Polyurethane PUR Adhesives

The PUR (or PU) adhesives also cure according to the described mechanism of polyaddition. The reactive group at the molecules of resin component A has the following chemical structure and is called an isocyanate group  

The molecule arrangement arising due to the chemical reaction of A and B is called the urethane group. If several of these groups are contained in a polymer molecule, macromolecules, called polyurethanes, will develop, which, after the curing reaction, will finally represent the adhesive layer. 

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The reduced equilibrium moisture content of heat-treated wood can influence the hardening of adhesives that need water for the curing reaction. This is significant for 1-component polyurethane (PUR) adhesive, which cures slower when bonding heat-treated wood with a smaller content of hydroxyl groups than non-treated wood... 

In Europe the term multilayer board includes cross-laminated timber elements used for construction parts in buildings and shuttering boards. Both these types of boards are mainly produced with MUF adhesives in gluing processes with relatively long pressing times or in processes with high temperatures. Polyurethane (PUR) adhesives are already in use as an alternative to MUF adhesives for production of building elements whereas EPI adhesives are in the introduction phase. 

For the last 10 years, an increasing portion of glulam beams produced in Europe for load-bearing timber structures has used one-component polyurethane (PUR) adhesives because of productivity requirements and environmental issues. These... 

Most of the glued components produced in Europe for non-structural purposes such as joinery use urea-formaldehyde (UF), poly (vinyl acetate) (PVAc) or polyurethane (PUR) adhesives. These adhesives must meet the performance requirements specified in EN 204 (2002) [15] for thermoplastic adhesives or EN 12765 (2002) [16] for thermosetting adhesives when tested in accordance with the following test methods ... 

This chapter introduces readers to the fundamentals of polyurethane chemistry, the basics of polyurethane adhesives, their applications and test standards. The chapter will also highlight relevant developments that have led formulators to create and tailor-make many polyurethane (PUR) adhesives and sealant products. 

Diisocyanates are an important class of chemicals of commercial interest, which are frequently used in the manufacture of indoor materials. such as adhesives, coatings, foams and rubbers (Ulrich, 1989). In some types of particle board, the diisocyanates have replaced formaldehyde. Isocyanates are characterized by the electrophilic -N=C=0 group, which can easily react with molecules containing hydroxy groups, such as water or alcohols. On hydrolysis with water, primary amines are formed, while a reaction with alcohols leads to carbamates (urethanes). Polyurethane (PUR) products are then obtained from a polyaddition of diisocyanate and diol components. Compounds commonly used in industrial surface technology are 4,4 -diphenylmethane diisocyanate (MDI) and hexamethylene diisocyanate (HDI). The diisocyanate monomers are known as respiratory sensitizers and cause irritation of eyes, skin and mucous membrane. Therefore, polyisocyanates such as HDI-biuret and HDI-isocyanurate with a monomer content <0.5 % are used for industrial applications, and isocyanate monomers will not achieve high concentrations in ambient air. Nevertheless, it is desirable to measure even trace emissions from materials in private dwellings. 

Reactive adhesives for elastic bonding are available as one-part and two-part systems, based on polyurethane (PUR), polysulphide, silicone or silane-terminated polymers, such as PUR-Hybrids and Modified Silicones (MS). These adhesive systems can he applied cold or warm or mixed with a water-based Booster component. 

For more informations about PUR adhesive and sealants, our read s may refer to the chapter Chemistry of Polyurethane adhesives and sealants in Volume 1 of this Handbook. 

Apart from the development of polyurethane adhesives and sealants with isocyanate reactive groups, a new type of silane-terminated polymer adhesive has been developed called Polyurethane (PUR)-Hybrids. They and modified silicones (MS) and provide the benefits of ... 

Polyurethane adhesives are produced in many grades such as one-component, two-component, dispersion and solvent based, and hot melted for use in different application areas. PUR adhesives have a good adhesion to wood, metal and plastics and find, therefore, end use in many industrial applications. Some applications outlined by sector are presented in this section. 

Depending on their use and characteristics, solvent or solventless polyurethane based adhesives are available and can also be customised for special packaging requirements. Some typical uses for one-component PUR adhesives are for adhesion of shopping bags, printed films, and adhesives for snack food bags. These are especially suitable for these applications mainly because they are solvent free, moisture curable, and easy to apply. 

PUR adhesives are also used for the bonding of interior materials of automobiles such as door trims, door centre panels, headlining and dash boards that are composed of at least two or more materials. Other polyurethane adhesives such as INSTA-GRIP [48] are used to attach fibreglass liners to trailers. The required properties are their initial adhesive strength, and heat resistance as well as their easy and quick application. 

Ultraviolet curing UV curing adhesives use ultraviolet light to initiate curing. This allows a permanent bond to develop without any need for heating. UV curable adhesives use various chemical systems, which include acrylics and acrylates, epoxies, polyurethanes (PUR), polyesters, silicones, vinyl and vinyl esters Aaylics are the most common components of UV curable adhesives. 

Elastic adhesives are usually produced on a polyurethane (PUR) basis, which have elongations up to 400%. One-component polyurethane systems cure with atmospheric moisture relatively slow and are therefore less sensitive to moisture. Due to its simple processing, 1-component polyurethane systems have gained market share increasingly (Brunner 1996). 

In a typical operation, PVC powder compound is metered into a form that has been machined to a high finish to represent the desired part surface, then heated to a temp-eramre at which the compound will sinter and partly fuse, while sufficient rotation is applied to obtain a uniform coating of the inside of the form. The latter may be, in fact, the same form previously used to rotomold PVC plastisol. The polyurethane (PUR) component may be foamed within the form or, more often, prepared previously, placed in the form, and fusion of the PVC, with resultant high PUR adhesion, then completed. ... 

Stenzler conducted instrumented impact tests of laminates with soft polymer interlayers have been conducted on three-layered samples consisting of a PMMA front, a polymer interlayer or adhesive, and a PC layer. The inner layers were either polyurethane (PUR) or polyacrylate. Strain rates on the order of 100 s at impact velocities 12 and 22 m/s were achieved using a gas gun. The interlayers increased impact resistance by increasing energy dissipation. 

Based on the numbers in Figures 1 and 2, by 1985 RIM and RRIM will require approximately 50 M lbs. of monomeric MDI, which is about one-third of the monomeric MDI supply in 1985 (Table IX based on 20-25% of 85% nameplate capacity, excluding ARCO capacity, = 137-171 M lbs. monomeric MDI). This will leave about 100 M lbs. of monomeric MDI for cast elastomers, thermoplastic polyurethanes, shoe soles, semi-rigid foams, and some adhesives and sealants, a monomeric MDI supply which should be more than sufficient for these applications. As RRIM grows, a need for capacity expansion can be seen in the late 1980 s. No effects on the market will be seen from PUR-SMC until after 1985, and at the present time meaningful projections are impossible. 

Tafigel PUR 50 [Munzing Chemie GmbH King Ind.j Chem. Descrip. Polyurethane polymer in water Uses Associative thickener, rheology control agent, vise, builder, stabilizer for aq. systems for indoor and outdoor paints, latex and anticorrosive paints, syn. resin-bound renderings, adhesives, and paste fillers Features Solv.-free... 

Kasobond Polyurethane elastomers for adhesives, PUR Lu-KasPolym. Chemie... 

One-component Epoxy/PUR hybrid adhesive Combination and mixture of polyurethane and epoxy resin, where the epoxy group reacts with the latent hardener at high temperature... 

The world production of polyurethane was about 16 billion pounds per year in 2010 to make PUR products in rubber, plastics, adhesives, sealants, fabrics, coatings, and both rigid and flexible foams. Over one-half of all polyurethane production goes into the manufacture of foam. Of that quantity, one-half is used to make flexible foam while the remainder is used to produce rigid foam. However, only about 800 million pounds of this production is used globally for high-performance rubber applications. 

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