Per Flodin

Methodological aspects of gel filtration with special reference to desalting operations

Abstract 1. A study of the gel filtration method has been made in order to find the optimal conditions for removing salts from proteins. 2. The column efficiency increases with decreasing particle size and flow rate. 3. The viscosity of the sample rather than the concentration is a limiting factor. 4. Gel filtration of a protein solution is equivalent to an exhaustive dialysis but it can be carried out in a much shorter time. 5. The mechanism of the process is discussed.

Interactions of polymers and organic admixtures on portland cement hydration

Abstract Interaction of polymers and other organic admixtures on Portland cement hydration is reviewed. This has been compiled in a systematic way. First hydration of Portland cement is described in short. Later, interaction with 4 important components of Portland cement is discussed. Finally interphase effects in polymer modified hydraulic cement are discussed. It is concluded that polymers and organic admixtures interact with the components of Portland cement when they come in contact with water. This interaction is due to ionic binding, causing cross-links which inhibit the film formation property of polymers and influence considerably the crystallisation process during the hardening of concrete. Some low molecular weight organic substances also have a considerable influence on Portland cement during its reaction with water.

Monosized polymer particles in size-exclusion chromatography : I. Toluene as solvent

Abstract Monosized macroporous poly(styrene-divinylbenzene) particles were prepared by a multi-step swelling process. The preparation of particles of different sizes (5, 10 and 20 μm) with similar pore-size distributions allowed a selective evaluation of the effect of particle size on column efficiency. All three particle sizes yielded columns with similar calibration graphs, which was to be expected because of their nearly identical pore-size distributions. The uniform packing which may be achieved with monosized particles resulted in columns with high efficiency and separation capacity. With 5-μm particles more than 50 000 theoretical plates were obtained in a 30-cm column (HETP ≈ 0.006 mm). The resolution, as measured by the parameter Rsp, was good throughout the experiments and especially high for the 5-μm particles. The theoretical prediction that HETP is proportional to the square of the particle diameter was confirmed by the experimental data.

Behaviour of calcium hydroxide with styrene-methacrylate polymer dispersion

Abstract The behaviour of Ca(OH) 2 on styrene-methacrylate polymer dispersion is studied. Ca(OH) 2 interacts with the polymer dispersion leading to precipitation and loss of filmforming ability. X-ray diffraction analysis has shown changes in 17–23 degree (2⊝) area. Heating the mix of Ca(OH) 2 with dispersion after treating with hydrochloric acid leaves a residue. This certainly is CaO which interacted with polymer dispersion and formed a complex. This is due to interaction between divalent calcium ions and carboxylic group in the dispersion leading to cross-linking with no filmforming character.

High-resolution 13C nuclear magnetic resonance studies of an unsaturated polyester in the solid state

Abstract Unsaturated resins crosslinked with styrene, have been investigated by magic angle spinning-cross polarization (MAS-CP) 13C n.m.r. and relaxation times in the rotating frame obtained. The relaxation times T1ϱ obtained ranged from 2 to 34 ms, and were found to change with cure temperature in the polyester resin with a maximum value observed for all carbons when curing proceeded in the temperature region 80°C–90°C. The relaxation times evaluated indicate that more complete crosslinking occurs at temperatures in this temperature region indicating that there was a correlation between T1ϱ and the cure temperature. There was also a common pattern for all carbon atoms and similarly a strong influence on relaxation time existed for all carbons in the cured polyester. The corresponding main-chain motions are mainly cooperative which, with a suggested spin-lattice relaxation mechanism will be a significant influence on the molecular mobility along with the cure temperature. This influence on the molecular mobility is dependent on the carbon chain polymer length and thereby on the number of endgroups in the carbon chain polymer.

Structure of the carbon chain polymer in unsaturated polyesters

Abstract The curing behaviour of thick laminates was simulated by curing thin polyester sections isothermally at various temperatures. Unsaturated polyesters with different ratios of styrene to unsaturations in the polyester were cured with benzoyl peroxide and subjected to hydrolytic degradation. The molecular size and structure of the carbon chain polymer was examined by size exclusion liquid chromatography and high resolution 13 C FT n.m.r. analysis and was found to depend on the reaction temperature. The overall values of the molecular weights ranged from 12 000 to 36 000, which is a magnitude lower than those reported earlier. There was a similar tendency for molar ratios of styrene to unsaturations in the resin varying between 1.25 and 2.00. In the region 60°C–80°C the molecular weight increased with increasing temperature and then, from a maximum at 80°C–90°C, the molecular weight decreased with cure temperature. For the molar ratio of styrene to unsaturations of 2.25 the molecular weight decreased with increasing cure temperature. The average styrene sequence lengths were not found to deviate from the ratio expected from the stoichiometry in the resin before curing except for temperatures below 70°C and above 120°C.

Kinetics of the Alkaline Dehydrochlorination of Polyvinyl Chloride)

Abstract From previous investigations of the alkaline dehydrochlorination of PVC it is well known that polyene sequences are formed. In this paper the true overall kinetics of the dehydrochlorination reaction between PVC and alcoholic KOH in tetrahydrofuran solution was studied at 9.5°C by measuring the rate of disappearance of KOH. Titrations of the hydroxide ions consumed and the chloride ions evolved showed close agreement. IR spectra of the samples did not show any evidence of substitution by hydroxide ions. Small amounts of DMSO present in the solvent were found to increase the reaction rate markedly. The kinetic scheme was discussed and the first rate constant was determined. Preliminary results of reactions of the polyene sequences with various reagents are presented. These reactions were made in order to introduce new functional groups into the PVC chains.

Surface modification of ethylene copolymers molded against different mold surfaces. Part 2. Changes at the outermost surface

The influence of the mold surface on the surface composition of thermoplastics has been investigated. Two different random copolymers, poly(ethylene-co-acrylic acid) (EAA) and poly(ethylene-co-vinyl acetate) (EVA), with varying comonomer contents were used. Specimens were prepared in molds coated with films of perfluorinated ethylene-propylene copolymer (FEP) and of poly(ethylene terephthalate) (PET). Samples were also molded against air and vacuum. Changes in the concentration and arrangement of the functional groups at the outermost surface were studied using X-ray photoelectron spectroscopy (XPS or ESCA), Fourier transform infra-red techniques (FTIR), and contact angle measurements. The concentration of functional groups at the outermost copolymer surface depended on the nature of the surface against which the random copolymers were molded. Results are interpreted in terms of differences in surface energy between the mold surface and the copolymer. The polar acrylic acid groups in EAA increased when mo...

Surface modification of ethylene copolymers moulded against different mould surfaces-1. Surface enrichment by functional groups

A polymer surface chemical composition can be changed by the influence of different environments. Results presented from this study show that the surface of the mould influences the outermost polymer surface by enriching it with specific functional groups. This was done by moulding random copolymers against polymer films with low and high surface energies. The values presented are interpreted in terms of differences in surface energy between the mould surface and the copolymer. The random copolymers used were poly(ethylene-co-vinylacetate) (EVA) and poly(ethylene-co-acrylic acid) (EAA), both with a different comonomer content. The copolymers were moulded in contact with mould surfaces made of polymer films which were perfluorinated ethylene propylene copolymer (FEP), poly(tetrafluoroethylene) (PTFE), and poly(ethylene terephthalate) (PET). The resultant surfaces were characterized by X-ray photoelectron spectroscopy (XPS or ESCA) and contact angle measurements The surface content of acrylic acid functiona...

Reactive carriers for the immobilization of copper ions

Abstract Macroporous functionalized gels based on copolymers of trimethylolpropane trimethacrylate and glycidlyl methacrylate were prepared for the adsorption of copper ions. The gels were functionalized with iminodiacetate, tris(2-aminoethyl)amine, tetraethylenepentamine (TEPA) and ammonia. The most favourable conditions for obtaining a high yield of TEPA were a high concentration of TEPA in the reaction mixture (at least 3 mol of TEPA per mole of epoxy), toluene as solvent, elevated temperature (70°C) and at least 4 h of reaction.