Aniline thermosetting resins

The amino group attached to a phenyl ring activates the o- and p- positions on the benzene ring similarly to the OH group in phenols. For this reason, a condensation reaction of aniline and formaldehyde leads to the formation of polymeric compounds. However, the amino group also can react with formaldehyde, and more complex reactions occur. For example, in the condensation of an aromatic diamine such as m-phenylenediamine with formaldehyde, the reaction can be written as follows  

This type of polymer is used, for example, to make resins with strong anion exchange properties[5]. Because the amino groups directly connected to the aromatic ring are weak bases, further methylation can be applied to form quaternary amines that are stronger bases. Pyrolysis of this type of polymer gives indication of both type of condensation. 

Moldoveanu, V. David, Sample Preparation in Chromatography, Elsevier, Amsterdam, 2002. 

Urea can react with formaldehyde forming methylol compounds in reactions as shown beiow  

The resulting compounds may eliminate water in polycondensation reactions as follows  

---

The largest user of phenol in the form of thermosetting resins is the plastics industry. Phenol is also used as a solvent and in the manufacture of intermediates for pesticides, pharmaceuticals, and dyestuffs. Styrene is used in the manufacture of synthetic rubber and polystyrene resins. Phthalic anhydride is used in the manufacture of DMT, alkyd resins, and plasticizers such as phthalates. Maleic anhydride is used in the manufacture of polyesters and, to some extent, for alkyd resins. Minor uses include the manufacture of malathion and soil conditioners. Nitrobenzene is used in the manufacture of aniline, benzidine, and dyestuffs and as a solvent in polishes. Aniline is used in the manufacture of dyes, including azo dyes, and rubber chemicals such as vulcanization accelerators and antioxidants. 

Urea-formaldehyde resins are the most prominent examples of the thermosetting resins usually referred to as amino resins, comprising ca. 80% of the amino resins produced worldwide. Melamine-formaldehyde resins constitute most of the remainder of this class of resins, with other minor amounts of resins being produced from the other aldehydes or amino compounds (especially aniline), or both. 

Figure 3.5 Programmed TGA to 800 °C under nitrogen at 5 °C/min of stoichiometric thermoset resins based on DGEBA. DDM resin cured with diamino diphenyl methane, mPDA resin cured with m-phenylene diamine, pPDA resin cured with p-phenylene diamine, mXDA resin cured with weto-xyylene diamine, AN the stoichiometric thermoplastic reaction product of DGEBA and aniline (included for comparison). Reproduced with permission from T. Dyakonov, P.J. Mann, Y. Chen and W.T.K. Stevenson, Polymer Degradation and Stability, 1996,...

A method for preparing thermosets by modifying o,p-phenol-formaldehyde resins using paraformaldehyde and aniline to provide A-phenyl benzoxazine having a melt viscosity between 2 and 4 poise at 125°C is described. 

Phenol-formaldehyde was reported as the first commercially synthetic polymer (1899) which was introduced as BakeliteT by Baekeland in 1909. This was the period which marked the dawn for the production of commercial synthetic thermosetting polymers. Other advances in the field included the discovery of urea-formaldehyde resins in 1884 and the beginning of their commercialization as Beetle moldable resin in 1928, followed by thiourea-formaldehyde (1920), aniline-formaldehyde (Cibatine by Ciba, 1935) and melamine-formaldehyde (1937) moulding powders. The year 1909 marked the discovery of epoxy compounds by Prileschaiev, which were not used until World War 2. The first thermoset polyesters, invented by Ellis, date back to 1934 and in 1938 was reported their first use in the forms of glass-reinforced materials [1]. 

Acrylic resin formulations have been used for outdoor, weather-resistant adhesives. Pressure-sensitive acrylic adhesives are common on decals, bumper stickers, decorative plates, etc. Two-part thermosetting acrylic formulations have been developed and packaged for encapsulating, potting, and structural adhesives. Thermosetting acrylics cure by free radical-initiated addition polymerization. These materials can be cured at room temperature with benzoyl peroxide and an amine promoter (dimethyl aniline). 

Other important raw materials from M hich thermosetting sAnthetic resins are produced include aniline, dicyandiamide, and melamine. 

---