Poly(styrene‐co‐butyl acrylate) latex‐reinforced polyester nonwoven fabric composites: Thermal and morphological studies

A series of thermoplastic composites were fabricated by impregnating the polyester nonwoven fabric in poly(styrene‐co‐butyl acrylate) latex having different monomer compositions of styrene and butyl acrylate viz., 100/0, 90/10, 80/20, 70/30, 60/40, and 50/50 weight by weight. Thermogravimetric analysis (TGA) of the composites was performed to establish the thermal stability and their mode of thermal degradation. From TGA thermograms, a slight improvement in thermal stability of the composites was noticed compared to polyester nonwoven fabric. Degradation kinetic parameters were obtained for the composites using Broido and Coats–Redfern methods. The activation energy (E_a) of the composites for the thermal degradation process lies in the range 7.1–261 and 60–264 kJ/mol for Broido and Coats–Redfern methods respectively. Morphology of the tensile‐fractured composites was studied using scanning electron microscopic technique. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of silicon carbide filler on mechanical and dielectric properties of glass fabric reinforced epoxy composites

Fiber‐reinforced polymeric composites (FRPCs) have emerged as an important material for automotive, aerospace, and other engineering applications because of their light weight, design flexibility, ease of manufacturing, and improved mechanical performance. In this study, glass‐epoxy (G‐E) and silicon carbide filled glass‐epoxy (SiC‐G‐E) composite systems have been fabricated using hand lay‐up technique. The mechanical properties such as tensile strength, tensile modulus, elongation at break, flexural strength, and hardness have been investigated in accordance with ASTM standards. From the experimental investigations, it has been found that the tensile strength, flexural strength, and hardness of the glass reinforced epoxy composite increased with the inclusion of SiC filler. The results of the SiC (5 wt %)‐G‐E composite showed higher mechanical properties compared to G‐E system. The dielectric properties such as dielectric constant (permittivity), tan delta, dielectric loss, and AC conductivity of these composites have been evaluated. A drastic reduction in dielectric constant after incorporation of conducting SiC filler into epoxy composite has been observed. Scanning electron microscopy (SEM) photomicrographs of the fractured samples revealed various aspects of the fractured surfaces. The failure modes of the tensile fractured surfaces have also been reported. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of catalyst on the curing of tetrafunctional epoxy resin formulations

Cure kinetics of tetraglycidyl 4,4′-diaminodiphenyl methane resin formulations with diaminodiphenylsulfone as hardener and borontrifluoride-ethylamine adduct as accelerator has been studied by differential scanning calorimetry (DSC) technique both dynamically and isothermally. The DSC scans show multiple exotherm peaks, indicating the complex nature of reaction. The curing exotherms obtained have been analysed to derive the kinetic parameters associated with the curing process. The heat of reaction shows a decreasing trend with increasing catalyst concentration.     

Synthesis and characterization of polyurethane/polybutyl methacrylate interpenetrating polymer networks

A series of castor oil based polyurethane (PU) and poly (butyl methacrylate) (PBMA) interpenetrating polymer networks (IPNs) (PU/PBMA; 80/20, 60/40, 50/50, 40/60 and 20/80) were prepared by sequential polymerization method using toluene diisocyanate (TDI), dibutyl tin dilaurate (DBTL) as catalyst and ethylene glycol dimethacrylate (EGDM) as crosslinker. Tensile strength, percentage elongation at break and surface hardness; FTIR and optical properties of the IPNs are reported. Thermo gravimetric analyzer (TGA) studies of the IPNs are performed in order to establish their thermal stability. TGA thermogram shows that the thermal degradation of IPN was found to proceed in three steps. The microcrystalline parameters such as crystal size (N) and lattice disorder (g in%) of IPNs have been estimated using wide angle X-ray scattering (WAXS) studies. The surface morphology of the IPNs has been studied using scanning electron microscope (SEM).     

Effect of aggressive environments on composite properties

Glass-fiber-reinforced epoxy and unsaturated polyester (UPE) composites were fabricated from diglycidyl ether of bisphenol-A (DGEBA) using 10% diethyl triamine (DETA) as a hardener and unsaturated polyester (UPE) using 1.5% each of methyl ethyl ketone peroxide (MEKP) and cobalt naphthanate as a catalyst and an accelerator, respectively. The fabricated composites were exposed to different aggressive environments, such as heat, water ageing, lubricating oil, fuel, and seawater. The exposed specimens were characterized by physical, chemical, mechanical, and thermal properties. A marginal increase (12%) in the mechanical properties in heat ageing, but a reduction in properties in other exposed systems of the epoxy and polyester glass-fiber-reinforced (GFRP) composites, were observed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 795–799, 1999     

Spectral and thermal studies on polyaniline–epoxy novolac resin composite materials

Polyaniline–epoxy novolac resin composite materials (PANI–RESIN) were prepared by emulsion polymerization technique and characterized by infrared and electronic absorption spectra, conductivity, particle size, and thermogravimetric and differential scanning calorimetric analysis. The conductivity of PANI–RESIN samples decreased with the addition of the RESIN as 0.1, 0.02, and 0.04 S/cm for 25, 50, and 75% addition of the RESIN, respectively. TGA thermograms of PANI–RESIN samples are more or less similar to those of polyaniline salts (PANI), which were stable up to 225°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3507–3512, 1999     

The effect of thermal treatment on the properties of PP films and laminates

Films of polypropylene, co-extruded polypropylene/nylon/polypropylene and clear polyester laminated to polypropylene have been subjected to thermal treatment over a temperature range of 118–120°C. The mechanical, optical, thermal and chemical resistance of these films have been studied before and after the thermal treatment. The improvement in properties has been explained on the basis of enhancement of crystallinity. © 1997 John Wiley & Sons, Ltd.     

Sorption and diffusion of aldehydes and ketones into natural rubber blends

Sorption and diffusion of aldehydes and ketones through different NR blends of bromobutyl (BIIR), chlorobutyl (CIIR), neoprene, EPDM, polybutadine, and SBR were studied at 25, 40, and 60°C. From the data, the Arrhenius activation parameter for diffusion, E_D, was determined. From the temperature dependence of the sorption constant, the enthalpy of sorption, ΔH, and entropy of sorption, ΔS, were also determined. The activation parameters are found to follow the conventional trend. Transport properties are affected by the nature of the interaction of solvent molecule, by its size, and also by the structural variation of the elastomers. For all the solvents, the polymer blends remained intact but the blends in the presence of benzaldehyde showed degradative reactions at higher temperature. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 101–112, 1998     

Microstructure,thermal, physico–mechanical and tribological characteristics of molybdenum disulphide‐filled polyamide 66/carbon black composites

With an objective to investigate the influence of molybdenum disulphide (MoS₂) on physico–mechanical and tribological properties of polyamide 66 (PA 66), was compounded with MoS₂ in the presence of carbon black (CB). The compounded material was injection molded to make test specimens to evaluate physico–mechanical, thermal, and tribological (wear, friction, and laser etching) characteristics. It was found that tensile strength, percentage elongation at break, and tensile modulus of PA 66/CB/MoS₂ composite increased linearly with increase in MoS₂ content. The impact strength of the PA 66 matrix increased from 37.2 to 43.2 J/m with an increase in MoS₂ content. The wear behavior of PA 66/CB/MoS₂ composites have been investigated under dry sliding conditions at different normal loads, sliding distances, and sliding velocities at room temperature. It was found that the introduction of MoS₂ in the presence of CB has certainly reduced the friction, wear behavior of PA 66 with improvement in laser etching resistance. MoS₂ could increase the adhesion between the transfer film and the counterface surface. The ability of the synergistic fillers in helping the formation of thin, uniform, and continuous transfer film would contribute to enhance the wear resistance of PA 66 composites. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Ethylene Methacrylate (EMA) Co-polymer Toughened Polymethyl Methacrylate Blends: Physico-mechanical,Optical, Thermal and Chemical Properties

Polymethyl methacrylate (PMMA) was blended with ethylene methacrylate (EMA) copolymer in different compositions by melt mixing technique using Haake Rheochord twin screw extruder. The physico-mechanical, thermal, optical and chemical properties of PMMA/EMA blends were investigated with special reference to the blend compositions. The impact strength of the blends was found to increase significantly with increase in EMA content, without affecting the optical properties significantly. Optical micrograph images of the blends reveals that the rubbery phase dispersed as domains in the continuous PMMA matrix at 5 and 10 wt. % addition of EMA. The PMMA/EMA, 80/20 blend was found to exist as co-continuous system. Attempts have been made to correlate changes in morphology with mechanical properties. The influence of chemical ageing and heat ageing on the mechanical performance of PMMA/EMA blends has been studied. Four composite models such as series model, parallel model, Hapin-Tsai and Kerner's model have been used to fit the experimental tensile strength, tensile modulus and surface hardness.