. But its high level of moisture absorption, poor wettability and insufficient adhesion between untreated fiber and the polymer matrix lead to debonding with age. In order to improve the above qualities, adequate surface modification is required. In our present work, fiber surface modification was effected through dewaxing, alkali (5%) treatment, aqueous graft copolymerization of methyl methacrylate (MMA) onto 5% alkali treated coir for different extents using CuSO₄ – NaIO₄ combination as an initiator system and cyanoexhylation with a view to improve the mechanical performance of coir‐polyester composites. Mechanical properties like tensile strength (PS), flexural strength (ES) and impact strength (IS) of the composites as a function of fiber loading and fiber surface modification have been evaluated. Composites containing z5 wt% of fiber (untreated) improved tensile and flexural strength by 30% and 27% respectively in comparison to neat polyester. The work of fracture (impact strength) of the composite with 25 wt% fiber content was found to be 967 J/m. The elongation at break of the composites exhibits an increase with the introduction of fiber, All types of surface modification result In improved mechanical properties of the composites. Significant improvement in mechanical strength was also observed for composites prepared from 5% PMMA grafted fiber.     

Preparation and mechanical characterization of chicken feather/PLA composites

Green composites, a bio‐based polymer matrix is reinforced by natural fibers, are special class of bio‐composites. Interest about green composites is continuously growing because they are environment‐friendly. This study describes the preparation and mechanical characterization of green composites using polylactic acid (PLA) matrix including chicken feather fiber (CFF) as reinforcement. Extrusion and an injection molding process were used to prepare CFF/PLA composites at a controlled temperature range. CFF/PLA composites with fiber mass content of 2%, 5%, and 10% were manufactured. The effects of fiber concentration and fiber length on mechanical properties of CFF/PLA composites have been studied. Mechanical properties of composites were investigated by tensile, compression, bending, hardness, and Izod impact testing. The results of experiments indicated that Young's modulus, compressive strength, flexural modulus, and hardness of the PLA reinforced CFF composites are higher but tensile strength, elongation at break, bending strength and impact strength of them are lower than pure PLA. The results indicate that these types of composites can be used for various applications. POLYM. COMPOS., 38:837–845, 2017. © 2015 Society of Plastics Engineers     

Investigation on mechanical and thermo‐mechanical properties of granite powder filled treated jute fiber reinforced epoxy composite

In the present study, two sets of jute epoxy composites are fabricated by varying first fiber loading from 10 to 50 wt% at an interval of 10 wt% and then granite powder incorporated from 0 to 24 wt% in an interval of 8 wt% in the composites. The initial study is to prepare polymeric composites for wind turbine blade application and study the following physical to thermo‐mechanical properties including fracture toughness of the composites. The void content of the unfilled composites show in decreasing order (from 6.37 to 3.07%) with the increasing in fiber loading which satisfied well with the increasing in tensile strength from 28.33 to 34.2 MPa and flexural strength from 44.2 to 97.8 MPa, respectively. As far as particulate filled composites the void content shows reverse in trend (from 2.99% to 9.68%) with the increasing in filler content and which justifies the mechanical properties i.e tensile strength decreases from 33.72 to 32.27 MPa and similarly in case of flexural strength also. Whereas, hardness shows a unique behavior both in fiber reinforced and particulate filled composites in an increasing order from 29 to 44 Hv, respectively. Fracture toughness is observed to be constant for all considered crack lengths however, its value significantly improved with both type of reinforcement. The dynamic mechanical analysis shows positive effect of both the reinforcement for mechanical performance under cyclic stresses. Finally, Cole–Cole plot is drawn from the dynamic mechanical analysis results to verify the homogeneity of the composites. POLYM. COMPOS., 38:736–748, 2017. © 2015 Society of Plastics Engineers     

Short glass fiber reinforced ABS and ABS/PA6 composites: Processing and characterization

In this study acrylonitrile‐butadiene‐styrene (ABS) terpolymer was reinforced with 3‐aminopropyltrimethoxysilane (APS)‐treated short glass fibers (SGFs). The effects of SGF concentration and extrusion process conditions, such as the screw speed and barrel temperature profile, on the mechanical properties of the composites were examined. Increasing the SGF concentration in the ABS matrix from 10 wt% to 30 wt% resulted in improved tensile strength, tensile modulus and flexural modulus, but drastically lowered the strain‐at‐break and the impact strength. The average fiber length decreased when the concentration of glass fibers increased. The increase in screw speed decreased the average fiber length, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength were affected negatively and the strain‐at‐break was affected positively. The increase in extrusion temperature decreased the fiber length degradation, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength increased. At higher temperatures the ABS matrix degraded and the mechanical strength of the composites decreased. To obtain a strong interaction at the interface, polyamide‐6 (PA6) at varying concentrations was introduced into the ABS/30 wt% SGF composite. The incorporation and increasing amount of PA6 in the composites broadened the fiber length distribution (FLD) owing to the low melt viscosity of PA6. Tensile strength, tensile modulus, flexural modulus, and impact strength values increased with an increase in the PA6 content of the ABS/PA6/SGF systems due to the improved adhesion at the interface, which was confirmed by the ratio of tensile strength to flexural strength as an adhesion parameter. These results were also supported by scanning electron micrographs of the ABS/PA6/SGF composites, which exhibited an improved adhesion between the SGFs and the ABS/PA6 matrix. POLYM. COMPOS. 26:745–755, 2005. © 2005 Society of Plastics Engineers     

Novel,low-cost jute-polyester composites. Part 1: Processing,mechanical properties,and SEM analysis

The development of high performance composites from a cheap natural fiber, jute, as reinforcement is particularly significant from an economic point of view. In this work, jute fiber-unsaturated polyester(GP) composites having appreciable mechanical properties were prepared by using solution impregnation and hot curing methods. Both unbleached (control) and bleached jute slivers with various percentages of fiber loadings were used to prepare the composites and were named JPH (C) i.e., Jute Polyester Hot Curing (control), and JPH (B) i.e., Jute Polyester Hot Curing (bleached), respectively. Mechanical properties such as tensile and flexural strain, toughness, and moduli of both the grades have been compared. Composites having 60 wt% of jute fiber yielded the best results. JPH (B) showed much better flexural properties than JPH (C), although the tensile properties of the latter were better. The inter-laminar shear strength (ILSS) of the JPH (B) was found to be higher than JPH (C). The nature of fiber-resin bonding was studied from scanning electron micrographs of the specimens subjected to tensile and flexural fracture. Dynamic mechanical properties were found to be very high, superior even to those of glass fiber reinforced composites. The flexural storage modulus was found to be 12.3 GPa at 30°C and to decrease slowly with temperature. The major finding in this work is the attainment of high mechanical properties of composite specimens with 60 wt %fiber loading. On a weight and cost basis, bleached jute fibres were found to be better reinforcements than other fibers with usual surface modification by coating or grafting processes.     

Physical and mechanical behavior of unidirectional banana/jute fiber reinforced epoxy based hybrid composites

During the last few years, natural fiber composites are replacing synthetic fiber composites for practical applications due to their advantages like low density, light weight, low cost, biodegradability and high specific mechanical properties. In this connection, the present investigation deals with the fabrication and mechanical properties of unidirectional banana/jute hybrid fiber reinforced composites and compares with the single natural fiber reinforced composites. The physical and mechanical properties of the natural fiber composites were obtained by testing the composite for density, tensile, flexural, inter‐laminar shear, impact, and hardness properties. The composite specimens with different weight percentages of fibers were fabricated by using hand lay‐up technique and testing were carried out as per ASTM standards. Incorporation of both the fibers into epoxy matrix resulted in an increase in mechanical properties up to 30 wt% of fiber loading. It is found that the hybrid composite give encouraging results when compared with the individual fiber composites. The morphologies of the composites are also studied by scanning electron microscope. POLYM. COMPOS., 38:1396–1403, 2017. © 2015 Society of Plastics Engineers     

Isolation and characterization of betel nut leaf fiber: Its potential application in making composites

Betel nut leaf fiber (BNLF) is a new finding as cellulosic filler for polymer composites. Its main constituents are 75% α‐cellulose, 12% hemicelluloses, 10% lignin, and 3% others matter, viscosity average molecular weight 132,000 and degree of crystallinity 70%. In the present work, BNLF reinforced polypropylene (PP) composites were prepared using heat press molding method. 5–20 wt% short length fiber is taken for getting benefits of easy manufacturing and the fiber was chemically treated with NaOH, dicumyl peroxide (DCP), and maleic anhydride‐modified PP (MAPP) to promote the interfacial bond with PP. The extent of modification of fiber was assessed on the basis of morphology, bulk density, moisture absorption, thermal, and mechanical properties of untreated fiber, treated fiber, and their reinforcing PP composites. The tensile and flexural strength of composites increase with the increase of fiber loading up to 10 and 20 wt%, respectively. It was also observed that Young's modulus and flexural modulus increase with fiber loading. The thermal degradation behavior of resulting composites was investigated. Among the various treated fibers, MAPP‐treated fiber composite showed best interfacial interactions as well as mechanical and thermal properties. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Preparation and characterization of chemically modified Jute–Coir hybrid fiber reinforced epoxy novolac composites

In this study, the effects of fiber surface modification and hybrid fiber composition on the properties of the composites is presented. Jute fibers are cellulose rich (>65%) modified by alkali treatment, while the lignin rich (>40%) coconut coir fibers consist in creating quinones by oxidation with sodium chlorite in the lignin portions of fiber and react them with furfuryl alcohol (FA) to create a coating around the fiber more compatible with the epoxy resins used to prepare polymer composites. The maximum improvement on the properties was achieved for the hybrid composite containing the jute–coir content of 50 : 50. The tensile and flexural strength are recorded as 25 and 63 MPa at modified coir fiber content of 50 vol %, respectively, which are 78% and 61% higher than those obtained for unmodified fiber reinforced composites, i.e., tensile and flexural strength are 14 and 39 MPa, respectively. The reinforcement of the modified fiber was significantly enhanced the thermal stability of the composites. SEM features correlated satisfactorily with the mechanical properties of modified fiber reinforced hybrid composites. SEM analysis and water absorption measurements have confirmed the FA-grafting and shown a better compatibility at the interface between chemically modified fiber bundles and epoxy novolac resin. Hailwood–Horrobin model was used to predict the moisture sorption behavior of the hybrid composite systems. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

相容剂对长玻纤增强尼龙66树脂力学性能和流变行为的影响

采用自行研制的熔体浸渍包覆长玻纤装置,制备了长玻纤增强尼龙66(LGF-PA66)复合材料.研究了相容剂乙烯-辛烯共聚物接枝马来酸酐(POE-g-MAH)、三元乙丙橡胶接枝马来酸酐(EPDM-g-MAH)对LGF-PA66力学性能和流学行为的影响.结果发现:当相容剂质量分数为2.5%时,复合材料的拉伸强度最大,缺口冲击强度在相容剂质量分数为0%～10.0%范围内近似线性的增加,不同相容剂对力学性能的影响相似.运用了拉伸强度模型和缺口冲击强度模型对实验结果进行了解释.相容剂用量的增加导致了平衡扭矩线性的提高,但对实际加工并没有带来太大的影响.     

Experimental Investigation of Mechanical and Morphological Properties of Flax-Glass Fiber Reinforced Hybrid Composite using Finite Element Analysis

The use of cellulosic fibers as reinforcing materials in polymer composites has gained popularity due to an increasing trend for developing sustainable materials. In the present experimental study, flax and glass fiber reinforced partially eco-friendly hybrid composites are fabricated with two different fiber orientations of 0° and 90°. The mechanical properties of these composites such as tensile, flexural and impact strengths have been evaluated. From the experiments, it has been observed that the composites with the 0° fiber orientation can hold the maximum tensile strength of 82.71 MPa, flexural strength of 143.99 MPa, and impact strength of 4 kJ/m². Whereas the composites with 90° fiber orientation can withstand the maximum tensile strength of 75.64 MPa, flexural strength of 134.86 MPa, and impact strength of 3.99 kJ/m². Morphological analysis is carried out to analyze fiber matrix interfaces and the structure of the fractured surfaces by using scanning electron microscopy (SEM). The finite element analysis (FEA) has been carried out to predict the resulting important mechanical properties by using ANSYS 12.0. From the results it is found that the experimental results are very close to the results predicted from FEA model values. It is suggested that these hybrid composites can be used as alternate materials for pure synthetic fiber reinforced polymer composite materials.     

Fabrication and characterization of functionally graded nanoclay/glass fiber/epoxy hybrid nanocomposite laminates

In this work, hardness, tensile, impact, bearing strength and water absorption tests were performed to study the mechanical properties of stepwise graded and non-graded hybrid nanocomposites. Three different stepwise graded nanocomposites and one non-graded (homogeneous) nanocomposite with the same geometry and total nanoclay content of 10 wt% were designed and prepared. Moreover, one neat glass fiber laminate was manufactured. The results of the tests indicated that addition of the graded and non-graded nanoclay improves hardness over neat glass fiber reinforcement. The maximum increase in hardness of about 53% over neat specimen is obtained for specimens that have the highest weight percentage (2 wt%) of the clay nanoparticles on its surface (S-specimen and the side of F-specimen that reinforced with 2 wt% nanoclay). The gradation process results in an increase in hardness of about 11% compared with non-graded (homogeneous) specimen. In addition, an improvement of 11.9% in strain-to-failure is achieved with specimen having greatest amount of nanoclay in the middle over neat glass fiber/epoxy composite. The other nanoclay-filled glass fiber composites have strain-to-failure close to neat glass fiber/epoxy. The addition of nanoclay reinforcement has insignificant effect on ultimate tensile strength, tensile modulus, water absorption, bearing strength and impact strength compared with neat glass fiber/epoxy.     

Influence of fly ash cenospheres on performance of coir fiber‐reinforced recycled high‐density polyethylene biocomposites

Recycled high‐density polyethylene (RHDPE)/coir fiber (CF)‐reinforced biocomposites were fabricated using melt blending technique in a twin‐screw extruder and the test specimens were prepared in an automatic injection molding machine. Variation in mechanical properties, crystallization behavior, water absorption, and thermal stability with the addition of fly ash cenospheres (FACS) in RHDPE/CF composites were investigated. It was observed that the tensile modulus, flexural strength, flexural modulus, and hardness properties of RHDPE increase with an increase in fiber loading from 10 to 30 wt %. Composites prepared using 30 wt % CF and 1 wt % MA‐g‐HDPE exhibited optimum mechanical performance with an increase in tensile modulus to 217%, flexural strength to 30%, flexural modulus to 97%, and hardness to 27% when compared with the RHDPE matrix. Addition of FACS results in a significant increase in the flexural modulus and hardness of the RHDPE/CF composites. Dynamic mechanical analysis tests of the RHDPE/CF/FACS biocomposites in presence of MA‐g‐HDPE revealed an increase in storage (E′) and loss (E″) modulus with reduction in damping factor (tan δ), confirming a strong influence between the fiber/FACS and MA‐g‐HDPE in the RHDPE matrix. Differential scanning calorimetry, thermogravimetric analysis thermograms also showed improved thermal properties in the composites when compared with RHDPE matrix. The main motivation of this study was to prepare a value added and low‐cost composite material with optimum properties from consumer and industrial wastes as matrix and filler. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42237.     

Novel eco‐friendly biodegradable coir‐polyester amide biocomposites: Fabrication and properties evaluation

Biocomposites are prepared from a cheap, renewable natural fiber, coir (coconut fiber) as reinforcement with a biodegradable polyester amide (BAK 1095) matrix. In order to have better fiber‐matrix interaction the fibers are surface modified through alkali treatment, cyanoethylation, bleaching and vinyl grafting. The effects of different fiber surface treatments and fiber amounts on the performance of resulting bio‐composites are investigated. Among all modifications, cyanoethylated coir‐BAK composites show better tensile strength (35.50 MPa) whereas 7% methyl methacrylate grafted coir‐BAK composites show significant improvement in flexural strength (87.36 MPa). The remarkable achievement of the present investigation is that a low strength coir fiber, through optimal surface modifications, on reinforcement with BAK show an encouraging level of mechanical properties. Moreover, the elongation at break of BAK polymer is considerably reduced by the incorporation of coir fibers from nearly 400% (percent elongation of pure BAK) to 16‐24% (coir‐BAK biocomposites). SEM investigations show that surface modifications improve the fiber‐matrix adhesion. From biodegradation studies we find that after 52 days of soil burial, alkali treated and bleached coir‐BAK composites show significant weight loss. More than 70% decrease in flexural strength is observed for alkali treated coir‐BAK composites after 35 days of soil burial. The loss of weight and the decrease of flexural strength of degraded composites are more or less directly related.     

Effect of screw design on fiber damage in extrusion compounding and composite properties

The mechanism of fiber length degradation during twin screw extrusion compounding and methods to reduce it through process and machine design are extremely important in discontinuous fiber reinforced composites. Fiber damage along the screw and the extruder die are determined for three screw designs with different mixing sections. The pellet quality, wet-out, and fiber dispersion in the extruded strands are compared. The fiber orientation distributions in the screw are determined to identify regions of higher fiber interaction. The fiber damage during subsequent injection molding has also been determined. The tensile, flexural, and impact properties of the tensile bars are compared. It is found that the residence time, fill-up, and the intesity of mixing during extrusion compounding have a predominant effect on fiber length degradation. The screw designs were seen to have a greater effect on the fiber damage in the 40 wt% glass-filled polymer than the 30 wt% glass-filled polymer. However, the mechanical properties of the 30 wt% glass-filled polymer showed an increasing trend compared to the 40 wt% glass filled polymer. A screw design that provides a balance of the fiber length, wet-out, and fiber dispersion was noted to give consistent mechanical properties.