Preparation And Properties Of FCF-301-Modified Waterborne PVDF Coating

PVDF coating has advantage of highest levels of durability and substrate protection,and it has been widely used in aluminium for architectural applications.With low VOC content,widely available and a huge market with big potential,aqueous PVDF paint becomes one of the directions for environmentally-friendly transformation of PVDF coating.Due to the immaturity of synthetic technology and weatherability of the resin,the application of the paint is less and the research on waterborne PVDF emulsion in China is still in its early stage.FCF-301 is one of the waterborne PVDF resin,which is developed by industry-university-research cooperation.However,the structure of the resin is not explicit,until now not yet used in coatings.In this paper,a high weather-resistance paint was prepared by modification and fomulation using primary self-made PVDF emulsion of FCF-301,which filling the domestic blank,with a high application value.Firstly,the causes for poor weather-resistance of the individual use of FCF-301 were analysed.Secondly,the FCF-301has been modified and reinforced by 2K-WPU in order to improve its visual,mechanical and weatherproof performance.Thirdly,factors that affect FCF-301 hybrid coating has been studied.The results are as follows:(1)FCF-301-dominated paint shows poor appearance,gloss,mechanical properties and weatherability when used alone.From the surface of dried film,it can be seen that the hard-core fails to roll out and it remains as particle as ever.The soft-shell,as binder,plays a role in keeping the core.~1H-NMR and FT-IR suggested that the hard-core was PVDF,and there was no transition layer on it.Hydroxyl acrylic polymer as the soft-shell only act as emulsifier to the core.To summarise,FCF-301 cannot be used directly in coating,it must be enhanced beforehand.(2)Aimed at the problem of fixation and capsulation,adopting 2K-WPU to reinforce the hard-core is considered in this paper.In order to study the miscibility and intermolecular interaction of the PVDF-core/2K-WPU interface,the hybrids were prepared by means of dissolving-mixing-casting method.The results of SEM indicate that HDI-A2470 was well compatible with PVDF,and a transition layer between two phases was appeared.DMA tests showed that the content of PVDF was 10 wt%in blend exhibited a single glass transition temperature,which indicated that HDI-A2470 and PVDF were completely miscible.However,the content of PVDF was 50~90 wt%,blends have been shown to be partially compatible.FT-IR and XRD test results showed that there's hydrogen bonding and dipole-dipole interaction between acrylic and PVDF.In addition,the polymer of HDI-A2470 hinders the steering and migration of the PVDF chain.Mechanical property showed that the high cohesional strength could convert the film from rigid to flexible.Finally,empirical study indicates that the HDI-A2470/FCF-301 coating had good compatibility,reached gloss to 48.6°,adhesion strength to level 1,hardness to F,impact properties to 50 kg·cm,which meet the need of practical application.(3)In order to promote the weathering performance of hybrid coating,influencing factors were studied synthetically.The results are as follows:Because the hard-core of FCF-301 is dependent on the 2K-WPU fixation and capsulation,making the weatherability of hybrid coating handicapped by its compositions of hydroxyl acrylic resin;The optimal weatherability can be achieved when the mass ratio of FCF-301/2K-WPU=5/5;Bayhydur 305 is superior to XP 2655 in this aspect,the weatherability increases with the mole ratio of NCO/OH,and the feasible result was NCO/OH=1.8;The increasing of temperature makes the hard-core split open,which is helpful for raising the contact area between the binder and hard-core,The optimal durability can be achieved when the temperature of 90?;the weatherability of the films decrease with the P/B mass ratio.The optimal results showed that under the acceleration of UV-B/1140h,the gloss retention and chromatic aberration of 2K-WPU/FCF-301 are 80%and 1.05 respectively which close to Daikin's ZEFFLE~TMM SE-310.So,it has a certain practical significance and application prospects.