Carboxyl-terminated butadiene acrylonitrile CTBN copolymer

Fig. 13. TXT cure diagram temperature of cure vs. the times to phase separation (doud point), gelation and vitrification for a neat and two rubber-modified systems. of the neat system is also included. The systems studied were DER331/TMAB O, gelation , vitrificaticm modified with IS parts rubber per hundred parts epoxy 1) pr eacted carboxyl-terminated butadiene-acrylonitrile (CTBN) copolymer containing 17% acrylonitrile (K-293, Spencer Kellog Co.) A, phase separation , gelation , vitrification, and 2) polytetramethylene oxide terminated with anmiatic amine (ODA2000, Polaroid Corp.) A. phase separation O, gelation O, vitrification. (DER331/TMAB/ K-293 data from Ref. )...

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)...

In order to improve the internal stress performance even further or to provide toughness for potting and adhesive applications it is advantageous to introduce reactive additives to the basic epoxide compound formulation. One of the most popular additives that has found considerable use in this type of application is a rubber-like liquid copolymer known as carboxyl terminated butadiene/acrylonitrile (CTBN). The generalised molecular structure of this material is ... 

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

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. 

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

A 3300 molecular weight carboxyl terminated 80-20 butadiene-acrylonitrile random copolymer designated CTBN (I) (Figure 3). 

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).

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. 

However, newer adhesives systems having moderate temperature resistance have been developed with improved toughness but without sacrificing other properties. When cured, these structural adhesives have discrete elastomeric particles embedded in the matrix. The most common toughened hybrids using this concept are acrylic and epoxy systems. The elastomer is generally a amine- or carboxyl-terminated acrylonitrile butadiene copolymer (ATBN and CTBN). 

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 ... 

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). 

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

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). 

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