Elastomers rubber-fiber bonding

Naturally occurring fibers such as cotton, cellulose, etc., have short whiskers protruding from the surface, which help to give a physical bond when mixed with rubber. Glass, nylon, polyester, and rayon have smooth surfaces and adhesion of these fibers to the rubber matrix is comparatively poor. In addition, these synthetic fibers have chemically unreactive surfaces, which must be treated to enable a bond to form with the mbber. In general, the fibers are dipped in adhesives in the latex form and this technology is the most common one used for continuous fibers. The adhesion between elastomers and fibers was discussed by Kubo [128]. Hisaki et al. [129] and Kubo [130] proposed a... 

In order to be able to describe polymers and their composites which are used in the production of adhesives and sealants, a general classification of engineering polymers need to be considered first. The nature of a polymer defined as a plastic, an elastomer (rubber), or a fiber depends on the strength of its intermolecular bonds and molecular structure. At temperatures above their Tg, elastomers (rubbers) are typically noncrystalline polymers with... 

Unvulcanized rubber consists of a large number of flexible long molecules with a structure that permits free rotation about single bonds in the primary chain. On deformation the molecules are straightened, with a decrease in entropy. This results in a retractive force on the ends of the polymer molecules. The molecular structure of the flexible rubber molecules makes it relatively easy for them to take up statistieally random conformations under thermal motion. This property is a result of the weak intermolecular attractive forces in elastomers and distinguishes them chemically from other polymers which are more suitable for use as plastics or fibers. 

Adhesion. Commercially available one- or two-coat adhesive systems produce cohesive rubber failure in bonds between ethylene-acrylic elastomer and metal (16). Adhesion to nylon, polyester, or aramid fiber cord or fabric is greatest when the cord or fabric have been treated with carboxylated nitrile rubber latex. 

CONTEXT The distinction between plastics that bend and stretch (elastomers such as rubber) and plastics that bend but don t stretch (fibers such as nylon) is that the dipole-dipole attraction gives fibers great tensile strength without the rigidity that we associate with covalent bonds. Nylon is composed of polyamide chains, bound by the dipole-dipole attraction of the C=0 bond fx 2.3 D) and the N—H bond fjL 1.3D), forming a hydrogen bond. 

Frequently it is necessary to combine materials having quite dissimilar solubility parameters, and often differing in modulus as well. An important example, the manufacture of tires, is discussed in the chapter, Bonding Textiles to Rubber. Use is made of a hybrid adhesive, RFL, containing heat-resistant resorcinol-formaldehyde for good attachment primarily to the polar, high modulus fiber, plus an elastomer of moderate solubility parameter, butadiene-styrene-vinyl pyridine terpolymer latex, mainly for the rubber. 

Extensive reviews on short fibers-reinforced elastomers have been published by Goettler and Shen, ° and more recently by Rajeev. Table 7.11 is a list of selected published works on natural fiber-filled rubber composites, sorted by rubber type. Only vulcanizable rubbers were considered in preparing the table thermoplastic rubber and rubber-plastics blends were omitted. As can be seen most grades of conventional elastomers have been considered with quite a large variety of natural fibers. Natural Rubber, SBR, and EPDM compounds have received much attention, as expected with respect to their industrial importance. A bonding system is us in most cases, with resin types (i.e. resorcinol-formaldehyde, resorcinol-hexamethylenetetramine, sil-ica-resorcinol-hexamethylenetetramine) the most frequent ones. 

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