Curing levels

The curing time profoundly affects the glass transition of epoxy systems for cure level is dependent on time and temperature of cure. Some systems cured for... 

It should be noted that the linear viscoelastic behaviour needs to be examined as a function of temperature and cure level during the reaction in order to describe fully the viscoelastic behaviour of the system. 

Optimum cure time (t9o) (minutes) Time to reach optimum cure level... 

The cure level can be obtained from Equation 1.1 by substituting 0 as a function of time t and integrating it. 

If there is an increase in cure dc at a cure level c at the reference temperature, but... 

A method for studying the photo-induced polymerisation of photoresists and solder masks at the substrate/ photopolymer interface, using ATR and IR spectroscopy is described. The technique is especially useful for dry film photoresists and gives information on cure levels affected by exposure dose and photoresist thickness. The photoprocessing of Vacrel 8100 series solder mask and Riston 3100 series photoresists from Dupont are used as examples. 23 refs. 

Under Cure. The reqnirement of full cure is relatively easy to obtain if proper cure time and temperatnre are nsed. One measure of the cure level is Tg. Periodic measurements of Tg are an excellent check for material and process consistency. Another way to check cure is to make two consecutive measurements of Tg If the epoxy is only partially cured, it will continue to cure during the first measurement and a higher Tg will be detected on the second measurement. A shift inTg of more than 5°C is an indication of under cure. This measurement is typically performed on a TMA. Figure 27.39 shows an example of an epoxy TMA run note that the second TMA run has a delta of 3°C. 

The recrystallization behavior of the samples was confirmed by DSC. Figure 11 shows the DSC curves for samples A-C. Sample C shows the highestand no detectable recrystallyzation. Samples A and B display not only well-defined reciystallization peaks but also melting endotherms not observed in Sample C. From the results of the study, it was concluded that the DSC and DMA methods can be used for monitoring the cure levels in the silicone release coatings. 

Do small differences in the production cycle (which give polymers which are hardly distinguishable by thermal analysis techniques) really affect the mechanical performance In other words, are the thermal analysis techniques more sensitive than mechanical tests in identifying the cure level ... 

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