The Paa Film Crystallinity And Peo Crystallization Kinetics

The thesis was focused on the crystalline of polymer and subject were crystallimity of film and crystallization kinetics. Research objects were poly(acrylic acid) and PEO, and analytic methods were X-ray diffraction(XRD) and differential scanning calorimetry(DSC). At first, the relation between the hydrophilicity and crystallim'ty of the film of poly(acrylic acid)(PAA) and its salts were investigated. Isothermal and non-isothermal crystallization kinetics of PEO and its blend system with lithium perchlorate were discussed.The solution of poly(acrylic acid)(PAA), poly(acrylic acid sodium)(PAANa), poly(acrylic acid lithium)(PAALi) were synthesized respectively. The paintings were coated on aluminium fins by roll film method in this article. The film with different crystallinity was obtained by varying baking time and temperature.The measurement of crystallinity of film was rarely reported. Based on the feasibility of surveying film crystallinity using XRD, crystallinity of the above film were tested by XRD. Contact angles for distilled water and glycerin on the film were measured at room temperature using a contact angle tester, with a droplet technique. Water and glycerin were dropped about 10 cm above film and contact angles were recorded within 30 seconds. Surface tension of film and the spreading speed constants were calculated according to the method in reference. The relation of the film hydrophilicity, crystallinity, surface tension and spreading speed constant was deeply discussed. The studies indicated that surface tension and spreading speed constant increased, equilibrium contact angle declined with crystallinity of film increasing, that is to say, the hydrophilicity of film were improved with crystallinity of film increasing.Isothermal and non-isothermal crystallization kinetics of PEO and blend system with lithium perchlorate at different annealing temperatures and different cooling rates have been investigated by using DSC. Theisothermal crystallinity process was analyzed using Avrami, Malkin methods and its kinetics parameters were obtained. The results indicated that PEO were of two-dimension growth with athermal nucleation. The value n of blending system having little differential to PEO indicated that the growth style of crystal were uniform except nucleation style. Each curve of pure PEO show an initial linear portion, then subsequently tend to level off. This fact indicated the existence of a secondary crystallization, which was caused by spherulite impingment in the later stage of crystallization process of PEO. Activation energy associated with the overall process of PEO and its blend sysytem have been evaluated from the rates of crystallization by using Cebe method, and results testified that pure PEO formed crystal easier in isothermal condition than blend system.DSC curves of non-isothermal crystallization indicated that the degree of secondary crystallization increased as cooling rates decreasing for PEO. For non-isothermal studies, Jeziorny and a method combined the Avrami and Ozawa equation were employed to describe the non-isothermal crystallization process as well, and the kinetics parameters n, Zc, f0.5, F(T) with specific physical meaning were determined. The activation energies were 149.68KJ/mol, 159.51 KJ/mol for non-isothermal crystallization by Kissinger method, respectively. It confirmed again that pure PEO could form crystal easier than its blend system under both isothermal and non-isothermal condition.