Degree of cure

Ruiz and co-workers [2] used differential photocalorimetry to estimate the degree of cure of photocurable coatings based on a compound containing 63% of an aliphatic urethane acrylate (Ebecryl 270), 34% of 1,6-hexanediol diacrylate and 3% of 2-hydroxy 2-methyl 1-phenylpropan-l-one (Darocur 1173) initiator. It was shown that results obtained by the DPC technique were more sensitive than those obtained by DSC. 

An application of DMA to the measurement of resin cure is discussed in Section 8.1.2. 

Overcuring, although not as serious as incomplete curing, can result in embrittlement, reduced vibration, and shock resistance. Most methods used to establish the optimum cure are based on measuring a specific physical or electrical property as a function of the time and temperature to produce an optimum value. More quantitative methods involve measuring changes in the 

DSC has been used to establish optimum cure schedules for rapid curing (snap cure) adhesives and adhesives requiring longer cures. Results showed that the snap-cured adhesive was 98% cured in 3 minutes, compared with over 15 minutes for the conventional cured adhesive.The cure for the latter adhesive was verified by thermomechanical analysis (TMA) by measuring the Jg as a function of cure schedules where it was shown that up to 15 0° C, the Tg had not yet reached a plateau after 30 minutes. At 165°C, a plateau was reached in 30 minutes, and at 170°C, the Tg peaked in 10 to 15 minutes. 

Cure cycles for adhesives should not be interrupted. Step curing should be performed in the same oven without exposing the adhesive to ambient air. Moisture absorption in partially cured adhesives affects the curing process and alters properties. The effects of interrupting the cure cycle and exposing an epoxy encapsulant to air moisture were shown by Naito and Todd.i i 

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A comparison of coatings formulations based on various glycols to determine the effects of the various glycol stmctures on the performance properties of the coatings has been made. Properties compared included degree of cure, flexibiHty, hardness, hydrolytic stabiHty, processibiHty, chemical and stain resistance, and viscosity (18,19). 

Polyfunctional aliphatic resins have exhibited high reactivity and degrees of cure with amines but problems of toxicity have diminished their usehilness and commercial interest. SoHd epoxy resins can be prepared by the taffy process or the advancement process. 

When formulating a silicone adhesive, sealant, or coating, based on hydrosilylation addition cure, one must consider the following properties of the uncured product pot life, dispensing technique, rheology, extrusion rate, cure performance. These characteristics directly affect the processing properties of the polymer base or crosslinker parts. The degree of cure conversion at the temperature of interest is determined by properties such as tack free time, cure profile and cure time. Once... 

Barcol hardness Also called Barcol impresses It is a measure of the hardness of a plastic, that includes laminate or reinforced plastic, using a Barber Coleman spring loaded indenter. Gives a direct reading on a 0 to 100 scale higher number indicates greater hardness. This test is often used to measure the degree of cure for plastics, particularly TS plastics. 

The difference in degree of cure of the blends by different curatives has also been explained on the basis of changes in curative distribution with accelerator types and the effect of cure temperature. The tensile properties of the blend cured by S/ZDEC at 170°C were significantly lower and modulus was higher than those cured by S/MET and S/DPG as shown in Table 11.17. Lowering of cure temperature by 20°C significantly improved these properties. However, the standard deviation in the results increased limiting the potential for any solid conclusion. 

Future work in this area will involve the extension of these techniques to other temperatures in an effort to better characterize the overall reaction kinetics of these two processes. In addition, degree of cure obtained through isothermal DSC measurements will be compared with the fraction of acetylene consumed as measured by isothermal FTIR experiments for the same temperature and time. Also, the effect of the incorporation of metal fillers on the isomerization and crosslinking reactions will be addressed. 

Degree of cure and rate of cure for thermoset and UV-cured resins and similar are both properties that can be measured and monitored readily by a number of... 

The W types require additional acceleration and ethylene thiourea (ETU), gives the best balance of all properties. However, the use of this accelerator is increasingly being restricted due to fears of its effects on pregnant women, and more recently men. DETU, thiurams and guanidines can also be used. Sulphur is sometimes used to increase the degree of cure in the W types, but this detracts from the ageing performance of the vulcanisate. 

The objective of the present work was to determine the influence of the light intensity on the polymerization kinetics and on the temperature profile of acrylate and vinyl ether monomers exposed to UV radiation as thin films, as well as the effect of the sample initial temperature on the polymerization rate and final degree of cure. For this purpose, a new method has been developed, based on real-time infrared (RTIR) spectroscopy 14, which permits to monitor in-situ the temperature of thin films undergoing high-speed photopolymerization, without introducing any additive in the UV-curable formulation 15. This technique proved particularly well suited to addressing the issue of thermal runaway which was recently considered to occur in laser-induced polymerization of divinyl ethers 13>16. 

Degree of cure, estimating, 10 426 Degree of dissociation, for ionic surfactants, 24 130... 

Figure 5. Log a (ionic diffusion) vs. a (degree of cure) for the uncatalyzed epoxy during isothermal cure.

Tool-mounted optrode (TMO). The cure-monitoring experiments described here were conducted with a "tool-mounted" optrode (TMO) arrangement (5,6) (Figure 2) which is Ideally suited for the manufacturing environment where minimum interference with the laminate layup work is desirable. The use of a tool-mounted optrode is as simple as the use of tool-mounted thermocouples currently in wide use. Indeed, the TMO provides viscosity/degree-of-cure information on the cure state of the surface layer only. However, knowledge of the cure state of the surface layer permits determination of the cure states in the bulk based on the available models (1,2). 

Figure 2.3 Reaction rate versus degree of cure for an autocatalytic model—curves a and b, at temperatures Ta and Tb, respectively, have an initial reaction rate equal to zero, and curve c has an initial reaction rate different from zero...

Figure 2.5 Degree of cure time versus time for an autocatalytic model—curves a, b, and c have temperatures Ta, Tb, and Tc, respectively, where Tc > Tb > Ta...

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