聚丙烯β型球晶形态及成因的探讨

本文主要采用扫描电子显微镜,对主含夕球晶的iPP,或其与LDPE共混的试样的表面、切面、热处理样,紫外线及光、热老化样等大量试样中的β球晶形态进行了观察,结合前人工作,对iPPβ球晶的形态及成因,提出了一些新的看法。     

等规聚丙烯β晶形态研究

本文用正交偏光显微镜和扫描电镜观察了加成核剂βIPP的晶体形态,发现偏光下βIPP为彩色树枝状,是由弧形晶片生长成的球晶,并提出了β晶是由一个中心向相反方向枝化生长的晶体模型。     

Ringed spherulites in ternary polymer blends of poly(<Emphasis Type="Italic">ε</Emphasis>-caprolactone), poly(styrene-<Emphasis Type="Italic">co</Emphasis>-acrylonitrile), and polymethacrylate

The relationship between ringed spherulite morphology, crystallization regimes/kinetics, and molecular interactions in miscible ternary blends of poly(-caprolactone) (PCL), poly(benzyl methacrylate) (PBzMA), and poly(styrene-co-acrylonitrile) (SAN) was investigated by using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). The interactions resulted in the deviation of both experimental and calculated T_gs and formation of the specific morphology of the spherulitic structure. Ring-banded spherulites were observed in the PCL/PBzMA/SAN ternary blends. The width of ring bands changed with the blend ratio and the crystallization temperature. Additionally, both composition and wt% of AN in the SAN copolymer had an apparent effect on the morphology of PCL spherulites. Both the crystallization structure of lamellae and molecular interactions greatly influenced the ring bands of PCL spherulites. Furthermore, by using the Flory–Huggins approximation, the depression of the melting point showed that interactions in the PCL/PBzMA/SAN-17 blend were greater than in the PCL/PBzMA/SAN-25 blend. In the ternary blends, the great molecular interactions between amorphous and crystalline polymer resulted in better homogeneity and a larger band period of the extinction rings in the PCL spherulites.     

Banded texture in sheared a semiflexible thermotropic liquid-crystalline polyester and its graft copolymers with polyolefins

The formation of banded texture both in a semiflexible thermotropic liquid-crystalline polyester (SBH 112, synthesized from sebacic acid, 4,4′-dihydroxybiphenyl and 4-hydroxybenzoic acid, from Eniricerche, Milan) and in a blend of SBH with graft copolymers, consisting of a polyolefin (polyethylene or polypropylene) backbone and SBH grafts (COPPE, COPPP) has been studied by polarization microscopy and by scanning electron microscopy. The influence of the preparation conditions upon the perfection, characteristics and thermal stability of the banded texture has been investigated. The results show that the banded texture formed in SBH sheared films possesses greater perfection, smaller band width and larger angle of deviation, and higher thermal stability than the banded texture formed in COPPE and COPPP prepared under similar conditions. It has been assumed that the chain rigidity of the macromolecules of the system is mainly responsible for the formation and perfection of the banded texture. Received: 17 March 2000 Accepted: 26 July 2000     

华北克拉通南缘舞阳地区太古代BIF中方解石的微区特征及地质意义研究

条带状铁建造(banded iron formation,BIF)是前寒武纪地层中广泛发育的一类富铁沉积岩,它在华北克拉通内广泛发育。在华北克拉通南缘的舞阳地区,晚太古代太华群铁山庙组BIF包含石英-磁铁矿和辉石-磁铁矿两种组合,前者的绝大部分磁铁矿颗粒均自形程度高、粒度粗大并常常紧密伴生有一定量的方解石。舞阳地区铁山庙组BIF的RAMAN, SEM, CL和EDS分析结果表明：石英-磁铁矿矿石中的磁铁矿自形程度最高、石英次之、方解石最低;方解石似条带的RAMAN分析结果指示其有序度、结晶程度沿条带的垂直方向无规律突变,明显不同于裂隙中后期热液流体沉淀形成的方解石脉;方解石发生了塑性流变并最终定位于石英和磁铁矿间的间隙内,其矿物的截面形状和展布特征明显受控于石英和磁铁矿并得到了石英颗粒间微裂隙内方解石的证实;方解石似条带的微区成份存在明显差异,这反映方解石经历了塑性流变及再次汇聚;在磁铁矿颗粒的汇聚及生长过程中,方解石充当了磁铁矿微颗粒迁移的媒介并得到了方解石中磁铁矿微颗粒局部富集现象的证实。     

Synthesis, crystallization and hydrolysis of aromatic-aliphatic copolyester: Poly(trimethylene terephthalate)-co-poly(l-lactic acid)

In this study, poly(trimethylene terephthalate)-co-poly(l-lactic acid) (PTT-co-PLLA) copolyesters with different compositions were synthesized by melt polycondensation. The crystal morphologies of PTT-co-PLLA copolyesters were investigated with polarized light microscope (PLM). It was found that PTT-co-PLLA copolyesters exhibited banded spherulites with smaller band spacing at the same degree of super-cooling compared with PTT homopolymer. The PLLA segments in those copolyesters ranged from 0 to 28.4 mol% and did not form crystals during crystallization. Hydrolysis study on PTT homopolymer and PTT-co-PLLA copolyesters was carried out in buffer solutions. PTT-co-PLLA copolyesters represented pronounced hydrolytic degradation, which increased with the content of lactyl units. And it was concluded that degradation of PTT-co-PLLA was mainly attributed to the scission of PLLA segments.     

Spherulites: How Do They Emerge at an Onset of Nonequilibrium Kinetic-Thermodynamic and Structural Singularity Addressing Conditions?

This communication addresses the question of the far-from-equilibrium growth of spherulites with different growing modes. The growth occurs in defects containing and condensed matter addressing environments of (bio)polymeric and biominerals involving outcomes. It turns out that it is possible to anticipate that, according to our considerations, there is a chance of spherulites’ emergence prior to a pure diffusion-controlled (poly)crystal growth. Specifically, we have shown that the emergence factors of the two different evolution types of spherulitic growth modes, namely, diffusion-controlled growth and mass convection-controlled growth, appear. As named by us, the unimodal crystalline Mullins–Sekerka type mode of growth, characteristic of local curvatures’ presence, seems to be more entropy-productive in its emerging (structural) nature than the so-named bimodal or Goldenfeld type mode of growth. In the latter, the local curvatures do not play any crucial roles. In turn, a liaison of amorphous and crystalline phases makes the system far better compromised to the thermodynamic-kinetic conditions it actually, and concurrently, follows. The dimensionless character of the modeling suggests that the system does not directly depend upon experimental details, manifesting somehow its quasi-universal, i.e., scaling addressing character.