Thiourea-formaldehyde polymers

Van Tumhout J (1975) Use of polymers for electrets. J Electrost 1(2) 147-163 Van Tumhout J (1999) Thermally stimulated discharge of electrets. In Sessler GM (ed) Electrets, vol 1, 3. Laplacian Press, Morgan HiU, pp 81-215 Vasudevan P, Nalwa HS et al (1979) Pyroelectricity in thiourea formaldehyde polymer. J Appl Phys... 

The first commercially successful synthetic polymer was phenol-formaldehyde (PF) [Smith, 1899]. The resin was introduced in 1909 by Baekeland as Bakelite . The urea-formaldehyde resins (UF), were discovered in 1884, but production of Beetle moldable resin commenced in 1928. Three years later, Formica , phenolic paper covered with decorative layer protected by UF, was introduced. The thiourea-formaldehyde molding powders were commercialized in 1920, while in 1935, Ciba introduced Cibanite , anihne-formaldehyde (AF) molding materials, then two years later, the melamine-formaldehyde (MF). 

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]. 

Treatment of wool with a FWA, followed by post-treatment with thiourea/formaldehyde by a pad/cure method, confers a high level of protection against photoyellowing and also improves the initial fabric whiteness (134). Unfortunately, this process is not commercially viable, partly because of environmental concerns about thiourea and formaldehyde and also because much of the benefit is lost after laundering. An alternative approach is to physically separate the FWA from the wool fiber by incorporating the whitener into a suitable polymer that can be applied as a surface treatment to wool fabrics (135). The photostability of the treated fabrics is somewhat better than for conventional FWA treatments (being similar to bleached wool) but the initial whiteness is significantly lower than that of FWA-treated wool. 

For the purposes of this chapter, aminopolymers are defined as polymers formed by the interaction of amines or amides with aldehydes. Of the various polymers of this type which have been investigated, only two are currently of appreciable commercial importance, namely urea-formaldehyde and melamine-formaldehyde polymers. In addition, melamine-phenol-formaldehyde and benzoguanamine-formaldehyde polymers find limited application. In the past there has been some commercial interest in thiourea-formaldehyde and aniline-formaldehyde polymers but these products are now of little importance. The aforementioned polymers form the contents of this chapter. 

The term aminoplastics has been coined to cover a range of resinous polymers produced by interaction of amines or amides with aldehydes. Of the various polymers of this type that have been produced there are two of current commercial importance in the field of plastics, the urea-formaldehyde and the melamine-formaldehyde resins. There has in the past also been some commercial interest in aniline-formaldehyde resins and in systems containing thiourea but today these are of little or no importance. Melamine-phenol-formaldehyde resins have also been introduced for use in moulding powders, and benzoguanamine-based resins are used for surface coating applications. 

Aydin, A., Imamoglu, M., and Gulfen, M. (2008). Separation and recovery of gold(lll) from base metal ions using melamine-formaldehyde-thiourea chelating resin. J. Appl. Polym. Set. 107(2), 1201-1206. 

A comprehensive study of the chemical stability of polyacrylamide (PAA) polymers was conducted. The primary emphasis of the study was to determine the stability of Dow Pusher 500 PAA in Sundance brine at 115°F (46°C). Experiments were completed which show the effect of biocides, metals, ferrous and ferric iron salts, pH, surfactants, alcohols, antioxidants, sodium hydrosulfite, thiourea, plastic pipe, formaldehyde concentration, free radical scavengers, hydrazine, oxygen, and temperature on the chemical stability of PAA. Stability tests were conducted at temperatures ranging from room temperature to 221 F (105°C). The results showed that many substances caused substantial chemical degradation of PAA polymers in the presence of oxygen however, in many cases, the adverse effects of these substances could be reduced or eliminated by the proper selection of chemical stabilizers or the nearly complete removal of oxygen from the solutions. 

---