半结晶聚酯(PET)的二相共存结构的表征

CHARACTERIZATION OF THE TWO-PHASE STRUCTURE IN SEMICRYSTALLINE POLY(ETHYLENE TEREPHTHALATE)

采用X射线衍射对称反射法 ,对半结晶聚酯PET2 试样收集粉末X射线衍射全图 (XDWP)数据 ,用Rietveld方法和Fourier过滤技术 ,对XDWP拟合并分离成结晶衍射峰之和CR2 和非晶散射峰之和AM2 两部分 ,与此同时获得PET2 试样的结晶相CR2 的三斜晶系晶胞参数 :a =0 .44 5 ,b =0 .5 92 ,c =1.0 72nm ,α =99.6 ,β =116 .9,γ =111.9(°) ,结晶密度dc=1.495 (g cm3) .然后由AM2 计算的约化径向分布函数G2 (r) ,得到表征非晶相结构的 3个主峰G2 1 (r)=0 .15 0 ,G2 2 (r) =0 .2 5 4,G2 3(r) =0 .46 0 (nm) .提出用“B个非晶散射峰At 之和”表达非晶相的散射曲线 ,并就PET2试样二相共存时的结晶相和非晶相的结构参数的可靠性和合理性进行了全面的诠释 .据此对半结晶PET2 的二相共存结构进行了表征 .研究表明 ,联用Rietveld方法、Fourier过滤技术和径向分布函数 (RDF)分析这一综合手段 。

The X-ray diffraction whole pattern (XDWP) data of semicrystalline poly (ethylene terephthalate) PET2 sample were collected in the symmetric reflection geometry on a diffractometer, employing a copper target ( K-alpha wavelength = 0.15418nn). The XDWP was fitted by combining the Rietveld method and Fourier filtering technique,Rietveld structure refinement for PET2 crystalline phase was done,the unit-cell parameters obtained being a = 0.445, b = 0.592, c = 1.072nm, alpha = 99.6, beta = 116.9, gamma = 111.9(degrees),and the density of the sample being d(c) = 1.495(g/cm(3)). Meanwhile, the XDWP was separated into two parts,CR2 crystalline region and AM(2) non-crystalline region in PET2. The reduced radial distribution function G(2)(r) was calculated from AM(2), finding three main peaks, G(21) (r) = 0.150, G(22)(r) = 0.254, G(23) ( r) = 0.460nm, which characterize the structure of the non-crystalline phase in PET2. We suggest that the amorphous curve is best taken as the sum of several non-crystalline scattering peaks. Reliability and reasonableness of the structural parameters of the crystalline phase and the non-crystalline phase are discussed. In conclusion,it is a very effective method that the combination based on the Fourier filtering technique and the full-pattern diffraction least-squares refinement (Rietveld method) and the radial distribution function analyses to study the two-phase structure in semi-crystalline polymers.