Forestry 485Forestry 485

Lecture 3-7: Mastics, Hot Melts, Lecture 3-7: Mastics, Hot Melts, etc.etc.

MasticsMastics

Very high viscosity and tackVery high viscosity and tack

Paste-like consistencyPaste-like consistency

High solids, low solventHigh solids, low solvent

Common form of construction adhesivesCommon form of construction adhesives e.g., Polyurethane adhesives are commonly supplied e.g., Polyurethane adhesives are commonly supplied

as a masticas a mastic General purpose home, shop, construction adhesiveGeneral purpose home, shop, construction adhesive Some used for industrial production of wooden I-Some used for industrial production of wooden I-

beamsbeams

Mastic CompositionMastic Composition

Composition varies widely; may contain:Composition varies widely; may contain: Rubber (natural, synthetic, recycled); latex in Rubber (natural, synthetic, recycled); latex in

water or dispersion in solventwater or dispersion in solvent Tackifiers: Rosin, resin, phenolics, Tackifiers: Rosin, resin, phenolics,

resorcinolicsresorcinolics Fillers: Carbon black, chalk, zinc oxide, clayFillers: Carbon black, chalk, zinc oxide, clay Plasticizers, antioxidants, curing agents, otherPlasticizers, antioxidants, curing agents, other

Mastic UsesMastic Uses

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

items)items)

Mastic UseMastic Use

Require only nailing pressure to effect a Require only nailing pressure to effect a good bond.good bond.

These adhesives generally have good dry These adhesives generally have good dry and wet strength.and wet strength. HOWEVER, they do not stand up well to HOWEVER, they do not stand up well to

repeated cyclic moisture exposure.repeated cyclic moisture exposure.

Good gap-filling ability.Good gap-filling ability.

Hot MeltsHot Melts

100% Solid Thermoplastics100% Solid Thermoplastics Pellets, blocks, chipsPellets, blocks, chips

Set (harden) within seconds upon removal Set (harden) within seconds upon removal of heat source (“heat-loss adhesive of heat source (“heat-loss adhesive system”)system”)

Used extensively for edge-banding, Used extensively for edge-banding, veneer splicing, and similar applicationsveneer splicing, and similar applications

Common Types of Hot MeltsCommon Types of Hot Melts

PolyamidePolyamide Typical application: Veneer splicingTypical application: Veneer splicing Low melt viscosity aids glue spread and wettingLow melt viscosity aids glue spread and wetting Rapid setup upon coolingRapid setup upon cooling

Ethylene-vinyl acetate (EVA)Ethylene-vinyl acetate (EVA) Typical application: Edge banding & veneeringTypical application: Edge banding & veneering High viscosity at application temperature; 50,000 to High viscosity at application temperature; 50,000 to

60,000 cps at 200 60,000 cps at 200 ooC C

EVA Glues are also used for Hobby, EVA Glues are also used for Hobby, Industrial Assembly, and PackagingIndustrial Assembly, and Packaging

Industrial EVA stick applicators

Industrial EVA slug applicators

Industrial EVA granular applicator for package closing

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