Preparation Of Water-Based Polyaniline-Hydroxyl Acrylic Dispersion And Its Anticorrosive Properties

As the process of industrialization continues to accelerate,coatings are more widely used in the protection of metals and buildings.In the face of environmental problems caused by traditional solvent-based coatings,the development of environmentally friendly water-based coatings has gradually become the main direction of coating research.Among them,water-based two-component polyurethane coatings have attracted the research interest of many scientific researchers due to their excellent properties.They are mainly composed of water-based hydroxyl components and hydrophilic modified isocyanate curing agents.Water-based hydroxy acrylic resins are the most commonly used water-based hydroxyl groups.However,the performance of water-based industrial coatings prepared from a single species of water-based acrylic resin is not comparable to that of solvent-based coatings.In order to improve its performance,it needs to be modified or added with other materials for composite use.Among many materials,polyaniline is an excellent anti-corrosion pigment,but its structure is rigid and requires water-based treatment before it can be used together with water-based paint.In this thesis,a secondary dispersion of water-based hydroxy acrylate was firstly prepared,and then polyaniline was synthesized using phosphoric acid-modified polyvinyl alcohol as a stabilizer,and a pigment with better water dispersibility—aqueous polyaniline was obtained.It is used in the water-based hydroxyl acrylic dispersion to obtain the water-based hydroxyl acrylic polyaniline anticorrosive coating,and it is matched with Bayer 2655 curing agent to prepare a coating with good water resistance,acid and alkali resistance.The main research contents of this thesis are as follows:When acrylic acid was used as the hydrophilic monomer,an aqueous hydroxy acrylate secondary dispersion was prepared by solution polymerization.The influences of the reaction process and the amount of each component on the dispersion were investigated.The results show that the amount of solvent is 20%of the total mass of monomers,when the degree of neutralization is 100%,the state of the dispersion obtained is best,with a solid content of 45%.The dispersion was analyzed and characterized by viscometer,gel permeation chromatography,nanoparticle size and zeta potentiometer,FT-IR and other test methods.The results showed that the viscosity of the dispersion was 336 mpa·s,the molecular weight was 37495 Da,and the average particle size was 185 nm.The polymer dispersibility index(PDI)is 0.147.When Bayer2655 was used as the curing agent,the prepared coating has excellent performance,its pencil hardness is H,adhesion is 0,and gloss is 85.The hydrochloric acid directly doped polyaniline(PANI HCl)was prepared by chemical oxidation method.When urea was used as a catalyst,polyvinyl alcohol and phosphoric acid were used as raw materials,and deionized water was used as a solvent,partially phosphorylated polyvinyl alcohol(PVA)was prepared.Under the condition of stabilizer and dopant,the hydrochloric acid doped polyaniline(P-PVA/PANI HCl)of partially phosphorylated polyvinyl alcohol and the phosphoric acid doped polyaniline of partially phosphorylated polyvinyl alcohol were prepared(P-PVA/PANI H₃PO₄).The factors affecting the synthesis of P-PVA/PANI HCl were explored,and the differences in the suspension of the three polyanilines in water were compared.The structure and morphology of the product were characterized by FT-IR and TEM.The experimental results show that under the conditions of direct addition of PVA,when the mass ratio of aniline:P-PVA=1:1.25,the molar ratio of aniline:ammonium persulfate=2:1,and the molar ratio of hydrochloric acid is An:HCl=2:3,the prepared P-PVA/PANI HCl has the best suspension in water,and the suspension time is 1.5 h.The morphology of the product is observed by TEM,and it is found that PANI HCl is easy to agglomerate into flakes,while P-PVA/PANI HCl is spherical with good dispersibility.Different contents of P-PVA/PANI HCl were added to the self-made water-borne hydroxyl acrylic dispersion,combined with Bayer 2655 curing agent.After curing at room temperature for 7 days,the coating state was observed,and the acid,alkali and salt resistance accelerated test was carried out.The results show that the coating surface is flat and smooth when the content is 0?0.4%,and the coating surface has obvious defects when the content is 0.5%.Compared with the coating without adding 0.4%,the acid resistance increased to 48 hours,the alkali resistance increased to 48 hours,and the salt water resistance increased to 160 hours.The electrochemical polarization curves of the coating with 0.4%P-PVA/PANI HCl and the coating with 0%P-PVA/PANI HCl were analyzed.The results showed that the coating with 0.4%P-PVA/PANI HCl had low corrosion efficiency and obvious anti-corrosion effect.