Hardening accelerators

In order to obtain a sufficient rate of cure at moulding temperatures it is usual to add about 0.2-2.0% of a hardener (accelerator). This functions by decomposing at moulding temperatures to give an acidic body that will accelerate the cure rate. A very large number of such latent acid catalysts have been described in the literature, of which some of the more prominent are ammonium sulphamate, ammonium phenoxyacetate, ethylene sulphite and trimethyl phosphate. 

The additives used for lacquer manufacture are composed of processing aids like hardening accelerators, flow agents, crosslinking agents and others like plasticisers, fillers and if necessary pigments. 

The kinetics of the cocondensation of monomethylolphenol model compounds and urea under alkaline conditions is reported by Pizzi et al. [173] and Yoshida et al. [174]. The same kinetics but under acidic conditions is described by Tomita and Hse [166,170,175]. The interaction of esters and copolymerized urea on the fast advancement and hardening acceleration of low condensation alkaline PUF resins is reported by Zhao et al. [117,172]. 

NORDTEST NT Build 442. Concrete, Hardened Accelerated Chloride Penetration, Espoo (1995). 

The calcium formate belongs also to the hardening accelerators [79]. This admixture is available as a waste in the production of pentaeritrite (polyhydroxyl alcohol). However, the effect of formate is less pronounced than the effect of chloride (Fig. 4.30). 

Chem. Descrip. Uncatalyzed mercaptan polymer Uses Epoxy hardener, accelerator tor amides, amines, and amido-amines in conventional and high-solids applies., fast-set concrete adhesives, castings, potting, laminates Features Requires amine catalyst tor activation Properties Gardner 2 max. color sp.gr. 1.15 dens. 9.6 Ib/gal vise. 100-150 poise gel time 4.5-6.5 min (30-50 g) After 7 day 25 C cure tens, str. 5900 psi elong. 3.75% flex. str. 10,000 psi 100% solids Capcure 40 sec HV [Cognis/Coatings Inks]... 

Chem. Descrip. Mercaptan polymer precatalyzed, accelerated Uses Epoxy hardener, accelerator in concrete adhesives, grouts, mortars, and coatings co-curative improves bond to glass and metal Features Fast cure eliminates induction times of polyamides and amido-amines... 

Unfortunately, solidified TS runners, flash, and defective parts cannot be recycled as they are with TPs. Some operations can use this material as a filler after it has been granulated but in practically all molding plants using TS, the material is lost and has to be considered in the part cost. One should consider using cold runners with TSs. Materials must be of a type that will permit their use for example, the time cycle should permit material to remain in the fluid state. As different hardeners, accelerators, and so on, can be used, it is practical to use cold runners. They have limited use in TM but are used more widely in IM. 

Control over the quantity and type of catalyzers, hardeners, accelerators, and inhibitors allows for matrices with very short polymerization periods (in the order of a few minutes) even at room temperature or, vice versa, very long periods (in the order of several hours) at high temperatures, depending on the needs of the composite. 

Alkanolamines are used as cross-linking and hardener accelerators in epoxy resins applications. Improved thermal and oxidative stability of polyvinyl alcohol, poly(phenylene ether), polystyrene, polypropylene, and polyethylene polymers are achieved by the addition of small amounts of the alkanolamines. Diethanolamine and morpholine act as initiators for the preparation of poly (alkyl methacrylate) in bulk or solution polymerization. The ethanolamines are efficient initiators for the preparation of polyvinyl chloride. Alkanolamines promote cross-linking of styrene copolymers with polystyrene or polyvinyl alcohol. Addition of alkanolamines to phenolic formaldehyde or urea formaldehyde resins affords improved electrical properties and increased water solubility. 

Curing reactions of alicyclic polyamines with epoxy resins occur easily enough to allow carrying out at room temperatures. However, aromatic polyamines, acid anhydrides and phenol compounds usually need hardening accelerators, since their curing reactions require long times, even at elevated temperatures. Table 3 summarizes the general characteristics of these hardeners. 

Co-hardener/accelerator to adjust, if necessary, the cure temperature to that which is specified. 

Various additives catalysts, hardeners, accelerators and inhibitors to alter curing characteristics, silver metal flakes for electrical conduction and aluminum oxide to improve thermal conduction. 

Patent Number US 5684202 A 19971104 TERTIARY AMINES, A PROCESS FOR THEIR PREPARATION AND THEIR USE AS HARDENING ACCELERATORS... 

The present invention relates to novel tertiary amines derived from bisphenols, diepoxides and aromatic secondary amines, to a process for their preparation and to their use as hardening accelerators for ethylenically unsaturated cold hardenable acrylic and polyester resins. 

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