Carboxyl terminated nitrile

Composite Particles, Inc. reported the use of surface-modified rubber particles in formulations of thermoset systems, such as polyurethanes, polysulfides, and epoxies [95], The surface of the mbber was oxidized by a proprietary gas atmosphere, which leads to the formation of polar functional groups like —COOH and —OH, which in turn enhanced the dispersibility and bonding characteristics of mbber particles to other polar polymers. A composite containing 15% treated mbber particles per 85% polyurethane has physical properties similar to those of the pure polyurethane. Inclusion of surface-modified waste mbber in polyurethane matrix increases the coefficient of friction. This finds application in polyurethane tires and shoe soles. The treated mbber particles enhance the flexibility and impact resistance of polyester-based constmction materials [95]. Inclusion of treated waste mbber along with carboxyl terminated nitrile mbber (CTBN) in epoxy formulations increases the fracture toughness of the epoxy resins [96]. 

Liquid diglycidyl ether of bisphenol A Carboxyl-terminated nitrile rubber... 

Conversely, the brittleness of cured epoxy resins can be ameliorated by copolymeiizing with flexible curing agents. The two most popular types are carboxyl-terminated nitrile rubber and mercaptan-terminated polysnlflde rnbber oligomers (Fig. 3.35). 

HOC(CH2CH=CHCH2)m(CH2(j H)nCOH Carboxyl-Terminated Nitrile Rubber... 

Flexibilized epoxy resins are important structural adhesives [69]. Liquid functionally terminated nitrile rubbers are excellent flexibilizing agents for epoxy resins. This liquid nitrile rubber can be reacted into the epoxy matrix if it contains carboxylated terminated functionalities or by adding an amine terminated rubber. The main effects produced by addition of liquid nitrile rubber in epoxy formulations is the increase in T-peel strength and in low-temperature lap shear strength, without reducing the elevated temperature lap shear. 

ATBN - amine terminated nitrile rubber X - Flory Huggins interaction parameter CPE - carboxylated polyethylene d - width at half height of the copolymer profile given by Kuhn statistical segment length DMAE - dimethyl amino ethanol r - interfacial tension reduction d - particle size reduction DSC - differential scanning calorimetry EMA - ethylene methyl acrylate copolymer ENR - epoxidized natural rubber EOR - ethylene olefin rubber EPDM - ethylene propylene diene monomer EPM - ethylene propylene monomer rubber EPR - ethylene propylene rubber EPR-g-SA - succinic anhydride grafted ethylene propylene rubber... 

Carboxylic functional polyester curing agents, 10 401-406 Carboxyl ion system, 19 193 Carboxyl-terminated butadiene nitrile, rubbers and, 10 376-375 Carboxymethyl cellulose (CMC),... 

Epoxy-nitrile Nitrile-epoxy adhesives are composed of solid epoxy resin modified with carboxyl-terminated butadiene nitrile (CTBN) copolymer. The CBTN is introduced into die epoxy resin at elevated temperatures. The modification provides toughness and high peel strength without sacrificing heat and chemical resistance. The film adhesives are widely used in the aerospace industry in the construction of jetliners. 

The epoxy-nitrile adhesives were introduced commercially in the late 1960s. They consisted primarily of DGEBA epoxy resin modified with carboxyl-terminated butadiene nitrile (CTBN) rubber. These first nitrile copolymers were available from B.F. Goodrich under the trade name of Hycar. The most convenient form of epoxy nitrile adhesive, especially when one is bonding large parts (aircraft structures), is a supported film. However, solvent solutions of epoxy-nitrile adhesives have also been commercially available. 

In the mid-60 s carboxyl-terminated polybutadiene/acrylo-nitrile (CTBN) liquid polymers were introduced for the purpose of epoxy resin modification. These telechellc polymers are essentially macromolecular diacids. They offer processing ease (and therefore advantage) over the solid carboxylic nitrile elastomers. It is no surprise that the epoxy prepreg industry (adhesive and non-adhesive varieties) found the liquid and solid carboxylic nitrile elastomer species useful together in processing liquid and lower molecular weight solid epoxy resins where elastomer modification was needed. 

Later, in 1974, amine reactive versions of the liquid nitrile polymers (ATBN) were issued, thereby offering another way to introduce rubbery segments into a cured epoxy resin network. References are cited which provide detailed discussions of nitrile rubber, carboxylic nitrile rubber and both carboxyl- and amine-terminated nitrile liquid polymers (1-4). Table I illustrates CTBN and ATBN products structurally. Table II provides properties for typical solid carboxylic nitrile elastomers. 

Wide-ranging documentation exists which covers modification of epoxy resins using carboxyl-terminated polybutadiene/acrylo-nitrile liquid polymers in which addition esterification (alky-... 

Apart from carboxyl and amine-terminated nitrile rubbers, the rubbers having other end groups like amine [12-14], mercaptan [15, 16] hydroxyl [17] and epoxy [18,... 

Fig. 5.80 An FESEM (5 kV) image of a whitened region from a three point bend fracture surface of epoxy modified with carboxyl-terminated butyl nitrile rubber (CTBN) particles. (From O. L. Shaffer, impublished [376].)...

Abbreviations HIPS, high-impact polystyrene ABS, acrylonitrile-butadiene-styrene graft copolymer EPDM, ethylene propylene-diene copolymer CTBN, carboxyl terminated butadiene nitrile telomer M = 5000 g/mol) PC, polyearbonate SBS, styrene-butadiene-styrene triblock copolymer SIS, styrene isoprene styrene tribloek copolymer SEBS, SBS with hydrogenated center block PU, segmented (block copolymer) polyurethanes PDMS, poly(dimethyl siloxane) FIFE, polytetralluoroethylene. 

The Goodrich product might be made using 4,4 -azo-his-(4-cyano-n-amyl alcohol) as initiator, since the nitrile band at 2330 cm" is present in their material. However, a strong ester band is also present, pointing to the possibility that the product is made by addition of an epoxide to a carboxyl-terminated polybutadiene. 

The thermosetting films are employed for metal-to-metal bonding in aircraft, as well as less demanding appliance, electrical, and automotive requirements. These adhesives are hybrids designed to provide an optimum combination of shear strength, elongation, and heat resistance. Nitrile-phenolic and epoxy-nitrile are the leaders, followed by vinyl butyral-phe-nolic, epoxy-nylon, and epoxy-phenolic. The nitrile rubber in the epoxy-nitrile is a carboxyl-terminated butadiene-nitrile polymer which reacts with the epoxy at the elevated cure temperature. 

One of the largest areas of use of nitrile rubber modified epoxy systems is in the printed circuit board area. A number of systems have been described that are composed of carboxyl-containing nitrile rubber such as Hycar 1072 mixed with epoxy resin. " The low molecular weight functionally terminated nitrile rubbers have also found significant application in this area. Other workers have found useful a system that combines a high molecular weight nitrile rubber with the liquid functionally terminated materials. Finally, other references describe the use of non carboxylated nitrile rubbers in circuit board applications. 2 ... 

The liquid nitrile rubbers can be reacted into the epoxy matrix in one of two ways. If a carboxyl terminated material is used it is normally adducted or prepolymerized with an epoxy resin prior to formulating. The resulting epoxy adduct is then placed in the epoxy component of the composition. A second method of incorporating liquid nitrile materials would be to use an amine terminated rubber. In this case the material contributes amine reactivity and functions as a part of the hardener system. These materials were primarily developed to form stable admixes with amine containing epoxy hardeners. 

Recently Sahoo and Bhowmick [75] synthesized hydroxyl-terminated POSS in their laboratory starting from (3-aminopropyl) triethoxysilane (APS) and phenylglycidylether (PGE) and used it as a curative in carboxylated nitrile mbber (XNBR). This has been a newer class of material where the nanofiller simultaneously cures the mbber and promotes solvent resistance, as well as mechanical and dynamic mechanical properties. Table 3.3 illustrates some of these findings. 

Very interesting transformations were reported in terminal alkynes RC=CH (R = alkyl, aryl, alkoxy, carboxylate, etc.). They react readily with nitric acid, in aqueous nitromethane (1 1) and in the presence of catalytic amounts of tetra-butylammonium tetrachloroaurate to give 3,5-disubstituted isoxazoles 15 in 35% to 50% isolable yield (92). The reaction might proceed via a nitrile oxide intermediate by attack of an electrophile (AuCh or H+) and of a nucleophile (N02 ) on the triple bond to form a vinyl nitrite, which is converted to a nitrile oxide by the action of gold(III) or of nitric acid (Scheme 1.8). 

The terminal carhanionic sites of "living" polymers can be reacted with various electrophilic compounds of yield (o)-functional polymers. Esters, nitriles, acid chlorides, anhydrides, lactones, epoxides, benzyl or allyl halogenides have been used for their high reactivity with metal organic sites, to yield appropriate functions.2 Carbon dioxide is also an efficient reagent to yield terminal carboxylic functions. 

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