Paper polymer adsorption

At the symposium on which this book is based, the various authors presented papers on the general topic of polymer adsorption and particle stabilization/destabilization. In this volume both aqueous and nonaqueous systems are included, comprising work on both natural and synthetic polymers. Together the chapters constitute a comprehensive update of research in progress on these topics and provide broad coverage of both experimental and theoretical aspects. 

In this paper some of the current thinking in three closely-related areas is highlighted polymer adsorption the effect of polymer on the pairwise interaction between particles and the effect of polymers on dispersion stability. 

It would be an impossible task to summarize in one short review the many facets of this subject. This has been more than adequately attempted in several other recent reviews of the fields of polymer adsorption (1-4) and dispersion stability in the presence of polymers (J, 5-7). My objective, therefore, is primarily to set the scene for the papers that follow to highlight current theoretical and experimental work, and to indicate where future research efforts might conceivably be directed. 

A major advantage of the simple model described in this paper lies in its potential applicability to the direct evaluation of experimental data. Unfortunately, it is clear from the form of the typical isotherms, especially those for high polymers (large n) that, even with a simple model, this presents considerable difficulty. The problems can be seen clearly by consideration of some typical polymer adsorption data. Experimental isotherms for the adsorption of commercial polymer flocculants on a kaolin clay are shown in Figure 4. These data were obtained, in the usual way, by determination of residual polymer concentrations after equilibration with the solid. In general, such methods are limited at both extremes of the concentration scale. Serious errors arise at low concentration due to loss in precision of the analytical technique and at high concentration because the amount adsorbed is determined by the difference between two large numbers. 

Such displacement effects, although often very pronounced, have not yet been studied systematically. They will be the subject of the present paper. We will discuss the adsorption of polymer from a mixture of two solvents and we will see that in some cases drastic effects occur as a function of the mixture composition. Also, we explore some consequences and practical applications of displacement. It turns out that displacement studies not only increase our insight on the role of the solvent in polymer adsorption but can also be used to determine the segmental adsorption energy. So far, experimental data for this quantity were very scarce. Some illustrative experiments will be discussed briefly. 

In this paper we present results for a series of PEO fractions physically adsorbed on per-deutero polystyrene latex (PSL) in the plateau region of the adsorption isotherm. Hydro-dynamic and adsorption measurements have also been made on this system. Using a porous layer theory developed recently by Cohen Stuart (10) we have calculated the hydrodynamic thickness of these adsorbed polymers directly from the experimental density profiles. The results are then compared with model calculations based on density profiles obtained from the Scheutjens and Fleer (SF) layer model of polymer adsorption (11). 

Flocculation is indeed dependent on polymer adsorption, and there are hypotheses correlating the two phenomena, but often these have been put forth without detailed measurement of the two phenomena simultaneously (10-13). In this paper, flocculation is investigated as a function of polymer and solution properties and hydrodynamic conditions by measuring different properties of the system, including adsorption, using well characterized kaolinite and polymer samples prepared specifically for this purpose. Also, the role of concentration and charge density of polyacrylamide and polyacrylamide-polyacrylic acid co-polymers in determining kaolinite flocculation is examined under controlled hydrodynamic conditions. 

This paper contributes to the literature by quantifying anionic polymer adsorption onto the clay minerals kaolinite, feldspar, mica and quartz by X-ray photoelectron spectroscopy (XPS). XPS measures the sorbed amount directly rather than by a subtraction technique. This enables an insight into how effective selective flocculation is for obtaining kaolinite from a mineral mixture. Atomic force microscopy (AFM) is also used to image polymer adsorption onto mineral surfaces and the effectiveness of this technique applied to mineral surfaces is discussed here. 

Polymer adsorption has been reviewed by many authors28-37. An earlier volume of this journal presented an article which dealt with polymer adsorption studies made before 196429. This paper gives a review of subsequent advances in this field of study. In Chap. B, the principal theories are described, confining ourselves to those which are amenable to experimental teste. Chapter C gives a brief survey of typical measuring techniques. In Chap. D, important experimental data on the thickness of the adsorbed polymer layer and the fraction of adsorbed segments are summarized and discussed, along with their comparison with relevant theories. 

No attempt has been made to discuss the voluminous literature on molecular sieves or supported metals and the reader is referred to papers by Nacchace and Uytterhoeven (31) and Sheppard (32) respectively. IR studies on adsorption from solution are particularly relevant to polymer adsorption and have been reviewed by Rochester (33). 

This publication arranges the published papers on adsorption of polymers with special regard to experiment and theory. A summary of all investigated systems is given. The experimental methods are outlined and the amounts adsorbed are discussed as a function of the system and experimental parameters (polymer, adsorbent, solvent, molecular, concentration, time, weight and temperature). Calculated and experimental amounts of saturation, the number of contact points per molecule adsorbed, the thickness of the adsorbed layer, the adsorption isotherms, the heats of adsorption, the effects of desorption are compared. Assumptions on the structur of the adsorbed layer and the mechanism of polymer adsorption are made and discussed. 

A pervaporation system consists of equilibria at both sides of the membrane. One side of the membrane is in contact with the feed liquid mixture, while the other side is exposed to the permeate vapor at low pressure. It is considered that equilibria are established locally at both sides of the membrane. Adsorption equilibrium at the liquid-polymer interface must be established on the feed side, while an adsorption equilibrium at the vapor-polymer interface must be established on the permeate side. Further, both sides of the membrane are connected by liquid phase and gas phase diffusions of permeant molecules in the polymer. Therefore, adsorption equilibria at both liquid-polymer and vapor-polymer interfaces must be studied to fully discuss pervaporation phenomena. This aspect is neglected in many pervaporation papers. Although adsorption at the liquid-polymer interface can be studied by inverse phase liquid chromatography (20,21), this paper shows that adsorption at the vapor-polymer interface can be studied by IGC. 

Surface chains play a fimdamental role in the interaction processes (adsorption and adhesion) of the cellulose fibrils with other molecules. Such surface interactions play a key role in many areas of science biology (interaction with the plant cell-wall polymers, adsorption of cellulolytic enzymes), industrial (paper and textile industries), and technology (compatibilization and adhesion thermoplastic amorphous matrix on cellulose). Unfortunately, very little information has yet been gathered on the organization, conformation, and dynamics of the surface chains. In fact, few experimental... 

However, most explicit kinetic equations proposed in the literature are based on rather simple adsorption models which have no relevance for polymer adsorption. In this paper we will therefore first consider mass transfer-limited polymer adsorption and desorption rates from a theoretical point of view. We will then turn our attention to measurements which were designed in such a way as to enable accurate control over the mass transfer rate, so that data can be meaningfully analyzed. We used two different methods. The first is reflectometry combined with impinging-jet flow in order to measure adsorbed mass as a function of time.This... 

With nanometric particles the problem of polymer adsorption is different from the usual adsorption on macroscopic surfaces (Spalla O, Cabane B. Coll. Pol. ScL, in press). For one thing, nanometric dispersions have an extremely large surface area, hence they can adsorb a substantial amount of polymer before being saturated. In fact the amount of bound polymer is often comparable to the amount of particles in the system thus the system may be better described as a two-component system, similar in nature to mixed solutions of two polymers which interact with each other. This paper presents an analysis of such mixed particles+polymer dispersions from the point of view of two-component systems. 

It is not the primary objective of this paper to fully analyze the structure of the polymer layer on the solid surface. However, a few thoughts will be given about the role of salt and polymer concentration on polymer adsorption. 

Another paper presented at this meeting will discuss the aspects of polymer adsorption in field application (4). The fresh water requirement and the available disposal capacity did not impose operational bottlenecks because of the relatively small pore volumes of projects. 

Al-Sharji, H.H., Grattoni, C.A., Dawe, R.A., and Zimmerman, R.W. 2001. Disproportionate Permeability Reduction Due to Polymer Adsorption Entanglement. Paper SPE 68972 presented at the SPE European Formation Damage Conference, The Hague, 21-22 May. DPI 10.2118/68972-MS. 

Amro, M.M. 2008. Investigation of Polymer Adsorption on Rock Surface of High Saline Reservoirs. Paper SPE 120807 presented at the SPE Saudi Arabia Section Technical Symposium, Al-Khobar, Saudi Arabia, 10-12 May. 

Pmar, A.E. 1983. Effect of Polymer Adsorption on Mobility Ratio. Paper SPE 11503 presented at the Middle East Pil Technical Conference and Exhibition, Bahrain, 14-17 March. DPI 10.2118/11503-MS. 

Goddard, E. D. and R. Vincent (eds.), Polymer Adsorption and Dispersion Stability , ACS, Washington, DC, 1984. Papers are presented on the general topic of polymer adsorption and stabilization/destabilization. They include aqueous and nonaqueous systems, and natural and synthetic polymers. 

From the examples presented in this chapter papermaking suspensions are dearly fasdnating complex systems that show a richness of interesting phenomena. Both colloidal and hydrodynamic phenomena play a crudal role. The colloidal interactions can be modified, and thus optimized and controlled, by polymers and poly electrolytes. The time scales of polymer adsorption, partide deposition on fibers, particle detachment polymer transfer, flocculation and break-up of colloidal aggregates determine how a papermaking suspension behaves on a paper machine. These time scales can be controlled by dosage and addition points. Some of the relevant time scales can be predicted by theory, as some of the examples given here show, whereas others require experimental determination, such as polymer transfer rates, particle detachment and floe break-up rates, which are difficult to predict from first principles. Therefore, expensive pilot and mill trials are usually required to optimize and fine-tune the use of additives on a paper machine. Nevertheless, laboratory experiments can provide useful trends and help to eluddate the mechanisms by which additives function. 

Additives. Because of their versatility, imparted via chemical modification, the appHcations of ethyleneimine encompass the entire additive sector. The addition of PEI to PVC plastisols increases the adhesion of the coatings by selective adsorption at the substrate surface (410). PEI derivatives are also used as adhesion promoters in paper coating (411). The adducts formed from fatty alcohol epoxides and PEI are used as dispersants and emulsifiers (412). They are able to control the viscosity of dispersions, and thus faciHtate transport in pipe systems (413). Eatty acid derivatives of PEI are even able to control the viscosity of pigment dispersions (414). The high nitrogen content of PEIs has a flame-retardant effect. This property is used, in combination with phosphoms compounds, for providing wood panels (415), ceUulose (416), or polymer blends (417,418) with a flame-retardant finish. 

Adsorption of macromolecules has been widely investigated both theoretically [9—12] and experimentally [13 -17]. In this paper our purpose was to analyze the probable structures of polymeric stationary phases, so we shall not go into complicated mathematical models but instead consider the main features of the phenomenon. The current state of the art was comprehensively summarized by Fleer and Lyklema [18]. According to them, the reversible adsorption of macromolecules and the structure of adsorbed layers is governed by a subtle balance between energetic and entropic factors. For neutral polymers, the simplest situation, already four contributor factors must be distinguished ... 

In the following paper, the possibility of equilibration of the primarily adsorbed portions of polymer was analyzed [20]. The surface coupling constant (k0) was introduced to characterize the polymer-surface interaction. The constant k0 includes an electrostatic interaction term, thus being k0 > 1 for polyelectrolytes and k0 1 for neutral polymers. It was found that, theoretically, the adsorption characteristics do not depend on the equilibration processes for k0 > 1. In contrast, for neutral polymers (k0 < 1), the difference between the equilibrium and non-equilibrium modes could be considerable. As more polymer is adsorbed, excluded-volume effects will swell out the loops of the adsorbate, so that the mutual reorientation of the polymer chains occurs. 

It has been outlined by several authors that the single macromolecule may be irreversibly bound because of the large number of weakly interacting segments. The first papers on the construction of polymer-coated silica adsorbents involved the physical adsorption of water-soluble polymers. Polyethylene oxides [28, 29] and poly-/V-vinylpyrrolidone [30] are examples of the stationary phases of this type. 

According to the concepts, given in the paper [7], a significant difference between the values of yield stress of equiconcentrated dispersions of mono- and polydisperse polymers and the effect of molecular weight of monodisperse polymers on the value of yield stress is connected with the specific adsorption on the surface of filler particles of shorter molecules, so that for polydisperse polymers (irrespective of their average molecular weight) this is the layer of the same molecules. At the same time, upon a transition to a number of monodisperse polymers, properties of the adsorption layer become different. 

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