DSC, WAXD and POM were performed on the structures and morphology of a blend system being composed of PET, PEN and nucleating agent(DBS). It is concluded that the crystallization of the blends is dependent on the contents of PET and the nuclenting agent, which affect the morphology of the blends. Under certain conditions, the blends show a complex extinction pattern, with the black cross extinction accompanying black homocentric zone and fireworks scattering form, rather than that of the common spherulite.
We have reported the synthesis, morphological structure and single crystal structure of crystalline syndiotactic 1,2-polybutadiene. Now we want to study the effect of self-seeding nucleation on the crystallization behavior of it. In the report, the effects of self-seeding nucleation the crystallization behavior of syndiotactic 1,2-polybutadiene were studied by DSC and PLM techniques. The results indicated that the crystallization temperature of crystalline syndiotactic 1,2-polybutadiene increased obviously and the spherulite size decreased markedly after the process of self-seeding nucleation treatment.
The effects of self seeding nucleation on the crystallization behavior and properties of polypropylene (iPP) were studied. DSC results indicated that the crystallization temperature of iPP increased obviously after the process of self seeding nucleation. The results of polarized light microscopy showed that the spherulite size decreased markedly, as a result, the mechanical properties and the transparency of iPP were all improved.
The crystalline syndiotactic 1,2-polybutadiene was synthesized in a catalytic system consisting of iron acetylacetonate [Fe(acac) 3], triisobutylaluminum [Al(i-Bu) 3] and diethyl phosphite (DEP), and its morphological structure was investigated by transmission electron microscopy (TEM). The polymer with a melting point 179 ℃ was found to have 89.3% 1,2 polybutadiene and 86.5% syndiotacticity based on 13C NMR measurements. The bright field electron micrograph shows that the solution cast film of syndiotactic 1,2-polybutadiene consists of lamellae with lateral scale in micron size. It should be noted that the lamellae have no branching and they are almost parallel each other in localized areas. The lamellar growing direction is along b axis. Surprisingly, the electron diffraction pattern of the film only exhibits strong (hko) reflections, which indicate that the lamellae possess a single crystal-like orientation, i.e., with their c axis perpendicular to the film plane, while a and b axes in the film plane. According to the orthorhombic packing of plane zigzag chains, the cell parameters calculated from the electron diffraction pattern are a=1.102 nm, b=0.664 nm, respectively, which are completely consistent with the results reported by Natta et al..
In this paper, the isothermal crystallization kinetics of polypropylene(iPP) during self-nucleation was studied by means of differential scanning calorimetry(DSC). The iPP was melted at 438 K and then isothermally crystallized in the range of temperature between 421 and 425 K. The mechanism of nucleation and growth of iPP was discussed. The Avrami equation was applied to analyzing the process of isothermal crystallization of iPP from the melt. The average value of Avrami exponent is n=3.01, suggesting that the primary crystallization maybe corresponds to three-dimensional spherulitic growth.The K g value obtained from Lauritzen-Hoffman equation is 1.128×105 K2, which suggests that crystallization species should be regime Ⅱ. The decrease of crystallization active energy and chain folding work indicates that the self-nucleation can greatly promote the overall crystallization of iPP.
