Merging of all three segments (i.e. epoxy, ester and amide) into saturated and unsaturated polymer chain has been recently reported from our Indian scientists [7-10]. Certain properties of resins may also be improved via interact of with the other unsaturated resin is another possibility. In order to improve certain properties of such reported USPEAs their blending with commercial vinylester epoxy resin is possible. While vinylesterresin is versatile industrial resin today [11,12] Hence the present paper comprises studies of interacting blending of reported unsaturated poly(ester-amide) resin with vinylester (VE) resin. The glass fiber reinforced composites of these blends have been fabricated and characterized by chemical, mechanical and electrical properties. The whole work is scanned in Scheme 1.
VERs are important classes of thermosetting polymer used for obtaining high performance composites with military, commercial as well as medical application and also find multiple applications in optical fiber coating, UV curing ink, and in printed circuit board due to their ability to form cross link . Vinylester resins are used to fabricate a variety of reinforced structures [9-10] including pipes, tanks and ducts. VERs have superior properties compared with other thermosetting polymers such as unsaturated polyester resins, are less expensive and easier to process than epoxy polymers. Most of the studied related to synthesis, modification, curing and effect of diluents carried out on VERs, based on diglycidyl ether of bisphenol –A, reported elsewhere [11-15]. Efforts are being made to develop VE resin with better toughness, lower viscosity and reduced shrinkage during cure but no studies have been reported on VE resin based on a Araldite LY556 (epoxy resin based on diglycidyl ether of bisphenol-A) and methacrylic acid therefore it interested the authors to investigate vinylesterresin based Araldite LY556 as matrix resin in glass fiber reinforced composite and effect of diluents on the mechanical properties such as tensile strength, flexural strength, and ILSS.
ABSTRACT: Over the most recent thirty years of composite materials, plastics and ceramics have been the dominant emerging material. The volume and number of applications of composite materials have grown progressively, piercing and conquering new markets relentlessly. Modern composite materials constitute an important proportion of the engineered materials market ranging from everyday products to complicated applications. While composites have already confirmed their worth as weight-saving materials, the current challenge is to make them cost effective. This paper discuss about the physical properties of borassus fruit fibre includes wax, ash, moisture, density, lignin and cellulose content. Then the composites were fabricated using vinylesterresin and tensile, compression, flexural and impact test was explored on the specimen with the volume fraction of 65-35, 70-30 and 75-25.
Vinyl esters are thermosetting resins that are successfully and continually being used in industrial applications. Its continued utilization is due to its thermal, mechanical, and chemical resistant properties, which prove to be good quality when compared with its relatively low cost. Vinylesterresin is formed from the reaction of a multifunctional epoxy resin and ethylenically unsaturated monocarboxylic acid. The product of this reaction is dissolved in styrene and gives a thermosetting liquid with a low viscosity which can be cured by radical polymerization when peroxides (e.g. MEKP) are introduced. Copolymerization of the styrene with the unsaturated vinylesterresin produces a three-dimensional structure which can elongate along the length of the epoxy chain. This allows high elongation under mechanical and thermal stress; it allows high elongation, fatigue resistance, and good thermal resistance (Blankenship et al., (1989).
Abstract: The mechanical properties of sawdust reinforced vinylesterresin 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 vinylester composites with better material properties, but also useful for the investigations of thermal and mechanical properties in other composites.
Whether a material will absorb microwave energy and convert it into heat depends on its relative complex permittivity and loss tangent. Ku et al.  showed that liquid rapid Araldite (epoxy resin) has a dielectric constant of 2.81 and a loss tangent of 0.244 at 2.45 GHz at room temperature. The loss tangent is quite high and it is expected that Araldite will absorb microwaves readily and convert it into heat. Vinylesterresin is produced from modified epoxy resin and methacrylic acid and epoxy resin absorbs microwave irradiation readily. It is therefore expected that it will also absorb micro- waves readily [9,10,20]. A possible risk in applying microwave energy to the vinylester composite is the interaction of the styrene in the resin with the high voltage (HV) transformer in the oven. The oven cavity is spot welded together and is not neces- sarily water/air/steam proof. Styrene is a highly flammable vapor and is given off during the curing process of the composite. High vapor concentrations of styrene may cause explosions. The gas may explode if it is ignited by an electric arc or the heat of the HV components. The oven does not have an exhaust fan. A blower motor inside sucks air through the air filter at the front and cools the HV transformer as the air passes. The air from the fan is blown into a duct and it cools the magnetrons. Some air is forced into the cavity at the back and then out of the steam exhaust outlet at the back. This is where the styrene-containing air will interact with HV transformer and ignition or explosion may result. Due to this, the oven was modified to ensure that ignition or explosion would not happen. Details of the modifications have been mentioned in another paper . The microwave facility used in this study is shown in Figure 6.
The resin used in this project is Hetron 922 PAW which is diluted by 50% by weight of styrene. Styrene is volatile and evaporates easily and poses an inhalation hazard. Vinylesterresin (Hetron 922 PAW) is potentially a sensitizer and can cause a more serious form of dermatitis. This is because they can cause an allergic reaction in some people. People who are allergic to these sensitizers can get dermatitis if they work near these products, even if there is no obvious contact with them. The styrene is a reactive diluent, i.e. it produces a low viscosity resin; which when mixed with an initiator (MEKP) produces vinylester. One of the by products of the reaction between the resin and the initiator is styrene fumes. Styrene can enter the lungs or through the skin. The fumes can irritate the eyes, nose and throat. Breathing in styrene fumes can cause headaches, nausea, and drowsiness. Long term damage can include memory loss and mood and personality changes (neurotoxic effects). Styrene can also cause liver damage. Styrene fumes are also very flammable.
Another sandwich panel application was the first use of FRP bridge deck for repair of truss bridges was in Wellsburg, New York. The FRP decking was chosen to replace the deteriorated reinforced concrete deck. The FRP deck weighed 80 percent less than the concrete deck, allowing an increase of the live load capacity. The deck consisted of an E-glass sandwich design with foam cores, vacuum infused with a vinylesterresin. The panels were also manufactured by Hardcore Composites. Both the top and bottom skins consisted of eight plies providing a total thickness of 15 mm per skin. The stresses in the composite were conservatively designed to reach 20 percent of ultimate and the deflection was limited to L/800. Observation of the behavior of the deck showed that no composite action developed between the deck and the superstructure, and that the joints between panels did not completely transfer load. The investigators proposed a separate study to determine if a combination of service loads and environmental exposure weaken the panels. (Alampalli et al. 2003)
Abstract: The previous work of another group of researchers found that the modulus of tension, flexural and compression increased with increasing percentage by volume of fly ash. They also documented that the viscosity of the composite increased exponentially with increasing percentage by volume of the filler. The viscosity increased sharply when the percentage by volume of reinforcer is between 35 to 50%. They failed to mention the highest percentage by weight of fly ash that could be added to the resin to get highest mechanical properties while still ensuring that the composite could be cast into moulds with ease. This project attempts to find out the optimum percentage by weight of slg in vinylesterresin as far as yield strength, tensile strength, Young’s modulus and Poisson’s ratio of the composite are taken into account. The research found that 33% by weight of filler is a favourable and convenient percentage by weight of slg to use because up to this percentage by weight of reinforcement, the mechanical properties like modulus of tension are increasing with the increase in percentage by weight of filler, while at the same time the viscosity is not high enough to prevent ease of casting the composite into moulds.
Abstract: This study investigated the strength developments and deformation characteristics of methyl methacrylate (MMA)- modiﬁed vinylester polymer concrete, with MMA contents and curing temperatures as test variables. To lower the viscosity of the vinylesterresin applied as a binder, an MMA monomer was added. In this study, the developed 168-h compressive and ﬂexural strengths were 43.8–77.2 and 18.2–21.8 MPa, respectively. Also, these values decreased as MMA contents increased and curing temperatures decreased. The coefﬁcient of thermal expansion ranged from 10.82 9 10 -6 to 14.23 9 10 -6 /°C, and it decreased as an MMA content increased. The ultimate compressive strain ranged from 0.00391 to 0.00494, which decreased with an increase in MMA contents and notably decreased with a decrease in curing temperatures. The modulus of elasticity tended to decrease as MMA contents increased and curing temperatures decreased.
vinylesterresin cured with styrene and modified with liquid rubber CTBN. A sharp drop in density causing de- trimental fracture toughness was observed in higher CTBN concentrations (>10 wt%). Balakrishnan et al.  exam- ined the fracture behavior of rubber dispersed epoxy and inferred cavitations, yielding, plastic deformation of ma- trix, crack diversion and energy dissipation caused by ru- bber particles which contribute to the improvement of the ductility of the epoxy nanocomposite system. Frohlich et al.  suggested the compatibility matching as the key to novel phase-separated nanocomposites with significantly improved toughness.
The crosslinking reactions of vinylester resins are initiated by free radicals. Free radicals are generated in several ways, including thermal or photochemical decomposition of peroxides and hydroperoxides or azo and diazo compounds. The type of vinylester resins, the method of fabrication and the requirements of the application determine the uses of initiator systems. The initiators most commonly used for vinylesterresin cure reactions are methyl ethyl ketone peroxide (MEKP), benzoyl peroxide and cumene hydroperoxide. Decomposition of these initiators can be effected by heat or by the use of accelerators or promoters, which can cause a more rapid decomposition of the initiator at a given temperature. The accelerators most commonly employed are tertiary amines, such as dimethyl- or diethyl- aniline, and metallic soaps, such as cobalt or manganese octoate or naphthenate. Vinylester resins can also be crosslinked via ionizing radiation - either actinic or high energy. Electron radiation has such high quantum energy that the free radicals required for polymerization are formed directly from the vinylesterresin.
DOI: 10.4236/ojcm.2019.94023 366 Open Journal of Composite Materials the gap between epoxy resin and polyester resin in both sides of mechanical property as well as effective economy    . Thanks to good toughness, excellent resistance, good mechanical properties, outstanding heat performance, and flexible processibility compared to unsaturated polyester, VE is being in- creasingly used in solvent storage tanks, sewer pipes, ship and boat construction, coating, automobile structural parts, swimming-pool  . Similar to other thermosets, pure vinylesterresin is inherently brittle due to their highly cross-linked structure. One approach to increase its performance is to modify with fillers at micro/nano scale -. There is a large number of studies con- ducted to investigate properties of vinylesterresin reinforced by micro/nano particles. Vahid Arabli et al. studied in curing kinetics, modeling, mechanical properties and thermal stability in graphene oxide/vinylesterresin nanocompo- site . They claimed that with a low content of graphene oxide (0.3%), the matrix became stiffer while the glass transition temperature shifted to a higher value. Dipa Ray used fly ash had a particlesize distribution in the range of 76 to 152 µm to fill in VE matrix . Auad et al. modified vinylesterresin of differ- ent molecular weights by rubber. The research group claimed that the addition of elastomers produces toughening of the networks, but at the same time a re- duction of their mechanical properties such as flexural modulus and compres- sion yield stress . S. Grishchuk et al. investigated about structure and prop- erties of vinylester resins modified with organophilic synthetic layered silicates bearing non- and co-reactive intercalants. They found that fracture toughness (Kc) and energy (Gc) were markedly improved with increasing organophilic synthetic layered silicates amount . However, along with restriction of load- ing content in polymer, the size of nano fillers is close to the molecular scale, leading to detrimental effects on properties of filled system because of interca- lating of nano particles and base material  Therefore, submicron particles have been considered as filled-gap material between nano and micro filler in re- cent years. In spite of that, in the best authors’ knowledge, there was still very few literature about using micro-nano filler for polymer matrix   . In this study, the submicron glass fiber (sGF) with diameter in the range of mi- cro-nano scale used to reinforce vinylesterresin at low content to facilitate us- ing experimental data for further research of carbon fiber composite after that. Mechanical properties were characterized to access effects of sGF on submicron composite (sMC) system.
A commercial vinylesterresin supplied by Hetron Chemical Pty. was reinforced with varying percentages by weight of sawdust. The sawdust particles were sieved into 3 diﬀerent sizes, which were <300 μm, 300–425 μm, and 425–1180 μm, respectively, with a view to increase its fracture toughness for civil and structural applications. The sawdust used varied from 0% w/t to 15% w/t in step of 5% w/t. For higher w/t% of sawdust, the mixture would be too sticky to be mixed and cast. The cast composites were cured in ambient conditions and then postcured in microwave irradiation. They were then tested for fracture toughness using short bar tests. The values of fracture toughness of the composites increased with increasing particulate size, and this is due to the size distribution of the filler. It was found that the optimum amount of sawdust (425–1180 μm) was 15% w/t, with which the increase in fracture toughness was 126% as compared to neat resin and the reduction in cost was 15%. Furthermore, the optimum amount of sawdust (300–425 μm) was also 15% w/t, with which the increase in fracture toughness was 28.3% as compared to neat resin and the reduction in cost was again 15%.
For the preparation of particle filled glass fiber reinforced vinylester composites, silicon dioxide filler particles are added to the above mixture, the composite specimen with two different filler proportions are prepared. The weight fractions of the filler in the matrix were 5%, 10% with respect to the weight fraction of the vinylesterresin.
The vinylesterresin used is Hetron 922 PAS in summer and Hetron 922 PAW in winter. The vinylester is dissolved in 50% by weight of styrene. In this study, Hetron 922 PAW was used. It is based on the reaction between methacrylic acid and diglycidylether of bishphenol A. The resin hardener ratio used in the experiment was 98% resin by volume and 2% hardener by volume (Astrom, 1997). The reinforcer was fly ash (ceramic hollow spheres) particulate and they were made 44% by volume or 33 % by weight in the cured vinylester composite [VE/FLYASH (33%)]. Forty four percent by volume or 33 % by weight of flyash in the composite is considered optimum by the ECEFC because the composite will have a reasonable fluidity for casting combined with a good tensile strength in service.
amide) into saturated and unsaturated polymer chain has been recently reported from our Indian scientists [7-10]. Certain properties of resins may also be improved via interact of with the other unsaturated resin is another possibility. In order to improve certain properties of such reported USPEAs their blending with commercial vinylester epoxy resin is possible. While vinylesterresin is versatile industrial resin today [11,12] Hence the present paper comprises studies of interacting blending of re- ported unsaturated poly(ester-amide) resin with vinylester (VE) resin. The glass fiber reinforced composites of these blends have been fabricated and characterized by chemical, mechanical and electrical properties. The whole work is scanned in Scheme 1.
Referring to the graph (figure 5) of the tensile strengths of test pieces obtained by exposing them to 180W of microwaves, it is found that with exposure duration of 30 to 40 seconds, the tensile strengths of the test pieces of are almost the same as that cured under ambient conditions. Even though, the tensile strength values of the microwave-cured samples do not higher than its ambient cured counterpart, the microwave parameters used are favourable because they bring about all the positive outcomes as mentioned in the section of yield strength (figure 4). As for the 360 W microwave processing, the tensile strengths and yield strengths (figure 4) obtained are promising but the impact strength is reduced by more than 5 percent. The parameters of microwave treatment of vinylester composites in the previous paragraph are therefore better.
It is necessary to ensure that all promoters and accelerators are thoroughly mixed into the resin before adding MEKP. These agents should never be mixed directly with MEKP. Violent decomposition and fire could result from such mixing or contamination. Stir MEKP into the resin slowly and carefully to avoid splashing. Spilled material should be absorbed in inert material such as vermiculite or sand and then wet with water. All such contaminated material should be placed in double polyethylene bags and kept out of doors and away from combustibles until it can be removed by qualified hazardous waste personnel. In case of fire, spray with water, preferably with a fog nozzle, or with carbon dioxide or foam from a safe distance. Dry chemical or other extinguishers may be effective against a very small fire .
The mean, standard deviation and coefficient of variation of the elastic modulus and hardness values determined using nanoindentation technique for the six locations are summarized in Table 3. Each grid has 40 equally spaced indents placed at a predetermined position of the surface of the coating. As the nanoindentation tests were not done on the same nanoscaled position for all the specimens, there could be some difference in the obtained results. In order to satisfy an equal variance assumption for all the 6 grids, the paired non-parametric test and the paired p-tests were performed on log transformed elastic modulus data at a 5% level. The p-value from the test was less than the alpha level (=0.05). The variation in the values of elastic modulus and hardness in Table 3 can be attributed to the fact that some indents are on vinylester whereas some are on the glass flakes. The variation of modulus with the number of indents is shown in Figure 8. The same result holds good for hardness values of the coating as well. In Figure 7, the zone between 10th and 15th indent lies on a glass flake as may be interpreted from the modulus values which lies between 10 and 25 GPa, whereas the positions of the 15th–25th indent lies on vinylester, as the modulus values are in the range of 4–8 GPa. The boundary region of the glass flakes and resin has the highest stress concentration and therefore is a weak zone as can be observed in Figure 8. The indents appear relatively shallower on glass flakes because the hardness of glass flakes is higher than that of vinylester matrix.