I am wondering if any of you know about glue/adhesives that do not harden over time after they are applied or glue/adhesives that take a really long time to harden after application. I need the glue to temporarily hold polymer sheets before they are sewed together.
I think you could use some types of Butylrubber. If I'm not wrong from Isobutylene is derived the Post-it adhesive. However you can find Butyl tape easily in every big hardware store (especially nautical) or online.
At this link you can find some more information this is an excerpt:
Tapes and flooring adhesives Exxon butyl rubber can be used in adhesive formulations for transparent tape, hot-melt pressure sensitive adhesives, mastic for pipe wrap tape and vinyl floor tile adhesives. It can also be used for semiconducting electrical splicing tape. A rubber splicing tape must be self-fusing; i.e., when wrapped upon itself, it must fuse to the underlying layer, forming a permanent bond. The self-fusing is a result of compounding and eliminates the need for application of a separate adhesive coat. These compounds have very high tensile strengths and exhibit some degree of recovery or elasticity. Electrical splicing tapes based on Exxon butyl rubber have moisture resistance, outstanding aging resistance and good electrical properties. Polyisobutylene elastomers have long been successfully used in pressure sensitive adhesives both as primary elastomers and as tackifiers and modifiers. Exxon chlorobutyl rubber can be used alone or in blends with other polymers to achieve special properties in pressure sensitive adhesives.