| It is difficult to produce the higher quality powder coatings for the conventionalTGIC-based powder coatings which were prepared with amorphous polyester resin due to itcould not coordinate rheological properties, glass transition temperature and reactivity. Inthis paper, a semi-crystalline polyester resin with acid value about33mgKOH/g wassynthesized by two-step direct esterification, one-step vacuum process and blockpolycondensation method. The properties of semi-crystalline polyester resin, powder coatingand film of semi-crystalline polyester powder coating were discussed. The conclusions weregiven as follows:(1)The semi-crystalline polyester resin was synthesized by two-step esterification andone-step vacuum process, which1,6-hexanediol (HDO), terephthalic (PTA) acid andisophthalic (IPA) acid as the raw material with n(HDO):n(PTA)=1.10andn(COOH):n(OH)=1.05. The structure and properties of semi-crystalline polyester resinwere characterized by FTIR, XRD, H-NMR, GPC, DSC, TG and CPC. It was found that thestructure of semi-crystalline polyester resin was IPA/HDO/PTA/HDO/IPA, with38.5%of thecrystallinity degree, the Number average molecular weight and molecular weight distributionwere3435and1.434respectively, The glass transition temperature was54.5℃, which meetthe storage stability of the powder coating. TG curve indicated that the initial degradationtemperature of semi-crystalline polyester resin was395℃,which exhibited good thermalstability. The rheological curve showed that the flowability of semi-crystalline polyester resinwas better than amorphous polyester resin.(2)The powder coatings were prepared with semi-crystalline and amorphous polyester resin.It was found that after the semi-crystalline polyester resin could improve the reactivity,rheological and stability of powder coating company with increasing of the flowability andgloss of film, while the heat resistance and pencil hardness of film decreased, and theprocessing properties of powder coating became difficult.(3)The ATR-FTIR and SEM were used to characterized the weatherability of the film, theresults showed that the anti-aging property of powder coating were decreased after thesemi-crystalline polyester resin was introduced to powder coating. ATR-FTIR monitored the absorption peaks1725cm-1reduced constantly with the increase of the aging time. By peakfitting analysis, the absorption peaks1725cm-1of semi-crystalline polyester powder coatingdecreased and appeared six new peaks in1550-1850cm-1. However, in the same position, theamorphous polyester powder coating decreased and appeared three new peaks, the resultsshowed that the degradation mechanism of semi-crystalline polyester powder coating wasmore complex than that of amorphous. Furthermore, compared the SEM photos of the twopowder coatings, the surface of semi-crystalline polyester powder coating became worse thanthe amorphous polyester powder coating. |
PDF Full Text Request