SynopsisThe yradiation-induced free-radical copolymerization of ethylene and CO has been investigated over a wide range of pressure, initial gas composition, radiation intensity, and temperature. At 2O"C., concentrations of CO up to 1% retard the polymerization of ethylene. Above this concentration the rate reaches a maximum between 27.5 and 39.2% CO and then decreases. The copolymer composition increases only from 40 to 50% CO when the gas mixture is varied from 5 to 90% CO. A relatively constant reactivity ratio is obtained a t 20°C., indicating that CO adds 23.6 times as fast as an ethylene monomer to an ethylene free-radical chain end. For a 50% CO gas mixture, the above value of 23.6 and the copolymerization rate decrease with increasing temperature to 200°C. The kinetic data indicate a temperature-dependent depropagation reaction. Infrared examination of copolymers indicates a polyketone structure containing -CH-CHand -COunits. The crystalline melting point increases rapidly from 111 to 242"C., as the CO concentration in the ,copolymer increases from 27 to 50%. Molecular weight of copolymer formed a t 20°C. increased with increasing CO, indicating a,, values >20,000. Increasing reaction temperature results in decreasing molecular weight. Onset of decomposition for a 50% CO copolymer was measured at -250OC.
A study has been performed to determine the effect of the use of divinyl benzene(DVB) as a crosslinking agent in polymeric binders consisting of mixtures of styrene, acrylonitrile, and acrylamide, on the thermal stability and structure of polymer concretes(PC), containing sand and cement as an aggregate. The results indicate that the inclusion of DVB results in improvements in the thermal and mechanical stability. The improvements are attributed to three‐dimensional cross‐linking of the polymer due to the inclusion of DVB. The influence of the sand‐cement ratio on the structure of PC samples at 240°C are also discussed.
The radiation‐induced copolymerization of ethylene and sulfur dioxide has been studied in the liquid and gas phases. In the liquid phase, the copolymer composition remained equimolar over a temperature range of 20–160°C. and ethylene pressures of 50–680 atm. The rate of copolymerization in the liquid phase at 680 atm. increased with temperature to a maximum value at ∼80°C. Above this temperature the rate steadily decreased to zero at 157°C. because of temperature‐dependent depropagation reactions. In the gas phase, copolymers were formed that contained from 9 to 46 mole‐% sulfur dioxide. Under constant conditions of temperature, pressure, and radiation intensity, the copolymerization rate in the gas phase increased with increasing sulfur dioxide in the initial gas mixture. The propagating species for the liquid‐phase experiments is considered to consist of an equimolar complex molecule of ethylene and sulfur dioxide. For gas mixtures containing an excess molar concentration of ethylene, the propagating species are ethylene and the complex molecule. Infrared spectra show polysulfone structures. Calorimetric and x‐ray diffraction analyses indicate crystalline structures for copolymers in the range 9–50 mole‐% sulfur dioxide, although a melt transition temperature could not be observed for copolymer containing >31 mole‐% sulfur dioxide. Clear uniform film was obtained with copolymers containing up to 31 mole‐% SO2.
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