Crosslinked binders, chemistry

Chemistry of Propellants Based on Chemically Crosslinked Binders... 

Chemistry of Polysulfide Polymers. Propellant chemistry based on chemically crosslinked binders had its beginning at the Jet Propulsion Laboratory in the winter of 1946 when potassium and/or ammonium perchlorate were mixed into Thiokol LP-3 polysulfide liquid polymer, to which had been added an oxidative curative, p-quinone dioxime. This polysulfide polymer, as described by Jorczak and Fettes (13), is prepared... 

Post-crosslinkable and substrate reactive polymers are widely used to Improve water and solvent resistance, strength, substrate adhesion and block resistance In binders, adhesives and coatings. The surprisingly rich chemistry of a new class of functional monomers (eg. 1 and 2) related to standard amide/aldehyde (amlnoplast) condensates, but which eliminate aldehyde emissions, was elucidated by monomeric model and mechanistic studies and discussed In the preceeding paper (1). Results with these monomers In copolymer systems are reported here. 

A hydrocarbon prepolymer containing terminal carboxyl groups (28) is available to the propellant chemist. These polymers were synthesized to eliminate some of the variables found in the copolymers. The carboxyl groups can be made of the same types with like reactivity. These linear non-branched polymers impart greater extensibility to elastomeric formulations. The chemistry in propellants is similar to the random functionality polymer. As 20 years of the chemistry of crosslinked propellant binders is reviewed, one familiar with the art cannot fail to predict solid propellant formulations using these polymers tailored to the specific requirements of the solid rocket design with the confidence that any discipline of science can be practiced. 

In commercial use, easy-care and durable press finishes are frequently combined with other finishes to provide additional properties such as water and oil repellency, flame retardancy, soil release and the like. Often the combination of another finish with the cellulose crosslinking finish will result in a more durable effect from the first finish. Combination with pigment printing is very common because of similar chemistry to cellulose crosslinking agents and binders and the similar application conditions. 

Polysiloxanes. Siloxane rubbers are readily cured by heating in the presence of an appropriate peroxide and the technology is well-established (26). Indeed, this crosslinking chemistry has recently been extended into ceramic applications (27). Vinyl-substituted siloxanes were found to be very effective binders for SiC powder. With only about 1 wt% 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (Lupersol 101), the [(MeSiOi 5)o.5o(PhSiOi 5)0.25 (CH2=CHMe2SiOo.5)o.25] polysiloxane cured to an infusible solid after one hour at 180 C (27). Subsequent pyrolysis gave P-SiC, and dense ceramic monoliths could be prepared using these polymer systems as SiC binders. 

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