Hotmelts adhesive

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. 

The reactive hotmelt adhesives retain a high level of flexibility and dynamic load-bearing capacities even after crossUnking and are used to join plastics to one another as well as to wood (furniture industry), glass (construction industry), aluminum (sandwich elements), and painted surfaces. Typical applications include window casement sheathing, foil laminations, clip fasteners, bookbinding, textile... 

RHM adhesives have the following advantages over the standard hotmelt adhesives ... 

Hotmelt adhesives are thermoplastics that are processed free of solvents in the melted state and are therefore known as hotmelts. Since the adhesives are 100% solids, no volatile components can be released. No incineration and/or ventilation systems are required to dispose of the solvents. These adhesives are used to fill larger gaps and therefore often function as both adhesives and sealants. Foamed hotmelt adhesives comprise a special category They are capable of filling large gaps with very little material while still bonding the substrates. 

The process time is determined by the technical parameters heatup, application, and cooling It is very short compared to the process times of reactive adhesives. Processing is done with so-called sticks, spreadable powders, extrusions, nets, or films. Hotmelt adhesives in the form of films in particular are among the heat-activated or heat seal adhesives. In film and textile composites the term used is laminate adhesives. 

In hotmelt adhesive guns, the adhesive granulates or sticks are melted, and then transported in liquid form through heated tubes for applicatimi. Hotmelt adhesives are applied in dot patterns, in the form of beads, by spraying or by means of rollers in the transfer method. The adhesive is applied continuously in timed cycles, resulting in highly variable adhesive patterns and variable adhesive layer thicknesses. In laminating systems, both Uquid hotmelt adhesives and adhesive films can be processed. 

A typical cycle for hotmelt adhesives is Melting Transport of melt to application location (possibly distributiOTi) Covering of the structural components to be joined Cooling. The relationship between viscosity and temperature is decisive at every single process step, so that these relationships should be familiarized for all hotmelt adhesives. 

Hotmelt adhesives are suitable for adhesive joining of clips, lamination of films, leather and textiles and bonding of films, foams, textiles, and wood. Resistance to hot water and steam is a problem that arises most particularly in the field of textile bonding. This problem was solved using hotmelt adhesives based on copolyamides. 

The primary components used to make polyamide-based hotmelt adhesives are copolyamides with PA 12 and so-called polyamide resins. 

Ethylene vinyl acetate copolymers Copolymers made from ethylene and vinyl acetate (E/VA) are among the most important hotmelt adhesives. The vinyl acetate content of the copolymer varies between 10 and 50%. The density increases in proportion to the VAC content. Other possible components include resins, waxes,... 

The polyolefinic hotmelt adhesives are characterized by aging stability, i.e., the laws of adhesion and flexibility and the appearance of yellowing are not as pronounced as in the TPEs. 

Thermoplastic elastomers (TPE) Styrene-butadiene-styrene (SBS) and styrene-isoprene-styrene (SIS) block copolymers represent primary materials for other hotmelt adhesives. They are characterized by long open times, high elasticity levels, good spring qualities and a lasting stickiness, so that precoated surfaces always retain some of the qualities of PSAs. The melting temperatures of these adhesives are particularly low at about 65°C, so that they can be used for thermally sensitive materials (foams, fleeces, thin films). 

N-ethylbenzenesulfonamide - from zero up to the stoichiometric equivalent of amide units and 20 wt% in hotmelt adhesive ... 

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. ... 

CoUano, 2013. Moisture Curing PUR Hotmelt Adhesive for Textiles and Technical Textiles. 

For example, hotmelt adhesives are 100% solid thermoplastic compounds that are solids at room temperature, but they are changed to liquid when heated to the melting temperature. When applied, hotmelts bond and cool rapidly. To make EVA based hotmelt adhesives, mixing process at high temperature is essential. To reduce the thermal degradation of hotmelt adhesives, 1-2 parts of a phenolic antioxidant by weight were used as a thermal stabilizer (Park et al. 2003 Park et al. 2006). 

Principle of the Allover method using induction heating (IH) and hotmelt adhesives (Sekine et al. 2009)... 

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