Modification Of Natural Chitosan And Its Application In Antifouling Coatings

With the development of science and technology,people are more frequent in the development and utilization of the oceans.The problems caused by marine fouling on ships and marine equipment have become increasingly obvious,which has brought manpower and material resources losses.At present,the main way to solve the marine fouling is to brush marine anti-fouling paints coatings,anti-fouling agents plays a key component of anti-fouling,therefore studing a new type of environmentally friendly marine anti-fouling agent to solve the fouling of marine organisms plays a role that can not be ignored.In this paper,chitosan was choosed as the basic research materials.The different molecular weight chitosan and chitosan chemically modified were studied about anti-bacterial and anti-fouling performance,and as an antifouling agent chitosan was added to the laboratory homemade zinc acrylic resin anti-fouling paint to have a raft test.The main work is as follows:Three kinds of chitosan of low molecular weight chitosan,medium molecular weight chitosan and high molecular weight chitosan were choosed.The antibacterial ability of three kinds of chitosan on Escherichia coli,Staphylococcus aureus was tested by inhibition zone method,and the plate count method was used to determine the three kinds of chitosan on the resistance of seaweeds of Nitzschia closterium f.minutissima,and chitosan as an antifouling agent was added to the laboratory homemade of zinc acrylate resin,then prepared into paint to havea raft test in Rongcheng Weihai.The results showed that low molecular weight chitosan had better antimicrobial,anti-seaweed and antifouling performance than the other two kinds of chitosan.Chitosan derivatives with double antibacterial functional groups were synthesized by two-step method using C2-NH2 and C6-OH active groups of chitosan.FT-IR shows that esterification of benzoyl chloride with C6-OH and quaternization of C2-NH2,so that chitosan has two antibacterial groups.At the same time,monofunctional chitosan-benzoylchitosan and quaternized chitosan were synthesized respectively.Antimicrobial,anti-seaweed and antifouling properties tests show that bifunctional chitosan derivatives are stronger than monofunctional chitosan and unmodified chitosan.N,O-carboxymethyl chitosan was synthesized by the reaction of chloroacetic acid with chitosan C₂-NH₂ and C₆-OH active groups easily,and then copper ions were introduced to synthesize N,O-carboxymethyl chitosan copper chelate and a novel antifouling agent was synthesized.At the same time,directly introducting copper ions to raw materials chitosan to prepare another antifouling agent chitosan copper.The results of FT-IR、XRD and TGA showed that copper ion successfully chelated with chitosan and chitosan derivatives.The copper ions release of antifouling agent was test indirectly by conductivity meter and the result showed that copper ions release rate of N,O-carboxymethyl chitosan is slower than chitosan copper.Antibacterial,anti-seaweed and anti-fouling performance tests showed that N,O-carboxymethyl chitosan copper effect is better than chitosan copper.Chitosan has sustained release effect.On the basis of the fifth chapter,the introduction of ferroferric oxide to prepare chitosan coated ferroferric oxide,followed by thiourea modification and introduction of copper ions to obtain the chelates of magnetic chitosan copper.The changes of the chitosan after the modification were characterized by means of FT-IR,XRD and polarized light microscope.The release rate of copper ions of the magnetic chitosan copper in the presence of external magnetic field was found to be slower than that in tabsence of external magnetic field by conductivity meter.Antibacterial,anti-seaweed and anti-fouling performance tests showed that magnetic chitosan copper has good antibacterial and anti-fouling effect.