Design,Preparation And Marine Antifouling Performances Of Natural Phenolic Based Benzoxazine Polymers

Marine biofouling is the gradual settlement and accumulation of undesirable microorganisms on artificial material surfaces enabled by adhesion of proteins and polysaccharides,which is a common,persistent and substantial problem and is the cause of many issues and challenges encountered in marine industry.Marine antifouling coatings are widely used as an effective and economical approach to prevention and treatment of marine biofouling.Environmentally friendly marine antifouling systems,such as low surface energy antifouling coatings,are considered to possess the most promising prospects for application.However,the application of silicone antifouling coatings,with low surface energy,is limited by the poor mechanical properties and weak substrate adhesion.Moreover,due to the complex marine environment and the diversity of biofouling species,it is difficult to use a single antifouling feature to solve marine antifouling problem.In view of this,the room-temperature-curable benzoxazine resin were prepared,and provide experimental and theoretical basis for the development of composite low surface energy marine antifouling coatings.The main research contents are as follows:1.Urushiol-based benzoxazine copper polymer（UBCP）was synthesized using natural product urushiol and n-octylamine,paraformaldehyde as the reactants,and then CuCl₂ as the catalyst for further reaction.UBCP can be cured into films at room temperature,which have strong substrate adhesion,smooth and dense surface,and controllable release of effective copper ion at minimized concentrations.Moreover,UBCP exhibits excellent antifouling performance,with both fouling release and antifoulant release characteristics.The antibacterial performance of UBCP towards typical Gram-negative bacteria（E.coli）and Gram-positive bacteria（S.aureus）both more than 99.99%,while its ability to inhibit algal activity is above 99%,and the surface of UBCP can effectively prevent microbial adhesion.In summary,UBCP is a highly effective and eco-friendly coating material and provides a promising approach to address the economic and operational issues caused by marine biofouling.2.UBCP coating exhibits good antifouling properties,but it is a hard and brittle rigid material with a large modulus,which is not conducive to the fouling release performance.UBCP/PTO composite coating was prepared by blending and modifying natural and environmentally friendly polymerized tung oil（PTO）with UBCP.The introduction of PTO with long alkane segments significantly toughened UBCP and reduced the elastic modulus（from 289.8 MPa to 43.8 MPa）of the composite coatings,weakening the adhesion of the fouling organisms to the surface and thus making it easier to remove.Moreover,the small concentration of copper ions in UBCP was released from the composite coatings and had a synergistic antifouling effect.The antifouling performances of the composite coatings were tested with three different bacteria（E.coli,S.aureus and V.alginolyticus）and two microalgae（N.closterium and P.tricornutum）,all of which were easily released from the composite coatings.This work develops a composite coating with synergistic effects of antifouling and fouling release as well as long-lasting antifouling performance using eco-friendly natural products as the main raw materials.3.Based on the flexible molecular designability of benzoxazine,a long and flexible chain octadecylamine structure was introduced into the benzoxazine structure,and urushiol octadecylamine benzoxazine polymer（UDHP）and cardanol stearylamine benzoxazine（CDHP）was prepared by thermosetting ring-opening polymerization.The surface free energy of UDHP and CDHP coatings is significantly lower than that of urushiol octylamine benzoxazine polymer（UOHP）and cardanol octylamine benzoxazine polymer（COHP）due to the presence of flexible octadecyl chains.The water contact angel（WCA）of UDHP and CDHP are 109.2°±2.0°and 110.9°±1.5°,and the elastic moduli are 196.8 MPa and 24.0MPa,respectively,which are significantly lower than that of UOHP（978.1 Mpa）and COHP（732.5 Mpa）.The results of antifouling performance test showed that the three bacteria and three marine microalgal cells adhered the least amount on the surface of the UDHP and CDHP coatings,which mainly due to the lower surface energy and modulus,the adhesion of bacteria and algal cells on the coating surface is weak,showing good fouling release performance.4.The polybenzoxazine coating with low surface energy and low modulus indicates good fouling release performance,but this is mainly a dynamic antifouling performance,the static antifouling performance is poor.In order to improve the static antifouling performance,there two strategies such as add a relatively non-toxic and harmless eco-friendly antifouling agent or graft antifouling groups on the coating surface to kill or repel fouling organisms and improve static antifouling performance.Therefore,an eco-friendly antifouling agent,silver nanoparticles（AgNPs）,was selected for this part of the work.That is,polybenzoxazine/AgNPs composite coatings were prepared by in-situ reduction of the abundant phenolic hydroxyl groups in urushiol-based benzoxazine.The antibacterial properties of the composite coating gradually increased with the increase of Ag content.When the Ag content was 1%,the antibacterial rates of the composite antifouling coating toward E.coli,S.aureus,V.alginolyticus and Bacillus sp.were 100%,99.7±0.2%,100%and 99.1±0.3%,respectively.Moreover,the adhesion amount of bacteria and marine microalgae cells on the coating surface is also significantly reduced,showing good antibacterial and antifouling performance,thereby improving the poor static antifouling properties of the low modulus benzoxazine polymer antifouling coating,and composite coating is a novel eco-friendly marine antifouling coating that combines both dynamic and static antifouling effects.5.Based on the physical and chemical properties of the antifouling coating,a polymer with antibacterial effect was designed and synthesized as an antifouling coating.Urushiol rosin amine benzoxazine monomer（URB）was prepared using rosin amine with antibacterial and algae-inhibiting effect as amine source,reacted with urushiol and paraformaldehyde.Then,urushiol rosin amine benzoxazine polymer（URHP）was prepared by thermosetting ring-opening polymerization.The results of antibacterial performance test showed that the antibacterial rates of URHP toward E.coli,S.aureus,V.alginolyticus and Bacillus sp.were 85.5±5.0%,77.5±5.0%,75.3±1.8%and 74.0±5.7%,respectively.Furthermore,the adhesion of bacteria and marine microalgae cells on the coating surface was also significantly reduced.These results indicate that URHP has good antibacterial and antifouling properties.