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#1158
Author: Dan Thompson, Loparex, Inc.
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Subject: There is not a substantial difference in the shelf life of either process.
I will confine my answer to easy release silicone systems on a polyethylene film, as that is a combination I have seen in the type of application mentioned. There is not a substantial difference in the shelf life of either process. In fact, at Loparex, the shelf life would be six months for either UV cured or thermally cured silicone systesms. The cure chemistries mentioned above can all lead to stable release systems which work for a variety of applications.
Now, for a word about shelf life from release liner manufacturers. The shelf life given is a conservative estimate. It includes our conventional wisdom about our products and aging studies that we have done for some (not all) of our product combinations. It also includes our business liability, and the fact that we want our customers to use our products quickly. Our stated shelf life is also influenced by the fact that we do not control the roll storage and handling practices of our customers. Still, many release liners still function quite well beyond our stated shelf life.
Finally, I'll compare the cure chemistries of the different silicone systems on polyethylene films. If we, as release liner manufacturers, do our product design correctly, all of the chemistries are well cured to low extractables, no smear, and no rub-off. But, there is a difference in the rate of reaction for those chemistries. In general, the cure chemistry of the UV-cured silicones is the fastest, as we generally see 1 to 3% extractables right off-coater. Platinum-catalyzed thermal systems would be next, followed by tin-catalyzed thermal systems. The tin-catalyzed silicone systems are designed with a slower cure rate but they do post-cure to reach a well-cured system. In terms of crosslink density of the coatings, a similar trend is followed: UV cured silicone has higher crosslink density than the thermal chemistries. So, one could argue that the UV cured chemistry is more stable because it cures faster in process and fo
So, to summarize, I've stated that the UV-cure chemistry can be argued to be more stable than the thermal systems. But, again, any of the chemistries can be used to manufacture excellent release properties on polyethylene film. A cost-benefit analysis might be useful in determining the best release liner for the application.
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