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Forestry 485

Forestry 485. Lecture 3-7: Mastics, Hot Melts, etc. Mastics. Very high viscosity and tack Paste-like consistency High solids, low solvent Common form of construction adhesives e.g., Polyurethane adhesives are commonly supplied as a mastic General purpose home, shop, construction adhesive

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Forestry 485

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  1. Forestry 485 Lecture 3-7: Mastics, Hot Melts, etc.

  2. Mastics • Very high viscosity and tack • Paste-like consistency • High solids, low solvent • Common form of construction adhesives • e.g., Polyurethane adhesives are commonly supplied as a mastic • General purpose home, shop, construction adhesive • Some used for industrial production of wooden I-beams

  3. Mastic Composition • Composition varies widely; may contain: • Rubber (natural, synthetic, recycled); latex in water or dispersion in solvent • Tackifiers: Rosin, resin, phenolics, resorcinolics • Fillers: Carbon black, chalk, zinc oxide, clay • Plasticizers, antioxidants, curing agents, other

  4. Mastic Uses • Mastics are common construction adhesives supplied in tube or can, used to bond: • Ceramic, plastic, metal, asphalt, or acoustical tile • Hardboard and wood paneling • Wallboard, furring strips • Flooring: Wood and synthetic • Countertop laminates • Many, many others! (see Marra, p. 68 for additional items)

  5. Mastic Use • Require only nailing pressure to effect a good bond. • These adhesives generally have good dry and wet strength. • HOWEVER, they do not stand up well to repeated cyclic moisture exposure. • Good gap-filling ability.

  6. Hot Melts • 100% Solid Thermoplastics • Pellets, blocks, chips • Set (harden) within seconds upon removal of heat source (“heat-loss adhesive system”) • Used extensively for edge-banding, veneer splicing, and similar applications

  7. Common Types of Hot Melts • Polyamide • Typical application: Veneer splicing • Low melt viscosity aids glue spread and wetting • Rapid setup upon cooling • Ethylene-vinyl acetate (EVA) • Typical application: Edge banding & veneering • High viscosity at application temperature; 50,000 to 60,000 cps at 200 oC

  8. EVA Glues are also used for Hobby, Industrial Assembly, and Packaging www.impact-adhesives.com Industrial EVA stick applicators Industrial EVA slug applicators Industrial EVA granular applicator for package closing

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