Polyacrylamide thermal stability

Synthetic polymers and natural polymers suitable for drilling muds are listed in Tables 1-7 and 1-8, respectively. Polyacrylamides are eventually hydrolyzed in the course of time and temperature. This leads to a lack of tolerance toward electrolyte contamination and to a rapid degradation inducing a loss of their properties. Modifications of polyacrylamide structures have been proposed to postpone their thermal stability to higher temperatures. Monomers such as AMPS or sulfonated styrene/maleic anhydride can be used to prevent acrylamide comonomer from hydrolysis [92]. 

Immobilized enzymes are becoming increasingly important in commercial processes. In this experiment, students will trap molecules of the enzyme horseradish peroxidase within a polyacrylamide gel matrix. The reaction kinetics and thermal stability of the immobilized enzyme will be measured. This experiment introduces students to the use of enzymes in biotechnology. 

PAn composites have been formed by polymerizing aniline in the presence of a latex.50 The latexes were chlorinated copolymers (Haloflex EP 252), which were film-forming latexes. Interestingly, the thermal stability of the resultant composite was better than either of the individual components. Polyaniline-polyacrylamide51 composites have been prepared by carrying out a chemical oxidation of aniline in the presence of polyacrylamide. Films that could be cast were stable up to 250°C. However, conductivities were low (approximately 5 x 10-2 S cm-1). 

This reaction seems to be specific for monomers containing amide groups (acrylamide or methacrylamide), but once these monomers are present in the electrolytic medium, other monomers, e. g., acrylonitrile, can be polymerized. The authors attribute the polymerization initiation to the electrogenerated metal ions only, but it is possible that even the perchlorate ion plays a role in the formation of the initiating species. The polyacrylamide thus obtained has an electrical conductivity 3 to 4 times higher than that of polymers obtained by the usual methods. This is due to the presence of metallic cations coordinatively bound in the polymer bulk. The presence of these cations increases the thermal stability of the polymer by 20—40%. 

Gamma irradiation of the highly miscible poly(vinyl al-cohol)/polyacrylamide blends up to 100 kGy has been show to increase the thermal stability of the blend [204]. 

The most widely used water-soluble polymer has been anionic polyacrylamide because it readily forms rigid hydrogels under these conditions and is relatively inexpensive. However, recent reports have shown that gels derived from polyacrylamide have limited thermal stability parti cularly when high concentrations of metal ions are present in solution. Specifically, these systems were unsuited to reservoir temperatures above 90 C. Others have indicated a somewhat lower (75 C) temperature for polyacrylamide. 

Arnold C (1979) Stability of high-temperature polymers. J Polym Sci Macromol Rev 14 265-378 Beyler CL, Hirschler MM (1995) Thermal decomposition of polymers. In DiNenno PJ (ed) The SFPE handbook of fire protection engineering (Chaps. 1-7), 2nd edn. NFPA, Quincy, MA, pp 110-131 Bhuiyan AL (1984) Some aspects of the thermal stability action of the structure in aliphatic polyamides and polyacrylamides. Polymer 25 1699-1710... 

The distribution of soluble arylsulphatases in human tissues has been examined via ion-exchange chromatography. All tissues contained arylsulphatase A and B. In addition, brain singularly contained significant quantities of a minor anionic form (Bm) only trace amounts of Bm were found in liver, kidney, testis, and placenta. Arylsulphatases B and Bm had equal activity towards methylumbelliferyl sulphate, nitrocatechol sulphate, and UDP-2-acetamido-2-deoxy-D-galactose 4-sulphate, but both forms were inactive toward the arylsulphatase A substrates cerebroside sulphate and L-ascorbic acid 2-sulphate. The physicochemical properties of arylsulphatases B and Bm differed with respect to thermal stability, ionicity, and behaviour on polyacrylamide gel electrophoresis and isoelectric focusing. 

The thermal stability of polymers (i.e., stability at higher temperatures) is a second important consideration. Laboratory tests indicate that the carbon/carbon backbone of polyacrylamides is stable in the absence of oxygen and divalent ions to temperatures up to 194°F. During incubation at high temperatures, however, polyacrylamides undergo hydrolysis by reaction of the amide groups with water. This is reflected in an increase in solution viscosity, as shown in Fig. 5.8. The behavior of xanthan polymers at elevat-... 

Muller, G.i Thermal Stability of High-Molecular-Weight Polyacrylamide Aqueous Solutions, Polymer Bull. (1981) 5, 31-37. 

Garcia et al. [98] conducted coulometric initiation of acrylamide polymerization in oil-continuous AOT-toluene-water microemulsions using platinum/Nafion solid polymer electrodes (SPEs). The SPE served to separate the microemulsion from an aqueous electrolyte phase. Polymerization was initiated at room temperature by constant-potential electrolytic reduction of potassium persulfate initiator solubilized in the microemulsion droplets. Acrylamide monomer behaved as a cosurfactant and was required for the redox process. Latex particles and solid polyacrylamide were obtained. The kinetics of electroinitiated polymerization was slower than observed with UV or thermal initiation. Latex stability results suggest that coalescence is the primary mechanism for particle growth. 

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