Poly (acrylic acid) [PAA]-based aircraft de-icing fluids are widely used commercially but are known to be subject to the formation of insoluble gel particles within wing structures. In this study, the rheological effects of the sodium chloride, potassium formate, and calcium acetate with commercially used PAA-based fluids are reported across the temperature range of −15 to 15 °C. Calcium ions have the potential to create gel particles, reflected in the shifts in the viscosity–temperature profile, while PAA aggregation is influenced by the concentrations and compositions of sodium and potassium salts in the water used for dilution. From the data presented, it is possible to create de-icing fluid formulations with the necessary rheological characteristics from stock solutions by dilution using available water sources, providing that the ion concentration is known.

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Titanium dioxide pigments will typically have an inorganic surface coating based on a blend of alumina and silica and an organic treatment. Both the organic and inorganic treatments can influence the cure characteristics of polyester powder coatings. This paper attempts to explore the connectivity between the nature of the coating and the cure behaviour of a typical heat cured epoxidised isocyanurate formulation. It is found that a high silica: alumina content in the inorganic pacification layer significantly retards the cure process, but is influenced by the nature of the organic treatment. The organic surface treatment may accelerate or retard the initial cure process and gelation times. Elemental analysis indicates that certain of the pigments studied have a significantly higher zirconium content and exhibited enhanced cure rates compared with those with the lower zirconium content. This paper illustrates the potential effects of different grades of titanium dioxide on the cure of polyester powder coatings. Keywords, polyester, trigylcidyl isocyanurate, cure data, thermally stimulated current measurements, dynamic mechanical thermal analysis.

The influence of epoxy resin formulation on the nature and extent of moisture is studied using dielectric and gravimetric analysis for samples cured at 40, 50, 60, and 70 °C and aged at 50 °C and 70 °C. The equilibrium moisture uptake depends on the difference between the glass transition and aging temperature. Dielectric relaxation data measured from 1 to 3 × 1010 Hz indicates the presence of water in at least two different environments. The high frequency relaxation ca. 1 × 1010 Hz is associated with water clustered in nano-voids, whereas the relaxation at 105 Hz arises from a combination of OH pendant group reorientation motion coupled with that of molecularly dispersed water molecules. A correlation exist between the dielectric permittivity and the amount of moisture absorbed. Water initially resident in voids is re-dispersed with aging into the resin matrix aiding plasticization and allowing densification of the matrix. The extent to which changes occur depends on the chemical functions forming the matrix and densification leads to a drop in the amount of water absorbed. In the complex resin systems, water interacts with both OH groups and polyether of the amine curing agent which is not possible with the aliphatic diamine in the simple system.] © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 133, 44717.

Dielectric techniques can be used as an in situ monitor of resin cure. This study reports measurements on two commercial resin formulations and aims to establish the extent to which identifiable turning points in the dielectric behaviour are dependent of the formulation used. Complementary curometer and differential scanning calorimetry data are used to monitor the progress of cure and are compared with the dielectric data. System [A] is a simple epoxy amine system, whilst system [B] is a blend of both epoxy and amine resins. It is clear that without calibration of the dielectric data against other methods it is difficult to unambiguously derive absolute cure information on a system not previously studied. However, dielectric data does allow identification of the points at which gelation and vitrification occur and demonstrates its utility as an in situ monitoring method for the cure process.

This paper describes the acoustic properties of a range of epoxy resins prepared by photocuring that are suitable for application in piezoelectric ultrasonic transducer matching layers. Materials, based on blends of digylcidyl ether of Bisphenol A and 1,4-cyclohexanedimethanol diglycidyl ether, are described. Furthermore, in order to vary the elastic character of the base resin, samples containing polymer microspheres or barium sulphate particles are also described. The acoustic properties of the materials are determined by a liquid coupled through transmission methodology, capable of determining the velocity and attenuation of longitudinal and shear waves propagating in an isotropic layer. Measured acoustic properties are reported which demonstrate materials with specific acoustic impedance varying in the range 0.88 6.25 MRayls. In the samples comprising blends of resin types, a linear variation in the acoustic velocities and density was observed. In the barium sulphate filled samples, acoustic impedance showed an approximately linear variation with composition, reflecting the dominance of the density variation. While such variations can be predicted by simple mixing laws, relaxation and scattering effects influence the attenuation in both the blended and filled resins. These phenomena are discussed with reference to dynamic mechanical thermal analysis and differential scanning calorimetry of the samples.  Author to whom correspondence should be addressed Richard O'Leary, Centre for Ultrasonic Engineering, University of Strathclyde, 204 George Street, Glasgow, G1 1XW r.oleary@eee.strath.ac.uk

A series of poly(ether imide)s are investigated using positron annihilation lifetime spectra [PALS] and gas permeation measurements. The glass transition temperature Tg, determined by differential scanning calorimetry, does not correlate with the void sizes calculated from density or determined by PALS, implying that in these materials polymer−polymer chain interactions and not free volume has a dominant role in determining the overall chain dynamics. Significant differences observed in the permeability process with respect to carbon dioxide and nitrogen, highlight the role of polar interactions between the diffusing gas molecule and the polymer matrix on the transport processes. Diffusion coefficients do not change in a simple manner with void size. The solubility parameters vary across the series of materials and produce a small variation in the solubility coefficients for nitrogen and argon, but significantly differences were observed for carbon dioxide, reflecting the influence of polar interactions plasticizing the matrix. This study indicates that whilst the void structure is important in influencing gas transport, chain–chain interactions are controlling many of the higher temperature physical properties of these polymers. High values of selectivity between carbon dioxide and nitrogen were observed indicating that these materials have potential applications as gas separation membranes. POLYM. ENG. SCI., 56:427–434, 2016. © 2016 Society of Plastics Engineers

Rheological and wind tunnels measurements are presented for mixtures of polymer polyacrylic acid [PAA] and polyvinylpyrrolidone [PVP] polymers dispersed in water-1,2 propylene glycol mixture to examine their use as potential aircraft de-icing fluids. PAA solutions which form the basis of de-icing fluids are known to result in undesirable gelation which may lead to undesirable and catastrophic consequences in such applications. In this study, we examine the blending of PVP with PAA blends as alternative de-icing fluid formulations that can reduce the likelihood of forming such irreversible gel deposits. Through adjustment of the electrolyte concentration, the ratio of PAA to PVP as well as the molecular weight of PVP, it is possible to achieve a required viscosity profile to that exhibited by a model de-icing fluid across a range of appropriate temperatures. Wind tunnel tests indicate that the mixtures are capable of meeting the necessary requirements for boundary layer depletion as well as having sufficient capability of retaining a stable layer required during aircraft taxiing.

Dielectric measurements are reported for alpha and gamma alumina powders exposed to moisture for various periods of time, temperatures and dried in air for various times. The observed behaviour reflects the nature of the surface oxide, topography of the oxide and is influenced by their ability to change as a consequence of thermal treatment. This study highlights the importance of the nature of the surface oxide on the processes of moisture penetration in aluminium bonded structures.

This review outlines some of the issues which have to be addressed when selecting an adhesive for a particular structural adhesive bonding application. The designer may find that a number of adhesives provide the required load bearing properties and the selection may require a more detailed consideration of the processes involved in the fabrication of the joint, the temperature over which it is to work and the environment in which it will have to operate. The article attempts to provide the reader with an insight into the effects of factors such as time and temperature used in the cure process, details of the components in the mixture and the effects of various additives on the physical properties of the adhesives which are created. The performance of an adhesive may vary with time as a consequence of stress-induced changes which are triggered by thermal effects or by hygrothermal factors. The review considers joints created using metal substrates and carbon fibre composites. The performance and durability of an adhesive bond is critically dependent on the stability of the interface between the adhesive and adherend and is sensitive to the pre-treatment processes used in the creation of the bond. The review outlines how broadband dielectric measurements can be used to non-destructively monitor the cure of adhesive bonds and the processes involved in ageing of joint. The dielectric method gives an insight into the fundamental processes which are giving rise to the changes in the mechanical properties of the joint as they age.

The effects of changing the ratio of 4,4'-diphenyl methane diisocyanate (MDI) to ester on the stress-strain extension characteristics of various polyurethane elastomers are reported. The data was analyzed using phenomenological theories appropriate to low, medium, and high extensions and the effect of non-Gaussian terms are considered. Analysis of the high extension data using the Morris theory provides elastic constants which are characteristics of the polyurethane networks. The values of theses constants are discussed in the context of the expected variations of the morphology in these polymers. (C) 2015 Society of Plastics Engineers

ABSTRACTBroadband dielectric relaxation spectra are reported on a range of poly(ether imide) polymers in which the chemical structure of the diamine used to create the polymer is systematically varied with the anhydride structure based on 2,2‐bis‐[4‐(3′,4′‐dicarboxyphenoxy)phenyl]hexafluoroisopropylidine dianhydride. In all the polymers examined, a dipole relaxation was observed below room temperature. The magnitude and activation energy associated with the relaxation process varied with the chemical structure reflecting the effects of steric hindrance on the conformational change associated with the NC and COC linkages. Values of the activation energies varied between 29 and 34 kJ/mol−1, and are consistent with the observed relaxation being associated with constrained local oscillatory motions of small elements of the polymer backbone. The glass transition temperatures of these polymers are in the range 195–243°C and are associated with the large scale motion of the polymer backbone. Changes in the backbone structure influence the extent of inter chain–chain interaction and are reflected in the amplitude of the relaxation process and the high frequency limiting dielectric permittivity ε∞ values which are important when these polymers are used in thin film electronic applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41684.

ABSTRACTThis article reports a study of four poly(ether imide)s with varying ethylene oxide (EO) segments lengths using positron annihilation lifetimes spectroscopy, wide angle X‐ray diffraction, and gas transport measurements. The measured properties change with the length of the EO segment. Comparison of the poly(ether imide) containing a single ether linkage with those containing one and three EO units, show progressive changes of the permeability and diffusion coefficient with void size. However, when six EO units are incorporated into the polymer backbone certain of the observed trends are reversed. Incorporation of flexible EO segments in the polymer backbone allows changes in the chain–chain interactions which increases the packing density and changes the void size and influences the solubility coefficients leading to variation of the gas transport characteristics. Differences in the measured solubility parameters reflect the extent to which the gases molecules are able to interact with the polymer matrix. The highest values obtained for the gas separation for carbon dioxide and nitrogen is observed when EO has a value of three. Further increasing of the length of the EO segments in the poly(ether imide) leads to a reduction the gas transport properties and hence the extent to which gas separation would be achieved. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1654–1662

Titanium dioxide pigments will typically have an inorganic surface coating based on a blend of alumina and silica and an organic treatment. Both the organic and inorganic treatments can influence the cure characteristics of polyester powder coatings. This paper attempts to explore the connectivity between the nature of the coating and the cure behavior of a typical heat-cured epoxidized isocyanurate formulation. It is found that a high silica:alumina content in the inorganic pacification layer significantly retards the cure process, but is influenced by the nature of the organic treatment. The organic surface treatment may accelerate or retard the initial cure process and gelation times. Elemental analysis indicates that some of the pigments studied have a significantly higher zirconium content and exhibited enhanced cure rates compared with those with the lower zirconium content. This paper illustrates the potential effects of different grades of titanium dioxide on the cure of polyester powder coatings.

In this study we consider the use of poly(vinyl pyrrolidone) (PVP) in conjunction with poly(acrylic acid) (PAA) as a thickener for water/glycol solutions. PAA in water/glycol formulations has wide application in the aviation industry for aircraft de-icing and prevention of ice build-up. Routinely sprayed onto the surface of wings and fuselage of aircraft in winter, they are designed to be retained on surfaces under zero shear and actively removed under high shear corresponding to take-off velocities. PAA deposited in aerodynamically quiet regions can produce gel deposits which have adverse effects on the performance of aircraft control systems. In this study we examine the rheological properties of solutions produced using a combination of PAA with PVP, with the aim of reducing the sensitivity of the solutions to added electrolytes. Various PVP–PAA formulations were examined rheologically and in a wind tunnel, across a range of sub-zero temperatures. The conclusions were that these blends can be used as alternative de-icing fluids. In these fluids, hydrogen bonding between the PVP and the PAA achieves the required level of polymer–polymer interactions to exhibit viscoplastic flow at lower electrolyte content. Gels which are formed are less stable that those formed with PAA alone.

ABSTRACTBroad band dielectric relaxation spectra are reported for some poly(ether imide)s based on 2,2‐bis[4′‐(3″,4″‐dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride and 1,2‐bis(4‐aminophenyl) diamines derived from ethylene glycol oligomers of different specific lengths. Spectra were obtained over the temperature range −150–−20 °C and which covers the low temperature relaxation region for these materials. In the case of the polymer with no EO units, a single broad dipole relaxation feature is observed. The introduction of a single CH2CH2O unit significantly broadens the relaxation suggesting the existence of two separate relaxation processes. Increasing the number of EO units per repeat to 3 and 6, allows resolution of two relaxations processes; one due to an oscillatory–librational motion of the imide segment and the other to conformational changes involving the EO sequences. Analysis of the relaxation using the Havriliak‐Negami equation indicates that both processes deviate for the description of a simple dipole relaxation and indicate cooperativity of bond motion in the relaxation process. The ability of a polymer to change its packing density is reflected in changes in the relaxation spectra on annealing and changes in the value of the higher frequency limiting values of the permittivity. The activation energy for dipole reorientation ranges from a value of 34 kJ mol−1 for the relaxation of the dipole associated with the imide relaxation process to a value of 60 kJ mol−1 for the polymer containing 3 EO segments. In this latter polymer, system a lower activation energy process is observed with a magnitude of ∼15 kJ mol−1 associated with conformational changes of the aliphatic ether. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1326–1336

This study of the behaviour of high-density polyethylene umbilical hoses subjected to constant and cyclic variation of pressure and temperatures attempts to simulate the temperatures and stresses experienced in offshore operations. The hoses are used to carry fluids to the top of the wellhead and provide protection for the electrical and optical controls systems. Measurements are reported for exposures at 40℃, 70℃ and 100℃ in water, methanol and xylene, using an applied pressure of 200 bar. The changes in the physical properties of the hose were monitored by measurement of the tensile properties, dynamic mechanical thermal analysis, differential scanning calorimetry and gravimetric uptake of the fluids. Significant changes occur immediately on application of pressure and reflect changes in crystallinity. The rates and extent of the modifications depend primarily on the ageing temperature but are also influenced by the fluid. Water has little effect on the rate at which ageing occurs, whereas xylene, which is a potential solvent for high-density polyethylene, exhibits characteristics of plasticization. Methanol behaves as a weak solvent and shows characteristics intermediate between xylene and water. Burst tests carried out on the aged material show that significant loss in strength is only observed with the highest temperatures and most aggressive solvent systems. The study indicates that engineers should use pressure-aged rather than initial materials data when designing umbilical hose systems.