Thermal and mechanical properties of functionalized mullite reinforced unsaturated polyester composites

This work studies the development of varying weight percentages (0.5, 1.0, and 1.5 wt%) of surface functionalized mullite reinforced unsaturated polyester (UP) composites and their thermal, dielectric, water absorption, and mechanical properties. The synthesized mullite was functionalized with vinyltriethoxysilane (VTES). The introduction of vinyl groups on the surface of mullite was confirmed by FT‐IR, TGA, and X‐ray diffraction (XRD) analyses. Varying weight percentages (0.5, 1.0 and 1.5 wt%) of vinyl functionalized mullite (VFM) were incorporated into UP resin with a benzoyl peroxide initiator to obtain composites. The resultant data obtained from thermal, mechanical, dielectric, and water absorption studies, indicate that incorporation of VFM, leads to a significant improvement in the thermo mechanical, dielectric, and moisture resistant properties of the UP composites, compared with those of neat UP matrices. The molecular dispersion of VFM fiber in reinforced UP matrix composites was confirmed by SEM analysis. POLYM. COMPOS., 35:1663–1670, 2014. © 2013 Society of Plastics Engineers     

Chemical treatment of wood fiber and its reinforced unsaturated polyester composites

In order to enhance the interfacial adhesion between wood fiber and an unsaturated polyester matrix (UPE), acrylic acid (acrylic acid)/poly(methyl methacrylate), and (acrylic acid)/silanization (AAS) were used to treat the wood fibers. The mechanical properties and the impact fracture surfaces of the prepared composites were measured and characterized, and the fracture mechanism of these kinds of composites was analyzed. The results showed that the AAS composites possessed the optimum comprehensive mechanical properties. When the weight fraction of wood fiber was 16%, the flexural strength and flexural modulus of the AAS composites were increased by 28.9 and 51.8%, respectively, compared to those of untreated composites. The highest tensile strength and lowest water absorption were also noted for AAS composites. These composites possessed the strongest interfacial adhesion between wood fiber and the UPE matrix. J. VINYL ADDIT. TECHNOL., 19:18–24, 2013. © 2013 Society of Plastics Engineers     

Bamboo fiber reinforced polypropylene composites and their mechanical,thermal, and morphological properties

Short bamboo fiber reinforced polypropylene composites were prepared by incorporation of various loadings of chemically modified bamboo fibers. Maleic anhydride grafted polypropylene (MA‐g‐PP) was used as compatibilizer to improve fiber–matrix adhesion. The effects of bamboo fiber loading and modification of the resin on the physical, mechanical, thermal, and morphological properties of the bamboo reinforced modified PP composites were studied. Scanning electron microscopy studies of the composites were carried out on the interface and fractured surfaces. Thermogravimetric analysis and IR spectroscopy were also carried out. At 50% volume fraction of the extracted bamboo fiber in the composites, considerable increase in mechanical properties like impact, flexural, tensile, and thermal behavior like heat deflection temperature were observed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of process parameters and composition on mechanical,thermal, and morphological properties of polypropylene/sawdust composites

Polypropylene/sawdust composites have been prepared according to a statistical experimental design, with varying sawdust and compatibilizer (maleic anhydride grafted PP) concentrations. To investigate process conditions, composites were first extruded in a twin screw extruder coupled to a Haake torque rheometer, without degassing, and then reextruded in a Werner Pfleiderer twin screw extruder, with two degassing zones. Process conditions were analyzed according to statistical techniques. Effect of the variables on mechanical properties was assessed through flexural modulus, tensile strength, and percent elongation at break and morphology was assessed by scanning electron microscopy. Comparison between the extruded and reextruded compounds indicated the need to reduce moisture, prior to and during processing, as well as the need of effective mixing of the compounds. Sawdust concentration showed to be the variable which affected most all properties assessed. Increase in sawdust concentration resulted in increased composite stiffness. The presence of the compatibilizer caused a slight increase in tensile strength and reduction in percent elongation at break, indicating improved adhesion at the PP/sawdust interface. The reprocessed compounds were also analyzed by differential scanning calorimetry. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Structural,mechanical, thermal,and electrical properties of carbon black reinforced polyester resin composites

Carbon black (CB) reinforced polyester resin (PR) composites (CPC) have been fabricated from mechanical mixtures of liquid PR and CB powder having 0–50 wt% CB contents and cured with 1% of methyl ethyl ketone peroxide at room temperature under a pressure of 50 MPa. The samples have been examined by the Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD) technique, scanning electron microscopy (SEM), mechanical test, micromechanical test, differential thermal analysis (DTA), and thermogravimetric analysis (TGA) and electrical test. FTIR spectra confirm the physical and chemical bond formations between CB and PR. XRD shows a very partial crystalline structure in cured PR and hexagonal structure in CB particles. SEM exhibits a clear dispersion of CB particles in PR matrix at lower loading and aggregates at higher loading. With the increase of fillers, while the tensile and flexural strengths of CPCs decrease, the Young's and tangent modulii increase by 80 and 100%, respectively. These increments are found consistent with the theoretical values. The degree of physical crosslinking between CB and PR as well as the aspect ratio of CB in CPCs are found to increase with the increase of filler. A remarkable increase in microhardness of about 61% at 50 wt% CB content is observed. The TGA represents that the thermal degradation temperature for pure PR is 373°C and that for CPC is 393°C. The dielectric constant of CPCs decreases with increasing frequency, whereas the ac‐ and dc‐ conductivities of CPC are found to increase with CB content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40421.     

Mechanical,thermal, and morphological properties of bismaleimide/unsaturated polyester copolymers

An unsaturated polyester (UP) resin was modified by the addition of a thermosetting bismaleimide (BMD) as a second coreactive monomer. The copolymers were characterized in terms of mechanical, thermal, and morphological properties by tensile, bend, and impact testing; thermogravimetric analysis; heat deforming temperature analysis; dynamic mechanical analysis; and scanning electron microscopy. In addition, Fourier transform infrared spectroscopy of modified resin indicated that crosslinking networks were formed between BMD and UP. The properties of the modified resins were compared with those of unmodified resins. The results indicate that the addition of BMD not only improved the thermal decomposition temperature and heat deforming temperature but also caused small changes in the mechanical properties. The effect of the construct of BMD and the reactions among BMD, UP, and styrene were analyzed. The results show that BMD has great potential to improve the properties of UP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 593–598, 2006     

Dynamic mechanical,mechanical and morphological properties of reactive thermotropic liquid crystalline polymer/unsaturated polyester/glass fibre hybrid composites

Abstract

Unsaturated polyester (UP) reinforced with self-synthesised reactive thermotropic liquid crystalline polymer (TLCP)–methacryloyl copolymer (LCMC) and glass fibre (GF), the hybrid composites of UP/GF/LCMC were prepared by moulding technology. The dynamic mechanical analysis indicated that storage modulus and glass transition temperature (T _g) of hybrid composites increased significantly because of the addition of LCMC. The effect of LCMC content on the mechanical properties of LCMC/UP/GF hybrid composites such as impact strength, specific strength and modulus and load–displacement relationship were also investigated through static mechanical tests. The mechanical properties of hybrid composites increased significantly because of the addition of LCMC. The crystal behaviour analysis of LCMC/UP blend was investigated by X-ray diffraction and polarising optical microscopy. The results showed that the crystal phase and texture structure of LCMC still existed in the blends after blending with UP. The morphology of fracture surfaces of hybrid composites containing different TLCP contents was observed by scanning electron microscopy. The present paper discussed the mechanism for the improvement of dynamic mechanical and mechanical properties.     

Studies on thermal,mechanical, morphological,and viscoelastic properties of polybenzimidazole fiber reinforced high density polyethylene composites

High density polyethylene (HDPE) and polybenzimidazole fiber (PBI) composites were prepared by melt blending in a twin screw extruder. The thermomechanical properties of PBI fiber reinforced HDPE composite samples (1%, 4%, and 8%) of fiber lengths 3 mm and 6 mm were investigated using differential scanning calorimeter (DSC), universal testing machine, rheometer, and scanning electron microscopy (SEM). The effects of fiber content and fiber lengths on the thermomechanical properties of the HDPE‐PBI composites were studied. The DSC analysis showed a decrease in crystallinity of HDPE‐PBI composites with an increase of fiber loading. SEM images revealed homogeneous distribution of the fibers in the polymer matrix. The thermal behavior of the composites was evaluated from thermogravimetric analysis and the thermal stability was found to increase with the addition of fibers. The evidence of homogeneous distribution was verified by the considerably high values of tensile strength and flexural strength. In the rheology study, the complex viscosities of HDPE‐PBI composites were higher than the HDPE matrix and increased with the increasing of PBI fiber loading. POLYM. COMPOS., 5–13, 2016. © 2014 Society of Plastics Engineers     

Preparation of porous polyester composites via emulsion templating: Investigation of the morphological,mechanical, and thermal properties

Open porous polyester composites were prepared by the crosslinking of unsaturated polyester resin and divinylbenzene in water‐in‐oil concentrated emulsion templates with the presence of a conventional surface modified montmorillonite nanoclay. Medium and high internal phase emulsions with either 55 or 80 wt% of internal phase were used as templates. The effect of monomer composition, emulsifier concentration, and internal phase amount on the emulsion stability and the morphology of the resulting porous composites were investigated. Moreover, the morphological properties of the resulting composites were determined depending on the amount of nanoclay loading. It was found that the morphological features, namely surface area and cell diameter, were altered dramatically with the amount of nanoclay loading. An important part of the research was focused on the variation of mechanical and thermal properties with the incorporation of nanoclay particles. The mechanical properties were improved both with the nanoclay incorporation and the use of medium internal phase emulsions. However, the used nanoclay did not have a significant effect on the thermal stability of the resulting composites. POLYM. COMPOS., 37:1531–1538, 2016. © 2014 Society of Plastics Engineers     

Effect of the delignification of wood fibers on the mechanical properties of wood fiber–polypropylene composites

The effect of the delignification of hornbeam fibers on the mechanical properties of wood fiber–polypropylene (PP) composites was studied. Original fibers and delignified fibers at three levels of delignification were mixed with PP at a weight ratio of 40:60 in an internal mixer. Maleic anhydride (0.5 wt %) as the coupling agent and dicumyl peroxide (0.1 wt %) as the initiator were applied. The produced composites were then hot‐pressed, and specimens for physical and mechanical testing were prepared. The results of the properties of the composite materials indicate that delignified fibers showed better performance in the enhancement of tensile strength and tensile modulus, whereas the hardness of the composites was unaffected by delignification. Delignified fibers also exhibited better water absorption resistance. Notched impact strength was higher for delignified fiber composites, but it was reduced at higher delignification levels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4759–4763, 2006     

Effect of wood sawdust content on rheological and structural changes,and thermo‐mechanical properties of PVC/sawdust composites

The use of untreated sawdust as a filler in poly(vinyl chloride) (PVC) was examined—the effects of sawdust content on structural and thermal changes, and rheological and mechanical properties being of main interest. The results revealed that the torque and die entrance pressure drop values during mixing were independent of sawdust particles up to 23.1 wt%. The extrudate swell monotonically decreased up to 33.3 wt% sawdust content. Smooth wood‐like texture with controllable size of the extrudate could be obtained at a sawdust content greater than 33.3 wt%. Tensile, impact, flexural and hardness properties of the PVC/sawdust composites considerably decreased with up to 16.7 wt% sawdust content before leveling off for higher sawdust loadings. The composites having sawdust higher than 16.7 wt% showed a benefit of cost savings. The decreases in the mechanical properties of PVC with sawdust are explained in association with the presence of moisture, interfacial defects between fibre and polymer, and fibre dispersions in the PVC matrix. Thermal degradations of PVC in PVC/sawdust composites were evidenced by a decrease in decomposition temperature and an increase in polyene sequences, which were caused by Cl cleavage due to strong hydrogen bonds of fibre–PVC molecules. The maximum of tanδ transition and the glass transition temperature were found to improve with sawdust content as a result of re‐formation of hydrogen bonds between the macromolecules of the fibre and the polymer. The overall results in this work suggest that the properties of PVC/sawdust composites were strongly influenced by sawdust content up to 16.7 wt%. Beyond this value the effect of sawdust content on the properties was comparatively small. Copyright © 2003 Society of Chemical Industry     

Effects of compatibilizer type and rubber‐wood sawdust content on the mechanical,morphological, and thermal properties of PVC/LDPE blend

This article aimed to investigate the mechanical, morphological and thermal properties of PVC/LDPE blend with and without the addition of compatibilizers. The effects of LDPE content, compatibilizer type and rubber‐wood sawdust loading on the properties of the blend were evaluated. The experimental results suggested that as the LDPE content was increased the mechanical properties of PVC‐LDPE blend progressively decreased due to poor interfacial adhesion. The continuity and compatibility between PVC and LDPE phases could be improved through three different types of compatibilizers which included chlorinated polyethylene (CPE) poly(methyl‐methacrylate‐co‐butyl acrylate) (PA20) and poly(ethylene‐co‐methacrylate) (Elvaloy). The PA20 was found to be the most suitable compatibilizer for the blend. A radical transfer reaction was proposed in this work to explain the structure and thermal changes of the PVC in PVC‐LDPE blend. The decomposition temperature of PVC in the blend decreased with the loading of the PA20 and the wood sawdust. As the sawdust content was increased the tensile and flexural moduli increased with considerable decreased in the tensile, flexural and impact strength, a slight improvement being achieved if the PA20 was incorporated in the composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 598–606, 2006     

Mechanical properties of woodflour unsaturated polyester composites

Agrowastes and woodflour are a potential and attractive alternative of cheap reinforcement for brittle polymeric materials because they can reduce costs and, at the same time, improve certain properties. On the other hand, their high moisture sorption and low microbial resistance are disadvantages that need to be considered and, as far as possible, corrected. Polyester resins are widely used throughout the world, and can be processed with reinforcing agents very easily. In this work, the effect of the addition of chemically modified woodflour on the final properties of unsaturated polyester composites was studied. The filler was treated with an alkaline solution to increase its interfacial area and then modified with maleic anhydride (MAN) under severe reaction conditions (140°C, 24 h). No improvement in the mechanical behavior of polyester–woodflour composites was found when particles were only alkali treated, while the composites prepared with MAN-treated woodflour offered better performance under compressive loads. Simple mechanical models used to fit the experimental flexural behavior indicated that a good compatibility between filler and matrix was obtained regardless of the kind (treated or untreated) of reinforcement used. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2121–2131, 1998     

Effect of moisture content on mechanical properties,thermal and structural stability and extrudate texture of poly(vinyl chloride)/wood sawdust composites

Mechanical properties and thermal and structural changes of poly(vinyl chloride) (PVC)/wood sawdust composites were assessed with respect to the effect of moisture content, varying from 0.33 to 3.00 % by weight in the composite, for three different wood sawdust contents. The swell ratio and texture characteristics of the composite extrudates were also evaluated. Unique explanations were given to describe changes in the composite properties in terms of molecular interactions between PVC, cellulosic sawdust and moisture, such as dipole–dipole interactions, interfacial defects and bonding, fibre swelling, and moisture evaporation. The results suggest that at low moisture content the tensile modulus decreased and elongation at break of the composites increased with moisture content, the effect being reversed for high moisture content. Tensile strength decreased with increasing moisture content up to 1–2 %, and then unexpectedly increased at higher moisture contents. The effect of moisture content on flexural properties of the composite was similar to that on tensile properties. Impact strength of the composites was considerably improved with moisture content at low sawdust contents (16.7 wt%), and was independent of the moisture content at higher sawdust contents (28.6 and 37.5 wt%). A decrease in decomposition temperature with an increase in polyene content was evidenced with increasing moisture content, while the glass transition temperature did not change with varying moisture content. The extrudate swell ratio increased with the shear rate but remained unaffected by moisture content. The bubbling and peeling‐off in the composite extrudate occurred as a result of the evaporation of water molecules and the application of a high shear rate. Copyright © 2004 Society of Chemical Industry     

Processability,morphology and mechanical properties of wood flour reinforced high density polyethylene composites

Abstract

Wood flour reinforced high density polyethylene (HDPE) composites have been prepared and their rheological properties measured. The melt viscosity decreased as the processing temperature increased and the wood flour content decreased. A power law model was used to describe the pseudoplasticity of these melts. Adding wood flour to HDPE produced an increase in tensile strength and modulus. Composites compounded in a twin screw extruder and treated with a coupling agent (vinyltrimethoxysilane) or a compatibliser (HDPE grafted with maleic anhydride) exhibited better mechanical properties than the corresponding unmodified composites because of improved dispersion and good adhesion between the wood fibre and the polyalkene matrix. Scanning electron microscopy of the fracture surfaces of these composites showed that both the coupling agent and compatibiliser gave superior interfacial strength between the wood fibre and the polyalkene matrix.     

Mechanical,morphological, and thermal properties of chemically treated pine needles reinforced thermosetting composites

Natural fibers are widely used as reinforcement in composites. Pine needles are one of the major biowaste generated by Pinus roxburgii plant. This species is found abundantly in the forests of Himachal Pradesh. In this work, composites of urea–resorcinol–formaldehyde resin‐reinforced with Pine needles fibers were prepared. Fibers were chemically modified to improve their compatibility with matrix. These fibers were mercerized with NaOH solution and acetylated to increase their hydrophobic character. The chemically modified fibers were characterized with Fourier transform infrared spectra, ¹³C‐nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscopy. The composites were prepared with treated and untreated fibers containing 30% fibers by weight using compression molding technique. The morphology of the materials thus obtained was evaluated by scanning electron microscopy. The chemical modifications of fibers improve fiber–matrix adhesion and also have markedly effect on mechanical properties of composites. Moreover, the thermal resistance of these composites was improved on chemical modification. These results indicate that chemically modified fibers exhibit better compatibility with the polymer matrix than that of untreated fiber. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci, 2013     

Mechanical,morphological, and thermal properties of chemically treated pine needles reinforced thermosetting composites

In the recently published article cited above, the author's name Aishwarya Jyoti was incorrectly printed. The correct author's name is published above.     

Improvement in mechanical and thermal properties of unsaturated polyester- based hybrid composites

Polymer matrix composites are used in automobile, structure and aerospace industries due to their light weight and high strength. The present research has an aim to reinforce locally developed silica nanoparticles and glass fibers in unsaturated polyester to produce polymer-based hybrid composites. Composites were synthesized by hand lay-up method with 1, 2, 3 and 4 wt% of silica sand nanoparticles and glass fiber. Mechanical tests like tensile, impact and micro-hardness were performed on the obtained polymer hybrid composites. The results of mechanical properties of the hybrid polymer matrix composites revealed an increasing trend. The SEM analysis was performed on the developed and fractured tensile testing samples. The SEM analysis showed the presence of silica nanoparticles in the samples and pulling action of fibers were seen under fractured tensile tests. The pulling actions of fibers from polymer matrix delayed the fractured mechanism and enhanced the mechanical properties. Silica nanoparticles filled the cavities generated during tensile test and extensive enhancement was revealed in tensile as well as impact energy. Toughness of the hybrid composite was also enhanced as a result. The thermal properties of the hybrid polymer composites were analyzed using thermogravimetric analysis. Thermal stability of the composite has been marginally increased with increasing wt% of reinforcement.     

Effect of nanocrystalline cellulose on morphological,thermal, and mechanical properties of Nylon 6 composites

In this study, nanocomposites based on Nylon 6 and nanocrystalline cellulose (NCC) were prepared by melt compounding. Then, morphological, thermal, and mechanical properties were analyzed for NCC content between 0 and 7 wt%. Morphological analyses showed different roughness in fractured surface of neat Nylon and its nanocomposites caused by the presence of NCC. Mechanical results showed that the optimum properties were obtained at 3% NCC which could be related to relatively good NCC dispersion at low concentrations with good Nylon‐NCC bonding. Overall, flexural (41%) and tensile (23%) moduli, as well as tensile strength (11%) were increased up to 3% of NCC. However, elongation at break and impact strength decreased with NCC addition. Finally, density and hardness showed only a small increase of 5 and 3%, respectively. POLYM. COMPOS., 37:1473–1479, 2016. © 2014 Society of Plastics Engineers     

Morphological,mechanical, tribological,and thermal expansion properties of organoclay reinforced polyethylene composites

The morphological, mechanical, thermal, and tribological properties of high‐density polyethylene (HDPE) composites reinforced with organo‐modified nanoclay (3 and 6 wt%) were studied. A commercial maleic anhydride‐based polymeric compatibilizer (PEgMA) was used to improve the adhesion between the polyethylene and clay. Transmission electron microscopy (TEM) characterization of composites revealed that nanoclay exists mainly in a multilayered structure in the HDPE matrix. Mechanical testing of composites showed that Young's modulus and tensile strength increased with nanoclay content. Coefficients of the linear thermal expansion (CLTE) of HDPE–PEgMA–clay composites were slightly lower in the flow direction than those of HDPE–PEgMA. The tribological properties were measured in dry conditions against a steel counterface. The friction coefficient of the matrix was decreased by the addition of clay. Electron microscopic results suggested that the wear mechanism for HDPE and HDPE composites was mainly adhesive. Clay agglomerates were observed on the worn surfaces of the composites, which may partly explain decreased friction. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers