Polysulfides blends

Epoxy-Liquid Polysulfide Blends Epoxy resins in combination with liquid PSs appear to possess many added advantages as the elastomeric PS segments in epoxy chains impart permanent flexibility [18]. Epoxy-liquid PS blends have been reported as binders for Army illuminating formulations [8]. Similarly, novolac epoxy-liquid PS blends have been reported for inhibition of composite propellants [19]. 

Butyl formal, butyl ether, and polysulfide blend Carboxyl terminated polybutadiene and epoxy blend... 

Fig. 2, Representative bend specimens after testing at 76°K (a) butyl formal, butyl ether, and polysulfide blend (b) fluorosilicone (c) polysulfide (d) silicone (e) polyurethane (f) epoxy (g) epoxy-silicone and (h) carboxyl terminated polybutadiene and epoxy blend. 

The monosulfides of the alkaline earth metals crystallize in the rock salt (MgS, CaS, SrS, BaS) and zinc blende (BeS) structures. BaS is insoluble in water, while the other monosulfides are sparingly soluble but hydrolyzed on warming (except MgS that is completely hydrolyzed). The monoselenides are isomorphous to the sulfides. The monotellurides CaTe, SrTe, BaTe adopt the rock salt stmcture, while BeTe has the zinc blende and MgTe the wurtzite structure. Alkaline earth polysulfides may be prepared by boiling a solution or suspension of the metal hydroxide with sulfur, e.g.,... 

Twenty-four horns after several barrels of the dyestuff were bulked, blended and repacked, spontaneous heating occurred. This was attributed to aerobic oxidation of excess sodium polysulfide used during manufacture. 

The ground mixture is heated to about 750 °C under reducing conditions, normally in a batch process. This can be done in directly fired kilns with the blend in lidded crucibles of controlled porosity, or muffle kilns. The heating medium can be solid fuel, oil, or gas. The sodium carbonate reacts with the sulfur and reducing agent at 300 °C to form sodium polysulfide. At higher temperatures the clay lattice reforms into a three-dimensional framework, which at 700 °C is transformed to the sodalite structure, with entrapped sodium and polysulfide ions. 

A family of elastomeric foams has been developed by Rand 129) for use as stress relief coatings on electronic components in encapsulated electronic assemblies. Polysulfide, silicone and polyurethane elastomers blended with glass and phenolic microspheres have been used to formulate syntactic foams (Fig. 10) These foams are used to minimize the stress caused by differential thermal expansion between the component and the encapsulant. 

Titanates have been instrumental in the bonding of fluorinated resins to packaging films, poly(hydantoin)—polyester to polyester wire enamel, polysulfide sealant to polyurethane (a phosphated titanate is recommended), polyethylene to cellophane using a titanated polyethylenimine, and silicone mbber sealant to metal or plastic support using polysilane (Si—H) plus polysiloxane (Si—OR) and titanate as the adhesive ingredients (450—454). Polyester film coated first with a titanium alkoxide, then with a poly(vinyl alcohol)—polyethylenimine blend, becomes impermeable to gases (455). 

Alloyed blends consisting of epoxy-phenolic, epoxy-nylon, and epoxy-polysulfide adhesives... 

For adhesive systems, the liquid epoxy resins most widely used with LP-3 polymers are liquid unmodified and diluent-modified bisphenol A resins and liquid blends of bisphenol A and bisphenol F resins. Solid bisphenol A, multifunctional, and aliphatic diepoxy resins have also been used. Ratios of liquid polysulfide polymer to epoxy are in the range of 1 2 to 2 1. The effect of various degrees of polysulfide on cure properties of a DGEB A epoxy is shown in Table 7.7. An increase in elongation and impact strength is the result of increased amounts of the liquid polysulfide polymer. 

Another common method of flexibilizing epoxy adhesives is by blending the primary epoxy resin with other, more elastic polymers. Epoxy-nylon, epoxy-polysulfide, and to a certain extent epoxy-urethane hybrids use such a mechanism to provide flexibility. These flexibilizers are important additives for epoxy adhesives even though they may reduce certain... 

The feedstocks (straight-mn naphtha (SRN) and a blend of SRN and hydrocracked naphtha) and hydrotreated products were analysed by ASTM methods for density, carbon, hydrogen, hydrocarbon and boiling point distribution. Total sulfur was determined by ASTM D-4045 method, mercaptan sulfur by the potentiometric method (ASTM D-3227 and UOP-212), disulfides by the UOP-202 method, polysulfides by polarography [1], and elemental sulfur by the UOP-286 method. The Perkin-Elmer gas chromatograph (Model 8700), equipped with a flame photometric detector (GC/FPD) and a DB-1 fused silica capillary column (30 m x 0.53 mm), was used for identification of individual sulfur compounds [2-6]. The sensitivity of the GC/FPD technique was maximized by optimizing the gas flow rates and temperature programming as presented elsewhere [1]. 

Mercuric sulfide, HgS, is precipitated from aqueous solutions as a black, highly insoluble compound. The solubility product is 10 54, but the sulfide is somewhat more soluble than this figure would imply because of some hydrolysis of Hg2+ and S2- ions. The black sulfide is unstable with respect to a red form identical with the mineral cinnabar and changes into it when heated or digested with alkali polysulfides or mercurous chloride. The red form has a distorted sodium chloride lattice with Hg—S chains similar to those in HgO. Another form, occurring as the mineral metacinnabarite, has a zinc blende structure, as have the selenide and telluride. 

The ESD behavior can be provided by blending in a flexible-chain polymer with an active -OH or -SH group, viz. polyvinyl alcohol (PVAl), ethylene-vinylacetate (EVAc), polyvinylphenol (PVPh), a copolymer of ethylene oxide and epi-chlorohydrin (EO-CHR), maleated copolymer, aliphatic polysulfides, etc. These low performance resins have been incorporated into a variety of alloys and blends (see Table 1.79). 

The polysulfide resin called for in these specifications is a dichloroethylformal polysulfide in the 1000 molecular v eight range. The accelerators are tertiairy amines consisting of a blend of 2, 4, 6-tridimethyl-aiainomethyl phenol (DKP-30), and dime thy laminoe thy 1 phenol (EMP-IO). 

Cheng and English edited ACS symposium series which covers the solution and solid state NMR investigations for dendrimers, cellulose, polyurethane, polyolefins biopolymers, copolymers and so on. Spiess described a historical overview of role of NMR spectroscopy in polymer science. Newmark summarizes the two dimensional and pulsed gradient diffusion NMR experiments and their applications to polymers Shit et al. reviewed the analysis of polymer molecular weight and copolymer composition by NMR. Sasanuma summarized the the analysis of polyethers and polysulfides by NMR and theoretical calcula-tions Ardelean et al described the principle and its applications of diffusion studies by NMR. Roy et al summarized the structural analysis of Novolak resins by multidimensional NMR. Reviews about NMR study of surfactant polymer blends and the structural elucidation of supramocules are published. 

Polysulfide rubbers posses outstanding resistance to solvents. They exhibit excellent resistance to oils, gasoline, and aliphatic and aromatic hydrocarbon solvents, very good water resistance, good alkali resistance, and fair acid resistance. FA polysulfide rubbers are somewhat more resistant to solvents than ST rubbers. Compounding of FA polymers with NBR will provide high resistance to aromatic solvents and improve the physical properties of the blend. For high resistance to esters and ketones, neoprene W is compoimded with FA polysulfide rubber to produce improved physical properties. 

Chem. Descrip. Blend of liq. polysulfide and epoxy resin Uses Flexibilized coating for use in sec. containment, drum storage, and truck unloading areas, and in fuel storage tanks Features Abrasion and chem. resist. 

Epoxy-polysulfide adhesives are suitable for used down to -100°C and lower temperatures. Some blends have been used down to liquid nitrogen temperatures of -198.5°C. The maximum service temperature is about 50°C to 71-82°C. The resistance of bonds to moisture is quite high, but may deteriorate if the bonds are stressed. Some formulations will corrode copper adherends. 

Polymer blends are often used in adhesive formulations where properties associated with rigid polymers (high temperature resistance, chemical resistance, etc.) must be obtained along with properties associated with tough, elastic polymers (impact strength, high peel strength, etc.). Examples of these adhesive systems are nylon-epoxy, phenolic-nitrile, epoxy-polysulfide, epoxy-nitrile, and epoxyurethane. 

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