Preparation Of Novel Silicone Elastomers Based On Tannic Acid

Due to their unique physical and chemical properties,such as aging resistance,high and low temperature resistance,biocompatibility,etc.,silicone materials have a wide range of applications in biomedicine,aviation technology,building materials and coatings,and transportation.Tannins are widely found in various plants,such as fruits,tea,coffee and so on.It has antioxidant,antiviral and biocompatible properties.Tannins have high chemical reactivity and can interact with other substances through hydrogen bonding,electrostatic interaction,coordination and ?-? stacking.Despite the excellent properties of silicone materials and tannins,elastomers based on both have not been developed and studied.In this paper,we used aminopropyl polysiloxane(PAPMS)and aminopropyl capped polydimethylsiloxane(DP-1)as raw materials and tannic acid or modified tannic acid as cross-linking agent to prepare new silicone elastomers by hydrogen bonding,covalent bonding and ammonia-ene reaction,and the properties of the elastomers were investigated in two main aspects as follows.1.New silicone elastomers were prepared by Michael addition and hydroxylation reactions using tannic acid as the cross-linking agent.The effects of solvent type,heating time,crosslinker dosage,molecular weight of PAPMS and DP-1 dosage on the properties of the elastomers were investigated.This includes the forming condition,tensile strength,elongation at break,hardness,Young's modulus and cross-link density of the elastomer.The mechanical properties of the elastomers were enhanced by the addition of reinforcing fillers.In addition,since the crosslinking system is a non-homogeneous reaction,we found that the surface morphology of the elastomer was flat and uniform by SEM.The elastomers formed at room temperature demonstrated the cross-linking mechanism as hydrogen bonding by reversibility.We demonstrated this crosslinking by FT-IR,1HNMR and MS with a small molecule reaction of catechol and n-decylamine,which is including Michael addition and hydroxylation reactions.The new elastomers were shown to be thermally stable by thermal weight loss analyzer.The binder prepared by using these two cross-linking methods has a certain bonding effect on both iron and glass,and the bonded iron specimens can bear a weight of 500g.Firstly,we grafted acryloyl group onto tannic acid using alcoholysis reaction to obtain modified tannic acid(G-TA).Using 1HNMR,we can see that the acryloyl group has been successfully grafted and the grafting rate is about 80.1%.The organosilicone elastomers were prepared by the aminole reaction between the double bond of G-TA and the amino group of aminopropyl polysiloxane.The tensile strength of the prepared elastomer was only 0.3 MPa without the addition of reinforcing filler,so we enhancedthe mechanical properties of the elastomer by adding H2000 or TS530.Experiments have shown that up to 60 parts of reinforcing filler can be added to the elastomer.The tensile strength can reach up to 6.97 MPa and the elongation at break is about 390%.Thermal aging tests on the elastomer showed that the tensile strength,elongation at break and Young's modulus of the elastomer decreased to different degrees at 180?and 5h.The thermogravimetric analyzer indicated a 5%heat loss of the elastomer at a temperature of about 413?.The elastomer was prepared under conditions where only volatile solvents were required at room temperature and the curing onset time was 23 s.Under the same conditions the elastomer demonstrated good application prospects relative to other cross-linking methods.