Curing commercial trends

The effect of an additional 310 °C cure on the emission intensity and intermolecular spacing of a 6FDA-IPDA film, as compared to a 250 °C cured 6FDA-IPDA film, is also shown in Table III. The intensity of the 310 °C cured sample is significantly greater than that of the 250 °C cured sample. This behavior is identical to that observed in the cure study of the commercial polyimide films. Furthermore, this increase in intensity corresponds to a decrease in intermolecular distance, as shown by the data in Table III, analogous to the trend observed with the PMDA films. Finally, this extra cure appeared to result in a more ordered film as is evident by the addition of two minor diffraction peaks corresponding to 3.4 and 2.1... 

Photostabilization processes have not received much attention in the last year other than a multitude of review and specialist industrial articles. These include stabilization of polypropylene fibres, new stabilizer developments, sorting of stabilizers for polyethylene, trends in UV absorbers, hindered piperidines (hindered amine stabilizers (HAS)) for polyacrylics and urethanes, new stabilizers for polyolefins, enhanced service life applications, stabilizer mas-terbatches for polyester, stabilizers for UV cured acrylic overcoats for PVC, ° stabilization of clearcoats and various commercial packages. ... 

BT laminates have a Tg of 180°C and a high degradation temperature. For most high-temperature applications, they are a direct substitute for polyimide. They have the added advantage that the moisture sensitivity and processibility of BT are much closer to those of conventional epoxy than those of polyimide. Other than a high-temperature post lamination bake required for a full cure, the BT process is the same as an epoxy process. The major drawback of the BT laminate is cost. Although BT is much less expensive than polyimide, it is still up to 1.5 times the cost of epoxies. The result is that BT is a popular replacement for polyimide, but its use is limited to specialty applications. The trend for most high-temperature commercial applications is either a multifunctional epoxy or an epoxy-PPO blend. 

When the cured epoxy network is heated to a certain temperature, the thermally labile carbamate linkages start to cleave. It is found that the thermal dissociation of carbamates follows a general trend alkyl-NHCOO-alkyl (250 C), aryl-NHCOO-alkyl (200 X), alkyl-NHCOO-aryl (180 C), and aryl-NHCOO-aryl (120 °C). Indeed, the thermogravimetric analyses show that, compared to the commercial epoxy resin (ERL-4221), the cured carbamate-linked epoxy resins display decreased temperature range of initial decomposition from 220 °C to 350 C. 

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