Stability polymer

When polymers are used in oil recovery operations, it is clearly important that the polymer properties are not rapidly degraded. The main property of interest in this respect is generally the polymer solution viscosity although, for some polymers, the ability of the polymer to reduce the permeability of the reservoir formation may also be of some importance. Polymer degradation refers to any process that will break down the molecular structure of the macromolecule and the main degradation pathways of concern in oil recovery applications are as follows  

This section will simply present the findings of a number of key papers on polymer stability which have appeared mainly in the petroleum literature. No analysis of the mechanisms will be given in this section as this will be discussed for polyacrylamide and xanthan polymers later in this chapter. 

He did see considerable promise for polymers of HEC type and the biopolymers xanthan and scleroglucan were also found to be quite acceptable. However, Akstinat did not present very detailed stability results for the polymers in his study. Also, note that in the work of Akstinat, and in the work of Davison and Mentzer (1980), the objective was to find stable polymers for high-salinity brines (in the latter case based on sea water from the North Sea). It is well known, and it is discussed in detail below, that polyacrylamides are severely restricted in their performance in hard brines (i.e. brines containing divalent ions Ca , Mg ) (Zaitoun and Poitie, 1983 Moradi-Araghi and Doe, 1984). 

In a stability study involving five different polyacrylamides, one polyacrylate latex and two xanthans, Ryles (1983) found that the polyacrylamides were very stable for many months with or without the 

Another important aspect of Shape s work was that he studied combinations of additives for their effect on each other or on the stability of the HPAM under study. He noted the interaction between the oxygen scavenger, sodium hydrosulphite (Na2S204) and formaldehyde, which is frequently used as a biocide these substances interact to make the oxygen scavenger ineffective, and in combination they do not prevent degradation of the polyacrylamide. However, alternative biocides, such as glutaraldehyde, do not have this unfortunate effect. 

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Formaldehyde homopolymer is composed exclusively of repeating oxymethylene units and is described by the term poly oxymethylene (POM) [9002-81-7]. Commercially significant copolymers, for example [95327-43-8] have a minor fraction (typically less than 5 mol %) of alkyUdene or other units, derived from cycHc ethers or cycHc formals, distributed along the polymer chain. The occasional break in the oxymethylene sequences has significant ramifications for polymer stabilization. 

Additioaal uses for higher olefias iaclude the productioa of epoxides for subsequeat coaversioa iato surface-active ageats, alkylatioa of benzene to produce drag-flow reducers, alkylation of phenol to produce antioxidants, oligomeriza tion to produce synthetic waxes (qv), and the production of linear mercaptans for use in agricultural chemicals and polymer stabilizers. Aluminum alkyls can be produced from a-olefias either by direct hydroalumination or by transalkylation. In addition, a number of heavy olefin streams and olefin or paraffin streams have been sulfated or sulfonated and used in the leather (qv) iadustry. 

Although examples in the Kureha patent Hterature indicate latitude in selecting hold times for the low and high temperature polymerization periods, the highest molecular weight polymers seem to be obtained for long polymerization times. The addition of water to PPS polymerizations has been reported to effect polymer stabilization (49), to improve molecular weight (50,51), to cause or enhance the formation of a second Hquid phase in the reaction mixture (52), and to help reprecipitate PPS from NMP solution (51). It has also been reported that water can be added under pressure in the form of steam (53). 

Many antioxidants ia these classes are volatile to some extent at elevated temperatures and almost all antioxidants are readily extracted from their vulcanizates by the proper solvent. These disadvantages have become more pronounced as performance requirements for mbber products have been iacreased. Higher operating temperatures and the need for improved oxidation resistance under conditions of repeated extraction have accelerated the search for new techniques for polymer stabilization. Carpet backiag, seals, gaskets, and hose are some examples where high temperatures and/or solvent extraction can combine to deplete a mbber product of its antioxidant and thus lead to its oxidative deterioration faster (38,40). 

MURRAY, R. w.. Chapter entitled Prevention of Degradation by Ozone in Polymer Stabilization (Ed. HAWKINS, w. L.), Wiley, New York (1972)... 

The early recognition of the role of stable nitroxyl free radicals, e.g., 2,2,6,6-tetramethyl-4-oxopiperidine, and their hindered amine precursors, in polymer stabilization soon led to the development of the hindered amine light stabilizer (HALS) class of photoantioxidants. The first HALS, Tinuvin 770, AO-33, (commercialized in 1974) proved to offer much higher UV-stabil-ity to polymers than any conventional UV-stabilizer available at the time such as UV-absorbers, nickel compounds and benzoates. Table 3). 

Prior to the development of NMP, nitroxides were well known as inhibitors of polymerization (Section 5.3.1). They and various derivatives were (and still are) widely used in polymer stabilization. Both applications are based on the property of nitroxides to efficiently scavenge carbon-centered radicals by combining with them at near diffusion-controlled rates to form alkoxyamines. This property also saw nitroxides exploited as trapping agents to define initiation mechanisms (Section 3.5.2.4). 

Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) are also very useful tools for the characterization of polymers. TGA and DSC provide die information about polymer stability upon heating and thermal behaviors of polymers. Most of the polymers syndiesized via transition metal coupling are conjugated polymers. They are relatively stable upon heating and have higher Tgs. 

EB irradiation of polymeric materials leads to superior properties than the 7-ray-induced modification due to the latter having lower achievable dose rate than the former. Because of the lower dose rate, oxygen has an opportunity to diffuse into the polymer and react with the free radicals generated thus causing the greater amount of chain scissions. EB radiation is so rapid that there is insufficient time for any significant amount of oxygen to diffuse into the polymer. Stabilizers (antirads) reduce the dose-rate effect [74]. Their effectiveness depends on the abUity to survive irradiation and then to act as an antioxidant in the absence of radiation. 

The polymer stability upon storage was tested by keeping samples of pure, powdered poly(N-palmitoylhydroxyproline ester) in... 

Electro-optic materials can be made using liquid crystal polymer combinations. In these applications, termed polymer-stabilized liquid crystals [83,86], the hquid crystal is not removed after polymerization of the monomer and the resulting polymer network stabilizes the liquid crystal orientation. 

X represents the combined number of both types of units in the polymer chain. Eq. (3) applies also to polymers stabilized (see Chap. Ill) with small amounts of monofunctional units, although here it becomes necessary to replace the extent of reaction p with another quantity, namely, the probability that a given functional group has reacted with a bifunctional monomer. Type ii polymers stabilized with an excess of one or the other ingredient will be discussed later. 

A similar polymer-stabilized colloidal system is described by James and coworkers [66]. Rhodium colloids are obtained by reducing RhCls, 3H2O with ethanol in the presence of PVP. The monophasic hydrogenation of various substrates such as benzyl acetone and 4-propylphenol and benzene derivatives was performed under mild conditions (25 °C and 1 bar H2). The nanoparticles are poorly characterized and benzyl acetone is reduced with 50 TTO in 43 h. 

It is well known that the trimeric phosphonitri-lic chloride can be polymerized, at 200-300°C, to poly(dichlorophosphazene) (1), hereafter this polymer will be referred to as chloropolymer. Since this polymer contains hydrolytically-unstable chlorine groups, these groups are usually replaced with various alcohols, phenols, or amines to import the polymer stability. In our laboratories, the substitution is generally with alcohols or phenols. The reaction scheme is shown in Figure 1. 

Scheme 5. Covalent attachment to an amino-functionalized gel of pre-formed, polymer-stabilized metal (Rh, Pt) nanoparticles. (Reprinted from Ref. [33], 1991, with permission from the American chemical Society.)...

Formation of Missing Au SC via Thiolation of Polymer-Stabilized Gold Clusters... 

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