Crosslinked polymeric binder

The dimensional stability of the propellant grain is the result of the chemically crosslinked polymeric binder. Many of the mechanical properties of the final cured propellant will be dictated by binder characteristics. Another important consideration is the effect of filler, owing to its presence as well as its degree of interaction with the binder. 

Min BS, Park YC, Yoo JC. A study on the triazole crosslinked polymeric binder based on glycidyl azide polymer and dipolarophile curing agents. Propell Explos Pyrot 2012(1) 59-68. 

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]. 

Polymeric binders based upon a vinyl acetate and ethylene backbone incorporating a self crosslinking monomer have been widely used in the nonwoven industry (3). 

J.J. Rabasco, J.R. Boylan, D. Sagl, and R.B. Jones, Self-crosslinking vinyl acetate-ethylene polymeric binders for nonwoven webs, US Patent 7 485 590, assigned to Wacker Chemical Corporation, February 3,2009. 

Composite rocket propellants are two-phase mixtures comprising a crystalline oxidizer in a polymeric fuel/binder matrix. The oxidizer is a finely-dispersed powder of ammonium perchlorate which is suspended in a fuel. The fuel is a plasticized polymeric material which may have rubbery properties (i.e. hydroxy-terminated polybutadiene crosslinked with a diisocyanate) or plastic properties (i.e. polycaprolactone). Composite rocket propellants can be either extruded or cast depending on the type of fuel employed. For composite propellants which are plastic in nature, the technique of extrusion is employed, whereas for composite propellants which are rubbery, cast or extruded techniques are used. 

Diammonium phosphate and ammonium sulfamate are used at 15 % solids addon and function as condensed phase flame retardants, not only by crosslinking but also by dehydrating cellulose to polymeric char with reduced formation of flammable by-products (Fig. 8.6). The water insoluble ammonium polyphosphate is an effective flame retardant and is added to coatings and binder systems, for example for pigment printing. Ammonium bromide is applied at 10 % solids add-on and is effective in the gas phase. 

Hydroxyl-terminated polydiene resins gelled by the reaction with orthosilicate esters have increased thermal stability. These polymeric gels, like silicone rubbers, exhibit outstanding electrical properties. The polymeric gels crosslinked at ambient temperature are castable as self-curing liquids. For example, they are used as binders for rocket solid fuels, in coatings for pipes, tanks, etc. They can be mixed with rubbers. 

Summary The stepwise synthesis of the polycarbosilanes (Cl2SiCH2CH2) (5) and (H2SiCH2CH2)n (6) are described. On addition of catalytical amounts of transition metal complexes to polymer 6 dehydrogenation occurs and a further crosslinked carbosilane (8) is obtained by formation of new silicon-silicon bonds. Pyrolysis of carbosilane 8 produces a black ceramic material, containing P-SiC together with carbon. The ceramic yield after pyrolysis of 8 is approximately four times the yield obtained when 6 is employed as the starting material. From polymeric 8 preceramic fibers are accessible subsequent pyrolysis yields ceramic fibers. Moreover, the carbosilane 8 can be utilized as a binder for ceramic powders. 

Figure 3.73. Volume size of voxels assuming ellipsoid structure as a function of the inverse of the scan speed. The voxels were obtained by TP initiated crosslinking radical polymerization of acrylates in the presence of poly (styrene-co-acrylonitrile) as binder and an amino-substituted distyrylbenzene as TP active initiator using a pulsed laser (150-fs pulses at a 76-MHz repetition rate or 85-fs pulses at a repetition rate of 82 MHz). (From Ref. [133] with permission of the Technical Association of Photopolymers, Japan.)...

Photopolymerizable layers usually consist of a polymeric binder, such as poly(methyl methacrylate) or poly(vinylbutal) a photopolymerizable monomer, such as methylene glycol bisacrylate or polyethylene glycol bismethacrylate a thermal stabilizer, />-methoxyphenol a photoinitiator, such as an alkyl anthraquinone and a dye, such as a cyanine dye. On exposure to light in an imagewise manner the exposed areas are photohardened by formation of caged-type photopolymerized, two-dimensional crosslink structures. 

The crosslinked image areas are then insoluble in solvents. The soluble noncrosslinked areas can be removed with solvent or chemical action to provide relief patterns or images. Alternatively, the change in thermal properties on exposure can be utilized. The crosslinked areas are less easily thermally softened than are the unexposed areas. Thus the unexposed and thermally softened areas can be transferred by pressure to a receiving sheet to give a positive image. Proper choice of the polymeric binder and the monomeric acrylate or methacrylate permits control over the ultimate physical properties of the exposed and unexposed photo-... 

Solid state irradiation of -aminobenzoylazide in the absence of a binder leads to formation of the polyurea. Attempted formation of such a polymer within a matrix of a soluble polymeric binder such as poly-(vinylbutal) led to insolubilization in the exposed areas. Hydrogen abstraction can simultaneously produce crosslinking of the binder. 

Uses Polymerization/copolymerization thermally crosslinkable paint resin adhesion promoter binder for textiles, paper adhesives floor care prods. dental prods. base material for other methacrylates Properties Pt-Co 25 max. clear liq. pungent odor misc. with water ( > 24 C) m.w. 86.1 sp.gr. 1.015 vise. 1.38 mPa s (20 C) vapor pressure 0.8 mbar b.p. 161 C solid, pt. 15.8 C flash pt. 65 C ref. index 1.432 99.5% min. purity 0.02% max. water... 

Uses Binder, film-former in paints (printed circuit board coatings, coil, container, conosion-protection, marine, metal, plastics, sealers, tarp, wood varnishes), printing inks (screen printing), primers (adhesion pro-motion/corrosion protection), ceramic compds., sealers, heat-sealable lacquers, two-pack paints, resinous/polymeric food-contact coatings reactive resin in two-pack systems, e.g., crosslinked with melamine/phenolic resins... 

Uses Initiator of low temp, free radical polymerization multifunctional crosslinker for exterior durable coatings Features Latent initiator highly flexible Regulatory DOT nonregulated SARA nonreportable Properties Colorless clear liq. insol. in water sol. in polar org. soivs. such as acetone sp.gr. 1.06 dens. 8.7-9.0 Ib/gal vise. 120-300 cps vapor pressure < 0.1 mm Hg (140 F) b.p. 750 F flash pt. (PMCC) 110 C 98% resin solids Use Level 10-30% of binder system... 

The most promising method of obtaining polymeric materials is by the use of so-called hybrid binders. These constitute polymeric composite materials in which crosslinking indicates the heterogeneity of the distribution of the system components determined by thermodynamic... 

Bifunctional monomers, such as A-A, B-B and A-B, yield linear polymers. Branched and crosslinked polymers are obtained from polyfunctional monomers. For example, polymerization of formaldehyde with phenol may lead to complex architectures. Formaldehyde is commercialized as an aqueous solution in which it is present as methylene glycol, which may react with the trifunctional phenol (reactive at its two ortho and one para positions). The type of polymer architecture depends on the reaction conditions. Polymerization imder basic conditions (pH = 9-11) and with an excess of formaldehyde yields a highly branched polymer (resols. Figure 1.8). In this case, the polymerization is stopped when the polymer is still liquid or soluble. The formation of the final network (curing) is achieved during application (e.g., in foundry as binders to make cores or molds for castings of steel, iron and non-ferrous metals). Under acidic conditions (pH = 2-3) and with an excess of phenol, linear polymers with httle branching are produced (novolacs). 

---