Novel phosphate-free alternatives for silicate resins applied in sewer rehabilitation

Abstract

Novel organic-inorganic polyurea/polysilicate (denoted as 2P) hybrid resins were made from water glass (WG) dispersed in a mixture of polymeric methylene diphenyl diisocyanate (PMDI) containing epoxidized linseed oil (ELO) in different concentrations acting as emulsifier, plasticizer and phase-transfer-agent at the same time. ELO, made from renewable resources, replaces unfavorable chemically non-bonded organic phosphates used in common reference resins. The ratio of PMDI/WG maintained constantly at 2:1 parts by volume, where different concentrations of ELO were added (5, 10, 15, 20 and 25 vol%). The resulting 2P hybrid resins were tested by different methods. For the evaluation of the processability of new resins the initial viscosity and its progress during reaction time at room temperature (RT) was determined and monitored by Brookfield viscometry. The applicable pot life was set to reach 15 Pa·s. The progress of post-curing during 14 days at RT was investigated using Shore D hardness measurements. Fracture mechanical, three-point bending and compression tests were carried out to compare the hardened materials. In this work it is shown that ELO accelerates the curing and post-curing reactions and improves mechanical properties at concentrations with 5-15 vol%. Slight reduction of fracture toughness was observed for all concentrations of ELO except 10 vol%.