Free-radical retrograde precipitation-polymerization process

A free-radical retrograde polymerization process for forming a polymer. An admixture of reactants including predetermined amounts of a monomer, a solvent, and a free-radical-initiator is reacted. A precipitation polymerization reaction occurs such that a polymer-rich phase is at a temperature generally above the lower critical solution temperature (LCST) of the admixture.https://digitalcommons.mtu.edu/patents/1079/thumbnail.jp

Properties of Transfer-Molded Wood-Fiber/Polystyrene Composites

Transfer-molded composites combining polystyrene, wood particles, and three bi-functional coupling agents were prepared and evaluated for physical and mechanical properties. Pure 685D polystyrene (PS) (75-100% by weight) was combined with 100-mesh (0.15-mm sieve opening) particles prepared from thermomechanically pulped quaking aspen (Populus tremuloides) (0-25% by weight). Three coupling agents, polystyrene/poly(methacrylic) (both low and high molecular weight) and polystyrene/poly(vinyl acetate) developed at Michigan Technological University, were added in an effort to promote compatibility between the hygroscopic wood fiber and the non-polar hydrophobic polystyrene. Mechanical tensile testing was used to assess the respective composite's tensile elastic modulus and tensile strength. A polystyrene/poly(methacrylic) acid (PS-PMAA) coupling agent was found to be the most effective with regard to enhanced tensile elastic modulus at higher fiber-loading levels (enhancement levels of 11.3-23.8% over pure PS). A fiber/PS composite using low molecular weight PMAA (PS-PMAAL) as a coupling agent demonstrated the best tensile strength retention characteristics at higher fiber-loading levels. Initial results show high variability in material properties over the range of fiber-loading levels, and between coupling agent type. It is clear, however, that certain coupling agents do have a positive effect on composite properties

Analysis of polymer membrane formation through spinodal decomposition

A phenomenological model used in a previous work for spinodal decomposition of polymer‐solvent systems is further analyzed. From the dimensionless form of the nonlinear Cahn‐Hilliard equation, the dimensionless induction time is found to be a constant number for suddenly quenched systems. Computer simulation is carried out for prediction of early stage behavior with thermal history corresponding to a linear temperature drop followed by a constant temperature vs. time. In the areas of polymer membrane formation and phase separation studies, the universality of the constant dimensionless Induction time for suddenly quenched systems allows the determination of the minimum time needed for phase separation via spinodal decomposition. Also, simulation results for the double linear temperature history allows the convenient prediction of early stage spinodal decomposition behavior at every point of a membrane cross section undergoing thermal inversion phase separation

Free-radical retrograde-precipitation polymerization (FRRPP): Novel concepts, processes, materials, and energy aspects

The book pertains to unique phenomenological features of a potentially runaway polymerization reaction process that is apparently brought under control through a mass and energy confining mechanism. It integrates the combination of various concepts in order to explain a collection of experimental observations, which includes entrapment of reactive intermediates as well as their energy contents, nucleated thermal hot spots beyond adiabatic rise temperatures, and nanoscale confinement behavior that has been used for fine patterning of polymers. Toward the end, the author of the book will try to use whatever understanding that has been formulated about the Free-Radical Retrograde-Precipitation Polymerization (FRRPP) process to relate it to various materials including environmentally-reponsible and energy-relevant types, and inherent control of energetic systems

Analysis of polymer membrane formation through spinodal decomposition. Part 4: Computer simulation of early-stage coarsening

In a previous work, an early-stage coarsening mechanism was proposed, whereby continued growth of structure (via spinodal decomposition) in a polymer-solvent system will occur because some of the polymer-rich domains are being depleted. Such a mechanism was explained based on the situation wherein portions of the solvent-rich domains have already reached their binodal composition while the polymer-rich domains are still on their way to their corresponding binodal composition. In this work, we have simulated the nonlinear version of the Cahn-Hilliard theory to verify this phenomenon. Moreover, we have observed that the depleted polymer-rich domains seem to be uniformly distributed in space. Finally, as a validation of the proposed mechanism, we did not observe this uniform depletion of the domains when portions of the solvent-rich and polymer-rich domains reach their respective binodal compositions almost simultaneously

PS–PMMA Block copolymer system as compatibilizer for PS–PVC blends

We are studying the use of PS–PMMA block copolymer systems to improve the mechanical properties of immiscible PS–PVC blends. For a particular PS–PMMA block copolymer system, we found that effective compatibilization occurs at compatibilizer levels of 1–5 wt % in a 50/50 PS–PVC blend. In the samples, storage and stress relaxation moduli were at least midway between those of pure PS and PVC. On the other hand, the equivalent uncompatibilized blend exhibited storage and stress relaxation moduli that are much lower than those of the soft PVC component. Stress relaxation moduli of pure PS remained fairly constant with time, while a 25% drop was observed for pure PVC after 120 sec. Also after 120 s, stress relaxation moduli for the uncompatibilized blend exhibited a 20% drop, while a less than 10% drop was observed for the compatibilized PS–PVC blends

Kinetic study of Ru III -catalyzed polymerization of methylmethacrylate initiated with n-butylamine in the presence of carbon tetrachloride by a charge-transfer mechanism

Ruthenium trichloride (RuCl3 or RuIII) catalyzed polymerization of methylmethacrylate (MMA) initiated with n-butylamine (BA) in the presence of carbon tetrachloride (CCl4) by a charge-transfer mechanism has been investigated in a dimethylsulfoxide (DMSO) medium by employing a dilatometric technique at 60°C. The rate of polymerization (Rp) has been obtained under the conditions [CCl4]/[BA] ≤ 1 and [CCl4]/[BA] ≥ 1. The kinetic data indicate the possible participation of the charge-transfer complex formed between the amine-Ru III complex and CCl4 in the polymerization of MMA. In the absence of either CCl4 or BA, no polymerization of MMA is observed under the present experimental conditions. The rate of polymerization is inhibited by hydroquinone, suggesting a free-radical initiation

Transport phenomena aspects of the free-radical retrograde-precipitation polymerization (FRRPP) process

We have been studying free-radical polymerization that is accompanied by phase separation above the lower critical solution temperature. In the past, we have experimentally shown evidence of hot regions in the reactive system. We have also shown in the past that eventually the system exerts control over the rate of propagation as well as termination. In this work, we invoke a concept in polymer physics (the coil-to-globule transition) to help explain the mechanism of thermal trapping within the polymerization zones. The diffusivities of polymer chains at different stages in the reaction are calculated using appropriate methods. From the diffusivities, the propagation and termination rate coefficients are calculated using the Achilias-Kiparissides gel effect model. With experimental kinetic data, we then estimate rates of monomer consumption within polymer-rich particles. Using a pseudo-steadystate heat transfer model, we are able to show that interior temperatures of polymer-rich particle domains greater than about 1 mm can reach spinodal temperature values at the early stage of polymerization. Polymer-rich particle sizes are obtained from the same reactor system whereby a small amount of crosslinker is added to preserve particle morphology. This experiment indicates that even under turbulent flow conditions, relatively large particles can exist in the reactor fluid. This agrees with the physical implications of the coil-to-globule transition. However, since these particles were obtained during the period of slow conversion rate, our heat transfer calculations indicate that interior particle temperatures would be almost the same as surface temperatures. This points to an unknown radical-trapping mechanism at this stage of the polymerization process