Jorge Aburto | UNAN-Managua - Academia.edu (original) (raw)
Papers by Jorge Aburto
Starch-starke, 1999
French potato starch was supplied by INRA (Nantes, France). Octanoated dextrin (DS 8 2.9) and oct... more French potato starch was supplied by INRA (Nantes, France). Octanoated dextrin (DS 8 2.9) and octanoated starch (DS 8 2.7) were prepared by a modified method using pyri-132 Starch/Stärke 51 (1999) Nr. 4, S. 132-135
Carbohydrate Polymers, 1997
Octanoated starch (OCST) was prepared by esterification of native starch with octanoyl chloride. ... more Octanoated starch (OCST) was prepared by esterification of native starch with octanoyl chloride. The new material was characterised by 'H NMR, FTIR, and elemental analysis. This showed that the esteritication had proceeded to a degree of substitution of 2.7. The octanoated starch was subsequently mixed with low density polyethylene (LDPE) at various proportions in a Haake Rheomixer. Similar blends of LDPE were also prepared with plasticised starch (PLST) for comparison purposes. The thermomechanical properties were determined as a function of blend composition. The prepared LDPE/OCST blends show better mechanical properties compared to their respective LDPE/PLST blends. In particular, the elongation at breaking is signilkantly higher in the LDPE/OCST blends. The latter exhibit also a higher thermal stability and a low water absorption. Copyright 0 1997 Elsevier Science Ltd. AU rights . The disadvantage of these
Journal of Applied Polymer Science, 1997
In the present study, starch octanoates OCST1.8 and OCST2.7 with degrees of substitution (d.s.) o... more In the present study, starch octanoates OCST1.8 and OCST2.7 with degrees of substitution (d.s.) of 1.8 and 2.7, respectively, and dodecanoate DODST2.7 (d.s. Å 2.7), were prepared by esterification of native starch with fatty acid chlorides. Our analyses, including elemental analysis, FTIR, contact angle, DSC, and TGA measurements confirmed the esterification reaction of starch and the degree of substitution. The ester group was found to act like an internal plasticizer, with an increase in the number and the size of fatty acyl chains grafted onto starch. These starch esters were mixed with low density polyethylene (LDPE) at various proportions in a Haake Rheomixer. Water and moisture absorption, thermal and mechanical properties, and biodegradation were investigated as a function of blend composition. The DODST2.7/LDPE blends showed, in general, better thermal stability and higher elongation, but lower tensile strength and water absorption, than did corresponding OCST/LDPE blends. The addition of starch esters to LDPE led to a very slow rate of biodegradation of these blends.
Polymer Degradation and Stability, 1998
Starch-starke, 2005
This study deals with the organic solvent-free synthesis of fatty acid esters of high-amylose mai... more This study deals with the organic solvent-free synthesis of fatty acid esters of high-amylose maize (amylomaize) starch by transesterification with lauric acid methyl ester using potassium laurate as catalyst. The process involves thermal pretreatment of amylomaize in order to swell the polysaccharide and increase its accessibility and reaction with the esterification reagent. The swelling degree (Q) was monitored by UV-Vis spectrophotometry and scanning electron microscopy (SEM), whilst the formation of a complex between amylose and potassium laurate was confirmed by X-ray diffraction and FTIR studies. The transesterification reaction was carried out at 190°C and a central composite design was used to obtain the corresponding contour plots with a second order model (y = β0 + β1 X1 + β2 X2 + β12 X1 X2 + β11 X1 X1 + β22 X2X2) and a confidence interval of 95%. The experimental design consisted of two independent variables, reaction time (2–6 h) and catalyst (2.2 – 33.8 meq catalyst per eq. glucose), and two dependent variables, the degree of substitution (DS) and the yield of the amylomaize starch ester (Y,%). Maximum transesterification of amylomaize starch (DS = 0.61) was obtained after 4:30 h at 190°C with an intermediate concentration of catalyst (18 meq per eq. glucose). Finally, the optimized results were extended to other starch sources and vegetable oils.
Journal of Applied Polymer Science, 1999
In the present article a series of low-density polyethylene (LDPE) blends with different amounts ... more In the present article a series of low-density polyethylene (LDPE) blends with different amounts of fatty esters of amylose and starch, were prepared in a Haake-Buchler Reomixer. The tensile as well as the dynamic thermomechanical (DMTA) properties of the blends were measured. It was found that as the amount of the esters increases in the blends, the tensile strength and especially the elongation at break decrease nonlinearly. Scanning electron microscopy (SEM) was used to assess the interfacial adhesion between LDPE and the corresponding esters. The incompatibility of the blends was also verified with DMTA and differential scanning calorimetry (DSC). From the biodegradation studies of the blends during exposure in activated sludge, it was found that all esters are biodegradable, although to a much lesser degree compared to pure strach. The biodegradation rate of the composites is relatively small due to the low biodegradation rate of the pure esters.
Journal of Applied Polymer Science, 1999
In the present article a series of low-density polyethylene (LDPE) blends with different amounts ... more In the present article a series of low-density polyethylene (LDPE) blends with different amounts of fatty esters of amylose and starch, were prepared in a Haake-Buchler Reomixer. The tensile as well as the dynamic thermomechanical (DMTA) properties of the blends were measured. It was found that as the amount of the esters increases in the blends, the tensile strength and especially the elongation at break decrease nonlinearly. Scanning electron microscopy (SEM) was used to assess the interfacial adhesion between LDPE and the corresponding esters. The incompatibility of the blends was also verified with DMTA and differential scanning calorimetry (DSC). From the biodegradation studies of the blends during exposure in activated sludge, it was found that all esters are biodegradable, although to a much lesser degree compared to pure strach. The biodegradation rate of the composites is relatively small due to the low biodegradation rate of the pure esters.
Journal of Applied Polymer Science, 1999
In the present study, a series of poly(ethylene succinate)/poly(1-caprolactone) block copolymers ... more In the present study, a series of poly(ethylene succinate)/poly(1-caprolactone) block copolymers were prepared by using a two step process. In the first step, poly(ethylene succinate) (PESu) was synthesized by the melt polycondensation process while in the second, block copolymers were prepared by ring opening polymerization of 1-caprolactone (1-CL) in the presence of stannous octoate. The copolymers were analysed with 1 H NMR spectroscopy and were confirmed to possess final compositions very similar to the initial feed compositions. An increase in the 1-CL content led to an increase in the molecular weights of the copolymer, while polydispersity was narrowed. In the DSC thermographs, two melting points were recorded for copolymers containing 75 and 50 mol% PESu, confirming that block copolymers were prepared. The incorporation of 1-CL content in macromolecular chains resulted in a substantial decrease of the crystallization rates of the copolymers. PESu is a brittle material due to its low molecular weight, while the copolymer containing 75 mol% 1-CL possesses sufficient tensile strength and elongation at break. Enzymatic degradation was performed using Rhizopus delemar lipase in a buffer solution at 37 8C. Biodegradation rates were mainly affected by the crystallinity of copolymers, rather than from their molecular weight. PESu and copolymer films were degraded into very small fragments after six months soil burial while polycaprolactone remained almost unaffected. q 2002 Published by Elsevier Science Ltd.
Journal of Applied Polymer Science, 1997
In the present study, starch octanoates OCST1.8 and OCST2.7 with degrees of substitution (d.s.) o... more In the present study, starch octanoates OCST1.8 and OCST2.7 with degrees of substitution (d.s.) of 1.8 and 2.7, respectively, and dodecanoate DODST2.7 (d.s. Å 2.7), were prepared by esterification of native starch with fatty acid chlorides. Our analyses, including elemental analysis, FTIR, contact angle, DSC, and TGA measurements confirmed the esterification reaction of starch and the degree of substitution. The ester group was found to act like an internal plasticizer, with an increase in the number and the size of fatty acyl chains grafted onto starch. These starch esters were mixed with low density polyethylene (LDPE) at various proportions in a Haake Rheomixer. Water and moisture absorption, thermal and mechanical properties, and biodegradation were investigated as a function of blend composition. The DODST2.7/LDPE blends showed, in general, better thermal stability and higher elongation, but lower tensile strength and water absorption, than did corresponding OCST/LDPE blends. The addition of starch esters to LDPE led to a very slow rate of biodegradation of these blends.
Starch-starke, 1999
French potato starch was supplied by INRA (Nantes, France). Octanoated dextrin (DS 8 2.9) and oct... more French potato starch was supplied by INRA (Nantes, France). Octanoated dextrin (DS 8 2.9) and octanoated starch (DS 8 2.7) were prepared by a modified method using pyri-132 Starch/Stärke 51 (1999) Nr. 4, S. 132-135
Starch-starke, 1999
French potato starch was supplied by INRA (Nantes, France). Octanoated dextrin (DS 8 2.9) and oct... more French potato starch was supplied by INRA (Nantes, France). Octanoated dextrin (DS 8 2.9) and octanoated starch (DS 8 2.7) were prepared by a modified method using pyri-132 Starch/Stärke 51 (1999) Nr. 4, S. 132-135
Carbohydrate Polymers, 1997
Octanoated starch (OCST) was prepared by esterification of native starch with octanoyl chloride. ... more Octanoated starch (OCST) was prepared by esterification of native starch with octanoyl chloride. The new material was characterised by 'H NMR, FTIR, and elemental analysis. This showed that the esteritication had proceeded to a degree of substitution of 2.7. The octanoated starch was subsequently mixed with low density polyethylene (LDPE) at various proportions in a Haake Rheomixer. Similar blends of LDPE were also prepared with plasticised starch (PLST) for comparison purposes. The thermomechanical properties were determined as a function of blend composition. The prepared LDPE/OCST blends show better mechanical properties compared to their respective LDPE/PLST blends. In particular, the elongation at breaking is signilkantly higher in the LDPE/OCST blends. The latter exhibit also a higher thermal stability and a low water absorption. Copyright 0 1997 Elsevier Science Ltd. AU rights . The disadvantage of these
Journal of Applied Polymer Science, 1997
In the present study, starch octanoates OCST1.8 and OCST2.7 with degrees of substitution (d.s.) o... more In the present study, starch octanoates OCST1.8 and OCST2.7 with degrees of substitution (d.s.) of 1.8 and 2.7, respectively, and dodecanoate DODST2.7 (d.s. Å 2.7), were prepared by esterification of native starch with fatty acid chlorides. Our analyses, including elemental analysis, FTIR, contact angle, DSC, and TGA measurements confirmed the esterification reaction of starch and the degree of substitution. The ester group was found to act like an internal plasticizer, with an increase in the number and the size of fatty acyl chains grafted onto starch. These starch esters were mixed with low density polyethylene (LDPE) at various proportions in a Haake Rheomixer. Water and moisture absorption, thermal and mechanical properties, and biodegradation were investigated as a function of blend composition. The DODST2.7/LDPE blends showed, in general, better thermal stability and higher elongation, but lower tensile strength and water absorption, than did corresponding OCST/LDPE blends. The addition of starch esters to LDPE led to a very slow rate of biodegradation of these blends.
Polymer Degradation and Stability, 1998
Starch-starke, 2005
This study deals with the organic solvent-free synthesis of fatty acid esters of high-amylose mai... more This study deals with the organic solvent-free synthesis of fatty acid esters of high-amylose maize (amylomaize) starch by transesterification with lauric acid methyl ester using potassium laurate as catalyst. The process involves thermal pretreatment of amylomaize in order to swell the polysaccharide and increase its accessibility and reaction with the esterification reagent. The swelling degree (Q) was monitored by UV-Vis spectrophotometry and scanning electron microscopy (SEM), whilst the formation of a complex between amylose and potassium laurate was confirmed by X-ray diffraction and FTIR studies. The transesterification reaction was carried out at 190°C and a central composite design was used to obtain the corresponding contour plots with a second order model (y = β0 + β1 X1 + β2 X2 + β12 X1 X2 + β11 X1 X1 + β22 X2X2) and a confidence interval of 95%. The experimental design consisted of two independent variables, reaction time (2–6 h) and catalyst (2.2 – 33.8 meq catalyst per eq. glucose), and two dependent variables, the degree of substitution (DS) and the yield of the amylomaize starch ester (Y,%). Maximum transesterification of amylomaize starch (DS = 0.61) was obtained after 4:30 h at 190°C with an intermediate concentration of catalyst (18 meq per eq. glucose). Finally, the optimized results were extended to other starch sources and vegetable oils.
Journal of Applied Polymer Science, 1999
In the present article a series of low-density polyethylene (LDPE) blends with different amounts ... more In the present article a series of low-density polyethylene (LDPE) blends with different amounts of fatty esters of amylose and starch, were prepared in a Haake-Buchler Reomixer. The tensile as well as the dynamic thermomechanical (DMTA) properties of the blends were measured. It was found that as the amount of the esters increases in the blends, the tensile strength and especially the elongation at break decrease nonlinearly. Scanning electron microscopy (SEM) was used to assess the interfacial adhesion between LDPE and the corresponding esters. The incompatibility of the blends was also verified with DMTA and differential scanning calorimetry (DSC). From the biodegradation studies of the blends during exposure in activated sludge, it was found that all esters are biodegradable, although to a much lesser degree compared to pure strach. The biodegradation rate of the composites is relatively small due to the low biodegradation rate of the pure esters.
Journal of Applied Polymer Science, 1999
In the present article a series of low-density polyethylene (LDPE) blends with different amounts ... more In the present article a series of low-density polyethylene (LDPE) blends with different amounts of fatty esters of amylose and starch, were prepared in a Haake-Buchler Reomixer. The tensile as well as the dynamic thermomechanical (DMTA) properties of the blends were measured. It was found that as the amount of the esters increases in the blends, the tensile strength and especially the elongation at break decrease nonlinearly. Scanning electron microscopy (SEM) was used to assess the interfacial adhesion between LDPE and the corresponding esters. The incompatibility of the blends was also verified with DMTA and differential scanning calorimetry (DSC). From the biodegradation studies of the blends during exposure in activated sludge, it was found that all esters are biodegradable, although to a much lesser degree compared to pure strach. The biodegradation rate of the composites is relatively small due to the low biodegradation rate of the pure esters.
Journal of Applied Polymer Science, 1999
In the present study, a series of poly(ethylene succinate)/poly(1-caprolactone) block copolymers ... more In the present study, a series of poly(ethylene succinate)/poly(1-caprolactone) block copolymers were prepared by using a two step process. In the first step, poly(ethylene succinate) (PESu) was synthesized by the melt polycondensation process while in the second, block copolymers were prepared by ring opening polymerization of 1-caprolactone (1-CL) in the presence of stannous octoate. The copolymers were analysed with 1 H NMR spectroscopy and were confirmed to possess final compositions very similar to the initial feed compositions. An increase in the 1-CL content led to an increase in the molecular weights of the copolymer, while polydispersity was narrowed. In the DSC thermographs, two melting points were recorded for copolymers containing 75 and 50 mol% PESu, confirming that block copolymers were prepared. The incorporation of 1-CL content in macromolecular chains resulted in a substantial decrease of the crystallization rates of the copolymers. PESu is a brittle material due to its low molecular weight, while the copolymer containing 75 mol% 1-CL possesses sufficient tensile strength and elongation at break. Enzymatic degradation was performed using Rhizopus delemar lipase in a buffer solution at 37 8C. Biodegradation rates were mainly affected by the crystallinity of copolymers, rather than from their molecular weight. PESu and copolymer films were degraded into very small fragments after six months soil burial while polycaprolactone remained almost unaffected. q 2002 Published by Elsevier Science Ltd.
Journal of Applied Polymer Science, 1997
In the present study, starch octanoates OCST1.8 and OCST2.7 with degrees of substitution (d.s.) o... more In the present study, starch octanoates OCST1.8 and OCST2.7 with degrees of substitution (d.s.) of 1.8 and 2.7, respectively, and dodecanoate DODST2.7 (d.s. Å 2.7), were prepared by esterification of native starch with fatty acid chlorides. Our analyses, including elemental analysis, FTIR, contact angle, DSC, and TGA measurements confirmed the esterification reaction of starch and the degree of substitution. The ester group was found to act like an internal plasticizer, with an increase in the number and the size of fatty acyl chains grafted onto starch. These starch esters were mixed with low density polyethylene (LDPE) at various proportions in a Haake Rheomixer. Water and moisture absorption, thermal and mechanical properties, and biodegradation were investigated as a function of blend composition. The DODST2.7/LDPE blends showed, in general, better thermal stability and higher elongation, but lower tensile strength and water absorption, than did corresponding OCST/LDPE blends. The addition of starch esters to LDPE led to a very slow rate of biodegradation of these blends.
Starch-starke, 1999
French potato starch was supplied by INRA (Nantes, France). Octanoated dextrin (DS 8 2.9) and oct... more French potato starch was supplied by INRA (Nantes, France). Octanoated dextrin (DS 8 2.9) and octanoated starch (DS 8 2.7) were prepared by a modified method using pyri-132 Starch/Stärke 51 (1999) Nr. 4, S. 132-135