Study On The Influence Of Polyurethane Chemical Structure On Its Underwater Acoustic Absorptive Properties

Underwater acoustic absorptive materials are an important class of marine special functional materials and have irreplaceable important applications in the field of ship engineering.PU(Polyurethane)elastomer materials have great potential to be new underwater acoustic absorption materials due to its excellent environmental resistance and high damping properties.The multiple designable chemical structure of the polyurethane segment can be precisely controlled by adjusting the type and content of core components such as isocyanate,polyol,chain extender and crosslinker.However,due to its particular application,there are not many studies on the intrinsic relationship between the underwater acoustic absorption properties of polyurethane elastomers and the chemical structure of polyurethanes.Therefore,in this dissertation,we took the chemical structure of polyurethane segment as the starting point,systematically studied the factors affecting the acoustic absorption properties of the prepared elastomeric materials by the core components such as polyurethane isocyanate,polyol,chain extender and crosslink density.The application of polyurethane materials in the field of underwater acoustic absorption materials provides theoretical support.The specific research contents are as follows:Polyurethane elastomers were prepared by selecting isomers of diisocyanates with different molecular structures and diisocyanates with different skeletal groups.The molecular structure parameters such as the type and spatial configuration of diisocyanate were investigated for the acoustic absorption properties of polyurethane elastomers.It indicates that the more irregular the isocyanate structure was at 0.1 MPa,the better the damping performance and underwater acoustic absorption performance of the prepared polyurethane elastomer,but the mechanical properties and seawater resistance of the material will deteriorate.The increase in the number of benzene rings of isocyanate and the enhanced symmetry of the chemical structure of the isocyanate will result in excellent mechanical properties of the resulting material,but the underwater acoustic absorption properties will be deteriorated.The polyurethane elastomer was prepared by selecting the chain extender of long chain,short chain and branched chain and changing the crosslinking density.The effect of the chain extender and crosslinking density of polyurethane elastomer on the acoustic absorption performance of water was studied.The results show that when the pressure is 0.1 MPa,the length of the chain extender and the branching degree of the chain extender have little effect on the underwater acoustic absorption performance;the change of the crosslink density only brings about the change of the mechanical properties of the material.It has little effect on the underwater acoustic absorption performance of PU elastomers.Polyurethane elastomers were prepared by selecting different kinds of polyols with different molecular weights.The effect of polyol structure on the underwater acoustic absorption properties of polyurethane elastomers was investigated.The results show that for the lower molecular weight of the same chemical structure polyols at 0.1 MPa,the better the water sound absorption performance and mechanical properties.When the chemical structure of the polyol changes,such as PPG-PU,PBA-PU,PTMG-PU and HLBH-PU,the changes of their underwater acoustic absorption performance are not obvious.However,due to its superior mechanical properties,PBA-PU,PTMG-PU and HLBH-PU can maintain a relatively good acoustic cavity structure under 3.0 MPa conditions,so that the underwater acoustic absorption under high pressure and low frequency can still be maintained.