A comparative study of aging characteristics and thermal stability of oil palm ash,silica, and carbon black filled natural rubber vulcanizates

Filler‐filled natural rubber (NR) vulcanizates were prepared by conventional laboratory‐sized two roll mills and cured using sulfuric system. The effect of thermal aging on physical properties and thermogravimetric analysis (TGA) of oil palm ash (OPA) and commercial fillers (i.e., silica vulkasil C and carbon black N330)‐filled NR vulcanizates at respective optimum loading and equal loading were studied. Before aging, the OPA‐filled vulcanizates showed comparable optimum strength as carbon black‐filled vulcanizates. The hardening of aged filler‐filled NR vulcanizates happened after aging, thereby tensile strength and elongation at break reduced while the modulus increased. Fifty phr carbon black‐filled vulcanizates showed better retention in tensile properties as compared to silica (10 phr) and OPA (1 phr). This was attributed to the addition of different filler loading and this finding was further explained when equal loading of filler‐filled vulcanizates was studied. Fourier transform infra‐red analysis showed chemical structure had changed and tensile fractured surface exhibited smooth appearance due to the deterioration in tensile properties after aging. TGA also denoted the thermal stability was depending on the amount of filler loading. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4474–4481, 2013     

Structural and Optical Properties of Lead-Boro-Tellurrite Glasses Induced by Gamma-Ray

Spectrophotometric studies of lead borotellurite glasses were carried out before and after gamma irradiation exposure. The increasing peak on the TeO₄ bi-pyramidal arrangement and TeO₃₊₁ (or distorted TeO₄) is due to augmentation of irradiation dose which is attributed to an increase in degree of disorder of the amorphous phase. The structures of lead tellurate contain Pb₃TeO₆ consisting of TeO₃ trigonal pyramid connected by PbO₄ tetragonal forming a three-dimensional network. The decrease of glass rigidity is due to irradiation process which is supported by the XRD diffractograms results. The decreasing values of absorption edge indicate that red shift effect occur after irradiation processes. A shift in the optical absorption edge attributed to an increase of the conjugation length. The values of optical band gap, E_opt were calculated and found to be dependent on the glass composition and radiation exposure. Generally, an increase and decrease in Urbach’s energy can be considered as being due to an increase in defects within glass network.     

Gelling of microbial transglutaminase cross-linked soy protein in the presence of ribose and sucrose

Soy protein isolate (SPI) was incubated with microbial transglutaminase (MTGase) enzyme for 5 (SPI/MTG(5)) or 24 (SPI/MTG(24)) h at 40 °C and the cross-linked SPI obtained was freeze-dried, and heated with 2% (w/v) ribose (R) for 2 h at 95 °C to produce combined-treated gels. Longer incubation period resulted in more compact and less swollen SPI particle shape when reconstituted with sugar solution. Thus, this MTGase treatment affected samples in terms of flow behaviour and gelling capacity. Rheological study showed different gelling profiles with the cross-linking treatments and combined cross-linked SPI gave a higher G′ value compared to single treated samples. These are due to the formation of additional ε-(γ-glutamyl)lysine bonds and “Maillard cross-links” within the SPI protein network during the MTGase incubation and heating in the presence of ribose (i.e. reducing sugar). Network/non-network protein analysis found that network protein increased with cross-linking treatment, which also resulted in different SDS–PAGE profiles. As in non-network protein fraction, A₄ subunit was suggested to become part of the network protein as a result of combined cross-linking.     

Rate of elapsed polymerization of hydroxyethylacrylate gel induced by gamma irradiation

The rate of elapsed polymerization of polyhydroxyethylacrylate in gelatin has been studied to investigate the effect of co-monomers consumption at a given dose.The polymer gel dosimeters consisted of 2%～4%N,N-methyelene-bis-acrylamJde cross-linker,2%-4% 2-hydroxyethylaerylate monomer and gelatin at 3% and 5%,The dosimeters were irradiated by using 60Co teletherapy Y-ray source up to 20 Gy at a constant dose rate.The relaxation rate of water proton in the dosimeters at different doses and co-monomer concentrations were measured using a nuclear magnetic resonance spectroscopy.The rate of elapsed polymerization decreases with increasing the dose and the initial concentration of co-monomers.The rate of consumption of co-monomers increases with an increase of the polymerization and the gelatin content of the polymer gel.