Post-cure effect

Methods 1 and 3 have been utilized in dry developed resist systems. To our knowledge, there are no resist systems commercially available that depend on post-exposure treatment other than the post-curing effect in negative electron beam resists mentioned earlier. Since such systems are still largely in the research phase we will not discuss them here but rather refer the reader to the literature for more detailed descriptions (44-50). 

To minimize such effects, low heating rates should be adopted in DMA tests. In this way, however, material time dependent behavior may become more significant because of the longer thermal exposure, as well as any post-curing effects during the thermal exposure. 

One final point worth noting is that, provided the temperature does not rise above 150-200 °C, when a chemical deterioration occurs, the reduction in mechanical properties above the HDT is reversible on cooling. Indeed, stiffness and strength may even be enhanced due to post-cure effects at the elevated temperature. On the debit side, or HDT will be lowered by water absorption into the polymer. Indeed, the Tg should be one of the first criteria in assessing the likely suitability of candidate adhesives. 

Each of the above concepts, as well as other factors such as energy requirements for cure and post-cure effects, are major contributors toward developing radiation curable coating systems that have bonding capabilities to a wide variety of substrate materials. The major emphasis of this paper will center on polymer design for improved adhesion. 

Post-curing effect In Table 9.12 it can be seen that the use of the mixed chain-extender system Dianol 22 + EDO with both PPDI and CHDI gives very strong polyurethanes (cf. mixes 1 and 2) with tensile strengths around 38 5 MPa, whilst post-curing the CHDI-based TPU results in a further increase to 43 MPa and reduces compression set from 56 to 40% (at 100°C). A comparative postcuring experiment with a PPDI-based TPU gave no real improvement in these properties (refer to compounds 4 and 5). 

Fig. 8. DSC and TMA thermogram comparison for post-cure effects on dimensional variation , sample A (TMA) o, sample A (DSC).

As shown in Figure 3.28, fracture toughness (or specific fractirre energy), Gjc, of both ME and MEH increases as microsphere content increases up to a microsphere content of 20% and thereafter tends to be more or less flat. It should be highlighted that the maximum increase of MEH is about 13 times the control epoxy system but only about 6 times the control epoxy system for ME. Some increase of the control epoxy in fracture toughness after heating may be due to post-curing effect, the interest of which is beyond the scope of this work. 

TABLE 3.7 Study of Post-Cure Effects in HNBR Post-Cure Effects Study ... 

FIGURE 3.15 Post-cure effects on HNBR compression set. (From Zeon Chemicals L.P., Ejfects of Post Curing on Zetpol 1020 (Z5.1.) [Brochure], Louisville, KY. With permission.)... 

---