Melt rheology of polypropylene containing small amounts of high molecular weight chain. I. Shear flow

Large enhancements of the melt strength of polypropylene (PP) were achieved by the introduction of high molecular weight polyethylene (PE) into PP. The viscoelastic properties of the high‐melt‐strength PP melts under shear flow were investigated. It was found that the rheological properties of the high‐melt‐strength PP were distinctly different from those of conventional PP. The elastic response at low frequencies was significantly enhanced in comparison with the conventional PP, implying a presence of a long relaxation time mode that was not revealed in conventional PP. In step‐shear measurements, the fast and slow relaxation processes that characterized the linear viscoelastic properties were observed also for nonlinear relaxation moduli. The dependence of the damping for the slow process of the high‐melt‐strength PP on shear strain was much weaker than that of the fast process. These rheological behaviors characterizing the long relaxation time mode were further enhanced with the increasing concentration of high molecular mass PE. The unusual shear rheological behaviors were discussed in view of the role of high molecular weight PE as a long relaxation time mode within PP. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2692–2704, 2001     

Grafting onto Wool. IX. Graft Copolymerization of Vinyl Monomers by Use of Vanadium Oxyacetylacetonate as Initiator

Methyl methacrylate (MMA), acrylic acid (AAc), and vinyl acetate (VAc) were graft copolymerized onto Himachali wool in an aqueous medium by using vanadium oxyacetyl acetonate as initiator. Graft copolymerization was studied at 45, 55, 65, and 75°C for various reaction periods. The percentage of grafting was determined as functions of concentration of monomers, concentration of initiator, time, and temperature. The maximum percentage of grafting with each monomer occurred at 55°. Several grafting experiments were carried out in the presence of various additives which include HNO3, DMSO, and pyridine. Nitric acid was found to promote grafting of MMA. All these additives had adverse effects on grafting of VAc and AAc. MMA, VAc, and AAc were found to differ in reactivity toward grafting and followed the order MMA > AAc > VAc.     

Accurate and Reproducible Determination of Molecular Weight Distribution of Sodium Heparin U.S.P. By HPLC

Abstract

Accurate molecular weight averages and molecular weight distributions have been determined for bulk Sodium Heparin, USP. The molecular weight averages were approximately 10,000 daltons (one dalton = one molecular weight unit) and ranged from 3,000 to 17,000 daltons in a given sample. The method uses high pressure liquid chromatography (HPLC) with 5–10 micron particle size controlled porous glass of different pore diameters (40 Å, 100 Å, and 250 Å) and simultaneous detection with a differential refractometer and ultraviolet detector (254 nm). The columns were calibrated with different molecular weight fractions of Sodium Heparin and baseline resolution obtained between 6.5K daltons differences in molecular weight. Analysis time was 25 minutes per sample and the method gave excellent reproducibility for calculated molecular weight averages in a repeated series of analysis. It was determined that the column doing most of the separation in the set was the one packed with 250 Å pore diameter size material.     

超高效液相色谱法测定青娥丸中松脂醇二葡萄糖苷的含量

建立了超高效液相色谱(UPLC)测定青娥丸中主要活性成分松脂醇二葡萄糖苷(pinoresinol diglucoside, PDG)含量的方法。样品经索氏提取后,提取物再用Waters Oasis HLB SPE固相萃取小柱进行前处理以消除杂质对PDG色谱峰的干扰。色谱条件：采用Waters Acquity C18 BEH UPLC柱(100 mm×1.0 mm, 1.7 μm)分离,以乙腈-水(使用磷酸调pH值至4.0)(9:91, v/v)为流动相,流速为0.1 mL/min,检测波长为227 nm,柱温为25 ℃,进样量为0.5 μL。在上述条件下,松脂醇二葡萄糖苷在1.40～506.00 mg/L范围内呈现良好的线性关系,相关系数r=1;低、中、高3个添加水平下的平均回收率分别为100.51%、102.37%、100.10%(n=9)。该方法准确、灵敏、重现性好,可用于青娥丸的质量控制。     

Mindless Chemistry.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

Copolymers of Bromine-Containing Monomers. 5. Terpolymerization of Acryionitrile,Styrene, and Pentabromophenyl Acrylate

The terpolymerization of acryionitrile, styrene, and pentabromophenyl acrylate in dimethylformamide solution was investigated. Experimental terpolymerization data agreed well with calculations using the Alfrey-Goldfinger equation. The relationship between monomer feed and terpolymer compositions are presented on triangular coordinate graphs, and the lines of unique and the lines of binary azeotropic composition were identified. No point of true ternary azeotropic composition was found but a “pseudoazeotropic” region was identified. The experimental results of the terpolymerization agreed well with the theoretical curves over a wide range of monomer composition up to high conversions. The influence of pentabromophenyl acrylate units on the thermal and flammability characteristics of the terpolymers are described.     

Pseudoelementverbindungen. I. Zum Koordinationsverhalten von Diphenyl-cyanamido-thiophosphinat

Pseudoelement Compounds. I. Coordination Behaviour of Diphenyl-cyanamido-thiophosphinate The synthesis of the cyanamido-thiophosphinate-nickel(II) complexes Nipy_nX₂ (X = Ph₂P(S)NCN, n = 0, 2, 4) is reported and the i.r. and u.v. spectra of these compounds are discussed. The single crystal X-ray analysis of the tetrapyridine complex shows that the anionic ligand is coordinated via the cyano-nitrogen atom. With a bond angle N(1)? C(1)? N(2) of 175.4(3)° the NCN group is nearly linear. The bond distances N(1)? C(1) and C(1)? N(2) are asymmetric and typical of NC double and triple bonds.     

Conformational behavior of dithia[n.3.3](1,3,5)cyclophanes and dithia[n.3.3](1,2,6)cyclophanes

The conformational behavior of a series of crown-fused dithia[n.3.3](1,2,6)cyclophanes (126-CPs) and dithia[n.3.3](1,3,5)cyclophanes (135-CPs) was investigated by variable-temperature ¹H and ¹³C NMR spectroscopy, X-ray crystallography and density functional theory (DFT) calculations. Single crystal X-ray structure analysis showed that two thia-bridges in 126-CPs adopted a pseudochair-pseudochair (cc) conformation and the cyclophane decks underwent a ring-tilting motion in the case of [10.3.3](1,2,6)cyclophane (1a). In contrast, the thia-bridges in 135-CPs took both cc and pseudoboat-pseudochair (bc) conformations, and the ring-tilting process was also found in [10.3.3](1,3,5)cyclophane (2a). Variable temperature ¹H NMR study revealed that there was no wobbling-motion for two thia-bridges in 126-CPs while thia-bridges in 135-CPs experienced a wobbling-process with a conformational barrier of 9.21 and 8.80 kcal mol⁻¹, respectively, for 2a and [13.3.3](1,3,5)cyclophane (2b). DFT calculations for the two cyclophanes series revealed that 126-CPs preferred a cc conformation which was consistent with the experimental observation; similarly, 135-CPs took a preferential cc conformation, agreeing with 2a having a predominant cc conformer (cc:bc ratio=70:30), but not 2b having a predominant bc conformer (cc:bc ratio=15:85) in the solid state.     

铵梯脲混合炸药中改性硝酸脲和硝酸铵含量的测定

论述了铵梯脲混合炸药中改性硝酸脲和硝酸铵组分含量的一种快速准确的化学分析测定方法。该法在研制和生产铵脲类炸药的过程中,对选择最佳配比,控制生产和质量把关等有着重要的指导作用。同时笔者对测定方法,反应原理,影响因素等作了深入的探讨与研究。     

Fluordiazadiphosphetidine, 16. Mitt.

The reaction of (CH₃NPF₃)₂ with NH₃ and primary aliphatic and aromatic amines in the molar ratio 3:2 yields (CH₄NPF₄)₂ and the monoamino substituted fluordiaza-diphosphetidines. These react with N-Trimethylsilyl-methylamine to the mixed diamino substituted compounds.With 1,4-Diazabicyclo[2.2.2]octan as HF-acceptor a second step of nucleophilic substitution with NH₃ and primary amines is possible. In the case of ammonia a by- product has been identified as the 1:1 adduct of (CH₃NPF₂NH₂)₂ with 1,4-diazabicyclo[2.2.2]octan.

Herrn Prof. Dr.O. Hromatka zum 80. Geburtstag gewidmet.     

Synthesis and flammability of copolyisophthalamides. I. With phosphorus groups in the main chain

The influence of certain phosphorus substituted (OH, OMe, Me) 3,3'-diphenylphosphine oxides on flammability and thermal stability of 1,3-phenylene isophthalamide copolymers was investigated. Introduction of the above phosphorus groups along the backbone of poly(1,3-phenylene isophthalamide) was performed in a random manner to a degree of ca. 5-15 mol %. From the limiting oxygen index (LOI) measurements on copolymers, it was found that the diphenylphosphinic acid group has the highest flame retardance efficiency with an increase of LOI 44-56%. From thermogravimetric analysis (TGA), it was found that the action of phosphorus groups is limited in the solid phase, increasing the char yield to 27-42%. This was attributed to crosslinking reactions at the stage of amide bond decomposition. © 1992 John Wiley & Sons, Inc.     

Poly(N-acylethylenimine) copolymers containing pendant pentamethyldisiloxanyl groups. I. Synthesis

10-(Pentamethyl disiloxanyl) decyl oxazoline ( Si ) was synthesized. It was copolymerized with either undecyl ( U ) or nonyl ( N ) oxazolines using methyl 4-nitrobenzenesulfonate as initiator. Two series of random poly(N-acylethylenimine) copolymers, U/Si and N/Si , were synthesized over the whole composition range of Si monomer with a total degree of polymerization of about 100. Narrow molecular weight distributions were obtained. At a monomer to initator ratio of about 1060, the final degree of polymerization was 374 with a polydispersity index of 1.93. This shows the effect of chain transfer in this system.     

Poly(ethylene terephthalate) copolymers containing nitroterephthalic units. III. Methanolytic degradation

The methanolytic degradation of poly(ethylene terephthalate) (PET) copolymers containing nitroterephthalic units was investigated. Random poly(ethylene terephthalate‐co‐nitroterephthalate) copolyesters (PETNT) containing 15 and 30 mol % nitrated units were prepared from ethylene glycol and a mixture of dimethyl terephthalate and dimethyl nitroterephthalate. A detailed study of the influence of the nitro group on the methanolytic degradation rate of the nitrated bis(2‐hydroxyethyl) nitroterephthalate (BHENT) model compound in comparison with the nonnitrated bis(2‐hydroxyethyl) terephthalate (BHET) model compound was carried out. The kinetics of the methanolysis of BHENT and BHET were evaluated with high‐performance liquid chromatography and ¹H NMR spectroscopy. BHENT appeared to be much more reactive than BHET. The methanolytic degradation of PET and PETNT copolyesters at 80 °C was followed by changes in the weight and viscosity, gel permeation chromatography, differential scanning calorimetry, scanning electron microscopy, and ¹H and ¹³C NMR spectroscopy. The copolyesters degraded faster than PET, and the degradation increased with the content of nitrated units and occurred preferentially by cleavage of the ester groups placed at the meta position of the nitro group in the nitrated units. For both PET and PETNT copolyesters, an increase in crystallinity accompanied methanolysis. A surface degradation mechanism entailing solubilization of the fragmented polymer and consequent loss of mass was found to operate in the methanolysis of the copolyesters. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2276–2285, 2002     

Transient and athermal effects in the crystallization of polymers. I. Isothermal crystallization

The isothermal crystallization of poly(propylene) and poly(ethylene terephthalate) was investigated with differential scanning calorimetry and optical microscopy. It was found that the induction time depends on the cooling rate to a constant temperature. The isothermal crystallization of the investigated polymers is a complex process and cannot be adequately described by the simple Avrami equation with time‐independent parameters. The results indicate that crystallization is composed of several nucleation mechanisms. The homogeneous nucleation occurring from thermal fluctuations is preceded by the nucleation on not completely melted crystalline residues that can become stable by an athermal mechanism as well as nucleation on heterogeneities. The nucleation rate depends on time, with the maximum shortly after the start of crystallization attributed to nucleation on crystalline residues (possible athermal nucleation) and on heterogeneities. However, the spherulitic growth rate and the exponent n do not change with the time of crystallization. The time dependence of the crystallization rate corresponds to the changes in the nucleation rate with time. The steady‐state crystallization rate in thermal nucleation is lower than the rate determined in a classical way from the half‐time of crystallization. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1835–1849, 2002     

Transition metal complexes with Girard reagent-based ligands. Part IV. Synthesis and characterization of pyridoxilidene Girard-T hydrazone complexes. Crystal structure of the copper(II) complex

Abstract  The monoligand complexes of the formula M(HPLGT)(NCS)₂ (M = Cu(II), Zn(II)) in which the ligand tridentate ONO pyridoxilidene Girard-T hydrazone, [H₃PLGT]Cl₂ · 2H₂O, was coordinated in neutral doubly deprotonated form were synthesized. Also, the first complexes with the ligand coordinated in triply deprotonated monoanionic form of the formula [Cu(PLGT)N₃] and [Co(PLGT)(NO₂)₂NH₃] · 3H₂O are reported. The single crystal X-ray analysis of [Cu(HPLGT)(NCS)₂] showed that Cu(II) is placed in a square-pyramidal surrounding consisting of one tridentate Schiff base and one NCS group in the basal plane and the other NCS group in the apical position. Intermolecular hydrogen bonds leading to centrosymmetrical dimerization of these complexes were discussed. In the reaction of Girard-T and Hacac in the presence of CuCl₂, a mixture of single crystal complexes of the composition [Cu(3,5-Me₂pz)₂Cl₂]₂ and [Cu(acac)₂] · 2[Cu(3,5-Me₂pz)₂Cl₂] was obtained and X-ray analysis of the latter one was reported. Index abstract  Crystal structure of the Cu(II) complex with pyridoxilidene Girard-T hydrazone was analyzed. Additional two Cu(II) complexes obtained by the reaction of Girard-T reagent and Hacac in the presence of CuCl₂ were also studied by single crystal X-ray analysis.      

Pyridine-Type Complexes of Transition-Metal Halides XIV. Part III. Complexes with 2,4-, 2,6-, 3,4- and 3,5-lutidines

Compounds obtained by a solid–gas phase reactions between copper(II) chloride and bromide and 2,4-, 2,6- 3,4- and 3,5-lutidines were studied using thermogravimetry, far-infrared, electronic spectroscopy and X-ray diffraction. The results were compared with the corresponding data for the similar compounds with methylpyridines and 2,4,6-collidine. A special attention was paid to the host-guest phenomenon, a new structural feature of transition-metal halide complexes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Beiträge zur Chemie des Phosphors. 235. Zur Darstellung größerer Mengen von Diphosphan(4) im Laboratorium

Contributions to the Chemistry of Phosphorus. 235. On the Preparation of Larger Amounts of Diphosphane(4) in the Laboratory The preparation of several hundred grammes of diphosphane(4) by hydrolysis of calcium phosphide in a semicontinuous process as well as the handling of larger amounts of this compound are reported. In comparison with earlier results [12], the yield has been raised by 37 percent with simultaneous increase of the accessible total amount. The white solid which is formed in the preparation and purification of diphosphane(4) is not, as was believed in earlier work [25, 8], triphosphane(5) or another, novel phosphorus hydride but is rather a clathrate compound of diphosphane(4) or the phosphanes P_nH_n+2 (n = 2–4) and water, respectively.     

Fluordiazadiphosphetidine. 22. Mitt. Reaktionen von 2,2,2,4,4,4-Hexafluoro-1,3-dimethyl-1,3,2λ5,4λ5-diazadiphosphetidin mit silylierten Aminosäuren

Summary The interaction of silylated amino acids with hexafluorodiazadiphosphetidine was studied. With trimethlsilyl amino acid esters the substitution of one fluorine atom was accomplished, whereas with bis-silylated amino acids polymeric products were obtained, which could not be characterized.

     

Synthesis and flammability of copoly(isophthalamide)s. II. With pendant phosphorus groups

A series of copoly(isophthalamide)s containing pendant phosphorus, dialkoxyphosphinylphenylene, diphenylphosphinylphenylene, and diphenylphosphinylamino groups were prepared. The introduction of phosphorus groups was performed to a degree of ca. 5–17 mol %. From the limiting oxygen index (LOI) measurements, it was found that the LOI of P-substituted polyamides increased by ca. 14–40%. From TG and DTG analysis the maximum rate and the percentage of mass loss of the decomposition stages were evaluated. From these measurements the mode of action of phosphorus groups in the solid or gas phase was assessed. In the solid phase, due to crosslinking reactions, a reduction of the maximum rate and the percentage of mass loss in the decomposition stage of main chain amide bonds was observed. In this case the increase of the char yield at 700°C of the P-substituted polyamides was in the range of 21–36%. © 1993 John Wiley & Sons, Inc.     

Poly(ethylene terephthalate) copolymers containing 5‐nitroisophthalic units. III. Methanolytic degradation

The methanolysis of poly(ethylene terephthalate) (PET) copolymers containing 5‐nitroisophthalic units was investigated. Random copolyesters containing 10 and 30 mol % of such units were prepared via a two‐step melt copolycondensation of bis(2‐hydroxyethyl) terephthalate (BHET) and bis(2‐hydroxyethyl) 5‐nitroisophthalate (BHENI) in the presence of tetrabutyl titanate as a catalyst. First, the susceptibility of these two comonomers toward methanolysis was evaluated, and their reaction rates were estimated with high‐performance liquid chromatography. BHENI appeared to be much more reactive than both BHET and bis(2‐hydroxyethyl) isophthalate. The methanolysis of PET and the copolyesters was carried out at 100 °C, and the degradation process was followed by changes in the weight and viscosity, gel permeation chromatography, differential scanning calorimetry, and ¹H and ¹³C NMR spectroscopy. The copolyesters degraded faster than PET, and the rate of degradation increased with the content of nitrated units. The products resulting from methanolysis were concluded to be dimethyl terephthalate, dimethyl 5‐nitroisophthalate, ethylene glycol, and small, soluble oligomers. For both PET and the copolyesters, an increase in crystallinity was observed during the degradation process, indicating that methanolysis preferentially occurred in the amorphous phase. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 76–87, 2002