Non-reactive Diluents Research Articles

Cationic photopolymerization of epoxynorbornane linseed oils: The effect of diluents

AbstractNew epoxynorbornane linseed oils (ENLOs) were prepared as a function of the norbornene content. The cationic photopolymerization of ENLOs was investigated with real‐time infrared spectroscopy and photo‐differential scanning calorimetry. The effects of reactive and nonreactive diluents on the polymerization rate were also studied. The diluents reduced the viscosity of the formulations, markedly accelerated the rate of polymerization of ENLOs, and increased their final conversions. The effects of the reactive diluent were compared for ENLOs and epoxidized linseed oil. The relative reactivity of the oxiranes was not as important as the viscosity of the reacting system, and it was proposed that the cationic photopolymerization of ENLOs was controlled by diffusion. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3440–3456, 2003

Rheological Properties of (Meth)acrylic Cross-Linked Polymer Microparticles, 2. Role of Interactions in Non-Reactive and in Reactive Diluents. Copolymerization Studies

The rheological properties of (meth)acrylic cross-linked polymer microparticle solutions have been studied regarding the influence of physical interactions. Cross-linked polymer microparticles (CPM) were synthesized with different functionalities: epoxy, acrylic, carboxyl, hydroxyl, octadecyl and methyl. The viscosities of either dilute or concentrated solutions in non-reactive solvent (xylene) and in reactive solvents (styrene and isobornyl acrylate monomer) have been measured for each type of CPM. A very weak effect of functionality was noticed on the intrinsic viscosity of CPM, whatever the solvent. Only carboxyl groups had a significant influence by increasing the viscosity because of hydrogen bonding. Greater effects were shown on the rheological properties of concentrated solutions. All solutions exhibited shear-thinning behavior when the solvent was xylene or styrene. Carboxyl functionalized CPM still led to higher viscosity, while octadecyl groups reduced the low shear limiting viscosity. The recovery time was strongly increased for CPM with epoxy and acrylic functionalities when styrene was used instead of xylene, whereas it remained the same for all other CPM solutions. In isobornyl acrylate monomer, only CPM functionalized epoxy and acrylic showed shear-thinning behavior, the other solutions being Newtonian. Finally a copolymerization study has been done on three solutions, containing either non-reactive CPM in reactive diluent, or reactive CPM in non-reactive diluent, or reactive CPM in reactive diluent. This study confirmed the cross-linking mechanism of acrylic systems. First, intramolecular reaction took place within the CPM and small aggregates were formed. Then these aggregates interconnected leading to a viscoelastic solid.

Fluorescence and IR Characterization of Cure in Polyurea, Polyurethane, and Polyurethane−Urea

Fluorescence and IR spectroscopic techniques have been used to characterize cure in polyurea (PUa), polyurethane (PU), and polyurethane−urea (PUU), based on the study of model compounds. Polyurea cured in a nonreactive diluent by reacting liquid MDI (4,4‘-methylenebisphenyl diisocyanate) with 3,5-diethyltoluene diamine (DETDA) showed fluorescence intensity decrease at 339 nm due to DETDA consumption and an emerging peak near 310 nm from the formation of the urea derivative of MDI. The reaction at room temperature was complete after 50 min with supporting IR evidence of urea carbonyl at 1642 cm-1. When nonfluorescent liquid MDI was reacted with ethylene oxide terminated PPO (EO−PPO) to form polyurethane, the fluorescence intensity at 310 nm increased slowly, taking approximately 1500 min to plateau with an intensity increase of at least 15 times. For PUU, which was cured by reacting MDI, EO−PPO, and DETDA, the fluorescence behavior was more complex: first, a peak at 303 nm showed up immediately following the mixing of the reactants, probably due to urea group formation, while the peak at 333 nm decreased due to DETDA consumption, and second, the peak intensity at 303 nm, after a slight decrease began to increase with a gradual shift to 310 nm. These results were correlated with the overall extent of cure as well as the extent of urea and urethane formation monitored by FTIR spectroscopy. Within certain regions, the fluorescence behavior can be correlated to the extent of urea and urethane reaction.

The influence of the molecular structure on the chemical resistivity of solventless and high-solid epoxy resins

The chemical resistance of solventless and high-solid epoxy compositions has been studied. The compositions have been cured at normal temperature and the chemical resistivity has been studied as a function of various resin types, solvent types and hardener types. The chemical resistance increases slightly with increasing epoxy equivalent weight. This is especially pronounced for this type of dependence relative to low molecular weight organic acids. The resistance of diluents to hydrolysis is more important than the reactivity of the diluent used. Also the capacity to swell plays an important role for a given solvent and resin system. The highest resistances have been determined for styrene as a reactive diluent and for 1,1-diphenylethane as the non-reactive diluent. The differences due to polyamine hardeners are decreased with the use of epoxy resin of higher epoxy equivalent weight.

Phase morphology of as‐molded and annealed blends of polyarylate/copolyester

AbstractThe phase morphology of injection molded blends of polyarylate (PAR) and a copolyester (PCTG‐5445) was studied by transmission electron microscopy (TEM) and X‐ray diffraction (XRD). The use of ultramicrotomy to prepare ⋍ 50 nm thin section TEM specimens and solvent etching to dissolve the PAR phase revealed PCTG as the matrix phase in the as‐molded state which crystallized into PCTG spherulites upon annealing. The most consistent morphological information vs. concentration of PCTG and the highest structural integrity of the PCTG spherulites was obtained from thin sections treated with a mixture of 75% methylene chloride as the solvent for the PAR and 25% 2‐propanol as the nonreactive diluent. XRD results from the annealed PCTG/PAR blends show crystalline reflections of 0.59, 0.53, 0.46, 0.38, and 0.35 nm, which disappear into the amorphous background below 50% PCTG.

Oligomerization and cyclization of 1‐phenoxy‐2,3‐epoxypropane induced by magnesium perchlorate

AbstractDuring the reaction of 1‐phenoxy‐2,3‐epoxypropane (1) with catalytic amounts of Mg(ClO4)2 a variety of reaction products are formed which do not correpond to a normally distributed oligomer range. Essentially, three reaction paths can be distinguished which lead to oligo‐(hydroxyether)s of similar structure (6 and 8) and to cyclic, isomeric dimers (9 and 10) of very low reactivity. During the reaction of bifunctional 2,3‐epoxypropyl ethers, cyclic products act as nonreactive diluents decreasing the network density of the final crosslinked product.

Effects of unequal reactivity of functional groups on gelation phenomena in polyurethane systems

A model to describe the effect of unequal reactivity on curing of a diisocyanate with water, polyol and a diol was developed. The model predicts whether a given initial composition would gel or not and the fractional conversions of functional groups at the gel point. It has been shown that the relative speeds of reaction of water and hydroxyl groups can be used to classify water's behaviour as that of a (i) nonreactive diluent (ii) monofunctional blocking agent and (iii) chain extender capable of connecting branch points.

Selection, Characterization, and Biodegradation of Surgical Epoxies

Abstract A series of epoxy resins has been formulated on the basis of obtaining low water sorption, low water vapor permeability, retention of electrical properties, and resistance to biodegradation by the body. These resins have been tested for these properties both by accelerated aging in 100°C water and in vivo studies. A literature survey was conducted on the biodegradation of surgical plastics with the findings that nylon lost 80% of its tensile strength after 3 years implantation while Orlon and Dacron deteriorated considerably less in a 2-year period. Teflon, Mastic, and Mylar showed almost no loss in tensile strength after 17 to 22 months. The epoxies tested on this program showed no loss in strength after 6 months in vivo. It appears that materials whose chemical structure contain bonds similar to those found in the body (such as amide groups) are susceptible to biodegradation whereas those such as Teflon which contain only C-C bonds or C-F bonds are not. Two general types of biodegradation can occur on polymers: Attack starting at the end of a polymer chain and proceeding along the chain to produce monomeric fragments (as in polypropylene), and attack at regular intervals along a polymer chain where susceptible cross-linking groups are present to produce macromolecular fragments. It has been postulated that attack on polymers takes place in the amorphous areas (if they are present) to leave the more crystalline areas of the material intact. Thus, with implantation, these types of materials become brittle. Histology on the developed epoxies indicated that epoxies containing nonreactive hydrophobic diluents showed a greater foreign body reaction than normal epoxies without such diluents.