Graft copolymerization of acrylonitrile onto acetylated jute fibers

Graft copolymerization of acrylonitrile (AN) onto acetylated chemically modified jute was carried out in the temperature range 40–60°C using V⁵⁺-cyclohexanone redox initiator system. The effects of temperature, time, concentrations of metal ion (V⁵⁺), monomer (AN), cyclohexanone, some inorganic salts, and organic solvents on percent grafting have been studied. IR spectra of acetylated chemically modified jute and grafted jute have been taken, and their characteristic bands have been identified. Grafting has improved the thermal stability and also the lightfastness rating of jute fibers dyed with basic dyes.     

The Effects of Process Engineering on the Performance of PLA and PHBV Blends

The effects of process engineering in the fabrication of PHBV, PLA and their blends prepared by melt blending are studied. The elongation of an optimized blend can be improved by 148 and 250% over the virgin PHBV and PLA polymers, respectively. DSC shows that the two polymers are immiscible in blends of any composition. The crystallinity of PHBV is hindered by the presence of PLA. UV‐Vis demonstrates the opacity of the blend with incorporation of PHBV to the PLA phase. The observed tensile modulus of the optimized sample is compared with theoretical values from the rule of mixtures. Gordon‐Taylor's equation is applied on the glass transition temperatures for theoretical modeling to explain the miscibility of the polymers.

     

Structure and properties of compatibilized blends of polyamide-6 and ABS

Mechanical and Morphological properties of polyamide-6/ABS blend systems, compatibilized by styrene-maleic anhydride (SMA) copolymer, have been studied. The strength, modulus, and impact properties improved upon the addition of SMA. Morphological studies, using small angle light scattering, polarizing microscopy, and scanning electron microscopy, showed that SMA acts as a compatibilizer for the above system. © 1993 John Wiley & Sons, Inc.     

Polybutylene terephthalate/high-density polyethylene alloys. I. Morphological studies

Polybutylene terephthalate (PBT) is a commercially successful thermoplastic polyester but has certain drawbacks such as low impact strength and low melt strength. An attempt has been made to modify the properties of PBT by blending it with polyolefin such as highdensity polyethylene (HDPE). Since PBT and HDPE are incompatible, an ionomer has been used as a compatibilizer to form an alloy. Alloys of PBT and HDPE with varying amounts (2-8%) of ionomer were prepared by melt blending. The ultimate mechanical properties improved significantly on the addition of the ionomer due to an increase in interfacial adhesion between PBT and HDPE. DSC studies show that the presence of ionomer facilitated the crystallization of PBT in the alloy. DMTA studies show that more of PBT (amorphous) is going in to the HDPE-rich phase in the presence of ionomer. The morphology of the alloys was studied using scanning electron microscopy (SEM), polarizing microscopy (PM), and small-angle light scattering (SALS). They showed improved dispersion of HDPE domains in PBT matrix with increasing ionomer content and change in the type of superstructure on adding the ionomer. It has been shown that an alloy of PBT and HDPE with improved mechanical properties and homogeneous morphology can be made with use of ionomer as a compatibilizer. Such alloys are cost effective and can find use in several engineering applications.     

Graft copolymerization of acrylonitrile and methacrylonitrile onto gelatin by mutual irradiation method

In order to improve upon certain properties of gelatin graft copolymerization of acrylonitrile (AN) and methacrylonitrile (MAN) onto gelatin has been studied in aqueous medium using γ rays as a source of initiation. Optimum conditions for affording maximum percentage of grafting have been evaluated as a function of various reaction parameters. The grafted polyacrylonitrile (PAN) was isolated from the graft copolymer by acid hydrolysis, and the average molecular weight (M_v) of the isolated polymer has been determined viscometrically. The graft copolymers were characterized by IR spectroscopic methods and thermogravimetric analysis (TGA). Acrylonitrile was found to be more reactive than methacrylonitrile toward graft copolymerization. © 1994 John Wiley & Sons, Inc.     

Crystallization of poly(3‐hydroxybutyrate) by exfoliated graphite nanoplatelets

Poly(3‐hydroxybutyrate) (PHB) has been shown to be efficiently nucleated by exfoliated graphite nanoplatelets (xGnP). The nucleating effect of xGnP was investigated using differential scanning calorimetry, optical microscopy and atomic force microscopy. Nonisothermal crystallization of PHB from the melt required lower activation energies for PHB containing 1 wt % and 3 wt % xGnP (?214 and ?102 kJ/mol respectively) than for pure PHB (?60 kJ/mol). A kinetic study of the PHB/xGnP crystallization employing a modified form of the Avrami equation revealed that the presence of xGnP increased the PHB crystallization temperature, as well as the crystallization rates, and generated smaller and more numerous spherulites. Optical microscopy and atomic force microscopy confirmed the incorporation of xGnP into the lamellar structure of the PHB spherulites and provided insight into the influence of xGnP on spherulite size and lamellae thickness. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Viscometric studies of starch-g-polyacrylamide composites

Composites of starch-g-polyacrylamide, starch, and polyacrylamide have been prepared by gamma radiation-initiated polymerization of acrylamide in the presence of starch in aqueous medium. The polymerization was studied as a function of the (i) amount of water (ii) monomer concentration, and (iii) total dose. The optimum conditions for maximum conversion of the monomer to homopolymer and graft copolymer have been evaluated. Percentage of grafting of polyacrylamide could not be determined precisely as both the homopolymer and the graft are soluble in common solvents and all attempts to separate the graft from the homopolymer were unsuccessful. However, the formation of the starch-g-polyacrylamide copolymer was confirmed by the turbidimetric studies using acetone as a nonsolvent. The products of polymerization of acrylamide in the presence of starch consisted of unreacted starch, starch-g-polyacrylamide, and polyacrylamide and is referred to as the composite. Acrylamide was also polymerized in the absence of starch using γ-rays as means of initiation and the optimum conditions for maximum conversion of acrylamide to polyacrylamide have been evaluated. Viscosity behavior of the composite and polyacrylamide was studied in aqueous medium at 30±0.04°C. The reduced specific viscosity of the aqueous solution of acrylamide and the composite as well was found to increase with increasing dilution, the effect being more pronounced in the composite. This tends to indicate that both the homopolymer and the composite behave as polyelectrolytes. An attempt has been made to explain the polyelectrolytic behavior of the homopolymer and the composite. © 1993 John Wiley & Sons, Inc.     

Electrodeposition of nickel in the presence of Al<Superscript>3+</Superscript> from sulfate baths

The effect of Al³⁺ on the cathodic current efficiency, deposit morphology, crystallographic orientations and polarisation behaviour of the cathode during electrodeposition of nickel from acidic sulfate solutions was investigated. Higher concentration of Al³⁺ (>10 mg dm^–3) significantly deteriorated the surface quality of the nickel deposit as well as the current efficiency. X-ray diffraction studies revealed that the (200) plane was the most preferred crystal plane and was not affected by the presence of varying concentration of Al³⁺ in the electrolytic bath. The presence of Al³⁺ caused polarisation of the cathode, which increased with increasing Al³⁺ concentration. The effect of Al³⁺ on the electrokinetic parameters: Tafel slope (b), transfer coefficient () and exchange current density (i₀) were also investigated.     

Surface modification of coir fibers. II. Cu(II)‐ IO initiated graft copolymerization of acrylonitrile onto chemically modified coir fibers

A study of the graft copolymerization of acrylonitrile (AN) onto chemically modified coir fibers was carried out using a CuSO₄ and NaIO₄ combination as the initiator in an aqueous medium in a temperature range of 50–70°C. The graft yield was influenced by the reaction time, temperature, concentration of CuSO₄, concentration of NaIO₄, and monomer concentration. Grafting was also carried out in the presence of inorganic salts and organic solvents. A combination of copper(II) and sodium periodate (Cu²⁺‐IO) in an aqueous medium with an IO concentration of 0.005 mol L^?1 and a Cu²⁺ concentration of 0.004 mol L^?1 produced optimum grafting. The chemically modified and AN grafted fibers were characterized by FTIR and scanning electron microscopy (SEM). The SEM studies revealed that grafting not only takes place on the surface of the fibers but also penetrates the fiber matrix. The tensile properties like the maximum stress at break and extension at break of untreated, chemically modified, and AN grafted coir fibers were evaluated and compared. The extent of absorption of water of untreated, chemically modified, and grafted coir fibers was determined. It was found that grafting of AN imparts hydrophobicity onto coir fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 75–82, 2002; DOI 10.1002/app.10221     

Centreline defects in strips produced through thin slab casting and rolling

Segregation in conventional slabs has been the topic of multiple researches; the centreline segregation in thin slabs has not been explicitly reported in published literature. However, a centreline band (defect) is invariably observed on macroetching high-manganese (>1?wt-%) strips from thin slab casting and rolling route of TATA Steel, Jamshedpur. A study was conducted to establish the exact nature of centreline defects and correlate with observation in the corresponding slab. Presence of second phases at the centreline due to heavy manganese enrichment was observed to be the source of defect band. In summary, this paper establishes a direct correlation between defects in hot-rolled strips and macrosegregation in thin slabs and highlights countermeasures taken to address the defect.