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Industrial Polymers
Published in Manas Chanda, Plastics Technology Handbook, 2017
Polyesters were historically the first synthetic condensation polymers studied by Carothers in his pioneering work in the early 1930s. Commercial polyesters [30] were manufactured by polycondensation reactions, the methods commonly used being melt polymerization of diacid and diol, ester interchange of diester and diol, and interfacial polymerization (Schotten–Baumann reaction) of diacid chloride and diol. In a polycondensation reaction a by-product is generated which has to be removed as the reaction progresses.
Improvement of the chemical adhesion of EPDM rubber to Sheet Moulding Compound (SMC) by the addition of phenolic resin as adhesion promoter
Published in The Journal of Adhesion, 2021
Alexandra Allue, Koldo Gondra, Isabel De Marco, Gorka Díez
Table 7 has shown that over 11 pph of phenolic resin content the interlaminar shear strength of the SMC decreases. The explanation to this fact may be that phenolic resins are polycondensation resins release water during their polymerization. If this process is performed over 100ºC, the water is evaporated creating pores in the SMC. The number of pores logically increases with the amount of phenolic resin added, decreasing the mechanical performance of the SMC. Figure 11 shows the SEM images of the SMCs prepared with 11 and 17 pph of phenolic resin, where it can be seen that the SMC with 17 pph of phenolic resin has a greater porosity than that with 11 pph. With great amounts of phenolic resin, the negative effect of porosity surpasses the enhancement of the adhesion fibre-matrix produced by the phenolic resin.
Organocatalysis with carbon nitrides
Published in Science and Technology of Advanced Materials, 2023
Sujanya Maria Ruban, Kavitha Ramadass, Gurwinder Singh, Siddulu Naidu Talapaneni, Gunda Kamalakar, Chandrakanth Rajanna Gadipelly, Lakshmi Kantham Mannepalli, Yoshihiro Sugi, Ajayan Vinu
Various methods including physical vapor deposition, chemical vapor deposition, thermal polymerization-condensation, and hydrothermal or solvothermal methods are available for the synthesis of g-C3N4 [44]. Among these methods, thermal polymerization-condensation is the most used synthesis technique for preparing carbon nitrides and the widely used precursors are urea, melamine, dicyandiamide, cyanamide thiourea, and cyanuric acid [45,46]. Polyaddition and polycondensation are the processes involved in carbon nitride synthesis, which are temperature dependent. Polyaddition is the polymerization process to convert precursors into melamine whereas polycondensation is the condensation of the melamine by the loss of ammonia to form a g-C3N4 polymer [42,44]. The carbon nitrides derived from the traditional thermal condensation method have a low surface area (>20 m2/g), highly conjugated stacking of nitrogen atoms in the heptazine structure, and nitrogen atoms with less basicity, less bridging nitrogen atoms and less defective sites at the edges for the graphitic structure. The structure of the g-C3N4 may contain the molecular units of s-heptazine (tri-s-triazine) and triazine [47]. Triazine is not as stable as the tri-s-triazine (s-heptazine) structure. For catalytic applications, g-C3N4 with tri-s-triazine units may be more beneficial as it has more nitrogen atoms, providing more anchoring and active sites for catalytic reactions. Owing to the stability and other benefits of the tri-s-triazine structure, synthesizing carbon nitrides with tri-s-triazine molecular units is given more attention [48,49].
Synthesis and characterization of aliphatic polysulfides by interfacial polycondensation of sodium tetrasulfide with dichloroalkanes in the presence of quaternary onium salts
Published in Journal of Sulfur Chemistry, 2020
Mohammadreza Kalaee, Majid Abdouss, Mohammadreza Shakiba
There are several methods for the preparation of polysulfide polymers, which Interfacial polymerization is the more appropriate method and a lot of research has been done with this method due to ease and cost-effectiveness [10]. Interfacial polycondensation is an irreversible polymerization that occurs at the water interface with a single difunctional intermediate and an inert insoluble organic solvent with a complementary difunctional reactant [11]. Heterogeneous systems are classified according to the mutual dependence between the polymer's molecular weight and the conversion yield. A high molecular weight polymer can be obtained in this system at low conversions of the reaction groups [2,12,13].