Acrylonitrile copolymer , CTBN butadiene

Piperidine and carboxyl terminated butadiene acrylonitrile copolymer (CTBN) at 75 °C. 

Effect of Molecular Configuration of Elastomer. The extent of the impact and strength improvements of ERL-4221 depends on the chemical structure and composition of the elastomer modifier. The data shown in Table I indicate that the carboxyl terminated 80-20 butadiene-acrylonitrile copolymer (CTBN) is the most effective toughening and reinforcing agent. The mercaptan terminated copolymer (MTBN) is considerably less effective as far as tensile strength and heat distortion temperature are concerned. The mercaptan groups are considerably less reactive with epoxides than carboxyls (4), and this difference in the rate of reaction may influence the extent of the epoxy-elastomer copolymerization and therefore the precipitation of the rubber as distinct particles. 

The separate phases will be rich in one component but may have the other present as a minor component. In order to control compatibility the elastomer may have reactive end groups to enhance interfacial adhesion. A common example in epoxy-resin technology is the carboxy-terminated butadiene-acrylonitrile copolymer (CTBN). The structure is shown in Scheme 1.47. In this resin the solubility in the epoxy resin is conferred by the acrylonitrile group, and an increase in the fraction present decreases the upper critical solution temperature, with 26% acrylonitrile conferring total miscibility of CTBN with a DGEBA-based epoxy resin (Pascault et al, 2002). 

The incorporation of elastomers into epoxy resins has been an active area of research over the past decade (1-11). The primary reason for this interest has been the improved toughness of the modified materials. We have limited our work to the carboxy-terminated butadiene-acrylonitrile copolymers (CTBN) produced by... 

Synonyms Acrylonitrile-butadiene copolymer, carboxyl-terminated Butadiene-acrylonitrile copolymer carboxylated Butadiene-acrylonitrile copolymer, carboxyl-terminated Carboxylated butadiene-acrylonitrile copolymer CTBN... 

It is obvious from these data that CTBN (the carboxyl terminated butadiene-acrylonitrile copolymer) is the most effective modifier, and therefore it was selected for further study. As the concentration of the elastomer was increased to levels up to 100 parts, the impact also increased. The data in Table II show that the room temperature impact of ERL-4221 increased from 40 inch-lbs to greater than 320 inch-lbs by adding 100 phr or 33 wt % of CTBN. At very low temperatures ( —160°F) the impact of the system modified with 60 parts, or 23 wt %, of CTBN was 120 inch-lbs. These impact improvements appear to be directly proportional to the concentration of the elastomer modifier. 

Materials. Hycar CTBN is a registered trade name of a carboxyl-terminated, liquid copolymer of butadiene and acrylonitrile (B. F. Goodrich Chemical Co.). For most purposes it can be represented structurally as ... 

Liquids, butadiene-acrylonitrile copolymers (Hycar ATBN or CTBN, B.F. Goodrich)... 

Thus, with two equations and two unknowns, a unique solution to X and Y can be calculated. Carboxy-terminated copolymers of butadiene and acrylonitrile (CTBN) can be incorporated into the epoxy resin through a simple esterification reaction. One equivalent of carboxylic acid is esterified by one equivalent of epoxide. This reaction is again catalyzed by triphenylphosphine. Since, for our reactions, the limiting reagent in the esterification is the CTBN elastomer, the product is an elastomer capped with an epoxy resin. The epoxy terminated rubber is then capable of reacting in the usual manner with curing agents or in the previously discussed advancement reaction (Reaction Scheme 2). 

Fig. 13. Experimental CPC (A) and calculated binodal (broken curve) and spinodal (dotted curve) curves for a binary system composed of a DGEBA-based epoxy monomer (M = 479 gmol ) and a carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) (Reprinted from Polymer, 30, D. Verchere, H. Sautereau, J.P. Pascault, S.M. Mos-chiar, C.C. Riccardi, R.J.J. Williams, Miscibility of epoxy monomers with carboxyl-terminated butadiene-acrylonitrile random copolymers, 107 -115, Copyright (1989), with kind permission from Butterworth-Heinemann journals, Elsevier Science Ltd, The Boulevard, Langford Lane, Kidlington 0X5 1GB, UK)...

Chen and Jan [133] showed that bimodal distributions could be obtained by using two different rubbers as modifiers of a DGEBA-based epoxy resin cured with piperidine. The rubbers were two acrylonitrile-butadiene copolymers (CTBNs), with different AN content, i.e. 18 and 26%. The miscibility with the epoxy resin (and the corresponding cloud-point conversion) increased with the AN content. Therefore, when 10 wt% of CTBN (26% AN) was used as modifier, a high concentration (Cp == 13.4 pm ) of small particles (D = 0.2 pm) was obtained. When the same amount of CTBN (18% AN) was used as modifier. 

CTBN Butadiene acrylonitrile copolymer with a, co — carboxyl groups... 

Carboxyl-terminated copolymer of butadiene and acrylonitrile CTBN, Goodrich company... 

Kunz and coworkers [161,162] found for CTBN- and amine-terminated copolymer of butadiene and acrylonitrile (ATBN)-modified epoxies that, once a volume fraction of about 0.1 had been achieved in the polymer, further increase in volume fraction resulted in only minor increase in the value of fracture energy. The apparent discrepancy can be attributed to the use of matrices with different inherent ductility, curing conditions and test conditions employed [163,164]. Fracture energy in rubber-toughened epoxy is dependent on the test temperature and test rate [164—166]. The fracture energy increases with increase in the test temperature and decreases in test rate below the T. ... 

Carboxy-terminated butadiene acrylonitrile random copolymer (CTBN)... 

To the vinylester resins, thixotropic agents are added, for example silica fume (silicon dioxide in microspheres, which is a by-product of the glass industry), to obtain a behaviour adequate to their use also in open moulds. In addition, to improve their toughness, CTBN polymers (carboxyl-terminated copolymers of butadiene and acrylonitrile) are widely employed as reactive modifiers. This occurs since the CTBN-modified vinylester oligomers act as compatibilizers for blending additional butadiene copolymer (Burchill and Pearce, 1996). 

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. 

Figure 2 The chemical structure of a carboxyl-terminated copolymer of butadiene-acrylonitrile (CTBN).

Further toughening of VERs modified with a CTBN elastomer by introducing an epoxy-terminated butadiene-acrylonitrile copolymer diluted with a styrene monomer (Hycar ETBN 1300x40 from BF Goodrich) was presented [69]. The improvement of toughness achieved by the incorporation of the CTBN elastomer (Table 21) extends the range of VER applications from corrosion resistant equipment to automotive, marine and infrastructure markets. 

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