Carboxylic rubbers

Carboxylic elastomers have been reinforced with cationic starch products.93 Compounds were prepared either by solution mixing followed by drying, or by using a torque rheometer. The addition of cationic starch significantly reduced the toluene solubility of the carboxylated rubber. Physical properties of these compounds were greater than compounds prepared with unmodified pearl starch. 

This chapter concludes with brief reference to carboxylated rubber latexes. Further information, with references, is available in a review by Blackley [27]. Carboxylated rubber latexes contain rubbery polymers which have been modified by inclusion of a small amount of a copolymerisable carboxylic-acid monomer in the emulsion polymerization system by which they were prepared. Typical carboxylic-acid monomers are acrylic acid (XI), methacrylic acid (XII) and itaconic acid (XIII). The most industrially-important rubber latexes of this type are the carboxylated styrene-butadiene rubber latexes. Also of considerable... 

Two general features of emulsion polymerization reaction systems for the production of carboxylated rubber latexes are of special interest The first b that the polymerization usually takes place under acidic conditions (c. pH 3-4) and not under the alkaline conditions which are usual for the production of non-functionalized synthetic rubber latexes. Polymerization is carried out under acidic conditions in order to encourage the carboxylic acid monomer to become copolymerized into the molecxiles of rubber being prcxluced. If the reaction is carried oui under alkaline conditions, then the carboxylic acid monomer is present mainly as a carboxylate salt which partitions strongly in favour of the aqueous phase If it polymerizes at all under these conditions, polymerization occurs mainly ir the aqueous phase of the reaction system, and the polymer molecxiles in whicl it becomes incorporated are far more hydrophilic than are the majority of the polymer molecxiles, which are produced in the latex particles. The requiremen... 

As the polarity difference between the two blocks increases, (xAB)cr the Krause (1969,1970) theory (see Section 4.7.1) will become smaller, or alternatively, phase separation will occur for shorter block lengths. A limiting case in this argument involves the carboxylic rubbers and ionomers, in which one block consists of isolated single salt (ionic) mers, incorporated in an otherwise hydrocarbon-type backbone. It should be emphasized that the ionic block length is one monomer unit long. Phase separation and formation of ionic clusters occurs because of the extreme difference in... 

Poly(carbon monoxide-co- polyolefin), a linear, alternating terpolymer ethylene-co- propylene-co-carbon monoxide Carboxylic rubber... 

In simple homopolymers and networks, ionic charges may be introduced for a variety of reasons. For example, introducing about 5% of sodium methacrylic acid into polyethylene produces ionomers, which are clear, tough plastics. When the Tg of the polymer is below ambient, materials known as carboxylic rubbers are formed. Anionic and cationic ion exchange resins have been known for a long time. ... 

The first completely synthetic resin, based on phenol and formaldehyde, was invented by Baekeland and others in the first decade of this century. " While the phenol-formaldehyde resins yielded excellent adhesives then as now, blends with carboxylic rubber, epoxy resins, neoprene, nitrile rubber, and other polymers Improved adhesive properties for various purposes. 

In the past, considerable industrial interest has been shown in solid carboxylated polymers such as carboxylated styrene-butadiene rubbers (l-9) However industrial interest is now almost exclusively with carboxylated polymers in latex form Furthermore, interest is principally in the latices of carboxylated rubber latices, and of these the carboxylated styrene-butadiene rubber latices are pre-eminent. Statistics recently published for the consumption of synthetic latices of all types in Western Europe over the period 1979-QO indicate that, on a basis of dry polymer, carboxylated styrene-butadiene types make up some QP/o of the total (10). 

Carboxylated rubber latices are commonly produced hy hatch emulsion polymerization. The reaction system comprises the monomers, water, surfactant, initiator, modifier and (usually) inorganic electrolytes. It is essential that polymerization takes place under acid conditions (typically pH ca.4) in order to ensure that the carboxylic acid monomer does become copolymerized in the main polymer molecule which is being produced. If the reaction is carried out under alkaline conditions, then the carboxylating monomer partitions strongly in the aqueous phase as the salt form if it polymerizes at all under these conditions, it is in the aqueous phase that it polymerizes, and the polymer chains in which it becomes incorporated will be far more hydrophilic than the majority of polymer molecules which are produced in the reaction system. In contrast to the production of, say, solid styrene-butadiene rubber by emulsion polymerization, where it is common practice to shortstop the reaction at ca. 65 conversion in order to prevent "undue branching and crosslinking within the polymer, reaction systems for the production of carboxylated latices by emulsion polymerization are usually taken to as near complete conversion as possible. 

PARTICULATE STRUCTURAL ADHESIVES USING CARBOXYLATED RUBBERS... 

Particulate structural adhesives have also been prepared by the combination of epoxy resins and elastomeric carboxylated rubber, Hycar 1072. The epoxy resins are milled into the rubber and then the curatives are added. The stock is sheeted from the mill and ground into a powder. The adhesives can be applied by electrostatic spraying, fluidized bed, or powder bed."" "... 

Brown, H. P., and Anderson, J. F., Adhesive Properties of Carboxylic Rubbers, unpublished paper presented at Gordon Research Conference on Adhesives, Aug. 1958. 

The structure and vulcanisation mechanisms of carboxylated rubbers in general are discussed, and results are presented of a study of the vulcanisation of carboxylated nitrile rubber using four different curing systems. The crosslink density, tensile and dynamic mechanical properties, stress relaxation and tear strength of vulcanised samples were investigated. 22 refs. 

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