Resin Molecules Research Articles

Fluorescence based temperature measurements and applications to real‐time polymer processing

AbstractWe have used temperature sensitive fluorescent dyes, doped into polymer resins, to monitor the true resin temperature during extrusion processing. Two types of temperature sensitive fluorescent dyes were used: mobility dyes and fluorescence band definition dyes. When mixed with the resin at dopant concentrations, the fluorescent dye resides in a molecular neighborhood composed of resin molecules. Under these circumstances, its fluorescence spectrum reflects the resin temperature in its neighborhood. We apply this measurement concept to extrusion processing by using an optical sensor that accesses the machine at standard instrumentation ports. We show that, under processing conditions, the true resin temperature is significantly different from The machine temperature. Two examples of real‐time process monitoring arc presented: first, the effects of shear heating during extrusion were measured, and second, the effects of poor temperature control during extrusion were observed. The effects due to pressure on the fluorescence temperature measurements are examined. The fluorescence temperature measurements are compared to melt temperature thermocouple measurements.

Prediction of Asphaltene Precipitation for Kuwaiti Crude Using Thermodynamic Micellization Model

A thermodynamic micellization model is used in this work to describe asphaltene precipitation from Kuwaiti crude oil. The model is based on asphaltene and resin micelle formation and then destruction by addition of an alkane. A coin-like aggregate of asphaltene surrounded by resin molecules constitutes the micellar phase. The rest of the asphaltene and resin are dissolved in the bulk phase. A group contribution method was used to predict the critical properties for the asphaltenes, resin, and oil. The Peng−Robinson EOS was used to predict the onset point and to perform flash calculations. The onset point and the amount of asphaltene precipitated were measured. Hexane, heptane, octane, and decane with varying volumes and temperatures were used. The model also was tested using high-pressure data. In both cases, the model could describe the experimental data reasonably well with a mean square error of 0.57%.

MOLECULAR MECHANICS OF AGGREGATES OF ASPHALTENES AND RESINS OF THE ATHABASCA OIL

An analysis of the effects of an almost continuous chemical distribution of asphaltenes and resins on the molecular recognition processes occurring in crude oil indicates that their aggregates will have a broad distribution both in the chemical composition and in the strength of the intermolecular interactions responsible for the aggregation. Then, crude oil cannot be described just as a sol formed by solid asphaltene particles dispersed by resins or as a simple micellar system of asphaltene and resin molecules. The molecular aggregates may vary from solid particles formed by asphaltenes and resins to loosely bound micelles with quite short lifetimes. These different aggregates may coexist within the crude oil and many will exchange components with others. The entropic contributions to the changes in free energy upon aggregation were also discussed. Molecular mechanics calculations showed that a model asphaltene aggregate from Athabasca exhibits stronger interactions with its resins than with solvents such as toluene and n-octane. The resins showed a considerable selectivity for the different adsorption sites of the asphaltene aggregate. This selectivity was stronger than that found for the solvent molecules, indicating that it is enthalpically more favorable for them to form aggregates with the asphaltenes. The selectivity may also help to explain the specificity of some resins that are able to disperse only the asphaltenes of certain types of crude oils while failing to do the same for others.

Spectromechanical analysis of the structure and oxidation of PMR thermoset thermally-stable resins

The long-term ageing of high temperature polyimide thermoset polymers such as the commercial PMR15 resin and model molecules which compose the PMR15 chemical structure, was studied. The amount of each oligomer directly influences the physico-chemical and mechanical properties. The aim was to understand the oxidation mechanisms of these thermoset polyimide resins and the consequences for the mechanical properties. Nuclear magnetic resonance analysis has been associated with the thermo-mechanical transitions.

Waterborne unsaturated polyester resins

The transformation of solvent soluble unsaturated polyester resins into resins able to form stable water dispersion is presented in this paper. The methods of modification are discussed, consisting of the introduction of polar hydrophilic groups such as carboxylic and sulfonic ones (sodium 5-sulfonatoisophthalic acid) into the resin molecule, which ensure good tolerance with water. Instead of styrene, glycerol monoethers of allyl alcohol and unsaturated fatty alcohols were used as reactive built-in crosslinking monomers for resin modification. The influence of the resin composition and method of synthesis on the dispersion stability and properties of photocurable lacquer coatings obtained from the waterborne resins were investigated.

Molecular thermodynamics of asphaltene precipitation in reservoir fluids

AbstractA previously described molecular‐thermodynamic framework, based on colloid theory, is used to correlate experimental asphaltene‐precipitation data at high‐temperature and pressure conditions. In this framework, asphaltenes and resins are represented by pseudopure components, and all other components in a crude oil are presented by a continuous medium that affects van der Waals attractions among asphaltene and resin molecules. Model parameters are evaluated systematically from average properties of asphaltenes and resins in crude oils, and from dispersion‐force properties of the oil medium. Given the composition of the medium, and asphaltene and resin concentrations, the molecular‐thermodynamic model described here can be used to identify the onset of asphaltene precipitation, and the total amount of precipitation at the given operation conditions. Calculated results for the effects of oil composition and pressure on asphaltene precipitation are in good agreement with at least some experimental measurements for four reservoir fluids, including Texaco, Shell, Weyburn, and North‐Sea crude oils.

Thermal, mechanical, and morphological properties of phenolic resin/silica hybrid ceramers

Phenolic resin/silica hybrid ceramers were prepared through sol–gel technology. Differential scanning calorimetry and thermogravimetric analysis methods were utilized to study the thermal properties of the fabricated hybrid ceramers. The results showed that the heat resistance of the ceramers was slightly higher than that of the phenolic resin. The hydrogen bonding occurring inside the hybrid ceramers was investigated by Fourier transform infrared. The results showed that the intermolecular hydrogen bonding between the phenolic resin and the silica was stronger than the intramolecular hydrogen bonding between the phenolic resin molecules themselves. Furthermore, the hybrid ceramers were utilized to fabricate carbon-fiber-reinforced composites. The fabricated ceramer composites possessed better flexural strength and flexural modulus than that fabricated from neat phenolic resin. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1699–1706, 2000

Molecular Recognition in Aggregates Formed by Asphaltene and Resin Molecules from the Athabasca Oil Sand

The conformation of lowest energy of an asphaltene molecule of the Athabasca sand oil was calculated through molecular mechanics. The molecule has a complex globular shape with small internal cavities. This shape resulted mostly from the existence of polymethylene bridges connecting the aromatic regions. Molecular aggregates formed with the asphaltene and with nine resins from the same oil, and with n-octane and toluene, were also studied. The resins showed higher affinities for the asphaltene than toluene and n-octane and also exhibited a noticeable selectivity for some of the external sites of the asphaltene. This selectivity based on the molecular recognition of the site depends on the fit between the resins and the site of the asphaltene. The selectivity explains why resins of one oil may not solubilize asphaltenes from other crudes. An analysis of the changes in the enthalpic and entropic contributions to the free energy showed that both contributions should be considered when the stability of the as...

Properties of molding compounds to improve package reliability of SMDs

Package cracking during reflow soldering process is the great problem in the reliability of plastic packages. The technique of lowering the glass transition temperature (Tg) of a molding compound is very effective for improvement of the package cracking resistance because of the properties of low moisture absorption and high adhesion strength for a molding compound. But the package reliability except for the package cracking resistance is also important. In this study, the effects of the Tg for molding compounds on the package reliability was discussed. It was confirmed that decreasing the crosslinking density was an important factor to improve the package cracking resistance. There was no problem in thermal resistance, even if the molding compound has low Tg. However, decreasing the crosslinking density by the lowering of Tg may not satisfy humidity resistance in some cases. It was found to be important to decrease the crosslinking density of molding compounds without lowering Tg in order to improve both the package cracking resistance and the humidity resistance. It was also confirmed that the introduction of rigid structural segments into the matrix resin molecules of the molding compound was a useful technique for achieving excellent package reliability.

Film forming properties of asphaltenes and resins. A comparative Langmuir- Blodgett study of crude oils from North Sea, European continent and Venezuela

Asphaltenes and resins were separated from different crude oils, dissolved in different paraffinic and aromatic solvents and studied by means of Langmuir technique. It was found that the resin films are more compressible and more polar than the corresponding asphaltene films. Intermolecular aggregation between asphaltene molecules was more prominent than between resin molecules, and the size of the final aggregates depended on the nature of the solvent and the bulk concentration of the aggregating species. Even when present in smaller amounts than asphaltenes on the surface, the resins dominate the film properties.

Tack behaviours of p- t-octylphenol formaldehyde resin with rubber using a molecular simulation

Tack behaviours of p- t-octylphenol formaldehyde resin with rubbers, such as cis-1,4-polyisoprene and cis-1,4-polybutadiene, were studied using molecular mechanics and dynamics. The structures of p- t-octylphenol formaldehyde resin were found to be that hydroxyl groups cluster in the centre of the molecule by intramolecular hydrogen bondings and the t-octyl groups are extended out. The tack of p- t-octylphenol formaldehyde resin with rubber is formed by intermolecular non-bond interactions between the t-octyl groups of the resin and rubber chains. The interaction energies between one p- t-octylphenol formaldehyde resin molecule and two rubber molecules were calculated to investigate the effect of the molecular size of the resin on the tack strength. The interaction energies for the dimer and the trimer of p- t-octylphenol formaldehyde resin are greater than −20 kcal/mol while those for the tetramer–decamer are less than −40 kcal/mol.

Thermodynamic Model of Petroleum Fluids Containing Polydisperse Asphaltene Aggregates

New version of thermodynamic aggregation model of asphaltene-containing crude is formulated and analyzed with regard to characteristics of resin molecule shape and deformation of the resin shell of the asphaltene aggregates. The relation between the shape factors and elastic constants is discussed, and their effect on the size distribution of asphaltenic aggregates is considered. The model is applied to describe asphaltene precipitation from petroleum fluid upon its dilution with a liquid alkane. The effect of dilution on the asphaltene particle size distribution is studied. The model calculation has shown that the behavior of asphaltenic crude varies dramatically with the change of molecular characteristics of resins.

Thermodynamic Micellization Model for Asphaltene Aggregation and Precipitation in Petroleum Fluids

Summary A thermodynamic framework is proposed to describe the structure of asphaltene micelles and precipitation in crude. The asphaltene micelle is assumed to consist of an asphaltene core surrounded by a solvated shell. The shell contains both resin and all the other species except asphaltenes. The theoretical framework consists of the standard Gibbs free energy of micellar formation and the Gibbs free energies ofthe petroleum liquid and the precipitated phase. The standard Gibbs free energy of the micellar formation is modeled as the sum of various contributions including the association between asphaltene molecules in the core, the deformation of asphaltene and resin molecules in the micelle, and the adsorption of resin molecules onto the micellar core. The Gibbs free energy ofthe petroleum liquid phase includes the contributions from the standard state, mixing, and interactions among the species. The precipitated phase is assumed to be an ideal solid mixture of asphaltenes and resin. The direct minimization of the Gibbs free energy of the liquid/solid system is invoked to calculate the micellar structure and composition in crude and the amount and composition of the precipitated phase. The predicted results reveal that the addition of diluents n-C5 to n-C10 leads to asphaltene precipitation; whereas diluents such as C2 or C3 give rise to precipitation of nearly all resin and asphaltenes from crude. These predictions are in agreement with laboratory measurements. The predicted micellar size increases with dilution ratio. This prediction is also in agreement with measured data.

Location of crude oil resin molecules at an interface— model system

The location of resin molecules at an oil-water interface was investigated using low angle X-ray diffraction of lamellar liquid crystals as model systems. In general, the results revealed that resin molecules are located at the interface in contrast with the hydrocarbon molecules in crude oil and also that there is difference between the conditions at an interface with nonionic and ionic surfactants.

Food‐contact epoxy resin: Co‐variation between migration and degree of cross‐linking. Part II

The study of epoxy resin composed of bisphenol A diglycidylether (BADGE), bisphenol F diglycidylether (BFDGE) (base), and primary aliphatic polyamines (hardener), has confirmed the interest of measuring certain physical parameters in order to evaluate the density of cross‐linking of the network and thus predict the risks of resin molecules migrating into foodstuffs. This suggestion had been made in a preceding study on an epoxy resin composed of bisphenol A diglycidylether (BADGE) and primary aromatic poly amines. Samples with different densities of cross‐linking, obtained by subjecting the resin to different curing temperatures (5, 20, 50 and 90°C) for 7 days, were studied. The density of cross‐linking increased with curing temperature, as indicated by the increase in glass transition temperature, the increased stability of the rubber storage modulus E‘rub (increase in cross‐link nodes), the fall in relaxation enthalpies (reduction in physical ageing) and the decreased amplitude of the loss‐factor tan δ (reduction in chain mobility). Maximum crosslinking was obtained in the resin cured at 90°C (temperature above Tg8). Concurently, tests of migration into different liquid food simultants (distilled water, distilled water/ethanol/acetic acid, distilled water/ethanol) revealed a considerable reduction in specific migrations of BADGE and BFDGE, and of unidentified peaks.

Polymer-supported catalysts for efficient on-column preparation of 2-deoxy-2-[ 18F]fluoro-D-glucose

Several kinds of polymer-supported quaternary salts, such as dimethylaminopyridinium or tributylphosphonium salts, have been examined for the on-column preparation of [ 18F]FDG. Factors affecting [ 18F]fluoride trapping efficiency and [ 18F]fluorination yield have been optimized. [ 18F]Fluoride was practically, quantitatively trapped from flowing water and the subsequent 18F-substitution was carried out on-column with a radiochemical yield of over 70% (EOB). The improvement in the [ 18F]fluorination yield was achieved by introducing a spacer alkene chain between the supporting resin molecule and the catalytic site. A resin with higher cross-linkage and lower content of catalytic sites was shown to be useful for preventing column plugging.

Urea–formaldehyde (UF) adhesive resins for wood

Urea–formaldehyde (UF) resins are the most important type of adhesive resins for the production of wood based panels. They convince by their high reactivity and good performance in the production and by their low price, however they lack in water resistance of the hardened resin owing to the reversibility of the aminomethylene link and hence the susceptibility to hydrolysis. This need can be overcome by introducing other components like melamine to the UF resin molecules. The former problem of subsequent formaldehyde emission can be considered as solved owing to the decrease of the content of formaldehyde in the resins during the last two decades. Modern laboratory test methods enable a deep insight into the chemical structure and the gelling and hardening behaviour of the resins.

Curing reactions and modeling of silicone-carbon resins

New silicone-carbon resins have been made, based on four- or five-membered cyclosiloxanes, cyclopentadiene dimer (DCPD), and cyclopentadiene trimer (TCPD). The monomers are first polymerized to a B-stage resin, and then heated at higher temperatures to cure. In this work, the curing reaction of this silicone-carbon resin (which leads to network formation) is simulated using two approaches. In the first approach (stochastic model), all the available functional groups (olefin and silyl hydride) are allowed to react with each other with equal probability. This gives the kinetically controlled, liquidlike, diffusion-free limit. Extrapolation of the model to reactions where diffusion may play a role can be made by including molecular weight dependence in the rates. This dependence on the molecular weight can be scaled to fit the experimental data. In the second approach a percolation model is used. In the extreme case, this model corresponds to the solid-state reaction between silicone-carbon resin molecules on 2-dimensional or 3-dimensional rigid lattices. Relaxation of this geometric constraint can be made by providing a larger reacting distance between the reactants. Computer programs have been written for 2- and 3-dimensional lattices. Illustrative examples are given for these approaches. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1557–1573, 1997

Water sorption and solubility of glass fiber-reinforced denture polymethyl methacrylate resin

Polymethyl methacrylate (PMMA) absorbs water slowly over a period of time, primarily because of the polar properties of the resin molecules. The aim of this study was to determine the water sorption and solubility of heat-cured and chemical-cured glass fiber (GF) PMMA composite used in dentures. The test specimens ( n = 5) were fabricated from experimental, unidirectional, continuous GF reinforcement; the GF concentration of the test specimens was approximately 11% by weight. Water sorption and solubility were tested in accordance with International Standards Organization specification No. 1567. The results revealed that the type of acrylate had more of an effect on water sorption than did the presence of GF reinforcement in the test specimen ( p = 0.001 and p = 0.049, respectively). In the GF-reinforced test specimens the type of PMMA also affected the water sorption values ( p = 0.006). GF reinforcement affected the solubility values of the test specimen ( p = 0.002), but the type of acrylate had no effect on solubility ( p = 0.585). The results of this study suggest that the water sorption and solubility of unreinforced PMMA and PMMA reinforced with GF are in accordance with International Standards Organization specification No. 1567. (J Prosthet Dent 1996;76:531-4.)

Solvent vapour lock: an extreme case of the problems caused by lignified and suberized cell walls during resin infiltration

To determine the cause of floating tissue pieces and poor resin infiltration, sugarcane stem tissue was monitored during processing for microscopy. Bubbles formed within cells at the early stages of solvent replacement (the timing dependent on the fixation used), and increased in volume to fill the cells as resin concentration increased. It is concluded that bubbles form by solvent cavitation (formation of a solvent vapour phase) as hydraulic pressure decreases within the cells, because the thick, lignified and suberized walls are freely permeable to the solvent but not to the resin molecules. The pressure difference across the walls that would be required to release the vapour lock cannot be achieved by vacuum infiltration. In more flexible, thinner‐walled, suberized and lignified tissues in maize roots, the lowering of hydrostatic pressure in the cells results in distortion by cytorrhysis (cell collapse). The analogy is drawn between the cavitation and cytorrhysis of cells during resin infiltration and the same processes which occur in living plant cells during water stress. Cavitation and cytorrhysis did not occur in sugarcane or maize tissues processed by anhydrous freeze substitution.