Browsing by Author "CARDENAS, G"

Now showing 1 - 14 of 14
  • Thumbnail Image
    Item
    THERMAL STUDIES OF METAL POLY(BUTYL METHACRYLATES) .13.
    (GORDON BREACH SCI PUBL LTD, 1994) CARDENAS, G; SALGADO, E; TAGLE, LH
    Metal poly(butyl methacrylates) polymers were obtained by radical polymerization with benzoyl peroxide. The monomer was cocondensed with the metals: Cu, Ag, Au, Pd, Zn, Cd, Ga, In, Ge, Sn, Sb and Bi. The metals were evaporated to produce atoms and with the monomer they can generate a matrix at 77 K. After the warm up process, metal-monomer colloids can be obtained. The colloids were polymerized with benzoyl peroxide at 70 degrees C for 0.5 h at 70 degrees C. Four different initiator concentrations (0.5, 1.0, 1.25 and 5.0 mol%) were used. The yields are over 50% and the viscosimetric molecular weight range from 10(4)-10(5) g/mol. The higher My are Sb, In, Ag and Ge-poly(butyl methacrylates). The thermal stabilities of these metal polymers have been studied by thermogravimetry (TG) between 25 and 550 degrees C under nitrogen flow. The decomposition temperature was obtained from the maximum of the first derivative from TG curve. The kinetic parameters of the thermal decomposition were determined by the Arrhenius equation. All these polymers degrade in a single step around 300 degrees C. The kinetic data thus obtained show the thermostabilities decrease in the order: Pd-PBMA > Au-PBMA > In-PBMA > Sn-PBMA > Ag-PBMA > Sb-PBMA > Bi-PBMA > Ge-PBMA > Zn-PBMA > Ga-PBMA > Cu-PRMA > Cd-PBMA. The thermal stability apparently is depending upon the metal incorporated in the polymer matrix. The decomposition reaction order is -0.25 or -0.5 which means that we are in the presence of a complex single decomposition reaction, The pre-exponential factor, the activation energy, the reaction order and the decomposition temperature for all the polymers have been determined.
  • No Thumbnail Available
    Item
    THERMAL STUDIES OF METAL POLY(N-BUTYL METHACRYLATES) .10.
    (1993) CARDENAS, G; SALGADO, E; TAGLE, LH
    Metal poly(n-butylmethacrylates) polymers were obtained by radical polymerization with azodiisobutyronitrile (AIBN). The thermal stabilities of the metal polymers (M-PBMA) have been studied by thermogravimetry (TG) between 25 and 550-degrees-C under nitrogen flow. The decomposition temperature was obtained from the first derivative of the TG curve. The kinetic parameters of the thermal decomposition were determined by the Arrhenius equation. All these polymers degrade in a single step. The kinetic data thus obtained show that the thermostabilities decrease in the order Pd-PBMA > Ga-PBMA > Cu-PBMA > Ag-PBMA > Au-PBMA > Al-PBMA > Cd-PBMA > Ge-PBMA > Zn-PBMA > Sb-PBMA > In-PBMA > Sn-PBMA. In fact, the thermal stability is dependent upon the metal incorporated in the polymer, the highest being stable up to 389-degrees-C and the lowest up to 260-degrees-C. The order of reaction from the thermal decomposition of these metal polymers was found to be -0.25 for the homopolymers, Pd, Au, Ag, Cd, Zn, Ga, Ge and Sn but -0.5 for Bi, Sb and Al. The pre-exponential factor, the reaction order and the activation energy of the decomposition reaction for M-PBMA have been determined.
  • Thumbnail Image
    Item
    THERMAL STUDIES OF METAL POLY(STYRENE-CO-ACRYLONITRILE) .14.
    (TAYLOR & FRANCIS AS, 1994) CARDENAS, G; ACUNA, J; CARBACHO, H; RODRIGUEZ, M; TAGLE, LH
    The thermal stabilities of metal poly(styrene-co-acrylonitrile) has been studied by thermogravimetry (TG) between 278 K and 823 K under nitrogen flow. The kinetic data thus obtained indicate that the thermostabilities decrease in the order: Sn-STAN > Ga-STAN > Ag-STAN > Sb-STAN > Cu-STAN > Pd-STAN > Fe-STAN > Au-STAN > Bi-STAN for high Molecular Weight (HMW) and Ag-STAN > Pd-STAN > Fe-STAN > Ga-STAN > Cu-STAN > Sb-STAN > Sn-STAN > Bi-STAN > Au-STAN for low Molecular Weight (LMW) copolymers. The thermal stability seems to be dependable on the nature of the bond established between the copolymer and the metal. Cu-copolymer exhibits the lowest Ea most probably due to their oxidation potential. On the other hand, Ag-copolymer has the highest Ea and similar to the copolymer (fraction 1). The thermal decomposition temperatures were obtained from the DTG curves. The reaction order for the thermal decomposition of these copolymers is zero. In other words, we are dealing with a single step decomposition mechanism. The pre-exponential factor, the reaction order, the decomposition temperature and the activation energy of the decomposition for metal poly(styrene-co-acrylonitrile) have been determined.
  • No Thumbnail Available
    Item
    THERMAL STUDIES OF METAL POLY(VINYL ACETATES) .9.
    (1995) CARDENAS, G; MUNOZ, C; TAGLE, LH
    Metal poly(vinyl acetates) polymers were obtained by radical polymerization with azodiisobutyronitrile. The thermal stabilities of the metal polymers (M-PVAC) have been studied by thermogravimetry (TG) between 25 and 550-degrees-C under nitrogen flow. The decomposition temperature was obtained from the maximum of the first derivative from TG curve. The kinetic parameters of the thermal decomposition were determined by the Arrhenius equation. All these polymers degrade mainly in a single step with a very small second step, probably via a complex reaction. The kinetic data thus obtained show that the thermostabilities decrease in the order: Sb-PVA(c) approximately Ge-PVA(c) > Bi-PVA(c) approximately Cd-PCA(c) > Ag-PVA(c) approximately PVA(c) > Zn-PVA(c) > Au-PVA(c) > In-PVA(c) > Sn-PVA(c) > Ga-PVA(c) > Pd-PVA(c).
  • No Thumbnail Available
    Item
    THERMAL STUDIES OF METAL POLYSTYRENES .4.
    (1992) CARDENAS, G; RETAMAL, C; TAGLE, LH
    The thermal stability of metal polystyrene was determined by thermogravimetric analyses (TGA) from 25 to 250-degrees-C under nitrogen flow.
  • No Thumbnail Available
    Item
    THERMAL STUDIES OF METAL-FILMS PREPARED WITH OXYGENATED SOLVENTS .12.
    (1994) CARDENAS, G; OLIVA, R; TAGLE, LH
    Copper, silver and gold colloids have been prepared by Chemical Liquid Deposition (CLD) with dimethoxymethane, 2-methoxyethyl ether and ethylenglycol dimethyl ether. The metals are evaporated to yield atoms which are solvated at low temperatures and during the warm up process colloidal sols with metal clusters are obtained.
  • No Thumbnail Available
    Item
    THERMAL STUDIES OF ORGANOZINC FILMS .11.
    (1994) CARDENAS, G; OLIVA, R; TAGLE, LH
    The thermal stability of organozinc films was studied by thermogravimetric analysis (TGA) between 25 and 550-degrees-C min-1. The decomposition temperatures were obtained from the maximum of the first derivatives of the TG curve. The kinetic parameters of the thermal decomposition were determined by the Arrhenius equation. All the films degraded in one step with a very small weight loss. Films prepared with toluene and THF exhibit higher weight losses, 23.77% and 12.48%, respectively, and zinc-2-propanol film is the most stable (1.11% weight loss).
  • No Thumbnail Available
    Item
    THERMAL-ANALYSIS OF METAL POLYACRYLONITRILES
    (1991) CARDENAS, G; RETAMAL, C; TAGLE, LH
    The thermal stabilities of metal polyacrylonitriles (MPAN) were studied by thermogravimetric analysis (TGA) between 25 and 550-degrees-C under nitrogen flowing at 10-degrees-C min-1. The metal contents of the polymers and their molecular weights are also reported. The kinetic data obtained by TGA showed that the thermostabilities of these polymers decrease in the order: Ge-PAN > Ga-PAN > Au-PAN > Sn-PAN > Bi-PAN > In-PAN > Pd-PAN > Sb-PAN. The experimental data suggest that the thermal stability of these polymers depends on the metal and the amount of metal incorporated. The reaction order for the one-step thermal decomposition of the polymers was found to be zero. The pre-exponential factor, the reaction order and the activation energies for the decomposition of the metal polyacrylonitriles were determined.
  • Thumbnail Image
    Item
    THERMOGRAVIMETRIC ANALYSIS OF ORGANOMETALLIC FILMS
    (ELSEVIER SCIENCE BV, 1991) CARDENAS, G; TAGLE, LH
    The thermal behaviour of organometallic films was studied by thermogravimetric analysis (TGA) between 25 and 550-degrees-C at 10-degrees-C min-1. From the kinetic data obtained by TGA, it was found that the thermostability of these metal films depends on the metal and solvent. For palladium films the stability decreases in the following order: acetone, 2-butanone, dimethylformamide (DMF), 2-propanol, dimethyl sulphoxide (DMSO), tetrahydrofuran (THF), ethanol. For germanium films the stability decreases in the order acetone, 2-propanol, DMF, ethanol, 2-butanone, THF. For indium films the order of decreasing stability is DMF, ethanol, acetone, 2-butanone, DMSO, THF, 2-propanol.
  • No Thumbnail Available
    Item
    THERMOGRAVIMETRIC STUDIES OF CHITIN DERIVATIVES .1.
    (1993) CARDENAS, G; RETAMAL, J; TAGLE, LH
    The thermal stabilities of chitin derivatives (chitin; chitin iodine, acetate, phenylthiourea, tosylate, butyl xantate, benzyl xantate, isocyanate hexane. benzoate and benzoylate) have been studied by thermogravimetry (TG) between 278 K and 823 K under nitrogen flow. The kinetic data thus obtained indicate that the thermostabilities decrease in the order: chitin-acetate > chitin-phenylthiourea > chitin-isocyanate hexane > chitin-butylxantate > chitin-benzoate > chitin-benzylxanthate > chitin-iodine > chitin benzoylate.
  • Thumbnail Image
    Item
    THERMOGRAVIMETRIC STUDIES OF CHITOSAN DERIVATIVES
    (ELSEVIER SCIENCE BV, 1992) CARDENAS, G; BERNAL, L; TAGLE, LH
    The thermal stabilities of chitosan derivatives (chito; 2-amino-2-deoxy(1-4)-beta-D-glucopyranan) have been studied by thermogravimetry (TG) between 25 and 550-degrees-C under nitrogen flow. The kinetic data thus obtained indicate that the thermostabilities decrease in the order, chito-salicylaldehyde > chito-thioglycolic acid > chito > chito-butanoyl chloride > chito-4-Br-aniline > chito-4-NO2benzene > chito-benzoic acid > chito-benzoyl chloride. The thermal stability apparently depends on the kind of bond established between the chitosan and the reactants. Schiff bases are more stable than amides and alkyl amines. The order of reaction for the thermal decomposition of these chitosan polymers ranges between -0.5 and -1.0. This is probably due to several overlapped processes. The pre-exponential factor, the reaction order and the activation energy of the decomposition for chitosan derivatives have been determined.
  • No Thumbnail Available
    Item
    THERMOGRAVIMETRIC STUDIES OF METAL (STYRENE-METHYL METHACRYLATE) COPOLYMERS .5.
    (1992) CARDENAS, G; TAGLE, LH
    Metal (styrene-methyl methacrylate) copolymers were obtained by radical polymerization with azodiisobutyronitrile.
  • Thumbnail Image
    Item
    THERMOGRAVIMETRIC STUDIES OF METAL POLY(METHYL METHACRYLATES)
    (ELSEVIER SCIENCE BV, 1991) CARDENAS, G; RETAMAL, C; TAGLE, LH
    The thermal stabilities of metal poly(methyl methacrylate)s (PMMA) have been studied by thermogravimetry (TG) between 25 and 550-degrees-C under nitrogen flow. The kinetic data thus obtained show that the thermostabilities decrease in the order, Au-PMMA > Bi-PMMA > In-PMMA > Cu-PMMA > Ge-PMMA > Sb-PMMA > Pd-PMMA > Sn-PMMA > Ga-PMMA, suggesting that thermal stability is dependent upon the metal incorporated in the backbone. The order of reaction for the thermal decomposition of these metal polymers was found to be zero. The pre-exponential factor, the reaction order and the activation energy of the decomposition for metal poly(methyl methacrylates) have been determined and the reactions found to be zero order.
  • Thumbnail Image
    Item
    THERMOGRAVIMETRIC STUDIES OF POLY(OXYMETHYLENE-CO-DIMETHYLSILOXANE) COPOLYMERS
    (ELSEVIER SCIENCE BV, 1993) RODRIGUEZBAEZA, M; ZAPATA, M; CARDENAS, G; TAGLE, LH
    The thermal stability and kinetic parameters of a series of poly(oxymethylene-co-dimethylsiloxane) copolymers have been studied by thermogravimetry from 303 to 846K under nitrogen flow. The new copolymers, obtained by ring-opening copolymerization of 1,3,5-trioxane and hexamethylcyclotrisiloxane, contain different concentrations of oxymethylene and dimethylsiloxane comonomer units. The results of the thermal studies were compared with data corresponding to pure poly(oxymethylene) and poly(dimethyl-siloxane). The copolymers with low concentration of dimethylsiloxane comonomer units show only one degradation process, but copolymers richer in this co-unit degrade in two stages. Copolymers with an even higher concentration of dimethylsiloxane co-unit have three decomposition processes. The TGA results indicate that the molecular structure of the copolymers correspond to block copolymers and random copolymers bonded to segments formed by both pure poly(oxymethylene) and poly(dimethylsiloxane). The structures depend on the composition of the copolymers. The pre-exponential factors, the reaction orders and the activation energies have been determined from non-isothermal thermogravimetric data.