Curing effects on viscosity of reactive epoxy resin adhesives

Hesekamp, Dietger; Pahl, Manfred H.

doi:10.1007/bf00403532

Cited by 9 publications

(5 citation statements)

References 15 publications

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“…When the resin was cooled down from 175 to 130°C, the viscosity increase was more rapid due to the combined effects of polymerisation and cooling effect and reached a value of (76 ± 8) Pa‐s. Similar behavior of epoxy resin under cooling effect during cure has been observed by the researchers in the past 3, 39. The resin was subsequently allowed to flow for 60 min at intermediate dwell temperature of 130°C, where sufficient flow of resin occurred and the viscosity of the resin attained a maximum value of (1780 ± 180) Pa s. At second ramp, the viscosity of the resin decreased for certain time period and then increased again due to polymerisation.…”

Section: Resultssupporting

confidence: 74%

Determination of optimum cure parameters of 977‐2A carbon/epoxy composites for quickstep processing

Khan¹,

Iqbal

Hussain

et al. 2013

J of Applied Polymer Sci

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In this study polymer-matrix composite has been processed using autoclave and Quickstep techniques. A phenomenological approach was adopted for the optimization of cure cycle for Quickstep of an aerospace grade epoxy composite (Cycom 977-2A carbon/epoxy prepregs). Though there are reports concerning the processing and properties of materials using Quickstep technique, little work has been reported on the design of optimized cure cycle for Quickstep processing based on rheology, ultrasonic testing, and mechanical characterization. A step by step account is provided in this study, describing the introduction, balancing and combination of isothermal dwell periods and temperature ramps in order to control the resin viscosity. All the panels manufactured were qualitatively assessed using ultrasonic C-scan and afterwards fiber and void content, panel thickness, flexural strength, and interlaminar shear strength (ILSS) were assessed and compared with those obtained from traditional autoclave-and oven-cured laminates. The Quickstep panel properties produced from optimized cure cycle was superior to oven curing and was comparable with autoclave.

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Section: Resultssupporting

confidence: 74%

Determination of optimum cure parameters of 977‐2A carbon/epoxy composites for quickstep processing

Khan¹,

Iqbal

Hussain

et al. 2013

J of Applied Polymer Sci

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“…In Eq. 6, viscosity is treated as the combination of two exponential expressions, one for the dependence of viscosity and another for the effect of reaction kinetics [6,24]:…”

Section: Characterizationmentioning

confidence: 99%

“…In reactive systems, two effects can be superimposed in rheometric measurements, the dependence of viscosity with temperature and its increase in the degree of reaction [25,26]. These were determined based on the Pahl-Hesekamp approach [24,27] in which it is possible to separate the viscosity and kinetics therms. The viscosity of the reactive system is described with a WLF equation, in which the actual temperature is reduced by the difference between the actual glass transition temperature, T g (x), and the glass transition temperature for the degree of reaction x = 0 (Eq.…”

Section: Characterizationmentioning

confidence: 99%

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Effect of the aramid pulp on the physicochemical, viscoelastic properties and rheokinetics of polyurethanes

Cruz

Amico²,

Bianchi³

2022

J Polym Res

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This publication highlights the effect of aramid pulp (1 wt.%) on equilibrium swelling, enthalpy reaction, solid viscoelastic properties, and rheokinetics of castor oil (CO) and polyether (PE) polyol blend (50/50 CO/PE) with polymeric isocyanate (pMDI). The CO-pMDI system showed a lower solubility parameter difference (Δδ i ) than the PE-pMDI and CO/PE-pMDI. Crosslink density values ν e are higher for CO-pMDI, and when added to aramid pulp, there is a slight increase due to the possible restriction of swollen volume. Regarding the pseudo-solid behavior, AP restricts the macromolecular movement and confers reinforcing characteristics to PU systems. The Prout-Tompkins autocatalytic model satisfactorily described the reactions, resulting in activation energy values E a within 45−54 kJ/mol. However, for the CO/PE blend, the difference between the reactivity of the polyols and the solubility parameter with pMDI results in a two-step reaction kinetics. Aramid pulp practically does not change the reaction mechanism, only the viscosity of the medium. Furthermore, the thermodynamic parameters (ΔS* and ΔH*) indicated that the PU with AP resulted in more ordered complexes. The adequate description of the polymerization reaction and the effect of the aramid pulp allowed obtaining PU formulations with tunable characteristics for strict composite processing composites.

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“…The magnitude of this formation describes the curing degree and is associated with the glass transition temperature (Tg). Equations to describe the dependence of the Tg from the curing degree are given from DiBenedetto [2], Hesekamp [3], Williams-LandelFerry [4], Fox, Flory [5] and others. From a chemical point of view the cross-linking reaction of an epoxy adhesive is known to be autocatalysed due to the formation of reactive hydroxyl groups during the reaction of the epoxy groups [6].…”

Section: Introductionmentioning

confidence: 99%