23/03/2011 Technical Information Power Adhesi Home Customer Service Technical Information TEC Glue Guns TECBOND Glue Contact Us 0 Items SEARCH HOME > Technical Information Technical Information Products Glue Gun Categories Skip to section: Glue Categories HOT MELTS EXPLAINED Speciality Systems Ethylene Vinyl Acetate (EVA) Glue Gun Accessories Polyamide (PA) Polypropylene (PP) Glue Gun Spares Polyurethane (PUR) Glue Gun Manuals STRUCTURAL BONDING Glue Gun Diagrams Service Temperature Hide All Amount Of Adhesive Applied Show All Time Taken To Assemble TERMINOLOGY Open Time Viscosity Heat Resistance HEALTH AND SAFETY ADVICE Skin Contact Eye Contact Inhalation Removal Of Hot Melt From Components Fire GLUE GUN USE STORAGE GLUE USAGE HOT MELTS EXPLAINED Users of hot melt should perform their own tests to satisfy themselves that the adhesive selected, with adequate controls in place to ensure correct usage, will suit their requirements. Generally, testing of a bond should not be made until at least 24 hours after the application. Hot melt glues are thermoplastic polymer based materials in solid form which contain no solvents, VOCs or water and are non-hazardous, FDA approved and leave no risk of mould or odours in finished product. In use, they are heated and applied molten to one surface of the parts to be glued, when the surfaces are pressed together the hot melt quickly cools to form an almost instant bond. Hot melt Adhesives can be formulated using several different base polymers. The choice of polymer affects adhesion, temperature resistance, chemical resistance and cost. Ethylene Vinyl Acetate (EVA) A commonly used polymer suitable for both packaging and product assembly formulations. It is economical and effective at service temperatures from -30C to 80C. Polyamide (PA) Polymer used to formulate adhesives with better resistance to chemicals and temperature extremes, typically -60C to 130C Polypropylene (PP) Polymer used for adhesives with specific adhesion properties such as delayed setting time and often used for spray formulations. Effective at service temperatures from -30C to 110C hotmeltgluegunsticks.co.uk/technical-i 1/523/03/2011 Technical Information Power Adhesi used for spray formulations. Effective at service temperatures from -30C to 110C Polyurethane (PUR) Polyurethane Reactive Hot melt initially sets like a conventional hot melt by losing heat and solidifying. Following this, the PUR absorbs a small amount of moisture from the surrounding materials or atmosphere and cross links. This is a permanent chemical change that takes several days which increases both heat and chemical resistance. Since a small amount of moisture is required for this reaction to take place it is better if at least one substrate is porous. If moisture is only available from the edge of the bond then cross linking will be slow and unreliable. However, additional water should not be applied to a surface before bonding as this will overwhelm the reactive component of the adhesive and prevent cross linking. TECBOND Speciality glues are packed in individual cartridges with re-sealable caps. STRUCTURAL BONDING Over recent years, developments have allowed many product assembly applications to benefit from the efficiencies of hot melt adhesives. High performance bonding is now possible on a variety of substrates however final bond strength will vary depending upon the following criteria: 1. Service Temperature Hot melts are thermoplastic and consequently become brittle at low temperatures and soft at high temperatures. The strength of a bond will vary with both the amount and rate of load at different temperatures because of the nature of hot melts, 2. Amount of adhesive applied Bond strength will vary with the amount of glue and application method. Puddles of glue retain heat longer and spread more than thin lines therefore giving more glued area and more time to join substrates whilst the glue remains hot. 3. Time taken to assemble Hot melt starts to cool as soon as it is applied and if the assembly is not completed quickly enough bond strength will suffer. This is known as a cold bond and although initial results appear acceptable, the bond can deteriorate over a 24-hour period. The higher the temperature of the glue when the bond is made, the better the strength. TERMINOLOGY Open Time The open time is the period available to make a satisfactory bond after the hot melt adhesive has been applied. This can be as short as a second or two or be up to several minutes. The maximum open time of a hot melt adhesive is dependent upon these factors: 1. The formulation chosen. 2. The application temperature and the method of application. 3. The type of substrate, its surface temperature and ambient conditions. For maximum bond strength, it is important to get the parts together as soon as the adhesive has been applied. The different factors that affect open time mean it is not practical to quote exact times, therefore the open times of TECBOND hot melt adhesives are broadly classified into three groups: Short (1-15 seconds), Medium (15-30 seconds) and Long (30-60 seconds). Viscosity Values shown have been measured using standard ASTM D3236. When solid hot melt is heated it melts, the higher the temperature the more liquid the glue becomes. This liquid state is known as the viscosity, expressed in centipoises and measured with a viscometer. TECBOND hot melts can be dispensed at varying temperatures therefore their viscosity is expressed broadly as: Low (500-3000cps), Medium (3000-6000cps) and High (6000-15000cps). Low viscosity glue flows freely and can increase gun output, reduce stringing and give closer bonds. It is less suitable for porous materials such as foam or fabric. High viscosity glue may reduce gun output but is suitable for uneven surfaces or where gap-filling or low-sag hotmeltgluegunsticks.co.uk/technical-i 2/5