Moisture absorption behavior and its effect on the mechanical properties of jute‐reinforced epoxy composite

With the growing economic competition and the ecological pressure, the past decade has seen a renewed interest in developing more efficient reinforcements along with overall production cost. In some industrial applications, natural fiber composites fulfill small requirements for making the product to be economical due to their several advantages such as low density, greater deformability, lower abrasiveness, and cost. In the present work, composites are prepared with epoxy as a resin and jute as reinforcement by hand lay‐up technique. Moisture absorption characteristics when exposed to saline water, mineral water, sub‐zero temperature conditions, and also effect of moisture on depreciation in strength (tensile strength and flexural strength) and of different layers (one, two, three layers) of composites are studied experimentally. Specimen preparation and testing were carried out as per ASTM standards. It is found that the jute‐reinforced epoxy composite give encouraging results when compared with the pure epoxy composites. The less effect in strength is observed after exposure to mineral water and sub‐zero temperature condition. The morphologies of the composites are also studied by scanning electron microscope. POLYM. COMPOS., 38:516–522, 2017. © 2015 Society of Plastics Engineers     

Effects of processing conditions and copolymer molecular weight on the mechanical properties and morphology of compatibilized polymer blends

The mechanical properties and morphology of melt mixed polystyrene (PS)/polyethylene (PE) blends that were modified by the addition of up to 16% of a semicrystalline PS-b-hPB (hydrogenated polybutadiene) diblock copolymer with varying molecular weight are reported. As a result of the blocks of the copolymer penetrating the corresponding homopolymers, these diblock copolymers are capable of reinforcing the PS/PE interface significantly. This increase in interfacial strength between the immiscible blend components does not necessarily result in an improvement in the mechanical properties of the blends as measured by Izod or tensile tests. This may be because the effect of the copolymers on the rheological properties of the blends during processing outweighs their emulsifying/reinforcing effects. If found to be universally true for polymer blends, these results suggest that the relationship between the effects of copolymers on interfacial strength, their emulsifying effects, and the mechanical properties of copolymer modified blends are not as simple as suggested by many statements found in the literature.     

The effect of chemical treatment of wood and polymer characteristics on the properties of wood–polymer composites

The physical-mechanical properties and the microscopic structure of caixeta (Chrysophyllum viride) and slash pine (Pinus elliottii) impregnated with polystyrene (PS) were investigated. The influences of a pretreatment with hydrogen peroxide (H₂O₂) solutions utilized in the production of the wood–polymer composites (WPC) and the characteristics of polystyrene formed in situ on the properties of WPC were analyzed. The incorporation of polystyrene improved the compression and static bending properties of slash pine and caixeta. The micrographies confirmed that there were distinct but continuous phases of polymer and wood cell wall which granted the composites a better physical-mechanical behavior. The sensibilizing treatment with dilute hydrogen peroxide solution led to an increase in the viscosity average molecular weight (M _v) of polystyrene, and to the graft polymerization of the monomer, which, in turn, enhanced the stress properties of caixeta–polystyrene composites. Concentrated H₂O₂ solutions degraded caixeta wood, decreasing its tensile properties. Lower initiator concentration favoured higher molecular weight of polystyrene formed in pine wood. A fivefold increase in M _v of PS, however, had little effect on the compression properties of pine–polystyrene composites.     

Effects of processing conditions on the fiber length distribution and mechanical properties of glass fiber reinforced nylon‐6

The effects of processing conditions on fiber length degradation were investigated in order to produce composites with higher performance. Nylon‐6 was compounded with glass fibers in a twin‐screw extruder for various combinations of screw speed and feed rate. Collected samples were injection molded and Izod impact and tensile tests were performed in order to observe the effect of fiber length on the mechanical properties. Also, by using the extruded and injection molded smaples, fiber length distribution curves were obtained for all the experimental runs. Results show that when the shear rate is increased through the alteration of the screw speed and/or the feed rate, the average fiber length decreases. Impact strength, tensile modulus and tensile strength increase, whereas elongation at break decreases with the average fiber length.     

Study on the preparation and mechanical properties of injection‐moulded wood‐based plastics

The objectives of this study were to prepare injection‐moulded wood‐based plastics and to characterize their mechanical properties. Injection‐moulded wood‐based plastics with satisfactory flexural (65.7 MPa) and tensile strengths (30.1 MPa) were successfully obtained through a simple reaction of mulberry branch meal with phthalic anhydride (PA) in 1‐methylimidazole under mild condition. The X‐ ray diffraction results indicated complete disruption of the crystallinity of cellulose because the pattern obtained for esterified fiber was almost a straight line without any peaks. The peaks in the Fourier transform infrared spectroscopy spectra (1738 and 748 cm^?1) and NMR spectra (173.3 and 133.5 ppm) indicated the attachment of 0‐carboxybenzoyl groups onto the wood fibers via ester bonds. The differential scanning calorimetry curves showed that the glass transition temperature decreased with increasing weight percentage gain (WPG). The derivative thermogravimetric analysis curves indicated that esterified wood fiber was less thermally stable than the untreated fiber and that the component tends to be homogeneous with increasing WPG. Scanning electron microscope revealed that the fractured surfaces of most samples were smooth and uniform but that high temperature and less PA dosage could lead to the appearance of holes and cracks. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41376.     

The fracture properties of a fiber metal laminate based on a self‐reinforced thermoplastic composite material

The present research program has studied the fracture properties of a Fiber‐Metal Laminate (FML) system constituted by aluminum alloy and a high‐impact self‐reinforced composite material. Here, the self‐reinforced composite system consists of a polypropylene matrix reinforced with polypropylene fibers. Initial testing has shown that a though adhesion can be achieved between the aluminum layers and the composite material by incorporating a thermoplastic adhesive interlayer at the common interface. The adhesion at the metal–composite interface has been studied under a wide range of strain rate conditions using a Single Cantilever Beam test geometry, and it has been shown that the interfacial fracture toughness is loading rate sensitive. Interlaminar delamination tests of the plain composite have also been studied and it was shown that their fracture toughness is also loading rate sensitive. Additional tensile tests have shown that the tensile strength and moduli of the FMLs are linearly influenced by the volume fraction of their constituent materials as well as are successfully predicted using a simple rule of mixture. Low velocity impact tests have also shown that the FMLs based on a self‐reinforced polypropylene composite yielded specific perforation energies well above the 30 J m²/kg. It was also shown that by increasing the number of metal and composite plies in the FMLs, resulted in hybrid structures capable of absorbing higher specific low velocity impact energies. POLYM. COMPOS., 35:427–434, 2014. © 2013 Society of Plastics Engineers     

The effect of morphology on the corrosion inhibition and mechanical properties of hybrid polymer coatings

The durability and mechanical properties of epoxy ester coatings and films has been improved by blending with rigid aromatic polyurea (PU). The interaction of PU and epoxy ester was enhanced by coupling the polymers with polymethylhydrosiloxane. The reactions between various entities are analyzed by Fourier transform infrared spectroscopy and the change in physical and mechanical properties are studied by a dynamic mechanical analyzer. The corrosion resistance of the hybrid coatings was measured by direct current polarization method, direct current polarization (DCP). The addition of polymethylhydrosiloxane enhances the corrosion properties in the hybrid coatings. The surface morphology was analyzed by scanning electron microscopy. The glass transition temperature of the films increases with increasing PU concentration and a wide glass rubber transition range for hybrid coatings was achieved which confirms the higher impact strength of the hybrid coatings and films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Crystallinity morphology and dynamic mechanical characteristics of PBT polymer and glass fiber‐reinforced composites

The crystalline morphologies of PBT (poly butylene terephthalate) and its glass fiber reinforced composite systems were investigated in a thin‐film form by polarized optical microscopy and wide‐angle X‐ray diffraction. Three different types of PBT morphology were identified in the Maltese cross pattern: 45° cross pattern (usual type) by solvent crystallization, 90° cross pattern (unusual type) by melt crystallization at low crystallization temperature, and mixed type by melt crystallization at crystallization temperatures higher than 160°C. The glass fibers increased the number density of spherulites and decreased the size of crystallites acting as crystallization nucleation sites without exhibiting trans‐crystallinity at the vicinity of the glass fiber surfaces. Finally, the storage modulus was analyzed by using a dual‐phase continuity model describing the modulus by the power‐law sum of the amorphous‐ and crystalline‐phase moduli. The crystalline‐phase modulus was extracted out from the PBT polymer and composite systems containing different amount of crystallinity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 478–488, 2002     

The mechanical and fatigue properties of flowable crosslink thermoplastic polymer blends based on self‐catalysis of transesterification

A flowable crosslink polymer blend was successfully developed through a reactive compounding process. An epoxy captained ethylene acrylate copolymer and a carboxylic acid and zinc ion contained ethylene acrylic copolymer were employed to react in a twin screw extruder to form a partially crosslink polymer blend which was flowable at high temperature due to the rapid transesterification catalyzed by the zinc ion in the polymer. The developed crosslink polymer blend showed a significant improvement of the mechanical strength, thermal stability, and fatigue performance compared to the neat ethylene acrylic copolymer because of the strong chemical crosslink among polymer chains. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44964.     

Moisture absorption properties of wood‐fiber‐reinforced recycled polypropylene matrix composites

To reduce the moisture absorption of wood‐fiber‐reinforced recycled plastic composites (WRPCs), a coupling agent (KH550), methyl methacrylate (MMA), and maleic anhydride (MA) were used to modify the wood fibers. The surface‐treated wood fibers were mixed with recycled polypropylene and processing agents to fabricate the WRPCs. The mechanical properties and moisture absorption behavior of the WRPCs were determined. The results showed that the three surface treatment methods could effectively reduce the moisture absorption and thickness swelling of WRPCs. In Comparison to the properties of untreated wood‐fiber‐reinforced WRPCs, the moisture absorption ratio of WRPCs with wood fibers treated by MMA, KH550, and MA was reduced by 31.4%, 49.8%, and 38.2%, respectively, and the tensile strength was increased by 22.1%, 26.3%, and 4.2%, respectively. The impact toughness of the WRPCs was increased by 36.2% KH550 treatment and 19.2% for MMA treatment but was decreased by 4.2% for MA treatment. Coupling treatment of the wood fibers was the best way to reduce the moisture absorption of WRPCs, and this kind of WRPC possessed the best comprehensive properties. J. VINYL ADDIT. TECHNOL., 2010. © 2009 Society of Plastics Engineers     

Thermal and mechanical properties of polypropylene/wood‐flour composites

In this research, polypropylene/wood‐flour composites (WPCs) were blended with different contents of wood and/or maleated polypropylene (MAPP) and clay. We found that the addition of MAPP or clay in the formulation greatly improved the dispersion of the wood fibers in the composite; this suggested that MAPP or clay may have played the role of an adhesion promoter in the WPCs. The results obtained with clay indicate that it also acted as a flame retardant. The thermal tests carried out with the produced samples showed an increased crystallization temperature (T_c), crystallinity, and melting temperature (T_m) with wood loading. The increase of the two former parameters was explained by the incorporation of wood flour, which played the role of nucleating agent and induced the crystallization of the matrix polymer. On the other hand, the T_m increase was ascribed to the insulating properties of wood, which hindered the movement of heat conduction. The effects of UV irradiation on T_m and T_c were also examined. T_c increased with UV exposure time; this implied that UV degradation generated short chains with low molecular weight that could move easily in the bulk of the sample and, thus, catalyze early crystallization. The flexural strength and modulus increased with increasing wood‐flour content. In contrast, the impact strength and tensile strength and strain decreased with increasing wood‐flour content. All of these changes were related to the level of dispersion of the wood flour in the polymeric matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A novel low‐melting‐point alloy‐loaded polymer composite. I. Effect of processing temperature on the electrical properties and morphology

Sn–Pb alloy‐loaded polystyrene (PS) composites were processed by powder mixing and hot pressing. For the composites hot‐pressed at the temperatures below the melting point of the alloy, the resistivity dropped sharply if the alloy volume fraction reached 20 vol %. When the composites were processed at temperatures above the melting point, such phenomenon disappeared. According to the SEM and energy dispersive analysis X‐ray (EDAX) analyses, the size and dispersion of Sn–Pb alloy particles in composites changed when the hot‐pressing temperature reached the melting point of the alloy, which resulted in the different forms of resistivity–filler volume fraction curves. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1044–1050, 2000     

Effect of processing conditions on morphology and mechanical properties of compatibilized polypropylene nanocomposites

This work focuses on the influence of processing conditions on the nanocomposites structure, i.e. intercalated or exfoliated, and on the enhancement of mechanical properties of polypropylene (PP) nanocomposites. These nanocomposites were prepared using the melt intercalation technique in a co-rotating intermeshing twin screw extruder. In order to optimise processing conditions, both screw speed and barrel temperature profile were changed. The role of the compatibilizer (maleic anhydride grafted polypropylene) was also studied. The results obtained show that the barrel temperature is a very important parameter: using lower processing temperature, the apparent melt viscosity and, consequently, the shear stress are higher and, therefore, the exfoliation of the clay is promoted. Even using optimised processing conditions, exfoliation of clay can be achieved only when an high compatibility between polymer and clay exists: the PP nanocomposites containing maleic anhydride show an exfoliated structure and a sensible enhancement of mechanical properties while PP nanocomposites without compatibilizer show a structure mainly intercalated and a lower improvement of mechanical properties.     

The effect of surface treatments on the mechanical properties of basalt‐reinforced epoxy composites

Basalt fiber is an emerging alternative reinforcement to glass or carbon depending upon the application. An important contributing parameter to ultimate performance of any composite is the fiber–‐matrix interface, to which toughness and compressive strength are intimately related. To better understand this matrix fiber interaction in controlling properties, we compared different modification strategies and the impact upon the properties of composites. Strategies focussing upon mechanical interlocking through increased surface roughness and covalent chemical bonding using sol/get methods were explored. Combined methods were also used to explore synergistic behavior as well as the use of aliphatic triethylenetetramine (TETA) to react with any covalently attached epoxy groups. Results from single ply composites showed that when the properties were fiber or fiber/matrix dominated, the sol/gel or epoxy silane method gave the largest improvement in ultimate tensile strength increasing 66% and 27% for uni‐weave 0° and 45° laminas. The combined surface modification methods exhibited increases of 45% and 13% for the same laminas. When properties were matrix dominated, the combined strategies produced the highest improvements in ultimate tensile strength of about 55% compared with 37% for sol/gel modification. For 16‐ply plain weave laminates, epoxy silane surface treatments produced the greatest improvements in compressive and interlaminar shear strengths, increasing 52% and 21%, respectively. This correlated with fiber‐ and fiber/matrix‐dominated results from single ply laminas. The combined treatment using TETA however decreased shear and compressive strength by about 20%, while scanning electron microscopy (SEM) evaluation and dynamic mechanical thermal analysis (DMTA) attributed this to increased resin ductility and plasticization. © 2013 Society of Plastics Engineers     

Fabrication and mechanical properties of self‐reinforced polyester composites by double covered uncommingled yarn

Self‐reinforced poly(ethylene terephthalate) (srPET) composites composed of double covered uncommingled yarn that was prepared through cowrap spinning were hot pressed using a film stacking technique. The optimal consolidation temperature for manufacturing lamina was determined to be 240°C and resulting in the adequate impregnation and reinforcing structural integrity. The srPET laminates that had a plain structure exhibited the excellent tensile responses, whereas those with a twill weaving structure had the highest impact energy absorption. In the plain fabric, there were more interlace points and a higher crook degree of wrap and weft yarns in the periodic unit cell, resulting in more clamp force on the yarns at the interlace points during stretching and more elongation. The srPET composites prepared using basket‐weaving structural fabric broke apart and resulted in the lowest impact energy, which can be attributed to the larger gap between two interweaving points that creates a weak path. A strong influence from the weaving structure was observed for the α relaxation of the composites. T_α shifted to a higher temperature because the reinforcing of the fibers and the structural integrity was more effective. POLYM. COMPOS., 37:3331–3340, 2016. © 2015 Society of Plastics Engineers     

Influence of processing conditions and material compositions on the performance of formaldehyde‐free wood‐based composites

This study examined the differences between formaldehyde‐free wood composite panels made with maleated polyethylene (MAPE) and maleated polypropylene (MAPP) binding agents. Specifically, the study investigated the contrasts of (a) base resin type, PE vs. PP, (b) molecular weight/maleic anhydride content in MAPP binding agents, and (c) the manufacturing methods (reactive extrusion vs. hot press) on the physicomechanical properties of the composites. FTIR and XPS analyses of unmodified and modified wood particles after reactive extrusion with maleated polyolefins provided evidence of chemical bonding between the hydroxyl groups of wood particles and maleated polyolefins. Although extruding the particles before panel pressing gave better internal bond (IB) strength, superior bending properties were obtained through compression molding alone. MAPP‐based panels outperformed MAPE‐based panels in stiffness. Conversely, MAPE increased the IB strength of the panels compared with MAPP. Polymer base resin had no effect on modulus of rupture or screw holding capacity. Differences between the two maleated polypropylene compounds were not significant for any of the mechanical properties tested. Formaldehyde‐free wood composites manufactured in this study often outperformed standard requirements for conventional particleboard, regardless of material composition or manufacturing method used. POLYM. COMPOS., 27:599–607, 2006. © 2006 Society of Plastics Engineers     

The effect of hybridization on mechanical properties of woven kenaf fiber reinforced polyoxymethylene composite

The challenges of using natural fibers in polymer composites include high moisture uptake and poor interfacial bonding with thermoplastic matrix. In this study, the effect of hybridization was investigated to address the challenges of high moisture uptake and balanced mechanical properties in natural fiber reinforced polymer composites. Polyethylene terephthalate fiber (PET) was used in woven kenaf reinforced POM due to its hydrophobic characteristics. The results of tensile test showed that the tensile strength of the interwoven POM/kenaf/PET hybrid composite when tested along kenaf fiber direction, increased from 72 to 85 MPa due to increase in fiber content. Similarly, the tensile strength of the interwoven POM/kenaf/PET hybrid composite increased from 67 to 75 MPa. However, the flexural strength of the interwoven POM/kenaf/PET hybrid composite dropped from 160.1 to 104.9 MPa while that of woven POM/kenaf composite dropped from 191.4 to 90.3 MPa. The interwoven hybrid composite also showed significant improvement in impact strength compared to the woven POM/kenaf composite. The water absorption of the woven POM/kenaf composite dropped by approximately 30% due to hybridization with PET fiber. The results confirmed that hybridization with PET fiber significantly improved the tensile and impact properties of the woven composite and increased its resistance to moisture uptake. POLYM. COMPOS., 35:1900–1910, 2014. © 2014 Society of Plastics Engineers     

Gas turbine environment effect on morphology and mechanical properties of pultruded composite

The effect of gas turbine lubricant oil soaking, thermal cycling and their combination on morphology and tension and flexure properties of pultruded composite was studied. Two types of lubricant oils were used: Mil‐L‐7808 and Mil‐L‐23699. Composite samples were oil soaked for 720 h and microscopic analysis and mechanical tests were conducted. Samples were thermal cycled for 600 cycles (RT to 315°C) and measured tension and flexure properties. Samples were oil soaked, thermal cycled and then tested. Results of these three groups of environmentally aged samples were compared with non‐aged samples. The significance of aging effect is discussed in the article. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Development of semitransparent wood‐polymer composites

A new material has been developed consisting of pieces of wood embedded within a matrix of acrylic polymer, resulting in a transparent or semitransparent wood‐based product. This material presents quite appealing aesthetic features, thereby opening new possibilities for decorative applications. Because acrylic and methacrylic monomers are in the liquid state at room temperature, it is possible to introduce wood (in the current case, walnut wood) into a mixture of acrylic (hydroxypropyl acrylate) and/or methacrylic monomers (methyl methacrylate and 2‐hydroxyethyl methacrylate) along with a plasticizer (dioctyl phthalate) in the presence of a chemical initiator (benzoyl peroxide). A transparent polymeric matrix with dispersed wood is then obtained through bulk free‐radical polymerization. Introducing this reaction mixture along with pieces of wood into a mold results in a wood‐polymer composite. A 2^4?1 experimental fractional factorial design was implemented to study the importance of the composition of these materials on several relevant properties. The sheets produced were characterized by tensile testing, dynamic mechanical thermal analysis, thermal gravimetric analysis, and heat deflection temperature. The models obtained for predicting each property pointed to valuable insights regarding the influential constituents. In particular, our results suggested that monomers to be used in future applications of this material should be selected in terms of their cost and the desired flexibility for the final product, not in terms of their polarity. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Dynamic mechanical analysis of tropical wood–polymer composites

Wood–polymer composites (WPC) of Geronggang (GE; Cratoxylon arborescens), a light tropical hardwood, impregnated with methyl methacrylate (MMA) and styrene-co-acrylonitrile (3 : 2; STAN), were prepared by in situ polymerization using γ radiation or catalystheat treatment. The dynamic flexural storage modulus, E′, for oven-dried GE, moist GE, and GE–MMA and GE–STAN composites decreased with increasing temperature. The percentage decreases for GE with 10 and 16.5% moisture contents were 74.5 and 98.2%, respectively, which were higher than those for GE and GE composites, which ranged between 40 and 50%. The impregnated polymers were not as effective as water in acting as plasticizers, due to their nonpolar nature and much higher molecular weights. The α-transition peaks for moist GE and GE composites were more distinct and were shifted to lower temperatures than those for oven-dried GE. The values ranged between 75 and 150°C for moist GE and between 102 and 170°C for the GE composites. The α-transitions of the catalyst–heat-treated GE composites were lower than that of the radiation-induced counterparts. GE–STAN composites were also observed to have lower α-transition temperatures than those for GE–MMA for the respective treatment process, which seems to suggest that STAN interacted to a greater extent with cell wall components than did MMA.