A. M. Sarwaruddin Chowdhury

Grafting of 2-Ethylhexyl Acrylate with Urea on to Gelatin Film by Gamma Radiation

Gelatin films were prepared by dissolving gelatin granules in hot distilled water (90°C) followed by casting. Tensile strength (TS), tensile modulus (TM) and elongation at break (Eb %) of the films were found to be 27.0 MPa, 100 MPa and 4%, respectively. Gelatin films were irradiated under Co-60 source at different doses (50-1000 krad) and it was found that TS and TM of the films increased up to 48% and 120%, respectively at 250 krad dose. Urea (1–5 wt%) was added to the gelatin solution and films were prepared by casting, then irradiated and found that TS of the 2% urea containing gelatin film was 44.3 MPa which is about 64% enhancement of TS compared to raw gelatin films at 100 krad. Gelatin-urea films were then soaked in 1–10 wt% of EHA (2-Ethylhexyl acrylate) solutions at varying soaking time and irradiated under gamma radiation up to 500 krad. The highest TS and Eb were found to be 57 MPa and 11%, respectively for the 3% EHA and 3 min soaking time at 100 krad radiation dose.

Characterization of Poly(Vinyl Alcohol) and Poly(Vinyl Pyrrolidone) Co-polymer Blend Hydrogel Prepared by Application of Gamma Radiation

Hydrogel is prepared from a poly(vinyl pyrrolidone) (PVP) and poly(vinyl alcohol) (PVA) blend solution by gamma radiation with a 60Co λ source at room temperature. Properties of the prepared hydrogel, such as gel fraction, gel strength swelling ratio, equilibrium water content, and water absorption in room temperature, were investigated. Blending hydrogel with PVP and PVA obviously increased the gel strength and decreased the swelling ratio of hydrogel. It was observed that the gel fraction increased while the swelling ratio and water content decreased with increased radiation dose, but gel strength increased up to a certain radiation dose and then decreased. The percentage of water absorption at room temperature increased with time but after a certain time it became steady and decreased with radiation dose.

Studies on the cycling, processing and programming of an industrially applicable shape memory polymer Tecoflex® (or TFX EG 72D)

The present investigations were undertaken to find out whether and how often cycling, processing and programming can be repeated, whether repeated programming affects the one way effect and how much irreversible strain the shape memory polymeric material accumulates at a particular temperature. The effect was investigated in dependence of different stress levels, and the effect of both recovery temperature and recovery time was considered. As a model material the commercially and industrially applicable amorphous shape memory polymer Tecoflex® was examined and subjected to 50 programming cycles. Tecoflex® is characterized by a glass transition temperature, Tg, of 74 °C, above which it looses all its strength. During tensile testing at 20 °C (T < Tg), stresses a steady increase to 26 MPa as strains approached the rupture strain of 25%. It is observed that at 60 °C (T < Tg, but near Tg) the material can be strained to more than 2500% before rupture occurs while stresses slowly increase to values less than 0.3 MPa. It turns out that programming, cooling, unloading and heating to trigger the one way effect causes an increase of irreversible strain that is associated with a corresponding decrease of the intensity of the one way effect during the first thermomechanical cycles.

Effect of Natural Antioxidant (Diospyros peregrina) on the Aging Properties of Radiation Vulcanized (γ-Radiation) Natural Rubber Latex Film

Natural rubber latex and various concentration of natural antioxidant were blended in different ratios and irradiated at various absorbed doses by gamma rays from Co-60 source at room temperature. The aqueous extraction of Diospyros peregrina was used as natural antioxidant. It was found that the addition of different concentration of natural antioxidant into natural rubber latex improve the aging property of the film. Decreasing in tensile strength of rubber film with 10 phr natural antioxidant and 15 kGy radiation dose after 24 hours aging at 100°C was 9.34% compared to 13.89% for film without natural antioxidant. The tensile strength, tear resistance and modulus at 500% elongation of the rubber film were found to be optimum at 15 kGy radiation dose and with 10 phr natural antioxidant. Elongation at break, permanent set and swelling ratio decreases with the increasing absorbed radiation dose as well as the concentration of the natural antioxidant.

Fabrication and Mechanical Characterization of Calcium Alginate Fiber-Reinforced Polyvinyl Alcohol Based Composites

Calcium alginate fibers were prepared from sodium alginate by extruding aqueous sodium alginate solution (4% by weight) into a calcium chloride (2% by weight) bath. Water uptake and mechanical properties of the calcium alginate fiber were investigated. Water uptake tests of calcium alginate showed that it absorbed 50% of water within a minute and indicated strong hydrophilic nature. Polyvinyl alcohol (PVA)-based calcium alginate fiber reinforced unidirectional composites (10% fiber by weight) were fabricated by compression molding. Tensile strength (TS), tensile modulus (TM), bending strength (BS), bending modulus (BM) and impact strength (IS) of the PVA matrix and the composite were evaluated. TS, BS, TM, and BM of the PVA matrix were found 10, 18, 320 and 532 MPa, respectively. TS and BS of the PVA based composite were found to be 16 and 27 MPa, respectively, which were 60 and 50% higher than that of the PVA matrix. TM and BM of the composite were found to be 620 and 1056 MPa, respectively, which were improved by 94 and 98% over the matrix material. Degradation tests of the composites were performed for up to 2 months in soil medium and found that composites lost almost 50% of its original mechanical properties. The interfacial properties of the composite were also investigated by using the single fiber fragmentation test (SFFT).

Stress-Strain Behavior of Shape Memory Polymers by 1WE Method: Application to Tecoflex®

Thermomechanical cycles including programming, cooling, unloading and heating to trigger the 1WE were examined for a shape memory polymer (SMP), Tecoflex® (TFX EG-72D). Cycles were performed at 60°C with 50% and 225% strains and the recovery time of 10 min. Strains evolving with time were estimated during the thermomechanical treatments for the total 44 cycles using 50% strains and the total 50 cycles using 225% strains. Recovery ratios for 50% strains and 225% were also estimated. It turns out that programming, cooling, unloading and heating to trigger the 1WE causes an increase of irreversible strain and is associated with a corresponding decrease of the intensity of the 1WE in particular during the first thermomechanical cycles. In parallel scanning electron microscopic study using secondary electron imaging shows a very slight wavy surface structure evolved during cycling.

Modification of Jute Fibre by Sulphonation for Diverse Textile Use

Jute fibre is, by nature, hard and coarse. Treated with a sulphite of sodium in its neutral solution at about 165°C some of its properties were found to improve as lignin undergoes sulphonation reaction. Incrustation due to lignin is loosened, dislocated and partially removed as soluble lignin sulphonates come out in solution, but a major portion of them condenses to form solid lignin sulphonates remaining insoluble in tbe fibre and imparting new properties to fibres. Carbobydrate materials like hemicelluloses are also removed proportionately with the soluble lignin sulphonates. The rate of delignification as well as condensation of lignin sulphonates in the fibre was found to be dependent upon the degree of sulphonation of the fibre. It is seen that the sulpho-groups increase rapidly at the beginning of the treatment. The ratios of acidic sulphur to total sulphur lie within the limit of about 0.75, which means that about 25% of the sulphur was non-acidic in the sulphonated jute fibre.

Studies on Swelling and Absorption Properties of the IrradiatedPolyvinyl Alcohol (PVA)/Kappa-Carrageenan Blend Hydrogels

A series of hydrogels were prepared from an aqueous mixture of Poly vinyl alcohol (PVA) and Kappa-carrageenan (KC) and irradiated the mixture at 25 kGy radiation dose with γ-radiation from 60Co γ source at room temperature (25°C). The effects of KC on the properties, such as gel fraction, swelling ratio (e.g., in distilled water, in NaCl solution with different concentration, buffer solution with different pH), water absorption, water desorption, moisture absorption and uptake of metal ion from aqueous solution of the prepared hydrogels were investigated. Incorporation of KC into the PVA obviously influences the properties of hydrogels. It is found that the gel fraction of the prepared hydrogel decreased but swelling ratio increased with increase in concentration of Kappa-carrageenan. Swelling properties in NaCl decreased with increased concentration of NaCl in aqueous solution. Swelling of the blend gel in buffer increased with the increase in pH. Water absorption properties showed that maximum absorption occurred within 24 hrs and then increasing trend of water absorption was insignificant. Water desorption is very fast upto 48 hrs and then attained a plateau value. The maximum moisture absorption occurred within 48 hrs and then the absorption was insignificant. Kappa-carragenan influences to uptake of metal (Cu+2) by PVA / KC blend hydrogel with time.

Effect of Sodium Bicarbonate on the Mechanical and Degradation Properties of Short Jute Fiber Reinforced Polypropylene Composite by Extrusion Technique

Short jute fibers and the pellets of polypropylene (PP) were compounded to make composites with the help of an extruder followed by compression molding. The mechanical properties of the composites increased with the increase of fiber content up to 20%, then decreased while the jute content varied from 5 to 30 wt%. Composites with varying percentages (5 to 20%) of sodium bi-carbonate at constant (20%) jute content were made by same process. The mechanical properties, soil degradation tests, and the water uptake capacity of the composites were investigated properly. Also, the density of the composite was reduced up to 21.54%.

Study on the Properties of Radiation Induced Acrylamide Grafted Natural Rubber Latex Film

Grafted rubber films were prepared by mixing various proportions of acrylamide with natural rubber latex (NRL) with varying proportions by gamma radiation from Co-60 source at room temperature. Tensile strength, tear strength, elongation at break, permanent set, and swelling ratio, gel content and degree of grafting were measured. Tensile strength, tear strength, gel content and degree of grafting were found increasing with absorbed dose, as well as the proportion of monomer concentration and the optimum dose was found 12 kGy from the results. Elongation at break, permanent set, and swelling ratio of grafted rubber decreases with increase in absorbed dose, as well as proportion of grafted rubber.