Research On Preparation,Structural And Performance Of Intelligent Self-repairing Microcapsule/Basalt Fiber

Basalt fiber(BF),a high-performance fiber produced by pulverized rock-basalt as raw material,has excellent high-temperature resistance and heat insulation properties,good mechanical properties,stable chemical properties,excellent sound insulation and electrical insulation properties.It is also an environmentally friendly green material which is widely used in aerospace,firefighting,military,automobile,civil engineering,environmental protection and other fields.In order to improve the flexural properties of BF for better comprehensive quality and expanded applications,this paper imitated the self-repairing ability of organisms and formed double-layer microcapsule by subsequently coating the repairing agents and curing agents which can effectively and rapidly generate network macromolecules to modify BF with smooth and small surface area,so as to realize the intelligent self-healing of BF.At the same time,the self-repairing mechanism was explored.For this purpose,single-layer microcapsules were firstly prepared byin-situ polymerization with the melamine-urea-formaldehyde copolymer(MUF)as the capsule wall and the epoxy resin(E-51)as the core.And then on whose surface the curing agent(DDS)was adsorbed.Finally,double-layer microcapsules were obtained with MUF as the second capsule wall.The preparation process of microcapsules and coating process were optimized based on the microstructure,chemical structure and thermal stability analysis of microcapsule and microcapsule/BF.Emphasis was placed on the self-healing mechanism of microcapsule/BF.The conclusions were as following:(1)The optimum process for preparing the single-layer microcapsules is as follows: the emulsifier sodium dodecyl benzene sulfonate(SDBS)was used in an amount of 0.5 g,the stirring speed was 2000 r/min,the core-wall ratio was0.5:1,and the end point pH was 3.5,and the curing time was 2.5 h.Single-layer microcapsules were uniform in size with regular morphology and dense structure.Their size was in the range of 200~1280 nm.The infrared analysis showed that MUF was successfully covered on the surface of the core without chemical reaction occurs between them.The TG curve indicates that the core content was high,and the heat stable temperature was about 120 °C.(2)The DDS suspension was treated with Tween with a mass fraction of0.3%.The optimized adsorption of DDS on the surface of single-layer microcapsules was for 60 min at pH=4 with the mass ratio of DDS to single-layer microcapsules of 1:4.When the amount of the single-layer microcapsules was 10 g,the resulting microcapsules with obvious double-layerstructure showed more regular morphology and denser surface.Their size was in the range of 125~2700 nm.Both infrared and TG curve analysis proved the double-layer structure,and the heat stable temperature of double-layer microcapsules was around 120 °C.(3)The basalt yarn treated by a finishing liquid with waterborne polyurethane(WPU)concentration of 90% and microcapsule content of 30%showed the best coating rate and tensile fracture property.Its properties had no change during the coating process and the thermal decomposition temperature was 120℃.The microcapsule/WPU/ basalt fabric had tensile fracture properties,burst strength,and wrinkle recovery properties superior to WPU/basalt fabric and basalt fabrics.The mechanical properties of microcapsule-bearing basalt fabrics were self-healing.(4)The self-healing mechanism of microcapsule/BF can be described as follows.Upon basalt fiber was damaged,the microcapsule was broken due to crack propagation.The outflowing repair agent and curing agent were polymerized forming network macromolecular to repair the crack,and thus the performance of BF.