Composites Resin toughening

Nelsen, S., Golder, M. and DeStio, P., Method and compositions for toughening polyester resins, US Patent 6020414 (to Hoechst Celanese Corporation, Somerville, NJ), 2000. 

Table 3.2 Compositions of Toughened DuPont Delrin Acetal Resins [1]...

Another approach for toughening UP and VE resins which has had success with epoxy resins is the use of liquid rubber (or elastomer) additives. The chief benefit of emplojdng liquid rubbers (LR) versus a flexibilized resin is that decreases in hardness, stiffness and heat-deflection properties can be minimized. During cure, the liquid rubber phase separates from the resin and is concentrated in a particulate phase. Very little of the rubber remains in solution with the cured resin so the resin s heat deflection temperature is for the most part unaffected. The toughness of the two-phase, or composite, material will be a function of the microstructure, which in turn will depend on processing and cure conditions. The subject of epoxy resin toughening is covered in separate articles in this book. 

Rubber modifier for impact-resistant plastic Degradative plastics composition resin Zinc salt derivative for toughening polystyrene film... 

In 1966, a patent was granted to Seibert (B. F. Goodrich) which covered the preparation of carboxyl terminated liquid polymers. These polymers have been used in adhesives and composites as toughening agents, mainly with epoxy resin based systems. 

Her-Der Wu, Chen-Chi M. Ma and Char-Ming Lin, Processability and properities of phenoxy resin toughened phenolic resin composites . Journal of Applied Polymer... 

Studies of the particle—epoxy interface and particle composition have been helphil in understanding the mbber-particle formation in epoxy resins (306). Based on extensive dynamic mechanical studies of epoxy resin cure, a mechanism was proposed for the development of a heterophase morphology in mbber-modifted epoxy resins (307). Other functionalized mbbers, such as amine-terminated butadiene—acrylonitrile copolymers (308) and -butyl acrylate—acryhc acid copolymers (309), have been used for toughening epoxy resins. 

Blends of isobutylene polymers with thermoplastic resins are used for toughening these compounds. High density polyethylene and isotactic polypropylene are often modified with 5 to 30 wt % polyisobutylene. At higher elastomer concentration the blends of butyl-type polymers with polyolefins become more mbbery in nature, and these compositions are used as thermoplastic elastomers (98). In some cases, a halobutyl phase is cross-linked as it is dispersed in the polyolefin to produce a highly elastic compound that is processible in thermoplastic mol ding equipment (99) (see Elastomers, synthetic-thermoplastic). ... 

Crivello, J.V., Electron beam curable epoxy compositions, US Patent 5,260,349, 1993. Janke, C.J., Dorsey, G.F., Havens, S.J. and Lopata, V.J., A toughened epoxy resin system and a method thereof, US Patent 5,726,216, 1998. 

Garg A.C. and Mai Y.W. (1988a). Failure mechanisms in toughened epoxy resin - A review. Composites Sci. Technol. 31, 179-223. 

Fig. 8.2. Composite mode I interlaminar fracture toughness, G[, as a function of respective neat resin toughness, G] ( ) Kim et al. (1992) (O) from Russell and Street (1987) ( ) toughened thermosets and ( ) thermoplasties from Hunston et al. (1987) (A) from Bradley (1989a) ( ) from Jordan and Bradley...

Hunston D.L., Moulton R.J., Johnston N.J. and Bascom W.D. (1987). Matrix resin effects in composite dclamination Mode 1 fracture aspects. In Toughened Composites, ASTM STP 937 (N.J. Johnston ed.), ASTM, Philadelphia, PA, pp. 74-94. 

Poon, C., Benak, T. and Gould, R. (1990). Assessment of impact damage in toughened resin composites. Theor. Appl. Fract. Mech. 13, 81-97. 

Standard Tests for Toughened Resin Composites. NASA Reference Publication 1092, 1983. 

Thermosets are generally used in advanced composites due to their excellent thermal and dimensional stability, high modulus, and good mechanical properties. Because thermoset resins are inherently brittle, however, some applications require improved fracture resistance. Toughening of thermosets has been achieved through various methods, such as incorporation of reactive liquid rubber [1-9], elastomer [10], or rigid thermoplastics [11-25], and IPN formation with ductile component [26]. 

As an aside, we note that the FDEMS sensor input information can also be used to detect the onset of phase separation in toughened thermoset systems and to monitor cure in thin film coatings and adhesive bond lines. It is particularly important that the FDEMS sensor is also very sensitive to changes in the mechanical properties of the resin due to degradation. As such, it can be used for accelerated aging studies and as a dosimeter to monitoring the composite part during use to determine the knockdown in the required performance properties with time. 

---