Modifiers liquid rubbers

Saa Saadati, P., Baharvand, H., Rahimi, A., Morshedian, J. Effect of modified liquid rubber on increasing toughness of epoxy resins. Iranian Polym. J. 14 (2005) 637-646. 

Keywords unsaturated polyester, vinyl ester, impact modifiers, liquid rubbers, toughening, microstructure, cure, cavitation. 

Liquid rubbers In order to improve the flexibihty of short glass fiber-reinforced epoxy composites, Kaynak et al. [53] modified the epoxy resin matrix with hydroxyl-terminated polybutadiene (HTPB) liquid mbber. A silane coupling agent was also used to improve the interfacial adhesion between glass fibers and epoxy matrix. However, Humpidge et al. [54] reported some unique processing problems for the resulting pasty mixmres when short textile fibers were incorporated in a hquid mbber medium. 

The thermoplastic-rich phase may be separated in the course of polymerization (Sec. 13.4.2) or can be incorporated as a dispersed powder in the initial formulation (Sec. 13.4.3). A strong drawback of the in situ-phase separation for processing purposes is the high viscosity of the initial solution which results from the much higher average molar mass of the TP compared with the liquid rubbers. Also, for the same reason, the critical concentration crit has a smaller value (phase inversion is observed at smaller concentrations of modifier). 

High temperature epoxy resins are brittle materials, and one method of improving their fracture properties is to incorporate reactive liquid rubbers in the formulations In situ phase separation occurs during cure the cured rubber-modified epoxy resins consist of finely dispersed rubber-rich domains ( 0.1-S pm) bonded to the epoxy matrix. TTT diagrams can be used to compare different rubber-modified systems. 

Unmodified or rubber-modified liquid cashew resins have been used to make wet drum lining mixes. These resins are inexpensive and help to improve product... 

This investigation of silicone-modified hybrid composites demonstrates that compatibilized, segmented liquid rubbers can be tailored to promote the formation of colloidal rubber dispersions, which enhance the toughness of the epoxy matrix. Furthermore, such segmented liquid rubbers can in situ-modify filler surfaces to form core-shell particles with a hard filler core and a thin... 

The polyester resin used in this study, MR 13006 (Aristech Corporation), was supplied as a 60-wt% solution in styrene monomer. The epoxy resin, a digly-cidyl ether of bisphenol A (Epon 828), was obtained from Shell Chemical Company. The reactive liquid rubber, an amino-terminated butadiene-acrylonitrile copolymer (ATBN 1300 x 16), was provided by the BFGoodrich Company. The resin was mixed with additional styrene monomer to maintain the ratio of reactive unsaturation in the polyester-to-styrene monomer at 1 to 3. We added 1.5 wt% of tert-butylperbenzoate initiator to the solution, which we then degassed under vacuum. The mixture was poured between vertical, Teflon-coated, aluminum plates and cured under atmospheric pressure at 100 °C. In the modified compositions, the rubber was first dissolved in the styrene monomer, and then all the other components were added and the solution cured as described. In all the compositions, the ratio of the amine functions with respect to the epoxy functions was kept at 1 to ensure complete cure of the epoxy. 

Recent work has shown that the addition of epoxy-terminated butadiene-acrylonitrile (ETBN) liquid rubbers to elastomer-modified VER gives a fivefold increase in fracture energy over that of elastomer-modified VER (3). 

Fracture-Energy Testing. Table I gives the recipes and the fracture energies measured under slow and fast rates of test, for the elastomer-modified VER and for ETBN additions to the elastomer-modified VER. Also given are the total amounts of reactive liquid rubber, from both ETBN addition and CTBN reacted directly into the VER, for each recipe. For reference, the unmodified VER has a slow GIc. of 0.11 kj/m2. Finally, the Tg obtained from differential scanning calorimetric measurements is given for each recipe. 

As natural rubber is a product of nature, its properties are determined by the biochemical pathway by which the polymer is synthesized in the plant. In the case of natural rubber the polymerization process cannot be tailored like that of synthetic rubbers. The only option to modify natural rubber is after it has been harvested from the tree. The important modified forms of natural rubber include hydrogenated natural rubber, chlorinated natural rubber, hydro-halogenated natural rubber, cyclized natural rubber, depolymerised liquid natural rubber, resin modified natural rubber, poly(methyl methacrylate) grafted natural rubber, poly(styrene) grafted natural rubber, and epoxidized natural rubber [33,34]. Thermoplastic natural rubber prepared by blending natural rubber and PP is considered as a physically modified form of natural rubber. 

Impact Performance of Epoxy Resins with Poly(/i-butyl acrylate) as the Reactive Liquid Rubber Modifier... 

Although there is some scatter in the plots of EEW versus isothermal aging time, these data are convincing that, within experimental error, there is no significant difference in the rates of loss of epoxides between members of this homologous series of liquid rubber-modified epoxy resins. Further, that the rate of loss of epoxides is so low, despite the homogeneous reaction mixture and the high concentrations of epoxide... 

OOXia Xiao, K. Q., Ye, L. Effects of rubber-rich domains and the rubber-plasticized matrix on the fracture behavior of liquid rubber-modified araldite-F epoxies. Polym. Eng. Sci. 40 (2000) 2288-2298. 

OlAua Auad, M. L., Frontini, P. M., Borrajo, J., Aranguren, M. I. Liquid rubber modified vinyl ester resins fracture and mechanical behavior. Polymer 42 (2001) 3723-3730. 

In this method, a liqnid rnbber is blended with a thermoset resin before curing [108-200]. Various liquid rubbers used for toughening thermoset resins are presented Table 4.1. The toughening effect of a particular modifier is largely dependent on the... 

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