Curing behaviour

A development of the moving die rheometer where the operation of the unit is fully computer controlled. The rate of oscillation, temperature and level of strain can all be run through a series of options. The torque measurements are also highly sophisticated. As a consequence, the unit can be set up to monitor processing parameters, then the cure behaviour and finally the finished dynamic properties of the cured material. It is manufactured by Alpha Technologies. 

The cure site monomer directly controls which cure systems can be used to vulcanise the rubber. Since the cure behaviour is determined by the cure site monomer, and this can differ between suppliers, and presumably grades, it is advisable to read the manufacturers recommendation when deciding on the choice of cure system to use. 

R Musto, M. Abbate, G. Ragosta and G. Scarinzi, A smdy by Raman, near-infrared and dynamic-mechanical spectroscopies on the curing behaviour, molecular structure and viscoelastic properties of epoxy/anhydride networks, Polymer, 48, 3703-3716 (2007). 

The mechanism of the accelerated sulfur vulcanisation of EPDM is probably similar to that of the highly unsaturated polydiene rubbers. The vulcanisation of EPDM has been studied with emphasis on the cure behaviour and mechanical and elastic properties of the crosslinked EPDM. Hardly any spectroscopic studies on the crosslinking chemistry of EPDM have been published, not only because of the problems discussed in Section 6.1.3 but also because of the low amount of unsaturation of EPDM relative to the sensitivity of the analytical techniques. For instance, high-temperature magic-angle spinning solid-state 13C NMR spectroscopy of crosslinked EPDM just allows the identification of the rubber type, but spectroscopic evidence for the presence of crosslinks is not found [72]. 

Baldwin and co-workers also studied the peroxide curing behaviour of other EPDMs with a variety of third monomers [97]. As expected, they found that terminal olefins as present in 5-vinyl-2-norbornene (VNB) and MNB containing EPDM provide a much higher peroxide curing efficiency as compared to internal olefins as present in for instance ENB, DCPD and HD containing EPDM. This again is in line with the earlier considerations mentioned [96]. 

Roh, J. K., Higuchi, M., and Sakata, I., Curing behaviour and bonding properties of thermosetting resin adhesives. V. Cocondensation reaction of phenol with melamine, Mokuzai Gakkaishi. 36, 42, 1990 Chem. Abstr., 113, 41891, 1990. 

Only two studies have involved a direct determination of the SiH concentration by IR spectroscopy [5, 10]. The IR measurement of SiH absorption is, however, only suitable for analyzing the reaction in very thin layers or on surfaces. Supplementary to this analysis of the chemical conversion there are also many publications which describe the curing behaviour of industrial platinum-crosslinked silicone rubbers [11,12] (Fig. 1). 

Therefore the phenones Id-g were compared in their curing behaviour with the unsubstituted parent compound la in an isual acrylate based UV curable system (experimental conditions see ref. From the results (Table I) it is concluded that the phenones Id-f have a similar activity as the parent compound la, although differences became obvious at short irradiation time. The initiator activity of the azide Ig was extremely low compared to the phenones la and Id-f. This unexpected result might be explained by the effect of the azido group. To get more insight to the photoreactivity of the azide Ig an ethanolic solution was irradiated for one hour. A new crystalline compound was isolated and characterized as 4-(2-azidoethoxy)benzoic acid. 

Fonnulations containing carboxyl-terminated butadlene/acrylo-nltrlle elastosier (15) showed in our experiments very sluggish cure behaviour. In fact neither the Initial siixture nor a prereacted adduct with epoxy resin gave more than a slight skin formation after prolonged Irradiation. 

Recent developments in sensor technologies for in situ monitoring have made it possible to obtain some insight into the state of the curing resin. Parameters are calculated from sensor measurements and analytical models developed in terms of the epoxy cure behaviour [31]. It is clear that it would be more beneficial if the... 

The thermal properties of freshly prepared pure and additive-modified PF and KLPF resins were studied with DSC. In an attempt to accelerate the curing of KLPF, the additives zinc borate, potassium carbonate, sodium carbonate, and propylene carbonate were added to the resin and the curing behaviour was compared to the curing of unmodified KLPF and PF resins. Based on dynamic DSC experiments, isoconversional kinetic analysis of resin curing was performed. 

FT-IR spectroscopy, NMR spectroscopy and vapour pre-osmometry were used to characterise the polymers and the curing behaviour and stability of the polymers were investigated by DSC and TGA. These polymers were found to decompose in two stages and to be suitable for use as energy binders and fuels in rocket technology. 

LaLiberle BR, Bomstein J, Sacher RE, Cure behaviour of an epoxy resin-dicyandiamide system accelerated by monuron, Ind Eng Chem Prod Res Dev, 22(2), 261-262, 1983. 

Markovic and co-workers [13] investigated the effects of the phenol to formaldehyde ratio used for the preparation of novolac and the nature of methylene linkages on the curing behaviour of the novolac/HMTA system using rheological studies. Cure kinetics were described by a third-order phenomenological equation, which took into account the self-acceleration effect that arises from the chemical reaction and phase separation. The reaction rate was found to increase with an increase in phenol to formaldehyde ratio. For the same phenol to formaldehyde ratio, the reaction rate increased with an increase in o, o methylene linkages (Table 2.2). 

Using reference substances, either comercially available or synthesized and purified by known methods like 5-ethinyl-2-norbornene (ET-NBE, Scheme 3), and adding these separately to the solution of 1 in highly purified DCPD, we found that ET-NBE activates the system. This was rather unexpected, since acetylenes are known as catalyst poisons in the RIM of DCPD with Mo- and W-based catalyst and are therefore carefully removed during the purification of DCPD. If the monomer contained very low levels of ethinyl-norbornene, a very bad curing behaviour with 1 as catalyst was observed. Best results were obtained with approximately equimolar amounts of ET-NBE and 1. It turned out that crude DCPD (e.g. 94% from Shell) contained - by chance -approximately the appropriate amount of this acetylene and therefore was nicely cured with 1. 

It was found later that ET-NBE could be replaced by any monosubstituted acetylene, e.g. the much cheaper phenylacetylene, as long as the acetylene was present in approximately equimolar amounts, relative to the catalyst. Table 2 lists some other acetylenes, which were tested. It was also noted that the curing behaviour was influenced by the type of acetylene. For example the curing with 3-hydroxy-3-methyl-butyne led to a slower reaction which is less exothermic and could therefore be used for the curing of large objects. 

The performance of powder coatings during fusion and subsequent cure may be followed in detail by thermal analytical procedures such as differential thermal analysis and differential scanning calorimetry. These techniques offer an opportunity for the study of phase transitions and cure behaviour under closely controlled conditions. Differential scanning calorimetry is a requirement in the British Gas standard for epoxy powder coating materials for the external coatings of steel pipes where it is used as a guide to ascertain optimum cure conditions. 

Table 11.2 shows a rough comparison between the curing behaviour of a peroxide curing HTV, an addition curing HTV and an addition curing LR. 

The remaining stock pieces, from which the Mooney viscosity samples had been taken, were blended together and mixed in a laboratory BR Banbury using the formulation detailed in Table 7. The cure behaviour of each batch was examined using a Monsanto Rheometer and test pieces for assessing vulcanizate properties were cured for 20 min at 150°C. Tensile properties were measured after ageing in an air oven. 

Traditionally testing of unvulcanised rubber compounds before processing involves evaluation of plasticity (or, more correctly, viscosity-related properties) and scorch/curing behaviour. 

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