Polyurea/polysilica hybrid resins are widely applied in construction area, e.g. to fill cavities in mining and tunneling. Furthermore, they serve as matrix in fiber reinforced plastics (FRP) for trenchless sewer repair, where glass fiber woven fabric mats are used as reinforcement.
Organic/inorganic polyurea/polysilica hybrid resin is already produced at room temperature by indirect reaction of water (from water glass) and isocyanate (from polymeric methylene diphenyl diisocyanate, PMDI) via intermediary amine groups. While creating the organic polymer (polyurea), inorganic polysilica particles are built in situ by a silification process. For stabilization of the reactive water-in-oil emulsion market established resins use fluid organic phosphate esters as phase-transfer emulsifier, catalyst and plasticizer at the same time . Because of the unfavorable diffusion of chemically non-bonded phosphates and the substitution of dangerous chemicals through REACH regulation (EG 1907/2006), recent studies focused on replacing phosphates through functionalized vegetable oils. These fulfill the functions of emulsifiers, plasticizers and phase-transfer agents, and also get chemically bonded to the matrix. Vegetable oils also raise the bio-content while having a beneficial influence on reaction viscosity, post-curing and mechanical properties .
In this work, the adhesion between fiber and matrix of newly developed phosphate-free resins was explored compared to market established resins. For high damage tolerance and enhanced lifetime a proper fiber/matrix adhesion is essential. Adhesion was improved by using reasonable coupling agents and was investigated by means of interlaminar shear strength (ILSS), double-cantilever beam (DCB), tensile properties and Charpy impact tests. Well adhesion of recently developed resins and also increase of adhesion properties by use of reasonable coupling agents were also confirmed by scanning electron microscopy (SEM).
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 Kopietz, M., Grishchuk, S., Wetzel, B., Proceedings of 32nd International Conference of the Polymer Processing Society, Lyon, France, 25.-29. July 2016.