Epoxidized natural rubber/epoxy blends: Phase morphology and thermomechanical properties

Abstract

Epoxidized natural rubbers (ENRs) were prepared. ENRs with different concentrations of up to 20 wt % were used as modifiers for epoxy resin. The epoxy monomer was cured with nadic methyl anhydride as a hardener in the presence of N,Ndimethyl benzyl amine as an accelerator. The addition of ENR to an anhydride hardener/epoxy monomer mixture gave rise to the formation of a phase-separated structure consisting of rubber domains dispersed in the epoxy-rich phase. The particle size increased with increasing ENR content. The phase separation was investigated by scanning electron microscopy and dynamic mechanical analysis. The viscoelastic behavior of the liquid-rubber-modified epoxy resin was also evaluated with dynamic mechanical analysis. The storage moduli, loss moduli, and tan d values were determined for the blends of the epoxy resin with ENR. The effect of the addition of rubber on the glass-transition temperature of the epoxy matrix was followed. The thermal stability of the ENR-modified epoxy resin was studied with thermogravimetric analysis. Parameters such as the onset of degradation, maximum degradation temperature, and final degradation were not affected by the addition of ENR. The mechanical properties of the liquid-natural-rubber-modified epoxy resin were measured in terms of the fracture toughness and impact strength. The maximum impact strength and fracture toughness were observed with 10 wt % ENR modified epoxy blends. Various toughening mechanisms responsible for the enhancement in toughness of the diglycidyl ether of the bisphenol A/ENR blends were investigated. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39906.

RETRACTED: Epoxy Resins Toughened with Surface Modified Epoxidized Natural Rubber Fibers by One-Step Electrospinning

“…E-ERF 5 and E-ERF 10 show about 1.2 GPa and 1.1 GPa of modulus, and 52 MPa and 47 MPa of fracture strength, respectively, compared to that of neat epoxy resin having modulus of 1.4 GPa and tensile strength of 58 MPa. Compared to other studies, epoxy resin containing ENR particles (not in fiber form) showed much loss in tensile properties [24,51,52]. For example, epoxy resin with 12% liquid epoxidized natural rubber (particle size 0.48 to 0.67 in diameter) increased 125% impact toughness, but decreased tensile properties by 15 MPa from 65 MPa to 50 MPa, compared to neat epoxy resin [51].…”

Enhanced Charpy impact strength of epoxy resin modified with vinyl‐terminated polydimethylsiloxane

“…Since rubber modifiers are widely used as toughening agents of ER, we carried out investigation in order to compare our and published previously results. The value of impact strength of similar system (ER modified by rubber elastomers) is comparable/or better than those stated in Table IV, that is, Ozturk et al, 6 Lin et al, 18 Thomas et al, 36 Mathew et al, 37 Miwa et al, 38 even in the case of modification with block copolymer Zhao et al 48 As for the storage modulus, we obtained a decent value of 2000 MPa, which is in the upper half of values from Table IV with 3000 MPa (for 15 wt % of CTBN) 9 being the highest recorded value. As can be seen from the table glass transition temperature of our sample is one of the highest from compared systems stated in Table IV.…”

“…The critical concentration of a modifier is defined by the threshold when the mechanical properties of blends start to decrease. 37 On the other hand, the maximum impact strength (792 kJ/m 2 ) for the CTBN modifier in ER was reached at 15 phr. 35 For example, the maximum impact strength (13.6 J/m 2 ) was observed for 10 phr of HTPB in ER; for 20 phr of HTPB, the impact strength is lower by 30% than the maximum value.…”

A structural study of epoxidized natural rubber (ENR‐50) ring opening under mild acidic condition

“…TG and DTG thermograms of purified ENR-50 and acid-treated ENR-50 are shown in Figure 6. [39][40][41][42] These degradations occurred at wider temperature range than the purified ENR-50. 37,38 Meanwhile, acid-treated ENR-50 showed three steps of degradations over a temperature range studied.…”