Search results for "PLASTICS"
showing 10 items of 2724 documents
Chiral/Achiral Copolymers of Biphenylylacetylenes Bearing Various Substituents: Chiral Amplification through Copolymerization, Followed by Enhancemen…
2020
A series of dynamic helical homo- and copolymers of chiral and/or achiral biphenylylacetylenes (PBPAs) bearing achiral methoxymethoxy or acetyloxy groups at the 2,2′-positions along with a chiral o...
Polymerized Ionic Liquids with Polythiophene Backbones: Self-Assembly, Thermal Properties, and Ion Conduction
2018
Single ion conductors, based on polymerized ionic liquids (PILs) with a polythiophene backbone bearing imidazolium salts with butyl, hexyl, octyl, and decyl side groups and six different counterani...
The Relevance of Kneading and Extrusion Parameters in the Manufacture of Active Porous Aluminas from Pseudoboehmites
1987
In order to study the effect-on crushing strength, attrition resistance, specific pore volume, and pore volume distribution of extrudates-of kneading and extrusion parameters in the manufacture of active porous aluminas, a commercial pseudoboehmite (Pural SB from Condea Chemie, Brunsbuttel, FRG) was employed. A minimum kneading torque was required to prepare an extrudable paste, predetermined by extrusion conditions. The torque had an upper limit with respect to certain extrudate properties. The amount of water and the concentration of nitric acid as binder solutions were found to have a decisive bearing on the mechanical properties and the distribution of the pore volume. Crushing strength…
Effects of microplastics on the functional traits of aquatic benthic organisms: A global-scale meta-analysis
2021
Microplastics are widespread in the aquatic environment and thus available for many organisms at different trophic levels. Many scientific papers focus their attention on the study of the effects of microplastics on different species at individual level. Here we performed a global scale meta-analysis focusing our work on the study of the effect of microplastics on the functional traits of aquatic benthic organisms. Overall, microplastics showed a moderate negative effect on the examined functional traits of benthic organisms. Our results show that some crucial functional traits, such as those linked to behaviour and feeding, appear to be unaffected by microplastics. In contrast, traits rela…
Sedimentation of dissolved macromolecules in the vicinity of the consolute point 1. Strictly binary systems and kinetic considerations
1986
This paper analyzes the effect of gravity on polymer solutions near the consolute point. Calculations are carried out for monodisperse polystyrene in cyclohexane using the Flory-Huggins expression with a concentration-dependent interaction parameter for the free energy of mixing. Depending on molecular weight and distance to the demixing temperature, the influence of gravity leads to non-negligible gradients of the volume fraction in the one-phase region as well as in the two-phase region. In particular, the effect of gravity on the measurement of the coexistence curve in a finite sample is calculated explicitly.
Calculation of phase diagrams not requiring the derivatives of the Gibbs energy demonstrated for a mixture of two homopolymers with the corresponding…
1995
A method is presented which allows the calculation of phase diagrams (spinodal, binodal and tie lines) on the basis of the Gibbs energy of mixing ΔG. No derivatives of ΔG with respect to the composition variables are required. This method is particularly useful in cases where the composition dependence of ΔG is very complex and no analytical representation of the derivatives can be given. The method is applied to a ternary mixture of two homopolymers with a copolymer consisting of the same monomers. The sequence distribution of the copolymer is kept constant between random and purely alternating, and phase diagrams are calculated for different chemical compositions of the copolymer. The com…
Thermodynamics of a polymer blend solution system studied by gel permeation chromatography and viscosity
1999
Binary and ternary interaction parameters and their derivatives have been calculated with the Flory-Huggins formalism developed for a ternary polymer system. The equilibrium compositions of the ternary system tetrahydrofuran/polybutadiene/polystyrene that forms two phases in equilibrium at 25°C have been used to solve the binodal equations. With this set of parameters, the viscosimetric interaction parameters have been computed. For the sake of comparison, the experimental viscosimetric parameter has been determined from intrinsic viscosity data of a polymer (3) in a "binary solvent" (solvent + polymer (2)). It has been clearly shown that composition-dependent parameters are necessary to re…
Demixing time and temperature influence on porosity and interconnection of PLLA scaffolds prepared via TIPS
2009
Scaffolds suitable for tissue engineering applications were prepared by Thermally Induced Phase Separation (TIPS) starting from a ternary solution PLLA/ dioxane/water. The experimental protocol consisted of three consecutive steps, a first quench from the homogeneous solution to an appropriate demixing temperature (within the binodal region), a liquid-liquid demixing stage for a given time and a final quench from the demixing temperature to a low temperature (within the spinodal region). A large variety of morphologies, in terms of average pore size and interconnection were obtained upon modifying the demixing time and temperature, owing to the interplay of nucleation and growth processes d…
Calculation of miscibility behavior of multinary polymer blends
1996
A method for the calculation of phase diagrams (tie lines and binodal, spinodal, critical points and their stability) based exclusively on the Gibbs energy of mixing, δG, is presented which does not require the calculation of the derivatives with respect to the composition. The method is demonstrated for ternary mixtures of two homopolymers and the corresponding copolymer, and for quaternary and quinternary blends of five polymers exhibiting a closed miscibility gap. The advantages of the presented method become most obvious in the mathematical description of measured phase diagrams, where complex composition dependencies of the interaction parameter are observed.
Compatibility between polystyrene copolymers and polymers in solution via hydrogen bonding
2006
Abstract It has been applied the concept of improving miscibility, by introducing and optimizing the extent of intermolecular hydrogen-bonding interactions between two polymers. We select a commodity polymer such as polystyrene, to study the compatibility in chloroform with poly(vinyl pyridine) and poly(vinyl pyrrolidone), both considered as proton acceptors. In order to enhance polymer–polymer miscibility, polystyrene is slightly modified by copolymerization with methacrylic acid, in the first case, and with vinyl-phenol comonomer, in the second one. In this way, two series of polystyrene-based copolymers are synthesized and characterized bearing ca. 8% (w/w) of –OH groups. The miscibility…