Decorative laminates

When describing in more detail the characteristics and methods of manufacture of laminated sheet materials of different types it is helpful to use the classifications below, each of which is covered by a British Standard High-pressure laminates Decorative continuous laminates Direct-faced boards Composite boards. 

Uses Moisture-resist., protective films for outdoor use, transportation industry, pkg., building laminates, decorative applies. release film for printed circuit boards, thermosetting resins, epoxies, phenolics, polyester, rubber compds. in food-contact coatings Reguiatory FDA 21CFR 175.270 Trade Name Synonyms Tedlar Series [DuPont... 

See also continuous laminate decorative laminate high-pressure laminate electrical laminate. 

Laminated, Decorative and Non-Decorative Plastic Sheet Thermoset Sheet, Rod and Tube Polyvinyl-Chloride Sheet, Rigid, High Impact Thermoset Phenolic Sheet, Cotton Reinforced, Post-Forming Polyethylene Sheet... 

Phenol—formaldehyde resins are used as mol ding compounds (see Phenolic resins). Their thermal and electrical properties allow use in electrical, automotive, and kitchen parts. Other uses for phenol—formaldehyde resins include phenoHc foam insulation, foundry mold binders, decorative and industrial laminates, and binders for insulating materials. 

Urea—formaldehyde resins are also used as mol ding compounds and as wet strength additives for paper products. Melamine—formaldehyde resins find use in decorative laminates, thermoset surface coatings, and mol ding compounds such as dinnerware. 

Early laminates tended to be small because available presses were small, and their original uses were to replace small parts such as the natural mica insulator boards used in radio chasses. As decorative laminates evolved from industrial laminates and the size grew to serve markets such as tabletops, countertops, and wall paneling, laminate dimensions tended to fall into the typical building module ratio of about two length to one cross, such as 2 x 4s,... 

The commonly used resins in the manufacture of decorative and industrial laminates ate thermosetting materials. Thermosets ate polymers that form cross-linked networks during processing. These three-dimensional molecules ate of essentially infinite size. Theoretically, the entire cured piece could be one giant molecule. The types of thermosets commonly used in laminates ate phenoHcs, amino resins (melamines), polyesters, and epoxies. 

The most commonly used reinforcement for high pressure decorative and industrial laminates is paper (qv). The strong substrate layers, or filler, are kraft paper. Kraft is a brown paper made from a sulfate pulp process (8). It consists of both short cellulose fibers from hardwoods and long fibers from conifers. The long fibers impart most of the wet strength required for resin saturation processes. 

Other reinforcements that may be used in the substrate layers of decorative laminates and throughout the stmcture of industrial laminates are woven fabrics of glass or canvas and nonwoven fabrics of various polymeric monofilaments such as polyester, nylon, or carbon fibers. Woven and nonwoven fabrics tend to be much stronger than paper and have much more uniform strength throughout the x—y plane. They greatly enhance properties of laminates such as impact and tear strength. 

In small pieces or as inserts, laminates may be used unsupported because they are quite stiff and strong. The modulus of a high pressure decorative laminate is about 7 GPa (106 psi) at room temperature. Thick laminates range up to 25 mm and are very strong, having flexual strength of 130 MPa (19,000 psi). These products are used unsupported as toilet partitions, laboratory tops, and so forth. 

The properties of standard grades of high pressure decorative laminates manufactured are shown in Table 1. Tables 2 and 3 show properties of industrial laminates (12,13). 

Table 1. Performance Properties and Values for Decorative Laminates...

Aesthetic properties are of greatest concern in decorative laminates. These include gloss, appearance, cleanabiUty, wear resistance, stain resistance, and other surface properties. Physical properties are of most importance for industrial laminates. These include strength, electrical and thermal properties, expansion coefficient, and punchabiUty. The definitions of the laminate grades in these standards foUow. 

General-purpose type is a high pressure decorative laminate (HPDL) designed for both horizontal and vertical appHcations where appearance, durabiUty, resistance to stains, and resistance to heat up to 135°C (275°F) are requited. 

Miscellaneous Types. Various decorative effects have been developed which meet specific aesthetic requirements. These laminates may have special visual appeal, such as gloss finish, deeply embossed textures, and metallic surfaces. They are designed for specific installations and may not be suitable for all apphcations. For this reason, they are not included in these standards. Information concerning thein proper appHcation, properties, and care should be requested from the manufacturer. 

Particle board and wood chip products have evolved from efforts to make profitable use of the large volumes of sawdust generated aimually. These products are used for floor undedayment and decorative laminates. Most particle board had been produced with urea—formaldehyde adhesive for interior use resin demand per board is high due to the high surface area requiring bonding. Nevertheless, substantial quantities of phenol—formaldehyde-bonded particle board are produced for water-resistant and low formaldehyde appHcations. 

Composites. The history of phenoHc resin composites goes back to the early development of phenoHc materials, when wood flour, minerals, and colorants were combined with phenoHc resins to produce mol ding compounds. In later appHcations, resin varnishes were developed for kraft paper and textile fabrics to make decorative and industrial laminates. Although phenoHcs have been well characterized in glass-reinforced composites, new developments continue in this area, such as new systems for Hquid-injection molding (LIM) and sheet-molding compounds (SMC). More compHcated composite systems are based on aramid and graphite fibers. 

A melamine laminating resin used to saturate the print and overlay papers of a typical decorative laminate might contain two moles of formaldehyde for each mole of melamine. In order to inhibit crystallization of methylo1 melamines, the reaction is continued until about one-fourth of the reaction product has been converted to low molecular weight polymer. A simple deterrnination of free formaldehyde may be used to foUow the first stage of the reaction, and the build-up of polymer in the reaction mixture may be followed by cloud-point dilution or viscosity tests. 

Production of decorated melamine plastic dinner plates makes use of molding and laminating techniques. The pattern is ptinted on the same type of paper used for the protective overlay of decorative lamiaates, treated with melamine resia and dried, and then cut iato disks of the appropriate size. 

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