Hot melt applications

Product Softening Point Hot Melt Application Temperature Polymer Tensile Strength (psi) Polymer (% Elongation)... 

Pressure-sensitive adhesives fall into three broad product categories water based, solvent based, and hot melt. Application areas tend to overlap, and all three types can be used in most of the application areas. Despite this overlap, tapes tend to be produced from solvent-based adhesives, while water-based adhesives are preferred for label stock. Hot melts are used in both applications. Pressure-sensitive tapes for a variety of uses, such as masking, packaging, and insulation, are the largest application area, followed... 

The plastics used in hot-melt applications are generally not newly developed materials. However, the combination of properly formulated resins and application equipment to handle these resins has contributed much to the success of hot-melt technology." While most hot-melt adhesives melt... 

We will study in detail all the hot melt applications in another chapter in Volume 4 of this Handbook. However, we briefly mention here the main equipment used for hot melt application. 

These systems are mostly used for hot melt adhesive powders, for instance for textile laminating, liners and we will study this in two other chapters Hot Melts Application and Textile Bonding in the future volumes of this Handbook. 

Electromagnetic hot melts are also used. Standard hot melt applicators dispense the hot melt between the two substrates to be bonded with their subsequent reactivation through an RF work coil. This permits maintaining the ultimate hot melt temperatures without heat losses due to open time and heat sink through the substrate. 

The chemistry and structure of the tackifying terpene resins are developed by E. Ruckel al. These resins, produced commercially from pine turpentine, since the mid-Thirties, are formulated with natural rubber to produce pressure sensitive adhesives. More recently, the scope of their use has been broadened by formulation with elastomers and waxes for hot melt applications. Empirical application tests have developed a broad knowledge of utility but little science or predictability. By use of sophisticated high polymer techniques, polymerization mechanisms are used to explain how the minor structural differences between the beta-pinene and dipentene resins suit these resins respectively for pressure sensitive and hot melt adhesive usage. Again for use application the critical aspects of the formulation are its adhesive and cohesive properties as demonstrated by tack, shear and peel properties. 

The ability to speed up packaging lines to achieve much greater productivity without increasing space requirements, by simply converting to hot melt adhesives from cold glues, was an economic bonus to many companies. Hot melt application equipment interchangeable with aqueous dispensers was developed by several companies, permitting relatively inexpensive conversions to the hot melt system. 

The cost of using hot melt adhesives has been lowered by the introduction of foamed hot melt applicators. This system introduces an inert gas into the adhesive prior to the point of discharge. By using the adhesive foam the amount of adhesive applied can be reduced as much as 50%, thus significantly reducing the cost of the adhesive required. The foam system can also result in a thinner glue line, which is very advantageous in certain end uses. 

These adhesives are available in several forms pellets, monofilament, ground resins, billets, and glue sticks. The pellets and ground resins can be applied with standard bulk hot melt applicators. The monofilaments, first developed by Bostik, are applied with specialized melting equipment. The billets are applied with modified bulk melt equipment which melts only the surface of the billet in contact with a heated... 

Hot melt applicators for melting polyamides are available from several suppliers, notably, Nordson, Meltex Corp., Bostik Fastening Systems Group, and Graco/LTI. 

The manufacturer of pressure-sensitive products should read the chapters Acrylic adhesives , Styrenic hot melts , Application equipment , Testing and laboratory equipment , etc. 

The total market is split into 35% reactive p., used as curing agent for epoxies, 30% in inks and 35% in hot-melt applications. 

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