Preparation,structure And Properties Of Microencapsuled Self-healing Additive Silicone Rubber

Polysiloxane elastomers have been widely used in construction,automotive,electronics,aviation and aerospace due to their excellent synthetic properties.However,micro-cracks might be induced in the elastomer matrix during their application,which will decline their properties and shorten their life-spans.For example,some elastomer component,applied in the space environment,will suffer from frequent variation of temperature between the high and low temperature and cosmic rays,which will deteriorate their properties,even result in their degradation.Moreover,the elastomer components are difficult to be replaced.However,self-healing elastomers can solve the problem of the frequent component replacement due to the extension of their life-span.In the present work,dual component microcapsules were prepared by in-situ polymerization with poly(urea-formaldehyde)(PUF)as the shell material.Therein,one kind of the microcapsule contains Sylgard 184A(healing agent),and another kind of the microcapsule contains hydrogen silicone oil(curing agent).The effects of surfactant type,weight ratio of core and shell materials,stir speed on the structure and properties of microcapsules were investigated.The results show that the resultant microcapsules containing hydrogenated silicone oil have smooth surface,comparatively uniform size distribution as well as suitable wall-material strength when SDBS and GA are used as the surfactants and the weight ratio of core and shell materials is 1.5:1.And the microcapsules containing hydrogenated silicone oil show better thermal resistance with an initial decomposition temperature up to 229.8?.The microcapsules containing Sylgard 184 A exhibit regular shapes and moderate wall thickness with a narrower particle size distribution using PVA as the surfactant with weight ratio of core and shell materials of 2.5:1.Furthermore,the microcapsules will show stable structure when the temperature is below 258.6?.Self-healing addition liquid silicone rubber materials were also prepared by incorporation of the microcapsules.The self-healing properties of the silicone rubber was characterized by self-healing efficiency,which is obtained by the specific values of the tensile strength of virgin and healed silicone rubber.The effect of the proportion of two microcapsules,microcapsules concentration and healing temperature on the self-healing efficiency of silicone rubber was investigated.The self-healing performance of silicone rubber was further evaluated by observing the self-healing behavior of cut surface of the silicone rubber and gap width variation of the black-and-white splicing specimen with constant load.The self-healing silicone rubber was characterized by DMA and TGA analysis.The maximum self-healing efficiency of 80.3% can be achieved with the weight ratio of the dual component microcapsules of 0.6,and with 10wt% microcapsules at 100? for 24 h.The cut width of the silicone rubber decreases with the increased healing time up to 24 h at room temperature.In addition,the average gap width of the splicing specimen increases with the prolonged loading time.When the microcapsules concentration is 10wt%,the average gap of the splicing specimen shows the minimum width.The tan? decreases with the addition of the microcapsules,however,the microcapsules concentration has minor effect on tan? and storage modulus of the silicone rubber.Meanwhile,the embedded microcapsules have little influence on the initial decomposition temperature of the silicone rubber.