Preparation And Characterization Of Polyurethane Modified Silicone Antifouling Materials

The fouling release coatings(FRCs)relay on the properties of low surface energy and elasticity modulus,which makes fouling marine organisms difficult to adhere on the coatings surface and weaken the adhesion strength.Even if biofouling occurs,the fouling organisms could be removed by the water flow when the ship is moving and achieve self-cleaning.The properties of self-cleaning made FRCs be a promising development tendency for long-term environmental-friendly marine biofouling prevention technology.The base resin of the FRCs is commonly composed by silicone.The silicone resin has excellent properties such as aging resistance,low surface energy,and low elastic modulus because of its unique molecular structure.However,the mechanical properties are not as good as expected and with a low adhesion strength to anticorrosive undercoat.In this paper,the polyurethane with good mechanical strength and adhesion property are used to modify the silicone to improve the mechanical properties.At the same time,the antifouling properties of the silicone resin such as low surface energy and low elastic modulus are retained to prepare an antifouling coating with good performance.(1)Silicon ethoxy group functionalized polyurethane prepolymer was prepared.Linear polyurethane modified silicone was synthesized via polycondensation of the silicon ethoxy group in the prepolymer and the silicon hydroxyl in the silicone coating resin.In this study,linear polyurethane prepolymer PUa and PUb,which possess silicon ethoxy group,were soft segment and the influence of different soft segment structures(PDMS-NH₂,PDMS-OH,and PEG-OH)on the mechanical strength,surface energy,and elastic modulus of the polyurethane modified silicone antifouling coatings were investigated.The results show that the linear polyurethane modified silicone coating has low surface energy characteristics and the contact angle is above 108°.The mechanical strength is significantly higher than silicone resin and the tensile strength of the PUb modified silicone is 0.81 MPa.The elongation at break is 206.45%.The Shore hardness is slightly increased,but still maintains a high elasticity with a higher coating adhesion strength.(2)Glycerol were used as the branching point and the molar ratio of isocyanate groups to hydroxyl groups,the molar ratio of hydroxypropyl silicone oil and polyethylene glycol were adjusted.Series of branched polyurethane prepolymers containing silicon ethoxy groups were prepared and incorporated into silicone antifouling coatings.It was found that the tensile strength of the coating increased by increasing the content of polyurethane.The tensile strength of Si-PUd20 can reach to 1.21 MPa and the elongation at break is 120.56%,which is further higher than the mechanical strength of linear polyurethane modified silicone.At the same time,the adhesion of Si-PUd20 to the anti-corrosive undercoat reaches to 2.8 MPa and the Shore hardness is 42.71 HA.The anti-adhesion performance of diatoms is also slightly improved compared with the silicone anti-fouling paint.Therefore,the modification of silicone ethoxy-contained polyurethane prepolymer to silicone antifouling coating can improve the mechanical strength and adhesion of the silicone antifouling coating,while maintaining the antifouling performance.(3)A new polyurethane silicone copolymer was designed and synthesized through the reaction of amino-terminated polydimethylsiloxane with 4,4'-dicyclohexylmethane diisocyanate(HMDI)and melamine,which is the main compound.Fumed silica,additives,talc,Fe₂O₃,etc.were combined to prepare an antifouling coating.The static water contact angle,adhesion strength,and antifouling performance of the marine antifouling samples were investigated.The polyurethane silicone copolymer resin has high strength and toughness with a tensile strength of 6.24 MPa and an elongation at break of 163.12%.The prepared antifouling coating has good hydrophobicity,and the static water contact angle is above 110°.After 30 days of immersion in marine condition,there are no apperent large scale fouling organisms on the coatings of FR-SP1,FR-SP2,FR-SP4,FR-SP5,FR-SP6,FR-SP7,FR-SP8,and FR-SP9,and the morphologies of the surfaces do not change dramatically.After 60 days,no large fouling organisms are found on the coatings of FR-SP6,FR-SP8,FR-SP9,indicating those materials possess the best antifouling performance.