PLTW 2.1.2 – Exam Study Guide.

PLTW 2.1.2 – Exam Study Guide. • a substance that, when applied to the contact surfaces of two separate components, binds them together and resists their separation. • commonly referred to as glue, paste, or cement. - answerAdhesives *Adhesives* Adhesives can be classified in many ways: - answerSuch as chemistry type, structural versus non-structural, or cure mechanism *Adhesives* Choosing an effective adhesive for a particular application requires consideration of several factors including: - answer1. Substrates. What materials are you bonding together? 2. Environment. What conditions will exist during the bonding process? What conditions will exist when put into use 3. Load. What stresses (magnitude and direction) will be applied to the joint? What type of load will be applied (repetitive, dynamic, constant, and so on)? 4. Cost. What is the cost in terms of materials and production? *Adhesives* What are the stresses applied to a joint? (2) What are the types of loads applied to a joint? (3) - answerSTRESSES: magnitude and direction LOADS: repetitive, dynamic, and constant *Adhesives* What are the 7 types of adhesives? - answer1. Cyanoacrylates (super glue) 2. Hot melt glue 3. White glue 4. Wood or Carpenter's glue 5. Polyurethane (Gorilla®Glue) 6. Epoxy *Adhesives* What is the adhesive made of? • it is an acrylic resin. • the main ingredient is an acrylic monomer that transforms to a plastic state after curing. - answerCyanoacrylates (Super Glue) *Adhesives* How does it work? • it can only bond with a surface when there is moisture present. The molecules in the glue react with the moisture to form tight chains in between the two contact surfaces. • a thin layer of water should be applied to dry surfaces to facilitate the reaction. The reaction generates heat and cures instantly. - answerCyanoacrylates (Super Glue) *Adhesives* What materials does it bond well with? (wood, metal, paper, plastic, and so on) This type of adhesive adheres to a wide variety of materials including rubber, glass, ceramic, wood, metals, and plastics. - answerCyanoacrylates (Super Glue) *Adhesives* Advantages? • instant bond and immediate handling strength • good environmental resistance (resists the appearance of weathering and aging) • strong tensile bond. - answerCyanoacrylates (Super Glue) *Adhesives* Disadvantages? • tendency to stick to human skin • requires moisture to form a bond • short shelf life • lower shear strength than epoxy • do not fill in large gaps between materials. - answerCyanoacrylates (Super Glue) *Adhesives* Common uses? • bonding the pads of musical instruments (saxophones and clarinets) • tacking wires to surfaces in electronics • temporarily holding together components as an epoxy cures • bonding skin and fingernails for topical skin closure - answerCyanoacrylates (Super Glue) *Adhesives* Other IMPT info? • commonly called super glue or crazy glue. • Acetone (or nail polish remover) can chemically dissolve the bonds in this glue. - answerCyanoacrylates (Super Glue) *Adhesives* What is the adhesive made of? It is a polymer that can be made from one of a variety of bases, which include polyolefins, polyurethanes, and silicon rubber, among others. - answerHot Melt Glue *Adhesives* How does it work? • It is a thermoplastic adhesive that melts at a high temperature but solidifies when cooled. • It is melted and then applied using extrusion (typically in a hot glue gun) or rolling or spraying the adhesive onto a surface then joining the surfaces to be bonded. - answerHot Melt Glue *Adhesives* What materials does it bond well with? (wood, metal, paper, plastic, and so on) This type of adhesive adheres to a wide variety of materials including rubber, glass, ceramic, wood, metals, and plastics. - answerHot Melt Glue *Adhesives* Advantages? • filling in gaps between materials or bonding together uneven surfaces • can be used on porous and non-porous surfaces • is quick setting • has excellent moisture resistance. - answerHot Melt Glue *Adhesives* Disadvantages? • low strength • susceptibility to fail at temperatures near the application temperature • it's hot! - answerHot M