Hotmelt polymers/adhesives

When using hotmelt polymers/adhesives (Guo et al., 2010) for coating or for the lamination of fabrics, there is no water present in the formulation. Two main groups of hotmelts can be defined thermoplastic and reactive hotmelts. Different types of chan-istry are available. Thermoplastic hotmelts are available as polyolefines, TPU, EVA,... 

A typical characteristic of physically setting adhesives is the evaporation of solvents or heatup to a molten state. Application is then in liquid form (solvent adhesives, contact adhesives, dispersion adhesives, hotmelt adhesives) or from the solid phase (adhesive films, laminate adhesives). In all of these types there is a liquid state during processing from which emissions are always a possibility due to the volatility of the basic polymer or other adhesive components. 

Adhesives are nonmetaUic substances used to join two surfaces by means of surface adherence (adhesion) and inherent strength (cohesion), DIN 16920. This definition of adhesives does not cover water glass adhesives, adhesive ceramics, or adhesive mortars. The substances used as adhesives are polymers that go through a liquid phase at least once (reactive adhesives) or more than once (hotmelts, thermally activated adhesives). The liquid phase can also be achieved by dissolution in suitable solvents (nonreactive adhesives). In dispersion adhesives, the polymer molecules are dispersed (finely distributed) in a liquid - usually water - whereby the polymer molecules themselves are not dissolved. Fig. 6. These adhesives are also known as water-based or aqueous adhesives. It must be remembered that solvents are contained in these adhesives in addition to the water. Genuine aqueous adhesives contain less than 5% solvents in the liquid phase. The dispersions crnitain, in contrast to the solute adhesive molecules, additional substances, disposal of which requires specific additional measures. Since the dispersions represent stable systems in water, the water-resistance of such adhesives is reduced. Their thermal and water resistance can be increased by additional crosslinking (usually with isocyanates). 

There many reasons to add plasticizers to the polyethylene formulations. Smaller amounts are added for conventional reasons, such as to make material more flexible. This includes applications in hotmelt adhesives and plasticization of pipe material. It is shown that up to 30 phr of plasticizer can be added to polyethylene. Small amounts of plasticizer are also needed to compatibilize different polymers or formulation components as well as to facilitate the biodegradative properties. ... 

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