乙二醇合成工艺的研究进展

对国内外乙二醇合成的传统工艺:直接水合法、催化水合法和碳酸乙烯酯法进行了介绍;对乙二醇合成的新工艺,包括乙二醇和碳酸二甲酯联产法和C1化学法的工艺流程和发展前景进行了综述,其中,C1化学法主要分为乙烯合成法、合成气合成法和甲醛、甲醇合成法。作为合成气合成法之一的合成气偶联合成法,具有工艺要求不高、反应条件温和等优点,是目前最有希望大规模工业化生产乙二醇的工艺路线。     

TiO_2纤维的制备、表征及其光催化活性

采用常压乙二醇法制备出在可见光下具有较高催化活性的TiO2纤维。扫描电子显微镜表征结果表明,TiO2纤维直径为0.8～2.0μm、长度为5～25μm;BET比表面积和X射线衍射表征结果表明,随焙烧温度的升高,比表面积减小,TiO2纤维晶型逐渐由锐钛矿型向金红石型转变;紫外-可见漫反射光谱分析结果表明,TiO2纤维在可见光区有明显的吸收。在可见光下对甲基橙和苯酚的降解实验表明,焙烧温度为400℃时TiO2纤维的催化活性最好,对甲基橙和苯酚的降解率分别达到90.3%和84.0%;所制备的TiO2纤维比溶胶-凝胶法制备的锐钛矿型TiO2在可见光下具有更好的催化活性,原因是其能带间隙减小和吸收波长扩展到可见光区所致。     

Degradation of polyethylene terephthalate films in the presence of lubricants for HFC 134a: a critical issue for hermetic motor insulation systems

Earlier studies conducted in the use of sealed tubes with polyalkylene glycol lubricants and polyethylene terephthalete (PET) films revealed that the PET films exhibited embrittlement and (visual) degradation. This led to an investigation of PET embrittlement mechanisms with the new lubricants used with HFC 134a. The lubricants studied were three polypropylene glycols (the monol, the diol and the completely end-capped glycols), pentaerythritol ester and a blend of monol and ester. The effects of moisture content, temperature and lubricant structure were studied. All lubricants in this study were of viscosity grade ISO-32 (150 SUS). The results were compared to PET film embrittlement in the presence of CFC 12 and mineral oil. This study reconfirmed the earlier findings that the PET films must be dried to lower than 0.1 wt.% moisture content for use in hermetic systems. This paper discusses the effect of the moisture content of the lubricant and the effect of the lubricant structure on PET films. The dependence of the various mechanisms on temperature is shown. Esters and end-capped polyalkylene glycols are recommended for use with HFC 134a.     

Polyethylene mixed crystal infra-red spectroscopy: The influence of matrix isotopic species on guest conformation

The chain conformation of solution-crystallized polyethylene has previously been confirmed by infra-red spectroscopy, using the CD₂ bending bandshape for samples with a minority of the deuterated species^1–3. The method of calculating the i.r. band profile from molecular conformational models is now developed to give a more accurate representation of doublet splittings and to include the singlet component. The CH₂ bending profile is calculated for samples with a deuterated matrix, and the good agreement with experimental data indicates that the same molecular model is applicable for samples with the deuterated polymer as either guest or matrix, for identical crystallization conditions. This result implies that isotopic fractionation is unimportant under these conditions.     

In Situ Formation of a Novel Nanocomposite Structure Based on MCM-41 and Polyethylene

M41S materials are prepared by in situ assembly of inorganic precursors and organic template and can be viewed as nanocomposites of the siliceous phase and organic surfactant. Calcination of these precursors gives the M41S materials that have been used to prepare novel nanocomposite structures, in which the organic phase inside the nano-sized pores is isolated by the nano-sized inorganic pore walls. The nanocomposite structures can be formed by in situ polymerization of monomers inside the channels. Polymerization of ethylene takes place inside the nano-sized pores, producing the desired nanocomposite structure. The resulting polyethylene was found to be a mixture of crystalline and amorphous phases.     

Photostability of polyetherurethaneureas

Polyetherurethaneureas (PEUUs) were synthesised from polyethylene-glycols (PEGs) of molecular weight 400, 600 and 1000, 4,4′-diphenylmethanediisocyanate (MDI) and aliphatic diamine chain extenders, 1,3-propanediamine (PDA) and 1,6-hexanediamine (HDA). Polymer films were irradiated with 365 nm light at 293 K and the effects of polyether soft segment length and urea hard segment on photo-oxidative stability were studied by following the variation in weight-average molecular weight (M _w), gel formation and stress-strain properties. Changes in ultraviolet and infrared spectroscopy were monitored on photo-oxidation and hydroperoxide content determined. The soft segment length was increased by increasing the molecular weight of PEG from 400 to 1000 and hard segment structure was changed by variation of diamine. It was noted that the structure of urea and polyether soft segment length plays an important role in photostability of PEUUs. PDA chain extended PEUUs were more stable than HDA chain extended PEUUs.     

Dynamic properties of carbon black filled chlorinated polyethylene/hindered phenol blends

Aggregates of carbon black (CB) in a polymer matrix have a tendency to form a CB network. The dynamic mechanical properties of binary systems of chlorinated polyethylene (CPE) and CB or 3,9‐bis{1,1‐dimethyl‐2[β‐(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyloxy]ethyl}‐2,4,8,10‐tetraoxaspiro[5,5]‐undecane (AO‐80) and their ternary systems were investigated. It was found that the dynamic mechanical properties of those systems depend on the colloidal properties, surface oxides, and surface modification of CB. For binary systems of CPE and CB, oxidized CB gives a high modulus at low strain amplitude and a large Payne effect compared with untreated CB. In contrast, the reverse effect was observed for their ternary systems. Consequently, a good micro‐dispersion is obtainable by surface modification due to physical adsorption of AO‐80 on oxidized CB particles via hydrogen bonds. © 2003 Society of Chemical Industry     

Examination of the role of oxygen in the photografting of methacrylic acid on a polyethylene film with a mixed solvent consisting of water and organic solvents

The photografting of methacrylic acid (MAA) on a linear low‐density polyethylene film (thickness = 30 μm) under air and nitrogen atmospheres was investigated at 60°C in mixed solvents consisting of water and an organic solvent, with xanthone as a photoinitiator. The organic solvents used were acetone, methanol, tetrahydrofuran, and dioxane. A maximum percentage of grafting occurred at a certain concentration of the organic solvent in the mixed solvent. This was observed for the systems under both air and nitrogen. The grafting reaction under air exhibited an induction period, but the rate of grafting after the period was greater than that under nitrogen. The formation of poly(ethylene peroxide)s by photoirradiation seemed to be a factor for the accelerated photografting under air. On the basis of attenuated total reflection infrared spectroscopy and scanning electron microscopy of the grafted film, the MAA‐grafted chains of the sample prepared under air tended to penetrate more deeply inside the film than those of the sample prepared under nitrogen. The resulting grafted films exhibited a pH‐responsive character: the grafted films shrank in an acidic medium but swelled in alkaline medium. This was evaluated from measurements of dimensional changes in the grafted films. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 992–998, 2003     

环氧乙烷合成乙二醇的研究进展

介绍了环氧乙烷合成乙二醇的主要生产方法，包括以壳牌、联碳化学公司以及Halcon—SD公司为代表的环氧乙烷直接水合法，环氧乙烷催化水合法和碳酸乙烯酯法，后两种乙二醇生产方法是目前国内外研究开发的热点。催化剂体系是催化水合法工艺的关键，重点介绍了国内外各主要公司对催化剂体系的研究进展及使用效果；碳酸乙烯酯法分为乙二醇和碳酸二甲酯联产法以及碳酸乙烯酯水解法，详细介绍了国内外各主要公司对该技术的研究进展，包括工艺流程、催化剂体系等方面。将3种乙二醇生产方法进行技术经济比较，结果表明，催化水合法和碳酸乙烯酯法在原料消耗和能耗方面占优势。并对我国乙二醇生产工艺技术提出建议。     

Crystalline and viscoelastic properties of branched polyethylenes synthesized using bidentate nickel (II) catalyst

In this work, five branched polyethylenes with different branching units were synthesized using bidentate nickel (II) catalyst containing -diimine ligands. For comparison, one linear polyethylene was also prepared using tridentate iron (II) catalyst containing -diimine ligand. The crystalline structure of the polyethylenes was investigated using X-ray diffraction (XRD) and polarized optical microscope. The crystalline properties were also measured by differential scanning calorimeter (DSC). Viscoelastic properties of the polyethylenes were investigated using rheometric dynamic analyzer. The DSC and XRD results showed that highly branched polyethylenes exhibit no melting points and no predominating crystalline forms, while the linear polyethylene exhibits clear orthorhombic (110) and (200) reflections on XRD pattern and a clear melting point at 118 °C. The viscoelastic properties of the branched polyethylenes were very complicated due to the combined effect of the molecular weight difference and the degree of chain branching as well as the branching structure.