Fast cure rate

Polyurethane adhesives are known for excellent adhesion, flexibihty, toughness, high cohesive strength, and fast cure rates. Polyurethane adhesives rely on the curing of multifunctional isocyanate-terrninated prepolymers with moisture or on the reaction with the substrate, eg, wood and ceUulosic fibers. Two-component adhesives consist of an isocyanate prepolymer, which is cured with low equivalent weight diols, polyols, diamines, or polyamines. Such systems can be used neat or as solution. The two components are kept separately before apphcation. Two-component polyurethane systems are also used as hot-melt adhesives. 

Radiation cure system. Other addition reaction cure systems that have emerged in recent years are the ultra-violet (UV) and electron beam (EB) radiation cure systems. The development of these systems has been prompted by the ever-increasing need for fast cure rates and low cure temperatures. The U V cure system... 

Two-part sprayable polyurethanes are used in the production of chemical-resistant paints and coatings. The polyurethanes can be let down in some solvent to ease in the spraying. Polyureas are becoming important in this section of the market because of their very fast cure rates. 

These resins act more as polyester resins than they do as epoxy resins. They are easily processed, have fast cure rates at room temperature, and can be cured with peroxides. They effectively wet out glass fiber reinforcement and cure quickly. Therefore, vinyl ester resins are often used in the manufacture of composites such as filament- wound and pultruded structures. 

Energy curable adhesives for use in flexible packaging based on ultraviolet or electron beam irradiation are in their infancy. The potential use of these types of adhesive is promising due to the fast cure rate (essentially full cure on irradiation and hence low risk of migratory components) and the potentially... 

Halogenation of saturated hydrocarbon polymers can hardly be controlled and is frequently assodated with chain degradation phenomena In contrast, the presence of randomly distributed olefinic unsaturations, allows selective halogenation reactions by adopting appropriate conditions. For instance, butyl rubber can be chiorinated or brominated in allylic positions and chloro-butyl or bromo-butyl rubber results The latter polymers are very interesting since they exhibit fast curing rates when sulfur and ZnO are introduced in the formulations. 

Water-industry sealants have a fast cure rate and the ability to accept early cyclic movement, even at low temperatures. They provide long-term performance under permanently immersed conditions and are resistant to anaerobic bacteriological conditions associated with sewage. 

The most important crosslinking agent for pressureless hot air vulcanization of silicone rubber is DClBP(Bis-2,4-dichloro-benzoyl-peroxide) (Fig. 14). It generates decomposition products, which are removed in a post-curing process with air blowing. This product provides the advantage of a fast cure rate and bubble-free cured transparent rubber. 

As expected, the more intense the light source, the faster the photocure. Cures in as short as 30 seconds have been obtained on a PPG Ultraviolet Processor. However, with this polymer system, UV radiation alone is not sufficient for fast cure rates. Both heat and light are required. This is demonstrated in Table IV. 

Microwave Fast curing rates (factor of 10) over forced convection heating. Reduced stress from CTE mismatched materials Cure schedules require optimization of many parameters. Specialized equipment... 

The type of elastomer will influence the rate of cure and the resultant crosslink network. Natural rubber tends to cure faster than SBR. Cure systems containing thiuram accelerators such as tetramethylthiuram disulfide will show short induction times and fast cure rates compared with a system containing diphenylguanidine. 

Chem. Descrip. Carboxyiated styrene-butadiene latex Uses Binder for nonwovens, textiles, froth coatings of upholstery fabrics Features Soft self-crosslinking exc. water and solv. resist., tensile str. good adhesion fast cure rate... 

CAS 1314-13-2 EINECS/ELINCS 215-222-5 Uses Aclivalor, reinforcer, hiding pigment for use in rubber (NR, SR, latex), paint, chemicals, stearate, resin, primer, and adhesives Features Med. to fast cure rate... 

Features Med. to fast cure rate med. surf, area Properties Wh. fine powd. odorless sp.gr. 5.6 Toxicology Nontoxic Z0C0 624 [ZOCHEM]... 

Improved versions of the reactive acrylics have been developed and are called "aerobic" acrylics (61,62). These aerobic acrylics have diminished sensitivity to air inhibition and can be cured between two surfaces, regardless of the presence or absence of air. The adhesives are low in odor, nonflammable, and low in toxicity. The fast curing rate, e.g., 10 to 60 seconds, and the solvent-diluted activator minimize the movements in the substrates prior to fixture. The compositions, as claimed in patents (66,67), contain an elastomer that is colloidally dispersed in a monomer or in a monomer/oligomer/polymer solution. On the general subject of the rubber-reinforcement of acrylics, Drake et al. have written a recent review (68). However, they emphasize nitrile rubbers. 

The main family of bioerodible polymers is represented by poly(alkylcya-noacrylate)s (PACA). These polymers have a long history since 1947 as adhesives, especially in areas where a fast cure rate is needed. Polymerisation of alkylcyanoacrylates (ACA) can be initiated in the presence of bases as weak as the hydroxyl ions of water. The propagation rate decreases when the size of the lateral alkyl chain increases. As polymerisation can be very fast, ACAs have been used as surgical glue, as tissue adhesive and for embolisation purposes. As shown in Section 4.4.6, ACAs have also been used extensively for preparing nanospheres and nanocapsules for drug delivery. 

Quaternary phosphonium salts such as the tetraalkyl and alkyl-triphenylphosphonium halides have been used as fast catalysts for curing of phe-nolics, carboxylic acid-terminated polyesters, or anhydrides with epoxies (126). Used in powder coatings, they showed good latency and fast cure rates at moderate temperatures. 

A filled, medium reactive, general purpose, thixotropic, orthophthalic resin offering a fast cure rate and good filler stability and designed for cold press moulding and RIM. 

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