Showing papers by "DSM published in 1989"

Method of forming a three-dimensional object by stereolithography and composition therefore

Abstract: A stereolithographic method which employs an ultraviolet-curable liquid composition adapted to cure rapidly to a lightly cross-linked solvent-swellable three-dimensional complexly-shaped polymeric thin-walled element constituted by heat-softenable solid polymer upon exposure to ultraviolet dosage in the range of about 0.1 to about 10 Joules per square centimeter and which possesses reduced distortion comprises, from 20 to 80 weight percent, of a resinous polyacrylate or polymethacrylate dissolved in a combination of 10 to 45 weight percent of a liquid polyacrylate or polymethacrylate, which is preferably trifunctional, and 10 to 45 weight percent of liquid N-vinyl monomer, preferably N-vinyl pyrrolidone. Thus, the weight ratio of polyacrylate: polymethacrylate: N-vinyl monomer is about 1:2:2 to about 8:1:1. One of the foregoing polyacrylates or polymethacrylates is a polyacrylate and the other is a polymethacrylate so that good cure speed is accompanied by good distortion resistance. In the method, a reservoir of the liquid composition is established and its exposed surface is irradiated to solidify the surface and build up a thin-walled element which is removed from the reservoir, drained of liquid adhering thereto and cured.

Process for the processing of a thermoplastic polycondensation polymer

Abstract: The invention relates to a process for the processing of a thermoplastic polycondensation polymer by supplying the polymer in finely distributed form to a first vented extruder in which the polymer is devolatilized at a temperature below its melting temperature. The polymer is then placed in a second extruder where the polymer is transported below the melting temperature of the polymer over a first length of the screw from the inlet of the extruder, with constant evacuation of volatile components by means of a vacuum exhausting device at a vacuum of less than 10 mbar and the polymer is compressed and melted over a second length of the screw and then leaves the extruder as an end product of a semimanufacture.

The effect of crown ethers on enzyme-catalysed reactions in organic solvents

Abstract: Crown ethers considerably enhance the rate of the α-chymotrypsin-catalysed transesterification of N-acetyl-L-phenylalanine ethyl ester (N-Ac-L-Phe-OEt) with propan-1-ol in n-octane; with subtilisin the effect is somewhat less pronounced.

Gene replacement as a tool for the construction of aspergillus strains

Abstract: Transformation of Aspergillus , particularly A. niger is demonstrated. Integration at the glucoamylase locus is exemplified. A chymosin expression construct is inserted at a locus, where the chymosin may be joined to a signal sequence for efficient secretion.

Melting behaviour of gelspun/drawn polyolefins

Abstract: The melting behaviour of gelspun/drawn UHMW-PE and UHMW-PP fibres was investigated. Unconstrained UHMW-PE and UHMW-PP fibres melt at 142°C and 170°C, respectively. Upon constraining, by holding the fibres at a fixed length or by embedding the fibres in a matrix, an increase in the melting temperature of both fibres is observed. In the case of UHMW-PE fibres a solid-solid phase transition in polyethylene at 155°C from the orthorombic to the hexagonal crystal structure occurs. Above 155°C, the fibres can not sustain any load. This solid-solid phase transition at 155°C sets an upper limit to both the maximum curing and continuous use temperature of PE-fibre reinforced composites. In gelspun/drawn UHMW-PP, such a detrimental solid-solid phase transition is absent, and therefore the increase in melting temperature can be utilized effectively. For example, heating of UHMW-PP fibres for 30 minutes at 200°C does hardly affect the room temperature Young's modulus and tensile strength if the fibre is constrained during heating.

Viscoelastic properties of UHMW‐PE fibers in simple elongation

Abstract: Stress relaxation after a simple elongational step strain, creep under a constant simple elongational stress, and stress build-up under a constant Hencky strain rate have been measured for ultrahigh-molecular-weight polyethylene (UHMW-PE) fibers. The data from the various experiments are consistent with the Boltzman superposition principle in the experimental region of small strains or short times. This leads to a simple constitutive equation in which temperature can be incorporated via time-temperature superposition. The measured power-law relaxation of the UHMW-PE fiber leads to analytical expressions for the dynamic quantities in simple elongation. The constitutive equation is the one-dimensional equivalent of the gel equation derived for cross-linking gels at the gel point. The similarity between the rheological behavior of fibers and cross-linking gels at the transition point might lead to an enhanced understanding of the molecular processes occurring during deformation.

Taxonomy of Bacillus

Abstract: A century ago, when a young scientist detected that a bacterium which Pasteur had thought to be a coccus was in fact a short rod, Pasteur’s comment was, “I wish I could convey to you how little that information excites me” (Duclaux, 1896) Obviously, Pasteur was interested in microorganisms mainly for what they do rather than what they are Whereas this remains a legitimate interest today, early bacteriologists felt that, with the increasing diversity of organisms isolated, there was a need to arrange bacteria distinctly The easiest way to do this was to put them into groups with common properties, to study the relationships of such groups and their role in nature, and to develop methods that would enable scientists to identify new isolates with already known groups

Phenylglycidate stereoisomers, conversion products thereof with e.g. 2-nitrothiophenol and preparation of diltiazem

Abstract: The stereoisomerically pure esters of (2R,3S)-3-(4-hydroxy or 4-alkoxyphenyl)glycidic acid, which is a starting compound for the preparation of diltiazem, are prepared by stereospecific enzymatic hydrolysis. By using such an ester, it is possible to economically prepare the (2S,3S) isomer of diltiazem to the exclusion of other stereoisomers.

Copolyamides of nylon‐4,6 and nylon‐4,T

Abstract: Copolyamides of nylon-4,6 and nylon-4,T were prepared by a two-step method: (1) a prepolymerization in an autoclave (40 min at 210°C) and (2) a postcondensation in the solid state (4 h, 260°C). On these materials was studied the melting behavior with DSC, the crystalline structure with WAXS, the water absorption, and the mechanical properties with a torsion pendulum. In these copolyamides the order was found to remain high, but the crystalline structures of -4,6 and -4,T were not isomorphous. The torsion moduli increased with -4,T content both at RT and at 140°C.

Screw design in injection molding

Abstract: The performance of screws of advanced design in injection molding has been investigated with respect to four different objectives: (1) improvement of distributive mixing; (2) improvement of dispersive mixing; (3) increase of plasticating capacity; and (4) reduction of inhomogeneity of melt temperature. The screws used are three zone screws with different compression ratios, screws with pineapple or Maddock/Egan mixing elements, with one or two channel barrier sections, with static mixers mounted in the valve or in the nozzle, or with combinations of these different elements. The best mixing quality is obtained with multi-channel Maddock sections. The highest plasticating capacity and, consequently, the shortest cycle times are achieved with the barrier screws. Temperature measurements show that these screws improve melt homogeneity considerably with a relatively small loss of plasticating time. In all cases, increasing the back pressure gives inferior results compared with improvement of the screw design.

Methanolacinia gen. nov., incorporating methanomicrobium paynteri as methanolacinia paynteri comb. nov

Abstract: On the basis of an extended investigation of morphological, biochemical and physiological properties and its phylogenetic affiliation it is proposed to place Methanomicrobium paynteri, validly published in 1984 within a new genus, Methanolacinia gen. nov. as Methanolacinia paynteri comb. nov.

The removal of carbon or carbon residues from ceramic powders or greenware with ammonia

Abstract: In this paper it is shown that carbon or carbon residue can be removed from ceramic powder, granulate or greenware with NH 3 , yielding HCN. Dissociation of NH 3 on the surface of carbon or carbon residue and matrix material occurs simultaneously. If NH 3 is used instead of N 2 in the carbothermal synthesis of nitrides it is necessary to allow for both the dissociation of NH 3 and the formation of HCN.

Composition containing uv curable unsaturated monomers and/or oligomers, a photoinitiator and colloidal silica with an oragnosilane compound, and the application of this composition in coatings

Abstract: The invention relates to a composition containing UV curable unsaturated monomers and/or oligomers, a photoinitiator and colloidal silica with an organosilane compound, a polyalkoxysilane being used as organosilane compound and the composition containing an acid catalyst.

Thermal expansivity of particulate composites: Interlayer versus molecular model

Abstract: We continue the comparison of the results of an interlayer model, based on the theory of elastic continua, and a molecular model, derived from a theory of mixtures, previously presented in terms of bulk moduli K. We now derive expressions for the dependence of the thermal expansivityαc on the volume fractionφf of the filler, at low and elevated values ofφf. Correspondencies between the characteristic parameters, viz. adhesion and repulsion ratios on the one hand, and interlayer content and thermal properties of matrix, filler, and layer, on the other, are examined. Since in the molecular theory bothα andK are derived from an equation of state, the identical set of parameters determines both functions and suggests correlations between them.

Oxygen-induced next-nearest neighbour effects on the C1s-levels in polymer XPS-spectra

Abstract: This letter reports the results of ab initio quantum chemical calculations on the C1s core levels of model systems for a number of oxygen containing polymers. Conformational effects were studied. SCF calculations have been carried out with STO-3G and 4-31G basis sets, and Koopmans' theorem was applied to obtain the core-level binding energies. To evaluate the performance of the procedure ΔSCF calculations were carried out on polyacrylic acid. The existence of oxygen-induced secondary substituent effects in the XPS-(ESCA-)spectra is discussed. A comparison with semi-empirical CNDO/2 results from Clark and Thomas has been made.

Changes of mesophase structure of BRIJ 96/water mixtures on addition of liquid paraffin

Abstract: The influence of the addition of liquid paraffin (LP) on the structure of the lamellar (Lα) and hexagonal (H1) mesophases formed in mixtures of water (W) and BRIJ 96 (B) was studied. Mesophases were identified using polarization microscopy and small angle x-ray diffraction (SAXD). Repeat spacings were also determined with SAXD. Depending on theW/B ratio, addtion ofLP toLα gives a large, almost linear one-dimensional swelling or an initial swelling followed by a gradual transition to H1.Lα with a highLP-content gives a diffraction pattern showing only the first order diffraction maximum, possibly a result of undulations of the layers. The lamellar structure, however, was confirmed using freeze fracture electron microscopy (FFEM). Addition ofLP to H1 gives an initial swelling followed by a transition to a transparent, highly viscous, isotropic phase, called the gel-phase (G). The diffraction pattern obtained fromG yields little information on its structure. A large swelling ofG withLP was observed. From the degree of swelling as a function of hydrocarbon content it was inferred that this phase consists of spherical aggregates forming a close-packed structure. Using FFEM, textures were visualized resembling those obtained from the isotropic mesophase (I1) in water-surfactant mixtures. Finally, geometrical factors are discussed that may play a role in the formation of the gel-phase.

Interfacial role and properties in model composites: Fracture surfaces by scanning electron microscopy

Abstract: The fracture surfaces of glass sphere-filled polyethylene model composites with varying degrees of interfacial modification were examined by scanning electron microscopy. The micrographs give a qualitative view of the bonding process and the nature of the region of modified matrix surrounding the glass spheres. Adhesive failure is seen for the unmodified composites, and also for the composites with near monolayer modification. At higher degrees of interfacial modification a layer of bound modified matrix is formed around the glass surface and the failure is cohesive. The micrographs demonstrate that the properties of the modified interfacial layer are dependent on the volume fraction of glass. The micrographs also show that the mechanism of bonding the matrix to the glass surface is through the thermally activated azide moeity.

A method of improving the properties of dough and the quality of bread

Abstract: The invention relates to a method of improving the properties of dough and the quality of bread by adding to the dough, dough ingredients, ingredient mixture or dough additives or additive mixture an enzyme preparation comprising hemicellulose and/or cellulose degrading enzymes and glucose oxidase, or sulphydryl oxidase and glucose oxidase, the enzyme preparation being preferably used in combination with lecithin. The enzyme preparation of the invention has an advantageous effect on the processability of the dough and the properties of the final bakery product. The combination of the enzyme preparation of the invention and lecithin can advantageously replace bromate conventionally used as a baking additive.

Triboelectrically processable powder coating.

Abstract: The invention relates to a triboelectrically processable powder coating based on a polyester-containing binding agent and a nitrogen-containing additive. The nitrogen-containing additive is a sterically hindered tertiary amine or aminoalcohol.

Thermal expansivity and bulk modulus of polymer composites: Experiment versus theory

Abstract: Correlations between the thermal expansivity, αc, and the compressibility, Kc, of particulate-filled polymer melts are explored in terms of two different theories and in connection with experiments. Both theories employed [an interlayer approach based on micromechanics (IM), and a molecular one starting from the statistical thermodynamics of mixtures (MM)] account for the effect of filler-matrix interactions, viewed as a system-dependent parameter. The concentration dependences of αc and Kc calculated using either IM or MM agree well with experiments on polyurethane and epoxy composites, and it is possible to predict αc based on Kc experimentation. In MM this is always true, but in IM it depends on a knowledge of relations between α and K of the constituents. This point remains to be explored further.

A model for the effect of physical ageing on the stress relaxation behavior of high density polyethylene

Abstract: The stress relaxation behavior of high density polyethylene (HDPE) can be affected by ageing processes; e.g., with increasing storage time at a low temperature following a quench from a high temperature (close to the melting point) the relaxation curves change shape. More specifically, the stress level approached after very long loading times in a stress relaxation experiment increases with the ageing time. Here this stress level is denoted “the internal stress”σ i. Struik has pointed out that physical ageing may also occur in semicrystalline polymers like HDPE. The physical ageing should then be associated with that part of the amorphous phase which is closest to the surfaces of the crystallites. This part of the amorphous phase of HDPE can be assumed to have a restricted mobility at room temperature and may have a partially “glassy” character. In this paper a model for explaining the increase inσ i for HDPE with increasing ageing time is proposed and discussed. It is based on the separation of the amorphous phase into two parts as suggested by Struik. The glassy part of the amorphous phase ages in a way similar to that of an entirely amorphous polymer quenched to a temperature below its glass transition, while the more rubbery phase is assumed not to undergo any physical ageing.