Crosslinking binders

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... 

Back (10) has indicated that superior board performance is achieved with covalent bonding of the adhesive to the wood. A binder, then, must have at least the minimum number of reactive sites per molecule. If there is one or fewer such sites, then the lignin should behave as a filler, which may or may not be chemically bound to the resin. In the case of two reactive sites, a linear macromolecule is possible, or the lignin may be considered to behave as an extender for a resin. When three or more sites are available, crosslinking can occur and the lignin could then become a full partner in the crosslinked binder. One may project how the lignin could behave, once the reactive sites on the lignin molecule have been mapped. For this chapter, the interactive sites will be alcohols and benzyl alcohols, to simulate the reaction of PF resins with the carbohydrates in the wood. 

Linear GAP has a functionality of 2 and in order to achieve the desired level of mechanical properties, it must be raised by the addition of triols or crosslinked with triisocyanates to generate the desired extended polymeric matrix. Gas evolution is a serious problem during the curing of liquid GAP with isocyanates which react with moisture to give carbon dioxide. This carbon dioxide (C02) remains trapped in the voids of the crosslinked binder networks and results in decreased mechanical properties and performance. Some orga-nometallic compounds such as dibutyltin dilaurate (DBTDL) and triphenyl bismuth (TPB) are reported to suppress C02 formation and at the same time, accelerate the curing process [114]. 

With melamine or phenolic resins as crosslinkers binder no. 5 shows an attractive combination of good ED behaviour, good mechanical film properties and high bath stability. Its salt-spray resistance is comparable to that of a commercial LMPB system (no. 

Acralen. [Bayer] Self-crosslinking binder for textile industry. 

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