Polyamines temperature

Ambient-cure systems are often based on lower molecular-weight soHd epoxy resins cured with aUphatic polyamines or polyamides. Curing normally occurs at ambient temperatures with a working life (pot life) of 8—24 h, depending on the formulation. Epoxy—poly amine systems are typically used for maintenance coatings in oil refineries, petrochemical plants, and in many marine appHcations. Such coverings are appHed by spray or bmsh. These are used widely where water immersion is encountered, particularly in marine appHcations (see COATINGS, MARINE). 

This reaction is reported to proceed at a rapid rate, with over 25% conversion in less than 0.001 s [3]. It can also proceed at very low temperatures, as in the middle of winter. Most primary substituted urea linkages, referred to as urea bonds, are more thermally stable than urethane bonds, by 20-30°C, but not in all cases. Polyamines based on aromatic amines are normally somewhat slower, especially if there are additional electron withdrawing moieties on the aromatic ring, such as chlorine or ester linkages [4]. Use of aliphatic isocyanates, such as methylene bis-4,4 -(cyclohexylisocyanate) (HnMDI), in place of MDI, has been shown to slow the gelation rate to about 60 s, with an amine chain extender present. Sterically hindered secondary amine-terminated polyols, in conjunction with certain aliphatic isocyanates, are reported to have slower gelation times, in some cases as long as 24 h [4]. 

Two-component systems consist of (1) polyol or polyamine, and (2) isocyanate. The hardening starts with the mixing of the two components. Due to the low viscosities of the two components, they can be used without addition of solvents. The mass ratio between the two components determines the properties of the bond line. Linear polyols and a lower surplus of isocyanates give flexible bond lines, whereas branched polyols and higher amounts of isocyanates lead to hard and brittle bond lines. The pot life of the two-component systems is determined by the reactivity of the two components, the temperature and the addition of catalysts. The pot life can vary between 0.5 and 24 h. The cure at room temperature is completed within 3 to 20 h. 

Figure 1 Thermal oxidative breakdown of polyethylene (temperature 200°C P02 = 350 Tor stabilizer concentration 0.5 mass percent). 1-without stabilizer 2-CaO-6 3-polydii-minodiphenylmethane disulfide 4-polydiiminodiphenylsul-fon disulfide 5-polyparaoxydiphenylamine disulfide 6-po-lydimethylaniline disulfide 7-polyaniline disulfide 8-polydiiminodiphenyloxide disulfide 9-polythiosemicarbaz-ide disulfide 10-polyamine disulfide 11-polycarbamide disulfide 12-poly thiocarbamide disulfide 13-polyethylenedi-amine disulfide.

Polyamine disulphides are effective thermostabilizers of cured polyethylene up to 400°C. In presence of polyamine disulphides a decrease in gel fraction is one half as large as that of nonstabilized cured polyethylene over the temperature range from 350-380°C [46]. 

Aliphatic polyamines, amine adducts and polyamides react with epoxide resins at normal temperatures to give complexes with outstanding chemical resistance. Paints based on this type of reaction must be supplied in two separate containers, one containing the epoxide resin and the other the curing agent , the two being mixed in prescribed proportions immediately before use. 

Polybutadienes, polycaprolactones, polycarbonates, and amine-terminated polyethers (ATPEs) are shown in Scheme 4.4 as examples of other commercially available polyols. They are all specialty materials, used in situations where specific property profiles are required. For example, ATPEs are utilized in spray-applied elastomers where fast-reacting, high-molecular-weight polyamines give quick gel times and rapid viscosity buildup. Polycarbonates are used for implantation devices because polyuredtanes based on them perform best in this very demanding environment. Polycaprolactones and polybutadienes may be chosen for applications which require exceptional light stability, hydrolysis resistance, and/or low-temperature flexibility. 

A combination of aluminum chlorohydrate and a polyamine, such as poly (diallyldimethyl ammonium chloride), in aqueous solution is effective at elevated temperatures for an oil-in-water emulsion [787]. 

Nabeshima, Y., Ding, Z. L., Chen, G. H., Hoffman, A. S., Taira, H., Kataoka, K., and Tsuruta, T., Slow release of heparin from a hydrogel made from polyamine chains to a temperature-sensitive polymer backbone, in Advanced Biomaterials in Biomedical Engineering and Drug Delivery Systems (N. Ogata, et al., Eds.), pp. 315-316. Springer, Tokyo (1996). 

For polyamine-cured resin, recycle of presoaked epoxy also increased both impact strength and heat deflection temperature. For polyamide-cured resin, recycle also increased volume resistivity. Pre-soaked recycle dramatically increased adhesion to aluminum, especially in the anhydride system. 

A diesel fuel stabilizer containing a blend of amines, polyamines, and alkyl ammonium alkyl phosphate as specified under MIL-S-53021 is recommended for federal diesel fuel oil. This stabilizer is to be used at a treat rate of 25 lb/1,000 barrels. It is not intended for use in routine applications, but for situations where increased stability protection is required. Typical applications include fueled equipment undergoing long-term storage in a warehouse or depot, prepositioned equipment or equipment maintained in a high-temperature environment. 

Zytel Polyamine Stable to temperatures up to about 325°F (163°C) resistant to impact, deformation, and fatigue Fuel rails filter housings... 

Preparation of a Cured Epoxy Resin by the Room Temperature Reaction of Bisphenol A Diglycidyl Ether with Polyamines... 

The naturally occurring polyamine 3,3,3,3-pent (caldopentamine) has recently been isolated from high-temperature resistant bacteria (Thermus thermophilus).875... 

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