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Polyhexahydrotriazines: Synthesis and Thermal Studies
Published in Didier Rouxel, Sabu Thomas, Nandakumar Kalarikkal, Sajith T. Abdulrahman, Advanced Polymeric Materials, 2022
Nitish Paul Tharakan, J. Dhanalakshmi, C. T. Vijayakumar
A thermosetting polymer also known as a thermoset is a prepolymer material that cures irreversibly. The cure may be induced by heat, generally above 200°C, through a chemical reaction or suitable irradiation. Thermoset materials are usually liquid or malleable prior to curing and designed to be molded into their final form or used as adhesives. Others are solids like that of the molding compound used in semiconductors and integrated circuits. Once hardened, a thermoset resin cannot be reheated and melted to be shaped differently. Thermosetting resin may be contrasted with thermoplastic polymers which are commonly produced in pellets and shaped into their final product form by melting and pressing or injection molding.
Environmental Durability of Fiber-Reinforced Polymer Nanocomposites
Published in Bankim Chandra Ray, Rajesh Kumar Prusty, Dinesh Kumar Rathore, Fibrous Polymeric Composites, 2018
Bankim Chandra Ray, Rajesh Kumar Prusty, Dinesh Kumar Rathore
Most of the structural polymeric composites are based on thermosetting polymers. The widely used polymeric composites for load carrying applications are based on epoxy resin. The starting epoxy resin usually exists in liquid form that, upon the addition of a curing agent (hardener), solidifies through the formation of three-dimensional cross-linking bonds. The most important feature of a solid thermosetting polymer is its irreversible phase transformation, that is, upon heating it does not melt, rather, it decomposes above a certain temperature. Hence, all of the processing steps for the synthesis of a polymer composite are to be completed before solidification occurs. For making a nanofiller-reinforced polymer composite, usually the nanofiller should be dispersed properly in the polymer prior to the addition of a hardener. Once the hardener is added, curing takes place and the material solidifies.
Materials for 3D Printing
Published in Rafiq Noorani, 3D Printing, 2017
Thermosetting polymers are arranged in a cross-linked 3D shape. They are chemically transformed into a rigid structure after cooling from a heated plastic condition. However, a thermosetting polymer cannot be reshaped once it is cooled during the curing process; therefore, they cannot be recycled. In addition, in some cases, the polymers used are cured by nonthermal mechanisms. This type of polymer typically includes alkyds, phenolics, amino resins, and epoxies. Thermosetting polymers are brittle, possessing mechanically and thermally better properties than thermoplastics. That is, they are stronger than thermoplastic polymers, making them suitable for high-temperature applications. Thermosetting polymers have a wide range of applications, such as electronic components made from alkyds, due to their good electrical insulation. Also, phenolics have high heat and electrical resistance, making them great electrical wiring and connector devices. Aminos are known for their rigidity and hardness; therefore, they are used in housing appliances such as toilet seats. Lastly, epoxies have great dimensional stability and possess high-mechanical strength properties; they are typically used in pressure vessels, rockets motor casings, heavy tools. Figure 5.4 shows a comb that has been 3D printed and ready to use.
Effect of poly(ether imide) blends on the physical properties of thermoplastic glass mat composites
Published in Advanced Composite Materials, 2018
Se Hyun Kim, Je Sung Youm, Moo Sung Lee, Jeong Cheol Kim
Several attempts have been made to combine organic and inorganic materials into polymer resins to overcome the physical property limitations of pure polymer resins, resulting in so-called polymer composites. In particular, thermosetting polymer composites are widely employed for aircraft and automobile parts owing to their outstanding physical properties. However, recycling and mass production of these composites are difficult and costly. As a result, significant research interest has been paid to preparing and optimizing composites that possess thermoplastic polymer resin matrices in order to exploit the advantages of short curing times, light weights, fuel efficiency, and low costs and to effectively expand their applications [1,2].
Real-time inverse solution of the composites’ cure heat transfer problem under uncertainty
Published in Inverse Problems in Science and Engineering, 2020
K. I. Tifkitsis, A. A. Skordos
The manufacturing of fiber-reinforced thermosetting matrix composites involves several stages such as lay-up, draping, resin impregnation or consolidation and curing. The cure process is a non-linear heat transfer effect in which the thermosetting polymer resin reacts exothermically and is transformed from an oligomeric liquid to a glassy solid. The quality of the final part depends strongly on phenomena taking place during the cure governed by manufacturing process parameters and boundary conditions. The selection of cure process parameters is crucial for eliminating potential induced defects such as undercure or thermal overshoot in thick components.
Impact properties of thermoplastic composites
Published in Textile Progress, 2018
Ganesh Jogur, Ashraf Nawaz Khan, Apurba Das, Puneet Mahajan, R. Alagirusamy
The reinforcing fibres are surrounded by a matrix which may be polymeric, ceramic or metallic. The primary function of any matrix is to assist in keeping the fibres in the desired location with controlled fibre placement or orientation. Additionally, the matrix also acts as a load-distributing agent between the fibres, thus preventing buckling of fibres within the composite during compression loading. Furthermore, the resin helps to protect the fibres from both mechanical and environmental damage [1]. Textile composite structures may contain either thermosetting resins or a thermoplastic matrix; the matrix is an important component, for example it is estimated that slight damage in the matrix can reduce the load-bearing capability of a composite by 50% [4]. Until recently, thermosetting polymer composites have been predominant because of their excellent structural, mechanical and chemical properties in many applications; the thermoset composites have excellent resistance to solvents, abrasion, and corrosion and also good dimensional stability, fatigue and creep properties. However, thermosetting resins are not recyclable or repairable once they have undergone the curing process and thus pose difficulties in disposal. When these composites are subjected to excessive heat, they undergo chemical decomposition before degrading and whilst they possess some thermal stability, the resins are not be able to withstand very high temperatures as they degrade at temperatures around 170–180 °C. The fabrication process for a thermoset composite is somewhat complex as it involves further components in addition to the base resin such as curing agents, hardeners, and flowing agents. In the curing stage, the polymer molecules in the thermoset undergo chemical reactions with these additives and form three dimensional cross-links, and thus make the composite permanently hard and rigid. Owing to their rigidity and low elongation properties, thermosetting resins demonstrate poorer energy absorption than a thermoplastic matrix [5]. Several studies have been conducted to try to improve fracture toughness or impact resistance by adding plasticizers, rubbers or thermoplastic particles to the thermoset resin. However, there is a reduction in mechanical properties even after increasing fracture resistance, maybe because the enhancement made to pure thermoset matrix by the addition of the above-mentioned particles cannot be transferred efficiently to the composites due to the presence of fibres which hinders the growth of plastic regions in the matrix [2].