PVA BASED ADHESIVE PVA (or Poly Vinyl Acetate) are emulsions in water and are generally used as adhesives for porous materials as they cure by evaporation. They require a route for the water to escape and will not cure (dry) when encapsulated. Primary uses are for materials such as wood, paper and cloth. PVA adhesives do come in different grades and qualities, they are identified under EN 204 as D1, D2, D3 and D4; they are explained as follows:
D1 A lower quality product for adhesive purposes with little or no water resistance. Many of us will remember this PVA glue as ‘School Glue’; it is non toxic and low odour. These normally have a lower solids content (less polymer, more water) than higher grade wood glues. Generally used as sealers or bonding aids for plastering rather than as an adhesive.
D2 Generally a higher solids product with good adhesive properties. Suitable for interior woodworking, although not water resistant.
D3 A version of D2 with higher water resistance. Suitable for internal and external applications where occasionally wet conditions exist. Although not suitable for permanently damp, wet or permanently immersed locations. See our Duo 2 in 1 Wood Glue (page 30).
D4 High strength with water resistance, once cured can be immersed. One part D4 has a reduced shelf life (up to 6 months) and can have a strong odour. Two part products have a longer shelf life but require mixing together and using immediately. Another consideration when choosing a wood adhesive is its ‘creep resistance’. This relates to the products performance when subjected to a sustained load (i.e. shelves). A product that conforms to BS EN 14256 should be used for applications subject to sustained loading (see pages26, 30 and 33).
WATER BASED ADHESIVES - see Cove-Mate (page 15), Saves Nails Solvent-Free (page 28) and Incredibond (page 20). Water based gun applied adhesives are suitable for porous surfaces in internal or relatively dry external applications. For non-load bearing situations such as dry wall adhesive, cove adhesive or for dado rails, skirting boards, etc. Cure rates will be slower than solvent based equivalents, as they will cure (dry) by evaporation. Different grades with different characteristics are available for the job in hand.
POLYURETHANE (PU) ADHESIVE - see page 26. Polyurethanes possess very high adhesion and water resistance properties, conforming to EN 204 D4. PU adhesive can be supplied either in a liquid, paste or gel form. They cure when exposed to moisture in the air and will ‘foam up’ slightly whilst curing, this gives excellent gap filling properties. Cure times are much reduced relative to PVA based adhesives. Being moisture cure they can be used on non porous materials. Being very water resistant, PU adhesives can be used in marine applications.
SOLVENT BASED ADHESIVES Solvents are often used as a ‘carrier’ for the adhesive rather than water but still cure by evaporation (of the solvent). The advantage of this is that solvents have a much faster evaporation rates than water, giving faster cure rates and often a better initial grab. The solvent still needs to escape, so at least one of the materials being bonded needs to be porous. The down side is that solvents are flammable, often with a strong odour and can be an irritant or even toxic to humans. These factors should be taken into consideration when using adhesive containing solvents especially in confined spaces.
GUNABLE SOLVENT BASED ADHESIVE These are supplied in cartridge form and often used as a replacement for mechanical fixings such as nails and screws when fixing lightweight, non load bearing items such as dado rails, skirting boards, carpet gripper and stair nosing. Strong and durable, suitable for internal and external applications. Water based products are becoming more prominent for internal applications. Refer to products on page 28, Gripbond and Saves Nails.
CONTACT ADHESIVE - see page 29. Contact adhesives have a unique method of application that gets around the issue of bonding large areas of impervious or non porous materials together. The adhesive is applied to both surfaces and the solvent carrier is allowed to evaporate before bringing the surfaces together. As there is no need for any solvent to escape, contact adhesives are used in areas such as laminating large surfaces and bonding rubber sheets to other impervious materials such as GRP (Fibreglass).
HYBRID (MS POLYMER OR SPUR) ADHESIVES Extremely versatile when used as an adhesive, these products can be seen as the ‘next generation’ of grab adhesives relative to gunable solvent based products in performance and user friendliness. They are supplied in cartridges for application with a standard sealant gun or in tubs, are moisture curing and dry to a durable flexible rubbery compound which offers good movement accommodation and excellent gap-filling between many different materials. Suitable for internal and external applications to; metal, stone, brick, polystyrene, polycarbonate, PVC, uPVC, wood, concrete, plaster, glazing, automotive, marine, the list goes on…. These have been used in the building industry for some time but are now available as an ‘All In One’ sealant and adhesive for domestic use. They can even be used in damp conditions. See pages 18-19 for GRIPBOND PRO, GRIPBOND PRO MAX, WOOD PRO AND ASTRO PRO and see page 61 for TS55.
CYANOACRYLATE (CA) ADHESIVES - see page 31. Often referred to as ‘Superglue’, CA adhesives are fast curing, moisture cure adhesives. CA requires close fitting joints, normally between small plastic or rubber parts. Higher viscosity versions will offer a small element of gap filling capability, but still require the joint to have a close fitting. Can be used to bond uPVC, rubber, wood, metal, ceramics, leather, porcelain and card among others. Note: CA will bond skin in seconds; care should be taken when using. Cyanoacrylate Accelerator is available in an aerosol form to reduce the cure time, however the use of this will compromise the bond strength.
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www.bond-it.co.uk
APPENDICES: Adhesives
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