Aji Aji - Academia.edu (original) (raw)

Papers by Aji Aji

Research paper thumbnail of The effect of morphology and chemical characteristics of cellulose reinforcements on the crystallinity of polylactic acid

Journal of Applied Polymer Science, 2006

... The authors thank Fortum Oil and Gas Oy, Finland; Borregaard Chemcell, Norway; Scandinavian W... more ... The authors thank Fortum Oil and Gas Oy, Finland; Borregaard Chemcell, Norway; Scandinavian Wood Fiber AB, Sweden; and Rayonier, USA for supplying the materials. References. ... 8 Mathew, AP; Oksman, K.; Sain, M.; J Appl Polym Sci 2005, 97, 2014. ...

Research paper thumbnail of Optimization of the isolation of nanocrystals from microcrystalline cellulose by acid hydrolysis

Cellulose, 2006

The objective of this work was to find a rapid, high-yield process to obtain an aqueous stable co... more The objective of this work was to find a rapid, high-yield process to obtain an aqueous stable colloid suspension of cellulose nanocrystals/whiskers. Large quantities are required since these whiskers are designed to be extruded into polymers in the production of nano-biocomposites. Microcrystalline cellulose (MCC), derived from Norway spruce (Picea abies), was used as the starting material. The processing parameters have been optimized by using response surface methodology. The factors that varied during the process were the concentration of MCC and sulfuric acid, the hydrolysis time and temperature, and the ultrasonic treatment time. Responses measured were the median size of the cellulose particles/whiskers and yield. The surface charge as calculated from conductometric titration, microscopic examinations (optical and transmission electron microscopy), and observation of birefringence were also investigated in order to determine the outcome (efficiency) of the process. With a sulfuric acid concentration of 63.5% (w/w), it was possible to obtain cellulose nanocrystals/whiskers with a length between 200 and 400 nm and a width less than 10 nm in approximately 2 h with a yield of 30% (of initial weight).

Research paper thumbnail of Plasticized Waxy Maize Starch: Effect of Polyols and Relative Humidity on Material Properties

Biomacromolecules, 2002

The plasticizing effect of different polyols such as glycerol, xylitol, sorbitol, and maltitol on... more The plasticizing effect of different polyols such as glycerol, xylitol, sorbitol, and maltitol on waxy maize starch was investigated. The concentration of plasticizer was fixed at 33 wt % (dry basis of starch). The structure and mechanical performance of resulting films conditioned at different relative humidity levels were studied in detail. The effect of the plasticizer on the glass-rubber transition temperature (T g) and crystallinity was characterized using differential scanning calorimetry. It was found that T g decreases with increasing moisture content and decreasing molecular weight of the plasticizer. The water resistance of starch increased steadily with the molecular weight of the plasticizer and was directly proportional to the ratio of the end to total hydroxyl groups. As the molecular weight of the plasticizer increased, the brittleness of the dry system increased. However, the use of high molecular plasticizer allowed good mechanical properties of the moist material to be obtained in terms of both stiffness and elongation at break.

Research paper thumbnail of Morphological Investigation of Nanocomposites from Sorbitol Plasticized Starch and Tunicin Whiskers

Biomacromolecules, 2002

Nanocomposites were prepared from waxy maize starch plasticized with sorbitol as the matrix and a... more Nanocomposites were prepared from waxy maize starch plasticized with sorbitol as the matrix and a stable aqueous suspension of tunicin whiskers-an animal cellulose-as the reinforcing phase. The composites were conditioned at different relative humidity levels. The conditioned films were characterized using scanning electron microscopy, differential scanning calorimetry, water uptake experiments, and wide-angle X-ray scattering studies. Contrarily to our previous report concerning tunicin whisker filled glycerol plasticized starch nanocomposites (Macromolecules 2000, 33, 8344), the present system exhibited a single glass-rubber transition, and no evidence of transcrystallization of amylopectin on cellulose whisker surfaces and resultant antiplasticizing effects were observed. It was found that the glass-rubber transition temperature of the plasticized amylopectin matrix first increases up a whiskers content around 10-15 wt % and then decreases. A significant increase in crystallinity was observed in the composites by increasing either moisture content or whiskers content.

Research paper thumbnail of The effect of morphology and chemical characteristics of cellulose reinforcements on the crystallinity of polylactic acid

Journal of Applied Polymer Science, 2006

... The authors thank Fortum Oil and Gas Oy, Finland; Borregaard Chemcell, Norway; Scandinavian W... more ... The authors thank Fortum Oil and Gas Oy, Finland; Borregaard Chemcell, Norway; Scandinavian Wood Fiber AB, Sweden; and Rayonier, USA for supplying the materials. References. ... 8 Mathew, AP; Oksman, K.; Sain, M.; J Appl Polym Sci 2005, 97, 2014. ...

Research paper thumbnail of Optimization of the isolation of nanocrystals from microcrystalline cellulose by acid hydrolysis

Cellulose, 2006

The objective of this work was to find a rapid, high-yield process to obtain an aqueous stable co... more The objective of this work was to find a rapid, high-yield process to obtain an aqueous stable colloid suspension of cellulose nanocrystals/whiskers. Large quantities are required since these whiskers are designed to be extruded into polymers in the production of nano-biocomposites. Microcrystalline cellulose (MCC), derived from Norway spruce (Picea abies), was used as the starting material. The processing parameters have been optimized by using response surface methodology. The factors that varied during the process were the concentration of MCC and sulfuric acid, the hydrolysis time and temperature, and the ultrasonic treatment time. Responses measured were the median size of the cellulose particles/whiskers and yield. The surface charge as calculated from conductometric titration, microscopic examinations (optical and transmission electron microscopy), and observation of birefringence were also investigated in order to determine the outcome (efficiency) of the process. With a sulfuric acid concentration of 63.5% (w/w), it was possible to obtain cellulose nanocrystals/whiskers with a length between 200 and 400 nm and a width less than 10 nm in approximately 2 h with a yield of 30% (of initial weight).

Research paper thumbnail of Plasticized Waxy Maize Starch: Effect of Polyols and Relative Humidity on Material Properties

Biomacromolecules, 2002

The plasticizing effect of different polyols such as glycerol, xylitol, sorbitol, and maltitol on... more The plasticizing effect of different polyols such as glycerol, xylitol, sorbitol, and maltitol on waxy maize starch was investigated. The concentration of plasticizer was fixed at 33 wt % (dry basis of starch). The structure and mechanical performance of resulting films conditioned at different relative humidity levels were studied in detail. The effect of the plasticizer on the glass-rubber transition temperature (T g) and crystallinity was characterized using differential scanning calorimetry. It was found that T g decreases with increasing moisture content and decreasing molecular weight of the plasticizer. The water resistance of starch increased steadily with the molecular weight of the plasticizer and was directly proportional to the ratio of the end to total hydroxyl groups. As the molecular weight of the plasticizer increased, the brittleness of the dry system increased. However, the use of high molecular plasticizer allowed good mechanical properties of the moist material to be obtained in terms of both stiffness and elongation at break.

Research paper thumbnail of Morphological Investigation of Nanocomposites from Sorbitol Plasticized Starch and Tunicin Whiskers

Biomacromolecules, 2002

Nanocomposites were prepared from waxy maize starch plasticized with sorbitol as the matrix and a... more Nanocomposites were prepared from waxy maize starch plasticized with sorbitol as the matrix and a stable aqueous suspension of tunicin whiskers-an animal cellulose-as the reinforcing phase. The composites were conditioned at different relative humidity levels. The conditioned films were characterized using scanning electron microscopy, differential scanning calorimetry, water uptake experiments, and wide-angle X-ray scattering studies. Contrarily to our previous report concerning tunicin whisker filled glycerol plasticized starch nanocomposites (Macromolecules 2000, 33, 8344), the present system exhibited a single glass-rubber transition, and no evidence of transcrystallization of amylopectin on cellulose whisker surfaces and resultant antiplasticizing effects were observed. It was found that the glass-rubber transition temperature of the plasticized amylopectin matrix first increases up a whiskers content around 10-15 wt % and then decreases. A significant increase in crystallinity was observed in the composites by increasing either moisture content or whiskers content.