Showing papers by "DSM published in 1982"

Generalization of Kramers-Kronig transforms and some approximations of relations between viscoelastic quantities

Abstract: On the basis of some very plausible assumptions about the response of physical systems to stimuli, such as Boltzmann's superposition principle and the causality principle, Spence showed that the following characteristics obtain for the modulus and compliance functions: (i) They are analytic in the lower half of the complex frequency plane, (ii) they are limited if the frequency tends to infinity, and (iii) the real and imaginary parts are even and odd functions, respectively, of the frequencyω. It can generally be demonstrated that the real and imaginary parts of every function satisfying these three requirements and (iv) without singularities on the real frequency axis, are interrelated by Kramers-Kronig transforms. Similar relations hold between the logarithm of the modulus and the argument of the function.

Tensile strength of highly oriented polyethylene. II. Effect of molecular weight distribution

Abstract: The tensile strength of oriented polyethylene filaments is discussed in relation to molecular weight. Short-term tensile properties at room temperature were obtained in our laboratory and from the literature for polymer samples covering the molecular weight (Mw) range from 54 × 103 to 4 × 106, and polydispersities ranging from 1.1 to 15.6, oriented by solid-state extrusion, melt spinning/drawing, solution spinning/drawing, and “surface growth.” It was found that both the molecular weight and its distribution markedly affected tensile strength. The breaking stress σ of highly oriented fibers varied with molecular weight roughly as σ ∝, M0.4, at constant Mw/Mn over the entire range studied. Reduction of polydispersity from 8 to 1.1 by an increase of Mn with Mw approximately constant at 105 increased tensile strength of oriented polyethylene filaments by a factor of nearly 2.

Acute inhalation toxicity study of ammonia in rats with variable exposure periods

Abstract: The acute inhalation toxicity of ammonia was examined in rats using various exposure concentrations and exposure periods. Groups of male and female rats were exposed to dynamic atmospheres containing different concentrations of ammonia for 10, 20, 40 or 60 min. The aim of the study was to establish the relationship between exposure concentration and exposure period and mortality. The correlation between exposure concentration (c), exposure period (t) and mortality rate, expressed in probits was found to be Probit = 2.30 1n [c(2.02) x t] - 47.8. The following LC50 values for ammonia were calculated: 10min LC50 : 28,130 mg/m3 air (40,300 ppm); 20 min LC50 : 19,960 mg/m3 (28,595 ppm); 40 min LC50 : 14,170 mg/m3 air (20,300 ppm); 60 min LC50 : 11,590 mg/m3 air (16,600 ppm). Chemicals/CAS: ammonia, 14798-03-9, 51847-23-5, 7664-41-7; Ammonia, 7664-41-7

Mean-Field Lattice-Gas Description of the System CO2/H2O

Abstract: The mean-field lattice-gas model in the present form has proven to be well able to describe nearly quantitatively fluid phase behaviour of non-polar and polar pure components and mixtures over a large temperature and pressure range. In our version of the model it is assumed that: all lattice sites have the same volume, independent of temperature and pressure, and that every kind of lattice site has a characteristic interacting surface area. The combinatory entropy of the system is corrected with an empirical parameter. For mixtures the same procedure cart be followed and a description of fluid phase behaviour, based upon the parameters of the pure components and two binary interaction parameters, appear to come out quite reasonably. The systems CO2 H2O and mixtures thereof are most commonly used in supercritical extraction. It is shown here that the lattice-gas model can quite well deal with these systems. Values of the lattice-gas parameters have been derived in the outlined manner and predict t...

Some aspects of linear and nonlinear viscoelastic behaviour of polymer melts in shear

Abstract: In linear viscoelastic investigations the frequency dependence of the phase shift between stress and strain appears to be very characteristic of the molecular structure of the material. This function is also a good approximation of the slope of the double logarithmic plot of the absolute value of the shear modulus G d vs. the angular frequency ω. The product (G d /π) sin 2δ comes very close to the relaxation spectrum H(τ), with τ = 1/ω, in all physical states of the material.

Polymer composition based on a polycarbonate and a graft copolymer

Abstract: Disclosed is a polymer composition based on a polycarbonate and a graft copolymer of a vinyl aromatic compound and an unsaturated nitrile compound on a rubber-like polymer. Good flow properties are achieved by a composition consisting essentially of: A. at least one graft copolymer obtained by polymerizing 40-80 parts by weight of a monomer mixture, which mixture consists of: (1) 20-40 weight % of acrylonitrile, and (2) 60-80 weight % of styrene, in the presence of 10-25 parts by weight of a hydrocarbon rubber, B. at least one graft copolymer obtained by polymerizing 75-90 parts by weight of a monomer mixture, which mixture consists of: (1) 20-40 weight % of acrylonitrile, and (2) 60-80 weight % of styrene, in the presence of 10-25 parts by weight of a hydrocarbon rubber, C. a copolymer obtained by polymerizing 20-40 parts by weight of acrylonitrile with 60-80 parts by weight of styrene, and D. at least one polycarbonate, wherein based on the weight of the composition, the total rubber content is from about 5 to about 30 weight % and the difference in rubber content between components A and B is at least 5 weight %. Each monomer mixture used to formulate graft copolymer components A and B may additionally, based on the weight of the mixture, contain up to 20 weight % of at least one additional monomer.

Isotope effect in polymer compatibility

Abstract: The deuterium isotope effect on liquid-liquid phase behaviour in polymer blends was investigated with Gordon's Pulse Induced Critical Scattering Method. Spinodals in mixtures of polystyrene and polybutadiene were found to be sensitive to replacement of H by D in the polybutadiene. The results indicate a difference in heat of mixing between PS/PBH and PS/PBD-6 as well as an influence on the entropy of mixing.

Crosslinking of unsaturated polyester resins by combinations of vinyl esters and methacrylates

Abstract: The replacement of styrene by other crosslinking monomers in unsaturated polyester resins has been investigated because of the possible toxicity of this monomer and the strong smoke evolution of burning polyester materials. A theoretical study has been carried out to provide criteria for the applicability of classes of monomers in polyester curing. From this study it appeared that vinyl esters, vinyl ethers, N-vinyl lactams, and styrenes are suitable, whereas acrylic and methacrylic esters and allylic or olefinic compounds are not. Combinations of vinyl esters and (meth)acrylic esters of polyols should generate IPN-like structures. Polyesters cured by this combination of monomers gave materials with increased stiffness and strength relative to those obtained with the separate monomers and on the same level as styrene-cured polyesters.

Process for the production of polymer filaments having high tensile strength and modulus

Abstract: The invention relates to a process for the production of polymer filaments by spinning a solution of a polymer, having a weight-average molecular weight M w higher than 4.10 5 kg/kmole with at least 80 % by weight of solvent at a temperature above the gel point of that solution, cooling the spun product to below the gel point and stretching the obtained filament to a filament having a tensile strength of more than 1,5 GPa at room temperature. The polymer has preferably a weight/number-average molecular weight ratio Mw/Mn lower than 5. During stretching the filament can be twisted around its axis.

Combinations of Low Formaldehyde-Aminoplast Glues and PMDI

Abstract: Basic research on the formaldehyde emission from aminoplast-bonded particleboard has led to the conclusion that F-emission is essentially governed by the gross molar ratio of formaldehyde to NH2 equivalents in the material. From this starting point a new approach was chosen in the development of a glue for low-F-emission boards: such a level of the effective F/NH2 molar ratio is chosen for the UF or UMF glue that F-emission standards can be met, following which methods or additives are developed to bring mechanical quality back to an acceptable level. It is shown that addition of approx. 10% of polymeric isocyanate (PMDI) to UMF glue can meet our purpose on a commercially acceptable basis. The performance of the system, using different UMF/PMDI compositions over a range of F-emission levels, is described. An indication is given of possibilities and limitations of the system in commercial practice.

The nature of the lamellar overgrowth in polyethylene shish-kebab fibres as revealed by small-angle X-ray scattering and electron microscopy

Abstract: The melting, dissolution and crystallization behaviour of the lamellar overgrowth in polyethylene shish-kebab fibres have been studied by small-angle X-ray scattering and electron microscopy. SAXS experiments in which fibres were heatedin situ demonstrated the irreversible reorganization of the lamellar overgrowth already at 60° C. Reorganization continued in an inhomogeneous manner until the fibre lost its porosity around 140° C. The morphology that developed upon cooling depended on the crystallization temperature as well as on the maximum temperature attained before crystallization. Transmission electron microscopy observations showed the influence of molecular weight on aggregation. The SAXS patterns obtained duringin situ dissolution experiments disclosed that the lamellae dissolved in dodecane above 115° C. Recrystallization of the lamellae on to the backbones was almost complete within 10 min at 110° C. These high temperatures, as compared with single-crystal behaviour, indicate that the cilia nucleated with exceptionally high stem lengths on to the backbones. SAXS of fibres elongated to a maximum ratio of 1.5 at 90° C demonstrated the role of the lamellar overgrowth as a matrix between the elementary fibrils. The shish-kebab morphology could be restored after elongation by selective dissolution of the lamellae and recrystallization.

Pulse Induced Critical Scattering from solutions of randomly crosslinked polystyrene in cyclohexane

Abstract: The spinodal decomposition was observed by the Pulse Induced Critical Scattering technique for the three branched polystyrenes in cyclohexane. Branched polystyrenes were prepared by γ-irradiation on linear polystyrene of narrow molar-mass distribution for various periods. The location of the spinodals was hardly affected with regard to temperature though the crosslinking has increased the molar mass by a factor 10.

Acid halide functional materials and process for their preparation

Abstract: A composition containing one or more acid halide functional materials selected from those of the formula: wherein: X is halogen; b is an integer equal to 2 or more; R is an alkyl, aryl, aralkyl, halogen, alkyloxy, aryloxy, aralkyloxy of Z is a segment of: (1) a polyether, provided said polyether is not solely a polyarylene polyether; (2) a polyester containing polyether or polymeric hydrocarbon segments; (3) a hydrocarbon; (4) a polysiloxane; or (5) mixtures thereof, wherein the average value of b of all the acid halide functional materials in said composition is greater than two. The composition is useful for preparing nylon block polymers.

Preparation of derivatives of dichloroacetic acid esters

Abstract: The invention relates to a process for the preparation of derivatives of dichloroacetic acid esters, by reaction of a glyoxylic acid ester having the general formula R 1 --CO--COOR 2 , wherein R 1 represents an optionally substituted aryl or heteroaryl group and R 2 an alkyl, cycloalkyl or aryl group, with phosphoruspentachloride in the presence of a dispersant suitable for distributing the phosphoruspentachloride.

Process for the preparation of molded nylon block polymers

Abstract: A process for preparing a molded nylon block copolymer, which comprises (A) bringing into reactive admixture a lactam monomer, a basic lactam polymerization catalyst and a composition containing a lactam functional material selected from those of the formulae: wherein: Q is -N-C = 0, with Y equal to C 3 -C 11 alkylene; b is an integer equal to 2 or more; R is an alkyl, aryl, aralkyl, alkyloxy, aryloxy, aralkyloxy or Q group; Z Is a segment of: (1) a polyether, provided said polyether is not solely polyarylene polyether; (2) a polyester containing polyether or polymeric hydrocarbon segments; (3) a hydrocarbon; (4) a polysiloxane; or (5) mixtures thereof, and (B) allowing the admixture to polymerize in a mold.

Partially esterified and partially neutralized alkyl succinic anhydride resins and their use in printing inks

Abstract: The invention provides a process for the preparation of resins for printing inks in which an alkyl succinic anhydride resin is partially esterified with a polyhydroxy compound containing at least two methylol groups and at least one phenolic hydroxyl group in the molecule together with a C4-C12 alkyl group and subsequently partial neutralization is effected with a reactive compound of a metal of Group II of the Periodic Table.

Resins and their use in coating compositions

Abstract: The invention provides resins suitable for solvent-based varnishes containing nitrocellulose, which resins are the reaction product of 1.5-2.5, preferably 1.75-2.25 moles of dicyclopentadiene per mole of alpha-beta unsaturated dicarboxylic acid, which resin has an average molecular weight of 600-900, an acid value of 70-100, a saponification index of 250-300, a bromine index of 60-100 and a softening point of 100-160°C. The resins are prepared by initial reacting at 100 to 140°C and subsequently at 175 to 250°C. Preferably a mineral acid catalyst is used.