Abstract
A new type of high elastic polyurea protective coating reinforced by nano silica is prepared by filler composite in order to avoid both the leakage of fluorine chemical pipelines containing highly toxic and dangerous media as well as the damage to fluorine chemical pipelines under impact loads. The aim is to improve the intrinsic safety of fluorine chemical pipelines and ensure the safety of the ecological environment, life and property. The effects of different processes and process parameters on the properties of polyurea coating were studied. The polyurea coating was blended and strengthened with nano silica modified by silane coupling agent KH-550. The suitable stirring speed, material addition sequence and nano silica concentration of the new polyurea material were put forward to prepare a new polyurea coating with excellent properties. The properties of the polyurea coating were characterized, including curing time, tensile strength, elongation at break and impact resistance. Then, by using the numerical simulation method, the protection law of polyurea coating on fluorochemical pipelines with or without polyurea coating under the impact of small balls with different speeds was studied, and the equivalent stress mitigation and energy absorption mechanism of polyurea coating were analyzed from the perspective of macro and micro mechanisms. The results show that silane coupling agent KH-550 has successfully modified nano silica, and the optimal filling concentration of modified nano silica is 4 wt%. At this time, the tensile strength of filled reinforced polyurea coating is increased to 15.7 MPa, the elongation at break is 472%, the hardness is 61 HA, and the impact resistance of the matrix material is increased by 9.7 kJ/m2. This shows that the polyurea reinforced by nano silica has excellent mechanical properties and impact resistance. The simulation results show that the polyurea coating can slow down the impact caused by the equivalent stress of small balls at different speeds. When the ball speed is 5 m/s, the equivalent stress of polyurea coating slows down to 49.3%, and the percentage of reduction of the impact caused by the equivalent stress of the polyurea coating decreases gradually with the increase of ball impact speed.