Exerimental Study On Polyurethane Wet-sensitive Composite Material Construction And Repair Of Leaky Water Supply Pipeline

Due to the increased load of urban water supply pipe network and the aging of pipe network operation,the leakage of water supply pipe is widespread.Compared with the leakage rate of about 10 % in developed countries,the leakage rate of China's water supply network is relatively serious.In 2017,the annual average leakage rate of China's urban pipe network reached 14.71 %,and the leakage rate of some backward rural areas was even more than 40 %.According to the investigation,circular hole and crack defects account for a high proportion in the leakage pipeline.Existing pipeline repair technology has high cost,small application range,strong equipment specificity and complex construction,so it is necessary to develop simpler and more efficient pipeline quick repair technology for local leakage pipelines.The research on the synthesis of wet sensitive composites was carried out,based on the advantages and disadvantages of self-adhesive and adhesive water-stopping materials,the tensile properties and stress-strain curves of NR/PE blend elastomer,SEBS hydrophobic elastomer and polyurethane film were compared,preferably a high elastic high strength 0.4 mm polyurethane film as the base materials of the wet-sensitive composite material.Theoretically,it can have a good lasting repair effect on the pipeline.Moreover,the absorption rate of soaking water is less than 1 %,and the quality loss rate is lower than 0.8 %.There is no organic substance residue,which has little impact on the water quality and meets the hygienic conditions of contact drinking water.Through the analysis of physical and chemical properties and water quality safety of the moisture-sensitive polyurethane membrane matrix composite,it was found that the tensile strength of the wet-sensitive composite material was more than 26 MPa,and the elongation at fracture was up to 698.1 %,which was far greater than the traditional water-sealing material,and the single layer's hydraulic resistance capacity was 80 % higher than that of the base material.It has low tensile property loss after soaking,strong waterproof adhesion ability,excellent fatigue resistance and good chemical resistance.Theoretically,the wet-sensitive composite material can maintain a good and lasting pipe remediation effect.The application characteristics of wet-sensitive composite materials were studied in laboratory water supply pipeline system.The repair effect was characterized by comparing the critical sealing pressure of the repaired pipeline.The results showed that the lap width of the repaired layer increased,the critical sealing pressure increased,and the trend decreased.With the increase of material width,the critical watertight pressure first increases and then decreases.The number of repair layers is approximately proportional to the critical watertight pressure.When repairing 53 mm galvanized steel pipe,when the length of the beyond defect part of the repair layer is more than 5 cm,the influence of increasing length on the increase of critical watertight pressure can be almost ignored.The critical watertight pressure decreases when the defect area increases.When the water pressure is less than 0.1 MPa,the critical water stop pressure of all pipelines can reach more than 0.25 MPa.The optimal repair parameters are determined as follows: the lap width of the repair layer is 1/2 of the material width,the material width is 25 mm,and the repair pressure with water is less than 0.1 MPa.After the failure of repair,the tensile properties and interlaminar adhesion of the wet-sensitive composite were significantly reduced,and the microstructure showed obvious cracks.But its soaking quality loss rate is still very low,will not cause bad effects on water quality.In this project,polyurethane wet-sensitive composite material was constructed,its physical and chemical properties were studied and applied to test,providing certain support and theoretical basis for the rapid repair technology development of small pipe diameter partial leakage pipelines.The implementation of the research results can effectively reduce the repair cost,greatly shorten the construction time,effectively control the leakage of pipe network and accelerate the realization of the leakage rate control target.