Rubber-modified thermosets: Prediction of the particle size distribution of dispersed domains

Vázquez, Analı́a; Rojas, A. J.; Adabbo, H. E.; Borrajo, Julio; Williams, R. J. J.

doi:10.1016/0032-3861(87)90259-x

Cited by 105 publications

(62 citation statements)

References 9 publications

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“…3-6) allows estimation of the gelation and vitrification points as discussed p r e v i~u s l y .~~~~~ In the case of the systems containing CTBN, the increase in the dielectric constant can be used to define the point at which phase separation occurs. Values obtained for the systems studied are presented in Table 111, and for the pure resin systems, they agree well with those quoted by other workVariation of the gelation time and point ers*25, [37][38][39] of phase separation with CTBN content behaves according to an equation of the form t = kV-" (1) where t is the gelation time, k and n are constants characteristic of the system, and V is the volume fraction of the rubbery phase. The coefficients obtained from fitting the data are presented in Table Iv.…”

Section: Studies Of Cure In Dgeba/ddm Systemssupporting

confidence: 82%

Dielectric and morphological investigations of phase separation and cure in rubber‐modified epoxy resins: Comparison between teta‐ and DDM‐based systems

Delides¹,

Hayward

Pethrick

et al. 1993

J of Applied Polymer Sci

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SYNOPSISReal-time and equilibrium dielectric measurements, covering the frequency range lo-'-lo6 Hz, are reported on a series of rubber-modified epoxy resins, based on reaction of the diglycidyl ether of bisphenol A (DGEBA) with either triethylenetetramine (TETA) or diaminodiphenylmethylene ( DDM ) . The rubber modifier used was a carboxyl-terminated butadiene acrylonitrile ( CTBN) reactive oligomer and the phase-separated structure, the results of which was examined using both dielectric and electron microscopic techniques. The mixture was initially homogeneous, but after a short period of time, it underwent phase separation and this process was marked by the appearance of a dielectric peak associated with ion-charge migration within the occluded rubbery phase. Analysis of the peak provided information on the morphology of the system and these data were compared with information obtained from scanning electron microscopy. A phase-separated morphology was observed consisting of spherical rubber particles dispersed in an epoxy matrix. For high concentrations of rubber 2 10 wt %, precipitation of epoxy domains within the rubbery phase was observed. Detailed dielectric studies of the peak associated with phase separation revealed that in the case of the TETA system the peak continued to shift after vitrification, whereas in the case of DDM, it was invariant with time. The point at which the peak appears was used to determine the time at which phase separation occurred. Differences observed in the lower temperature dielectric spectra were associated with variations in the form of the phase structure and possibly reflect different degrees of densification of the matrix. Good agreement was observed between the predictions of the Maxwell-WagnerSillers (MWS) theory and experimental observation for these systems. 0 1993

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Section: Studies Of Cure In Dgeba/ddm Systemssupporting

confidence: 82%

Dielectric and morphological investigations of phase separation and cure in rubber‐modified epoxy resins: Comparison between teta‐ and DDM‐based systems

Delides¹,

Hayward

Pethrick

et al. 1993

J of Applied Polymer Sci

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“…[9], the presence of a mono-disperse polymer was assumed. The problem of expressing the average molecular weight in amine-cured epoxies under such an assumption has been already treated in the literature (19,20). According to these approaches, the number-average molecular weight, M n , of an epoxy-amine system can be expressed as (20) …”

Section: Resultsmentioning

confidence: 99%

Enthalpic, Entropic, and Square Gradient Contributions to the Surface Energetics of Amine-Cured Epoxy Systems

Mezzenga

Page

2002

Journal of Colloid and Interface Science

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“…Similar results have been reported in the literature. 14,26,30,31 It has to be mentioned that the quantitative determination (using dibutylamine titration according to ASTM D 1638) of the unreacted ONCO group in the synthesized PU prepolymer is important. This serves as a mean to monitor the product quality as well as the crosslinking reactions.…”

Section: Tdi-to-desmophenmentioning

confidence: 99%

Toughening of epoxy resin using synthesized polyurethane prepolymer based on hydroxyl-terminated polyesters

Harani

Fellahi

Bakar

1998

J. Appl. Polym. Sci.

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Epoxy resins are increasingly finding applications in the field of structural engineering. A wide variety of epoxy resins are available, and some of them are characterized by a relatively low toughness. One approach to improve epoxy resin toughness includes the addition of either a rigid phase or a rubbery phase. A more recent approach to toughen brittle polymers is through interpenetrating network (IPN) grafting. It has been found that the mechanical properties of polymer materials with an IPN structure are fairly superior to those of ordinary polymers. Therefore, the present work deals with epoxy resin toughening using a polyurethane (PU) prepolymer as modifier via IPN grafting. For this purpose, a PU prepolymer based on hydroxyl-terminated polyester has been synthesized and used as a modifier at different concentrations. First, the PU-based hydroxyl-terminated polyester has been characterized. Next, an IPN (Epoxy-PU) has been prepared and characterized using Fourier transform infrared (FTIR) spectroscopy, thin-layer chromatography (TLC), and scanning electron microscopy (SEM) prior to mechanical testing in terms of impact strength and toughness. In this study, a Desmophen 1200-based PU prepolymer was used as a modifier at different concentrations within the epoxy resin. The results also showed that, further to the IPN formation, the epoxy and the PU prepolymer reacted chemically (via grafting). Compared to virgin resin, the effect on the mechanical properties was minor. The impact strength varies from 3-9 J/m and K c from 0.9 -1.2 MPa m 1/2 . Furthermore, the incorporation of a chain extender with the PU prepolymer as a modifier into the mixture caused a drastic improvement in toughness. The impact strength increases continuously and reaches a maximum value (seven-fold that of virgin resin) at a modifier critical concentration (40 phr). K c reaches 2.5 MPa m 1/2 compared to 0.9 MPa m 1/2 of the virgin resin. Finally, the SEM analysis results suggested that internal cavitation of the modifier particles followed by localized plastics shear yielding is probably the prevailing toughening mechanism for the epoxy resin considered in the present study.

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Rubber-modified thermosets: Prediction of the particle size distribution of dispersed domains

Cited by 105 publications

References 9 publications

Dielectric and morphological investigations of phase separation and cure in rubber‐modified epoxy resins: Comparison between teta‐ and DDM‐based systems

Dielectric and morphological investigations of phase separation and cure in rubber‐modified epoxy resins: Comparison between teta‐ and DDM‐based systems

Enthalpic, Entropic, and Square Gradient Contributions to the Surface Energetics of Amine-Cured Epoxy Systems

Toughening of epoxy resin using synthesized polyurethane prepolymer based on hydroxyl-terminated polyesters

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