Crystallization morphologies and non-isothermal crystallization kinetics of isotactic polypropylene modified by α/β compounded nucleating agents |
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| Authors: | SHI Yaoqi XIN Zhong |
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| Affiliation: | State Key Laboratory of Chemical Engineering, Department of Product Engineering, School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China |
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| Abstract: | Crystallization morphologies and non-isothermal crystallization kinetics of isotactic polypropylene（iPP)modified by three α/β compounded nucleating agents（NAs)were studied by means of polarized optical microscope（POM)and differential scanning calorimeter（DSC).The size of spherulites in nucleated iPP appeared much smaller than that in pure iPP.However, iPP nucleated by different ratios of α/β compounded NAs showed different crystallization morphologies.Crystallization morphologies of nucleated iPP depended on ΔTCp(ΔTCp refers to the difference in crystallization peak temperature between nucleated iPP and pure iPP)of α and β NAs.The one with the higherΔTCp played a leading role in the crystallization process, resulting in that the crystallization morphology of nucleated iPP appeared close to that with the NA alone.Competitive nucleation would occur when the difference ofΔTCp between two NAs was not pronounced. ΔTCp was related to the concentration of NA.Thus crystallization morphologies could be adjusted by changing the ratio of α/β compounded NA.The Caze method was used to deal with non-isothermal crystallization kinetics obtained by DSC.The obtained parameters showed addition of α/β compounded nucleating agents could greatly raise crystallization peak temperature of iPP and shorten the crystallization half-time.Avrami exponent of α/β compounded nucleated iPP was close to that of iPP nucleated by the NA with the higherΔTC pindividually, which demonstrated that the crystallization process of iPP nucleated with α/β compounded NAs also depended onΔTCp of α and β NAs within the compounded system. |
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