Thiourea-formaldehyde

Decorative laminates have a core or base of Kraft paper impregnated with a phenolic resin. A printed pattern layer impregnated with a melamine-formaldehyde or urea-thiourea-formaldehyde resin is then laid on the core and on top of this a melamine resin-impregnated protective translucent outer sheet. The assembly is then cured at 125-150°C in multi-daylight presses in the usual way. 

Figure 28 Right richly-mottled Bakelite wool holder, 1940s. Front toast rack and Banda-lasta picnic ware and salt and pepper set in urea-thiourea-formaldehyde, 1927-32. The powderedform of thiourea made it possible to create softer mottled effects than with granular urea-formaldehyde...

Resins may influence phototendering of rayons. Wood (26) has reported that viscose rayon fabrics treated with urea formaldehyde or thiourea formaldehyde resin are protected from the degradative effects of mercury vapor lamp radiation. The mechanism of the protective effect is not fully understood as yet. Possibly resins can quench free radicals formed during irradiation. Work with resin-treated cotton indicates that simultaneous scission of cellulose chain molecules and resin-cellulose bonds occurs on exposure to light (63). 

Urea and thiourea-formaldehyde Kitchenware Available in pale colours... 

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 pure resin Ester gum modified phenol-formaldehyde Urea formaldehyde Thiourea formaldehyde Coumarone-indene. . 

Aliphatic double bond ISO , B 120 , Thiourea Formaldehyde COCU, COBr2, CHsCOCl X-ray interference Band spectra Band spectra... 

Epichlorohydrin Ethinyloestradiol Ethylene dibromide Ethylene oxide Ethylene thiourea Formaldehyde (gas)... 

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]. 

Thiourea-formaldehyde resin n. An amino resin made by polycondensation of thiourea... 

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. 

Thiourea closely resembles urea in that reaction with formaldehyde gives methylol derivatives and then resinous condensates which on continued heating yield network structures. Thiourea-formaldehyde resins are slower curing than urea-formaldehyde resins and the hardened products are more brittle and more water-resistant. At one time thiourea-formaldehyde resins were added to urea-formaldehyde resins to give mouldings and laminates with improved water-resistance. These mixed resins have now been largely superseded by melamine-formaldehyde resins which give products with better resistance to heat. 

FlameGard PE Cone. Is recommended for use on 100% polyester FlameGard 908 is a thermosetting urea/thiourea formaldehyde resin type flame retardant producing a soft to moderate firm hand. 

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