Showing papers in "Colloid and Polymer Science in 1979"

Studies on the preparation and characterization of monodisperse polystyrene latices V.: The preparation of cationic latices

Abstract: Methods are described for the preparation of monodisperse polystyrene latices using as initiators, 2-azo-bis-(2-methylpropamidinium) dichloride and 2-azo-bis-(2′-isopropyliminazolium) dichloride. The preparations were carried out in the absence of any added surface active agents. The effect on particle size of varying initiator concentration, monomer concentration, temperature and ionic strength was examined and the conditions defined for preparing monodisperse latices, with particles in the size range 0.2 to 1μm. Electrophoretic measurements confirmed that the latex particles were cationic. The evidence obtained suggested that the charged sites on the particle surface were amidinium groupings. The latices were not stable at pH values greater than 11 and prolonged heating at 90° also caused coagulation.

Adsorption characteristics of certain polyoxyethylene-polyoxypropylene block co-polymers on polystyrene latex

Abstract: The adsorption of a series of commerical polyoxyethylenepolyoxypropylene block copolymers onto polystyrene latex has been studied. Adsorption was Langmuirian in all cases with maximum adsorption occuring after the apparent critical micelle concentration had been reached. Examination of molecular areas at the interface indicate that for high ethylene oxide content surfactants, the hydrophilic chains adsorb as loops. This was confirmed by measurements of the adsorbed layer thickness determined by intensity fluctuation spectroscopy and microelectrophoresis.

Dependence of the equilibrium thickness and double layer potential of foam films on the surfactant concentration

Abstract: The effect of the surfactant concentrationc s on the equilibrium thicknessh r , of foam films and the potentialϕ 0 of the diffuse electric layer is studied in a wide concentration range (including cmc). The cell for investigation of thin liquid films is improved and a good reproducibility of the measuredh r is obtained. The possibilities for determination of the capillary pressureP σ in.the cell for investigation of microscopic thin liquid films are discussed. The values ofP σ can be measured with sufficient accuracy by the capillary-rise method, using a tube, identical with the tube of the cell for thin liquid films. The dependenceh r (c s ) is studied for nonionic surfactants (decylmethyl sulphoxide, nonyl-phenol 20-glycol ether and dodecyl 11-ethylene oxide) and the ionic sodium dodecyl sulphate. After reaching a steady value (a plateau in theh r (c s ) curve) at high concentrations (about cmc) a decrease in the equilibrium thickness of nonionic surfactants is found. The possible reasons for this decrease are discussed. It is shown that this effect probably is due to the electrostatic disjoining pressure. The values of theϕ o-potential at the plateau of theh r (c s ) curves are determined by the DLVO-theory using theh r , values. The so determinedϕ 0-values are more correct than the obtained earlier by this method because of the more precise measurement of the equilibrium thickness and the direct experimental determining of the capillary pressure. A qualitative interpreting of theϕ 0(c s ) dependence is made on the basis of the surfactant adsorption at the solution/air interface and it is found that for nonionic surfactants the surface charge saturation is very near to the saturation in the adsorption layer, and for the ionic surfactants the adsorption layer saturation is at higher concentration.

Obtention de ≪ monocristaux ≫ de copolymères triséquencés styrène/isoprène/styrène par cisaillement plan

Abstract: SIS Copolymerproben (Styrol-Isopren-Styrol) werden in geschmolzenem Zustand einer Scherung unterworfen. So wird bei Orientierung eine gut ausgebildete Monokristalltextur in den Proben erreicht. Im Falle einer zylindrischen Struktur orientieren sich alle Zylinder parallel zur Scherungs-Richtung, und es kommt zu einer einheitlichen Ordnung in der ganzen Probe. Die Scherung wird mit dem vor- und ruckwarts gegeneinander Gleiten zwischen zwei parallelen Metallplatten mit einer gleichmasigen Geschwindigkeit erzielt. Ein Mechanismus des Orientierungsprozesses wurde vorgeschlagen, aber weitere experimentelle Prufungen sind noch notwendig.

A new approach to the continuum theory of birefringence of oriented polymers

Abstract: The internal field in a transparent anisotropic dielectric is described with the aid of the classical electromagnetic theory by the introduction of the internal field or Lorentz-factor tensor. On the basis of the internal field equation generalized Lorentz-Lorenz relations are derived. A virtual refractive index in lieu of the mean refractive index is defined by the trace of the inverse susceptibility tensor. By the same token the harmonic mean replaces the arithmetic mean specific refractivity. The relation between birefringence, polarizability and structural anisotropy of the medium is formulated.

The colloidal behaviour of kraft lignin: Part I.: Association and gelation of kraft lignin in aqueous solutions

Abstract: SummaryThis paper deals with an experimental investigation aimed at determining the extent of and the nature of the aggregation behaviour of kraft lignin (Indulin AT), in aqueous solutions.Gel permeation chromatography (GPC) in dimethylformamide (DMF) revealed a bimodal molecular weight distribution of kraft lignin. The high molecular weight fraction (sol fraction) was isolated by dialysis and used in this investigation.Stable lignin sols in aqueous solutions, which were not light scattering as determined by the naked eye, were prepared. The extent of aggregation of these sols was followed viscometrically under different pH-conditions. Aggregation was found when the pH was lowered.The extent of aggregation as determined from viscosity measurements was found to increase irreversibly with storage time and storage temperature. Prolonged heating induced the formation of a 3-dimensional network (gelation). Although both association and gelation were thermally irreversible, it was found that the cohesive interactions could be broken by deprotonization of the carboxylic groups. The aggregation is discussed with reference to previous publications in the field.It is suggested that the long-range van der Waals forces play an important role together with intermolecular and intramolecular associations of the carboxylic groups.ZusammenfassungVorliegender Artikel berichtet über experimentelle Untersuchungen mit der Zielsetzung, des Ausmaß und die Natur des Aggregationsverhaltens von Kraftlignin (Indulin AT) in wäßrigen Lösungen zu bestimmen.Gelpermeations-Chromatographie (GPC) in Dimethylformamid (DMF) zeigte, daß beim Kraftlignin eine bimodale Molekulargewichtsverteilung vorlag. Die hochmolekulare Fraktion (Sol-Fraktion) wurde durch Dialyse isoliert und in vorliegender Untersuchung verwendet.Klare stabile Ligninsole wurden in wäßrigen Lösungen erhalten, die visuell keine Lichtstreuung zeigten. Das Ausmaß der Aggregation dieser Sole unter verschiedenen pH-Werten wurde viskosimetrisch verfolgt. Eine Aggregation wurde beobachtet, wenn der pH-Wert herabgesetzt wurde.Das Ausmaß der Aggregation, bestimmt aus den viskosimetrischen Messungen, nahm irreversibel mit der Lagerungszeit und Lagerungstemperatur zu. Lange andauerndes Erhitzen führte zur Bildung eines dreidimensionalen Netzwerks (Gelierung). Obwohl Assoziation wie auch Gelierung thermisch irreversibel waren, wurde gefunden, daß die kohäsiven Bindungskräfte durch Deprotonisierung der Carboxylgruppen aufgebrochen werden konnten. Die Aggregation wird im Lichte früherer Veröffentlichungen auf diesem Gebiet diskutiert.Es wird angenommen, daß die weitreichenden van der Waalsschen Kräfte zusammen mit inter- und intramolekularen Assoziationen der Carboxylgruppen eine wichtige Rolle spielen.

Negative Hamaker coefficients

Abstract: A study of the compatibility and incompatibility of 31 combinations of solutions of pairs of polymers in various common solvents was undertaken. A new approach, which utilizes the sign of the combined Hamaker coefficients (A132), was used. In this approach, phase separation is predicted to occur ifA132 is negative, and mixing ifA132 is positive. The Hamaker coefficients were derived from interfacial free energies. Good agreement between theory and experiment was obtained for systems at low polymer concentrations and for values forA132 farther removed from 0 than ≈ ± 0.3 X 10−14 ergs. The concentration dependence of the phenomenon has been studied more closely with eight of these solutions of polymer pairs, and the influence of polymer concentration on the surface tension of the liquids has been elucidated.

Thermal properties and volume fraction of the boundary interphase in metal-filled epoxies

Abstract: A previous study (1) on the thermomechanical behaviour of metal-filled Epoxies led us to conclude that the concept of the boundary interphase is a very useful tool for describing quantitatively the quality of adhesion between the matrix and the filler particles. It was shown that this interphase exists in reality and is an area between filler and matrix, which contains both areas of adsorption interaction in polymer surface layers into filler particles, as well as an area of mechanical imperfections. In the present paper, under the assumption that the interphase is homogeneous and isotropic, exhibiting perfect adhesion with both main phases, a theory was developed to describe the thermomechanical behaviour of this interphase. Thermal expansion coefficients and volume fraction of the interphase of a large number of composites were determined and the effect of various parameters, such as temperature, volume fraction of filler and particle size, were examined for specimens exhibiting imperfect as well as perfect adhesion between matrix and filler.

Negative Hamaker coefficients I. Particle engulfment or rejection at solidification fronts

Abstract: Calculated Hamaker coefficients were obtained from free energies of adhesion, derived from contact angle data, for several polymers, as a function of the separation. Comparing these values with published Hamaker coefficients, an equilibrium separationd0=1.82 A for various systems was established. It was demonstrated that the Hamaker coefficients A12 calculated from the free energy of adhesion agreed very well with those calculated from the free energy of cohesion, using Berthelot's rule. Visser's procedure of modifying the combining rule to calculateA132 fromAij values was tested and confirmed. Hamaker coefficientsA132 for the interaction of various polymer particles, embedded in naphthalene melt, with the naphthalene solidification front turned out positive in some cases and negative in others, thus predicting attraction of some particles by the solidification front and repulsion of others. These predictions were compared with microscopic observations of the behaviour of particles at the solidification front by which they become either engulfed (attraction) or rejected, i. e. pushed along (repulsion). There was good agreement between prediction and experimental observation.

The effect of long-chain alkanes on the stability of oil-in-water emulsions. The significance of ostwald ripening

Abstract: A number of investigations have shown that o/w emulsions made from or containing small quantities of long-chain alkanes are more stable than those made from short-chain alkanes or other simple oils. Two principle explanations for this behaviour have been suggested, one stating that the long-chain component inhibits Ostwald ripening, the other that it inhibits droplet coalescence. With the aid of adsorption, centrifuge and kinetic experiments it is shown that the effect probably arises from a slower rate of Ostwald ripening in emulsions containing long-chain alkanes. The effect of the nature of the oil phase on the van der Waals interaction between emulsion droplets is also considered.

Velocity of high frequency sound waves in oriented DNA fibres and films determined by Brillouin scattering

Abstract: We have measured the velocity of acoustic microwave phonons in fibres and films of oriented DNA. The sound velocity is found to be surprisingly isotropic and to decrease substantially during hydration of DNA. No optical modes have been detected in the frequency range covered from 5 to 120 GHz. The photoelastic constants are strongly anisotropic.

Effect of annealing on thermal properties and crystalline structure of polyamides. Nylon 11 (polyundecaneamide)

Abstract: The effect of prolonged annealing at a low super-cooling on the thermal properties and crystalline structure of nylon 11 has been investigated. Annealed nylon 11 formed the lamellar spherulites of the alpha-crystalline modification. Thickness of the lamellae increased with time of annealing from 50 to 165 A for the samples annealed for 20 and 2000 hours respectively. Corresponding values of the melting temperature and the heat of melting increased from 190 °C and 10 cal/g to 211 °C and 20 cal/g. The extrapolated heat of melting of the crystalline phase of nylon 11 is 47 cal/g.

A small angle X-ray scattering study of polyethylene fibres, using the two-dimensional correlation function

Abstract: By Fourier transformation of the intensity distribution in the small angle X-ray scattering diagram of a polymer fibre one obtains the corresponding two-dimensional correlation function. This is compared with correlation functions calculated on the basis of different models of the semi-crystalline morphology. Here, two steps may be distinguished: in the first, the correctness of a model may be checked with the aid of qualitative features, such as the relative positions and sizes of positive and negative areas; in the second a quatitative agreement is pursued by fixing the various parameters involved. This method was applied to cold drawn low density polyethylene before and after annealing at different temperatures. In the case of the non-annealed sample, the microparacrystalline model, discussed byHosemann andLoboda-Cackovic (J. Appl. Cryst.11, 540 (1978)) was found to give the best fit. Annealing at 80 °C or higher temperatures seems to lead to what has been indicated as a three-dimensional chess-board structure; it consists of fibrils in which crystalline and amorphous regions alternate in such a way that the crystalline regions in a fibril are adjacent to amorphous regions in neighbouring fibrils.

Interaction of acridine orange monohydrochloride dye with sodiumdodecylsulfate, (SDS) cetyltrimethylammoniumbromide (CTAB) and p-tert-octylphenoxypolyoxy ethanol (Triton X 100) surfactants

Abstract: Results of spectrophotometric, conductometric and dialysis studies on the interaction of acridine orange monohydrochloride dye with sodiumdodecylsulfate (anionic), cetyltrimethylammoniumbromide (cationic) and Triton X 100 (nonionic) surfactants have been reported. The anionic surfactant, SDS has been observed to undergo both electrostatic and hydrophobic interactions with the dye cation. Aggregation of the dye molecules can be destroyed when the surfactant is in large excess, whereas, excess dye can check micellization of SD S. At a ratio of AO:SDS=1:7 and above, dye embedded mixed micelles are formed. These remain in a separate phase, probably as coacervates. At lower ratios than 1:7, aggregation of dye molecules is induced, which being complexed with SDS become stabilized as colloids. The colloid and the coacervate have been observed to be thermally stable, negatively charged materials that can be broken by salts, and cations of higher valency are more effective in this regard. An 1:3 = AO:SDS colloid has beeen found to be sufficiently large like the coacervates to pass through a membrane having cut off permeability for molecular weights 12,000 and above. All the above features of AO-SDS interaction have been observed to be absent for AO-CTAB and AO-TX 100 systems, Even hydrophobic interaction has played an insignificant role in these cases. Thus, the dye cation, the cationic and the nonionic surfactants have almost retained their self physicochemical identities in solution in the presence of each other. Electrostatic interaction is thus the primary requirement for acridine orange-surfactant (anionic) system; the hydrophobic effect is secondary and may become co-operative.

Characterization of colloidal wood resin in newsprint pulps

Abstract: The dispersed colloidal wood resin in newsprint pulps has been characterized in samples taken from mills both during periods of pitch difficulties and during periods of smooth operation. The chemical composition of the resin particles in pitch troublesome and nontroublesome pulps resembled those of the extractives in freshly cut and seasoned wood, respectively, which suggests that pitch problems were encountered when the mills were pulping relatively unseasoned wood. Electrophoretic mobilities of the resin particles, measured as functions of pH, and particle size distributions were the same, within experimental error, in troublesome and nontroublesome pulps. Much higher resin particle concentrations were observed in pitch troublesome samples, which has led to a previously published method for forecasting or diagnosing certain types of resin problems. The shelf life of colloidal wood resin suspensions in their native process liquids is considerable; particle concentration half-lives of the order of 5 months were observed. Stability was unaffected even by relatively high concentrations of Na+, Ca2+ and Al3+, which suggests that the stability of the particles is governed by more than surface charge effects and that steric stabilization plays a role.

Miscibility of phospholipids and cholesteryl acetate in mixed monolayers on aqueous surfaces

Abstract: The surface pressure — area per molecule curves (F A curves) of mixed monolayers of phosphatidyl serine (PS) and cholesteryl acetate (CA), and those of dimyristoyl phosphatidyl choline (DMPC) and CA were measured on aqueous surfaces. ThoseF — A curves showed kink points, which were considered to be the collapse point of the monolayers. Then, the collapse pressure was determined as the surface pressure at the collapse points. On the basis of the phase diagrams, drawn by plotting the measured values of the collapse pressure as a function of the composition, the miscibility of the lipids in the mixed monolayers was discussed. Thus, it has been concluded that PS and CA, and also DMPC and CA are completely miscible in the monolayers on water. On the other hand, it has been also found that, on aqueous solutions of 100 mM CaCl2, PS and CA are immiscible in the monolayers because of the aggregation of PS molecules induced by Cat2+.

Long range intermixing of paraffin molecules in the crystalline state

Abstract: Evidence is presented for the unexpected effect that long chain paraffin molecules, at least as long as C36H74, can intermix when comprised by separate macroscopic crystals in contact, below the melting point and even below the rotary phase transition. This effect implies much greater mobility of paraffin chains in what is regarded as solid phase than normally envisaged and is likely to be of consequence for reorganization in polymer crystals.

Ein Modell für die diffusionskontrollierte Adsorption von Tensidgemischen an fluiden Phasengrenzen

Abstract: Fur den Fall der diffusionskontrollierten Adsorption von Tensidgemischen wird ein Integralgleichungssystem als Ergebnis und eine Moglichkeit fur dessen numerische Losung angegeben. Anhand von numerischen Ergebnissen fur den Fall, das eine verallgemeinerte Langmuir-Isotherme das Adsorptionsgleichgewicht beschreibt, wird der Vorgang der Gemischadsorption von zwei in der Losung befindlichen Tensiden diskutiert.

Demixing of unsheared and sheared solutions of polystyrene in tert-butylacetate and the pressure influence on their flow behaviour

Abstract: For the system tert-butyl acetate/polystyrene (M= 670000) the phase separation behaviour (upper critical solution temperatures, upper critical solution pressures) is investigated by means of visual and turbidimetric cloud-point measurements and by viscometry. For near-critical concentrations the visually determined cloud-points are found at higher, for low concentrations at lower temperatures as compared with the turbidimetrically determined binodal temperature,Tbin Plots of the invers of the turbidity measured atTbin as a function of the polymer concentration,w2, yield a minimum from which the critical composition can be determined. The viscometrically obtained demixing points (break-down of the viscosity at normal and at elevated pressures) show that the polymer solutions are stabilized at moderate concentrations. Irrespective of the preselected temperatures and of the present shear-rates (90-640 s−1, the demixing pressures are reduced by almost 20 bar. At sufficiently dilute or concentrated solutions the viscometric demixing points approach the binodal points. The above influences of the shear-field are explained by the rupture of intermolecular segment/segment contacts, which will be most efficient in the neighbourhood of the critical concentration for the formation of entanglements. In the case of the homogeneous solutions, the viscosity coefficientn increases in a fairly exponential manner by a factor of 3-4 per 1000 bar within the range ofp,T,w2 and shear-rate under investigation (1–1000 bar, -25 to f20 °C, 4–10 wt-% and 25–640 s−1). In plots of logn or ofV* (volume of activation) vs. concentration, extra effects show up when the critical conditions are approached; they result in a “hump” in logn vs.wn2 and in a minimum in V* vs.w2.

Influence of the pressure in the Plateau-Gibbs borders on the drainage and the foam stability

Abstract: The effect of the pressure in the Plateau-Gibbs borders of the foam upon its drainage and its stability has been investigated. The principle of the method and the apparatus for applying pressure gradient in the Plateau-Gibbs borders of the foam are described. The kinetics of establishing of the capillary pressure in the Plateau-Gibbs borders of the foam in dependence of the height of the foam column, the applied pressure difference and the type of the surfactant has been studied. The obtained results are qualitatively confirmed by an investigation of the foam water content change (calculated by measurements of its specific conductivity) at the same experimental conditions. The influence of the increased drainage rate and respectively the decreased foam water content on the foam stability when a pressure gradient is applied in its Plateau-Gibbs borders is discussed. It is shown that the time for the foam destruction when a pressure gradient is applied in the foam Plateau-Gibbs borders can be used for characterising the foam stability at definite conditions.

Surface study on the rubber particles in pretreated Hevea latex system

Abstract: From centrifuged high-ammonia latex concentrate, a fraction which contains rubber particles of a narrow particle size distribution in a serum phase freed from any water-soluble non-rubber constituents was obtained. The electrophoretic mobility of the dialysed latex particles has been studied as a function of dry rubber content, surface pH and concentration of sodium chloride. The rubber particles were shown to have an amphoteric nature with an isoelectric point at pH 3.8. The electrokinetic study showed that the net negative charge on the rubber particle surface is derived from the carboxyl groups of the adsorbed proteins and the adsorbed long-chain fatty acids. This is in agreement with the infrared data of the rubber film. The surface charge density of the rubber particle at pH > 6 was found to be 1.43 ,µC cm−2. The stability of the latex is briefly discussed in terms of its surface charge and compared with that of synthetic latices.

Phase equilibria in water-protein-polysaccharide systems

Abstract: Phase equilibria in the ternary water-soy bean globulins-polysaccharides systems, containing various acidic and neutral polysaccharides (pectin, sodium alginate, carboxymethylcellulose, arabic gum, dextransulphate, and dextran) were studied. Phase diagrams of the systems were obtained. Effects of pH, concentration of a neutral salt and urea on the compatibility of soy bean globulins with polysaccharides in water media were studied. It has been shown that soy bean globulins could be incompatible with acidic carboxyl-containing polysaccharides in the whole studied range of pH (2–12) and NaCl concentrations (0–1 mol·l−1). Incompatibility of soy bean globulins with sulphated polysaccharides takes place only under condition of high ionic strength independently of pH of the system. Incompatibility of soy bean globulins with neutral polysaccharides at pH ≠ pI occured only at high ionic strength or in the presence of 6 M urea. The change pattern in separation bodies of the water-soy bean globulins-polysaccharide systems at pH pI and varied when passing from carboxyl-containing polysaccharides to sulphated or neutral. Under equal conditions compatibility of soy bean globulins with polysaccharides increased in the series: pectin < carboxymethylcellulose < sodium alginate < arabic gum < dextran < dextransulphate.

Generation and relaxation of the molecular orientation during hot-stretching of amorphous thermoplastics

Abstract: Between the mechanical properties and the molecular orientation of hot-stretched amorphous polymers there exist definite and univalent relationships which are independent of the stretching conditions. It, therefore, seemed of great interest to find out whether the orientation and thereby the mechanical properties of such materials can be predicted from their thermomechanical stretching history. In order to check this conjecture stress relaxation, tensile, creep, creep recovery, and free shrinkage tests were performed on polystyrene at temperatures between 105 and 140 °C. During these experiments the stress (or the strain) and the birefringence (as a measure of the orientation) were measured simultaneously. If polystyrene aboveT g would behave like an ideal rubber the true stressσ (force per actual cross section) and the birefringenceΔn should increase proportional to (λ 2 −λ −1) (λ = draw ratio). Furthermore the stress optical coefficientΔn/σ should be strain-independent. In reality, the measuredσ- andΔn-values increase more slowly than they would do in accordance with the rubber theory. In addition, both quantities are not only strain- but also time-dependent. They relax already during the stretching process. Nevertheless, the stress optical coefficient remains constant (i. e. strain- and time-independent as well) with the exception of the values obtained at temperatures below 120 °C. At these low temperatures the stress contains a considerable energy elastic part and consequently the quotient ofΔn andσ is reduced. Furthermore it turned out thatσ andΔn as functions of the Cauchy strain (λ − 1) formally follow the theory of linear viscoelasticity over a strain range up to about 600%. That means, ifσ andΔn are presented in isochronous plots, they prove to be linear functions of (λ − 1) in this range. According to additional experiments carried out on some other amorphous polymers the mentioned findings turned out to be true not only for polystyrene but also for high impact polystyrene, PVC, and PMMA over a strain range the upper limit of which is to be found between 100 and about 600%. The formally linear viscoelastic behaviour of these polymers aboveT g leads to the following consequences:

Investigation of protein foams obtained by bubbling

Abstract: The foaminesses ζ of bovine serum albumin solutions, (BSA) with and without buffer, salt and alcohol additives were measured by bubbling and their surface tensions σ were obtained as function of the timet. The timet DG , which is necessary to attain the equilibrium surface tension is long (∼15 h). The area requirement of a single surface adsorbed moleculeA j0 was obtained fromdσ/dc, wherec the surfactant concentration, by the Gibbs relation. By assuming the existence of a hydration complex, which consists of the surfactant andX water molecules, the,coordination numbers were estimated toX=12±1 fromA j0 and the surface requirement of the hydrophilic group of the surfactant. The dependences of CMC andX on the additives are discussed. A good relation prevails between ζ andt DG . By applying the phase change model of Avrami for the adsorption and surface denaturation of theBS A, simple relation was found between the dimensionless surface tensionV = (σ0 - σs∞) ∼ (σst-σs∞) and the timet: log (2.3 logV) =n logt + logb The good relations between ζ andn as well as between ζ andnb indicate the applicability of this model.

Mechanism of the grafting of organosilanes on mineral surfaces: II. Secondary reaction during the grafting of alkenylchlorosilanes

Abstract: SummaryThe grafting of minerals by alkenylchlorosilanes leads to organomineral derivatives which are superficially covered by unsaturated organic groups. These groups may be of value when the grafted mineral is used as a reinforcing agent in a polymeric matrix. In this case, the unsaturated grafted groups copolymerize with an organic monomer to build up a composite material. It is therefore of importance to preserve the unsaturated character of the alkenyl-silane during the grafting reactions. It is shown that in certain synthesis conditions, the hydrochloric acid present in the reaction medium adds to the alkenyl-groups. For instance, in the grafting of methylvinyl-dichlorosilane, this reaction is of minor importance, whereas in the case of allyldimethylchlorosilane, no allyl groups are grafted as such on the mineral surface.ZusammenfassungDie Pfropfung von silicatischen Mineralen mit Alkenylchlorosilanen führt zu organischen Derivaten, deren Oberfläche mit ungesättigten organischen Gruppen bedeckt ist. Diese Gruppen können Vorteile bieten, wenn die so behandelten Minerale als Fül-stoffe oder Verstärker in einer Polymermatrix eingesetzt werden. Die ungesättigten Gruppen können miteinem organischen Monomer kopolymerisieren und ein echtes Verbundmaterial bilden. Die Pfropfung muß allerdings so geführt werden, daß der ungesättigte Charakter der Alkenylsilane erhalten bleibt. In der Arbeit werden experimentelle Bedingungen dafür berichtet.

Relaxation of the surface energy of solid polymers

Abstract: The surface energy of a polymer can be increased by compression moulding against a metal substrate. After removal of the substrate relaxation to the equilibrium value sets in. We determined the rate of polymer surface energy relaxation as a function of temperature. For a vinyl chloride-vinyl acetate copolymer we determined an activation energy of the relaxation process that could be correlated to segmental motions in this polymer. For a plasticized polyvinylchloride we found a lower activation energy and a larger rate of relaxation, which is the result of the action of plasticizers on segmental motions. In the case of polyethylene the results indicate segmental motions in amorphous regions in the polymer. With polyethylene the activation energy drops when nearing the melt temperature. The movements of molecular segments correspond to a desorption process at the polymer surface, after removal of the substrate. This agrees with the adsorption during compression moulding, as repotted in earlier work.

Solubilization properties of nonionic surfactant-polymeric acid complexes

Abstract: The complex of a polyoxyethylene-type nonionic surfactant and a polymeric acid (polyacrylic and polymethacrylic acids) in aqueous solution has a different solubilization power from that of the micelles of the surfactant solution alone. From solubilization experiments it was found that the binding of the surfactant to a polyacid becomes abruptly conspicuous above a certain surfactant concentration, which is lower than the CMC of the surfactant. This critical concentration is considered as the concentration at the beginning of the micelle-like binding of the surfactant on the polyacid and is denoted as CMC p . CMC p is dependent upon the concentration of the polyacid when it is dissociated or at low concentrations, but is constant when undissociated and the ratio surf actant/polyacid is not too small. CMC p is also dependent on the kind of polyacid, and on the degree of polymerization only in the low range. CMC p is independent of temperature. In a series of nonionic surfactants of the same lipophilic moieties, the effect of polyacid addition on the CMC p is the larger the longer the polyoxyethylene chain. The interaction between polyacid and solubilizate plays a key role in the solubilization by the complex.

≪ Monocristaux ≫ de copolymères triséquencés styrène/isoprène/styrène présentant la structure cylindrique: I. Étude de l'orientation par diffraction des rayons X aux petits angles

Abstract: Des copolymeres trisequences polystyrene-polyisoprene-polystyrene, presentant la structure en cylindres ont ete soumis a un cisaillement plan.

Molekülordnung und Kristallinität in Polyhexamethylenadipamid

Abstract: Kalorimetrische, rontgenographische und IR-spektroskopische Untersuchungen und Dichtemessungen ergaben fur PA 66 eine bei anderen Polymeren unbekannte Anomalie. Die Abhangigkeit der Rontgenkristallinitatwc und der kristallinitatsproportionalen Grosen (experimentelle Schmelzwarme ΔH*, IR-Bandenintensitat) vom spezifischen Volumen andert sich mit den Kiistallisationsbedingungen. Dies ist die Folge eines konformationsbedingten Ubergangs zwichen zwei triklinen Modifikationen unterschiedlicher Dichte. Fur aus der Schmelze, dem Glaszustand und verdunnter Losung kristallisierte Proben treten bei allen drei Mesmethoden hinsichtlich der Abhangigkeit vom spezifischen Volumen drei Bereiche auf.

Compression studies on a monolayer of polymer stabilized latices at the air/2 molar sodium chloride solution interface

Abstract: The two dimensional compression technique ofDoroszkowski et al. has been used to study the steric repulsion force for a monolayer of poly(vinyl pyrrolidone) stabilized polystyrene latex particles spread at the Air/2M sodium chloride solution interface. Repulsion forces were first detected at a particle separation of 150 nm with a dramatic increase in repulsion at about 15 nm.