Rheological Monitoring of Phase Separation Induced by Chemical Reaction in Thermoplastic-Modified Epoxy

Vinh‐tung, C.; Lachenal, G.; Chabert, B.

doi:10.1021/ba-1996-0252.ch005

Cited by 9 publications

(5 citation statements)

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“…The corresponding phase separation time, t ll,sol may correspond to the maximum of the tan δ curves observed around 6000 s for T i = 50 °C and 1700 s for T i = 70 °C. Such a maximum in tan δ has previously been observed for thermoplastic−epoxy blends at phase separation . It is believed to originate from interfacial deformation of the newly formed interface between the developing phases .…”

Section: Resultssupporting

confidence: 61%

“…Assuming the thermoplastic solutions in the thermoset precursors to be initially homogeneous, the increase in the molar mass of the epoxy−diamine copolymer during curing may result in liquid−liquid phase separation, even if the temperature is kept constant, due to the decrease in entropy of mixing. Such a well-known reaction-induced phase separation process − can be very simply detected by the fact that the solutions become cloudy. The final morphology in resulting thermoplastic−thermoset blend is strongly dependent on the complex competition between phase separation and polymerization rates.…”

Section: Introductionmentioning

confidence: 99%

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Interpenetrating Chemical (Polyepoxide) and Physical (Poly(vinyl chloride)) Gels

Girard-Reydet

Pascault

2000

Macromolecules

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Low-concentration solutions of poly(vinyl chloride) (PVC) in (diglycydyl ether of bisphenol A/4,4‘-diamino-3,3‘-dimethyldicyclohexyl methane) monomers were observed to have the ability to form chemically reactive physical gels. The changes in rheological and optical properties were monitored as a function of time by the use of dynamic shear rheometry and light transmission, respectively. For a given PVC concentration, the isothermal behavior of these solutions is governed by the competition between physical gelation rate and reaction-induced phase separation rate. The temperature, pg T ll, at which physical gelation and liquid−liquid demixing occur simultaneously, was then defined. When curing temperature, T i, is higher than pg T ll, the blend behaves like a classical amorphous thermoplastic-thermoset blend and the final heterogeneous structure consists of PVC-rich particles dispersed in a polyepoxide-rich matrix. When T i is lower than pg T ll, the physical gelation rate is high enough to ensure the formation of a macroscopic PVC gel before any phase separation phenomenon. True interpenetrating chemical (polyepoxide) and physical (PVC) gels are then generated. The usual temperature-dependent function of the crystallization-induced physical gelation rate was found to be affected by the extent of the epoxy−diamine polycondensation reaction. The evolution of pg T ll with PVC concentration is mainly governed by the concentration-dependent function of the physical gelation rate, resulting in an increase of pg T ll with PVC concentration.

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Section: Resultssupporting

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Interpenetrating Chemical (Polyepoxide) and Physical (Poly(vinyl chloride)) Gels

Girard-Reydet

Pascault

2000

Macromolecules

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“…A frequency sweep using 1, 8.8, 16.6, 25.0, 33.3 and 42.9 Hz in the autostress mode and a target strain of 1 was performed during isothermal cure at 160 °C. Gelation was determined from the point where tanδ became independent of frequency 9. It is important to note that the rheological data below 900 s are not considered to be valid measurements due to the torque being below what the instrument is able to measure accurately.…”

Section: Methodsmentioning

confidence: 99%

Toughening of epoxy resin systems using low‐viscosity additives

Varley

2003

Polymer International

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This study has evaluated three low-viscosity epoxy additives as potential tougheners for two epoxy resin systems. The systems used were a lower-reactive resin based upon the diglycidyl ether of bisphenol A (DGEBA) and the amine hardener diethyltoluene diamine, while the second epoxy resin was based upon tetraglycidyl methylene dianiline (TGDDM) and a cycloaliphatic diamine hardener. The additives evaluated as potential tougheners were an epoxy-terminated aliphatic polyester hyperbranched polymer, a carboxy-terminated butadiene rubber and an aminopropyl-terminated siloxane. This work has shown that epoxy-terminated hyperbranched polyesters can be used effectively to toughen the lower cross-linked epoxy resins, i.e. the DGEBA-based systems, with the main advantage being that they have minimal effect upon processing parameters such as viscosity and the gel time, while improving the fracture properties by about 54 % at a level of 15 wt% of additive and little effect upon the T g . This result was attributed to the phase-separation process producing a multi-phase particulate morphology able to initiate particle cavitation with little residual epoxy resin dissolved in the continuous epoxy matrix remaining after cure. The rubber additive was found to impart similar levels of toughness improvement but was achieved with a 10-20 • C decrease in the T g and a 30 % increase in initial viscosity. The siloxane additive was found not to improve toughness at all for the DGEBA-based resin system due to the poor dispersion within the epoxy matrix. The TGDDM-based resin systems were found not to be toughened by any of the additives due to the lack of plastic deformation of the highly cross-linked epoxy network 

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“…This phenomenon is attributed to the occurrence of phase separation which has been attributed to an increase in elasticity from the creation of an interface between two liquids [23]. Another interpretation of this process was put forward by Vinh-Tung et al [24] who explained this behaviour in terms of an additive of lower viscosity than the developing network being ejected from the continuous epoxy matrix and therefore producing an increase in viscosity. Fig.…”

Section: Development Of Cure Profilementioning

confidence: 97%

Toughening of a carbon fibre reinforced epoxy anhydride composite using an epoxy terminated hyperbranched modifier

DeCarli

Kozielski

Tian

et al. 2005

Composites Science and Technology

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Rheological Monitoring of Phase Separation Induced by Chemical Reaction in Thermoplastic-Modified Epoxy

Cited by 9 publications

References 0 publications

Interpenetrating Chemical (Polyepoxide) and Physical (Poly(vinyl chloride)) Gels

Interpenetrating Chemical (Polyepoxide) and Physical (Poly(vinyl chloride)) Gels

Toughening of epoxy resin systems using low‐viscosity additives

Toughening of a carbon fibre reinforced epoxy anhydride composite using an epoxy terminated hyperbranched modifier

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