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Manufacturing Techniques
Published in B. T. Åström, Manufacturing of Polymer Composites, 2018
Unsaturated polyester is the dominating resin not only due to its attractive performance-to-cost ratio, but also because it is the easiest to process. Improved properties are naturally achieved with vinylesters and epoxies, but processing becomes progressively more difficult and pulling speeds lower, since the resin reactivity determines the maximum speed all other things unchanged, see Figure 4-59. Pultrusion of epoxies is particularly problematic since they do not shrink as much as unsaturated polyesters and vinylesters, meaning that the solid surface of the partially crosslinked composite is in full contact with the die for a greater portion of the die length; epoxies also tend to stick to the die to a greater degree than other resins, leading to inferior surface finish. Perhaps more in pultrusion than in other processes, it is up to the processor to formulate the resin. To achieve high processing speeds without significantly sacrificing product properties it may be necessary to use several different initiators as well as accelerators and inhibitors. It is also normal practice to use various additives, including internal mold releases. In addition to the previously mentioned resins, several others, including phenolics, acrylics, and PURs, are used in pultrusion.
Cellulose-Based Composites from Kenaf Fibers
Published in S.M. Sapuan, J. Sahari, M.R. Ishak, M.L. Sanyang, Kenaf Fibers and Composites, 2018
J. Sahari, M.A. Maleque, M.L. Sanyang
Unsaturated resins, such as polyester resins, are used in sheet and bulk molding compounds, and are utilized in a variety of industrial applications such as automotive, aircraft, watercraft, building panels, furnishings, appliances, and fixtures for home construction. Since polyester resins are lightweight and weather resistant, it is widely used as stainless steel in numerous applications. Bing Yang (2014), studied the kenaf based cellulose fiber-reinforced composites with polyester, as well as the effect of glass fiber reveiled that the tensile modulus increased due to reinforcement of kenaf-based cellulose in polyester and the efficiency of stress transfer along the kenaf interface. This resulted in a strong interaction between polyester and kenaf fibers. Table 10.3 presents the modulus predicted with polyester, kenaf fibers, and glass fibers.
Thermoset Polymer Matrix–Based Natural Fiber Composites
Published in Shishir Sinha, G. L. Devnani, Natural Fiber Composites, 2022
Polyester was discovered in the DuPont lab in the 1930s but W. H. Caruthers set it to work on newly invented nylon in 1941. The first commercial polyester terylene was made in 1941. They are mainly used in commercial applications, but have certain limitations for use in the high-performance composite. The curing of polyester is done by an additional reaction in which unsaturated double bonds appear wherever cross-linking occurs. Polyester mainly contains three parts: a polyester chain; a cross-linking agent such as styrene that helps in lowering the viscosity to improve the process; and an initiator, mainly peroxides such as benzoyl peroxide. Styrene not only works as a cross-linking agent but also helps to lower the viscosity to attain better processability. Certain materials like chloro styrene, methyl methacrylate, and diallyl phthalate are used as pre-impregnation. The characteristic of formed polyester composites mainly depends on curing or a cross-linking agent used for impregnation. These can be processed to cure at either room temperature or high temperature, showing versatility in processing (Kandelbauer et al., 2014). Polyester resin is a viscous liquid that is prepared from the condensation reaction of unsaturated dibasic acid and glycol. This resin has a double bond between carbon atoms. The basic structure of polyester has a double bond carbon-carbon group and ester group. Polyester usually contains styrene as a monomer, which reduces the viscosity of the solution and also reacts with a chain to form a cross-linked rigid structure. Polyester has a lower temperature ability and less mechanical properties but they are characterized by lower cost, great processing versatility, and high performance.
Experimental Investigation on Flexural Strength Enhancement of Eucalyptus based Bamboo Composite Deck Board
Published in Cogent Engineering, 2023
Yirga Z. Yimer, Alemayehu G. Gualu, Ermias A. Amede, Leule M. Hailemariam
The materials that will be used in the experiment are. Eucalyptus Globulus was gathered from Gondar, Ethiopia.Bamboo (Oxytenanthera Abyssinica) was gathered from a Gondar, Ethiopia—Quara (Aletash National Park).Adhesive resin (Unsaturated Polyester Resin) taken from the market commercially available Aypols manufactured by Aypols Polymers Private Limited. Polyester (unsaturated) Resin is a liquid polymer that, once cured (cross-linked with styrene using certain compounds called hardeners), maintains the solid shape taken in the mold (Davallo et al., 2010).
Study of chemical and mechanical properties of Dharbai fiber reinforced polyester composites
Published in Advanced Composite Materials, 2018
S. Kalyana Sundaram, S. Jayabal, N.S. Balaji, G. Bharathiraja
The Dharbai fibers used in this investigation belong to grass family and do not require much water for higher yield. The source of this fiber is the leaf of Dharbai plant. Polymers generally act as good binders for fibers, as observed from several references [13–17]. The load transfer capability and lower cost have prompted the selection of polyester as the matrix material. Additionally, unsaturated polyester offers various advantages such as ease of moldability, better handling, and superior flow properties. The physical properties of polyester resin are shown in Table 1. The resin systems used in this study consist of unsaturated polyester resin, Methyl ethyl ketone peroxide (MEKP) catalyst, and cobalt octate accelerator. The accelerator and catalyst present in the resin system helps in enhancing the reaction rate and ensures uniform curing of composite sheets.
Fabrication and characterisation of polyester/hexagonal boron nitride/sisal fibre hybrid composites for microelectronic applications
Published in Australian Journal of Mechanical Engineering, 2023
Akash Deep Kushwaha, Brijesh Patel, Alok Agrawal
Unsaturated isophthalic polyester is a thermoset resin supplied by Carbon black composites, Mumbai India is taken as the continuous phase. A cobalt accelerator and Methyl Ethyl Ketone Peroxide (MEKP) catalyst are used to cure the unsaturated polyester. Isophthalic polyester resins show higher thermal stability and dimensional stability. It favourably possesses low density (1.15 g/cm3), good heat conduction ability (0.323 W/m-K) and low dielectric constant (3.32 @ 1 MHz). Cured polyester has a glass transition temperature of 78°C and a coefficient of thermal expansion of 68 × 10−6/oC. Hexagonal boron nitride (hBN) of size 5 microns is supplied by Souvenier Chemicals, Mumbai, India. It has high intrinsic thermal conductivity (200 W/m-K) for effective heat conduction and a low dielectric constant of 4.8 @ 1 MHz for proper signal distribution. Apart from that, its low density (2.3 g/cm3) and very low CTE (4 × 10−6/oC) are the additional favourable properties required for such applications. The silane coupling agent in combination with ethyl alcohol is used for the modification of the surface of the hBN and is supplied by Himedia, Mumbai, India and Changshu Hong Sheng Fine Chemical Co. Ltd., Changshu City, China, respectively. Sisal fibre is used as secondary filler material and is incorporated in the form of short fibre of approximate size of 4 mm. The density of the sisal fibre is 0.85 g/cm3. Among the various natural fibres, sisal fibre is selected because it possesses good mechanical and electric insulation properties. Sodium hydroxide flaxes used to modify the surface of sisal fibre were purchased from Rankem Corporation Limited, New Delhi, India.