The Development Of The High Shear Strength Of Polyurethane (pu) Pouring Sealant

Polyurethane (PU) material has excellent properties, such as high strength and elasticity, wide hardness range, low-temperature resistance, high electric-insulating property etc. The performance of PU can be adjusted in a broad range, which is a suitable system for the development of the pouring sealant with high-strength and application under low temperature. However, there are some shortcomings in preparation and application of PU, for example, complex synthetic technology and inferior bond strength. Thus, it is significant to investigate the synthetic technology of PU and modify its structure, leading its property to the requirements of the application.In this thesis, polyethylenec (N220), toluene diisocyanate (TDI),1,4-butyl glycol (BDO) were used as the main raw materials, and two-steps method was adopted to synthesis the polyurethane pouring sealant. The synthetic technology of PU was studied through using different raw materials and adjusting the ratio of raw materials components. A series of polyurethane polymers with different structure have been successfully synthesized. The shear strength properties were tested through the electronic universal testing machine, and the hardness properties were determined in a hardness account (LX-A) degree. The effects of polyurethane’s structure on its mechanical properties were studied details and the influences of various factors on material mechanical properties were also summarized. The hardness and shear strength of the polyurethane were evaluated through the investigations of the content of isocyanate, E-51epoxy resin and urea. The synthesized polyurethane materials have excellent properties with low hardness and high shear strength.The results of the synthetic technology of PU indicated that the optimum synthetic conditions of the pre-polymer, PPG2000-TDI, for PU should be operated at60℃for75min. The curing of BDO was controlled at30℃for4hours, and then the sample was placed at60℃for24hour. The as-prepared PU has the least bubbles and the excellent mechanical properties under the optimum synthetic conditions.The polyurethane structure and properties were also studied, and the results showed that comparing to the PUs modified with the isocyanate or E-51epoxy resin, the synthesized PU derived from the modification with a content of urea has a higher tensile shear strength as the samples with the same hardness condition. When the additive amount of water was maintained in the range of0-3.0%, the hardness and tensile shear strength of the samples were improved with the increase of water. When the content of water is3%, the tensile shear strength can be increased to9.68MPa, and the hardness is only85Shore A. Such PU material has a practical application value.Summary, the most effective modifying method to obtain PU with high tensile shear strength and low hardness property is to improve the interaction of hydrogen bonding, which enhances the intensity and density of physical crosslinking and improves the microphase separation of PU.