Study On Preparation And Properties Of Polysiloxane Based Marine Antifouling Coatings

Along with the marine activities of human beings,the occurrence of marine biofouling hinders the development of marine resources,marine economy,and the protection of nation marine rights seriously.Among various approaches for marine antifouling,the application of marine antifouling coating is one of the most cost-effective methods to solve the aboved mentioned problem.To ensure the antifouling performance of the antifouling coatings,biocides,for example cuprous oxide,are widely utilized.However,the release of these antifouling agents into the marine environment seriously threatens the marine ecological environment.In light of the above-mentioned problems,hydroxyl-terminated side chain amino modified polysiloxane(APDMS),pyridinecarboxamide-PDMS ligand polymer(Py-PDMS),polyurethane-PDMS polymer(PU-PDMS)and cyclosiloxane hybrid polymer(CHP)are designed and synthesized,and then a series of polysiloxane resin-based antifouling coatings are prepared in this paper.The chemical structures of the synthetic polymers,the mechanical properties,adhesion strength,surface morphology and wettability,and antifouling performance of these antifouling coatings are studied.The antifouling mechanisms of the corresponding polysiloxane-based coating are also discussed in this paper.Hydroxyl-terminated side chain amino modified polysiloxane with different amino content were synthesized by controlling the monomer ratio of octamethylcyclotetrasiloxane(D4)and N-Aminoethyl-?-aminopropyl trimethoxysilane(AEAPDMS)via the quaternary ammonium base anion ring-opening polycondensation reaction.Then,epoxy-modified polysiloxane resin(EAPDMS)were prepared via the ring-opening reaction of amino active hydrogen and epoxy group with APDMS and epoxy resin(E51).FT-IR spectroscopy exhibits that the crosslink density of EAPDMS increases first and then decreases as the epoxy component increases in the resin system.The tensile tests and the coatings'adhesion tests show that when the APDMS ammonia value is 7.05 mmol/g and the amino segment ratio is37.5%,the tensile strength of the prepared EAPDMS-3 reaches 28.5 MPa,and the coating's adhesion strength is 7.88 MPa.The diatom active growth experiment shows that EAPDMS can inhibit the active growth of Nitzschia Closterium because of the cationic structure in the epoxy-modified polysiloxane resin structure.The diatom adhesion experiments and the marine field tests show that the epoxy modified polysiloxane coatings have better antifouling performance when compared with the PDMS-based antifouling coating(Sylgard 184).After90 days'field test in the Yellow Sea,only a few microfouling organisms are observed on these coatings'surface.By using the polycondensation reaction of amino groups with acid chlorides and isocyanates,pyridinecarboxamide-PDMS ligand polymer(Py-PDMS)and polyurethane-PDMS polymer(PU-PDMS)were synthesized separately,and then the synthesized polymers were mixed.A methanol solution of Fe Cl3 was added to the as-prepared mixture to obtain the self-healing polysiloxane coating(SHPDMS)with hydrogen bonds and ligand bonds.By regulating the content of the Fe-pyridine ligand self-healing unit in the resin system,the self-healing time of the coating can be controlled.As the content of ligand self-healing units increases in the polysiloxane system,it can be observed that the self-healing time of the coating is significantly shortened.In addinition,when the Py-PDMS mass fraction is 70%,there is a complete self-healing process of the coating within 12 hours can be witnessed at room temperature.The diatom active growth experiments,the diatom adhesion experiments and the diatom movement trajectory tests on the coating surface show that the SHPDMSs are environmentally friendly and show excellent antifouling performance.Cyclosiloxane hybrid polymer was synthesized via hydrosilylation with Karstedt's catalyst,2,4,6,8-tetramethylcyclotetrasiloxane(D4~H)and tetramethyltetravinylcyclotetrasiloxane(D4~V).Nano-indentation test shows that the cyclosiloxane polymer coating has excellent mechanical properties,the coating hardness H=0.30 GPa,the reduced modulus E=1.47 GPa,H/E=0.2.Atomic force microscopy tests show that the CHP coating has a very flat and uniform surface morphology(RMS=0.46 nm,Ra=0.36 nm,Rtm=0.79 nm,S=54 nm).The diatom active growth experiment shows that the CHP coating is environmentally friendly.The diatom adhesion experiment exhibits that the adhesion density of Nitzschia Closterium and Phaeodactylum tricornutum on the surface of the CHP coating is only 1/10 and 1/4,respectively.The diatom trajectory test shows that the smooth surface morphology of the CHP coating will provide fewer attachment points for diatom attachment,making it difficult for the diatom to find a suitable location to attach.The diatom secretion protein staining experiment shows that the exopolymeric substances(EPS)of Nacicula exigua is difficult to adhere to the CHP surface due to the its characteristics of low surface free energy and low surface roughness.DMAEA-g-CHP and SBMA-g-CHP were prepared successfully via hydrosilylation with Karstedt'scatalyst,dimethylaminoethylacrylate(DMAEA)and3-[dimethyl-[2-(2-methyl-1-oxoprop-2-enoxy)ethyl]ammonio]-1-propanesulfonate(SBMA).Atomic force microscopy tests show that the surface roughness of the modified CHP coatings increase,and the island-like protrusions can be observed on these surfaces.Underwater atomic force microscopy tests exhibit that the surface of DMAEA-g-CHP swells due to the tertiary amine component,which further enlarge the surface roughness of the DMAEA-g-CHP coating.While the surface roughness of SBMA-g-CHP coating is reduced in water,because of the formation of the dense hydration layer constructed by the combination of zwitterionic components with water.The marine bacteria adhesion tests show that,after modification,few marine bacteria can be observed on the coating surfaces.The diatom active growth and diatom adhesion experiments show that DMAEA-g-CHP surface have an inhibitory effect on diatom growth,while SBMA modified surface have no effect on the growth of Nitzschia Closterium.Diatom movement trajectory tests show that,due to the increase of surface roughness of the modified CHP coating,the adhesion density of Nacicula exigua increases 1-1.5 times compared with the CHP coating,but still exhibit excellent antifouling performance.Mussel adhesion experiments show that after DMAEA modification,the surface roughness of CHP coating and the hydrophilicity increases,and mussels tend to adhere to DMAEA-g-CHP surface.