Acid functionalized rubber

Polymers can be modified by the introduction of ionic groups [I]. The ionic polymers, also called ionomers, offer great potential in a variety of applications. Ionic rubbers are mostly prepared by metal ion neutralization of acid functionalized rubbers, such as carboxylated styrene-butadiene rubber, carboxylated polybutadiene rubber, and carboxylated nitrile rubber 12-5]. Ionic rubbers under ambient conditions show moderate to high tensile and tear strength and high elongation. The ionic crosslinks are thermolabile and, thus, the materials can be processed just as thermoplastics are processed [6]. 

Interestingly, this same effect has been observed for the addition of a rubber toughening agent to ethyl cyanoacrylate-based adhesives, as was reported previously. The rubber must contain enough latent acid functionality on the polymer backbone or in an additive to inhibit the thermally activated decomposition of the alkyl cyanoacrylate adhesive polymer. 

Grafted Polymers. Due to the special chain structure ABS terpoly-mers have been widely modified by grafting vinyl monomers onto the main chain. We emphasize that the method how ABS itself is obtained is addressed sometimes as grafting styrene and acrylonitrile onto a butadiene rubber. Here we focus on grafting reactions on the ABS itself. Some examples of ABS grafted polymers are shown in Table 8.7. The pending acid functionalities may be allowed to react with amines and other compounds (45). 

The pH measurements were carried out in a 100-ml jacketed titration cell fitted with a magnetic stirrer and rubber stopper tttrou which were inserted nitrogen and buret delivery tubes and glass and calomel electrodes. A research pH meter was used the system was calibrated at pH 4 and 9.22. The ionic strength was 0.15 in all cases (KNO3). The temperature was held to 0.05° of the desired value. Each acid function was titrated with increments of 0.1000 M KOH, carbonate free."... 

Carbonated nitrile rubber (XNBR) incorporates up to 10% of a third comonomer with organic acid functionality. When compared to NBR, XNBR has improved abrasion resistance and strength. XNBR can be difficult to process, and it requires special formulation to prevent sticking to mixer surfaces and premature vulcanization. 

The book includes five chapters that mention the following topics Introduction of chemosensory effects and the properties and applications of stearic acid in food industry Functions of stearic acid in rubber industry Physicochemical properties and applications of stearic acid in biomedical sciences Practical use as a lubricant in tablets direct compression and the last topic is an overview on introduction and potential applications of deuterated hydroxystearic acids. 

PEST/PO blends have been compatibilized through graft copolymer formation by reaction of polyester carboxylic acid end-groups with pendent oxazoline groups on an appropriate PO. The copolymer contains a new esteramide linkage. Womer et al. (1997) have blended 0-20 parts oxazoline-functionalized rubbers containing more than one oxazoline group per chain with 100-80 parts acid-terminated PBT in... 

A polymer alloy was prepared by Lavengood, PateL and Padwa [6]. This alloy is comprised of ABS with polybutadiene rubber, a polyamide such as nylon-6 or nylon-11, and a compatibilizer. The polyamide and ABS are immiscible. The compatibilizer is selected in a fashion that it is either partially or completely miscible with the graft copolymer, and has acid functional groups that can be made to react with the end groups of polyamides. This can be a terpolymer of styrene, acrylonitrile, and maleic acid. The resulting polymer alloy has been a successful product in the commercial arena under the name of Triax 1000. The performance properties were a step change improvement. 

Core-shell impact modifiers have also been reported as impact modifiers for engineering polymers. MBS impact modifiers with a SBR core, a polystyrene middle layer and an outer layer of MMA copolymers with glycidyl methacrylate, acrylamide or methacrylic acid functional monomers were evaluated in PC/PBT blends [104]. Optimal results were obtained with 60 wt% SBR content in the MBS and a modest amoimt of a functional monomer in the MMA copolymer shell. Core-shell impact modification of polycarbonate [105] (PMMA grafted on poly(n-butyl acrylate) and PBT[106] (SAN grafted onto a butadiene based rubber) have been reported. A comprehensive review of core-sheU impact modification of various polymers (PMMA, PVC, PC, PBT, PET, polyamides, thermoplastic blends, thermosets) has been presented by Cruz-Ramos [107]. 

Carbon blacks are not simply carbon. Basic blacks have hydroxyl groups at the particle surfaces and acid blacks have carboxylic acid functionality. It has been shown that the mbber polymer forms strong secondary and primary covalent bonds with the carbon black, which accounts for its reinforcing ability. A wide variety of carbon blacks is available [5]. In addition to chemical functionality, they differ in factors such as particle size, degree of aggregation, and surface area, and different types of rubber polymers require particular kinds of black for optimum reinforcement. Silicone rubbers are sometimes reinforced with finely divided silica (Si02). 

Carboxylic acids. It has been shown that improved adhesion can be obtained in joints produced with solvent-borne polyurethane adhesives containing small amount of different carboxylic acids. These carboxylic acids can be aliphatic or aromatic, unsaturated or saturated, may contain one or more carboxylic acid functionalities, and have hydroxyl, carbonyl, or halogen groups. Fumaric and maleic acids are the most common carboxylic acids added to the solvent-borne polyurethane adhesives for the joining of SBR rubber sole. 

Polymers that contain carboxylic acid functionality, such as carboxylated nitrile rubber (XNBR), can also be cross-linked with a divalent metal oxide, either zinc oxide, zinc peroxide, or magnesium oxide. The organo-metallic cross-link supplements the traditional sulfur or peroxide generated cross-links to provide superior toughness and abrasion resistance. In XNBR, the amount of ZnO depends on its surface area, with 5 phr at 9 m /g surface area being used compared with 9 phr at 3.5 m /g surface area. Standard XNBR grades are best cured with zinc peroxide or low... 

Ionic polymers are a special class of polymeric materials having a hydrocarbon backbone containing pendant acid groups. These are then neutralized partially or fully to form salts. lonomeric TPEs are a class of ionic polymers in which properties of vulcanized rubber are combined with the ease of processing of thermoplastics. These polymers contain up to 10 mol% of ionic group. These ionomeric TPEs are typically prepared by copolymerization of a functionalized monomer with an olefinic unsamrated monomer or direct functionalization of a preformed polymer [68-71]. The methods of preparation of various ionomeric TPEs are discussed below. 

Weiss et al. [75] have synthesized Na and Zn salt of sulfonated styrene(ethylene-co-butylene)-styrene triblock ionomer. The starting material is a hydrogenated triblock copolymer of styrene and butadiene with a rubber mid-block and PS end-blocks. After hydrogenation, the mid-block is converted to a random copolymer of ethylene and butylene. Ethyl sulfonate is used to sulfonate the block copolymer in 1,2-dichloroethane solution at 50°C using the procedure developed by Makowski et al. [76]. The sulfonic acid form of the functionalized polymer is recovered by steam stripping. The neutralization reaction is carried out in toluene-methanol solution using the appropriate metal hydroxide or acetate. 

FIGURE 27.2 T-peel sfrength values of sulfuric acid-treated styrene-butadiene rubber (SBR)/polyurethane adhesive joints as a function of the immersion time in sulfuric acid. A = adhesion failure R = cohesion failure in the rubber. (From Cepeda-Jimenez, C.M., Pastor-Bias, M.M., Ferrandiz-Gomez, T.P., and Martm-Martmez, J.M., J. Adhes., 73, 135, 2000.)... 

A dusting agent which is soluble in rubber and thus does not impair the vulcanised bond between rubber components of a composite product. It is also an activator combining the functions of zinc oxide and stearic acid, of particular value in transparent rubbers since it does not produce the same opacity as zinc oxide. 

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