Evaluation of mechanical properties of epoxy–guar gum composites

Guar gum (GG) and hydroxypropyl guar gum (HPG) are widely used in a variety of applications ranging from foods, pharmaceutics to mining and explosives. However, there have been very few studies conducted investigating the use of these materials as fillers in polymer composites. GG and HPG were incorporated in an epoxy matrix and the mechanical properties of the resultant composites were determined. The tensile strength, flexural strength, and impact strength of the composites indicate that they provide reinforcement to the composites upto 5–7.5 phr after which there is a rapid decrease in the respective properties. HPG with higher propoxy content was found to provide greater reinforcement due to its increased hydrophobic nature leading to greater polymer–filler interaction. The nature of the filler required that the water absorption and related tests be carried out. The composites showed increased water absorption and also weight loss on exposure to acid and alkali environments, with HPGs showing greater variations when compared with GG, making the composites susceptible to moisture. The study shows that these fillers make an inexpensive, eco‐friendly, and renewable addition to conventional organic and inorganic fillers where the composites do not come into immediate contact with water. POLYM. ENG. SCI., 48:124–132, 2008. © 2007 Society of Plastics Engineers     

Studies on corrosion resistant properties of sacrificial primed IPN coating systems in comparison with epoxy–PU systems

The continuous development in the field of protective coatings and the search for newer materials with improved properties have led to the emergence of interpenetrating polymer networks (IPNs) as binders for high performance organic coatings for corrosion protection. In this study, one such ambient curing IPN polymer alloy poly(epoxy–urethane–acrylate) developed specially for use in protective coatings has been studied. Undercoat and a topcoat based on the alloy have been formulated and coated over zinc ethyl silicate primed steel surfaces. Similar formulations based on an epoxy polyamide undercoat and a PU topcoat has been formulated and coated over zinc ethyl silicate primed steel surfaces. Both the systems were evaluated for their physical and corrosion resistant properties by subjecting them to accelerated laboratory tests and field test at a corrosive location. The results are reported and conclusions drawn in this paper.     

Dynamic mechanical properties of epoxy–rubber polyblends

The dynamic mechanical properties of the epoxy resin of the diglycidyl ether of bisphenol A cured with varying amounts of a carboxyl-terminated butadiene–acrylonitrile copolymer were determined. Isochronal measurements were made between ?90° to 170°C for eight compositions. Mechanical relaxations indicate the degree of interaction and the state of mixing of the two-phase system. Phase reversal occurs at a volume fraction of 0.5, where an intermediate compound is formed. In the low concentration range of the elastomeric phase, the impact strength improvement correlates well with an increase in the energy absorption of the relaxation. The known morphology of the system at this composition range allowed testing of various phenomenological mechanics models proposed to calculate the tensile properties of composite systems.     

Matrix–size interactions in epoxy–glass fibers composites in relation to mechanical relaxations and effects of thermal aging

A study was carried out to examine the effect of removing the size from the surface of glass fibers in order to determine its role with respect to thermoxidative aging. Dynamic mechanical relaxation data have revealed that mechanical losses were always greater than the calculated upper bound values. The effects of removing the size from the surface glass fibers for epoxy matrix composites were found to be completely different when a fluoroligomer was used to modify the resin. Contrary to the case of the conventional epoxy resin, the characteristics of the composites containing fluoroligomer-modified resin were found to be insensitive to the removal of the size from the glass fibers surface. The presence of the size on the surface of the fibers provides an interlayer that degrades through the formation of more lightly crosslinked products than the matrix, thereby providing a large increase in dynamic mechanical losses after thermal aging. © 1995 John Wiley & Sons, Inc.     

Design of carbon/glass/epoxy‐based radar absorbing composites: Microwaves attenuation properties

Due to high specific strength, fatigue resistance, and stiffness, reinforced plastic composites have great deal of relevance in aerospace applications such as electromagnetic interference shielding, radar absorption, etc. These radar absorption structures offer good mechanical properties, absorption characteristics, and less interference with external profile making them viable for aerospace structure design. Present venture trades the investigation concerning the attenuation of electrical component (electromagnetic waves) through the inclusion of different carbon‐based absorbers in glass/epoxy. Short carbon fibers like carbon black and multi‐walled carbon nanotubes were utilized as the lossy components. The samples were manufactured via vacuum assisted resin infusion technique which gave uniform thickness and minimum void content. Particles were mixed in resin and infused in the glass preform. The effects of changing the absorber materials, number of layers of glass fiber mat and glass fiber itself were analyzed. Sandwiched absorbing structures with aramid honeycomb were also fabricated. The samples were tested via free space measurement technique. Two charts of results were obtained i.e. one with dielectric parameters and other with the reflection loss. Short carbon fibers showed the best fallouts in this study. Moreover, thickness with 16 layers of glass fiber was also evidenced as optimum for the structure. POLYM. ENG. SCI., 54:2508–2514, 2014. © 2013 Society of Plastics Engineers     

PU／EP／PBA三元IPN弹性体的力学性能

测试了一系列以ＰＵ为第一网络的ＰＵ／ＥＰ／ＰＢＡ三元ＩＰＮ的力学性能,并详尽考究考察了其影响因素。通过研究,得到一类具有良好综合的弹性体,其拉伸强度和扯断伸长率可同时达到最佳值。研究表明,发迹合成条件,可达到控制调节材料性能的目的。第一网络的性质和组分间的相容性,是决定体系最终性能的两个重要方面。     

Compensation of microwave‐source heating attenuation into epoxy–glass composites: Experimental results

The final goal of this study was to manufacture an epoxy–glass leaf spring by microwave processing. The physical properties of the final part to be manufactured, in particular, the mechanical properties, were directly related at the repartition of microwave‐source heating during the treatment. The major problem in microwave processing, however, is the attenuation of the microwave source. Here, we propose a dielectric effect of attenuation inversion of the electromagnetic waves as a new method for the uniform treatment of epoxy–glass by microwave energy. This solution used the dielectric properties of the mold to control the microwave‐heat‐source attenuation into the composite to be treated. Many experiments were carried out to validate the proposed solution. The results show that the microwave‐source heating attenuation could controlled and inversed. We demonstrated the uniform treatment of epoxy–glass parts about 100 cm long by means of the compensation of microwave‐source attenuation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39908.     

Dynamic mechanical behavior of LCP fiber/glass fiber–reinforced LLDPE composites

Liquid crystalline polymer (LCP) fibers and glass fibers have been used to rein force linear low density polyethylene (LLDPE) by using an elastic melt extruder and the compression molding technique. The impact behavior of hybrid composites of different composition is compared and is explained on the basis of the volume frac tion of the fibers. Addition of glass fibers decreases the Izod impact strength LLDPE. The impact strength of the composites increases when glass fibers are placed by LCP fibers. Dynamic mechanical α and β relaxations are studied and effect of variation of fiber composition on these relaxations is reported in the tem perature range from −50 to 150°C at 1 Hz frequency, a relaxation shifts toward higher temperatures with addition of fibers in LLDPE. Addition of fibers increases the storage modulus of LLDPE.     

Variation in physical and mechanical properties with coating thickness in epoxy–diamine–aluminum system

The mechanical properties and glass‐transition temperature within different thickness organic coatings made of diglycidyl ether of bisphenol A epoxy resin and 3‐aminomethyl‐3,5,5‐trimethylcyclohexylamine hardener are determined. The coatings are deposited on aluminum alloy (1050) substrates after degreasing. Dynamic mechanical thermal analysis and differential scanning calorimetry experiments are carried out on debonded coatings before and after the material from the opposed surface to the polymer/metal interface is removed by polishing. The results clearly show that the values of the physical and mechanical properties in those coatings depend on their thickness, but there is no gradient of properties within such coatings. Therefore, at a given thickness, those properties are homogeneous within the coating. To gain a better fundamental understanding of this behavior, a qualitative model involving the chemical reactions that take place at the epoxy/metal interface and the related diffusion phenomena is given. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 891–895, 2005     

Preparation and properties of multiwalled carbon nanotube/epoxy‐amine composites

Different amounts of multiwalled carbon tubes (MWCNTs) were incorporated into an epoxy resin based on diglycidyl ether of bisphenol A and both epoxy precursor and composite were cured with 4,4′‐diamino diphenyl sulfone. Transmission and scanning electron microscopy demonstrated that the carbon nanotubes are dispersed well in the epoxy matrix. Differential scanning calorimetry measurements confirmed the decrease in overall cure by the addition of MWCNTs. A decrease in volume shrinkage of the epoxy matrix caused by the addition of MWCNTs was observed by pressure–volume–temperature measurements. Thermomechanical and dynamic mechanical analysis were performed for the MWCNT/epoxy composites, showing that the T_g was slightly affected, whereas the dimensional stability and stiffness are improved by the addition of MWCNTs. Electrical conductivity measurements of the composite samples showed that an insulator to conductor transition takes place between 0.019 and 0.037 wt % MWCNTs. The addition of MWCNTs induces an increase in both impact strength (18%) and fracture toughness (38%) of the epoxy matrix with very low filler content. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The dynamic mechanical analysis of epoxy–copper powder composites using azole compounds as coupling agents

The dynamic mechanical properties of cured epoxy resin have been studied in which copper powder treated or untreated with azole compounds was used as fillers. The untreated fillers do not shift the glass transition temperature of the matrix polymer of the composites, whereas the storage modulus rises with increasing content of fillers. The application of azole compounds as coupling agents, which could react with both copper and epoxy resin, extended the polymer–filler interactions. The composite filled with copper powder treated with benzotriazole shows a strong reinforcement effect and high resistance to moisture.     

Morphology and mechanical properties of unidirectional sisal– epoxy composites

Plant fibers are of increasing interest for use in composite materials. They are renewable resources and waste management is easier than with glass fibers. In the present study, longitudinal stiffness and strength as well as morphology of unidirectional sisal–epoxy composites manufactured by resin transfer molding (RTM) were studied. Horseshoe‐shaped sisal fiber bundles (technical fibers) were nonuniformly distributed in the matrix. In contrast to many wood composites, lumen was not filled by polymer matrix. Technical sisal fibers showed higher effective modulus when included in the composite material than in the technical fiber test (40 GPa as compared with 24 GPa). In contrast, the effective technical fiber strength in the composites was estimated to be around 400 MPa in comparison with a measured technical fiber tensile strength of 550 MPa. Reasons for these phenomena are discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2358–2365, 2002     

Morphologies and mechanical properties of organic–inorganic multilayered composites

Organic–inorganic composites have received increasing attention because such composites exhibit improved optical, electrical, thermal, and mechanical behaviors by combining properties of both organic polymers and inorganic compounds. However, tensile strength is enhanced generally at the cost of decreasing ductility, which is not suitable for biomedical applications where tissue‐like elasticity is required. In this study, multilayered poly(vinyl alcohol) (PVA)/silica composites were synthesized, which achieved a significant enhancement in tensile strength and ductility. The chemical structure, thermal stability, and fracture morphologies of multilayered films were investigated to analyze the reinforcement mechanism. The results showed that extensive plastic tearing took place in monolayered composites with low‐silica contents and in all multilayered ones, whereas the monolayered composites with high‐silica contents were dominated by brittle fracture. For layered composite with 30 wt% silica in the second layer, the elongation at break is 237.8%, which is 3.21 times that of monolayered 30% SiO₂/PVA 74.0%. Also its tensile strength is 37.8 MPa, which is 1.52 times that of monolayered 30% SiO₂/PVA 24.8 MPa. These improved mechanical properties broaden its potential application, especially the applications of PVA in medical materials, which are intensely discussed as biomaterials. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Processing and mechanical properties of organic filler–polypropylene composites

The addition of organic fillers into thermoplastic polymers is an interesting issue, which has had growing consideration and experimentation during the last years. It can give rise to several advantages. First, the cost of these fillers is usually very low. Also, the organic fillers are biodegradable (thus contributing to an improved environmental impact), and finally, some mechanical and thermomechanical properties can be enhanced. In this study, the effect of the addition of different organic fillers on the mechanical properties and processability of an extrusion‐grade polypropylene were investigated. The organic fillers came from natural sources (wood, kenaf, and sago) and were compared to short glass fibers, a widely used inorganic filler. The organic fillers caused enhancements in the rigidity and thermomechanical resistance of the matrix in a way that was rather similar to the one observed for the inorganic filler. A reduction in impact strength was observed for both types of fillers. The use of an adhesion promoter could improve their behavior. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1906–1913, 2005     

Dynamic mechanical properties of extruded nylon–wood composites

Dynamic mechanical properties determine the potential end use of a newly developed extruded nylon–wood composite in under‐the‐hood automobile applications. In this article, the dynamic mechanical properties of extruded nylon–wood composites were characterized using a dynamic mechanical thermal analyzer (DMTA) to determine storage modulus, glass transition temperature (T_g), physical aging effects, long‐term performance prediction, and comparisons to similar products. The storage modulus of the nylon–wood composite was found to be more temperature stable than pure nylon 66. The T_g range of the nylon–wood composite was found to be between 23 and 56°C, based on the decrease in storage modulus. A master curve was constructed based on the creep curves at various temperatures from 30 to 80°C. The results show that the relationship between shift factors and temperature follows Arrhenius behavior. Nylon–wood composites have good temperature‐dependent properties. Wood fillers reduced the physical aging effects on nylon in the wood composites. The comparison of the nylon–wood composite with other similar products shows that nylon–wood composites are a promising low cost material for industrial applications. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Mechanical properties and morphology of glass bead–filled polypropylene composites

The effects of the filler content and size on the mechanical properties such as tensile modulus, E_c, yield strength, σ_yc, and impact strength, S_IC, of glass bead–filled polypropylene (PP) composites have been investigated employing an Instron materials tester and a Ceast impact tester at room temperature. With increasing concentration of glass beads, E_c and S_IC increase, but σ_yc decreases non–linearly, within a filler volume fraction range of 0%−20%; under the same test conditions, the values of E_C and σ_yc for PP with bigger beads are somewhat lower than those of PP with smaller ones; the maximum values of S_IC for the composites are about 1.4 times as high as the unfilled PP; the interface between the matrix and the beads is a weak bond. The results indicate that the stiffness and the toughness of the PP composites are effectively improved by addition of glass beads.     

Thermal and mechanical properties of polypropylene–wood powder composites

The preparation and characterization of modified and unmodified polypropylene (PP)–wood powder (WP) composites were done under fixed processing conditions. Different techniques were used to study the effect of both WP size and content, as well as compatibilizer content, on the properties of the composites. The results point to the fact that, WP settles in the amorphous part of the matrix and creates new crystalline phases or zones. Scanning electron microscopy micrographs show a relatively even distribution of WP in the PP matrix, which contributes to improvements observed in the properties of the material. Hg‐porosimetry results indicate that the PP matrix, which has a low pore volume, filled the pores in the WP particles. This reduced the total volume of pores in the PP–WP composites. This observation was also supported by a general decrease in gas permeability of the material. Thermal analysis results indicate that the presence of both WP and maleic anhydride grafted polypropylene (MAPP) leads to an increase in enthalpy (crystallinity) values, but to a decrease in lamellar thickness in the composites. The thermal stability of the composites improves somewhat compared to that of PP. There were distinctive differences between the results for composites containing different WP particle sizes, as well as for composites prepared in the presence and absence of MAPP. It is clear from the results that the presence of MAPP generally improves the tensile properties of the composites. Larger WP particles gave rise to better tensile properties, in the presence and absence of MAPP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4173–4180, 2006     

Influence of different glass fiber sizings on selected mechanical properties of PET/glass composites

The properties of fiber-reinforced plastics are considerably influenced by fiber-matrix interaction. The aim of this study was to investigate the influence of glass fiber surface treatments on the morphology of poly(ethylene terephthalate) (PET) and on selected mechanical properties of unidirectional PET/glass fiber composites. The materials used here were E-glass fibers treated with model sizings including aminosilane as a coupling agent and polyurethane and epoxy resin dispersions as film formers and PET as the matrix. For identification of the degree of crystallinity of the PET matrix, differential scanning calorimetry (DSC) was used. To study the influence of the different sizings on the mechanical properties, the following tests were performed: interlaminar and intralaminar shear tests and a transverse tensile test. Dynamic-mechanical analysis (DMA) was used to characterize the behavior of the composites under dynamical load. The DSC results show that the overall crystallinity and the melting behavior of the PET matrix were hardly influenced by the glass fiber surface treatments used. The various strength properties of the composites are influenced not only by the silane coupling agent, but also by the type of film former. With an epoxy resin dispersion, the mechanical properties were enhanced compared with a polyurethane dispersion. These results were confirmed by characterization of the composites by DMA.     

Morphology,thermal, and mechanical properties of acrylonitrile–butadiene–styrene/carbon black composites

Acrylonitrile–butadiene–styrene (ABS) polymers are susceptible to degradation that increases the yellowness of the polymer, distorts the surface glossy, and affects the mechanical properties. One way to protect ABS against degradation is the addition of carbon black (CB) that can act as a stabilizer. In this work, CB was dispersed in ABS through melt‐compounding. Electron microscopy was used to study the morphology of the filled‐ and unfilled‐ABS, and revealed that the CB particles/aggregates were distributed within the styrene–acrylonitrile (SAN) phase and around the PB phase. The results of the Fourier transform infrared spectroscopy showed that upon processing of ABS, crosslinking in the polybutadiene (PB) phase was the governing degradation mechanism. Increasing the CB content resulted in increasing the heat stability of the ABS/CB compounds, which was confirmed by thermogravimetric analysis. The DTA results showed that the PB degradation peak occurring at about 395°C was disappeared by addition of CB. Impact strength test was performed to study the effect of CB on the toughness of ABS. Impact strength was reduced with increasing CB loading. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Photoinduced cationic frontal polymerization of epoxy–carbon fibre composites

UV‐activated frontal polymerization was exploited for the preparation of epoxy–carbon fibre composites. The curing process was investigated showing the frontal behaviour, and the final properties of UV‐cured composites were compared with those of the same composites obtained by thermal curing in the presence of amine as hardener. The best curing formulations were designed, defining the photoinitiator‐to‐thermal initiator ratio, which was 1.5:1.5. It was observed that the presence of the carbon fibres induced an acceleration of the front velocity. By comparing the thermomechanical properties of the thermally cured composite and the same composite crosslinked using the frontal process, we could observe that the latter showed higher T_g value and lower σ_f. This was attributed to the formation of a different polymeric network structure. © 2019 Society of Chemical Industry