不锈钢表面SiO2-TiO2-ZnO-CaO溶胶-凝胶涂层的热变化和化学性能

采用溶胶-凝胶法在不锈钢表面制备了SiO2-TiO2-ZnO-CaO薄膜,用差热分析(DTA)、失重分析(TG)、红外光谱(IR)和X射线衍射分析(XRD)研究了薄膜的热变化过程及晶相转变行为,利用电子显微镜观察分析了不同组成的溶胶-凝胶涂层的抗酸性和高温抗氧化性. 结果表明: 在溶胶组成为SiO2∶TiO2∶ZnO∶CaO=x∶(80-x)∶10∶10(mol%,x=20～60)的四元系统中,TiO2含量高,溶胶胶凝时间长;涂有SiO2-TiO2-ZnO-CaO薄膜的不锈钢抗酸性和抗氧化性均有显著提高.     

联合增稠对不饱和聚酯团状模塑料流变行为的研究

模压流变性能是不饱和聚酯团状模塑料(BMC)在工业压制过程中相当重要的工艺参数。传统的BMC制造工艺,由于模压过程中流变性能较差,需要较大的模压压力及较长的模压时间,这样既增大了模具损耗,也降低了工厂的生产效率。系统讨论了化学增稠剂Ca(OH)_2在模压过程中对BMC流变行为的影响,在此基础上利用结晶性树脂与Ca(OH)_2对BMC进行联合增稠,对联合增稠的BMC的平板流动性能及螺旋流动性能进行分析。结果表明,结晶性树脂与Ca(OH)_2搭配的复合增稠体系不会影响BMC的固化行为,同时可以较好地改善BMC的模压流动性能,实现低压条件下BMC的成型。     

水泥基渗透结晶型防水涂料力学性能的试验研究

水泥基渗透结晶型防水涂料是一种新型防水涂料,在混凝土中可以形成不溶于水的结晶体,填塞毛细孔道,使混凝土致密、防水,提高混凝土的耐久性。本研究通过正交试验配制水泥基渗透结晶型防水涂料,研究了不同的材料组成对其力学性能的影响,从而为水泥基渗透结晶型防水涂料的研究开发以及产品的优化提供理论依据。     

中低品位磷矿粉的机械力化学活化与活性表征

采用机械力化学法对中低品位磷矿石进行活化,考察了不同活化设备在不同活化条件下的磷活化性能,结果表明:原料磷矿石质地较致密坚硬,化学活性较低,磷浸出率非常低,只有3.1％.采用XQM2-2L变频行星球磨机机械活化,在机械活化120 min后得到了最佳的活性,磷浸出率为7.5％.采用AGO-Ⅱ高能球磨机进行实验,磷浸出率最佳值为10.9％,若在相同活化条件下,活化过程中加入助磨剂,则可进一步提高磷的浸出率,最佳值可达15.3％.     

Banded texture of photo-aligned azobenzene-containing side-chain liquid crystalline polymers

Poly(6-[4-(4-cyanophenylazo)phenoxy]x-methylene methacrylate) (P_x, x is 2 or 6) were synthesized and used to study the texture of side-chain liquid crystalline polymers (SCLCPs) after photoinduced orientation. With increasing temperature of irradiated P₂ film up to 125 °C, just above its T_g, 123 °C, a banded texture was observed for SCLCPs under polarized optical microscope (POM). There is no banded texture of irradiated P₆ (T_g, 72 °C) film when heating to 75 °C. The formation of the banded texture is considered to be due to co-existing of in-plane and out-of-plane orientation mesogens in P₂ film, which is explained in terms of a molecular model. Based on our experimental results, factors of irradiation light intensity, film thickness, and heating rate on the formation of the banded texture were studied in this work.     

Effect of complex flow kinematics on the molecular orientation distribution in injection molding of liquid crystalline copolyesters

Wide-angle X-ray scattering (WAXS) is used to probe the molecular orientation in steady isothermal complex channel flows (in situ) and in injection molded plaques (ex situ) of a new, low-cost aromatic copolyester based on the mesogen 4,4′-dihydroxy-α-methylstilbene (DHαMS). Complex orientation states arise from the competition of inhomogeneous mixed shear and extension in isothermal flows. Slit-contraction flows lead to a significant but temporary increase in the average degree of molecular orientation, suggesting that this polymer is of the ‘shear-tumbling’ type. Conversely, bimodal orientation states are observed in slit-expansion flows, where transverse extension leads to a strong reduction in the average degree of molecular orientation along the flow direction. Similar bimodal orientation states are observed in injection molded plaques, suggesting that these kinematic concepts translate rather directly to the more complex transient non-isothermal case of injection molding. Variations in orientation state induced by changes in plaque thickness may be rationalized by systematic changes in the relative importance of shear and extension. These results suggest a complementary perspective on ‘skin-core’ morphologies in liquid crystalline polymer moldings, and provide a clear conceptual link between more fundamental studies in isothermal flows and structure development during processing.     

Determination of the molecular orientation in the polymeric liquid crystalline systems by low frequency Raman spectroscopy

Anisotropic polymer composites with fixed, oriented liquid crystalline organisation prepared by in situ photopolymerisation of acrylic or methacrylic acids in several cellulose derivatives were investigated by low frequency Raman scattering. The results were interpreted basing on a model of non-continuous structure of polymer glasses. The Raman investigations have shown that the macromolecules of the non-mesogenic (acrylic) component are oriented in the anisotropic composites, and that the orientation of the polyacrylic chains is more pronounced in the composites with higher concentration of the liquid crystalline cellulose derivative. It was found, that the interactions between the components play a crucial role in the formation of the composites (template-like photopolymerisation) and they determine their supramolecular structure. The liquid crystalline cellulose derivatives able to form hydrogen bonds play a role of specific cross-linking agents, while the cellulose derivatives with aliphatic side chains work as plasticisers.     

Mesomorphic properties of cholesteric side‐chain liquid crystalline polysiloxanes and elastomers

A series of crosslinked liquid crystalline polymers and corresponding uncrosslinked liquid crystalline polymers were prepared by graft copolymerization. Their liquid crystalline properties were characterized by differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffraction measurements. The results showed that the crosslinking obtained in the isotropic state and the introduction of nonmesogenic crosslinking units into a polymeric structure could cause additional reduction of the clearing point (T_i) of the crosslinked polymers, compared with the corresponding uncrosslinked polymers. The crosslinked polymers (P‐2–P‐4) with a low crosslinking density exhibited cholesteric phases as did the uncrosslinked polymers. In contrast, a high crosslinking density made the crosslinked polymer P‐5 lose its thermotropic liquid crystalline property. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 773–778, 2004     

Effects of convergent flow on in situ fibrillation of TLCP in PEN

A polymer melt entering a capillary die from a cylinder undergoes a convergent flow in which there is a complex combination of extensional and shear flows. The convergent flow plays an important role in controlling the in situ fibrillation of thermotropic liquid crystalline polymer (TLCP) in a thermoplastic matrix melt. This study examines effects of the convergent flow on development of TLCP fibrils in a TLCP/poly(ethylene naphthalate) (PEN) blend. A capillary rheometer was used and the extent of the convergent flow was varied by changing capillary dimension and shear rate. With a given capillary die, the TLCP fibrillation was found to increase with increasing shear rate because of the increased deformation of TLCP droplets. The establishment of a fully developed shear velocity profile by using a relatively long die is considered to be necessary to retain the TLCP fibrils initiated in the convergent flow region. At a given high shear rate, TLCP fibrillation improves with increasing capillary diameter (≤2 mm) because of the increased difference in velocity between the capillary and the cylinder. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1505–1513, 2004     

Thermotropic liquid‐crystalline polyphosphate esters containing phenolphthalein moiety

A new series of thermotropic liquid‐crystalline (LC) polyphosphate esters containing phenolphthalein as a part of their mesogen has been synthesized by a solution polycondensation method. The even‐numbered methylene spacers were varied from 2–10, and ethyl phosphate was used as a phosphorus heterogeneity. Thermal analysis showed that these polymers are stable up to 275–342°C with high char yield. All of the polymers exhibited liquid‐crystalline properties except for Polymers I and VI. Differential scanning calorimetry (DSC) confirmed the mesophase formation of the polymers. The glass transition temperature (T_g) and melting temperature (T_m) of the polymers were considerably low. A polymer containing phenolphthalein alone as a rigid segment with decamethylene spacers was also synthesized, but it did not show birefringent melt properties. These results reveal that phenolphthalein alone cannot act as a mesogen, whereas phenolphthalein phenylester can. Molecular modeling studies and conformational analysis confirmed that the steric hindrance of phenylester and the conjugation effect could explain the promotion of mesogenic behavior by phenolphthalein phenylester. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 194–200, 2004