| Releasing agent is a special kind of antifouling coating.With the sharp development of the pressure-sensitive adhesive industry,people’s demand for releasing agent is also increasing day by day.The modern market not only pursues lower releasing performance,but also requires retention of higher residual adhesion.This type of high-performance releasing agent technology is mainly monopolized by foreign countries.The internal successful cases of releasing agents also rely on fluorine-containing groups to adjust releasing performance.The high price of fluorine-containing compounds makes this type of releasing agent attractive only in the upmarket.Based on this situation,the preparation of high-performance silicone fluorine-free releasing agents is of great significance.However,the factors that affect the releasing performance,especially the photosensitive silicone release agent,are very complicated,and there is almost no in-depth research on the releasing mechanism and influencing factors at present.Therefore,studying and discussing the factors affecting the releasing performance of silicone release agents has important guiding significance for the design and development of new releasing agents.In this paper,by adjusting the chain length of silicone and the molecular structure of silicone and the thickness of releasing films,the influencing factors of the performance of different kinds of light-curing silicone hybrid polyurethane releasing agents,especially the influencing factors of releasing performance,are discussed.The full text research is as follows:First,a photosensitive silicone modified polyurethane releasing agent(SPU-1～SPU-3)with linear structure was prepared by using hydroxyalkyl double-terminated polydimethylsiloxanes of different chain lengths.Then 1173 photoinitiator and ethyl acetate(EA)are introduced for UV curing reaction to obtain release film S1～S3.Finally,through X-ray photoelectron spectroscopy(XPS),peel strength test,low-field nuclear magnetic resonance and other characterization techniques,the factors affecting releasing performance and releasing mechanism of the releasing films were analyzed.The results show that too long chain length of silicone soft segment will lead to a decrease in aging releasing performance and increase in residual adhesion,while a too short chain length of silicone soft segment will cause both aging release performance and residual adhesion to decrease at the same time.Therefore,when designing a silicone-modified polyurethane releasing agent,it is necessary to select a silicone with a moderate chain length as the soft polyurethane segment to obtain a releasing agent with excellent comprehensive performance.Secondly,the photosensitive silicone-modified polyurethane release agent(SPU-4,SPU-5)with branched structure was prepared by using dihydroxyalkyl end-capped branched polydimethylsiloxanes with different molecular structures.Then 1173 photoinitiator,EA and pentaerythritol tetraacrylate(PETTA)are introduced for UV curing reaction to obtain release film S4～S8.Finally,through XPS,PST,L-field NMR and other characterization techniques,the factors affecting the releasing performance and the release mechanism of the releasing films were analyzed.The results show that the double-capped structure is beneficial to improve the residual adhesion,while the single-capped structure is beneficial to improve the releasing performance.The presence of branched structures inhibits the formation of microphase separation structures.The curing effect of directly grafting the photosensitive group on the release agent molecule is better than the effect of introducing reactive diluent into the prepolymer.The film thickness can indirectly improve the aging releasing performance and residual adhesion.Therefore,when designing releasing agent molecules,it is necessary to take into account factors such as end-capping structure,functional group structure,degree of branching,and film thickness,etc. |
