Joining Techniques To understand which adhesive(s) is the most suitable for joining like and unlike materials To understand the advantages and disadvantages of the main 5 adhesives

Preparation Adhesives require a clean and prepared surface in order for the materials to fully bond together. Polymers: Surfaces should be cleaned thoroughly Should be roughened with abrasive paper Metals: Surfaces should be degreased Should be roughened with an abrasive paper Woods: Woods are porous so the adhesive will ‘soak’ into the surface Surfaces should be held in place securely – Why?

Health and Safety COSHH: Control Of Substances Hazardous to Health Risks: 1/ Burns from corrosive adhesives 2/ Inhalation of vapours 3/ Storage

Risk Assessment HAZARDRISKPEOPLE AT RISK – Who?CONTROL MEASURES – What can be done? Use of solvent based adhesives 1/ Burns from corrosive adhesives USER Use appropriate PPE equipment – gloves/eye protection Users fully briefed on safe use of adhesives Appropriate supervision Wash area immediately with warm soapy water Eyes – Seem medical attention immediately: Use eye bath 2/ Inhalation of vapours USER/ PEOPLE IN THE IMMEDIATE AREA Use only in well ventilated areas (Extraction) Appropraite supervision Use of face mask or respirator If dizziness occurs seek medical attention 3/ Storage TECHNICIAN and TEACHING STAFF Store in secure METAL cupboard Cupboard easily identifiable (YELLOW) with appropriate signage Staff to be fully briefed as to safe storage of adhesives Checks by technician on regular basis

Adhesives 1.Contact Adhesive (Unlike materials) 2. Acrylic Cement (Acrylic) 3. Polystyrene Cement (HIPS) 4. Epoxy Resin (Most materials) 5. Polyvinyl Acetate: PVA (Woods)

Contact Adhesive (Unlike materials) ApplicationsAdvantagesDisadvantages Unlike Materials 1/ Plastic to Wood 2/ Metals to Polymers 3/ Fabric to most materials 4/ General Purpose Able to bond unlike materials Ideal for large sheet gluing Quick bonding – Less need for clamping Easy application (Sold in tubes) Must be applied to both surfaces – Must be left for some time before pushed together Relatively expensive Solvent-based – Contains volatile organic compounds (VOCs)

Acrylic Cement (Acrylic) ApplicationsAdvantagesDisadvantages Acrylic Rapid bonding of acrylics Difficult to apply Difficult to give a neat joint Relatively expensive Solvent-based – Contains volatile organic compounds (VOCs)

Polystyrene Cement (HIPS) ApplicationsAdvantagesDisadvantages High Impact Polystyrene Strong bond – Causes the materials to weld together Water-like consistency – Can use a brush to apply -Absorbed into joint by capillary action Relatively expensive Solvent-based – Contains volatile organic compounds (VOCs)

Epoxy Resin (Most materials) ApplicationsAdvantagesDisadvantages Most materials including expanded polystyrene High strength to bonds Hardens immediately Excellent chemical and heat resistance Expensive Reaches full strength only after a few days Requires manual mixing – Can be messy

Polyvinyl Acetate: PVA (Woods) ApplicationsAdvantagesDisadvantages Woods (and porous materials) Gives a strong joint Relatively inexpensive Surfaces need to be securely clamped together for a long period of time Generally not waterproof