B. Ramaraj

Sodium Alginate and Poly(ethylene glycol) Blends: Thermal and Morphological Behaviors

Sodium alginate (SA) was blended with varying amounts of poly(ethylene glycol) (PEG) viz., 10, 20, 30, 40 and 50 wt % by using water as a solvent. The obtained SA/PEG blends have been characterized for thermal behavior by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) and surface morphology by scanning electron microscopic (SEM) methods. DSC analysis indicates the increase in glass transition temperature (Tg) of the blends with an increase in PEG content in the blend, which is due to chain entanglement. TGA results reveal the enhancement of thermal stability of SA/PEG blends in terms of the onset of degradation and percentage of weight loss. SEM photomicrographs shows the two phase morphology. This result indicates the immiscible nature of the SA/PEG blends.

Graft polymerization of p-dioxanone onto polyhydroxyethylaspartamide through ring-opening polymerization using organometallic and enzyme catalysts

The grafting of poly(p-dioxanaone) (PPDO) onto β-poly(N-2-hydroxyethyl)-DL-aspartamide (PHEA) was achieved, first, by synthesis of polysuccinimide (PSI) from DL-aspartic acid through thermal condensation polymerization, and then, followed by aminolysis of PSI to form PHEA with hydroxyl end groups, and finally the PPDO was grafted onto PHEA through these hydroxyl end groups by ring-opening polymerization (ROP) of PDO in the presence of tin octoate [Sn(Oct)2] and Candida Antarctica Lipase B (Novozyme 435) catalysts. Evidence of grafting was obtained by comparing Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD) analysis, polarized optical microscopy (POM), proton nuclear magnetic resonance (1H–NMR) spectroscopy, and solubility characteristics of PHEA with PPDO-grafted copolymers (PHEA-g-PPDO). The FT-IR spectroscopic analysis reveals the formation of ester linkage between PPDO and hydroxyl end groups of PHEA. TGA analysis shows a quite different thermal profile for grafted polymers. DSC and XRD results reveal the existence of graft copolymer in two different crystalline forms. POM shows banded spherulitic morphology for the graft copolymers. The grafting of PPDO was further confirmed by 1H–NMR. Eventhough, graft copolymer was obtained by both these methods, the graft copolymer obtained by enzyme catalyzed ROP shows higher crystalline order, better spherulitic morphology, and solubility characteristics than that of the graft polymer obtained by organometal catalyzed ROP.

Effect of ethylene vinyl acetate on physico-mechanical and thermal properties of polypropylene and starch biocomposites

The aim of this research is to investigate the effects of ethylene vinyl acetate (EVA) as compatibilizer on physico-mechanical and thermal properties of polypropylene (PP)/starch composites. PP/starch composites were prepared by the extrusion of PP resin with potato starch in co-rotating twin-screw extruder by varying starch content from 5 to 20%, where the EVA content was 10 wt% based upon potato starch. It was found that with the increase in starch content from 0 to 20% in the PP matrix, the tensile elongation increased from 19.77 to 32.0%, moisture content increased from 0.013 to 0.062%, water absorption increased from 0.035 to 0.181% and density increased from 0.912 to 0.985 g/cm3, however, the tensile, flexural and impact properties, Rockwell hardness, melt flow index and vicat softening point were found to decrease linearly. Similarly, the incorporation of starch with EVA has reduced the melting temperature of PP matrix from 162.3 to 158.55°C, the heat of fusion (▵H f) of PP matrix decreased from 66.52 to 27.05 J/g and so is the percentage crystallization, decreased from 31.83 to 21.45% with increase in starch content from 0 to 20 wt% in the PP matrix.