热致液晶共聚酯的熔融行为及结晶结构研究

采用ＤＳＣ及ＷＡＸＤ手段对含对羟基苯甲酸热致液晶共聚酯的相变行为及结晶结构进行了初步研究。结果表明，聚合物中存在两种同属于正交晶系的不同堆积形态结晶结构，在相变上表现为双重熔融峰。     

Synthesis and unusual properties of novel alkylbenzene sulfonate gemini surfactants

Seven new dialkyldibenzene disulfonate gemini surfactants have been synthesised. The physico-chemical properties such as their surface tensions, krafft temperatures and melting temperatures have been measured. It was found that the anionic gemini surfactants showed some aberrant properties. The results determined by drop-volume method indicated that surfactants Id, Ie at 25 °C and IIb at 50 °C showed no cmc and lowered surface tension of water hardly despite their seemingly favorable amphiphilic components. However, the three surfactants showed a sharp cmc and good surface activity with the increment of temperature. Surfactant Ie with two longer chains had a higher cmc than that for shorter chain surfactant Id. Furthermore, for this class of anionic gemini surfactants, the spacer carbon number had more important effects than the alkyl chain carbon number on their krafft temperatures and melting temperatures.     

The Na2O-SrO-B2O3 diagram in the B-rich part and the crystal structure of NaSrB5O9

The subsolidus phase relations in the B-rich part of the ternary system, Na₂O-SrO-B₂O₃, are investigated by the powder X-ray diffraction method. Four ternary compounds: NaSrBO₃, NaSr₄B₃O₉, Na₃SrB₅O₁₀ and NaSrB₅O₉ were found in it, the two lasts are new. NaSrB₅O₉ crystallizes in the monoclinic space group P2₁/c, with the lattice parameters a=6.4963(1) Å, b=13.9703(2) Å, c=8.0515(1) Å, β=106.900(1)°. Na₃SrB₅O₉ is also monoclinic, space group C2, a=7.290(1) Å, b=13.442(2) Å, c=9.792(1) Å, β=109.60(1). NaSrB₅O₉ is isostructural with another pentaborate NaCaB₅O₉, and its structure was refined by Rietveld method based on the structural model of NaCaB₅O₉. The fundamental building units are [B₅O₉]³⁻ anionic groups, forming complex thick anionic sheets, extending parallel to the ac plane. The Na and Sr atoms are all eight-coordinated with O atoms, forming trigonal dodecahedra. The [NaO₈] polyhedra are distributed between the B-O sheets, while the [SrO₈] polyhedra located in the sheets and connect with each other by edges to form infinite chains along the c-axis.     

The effect of compatibilizers on the crystallisation, melting and polymorphic composition of β-nucleated isotactic polypropylene and polyamide 6 blends

Non-compatibilized and compatibilized blends of isotactic polypropylene (iPP) and polyamide 6 (iPP/PA6) as well as their β-nucleated versions were prepared using maleic anhydride functionalized iPP (MAPP) with different anhydride contents as compatibilizer. Ca-suberate, a highly efficient and selective β-nucleating agent was added to the blends in order to promote the formation of the β-modification of iPP. The melting and crystallisation characteristics, as well as the polymorphic composition of the blends were studied by differential scanning calorimetry (DSC). The supermolecular and phase structure of the blends were studied by polarised light microscopy (PLM). iPP and PA6 form blends with heterogeneous phase structure; the PA6 component is dispersed in the iPP matrix in the concentration range studied. The compatibilizer promotes the dispersion of PA6 resulting in smaller particles than without MAPP. In the non-compatibilized β-nucleated blends, an iPP matrix consisting mainly of the α-modification was formed already at low PA6 content. On the contrary, predominantly β-iPP matrix developed in the presence of MAPP compatibilizers. The formation of α-iPP matrix in the absence of compatibilizer is related to the selective encapsulation of the nucleating agent in the polar PA6 phase. The influence of the blending technique on the polymorphic composition of the matrix supports the hypothesis of selective encapsulation. Compatibilizers, besides their traditional benefits assist the distribution of the β-nucleating agent between both phases of the blends and promote the formation of a matrix rich in β-iPP. In the presence of β-nucleating agent MAPP with low anhydride content and blends of iPP containing maleated polypropylene crystallise predominantly in the β-form.     

Studies of comonomer distributions and molecular segregations in metallocene-prepared polyethylenes by DSC

This paper is devoted to the study of crystallization and melting of two metallocene polyethylenes (m-PEs). A metallocene linear low density polyethylene (m-LLDPE) and a metallocene very low density polyethylene (m-VLDPE) were used consisting of 3.3 mol% butyl and 6 mol% ethyl branches, respectively. Several melt endotherms after stepwise crystallization revealed that the two m-PEs consisted of molecular fractions with different molecular weight and branch distribution. More segregation was observed for the m-VLDPE comparing with m-LLDPE. Using the relationships proposed by Hosoda, the short chain branching distribution (SCBD) and the average methylene groups in the lamella thickness were also calculated for the two polymers. These values were compared with the values obtained from theory of rubber elasticity. There was a very good correlation between the data.     

Melt crystallization of zinc alkali phosphate glasses

Melt crystallization of two zinc alkali phosphate glasses was studied with X-ray diffraction (XRD) experiments to accelerate efforts to melt process these glasses with organic polymers. The inorganic glasses differed markedly in chemical durability (water sensitivity) and crystallization rates. They were studied at room temperature prior to and after melt processing with XRD experiments and in situ at melt temperatures without flow in a novel differential scanning calorimeter/XRD apparatus. The glasses were found to be amorphous at room temperature and semi-crystalline above their glass-transition temperatures. Higher temperatures and shear (mixing) rates increased the crystallization rate of the glasses. The non-durable (water-sensitive) glass was observed to contain significant levels of crystalline matter after melt processing at 400°C. This process-induced crystallization of the glasses must be controlled, possibly during processing and/or glass formulation, otherwise it may lead to formation of unwanted phase-separated defects in the glass. If high levels of the crystalline matter are present during melt processing, they may lead to irreversible plugging of the processing equipment.     

The Melting Point Alternation in the Short-Chain n-Alkanes: Single-Crystal X-Ray Analyses of Propane at 30 K and of n-Butane to n-Nonane at 90 K

A less dense packing is observed in the odd-numbered n-alkanes compared to the even-numbered members, which consequently lowers melting temperatures. The reason for this is that the even-numbered n-alkanes have optimal intermolecular interactions at both ends (see the picture on the left), while the odd-numbered ones possess these only at one end—at the other end the intermolecular distances are longer (right)     

Temperature modulated dynamic mechanical analysis

Temperature modulated dynamic mechanical analysis (TMDMA) was performed in the same way as temperature modulated DSC (TMDSC) measurements. Temperature modulation with amplitude 0.5 K and period 20 min was realised by a series of linear heating and cooling cycles (saw-tooth modulation). As in TMDSC TMDMA allows for the investigation of reversible and non-reversible phenomena in the melting and crystallisation region of polymers. The advantage of TMDMA compared to TMDSC is the high sensitivity for small and slow changes in crystallinity, e.g. during re-crystallisation. The combination of TMDMA and TMDSC yields new information about local processes at the surface of polymer crystallites. It is shown that during and after isothermal crystallisation the surface of the individual crystallites is in equilibrium with the surrounding melt.     

矿石中多元素的XRF分析

采用熔融法制样,ＸＲＦ分析方法,测定矿石中的多种元素,此法克服了基体效应,方便可靠。     

Melting and thermal decomposition of [Ni(H2O)6](NO3)2

The two-stage melting process and the thermal decomposition of [Ni(H₂O)₆](NO₃)₂ was studied by DSC, DTA and TG. The first melting point at 328 K is connected with the small and the second melting point at 362 K with the large enthalpy and entropy changes. The thermal dehydration process starts just above ca. 315 K and continues up to ca. 500 K. It consists of three well-separated stages, but the sample mass loss at each stage depends on the experimental regime. However, irrespective of the chosen regime, the total of registered mass losses in stage one and two amounts to three H₂O molecules per one [Ni(H₂O)₆](NO₃)₂ molecule. The remaining three H₂O molecules are gradually freed in the temperature range of 440–500 K in the third stage of the dehydration. Above 580 K, anhydrous Ni(NO₃)₂ decomposes into NO and NiO. The gaseous products were identified by quadrupole mass spectrometer (QMS), and the solid product was identified by X-ray diffraction (XRD) analysis.