Browsing by Author "RIVAS, BL"

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    SYNTHESIS AND CHARACTERIZATION OF COPOLYMERS FROM ACRYLIC AND METHACRYLIC-ACID WITH 2-METHYLAZIRIDINE BY SPONTANEOUS COPOLYMERIZATION
    (1995) RIVAS, BL; PIZARRO, GD; TAGLE, LH; RADIC, D
    2-Methylaziridine (MAz) as a nucleophilic monomer and acrylic acid (AA) and methacrylic acid (MA), respectively, as electrophilic monomers were copolymerized in the absence of initiator at various feed ratios. Copolymers were characterized by elemental analysis, FT-IR and H-1-NMR spectroscopy. The monomer reactivity ratios were determined by the Fineman-Ross and Kelen-Tudos methods. Values of r(1) and r(2) were found to be less than unity for MAz-AA, and MAz-MA, corresponding to random copolymers with the tendency to the alternance. For all the copolymers the thermal decomposition with 10% weight loss is higher than 430 K. The reaction order for degradation of all copolymers was zero. The kinetic parameters of the decomposition were determined for all copolymers.
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    THERMAL-DEGRADATION AND DETERMINATION OF KINETIC-PARAMETERS BY DYNAMIC THERMOGRAVIMETRY OF COPOLYMERS SYNTHESIZED WITHOUT INITIATOR
    (1991) RIVAS, BL; PIZARRO, GD; CATALAN, RE; TAGLE, LH
    The thermal degradation of a series of 18 copolymers of 2-methylaziridine and 1-(2-hydroxyethyl)aziridine with N-phenylmaleimide and derivatives obtained without added catalyst, was investigated using thermogravimetry (TGA) under a dynamic nitrogen atmosphere over a temperature range from 20 to 500-degrees-C. Almost all the copolymers degrade in one step. The kinetic parameters E(a), n and A were obtained following one method of thermogravimetric analysis. The thermal stability depends on the copolymer composition which was determined from the H-1 NMR spectra. The most stable material was poly(p-nitrophenylmaleimide-co-2-methylaziridine).
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    THERMAL-DEGRADATION BEHAVIOR AND KINETIC-PARAMETERS OF COPOLYMERS OBTAINED BY COPOLYMERIZATION VIA ZWITTERION
    (1991) RIVAS, BL; PIZARRO, GD; TAGLE, LH
    The thermal degradation of a series of 18 copolymers corresponding to poly(p-methoxy-phenylmaleimide-co-2-methyl-2-oxazoline), poly(p-methoxyphenylmaleimide-co-2-ethyl-2-oxazoline), poly(p-nitrophenylmaleimide-co-2-methyl-2-oxazoline) and poly(p-nitrophenyl-maleimide-co-2-ethyl-2-oxazoline) has been investigated using thermogravimetry in the temperature range 20-500-degrees-C. All the copolymers degrade in one step. The kinetic parameters E(a), n and A have been calculated. The thermal stability depends on the copolymer composition.
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    THERMAL-DEGRADATION OF COPOLYMERS BASED ON 2-SUBSTITUTED OXAZOLINES AND BETA-METHYLHYDROGENITACONATE
    (1994) RIVAS, BL; DELPIZARRO, G; TAGLE, LH
    The thermal stabilities of poly(beta-methylhydrogenitaconate-co-2-methyl-2-oxazoline) and poly(beta-methylhydrogenitaconate-co-2-ethyl-2-oxazoline) obtained by spontaneous copolymerization have been studied by programmed thermogravimetric analysis over the temperature range from 293 K to 773 K under a flow of nitrogen. Most of the copolymers do not show weight loss until 473 K and they degrade in one step. The kinetic parameters Ea, n and A were obtained following one method of thermogravimetric analysis. The reaction order for all copolymers was 1.0. The poly(beta-methylhydrogenitaconate-co-2-methyl-2-oxazoline)s were the most thermostable copolymers.