Studies On Preparation, Structure And Properties Of Thermally Reversible Self-Healing Elastomers

Polymeric materials may easily suffer from damages in their manufacture and use, then the microcraks generate inside of the materials, which would reduce the material mechanical properties and diminish their using life. Self-healing polymeric materials could simulate the self-healing mechanism of organisms to heal the microcracks by theirselves to prolong the using life. There are many self-healing approaches to prepare polymeric materials. Thermally reversible self-healing material is an effective method, which takes advantage of the thermally reversible mechanism in the structure to complete the self-healing process. The characteristic of thermally reversible self-healing materials is to repair damaged parts without additional catalyst, monomer molecules or other special surface treatment. Basing on this theory, this thesis prepared and studied two thermally reversible self-healing elastmers of epoxidized natural rubber(ENR) based on physical thermal reversion and polyurethane based on chemical thermal reversion.On the one hand, ENR elastomeric materials with self-healing property was prepared whose basis material is ENR and vulcanization agent is DCP. The results show that the healing efficiency of ENR vulcanized by DCP is 76%, which is higher than that of ENR vulcanized by sulfur or phenolic resin. The research revealed that the self-healing properties of ENR are resulted from hydrogen bonding and lacking cross-linking structure in the vulcanized ENR. With the increase of the epoxidation extent of ENR, the ENR elastomeric materials perform better self-healing properties. In addition, the best treating condition to the elastmer is 60°C(healing temprature) and 24h(healing time). Finally, terpene resin was used to improve the self-healing efficiency of ENR. The results show that the highest healing efficiency of ENR/terpene resin composite was up to 100%, but the tensile strength decreased. SEM shows the terpene resin dispersed well in the ENR matrix.On the other hand, the self-healing elastomer materials based on polyurethane were also prepared in this thesis. Polyurethane elastomers were prepared by polyurethane prepolymer, 4, 4-diamino diphenyl disulfide and HDI trimers. FT-IR, 1H-NMR and GPC were used to characterize the prepolymer. The existence of hydrogen bonds with thermal reversibility is conformed by the FTIR analysis. The results show that the self-healing properties of PU elastomer derive from the thermally reversible hydrogen bonds and dynamically reversible disulfide bonds. The self-healing efficiency of elastomers prepared is as high as 95% which is 37.1% more than that of elastomers without disulfide bonds. AFM shows that the compatibility between soft and hard segments in PU elastmers extended by 4, 4,-diamino diphenyl disulfide was better than that of elastomers without disulfide bonds, which is easier to form a continuous structure between the double phases. The healed films could reach as much as 95% tensile strength of the original ones and the healing process could be performed at the same position for many times. The research revealed that the self-healing PU elastomers achieved not only high healing efficiency but also mechanical strength, which would embroad the application sphere of self-healing polyurethane elastomers.