Eduardo Canedo - Academia.edu (original) (raw)

Papers by Eduardo Canedo

Polímeros

Montmorillonite (MMT), natural (AN) and purified (AP) bentonite clays modified with alkyl ammoniu... more Montmorillonite (MMT), natural (AN) and purified (AP) bentonite clays modified with alkyl ammonium (A), alkyl phosphonium (F) and a mixture of both (A and F) salts were incorporated (1% w/w) into PET by melt blending. The hybrids thus obtained were characterized by XRD, TG, DSC and TEM. Nanocomposites having intercalated ordered structures and intercalated disordered/exfoliated structures were obtained with the clays modified with the ammonium and the mixture of ammonium and phosphonium salts, respectively. A nanocomposite was not obtained with the addition of 1% w/w of an alkyl phosphonium modified clay into PET. The organoclays ANOA, APOF and MMTOF, when added to PET not only led to an increase in its thermal stability but also acted as heterogeneous nucleating agents, increasing its crystallization temperature. This result is industrially significant as the low crystallization rate of PET makes its use difficult in preparing injected goods. Besides, as the behaviour of the bentonite clays supplied by a local industry was similar to that of the imported montmorillonite, the use of this raw material of lower cost, modified with national technology, can be an attractive technology for injection molded PET applications, where cost is of utmost importance.

Polímeros

The present work is concerned with the effect of low concentrations (0.5 e 1.0%) of poly(3-hydrox... more The present work is concerned with the effect of low concentrations (0.5 e 1.0%) of poly(3-hydroxybutirate) (PHB) on the isothermal cold crystallization of poly(ethylene terephthalate) (PET). Energy curves were obtained by differential scanning calorimetry (DSC) and the kinetics of the crystallization was analyzed using Avrami's method. Two crystallization stages were observed. Results showed that the presence of PHB affects the crystallization rate of PET, as verified by changes in the time needed to reach 1, 10, 30, 50 and 99% of crystallinity. Activation energies for the two crystallization stages were computed using Arrhenius plots; PET/PHB mixtures showed slightly smaller values. The equilibrium melting temperatures were estimated according to the procedure of Hoffman and Weeks; the higher values obtained for the PET/PHB mixtures suggest that PHB affects the crystalline structure of PET.

Minerals, Metals and …, Jan 1, 2010

Polymer nanocomposites have several advantages over conventional microcomposites, among which is ... more Polymer nanocomposites have several advantages over conventional microcomposites, among which is the fact that similar or better properties can be obtained at very low loadings(1-5%). Layered silicates such as those present in bentonite clays are some of the most useful ...

Journal of Applied Polymer …

Blends of poly(ethylene terephthalate) (PET) with small amounts of styrene-co-acrylonitrile (SAN)... more Blends of poly(ethylene terephthalate) (PET) with small amounts of styrene-co-acrylonitrile (SAN) were prepared by melt blending, and cold crystallization of these mixtures was investigated by means of differential scanning calorimetry. The results suggest that SAN interacts with the amorphous phase of PET, as observed by variations in the glass transition temperature and in the morphology of the blends, analyzed by scanning electron microscopy. The addition of 1% SAN promoted a significant reduction in the crystallization rate of PET, in a man-ner similar to that of an antinucleating agent. However, the crystallinity of the PET/SAN blends was comparable with that of neat PET; hence, mechanical properties were only slightly affected. Kinetic parameters were determined using Avrami theory; Avrami plots presented a nonlinear behavior at the end of crystallization, indicating that cold crystallization proceeds in two stages.

Journal of Materials …, Jan 1, 2011

The thermal transitions and the nonisothermal cold crystallization kinetics of poly(ethylene tere... more The thermal transitions and the nonisothermal cold crystallization kinetics of poly(ethylene terephthalate) (PET) at constant heating rates were investigated using differential scanning calorimetry. It was found that the glass transition and crystallization temperature increased with the heating rates, while the melting temperature showed a little variation for the heating rates used. Crystallization and melting latent heats were remarkably constant, independent of the heating rate. Kinetics parameters were determined using Ozawa model. Two different kinetic regimes were identified, corresponding to primary and secondary crystallization, at low and high fractional crystallization, respectively, both following Ozawa's model. Kinetics parameters were determined for the primary and secondary regimes; the pre-exponential constant (K T ) and Ozawa's exponent (m) decreased with increasing crystallization temperature. The combined kinetic parameter Z5K 1=m T increased exponentially with temperature; activation energies were estimated using Arrhenius plots for the two PET crystallization regimes.

TECHNICAL …, Jan 1, 1996

Page 434. COMPOUNDING OF GLASS REINFORCED PLASTICS IN COROTATING INTER-MESHING TWIN-SCREW EXTRUDE... more Page 434. COMPOUNDING OF GLASS REINFORCED PLASTICS IN COROTATING INTER-MESHING TWIN-SCREW EXTRUDER WITH NOVEL MIXING SECTIONS. LefterisN. Valsamis and Eduardo L. Canedo Parrel Corporation, Ansonia, Conn. ...

ANTEC'95., Jan 1, 1995

Mixing in corotating intermeshing twin-screw extruders with Farrel asymmetric modular mixing elem... more Mixing in corotating intermeshing twin-screw extruders with Farrel asymmetric modular mixing elements(Famme). EL Canedo, LN Valsamis ANTEC'95. 1, 312-320, 5/1995. Simplified mathematical models were used to characterize ...

Polymer …, Jan 1, 2009

A sodium bentonite (montmorillonite-based layered silicate clay) was organically modified with ce... more A sodium bentonite (montmorillonite-based layered silicate clay) was organically modified with cetyl trimethyl ammonium bromide (cetrimide), using different clay/ water ratios-but the same clay/cetrimide ratio-to suspend the bentonite clay and perform its organophilization. Infrared spectroscopy and thermogravimetric analysis indicated the incorporation of organic modifier into the bentonite. Wide-angle X-ray scattering showed that the incorporation of surfactant significantly increased the interlayer spacing in the bentonite for all concentrations studied. It was found that clay/water ratio employed during the modification affects neither the amount of organic salt incorporated nor the interlayer spacing in the organobentonites, but influences its degree of structural disorder. Lower clay/water ratios resulted in a more disorderly structure, as established by the decrease of the areas under the X-ray peaks as the clay/water ratio diminishes. The modified bentonites were melt compounded with maleic anhydride-grafted polypropylene. X-ray diffraction patterns of the hybrids revealed that the more disorderly organobentonites were better dispersed in the polymer matrix, indicating that, in the present system, the structure of polymer nanocomposites obtained were affected by the clay/water ratio used in organobentonite preparation.

AIChE Journal, Jan 1, 1989

A study of the flow of viscous liquids contained in an open cavity driven by a moving wall has be... more A study of the flow of viscous liquids contained in an open cavity driven by a moving wall has been undertaken as a first step toward understanding interphase heat and mass transport in polymer processing equipment where rolling pools of liquid are generated. Solutions to the equations of motion for creeping flow in cavities of different aspect ratios were obtained using a finite-differences technique for circumstances when the wall moves in the same direction as the gravitational field.

AIChE journal, Jan 1, 1993

liquids subjected to simple (plane Couette) shear from an experimental point of view.

Polímeros

Montmorillonite (MMT), natural (AN) and purified (AP) bentonite clays modified with alkyl ammoniu... more Montmorillonite (MMT), natural (AN) and purified (AP) bentonite clays modified with alkyl ammonium (A), alkyl phosphonium (F) and a mixture of both (A and F) salts were incorporated (1% w/w) into PET by melt blending. The hybrids thus obtained were characterized by XRD, TG, DSC and TEM. Nanocomposites having intercalated ordered structures and intercalated disordered/exfoliated structures were obtained with the clays modified with the ammonium and the mixture of ammonium and phosphonium salts, respectively. A nanocomposite was not obtained with the addition of 1% w/w of an alkyl phosphonium modified clay into PET. The organoclays ANOA, APOF and MMTOF, when added to PET not only led to an increase in its thermal stability but also acted as heterogeneous nucleating agents, increasing its crystallization temperature. This result is industrially significant as the low crystallization rate of PET makes its use difficult in preparing injected goods. Besides, as the behaviour of the bentonite clays supplied by a local industry was similar to that of the imported montmorillonite, the use of this raw material of lower cost, modified with national technology, can be an attractive technology for injection molded PET applications, where cost is of utmost importance.

Polímeros

The present work is concerned with the effect of low concentrations (0.5 e 1.0%) of poly(3-hydrox... more The present work is concerned with the effect of low concentrations (0.5 e 1.0%) of poly(3-hydroxybutirate) (PHB) on the isothermal cold crystallization of poly(ethylene terephthalate) (PET). Energy curves were obtained by differential scanning calorimetry (DSC) and the kinetics of the crystallization was analyzed using Avrami's method. Two crystallization stages were observed. Results showed that the presence of PHB affects the crystallization rate of PET, as verified by changes in the time needed to reach 1, 10, 30, 50 and 99% of crystallinity. Activation energies for the two crystallization stages were computed using Arrhenius plots; PET/PHB mixtures showed slightly smaller values. The equilibrium melting temperatures were estimated according to the procedure of Hoffman and Weeks; the higher values obtained for the PET/PHB mixtures suggest that PHB affects the crystalline structure of PET.

Minerals, Metals and …, Jan 1, 2010

Polymer nanocomposites have several advantages over conventional microcomposites, among which is ... more Polymer nanocomposites have several advantages over conventional microcomposites, among which is the fact that similar or better properties can be obtained at very low loadings(1-5%). Layered silicates such as those present in bentonite clays are some of the most useful ...

Journal of Applied Polymer …

Blends of poly(ethylene terephthalate) (PET) with small amounts of styrene-co-acrylonitrile (SAN)... more Blends of poly(ethylene terephthalate) (PET) with small amounts of styrene-co-acrylonitrile (SAN) were prepared by melt blending, and cold crystallization of these mixtures was investigated by means of differential scanning calorimetry. The results suggest that SAN interacts with the amorphous phase of PET, as observed by variations in the glass transition temperature and in the morphology of the blends, analyzed by scanning electron microscopy. The addition of 1% SAN promoted a significant reduction in the crystallization rate of PET, in a man-ner similar to that of an antinucleating agent. However, the crystallinity of the PET/SAN blends was comparable with that of neat PET; hence, mechanical properties were only slightly affected. Kinetic parameters were determined using Avrami theory; Avrami plots presented a nonlinear behavior at the end of crystallization, indicating that cold crystallization proceeds in two stages.

Journal of Materials …, Jan 1, 2011

The thermal transitions and the nonisothermal cold crystallization kinetics of poly(ethylene tere... more The thermal transitions and the nonisothermal cold crystallization kinetics of poly(ethylene terephthalate) (PET) at constant heating rates were investigated using differential scanning calorimetry. It was found that the glass transition and crystallization temperature increased with the heating rates, while the melting temperature showed a little variation for the heating rates used. Crystallization and melting latent heats were remarkably constant, independent of the heating rate. Kinetics parameters were determined using Ozawa model. Two different kinetic regimes were identified, corresponding to primary and secondary crystallization, at low and high fractional crystallization, respectively, both following Ozawa's model. Kinetics parameters were determined for the primary and secondary regimes; the pre-exponential constant (K T ) and Ozawa's exponent (m) decreased with increasing crystallization temperature. The combined kinetic parameter Z5K 1=m T increased exponentially with temperature; activation energies were estimated using Arrhenius plots for the two PET crystallization regimes.

TECHNICAL …, Jan 1, 1996

Page 434. COMPOUNDING OF GLASS REINFORCED PLASTICS IN COROTATING INTER-MESHING TWIN-SCREW EXTRUDE... more Page 434. COMPOUNDING OF GLASS REINFORCED PLASTICS IN COROTATING INTER-MESHING TWIN-SCREW EXTRUDER WITH NOVEL MIXING SECTIONS. LefterisN. Valsamis and Eduardo L. Canedo Parrel Corporation, Ansonia, Conn. ...

ANTEC'95., Jan 1, 1995

Mixing in corotating intermeshing twin-screw extruders with Farrel asymmetric modular mixing elem... more Mixing in corotating intermeshing twin-screw extruders with Farrel asymmetric modular mixing elements(Famme). EL Canedo, LN Valsamis ANTEC'95. 1, 312-320, 5/1995. Simplified mathematical models were used to characterize ...

Polymer …, Jan 1, 2009

A sodium bentonite (montmorillonite-based layered silicate clay) was organically modified with ce... more A sodium bentonite (montmorillonite-based layered silicate clay) was organically modified with cetyl trimethyl ammonium bromide (cetrimide), using different clay/ water ratios-but the same clay/cetrimide ratio-to suspend the bentonite clay and perform its organophilization. Infrared spectroscopy and thermogravimetric analysis indicated the incorporation of organic modifier into the bentonite. Wide-angle X-ray scattering showed that the incorporation of surfactant significantly increased the interlayer spacing in the bentonite for all concentrations studied. It was found that clay/water ratio employed during the modification affects neither the amount of organic salt incorporated nor the interlayer spacing in the organobentonites, but influences its degree of structural disorder. Lower clay/water ratios resulted in a more disorderly structure, as established by the decrease of the areas under the X-ray peaks as the clay/water ratio diminishes. The modified bentonites were melt compounded with maleic anhydride-grafted polypropylene. X-ray diffraction patterns of the hybrids revealed that the more disorderly organobentonites were better dispersed in the polymer matrix, indicating that, in the present system, the structure of polymer nanocomposites obtained were affected by the clay/water ratio used in organobentonite preparation.

AIChE Journal, Jan 1, 1989

A study of the flow of viscous liquids contained in an open cavity driven by a moving wall has be... more A study of the flow of viscous liquids contained in an open cavity driven by a moving wall has been undertaken as a first step toward understanding interphase heat and mass transport in polymer processing equipment where rolling pools of liquid are generated. Solutions to the equations of motion for creeping flow in cavities of different aspect ratios were obtained using a finite-differences technique for circumstances when the wall moves in the same direction as the gravitational field.

AIChE journal, Jan 1, 1993

liquids subjected to simple (plane Couette) shear from an experimental point of view.