Preparation And Application Of Tung Oil Microcapsules In Self-healing And Self-lubricating Epoxy Coatings

Microcapsules with different functions have been widely used in self-healing and self-lubricating materials.Polymer composites are susceptible to generate friction,wear and micro-crack during work which not only resulted in a waste of energy,but also reduced production efficiency and caused safety accidents.Self-healing and self-lubricating materials is one of the effective way to solve the problem.Microcapsules containing self-healing agent and lubricant are applied in polymer composite to make materials with self-healing and self-lubricating function,so as to effectively reduce the friction or microcracks produced by external force.In this paper,a novel microcapsule with self-healing and self-lubricating function was prepared which realized an effective combination of self-healing and self-lubricating technology and has a wide range of applications prospect.Poly(urea-formaldehyde)(PUF)and polysulfone(PSF)microcapsules loaded with tung oil as core materials were prepared via the in-situ polymerization and solvent evaporation technology.The optimum encapsulation parameters were investigated by examing the effect of the effect type and concentration of dispersants,stirring speed and mass ratio of core to shell material.And then the properties of prepared microcapsules such as surface morphology,particle size,shell thickness,encapsulation efficiency of microcapsules and thermal properties were characterized by scanning electron microscopy,optical microscopy,thermo-gravimetric analyzer and else.The results showed that the Reax 88 A with the concentration of 1 g/L was used as emulsifier,the mass ratio of core to shell was 2:1,stirring speed was 800 r/min,pH=3.Under above conditions,synthesized PUF microcapsules had regular shape structure,the content capacity of 60.7% was achieved,the thermal stable temperature were 240 ?.The PSF microcapsules had more compact surface and regular shape structure under the following conditions: 0.8 wt% gelatin and 1 wt% polyvinyl alcohol mixed dispersant solutions,stirring speed of 700 r/min,the ratio of core to shell of 1.25:1.The content capacity of about 54.2% was achieved.The average diameter is approximately 130 ?m and shell thickness was 10-20 ?m.The microcapsules have high thermal stability with the initial decomposition temperature of 350?.Self-healing epoxy coatings were prepared by incorporating the microcapsules into epoxy resin.Investigations by salt-immersed corrosion tests demonstrated the coatings have an excellent performance of corrosion resistance,the corrosion resistance gets better as the increasing of microcapsules content.Besides,epoxy coatings demonstrated a favourable self-lubricating performance with the add of micropcapsules.The friction coefficient and wear rate were the lowest at the microcapsules content of 10 wt%,the PUF was 0.38 and 8.26×10-14 m3/Nm,the PSF was 0.35 and 13.10×10-14 m3/Nm.Finally,the self-healing and self-lubricating mechanism were also discussed.