Styrene lattices, butadiene

The most common adhesive system used for bonding continuous fibers and fabrics to rubber is resorcinol-formaldehyde latex (RFL) system. In general, RFL system is a water-based material. Different lattices including nitrile and SBR are used as the latex for the adhesive system. 2-Vinylpyridine-butadiene-styrene is the common latex used in the adhesive recipe. RFL system is widely being used in tires, diaphragms, power transmission belts, hoses, and conveyor belts because of its dynamic properties, adhesion, heat resistance, and the capacity to bond a wide range of fabrics and mbbers. 

The spin-lattice relaxation process is usually exponential. Theoretically, the effect of spin-diffusion, characterized by the coefficient D (order of 1(T12 cm2 s 1), has an influence on T, relaxation times when ix > L2/D, where Lis the diffusion path length. NMR studies of model systems f6r rubber networks, based on a styrene-butadiene-styrene block copolymer (SBSy, in which styrene blocks act as a crosslink for polybutadiene rubber segments of known and uniform length, indicate that spin diffusion operating between PS and PB phases causes a lowering of Tg for the PS component in SBS (as compared to the pure PS) and hindering of the motion of the PB component (as compared to the pure PB)51). 

In copolymers such as styrene-butadiene-styrene the nature of the phase separation is such that eyki (r) is a periodic function of r with the symmetry of the phase lattice - that is, the long-range translational order of the phases. 

Emulsion polymerization is the most important process for production of elastic polymers based on butadiene. Copolymers of butadiene with styrene and acrylonitrile have attained particular significance. Polymerized 2-chlorobutadiene is known as chloroprene rubber. Emulsion polymerization provides the advantage of running a low viscosity during the entire time of polymerization. Hence the temperature can easily be controlled. The polymerizate is formed as a latex similar to natural rubber latex. In this way the production of mixed lattices is relieved. The temperature of polymerization is usually 50°C. Low-temperature polymerization is carried out by the help of redox systems at a temperature of 5°C. This kind of polymerization leads to a higher amount of desired trans-1,4 structures instead of cis-1,4 structures. Chloroprene rubber from poly-2-chlorbutadiene is equally formed by emulsion polymerization. Chloroprene polymerizes considerably more rapidly than butadiene and isoprene. Especially in low-temperature polymerization emulsifiers must show good solubility and... 

Table 14.6 illustrates typical improvements noted in epoxy hybrid formulations with vinyl chloride, acrylic, and styrene butadiene lattices. Tensile strengths of cured, latex-saturated paper substrates are listed in absolute numbers while those of latex-epoxy hybrids are listed as percent increases in tensile strength over that of the latex alone. The mechanisms believed responsible for these improvements are (1) cocuring of the epoxy group with carboxyl and amine functional groups present on the latex backbone and/or (2) homopolymerization of the epoxy catalyzed by the tertiary amine included in some hybrid formulations. 

It has an NiAs-type structure (Fig. 15-5), and the isolated methyl groups are presumably in the lattice as the pyramidal CHJ ion.35 Sofiium amd potasstuirralkyl5 can be used for metallation reactions- for example, in eq. 6-2. They can also be prepared from Na or K dispersed on an inert support material, and such solids act as carbanionic catalysts for the cyclization, isomerization or polymerization of alkenes. The so-called alfin catalysts for copolymerization of butadiene with styrene or isoprene to give rubbers consist of sodium alkyl (usually allyl) and alkoxide (usually isopropoxide) and NaCl, which are made simultaneously in hydrocarbons.33... 

Figure 5.19 Small-angle neutron scattering intensity obtained with a styrene-butadiene diblock copolymer having spherical butadiene microdomains. The peaks at very small q are due to a body-centered cubic lattice structure of ordered microdomains. The solid curve is the calculated intensity of independent scattering from solid spheres of mean radius 124 A. (From Bates etal.34)...

An isothermal morphology diagram of poly(styrene-fe/oc -butadiene) is shown in Fig. 19 as a function of molecular weight and copolymer composition the classic morphologies include spherical microdomains (0< a<0.15) packed in a body-centered cubic lattice, hexagonally packed cylindrical microdomains (0.15 <( a-0-3), and alternating lamellae of approximately symmetric diblocks (0.3 <0 -0-5). Sever-... 

Alkane sulfonates are applied in a widespread manner in emulsion polymerization. They are used as processing aids, in particular in the emulsion polymerization of vinyl chloride, vinyl acetate, styrene and acrylonitrile. Because they possess no double bonds, alkane sulfonates do not act as radical chain stoppers. Well-known lattices derived from emulsion polymerization are poly(vinyl chloride), ethylene-vinylacetate copolymers, polyacrylates, and butadiene and chloroprene rubbers. Alkane sulfonates also offer good stabilizing effects in lattices against coagulation by fillers. 

Stretching (GR-S, the co-polymer of butadiene and styrene) have a low strength unless they are mixed with carbon black. Obviously, the snapping of the chain molecules into the lattice is necessary to make the chains cohere sufficiently. On the other hand, the percentage of crystallites should not be too large, otherwise the material becomes hard and loses its rubbery properties. Polyethylene, which in the unstretched condition is from 55 to 75% crystalline, surpasses the tolerable limit. The fair average seems to be about 30%, which can be concluded from the unique mechanical properties of natural rubber, which crystallises to this extent on stretching. 

Latex la- teks [NS latic. latex, from L. fluid] (1835) (pi lattices or latexes) n. (1) An emulsion of a polymeric substance in an aqueous medium. (2) The sap of the hevea (rubber) tree and other plants, or emulsions prepared from the same. Latices of interest to the coatings and plastics industry are based mainly on styrene-butadiene co-polymers, polystyrene, acrylics, and vinyl polymers and co-polymers. (3) Fine dispersion of rubber or resin, natural or synthetic, in water the synthetic is made by emulsion polymerization. Latex and emulsion are often used synonymously in the paint industry. Emulsified monomers once polymerized become solids or plasticized gel particles and not emulsions but aqueous suspensions. Lovell PA, El-Aasser MS (eds) (1997) Emulsion polymerization and emulsion polymers. John Wiley and Sons, New York. Martens CR (1964) Emulsion and water-soluble paints and coatings. Reinhold Publishing Co., New York. VanderhofF JW, Gurnee EE (1956) Motion picture investigation of polymer latex phenomena. TAPPI 39 (2) 71-77. VanderhofF JW, Tarkowski HL, Jenkins MC, Bradford EG (1966) Theoretical considerations of the interfacial forces involved in the coalescence of latex particles. J Macromol Chem 1 (2) 361-397. 

Systems where the interaction between the end blocks is intermediate, the interactions between the adjacent blocks form stractures between those observed in the type II frustrated and the nonfrustrated systems. Stractures observed include alternating spheres on a BCC lattice, core-shell gyroid, core-shell cylinders, perforated lamellar, and pillared lamellar. Examples of such experimental systems are poly(styrene-b-isoprene-b-ethylene oxide),poly(styrene-b-butadiene-b-2-vinylpyridine) poly(styrene-b-isoprene-b-2-vinylpyri-... 

The thermal stability of NR and carboxylated styrene butadiene rubber (XSBR) lattices and their blends were studied by thermogravimetric methods by Stephen et The thermal degradation and ageing properties of these individual lattices and their blends were investigated with special reference to blend ratio and vulcanization techniques. As already described, as the XSBR content in the blends increased, their thermal stability was also found to increase. Among sulphur and radiation-vulcanized samples, radiation cured possessed higher thermal stability due to the higher thermal stability of carbon carbon crosslinks. 

R. Stephen et al. also studied the effect of microfillers on the thermal stability of NR, carboxylated styrene-butadiene rubber (XSBR) lattices and their 70/30 NR/XSBR blend. Microcomposites of XSBR and their blend were found to be thermally more stable than unfilled samples. ... 

Fig. 5.46 A transmission electron micrograph of an osmium tetroxide stained thin section of a poly(styrene-butadiene) diblock copolymer (16.1 wt% polybutadiene) shows the (100) projection of a body centered cubic lattice. (From Kinning et al. [214] reproduced with permission.)...

Early morphological studies to determine the nature of multiphase polymers and blends were reviewed by Folkes and Keller [363]. Many studies were of extruded block copolymers of materials such as SBS where the dispersed phase, an unsaturated rubber stained with OSO4 (see Section 4.4.2), was observed in the form of spheres, cylinders, or lamellae [364]. An excellent example is shown in a TEM micrograph of a thin section of a poly(styrene-butadiene) diblock copolymer, stained with OSO4 [365], which depicts the (100) projection of a body centered cubic lattice (Fig. 5.79). 

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