Melamine resin Subject

Superplasticizers (SP) reveal analogous effect as plasticizers it means that they improve the workability of cement mixture at constant w/c ratio or give the possibility to reduce w/c at constant workability. Therefore the strength can be improved as early as in 1984 Paillere [371] reported the concrete class of 60 MPa. The melamine resins act more effectively than the naphthalene-formaldehyde condensates [361]. The concrete subjected to thermal treatment or autoclaving shows much better strength, with respect to the reference, with superplasticizers addition. The difference between plasticizers and superplasticizers is only one the latter can be used in higher concentrations without causing excessive retardation or air entrainment. 

Because these fire-retardant salts are water-soluble and subject to leaching, several new methods have been developed which provide a water-resistant or permanent treatment for cotton fabrics and cellu-losic materials. Perkin developed a process involving successive treatment with sodium stannate and ammonium sulfate, which precipitates stannic oxide in the cellulose libers. Antimony oxide in combination with vinyl chloride or other chlorinated polymers has also been found effective. A more recent approach to this problem involves application of fire-retardant resin-forming or cross-linking compounds. " These include materials and methods based on the copolymerization of tetrakis(hydroxymethyl)phosphonium chloride and methylol — melamine, the reaction of bromoform and triallyl phosphate to form a cross-linked polymer, and the cross-linking reaction of tris(l-aziridinyl)phosphine oxide with cellulose, or its copolymerization with tetrakis(hydroxymethyl)phosphonium chloride and other materials. ... 

The initial development of polymeric MDI as a particleboard binder predates the above work but it is, we believe, based upon the same chemistry. Exterior or structural particleboard has been manufactured in North America and in Europe for years with predominantly phenol-formaldehyde binders and, in a few cases, with melamine-modified urea-formaldehyde binders. The familiar urea-formaldehyde resins are subject to hydrolysis and are thus suitable for interior board only. 

The presence of numerous hydroxyl groups able to react with formaldehyde makes starch-derived products suitable chemicals for formaldehyde-based resins. Research on this subject started many years ago and showed that in a number of applications it is possible to partially replace or extend urea formaldehyde, phenol formaldehyde and melamine formaldehyde resins without significantly affecting the finished product s performance. In many applications, adhesive systems based on formaldehyde resins incorporate a polysaccharide component. More than 4.5 Mio mto of formaldehyde-based resins have been produced in Western Europe alone. The use of carbohydrates allows lower consumption of oil-based resins and, consequently, reduced release of formaldehyde in the environment. 

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