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The radiation-induced gelation of two monomers, acrylic acid and acrylamide, crosslinked using four model compounds was investigated using Fourier transform mechanical spectroscopy. The gel point characteristics of the resulting hydrogels were compared. The gelation characteristics of the two monomers were very similar. The fractal dimensions of the critical gels ranged between 1.77 and 1.82 when the reactions were controlled. The patterns of viscoelastic events of the products at the gel point were also similar, with the matching reactivity of the monomers and the comparable molecular weight of the crosslinkable species, providing a foundation for such events. All of the reactions exhibited low mutation numbers, indicating that the samples tested were quasi-stable during the measurements. The extent of the UV irradiance during crosslinking reactions is an important parameter in the gelation process, with an increase in UV irradiance decreasing the gel times, decreasing the network relaxation exponents (increased fractal dimensions), leading to stiffer critical gels. The evolution of δ with G*, undertaken as van Gurp–Palmen plots, shows that in the fully formed gels, however, the monomer choice and the crosslinker variation can dictate the viscoelasticity of the materials. In particular, the potential for greater steric effects/greater stabilities of the radical active centres of the dimethacrylate species, in comparison with the diacrylate species, resulting in lesser viscoelasticities in the fully formed gels.

Viscosity is one of the key factors which influence the application of polyacrylamide (PAM) in enhanced oil recovery (EOR). In this study, we have demonstrated the viscosity reduction of PAM solution by using carbon quantum dots (CQDs) through rheological, spectroscopic and thermal analyses. The stability of PAM, CQDs, and PAM/CQDs composites, and the chemical interactions between PAM and CQDs were investigated. The addition of CQDs into PAM solution decreased its viscosity, demonstrating a phenomenon which contradicts the expression normally derived from the Einstein–Batchelor law for the viscosity of particle suspensions. Consequently, the elastic properties of PAM/CQDs composites were lower than those of the pure PAM solutions. Moreover, the presence of CQDs in the PAM increased its flow activation energy and decreased its yield point, leading to an increased sensitivity to both temperature and shear rate. The mechanism behind the reduced viscosity behaviour of PAM/CQDs composites appears to be the formation of free radicals and the elimination of ammonia molecules, leading to the deterioration of the polymer backbone.

In this chapter, the application, relevance, and mechanisms associated with the use of nanocomposites in enhanced oil recovery (EOR) are considered. Nano-EOR is a process that is typically employed when producing oil from conventional EOR techniques has been exhausted. The process involves the addition of nanoparticles (NPs) to chemical-based fluids, to improve the EOR performance. NPs dispersed in a polymer matrix—known as polymer nanocomposites—are a rising class of materials that may be preferable for EOR than pure NPs due to their improved rheological properties, better stabilization of emulsions and forms, improved stability and solubility, and more facile transport through porous media. A brief account of EOR, including its various classifications, is given. A review of the prior research, current challenges, and future research opportunities in the application of polymer nanocomposites for EOR is provided. Attention is given to studies of polymer nanocomposites for improving mobility control, interfacial tension (IFT) reduction, changing surface wettability, and for studies on their transport behavior through rocks and porous media. The mechanism that is based on viscosity increase appears to be the most acceptable mechanism in polymer nano-EOR. The use of general nanofluids and surfactant blends is also considered. The advantages and disadvantages of the use of nanofluids in chemical EOR applications are highlighted. A number of points are highlighted to allow some of the disadvantages to be manipulated/enhanced/resolved into positive effects. Finally, a summary of the field’s major challenges, which must be addressed to successfully implement polymer nanocomposites in EOR applications, is provided.

In this chapter, the science, technology and applications of functional hydrogels are considered. A brief discussion on fundamental network properties, such as fractal dimensions, network relaxation and stiffness, are given. A large number of synthesis approaches for the manufacture of functional hydrogels are discussed here. The key synthesis approaches which underpin a series of hydrogel variants and their applications are also discussed. An overview of the composition, structure, functionality, characterization and application of a range of functional hydrogels is offered in this chapter, as well as relevant rheological approaches in the synthesis and characterization of these materials are discussed here, paying particular attention to the gelation, sol-gel transitions and multiwave mechanical spectroscopy.

Aspects of melamine migration from epoxy-based coatings into a food simulant were studied. Four commercial amino-based cross linkers were incorporated into an epoxy anhydride coating system and into an epoxy phenolic coating system. The epoxy-based coatings were formulated, applied, cured and tested for migration by retorting in contact with the food simulant, 10% ethanol, at 131°C. The commercial melamino-based cross linkers used and the model coatings that were prepared using these cross linkers contained very low or non-detectable levels of free melamine. However, during retorting, the migration of melamine from the coatings increased as the retorting time was increased. This migration process is not the more classical diffusional process but rather the result of chemical attack (hydrolysis) of the coating. For these model can coatings, a substantial fraction of the melamino cross linker was hydrolysed although, curiously, the essential functional properties of the coating are retained. In all cases, for these model systems the migration of melamine was rather low because the cross linkers are used commercially in only small amounts - typically 1-2% of the dry film weight of the coatings. For the standard retorting conditions of 1 h, migration of melamine was up to 0.4 mg kg(-1), depending on the cross linker used. The cross linker that contained the methylol functionality (-CH₂OH group) gave rise to less melamine than did the alkylated cross linkers (methylated and butylated, -OCHv and -O(CH₂)₃CH₃, respectively). This observation could prove useful in formulating coatings with even lower melamine release characteristics.

In this study, the suitability of four chemically different melamino cross-linkers for use in formulating epoxy coatings was investigated on the basis of the composition and of the tendency of cured coatings to hydrolyse to melamine and to formaldehyde when they were retorted in aqueous food simulants. The four cross-linkers were characterised for their composition identity, flow behaviour, thermal stability and for the presence of residual species. The different cross-linkers were used individually to cross-link selected epoxy coatings. The effects of the cross-linker chemistry, the curing conditions and the kinetics of the hydrolysis and subsequent migration processes, leading to melamine and formaldehyde were investigated following thermal treatments that were designed to represent the conditions of food sterilisation. The results show that each cross-linker type is different in its rheological characteristics, its solids content, its thermal behaviour and its physical properties. The chemistry of each cross-linker plays a major role in the manner in which the epoxy coatings undergo hydrolysis to release melamine and formaldehyde. The greatest migration of melamine (from an unpigmented epoxy anhydride coating, cured with the hexamethoxymethyl melamine cross-linker) into the 10% (v/v) aqueous ethanol food stimulant, after retorting at 131 °C, for 1 h was 525 μg/6 dm 2 . The greatest migration of formaldehyde into the simulant was also from this coating at 11 μg/6 dm 2 , when retorted at 131 °C for 1 h. The curing conditions affected the extent of the cross-linker hydrolysis. The influence of varying the curing time and the curing temperature was used to control the hydrolysis of the cross-linked, epoxy-based coatings. A decrease in the extent of cross-linker hydrolysis by 50–80% was achieved in all cases as the temperature of the curing was increased, in stages, from 160 °C to 200 °C.

This review focuses on organometallic surfactant frameworks considering their wide applications. Organometallic surfactants have grown from being used as dewaxers in complex industrial processes to the production of nanoparticles and for use in many drug delivery applications. Their properties such as self assembly, forming supramolecular structures are outstanding, providing for their myriad industrial usage. In this review, an account of properties, preparation techniques, characterisation techniques and uses of organometallic surfactants are covered.

Pigmented (TiO2), amino resin crosslinked coatings, designed for applications in can coatings’ internal lacquers, were formulated, characterized, applied, and cured. Three grades of a pigmentary form of TiO2 were characterized in terms of their particle size, their particle morphology, their zeta potential, and their moisture retention behavior. Epoxy coatings that were crosslinked using one of several, different amino crosslinkers were prepared. The effect of the presence of the TiO2 pigments on the hydrolysis of the cured coatings was monitored via the controlled retorting of the coatings. The different grades of TiO2 pigment were selected, to establish whether or not they could be used interchangeably with respect to hydrolysis and to melamine release. Also, the effects of the aging of the fluid coatings on the amount of melamine released from the coatings (after curing and retorting) were monitored. Storage under laboratory conditions for 2, 20, and 40 weeks was used for this purpose. The TiO2 pigment contributed significantly to the hydrolysis behavior of the epoxy coatings in that their presence substantially reduced the amount of melamine released and the extent of crosslinker hydrolysis. Typical results show that excluding the TiO2 pigment particles from the formulation results in there being 50% more hydrolysis of the crosslinker to melamine. With respect to the melamine release and crosslinker hydrolysis, the different grades of the pigment gave similar results.

In recent times, hyperuricaemia has been widely diagnosed in individuals due to changes in lifestyle and as a result of disease conditions that lead to elevated levels of uric acid in the blood. Our present work is on determination of the levels of uric acid in healthy individuals and patients with type 2 diabetes mellitus. Prevalence of hyperuricaemia in relation to age, gender and disease condition was monitored. The results indicated that, levels of uric acid are much higher in subjects that have a combined case of hyperuricaemia and type 2 diabetes mellitus.

This study was aimed at understanding any effects that the presence of acrylic acid dimer could have on thermo-mechanical properties of acrylic acid-based hydrogels. Polymeric hydrogels were systematically synthesised and characterised on the basis of having different concentrations of acrylic acid dimer. The materials show a reversible thermo-responsive behaviour, when heated in situ using light transmittance approaches. The point of cloudiness is significantly influenced as a consequence of the presence of the acrylic acid dimer material. Increasing the amount of the dimer additive up to 2% improves the light transmittance (%) of the soft gels by up to 70%, at 140°C, suggesting that a potential method of altering the lower critical solution temperature of the soft gels is to alter the polymer backbone through copolymerization. As the amount of dimer was increased up to 2%, the values of storage modulus (G') were increased by up to 75%, leading to greater viscoelasticity and stronger gel compositions.