Melamine formaldehyde thermoset composites

About 95% of the melamine produced is largely used as a feedstock In the production of melamine-formaldehyde thermoset composites In the plastics industry and to produce molding compounds, textile finishes, and paper coatings. Melamine is also used in ieather tanning. 

Wood Composites—these are resin-bonded composite boards where the particles are wood shavings, flakes, chips, or fibers bonded with thermosetting adhesives that can be urea formaldehyde, melamine formaldehyde, phenol formaldehyde, or diisocyanate. In recent years, the markets for OSB and MDF board have been rapidly increasing. Most particle board production uses urea-formaldehyde as a binder that is acid setting. Hence, sodium borates (alkaline) can interfere with the setting. As a result, boric acid has been the major boron compound used as the flame retardant in particle board.28 29 Typically, a loading of 12%-15% of boric acid in MDF is required to meet the ASTM E-84 Class A rating. If sodium borate is used as a flame retardant, phenol-formaldehyde binder, that is compatible with alkaline chemicals, is commonly used. 

For example, U.S. Pat. No. 3,367,917 [15] describes a thermosetting melamine-formaldehyde-benzoguanamine resinous molding composition containing a hbrous hller, such as a-cellulose pulp, in an amount between 25 and 42% by weight. 

Thermoset composite systems of phenol and formaldehyde, some of which can he substituted for a number of structural applications can also be considered as engineering plastics and they have been in use for a very long time. In recent applications, improved urea - melamine resins have been used as matrices more and more for composite systems, because of their non-melting, high thermal and chemical resistances, hardnesses, mechanical-dimensional stabilities and low flammabilities. 

For a general introduction, see Wood adhesives - basics. Aminoplastic resins are polycondensation products of the reaction of aldehydes with compounds carrying amine or amide groups. Formaldehyde is by far the primary aldehyde used. The name amino-plastic is traditional, but is a misnomer these are thermosetting, irreversibly hardening resins. Two main classes of these resins exist urea-formaldehyde (UF) resins and melamine-formaldehyde (MF) resins. Today, for wood adhesives, pure MF resins are not used anymore because of cost, and only melamine-urea-formaldehyde (MUF) adhesives are used. The main use of these resins is in composite products such as particle board, plywood, medium density fibreboard (MDF), oriented strand board (OSB), glu-lam/flngerjointing and furniture. 

A wide range of adhesive types and chemistries are used to bond wood elements to one another (Table 2), but relatively few adhesive types are utilized to form the composites themselves. The vast majority of pressed-wood products use synthetic thermosetting adhesives. In North America the most important wood adhesives are the amino resins (qv), eg, urea-formaldehyde (UF) and melamine-formaldehyde (MF), which account for 60% by volume of adhesives used in wood composite products, followed by the phenolic resins (qv) eg, phenol-formaldehyde (PF) and resorcinol-formaldehyde (RF), which account for 32% of wood composite adhesives (12,13). The remaining 9% consists of cross-linked vinyl (X-PVAc) compounds, thermoplastic poly(vinyl acetates) (PVA), soy-modified casein, and polymeric diphenylmethylene diisocyanate (pMDI). Some products may use various combinations of these adhesives to balance cost with performance. 

Thermosets can be divided into several classes depending on the chemical composition of the monomers or pre-polymers (resins). Important thermosetting resins in current commercial applications are the condensation products of formaldehyde with phenol (phenolic resins), urea or melamine (amino resins). Other major classes are epoxy resins, unsaturated polyester resins, allyl resins and isocyanate resins. 

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