Study On The Application Properties Of Oxidized Polyethylene Wax In Powder Coatings

Most traditional coatings use organic solvents as solvents,and harmful VOCs will appear during production and use,which not only pollutes the environment,but also poses a threat to human health.In recent years,as people's awareness of environmental protection has gradually increased,powder coatings without organic solvents have attracted widespread attention,but the pigments and fillers in powder coatings are not easily dispersed.Oxidized polyethylene wax is an excellent polar wax with a large number of carboxyl groups in the structure.It has a good affinity with basic pigments and can promote the dispersion of pigments in the system.Therefore,it is of great value to study the application of oxidized polyethylene wax in powder coatings.We use melt extrusion mixing method,using polyester resin,titanium dioxide,oxidized polyethylene wax as raw materials,calcium carbonate as filler,TGIC as curing agent,adding coupling agent,leveling agent and benzoin to prepare powder Paint,and explore the best synthesis conditions,and then characterize its performance.The results show that the leveling agent dosage is 0.5 wt%,the titanate coupling agent content reaches 0.5 wt%?0.75 wt%of the total coating,the benzoin dosage is 0.25 wt%?0.5 wt%,and the polyester resin dosage is 65 wt%,the content of pigment and filler is 20 wt%?25wt%,and the curing performance is 180?,15 min,the comprehensive performance of the coating is the best.As the temperature continues to rise,there is no exothermic peak in the coating film,indicating that the coating film is completely cured.On the basis of the above formula,an oxidized polyethylene wax?OPEW?was added to prepare an OPEW powder coating.FT-IR can be used to analyze the structural changes of powder coatings before and after curing.The dispersion of pigments of the coating film were observed through scanning electron microscopy.And explore the mechanical properties,thermal properties and water resistance of the coating film.The results showed that as the OPEW content increased,the pigments and fillers became more and more uniformly dispersed.And when the OPEW content is 8 wt%and 10 wt%,the pigment and filler are dispersed most uniformly.When the OPEW content was 15%by weight,a small amount of pigment and filler agglomerated.And the surface of the coating film is relatively smooth,without cracks and bubbles,and the cut surface of the coating film is a tightly crosslinked network structure.The coating performance of the three types of OPEW is excellent,and the performance of the powder coating film with OPEW is better than that without OPEW?except when the content of OPEW is 15 wt%?.OPEW can increase the initial decomposition temperature T0 and the maximum decomposition rate temperature of the coating film.OPEW can increase the T_g of the coating film and increase the maximum use temperature.However,too much addition will affect the final stability.The stability of OPEW-2 wt%sample is the best.Water resistance experiments were performed on the cracks of the coating film.The results showed that OPEW-0 wt%,OPEW-2 wt%,and OPEW-5 wt%powder coatings had the best water resistance.DSC was used to analyze the reaction kinetics of powder coatings.At different heating rates,powder coatings were investigated for the curing process of OPEW-0 wt%and OPEW-8 wt%,and the effect of OPEW on the curing process of powder coatings was studied.The results show that the T_g of OPEW-8 wt%powder coating is 57.1?,which is greater than the T_g of OPEW-0 wt%powder coating,which indicates that OPEW increases the storage stability of the system.Because when the T_g of the sample coating film is higher than the storage temperature?normal temperature?,the segment mobility of the polymer will be limited,and there will be no segment-level or molecular-level substance diffusion between different particles,and the system will have good chemical stability.The reaction order of OPEW-0 wt%and OPEW-8wt%samples are both 0.92.The reaction order is not an integer,indicating that the curing process is a complex physicochemical reaction.The activation energy of OPEW-0 wt%is 64.35 kJ·mol^-1,and the activation energy of OPEW-8 wt%is 60.95 kJ·mol^-1.Its size directly determines the difficulty of the curing reaction.The smaller the Ea of the reaction,the easier the curing reaction will proceed,Indicating that OPEW can promote the curing reaction.