Ester Resin Composites Research Articles

Chemical treatments of bamboo to modify its moisture absorption and adhesion to vinyl ester resin in humid environment

Moisture absorption is a major concern in the case of natural fibers used as reinforcement in structural composites. Bamboo strip as a kind of natural material has been used to reinforce vinyl ester resin, in this study. The moisture absorption behavior of the bamboo strips and their adhesion to vinyl ester resin at different levels of relative humidity (RH) during specimen fabrication are investigated. To improve moisture resistance and the adhesion to vinyl ester resin under high RH conditions, the bamboo strips are subject to different chemical treatments, that is with alkaline, pre-alkaline and acetic anhydride, pre-alkaline and potassium permanganate, and pre-alkaline and silane. The study of the equilibrium moisture content of modified bamboo strips shows that it is slightly increased by alkaline treatment, while it is reduced by the other three methods, especially by acetylation due to its well-known esterification. The interfacial shear strength (IFSS) by pull-out test is greatly improved after the modification and it decreases steadily as the fabrication RH levels increase for both untreated and treated samples. At high level RH (80% RH), IFSS is almost negligible except acetylated specimens. Results indicate that the severe negative impact on the IFSS by fabrication RH levels is not so considerable if the bamboo strips are subjected to acetylation as pretreatment. The interlaminar shear strength values based on short-beam shear test of unidirection bamboo strip mats/vinyl ester resin composites are well consistent with IFSS data.

Influence of Carbon Nanotubes on Mechanical and Thermal Properties of Glass Fiber Reinforced Vinyl Ester Resin Composites

Carbon nanotubes (CNTs) were incorporated into glass fiber/ vinyl ester resins composites to improve their mechanical and thermal properties, especially the interlaminar shear and longitudinal compressive strengths which are belong to the matrix-dominanted properties and much weaker than the fiber-dominated properties. In this study, a higher temperature initiator was added to improve the polymerization degree and raise the transition temperature (Tg). Mechanical testing indicated that by adding 0.4 wt% CNTs, the nano-filled composites attributed to 21%, 16%, 10%, and 8% improvement in interlaminar shear strength, compressive strength, tensile strength and flexural strength with respect to their counterparts without CNTs, respectively. Moreover, Thermogravimetric analysis (TGA) also exhibits approximately 14°C higher decomposition temperature than those of conventional composites.

Thermal properties of sawdust reinforced vinyl ester composites post-cured in microwaves: A pilot study

The mechanical properties of sawdust reinforced vinyl ester resin composites post-cured in microwaves have been measured and evaluated in earlier studies. This basic but critical and important data have caused interests in the relevant industry in Australia. This study is therefore carried out to measure and evaluate the thermal properties of the composites with a view to benefit the civil and construction industry as the materials are used in the industry. The original contributions of this paper are that samples post-cured in microwaves, irrespective of the percentage by weight and particle size of sawdust, have higher glass transition temperatures than their counterparts post-cured in an oven; these imply that the stiffness of the samples post-cured in microwaves are higher than their peers. From previous study, it was discovered that the fracture toughness increased with increasing particulate loading. These properties are vital in civil engineering applications because civil structures need composites with high rigidity and fracture toughness. It is hoped that the discussions and results in this work would not only contribute towards the development of sawdust reinforced vinyl ester composites with better material properties, but also useful for the investigations of thermal and mechanical properties in other composites.

Thermo-mechanical correlations to erosion performance of short carbon fibre reinforced vinyl ester resin composites

Thermo-mechanical properties and erosion performance of short carbon fibre reinforced vinyl ester resin based isotropic polymer composites with four different fibre weight fractions have been investigated. The storage, loss and damping characteristics were analysed to assess the energy absorption/viscous recoverable energy dissipation and reinforcement efficiency of the composites as a function of fibre content in the temperature range of 0–140°C. The composite with 30wt.% of short carbon fibres has been observed to exhibit superior thermo-mechanical response with highest energy dissipation/damping ability accompanied with a constant storage modulus without any substantial decay till 60°C. The erosion rates (Er) of these composites are evaluated at different impingement angles (30–90°), fibre loadings (20–50wt.%), impact velocities (43–76m/s), stand-off distances (55–85mm) and erodent sizes (250–600μm) following the erosion test schedule in an air jet type test rig. An optimal parameter combination is determined and subsequently validated for erosion rate minimization following Taguchi method and by conducting confirmation experiments. A correlation between the loss-modulus inverse and the erosion rate has been observed which conceptually establishes a possible mechanistic equivalence between erosion and dynamic mechanical loading modes. The morphologies of eroded surface are examined by the scanning electron microscopy to investigate the nature of wear-craters, material damage mode and other qualitative attributes responsible for promoting erosion.

Neutron irradiation effects on superconducting wires and insulating materials

On the progress of the Deuterium–Deuterium (D–D) or Deuterium–Tritium (D–T) burning plasma devices, the importance of neutron irradiation on superconducting magnet materials increases and the data base is desired to design the next generation devices. To carry out the investigations on the effect of neutron irradiation, neutron irradiation fields are required together with post-irradiation test facilities. In these several years, a collaboration network of neutron irradiation effect on superconducting magnet materials has been constructed. 14 MeV neutron irradiation was carried out at Fusion Neutronics Sources (FNS) in Japan Atomic Energy Agency (JAEA) and fission neutron irradiation was performed at JRR-3 in JAEA. After the irradiation, the Nb 3Sn, NbTi and Nb 3Al samples were sent to High Field Laboratory for Superconducting Materials (HFLSM) in Tohoku University and the superconducting properties were evaluated with 28 T hybrid magnet. Also, the organic insulation materials are considered to be weaker than superconducting materials against neutron irradiation and cyanate ester resin composite was fabricated and tested at the fission reactor. One clear result on Nb 3Sn was the property change of Nb 3Sn by 14 MeV neutron irradiation over 13 T. The critical current was increased by 1.4 times around 13 T but the increment of the critical current became almost zero at higher magnetic fields and the critical magnetic field of the irradiated sample showed almost the same as non-irradiated one.

Mechanical and Wear Characterization of GF Reinforced Vinyl Ester Resin Composites with Different Co-Monomers

This article reports the mechanical characterization and sliding wear behavior of glass fiber-reinforced vinyl ester resins of varying acid values, based on epoxy-novalocs in the presence of three different comonomers (styrene, methyl acrylate and butyl acrylate) as reactive diluents. It presents a special account of the optimization of fabrication techniques of glass fiber-reinforced vinyl ester resin composites. It outlines optimum reaction conditions such as temperature, time, monomer type and initiator concentration. The experimental plan consisted of preparation of vinyl ester resin followed by the composite samples. Mechanical characterization was done and a comparison was made between the different samples. It was found that these composites have fairly good tensile and flexural properties. The composites with styrene and butyl acrylate as co-monomers had similar tensile strength which was higher than that of the composite with methyl acrylate. Hardness values of the three composites were almost the same without any significant effect of the comonomer type. Volumetric wear rate was estimated for these samples under various test conditions. A steady wear rate regime after certain amount of sliding was observed all the three cases.

Properties and performance of fire resistant eco-composites using polyhedral oligomeric silsesquioxane (POSS) fire retardants

Fire retardants are combined with polymer resins to reduce their flammability, decrease production of volatiles and inhibit pyrolysis. The goal of this work is to develop environmentally friendly fire retardant vinyl ester resin composites by blending fatty acid vinyl ester (FAVE) resins with environmentally friendly particulate fire retardants: polyhedral oligomeric silesquioxanes (POSS), while comparing them to similar composites with talc, a standard inorganic filler. Various concentrations of POSS or talc filler were blended into commercial and FAVE brominated vinyl ester resins, Derakane 510A-40 and FAVE-Br, respectively, and commercial and FAVE non-brominated vinyl ester resins, Derakane 441-400 and FAVE-L, respectively. Thermo-mechanical characterization of the new eco-composites was conducted using dynamic mechanical analysis and thermo-gravimetric analysis. Most POSS additives performed no better than talc in improving the composite performance relative to that of the neat resin. Yet, composites reinforced with methacryl POSS (MA0735) slightly outperformed the other POSS additives and talc. This POSS additive maintained resin viscosity, improved T g , increased cross-link density, and increased flame retardance. However, the flame retardance of even this relatively high performing POSS-filled composite was very poor compared to that of brominated resins and the thermo-mechanical improvements relative to talc were small.

Preparation and characterization of organic–inorganic hybrid composites based on multiepoxy silsesquioxane and cyanate resin

AbstractA multiepoxy cubic silsesquioxane was prepared by the hydrolysis and polycondensation of trifunctional monomer (γ‐glycidoxypropyl)trimethoxysilane in a solvent mixture of methyl isobutyl ketone and anhydrous ethanol with a tetraethyl ammonium hydroxide aqueous solution acting as the catalyst, and it was successfully introduced into a cyanate resin and formed highly crosslinked organic–inorganic hybrid composites on a molecular level via a mutual cure reaction. The properties of the multiepoxy cubic silsesquioxane/bisphenol A dicyanate ester resin composites were investigated, and the results showed that introducing the cubic silsesquioxane unit into the cyanate resin successfully modified the local structure of the molecule, made the chain more rigid, restricted the chain mobility, and eventually improved the thermal stability and flame retardancy of the resin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3652–3658, 2006

Electrochemical Corrosion Behavior of Carbon Fiber/Vinyl Ester Resin Composite Used for Sucker Rods

The electrochemical corrosion behavior of carbon fiber/vinyl ester resin composite (CF/VE), which has been used for sucker rods in the oil field, was studied under an immersion condition of 3% NaCl aqueous solution at 65°C. Galvanic corrosion experiment between the CF/VE composite and the alloy used as joints linking the composite sucker rods and metal suckers was performed. The results show that in a polarization system, there are a cathode reaction of oxygen absorption on the surface of the composite and an anode reaction, which is mainly depended on the concentration of the hydroxyl (OH¯). A slight acceleration of the absorption behavior and the decrease in the mechanical properties of the CF/VE composite are caused by the galvanic corrosion.

Hygrothermal Aging on Pultruded Carbon Fiber/Vinyl Ester Resin Composite for Sucker Rod Application

The effects of hygrothermal aging on thermal and mechanical properties, and on the microstructure of pultruded unidirectional carbon fiber/vinyl ester resin (CF/VE) composites were investigated. The composite specimens were immersed in distilled water and salt solution at 95 and 65 C for more than 1000 h and the moisture absorption was recorded. The diffusion rate of moisture into the composite was found to fit Fickian’s diffusion model. SEM observation revealed that the fiber-matrix interface was weakened due to the invasion of moisture leading to debonding. Three-point flexural and interlaminar shear tests showed that both flexural strength and interlaminar shear strength (ILSS) of the composite specimens deteriorated to some extent after hygrothermal aging, while stiffness was less affected. Dynamic mechanical thermal analysis (DMTA) results indicated that the glass transition temperature of the matrix underwent complicated changes, which was attributed to the combinational effects of plasticization and the formation of hydrogen bonds in the systems.

Surface modification of ultrahigh‐molecular‐weight polyethylene fibers

AbstractTo prevent the loss of fiber strength, ultrahigh‐molecular‐weight polyethylene (UHMWPE) fibers were treated with an ultraviolet radiation technique combined with a corona‐discharge treatment. The physical and chemical changes in the fiber surface were examined with scanning electron microscopy and Fourier transform infrared/attenuated total reflectance. The gel contents of the fibers were measured by a standard device. The mechanical properties of the treated fibers and the interfacial adhesion properties of UHMWPE‐fiber‐reinforced vinyl ester resin composites were investigated with tensile testing. After 20 min or so of ultraviolet radiation based on 6‐kW corona treatment, the T‐peel strength of the treated UHMWPE‐fiber composite was one to two times greater than that of the as‐received UHMWPE‐fiber composite, whereas the tensile strength of the treated UHMWPE fibers was still up to 3.5 GPa. The integrated mechanical properties of the treated UHMWPE fibers were also optimum. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 463–472, 2004

Influence of resin chemistry on water uptake and environmental ageing in glass fibre reinforced composites-polyester and vinyl ester laminates

Hand laid up glass fibre reinforced isophthalic polyester resin and transfer moulded vinyl ester resin composites were subjected to environmental ageing. Gravimetric measurements were performed on laminate samples exposed to air and distilled water at 30°C and 60°C. Complementary porosimetry measurements on the original and fully aged samples indicated significant changes in the structure arising on ageing. Blistering showed that hydrolysis and de-bonding at the fibre-matrix interface occurred in polyester laminate to a greater extent at 60°C than 30°C. Leaching of monomer residues led to an anti-plasticisation effect in vinyl ester laminate. The influence of the fabrication method on the ageing behaviour is observed through porosity measurements on aged samples.

Effects of moisture and thermal cycling on in-plane shear properties of graphite fibre-reinforced cyanate ester resin composites

The weight change and retention of in-plane shear (±45°) strength of graphite fibre-reinforced cyanate ester resin matrix composites have been estimated on exposure to high humidity and thermal cycling, respectively. Cyanate ester resin matrix composites absorbed a remarkably small amount of moisture on exposure to high humidity. However, the degree of moisture absorption underwent a rather sudden increase to a new equilibrium level after prolonged exposure. A morphology study showed the occurrence of extensive cracking in the matrix/interface region in the form of delamination between plies as well as translaminar cracking within plies. The phenomenon is believed to be caused by weakening of the fibre-matrix interface, which was confirmed by microscopic analysis of fracture surfaces. A sudden moisture gain associated with extensive matrix/interface cracking was found to reduce the in-plane shear strength and fatigue lifetime at a given stress amplitude. The slope of the S-N curve was lower for wet specimens, implying a higher growth rate of local cracks as well as delamination. The rate of in-plane shear strength degradation was also measured on static exposure to dry heat as well as after thermal cycling to a peak temperature of 150 or 204°C. At a frequency of 10 min/cycle and for a relatively short duration, the effect of thermal cycling seems to be represented by the cumulative sum of thermal oxidation effects at the peak temperature.