Satya Panigrahi

Biodegradable Polymers: Past, Present, and Future

In recent years, there has been a marked increase in interest in biodegradable materials for use in packaging, agriculture, medicine, and other areas. In particular, biodegradable polymer materials (known as biocomposites) are of interest. Polymers form the backbones of plastic materials, and are continually being employed in an expanding range of areas. As a result, many researchers are investing time into modifying traditional materials to make them more user-friendly, and into designing novel polymer composites out of naturally occurring materials. A number of biological materials may be incorporated into biodegradable polymer materials, with the most common being starch and fiber extracted from various types of plants. The belief is that biodegradable polymer materials will reduce the need for synthetic polymer production (thus reducing pollution) at a low cost, thereby producing a positive effect both environmentally and economically. This paper is intended to provide a brief outline of work that is under way in the area of biodegradable polymer research and development, the scientific theory behind these materials, areas in which this research is being applied, and future work that awaits.

Two-dimensional surface properties of an antimicrobial hydantoin at the air–water interface: An experimental and theoretical study

5,5-Acetamidomethyl-5-methylimidazolidine-2,4-dione shows antimicrobial activity against bacteria at millimolar concentrations well above its critical micellar concentration (cmc). Two-dimensional surface properties were investigated using Langmuir Film Balance to understand the membrane-active nature and nanomaterial behavior of this hydantoin derivative. Hydantoin forms an expanded nanofilm at air-water interface. The maximum limiting surface area (A(0)) and collapse pressure (pi(c)) are dependent on hydantoin concentration. Hydantoin undergoes a change in orientation at the interface, in the pressure region 2.5 and 7.5 mNm(-1), corresponding to surface areas 51-15 and 41-12A(2)molecule(-1), respectively. A large collapse pressure (pi(c)) in LB film indicates a role for hydrophobic interactions in the self-assembly of hydantoin. Surface areas computed using Connolly method, are in good agreement with the experimental results. Monolayer studies suggest a dispersed state for hydantoin when its concentration is below cmc, suggesting a mechanism for the observed bacteriostatic activity of hydantoin. In the present study, it has been found for the first time that the minimum inhibitory concentration (MIC) of the hydantoin is very close to its cmc.

Extrusion Compounding of Flax-Fiber-Reinforced Polyethylene Composites: Effects of Fiber Content and Extrusion Parameters

The objectives of this study were to examine the effects of fiber content and extrusion parameters on flax-fiber-reinforced polyethylene composites and to determine the optimum values for the same. The flax fibers were chemically pretreated, ground, and mixed with powdered polyethylene. The mixture was extruded, pelletized, ground, rotationally molded, and cut into test specimens for testing and characterization. Superposition surface methodology was then applied as optimization technique. Optimum values were fiber content = 6.25%, barrel zone temperatures = 75, 117, 127, 137, and 147 °C, and screw speed = 118 rpm for linear low-density polyethylene (LLDPE) composites; and fiber content = 5.02%, barrel zone temperatures = 75, 118, 128, 138, and 148°C, and screw speed = 126 rpm for high-density polyethylene (HDPE) composites.

A kinetic study of xylose recovery from a hemicellulose-rich biomass for xylitol fermentative production

Abstract Hemicellulose in the complex structure of lignocellulosic substances is mainly composed of xylan which is a polymer based on monosaccharide xylose. Using acidic or enzymatic hydrolysis, hemicellulose can be depolymerized into its constituent monomer. The kinetics of hemicellulose depolymerization and decomposition in oat hull was investigated under moderate pressures with catalyst (H2SO4) concentration up to 0.55 N and temperatures of up to 130 °C for a total residence time of 150 min. Different trends of recovery or generation and kinetic mechanisms obtained for the components in the hydrolysate which could be described by different kinetic models, that is, a single-phase kinetic mechanism with product decomposition (two-step sequential reaction) could describe xylose generation. However, generation of arabinose, furfural, and acetic acid followed a single-phase mechanism with no decomposition (one-step reaction). Generation of glucose in the hydrolysate followed a biphasic mechanism due to the fast- and slow-releasing fractions into the liquid phase which was apparently with no decomposition. A pentose recovery of almost 80% was achieved under optimal conditions. Parameters of xylitol bioproduction indicated that a xylitol/xylose conversion yield of 0.80 g/g is achievable from the concentrated hydrolysate with no complementary treatment proving its low toxicity compared to other hemicellulose resources.

Xylitol Production in Aerated Free- and Immobilized-cell Systems

Abstract. This study was conducted to evaluate the performance of free- and immobilized- cell systems in xylitol production process using Candida guilliermondii as the biocatalyst and a hemicellulosic hydrolysate derived from the hydrolysis of oat hull biomass as the medium. Both biotransformation performance and cell regeneration were greatly dependent on oxygen mass transfer coefficient (k L a). However, the process using immobilized biocatalyst demonstrated to be more flexible to the level of aeration rate. Application of the bio-based composite as the cell support in xylitol bioconversion process was examined and the results indicated that the composition of the support could be effective on the xylitol yield and productivity in repeated batch bioconversion process.

Sorption Isotherms of Natural and Chemically Modified Biofiber

Biofiber-based composites are emerging as an alternative to synthetic fiber reinforced composites in different kinds of products and applications due to some advantages such as low density, low abrasive behaviour, good thermal insulation and biodegradability of the biofibers. However their sensitivity to thermal degradation and hygroscopic property as well as incompatibility with polymers is restrictive. Therefore, more knowledge on their hygroscopic behaviour could be helpful in appropriate employment of biofibers in polymeric matrices and manufacturing biocomposites. The purpose of this study is to investigate the influence of chemical pretreatments (mercerization, silinization and bleaching) and environmental conditions (temperature and relative humidity (RH)) on water sorption isotherms of flax fiber. Finally, empirical and mathematical models are to be employed to model adsorption and desorption equilibrium isotherms of the materials.

Utilization of Flax Fiber with Recycled Tire Rubber in Biocomposite Material

Flax, which is known for its linens and oils that are used for industrial products, can also be utilized as a cost effective and environmentally acceptable approach to the creation of a partially biodegradable molded grade biocomposite. Biocomposite material is investigated by combining recycled tire rubber and flax with linear low density polyethylene (LLDPE). The manufacturing process which we used to fabricate our biocomposite product included Extrusion and Compression Molding. Our study involved optimizing and studying the composition percentages of the compounds being used. Moreover, we also observed the properties of the product by using tensile test, tearing test, water absorption test, hardness test and Differential Scanning Calorimetry (DSC method).

Frictional properties of natural and chemically-treated flax fibers

Frictional properties of the natural and treated flax fiber may be required in the design of storage structures, processing, and handling equipment for the fibers used in biocomposites and other applications. The frictional properties (internal friction, static friction, and dynamic friction coefficients) of chemically-treated and natural flax fibers were determined using Wykeham Farrance shear box apparatus. From statistical analysis, the applied normal pressure did not appear to influence the frictional properties of the flax fiber samples. Chemical treatment significantly increased the frictional properties of the flax. The frictional properties were affected significantly by the alkaline treatment compared to other samples. The effective internal friction coefficient values of the whole flax samples ranged from 0.365 to 0.745 and values for the ground samples varied from 0.424 to 0.819. For the whole fiber samples the effective static friction values ranged from 0.155 to 0.244, and the values for the ground fiber samples varied from 0.132 to 0.244. For the whole fiber samples, the dynamic friction coefficient values ranged from 0.131 to 0.179, and the values for the ground fiber samples varied from 0.123 to 0.197.

Microwave and microwave-vacuum drying kinetics of field peas

Field pea (Pisum sativum L.) is a leguminous crop high in protein and complex carbohydrates and low in fat. Field pea is harvested at 18 to 20% moisture and must be dried to lower moisture contents for safe storage and grinding to be used in food applications. The drying kinetics of field pea using microwave, microwave-vacuum and convective drying were investigated. Three microwave power levels P10, P8 and P6 corresponding to 745, 588 and 455 W, respectively and two vacuum pressures 85 and 68 kPa were used. The times required to dry field pea samples from initial moisture content of 21.1% to below 10% decreased with increasing power levels. Higher drying times were achieved when higher vacuum pressure of 85 kPa was combined with the microwave power levels compared to combined vacuum pressure of 68 kPa and microwave power levels, as well as microwave power levels alone. However, the decrease in drying time from using combined higher vacuum pressure and microwave power was marginal. There was no difference between the drying times for samples dried at microwave power levels P10, P8 and P6 and the corresponding drying at combined vacuum pressure of 68 kPa and power levels P10, P8 and P6. Page and modified Pages models provided best fit models for the microwave, microwave-vacuum and convective drying data with higher R2 and lower SE compared Newton and Wang and Singh models. The drying rate constant (k) values ranged from 0.0088 to 0.0245 min-1 for the Pages model and for the modified Pages model, they varied from 0.0484 to 0.0916 min-1. The n values ranged from 1.3079 to 1.8875 for both Page and modified Pages models.

The Effects of Chemical Treatments of Flax Fiber on Some Engineering Properties of Biocomposite

Abstract: Flax fiber, produced through a conventional scotching mill, was washed using a commercial detergent and then it was chemically treated using silane, benzoyle and peroxide. The chemically treated fibers were dried by an air-cabinet drier at 70 °C. The dried fiber were ground and truly mixed with HDPE at a ratio of 10% flax fiber and 90% HDPE. After extruding and pelleting, the mixture was fed through a rotational molding machine and composite plates were produced. The resulting composites were tested for their various mechanical properties using standard ASTM procedures. The test results indicated that the mechanical strength of the composites was higher than the plates made from HDPE, however there was no significant difference between the mechanical strength of composites produced from various chemical treatments. The optical properties of the composites were investigated using NIR spectroscopy. The % of reflectance of the NIR at a wide range of wavelength indicated that HDPE plates were easily distinguishable, however the chemically treated composites and untreated composites were not distinguishable from each other using this technique.