Thermo-Oxidative Degradation of Thick-Walled Rubber Materials Studied by IR-Technique and Computed X-Ray Tomography Scanning

1990 ◽  
Vol 63 (1) ◽  
pp. 23-31 ◽  
Author(s):  
Bengt Mattson ◽  
Bengt Stenberg ◽  
Sture Persson ◽  
Erik Östman
Keyword(s):  
Oxidative Degradation ◽  
Attenuated Total Reflection ◽  
Low Permeability ◽  
Conventional System ◽  
X Ray ◽  
Oxidative Aging ◽  
Aging Properties ◽  
Thermal Stability Of ◽  
Tomography Scanning ◽  
Thermo Oxidative Degradation

Abstract Natural rubber cylinders vulcanized with two different systems, TMTD, which is an efficient vulcanizing system (EV system) and S/CBS, which is a conventional system, have been studied with respect to thermo-oxidative aging gradients, by the ATR-IR-technique (attenuated total-reflection infrared spectroscopy), computed x-ray tomography scanning and swelling. Observed aging processes are dominated by the formation of an oxidized layer whose low permeability to oxygen protects the interior of the material from oxidative aging processes as long as it is intact. The time to the formation of the oxidized layer is the major reason for the differences in the aging gradients. The oxidized layer is formed rapidly in the conventional system, whereas the formation is inhibited by dithiocarbamates in the EV system. Oxygen therefore diffuses into the EV materials, giving deeper oxidative aging than in the conventional materials at the same temperature. The conclusion drawn from the results of this study is that an earlier formation of an oxidized layer is advantageous with respect to thermo-oxidative aging of the bulk. Although it must be stated that, due to the better thermal stability of an EV system and to the poor mechanical properties of an oxidized layer, no objection is here raised to the accepted view that an EV system has superior aging properties.

THE EFFECT OF ACRYLONITRILE CONTENT ON THE THERMO-OXIDATIVE AGING OF NITRILE RUBBER

2014 ◽  
Vol 87 (1) ◽  
pp. 53-69 ◽  
Author(s):  
Richard J. Pazur ◽  
J. G. Cormier ◽  
K. Korhan-Taymaz
Keyword(s):  
Oxygen Permeability ◽  
Oxidative Degradation ◽  
Attenuated Total Reflectance ◽  
Cross Linking ◽  
Absorption Loss ◽  
Oxidative Aging ◽  
High Oxidation ◽  
Nitrile Rubbers ◽  
Rate Behavior ◽  
Thermo Oxidative Degradation

ABSTRACT The level of thermo-oxidative degradation in a series of unstabilized and unfilled nitrile rubbers (NBR) varying in acrylonitrile (ACN) content (18–43.5 wt%) was investigated on heat-aged samples (40–120 °C) by Attenuated Total Reflectance–Fourier Transform Infrared (ATR-FTIR) spectroscopy. A similar degradation profile evolution was observed regardless of ACN content with the generation of hydroxyl-, carbonyl-, and ester-based products with a concomitant loss of the 1,4-trans, 1,4-cis, and 1,2-vinyl butadienes. The magnitude of IR active group absorption loss is greatest in the lowest ACN NBR concentration and steadily lessens toward higher ACN levels (1,4-cis > 1,2-vinyl > 1,4-trans >> butadiene methylenes). The 18% ACN NBR possesses two distinct kinetically different degradation regimes (80–120 and 40–80 °C). Activation energies by carbonyl growth and 1,4-trans loss increase from 71 to 87 kJ mol−1 and from 71 to 79 kJ mol−1 respectively, for decreasing ACN (43.5–18%) content. The rate of consumption of the 1,4-trans butadiene group is mainly affected by thermo-oxidative carbonyl-based and addition-cross-linking reactions, the latter being lower in activation energy for low to mid ACN NBRs. The high oxidation rate behavior of the lowest acrylonitrile rubber is attributed to its higher oxygen permeability rates. Cross-linking due to addition-type reactions is favored for higher 1,4 unsaturation levels.

scholarly journals Electrospun Magnetic Nanocellulose–Polyethersulfone-Conjugated Aspergillus oryzae Lipase for Synthesis of Ethyl Valerate

Membranes ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 972
Author(s):  
Nurul Hidayah Hussin ◽  
Roswanira Abdul Wahab ◽  
Nursyafiqah Elias ◽  
Adikwu Gowon Jacob ◽  
Mohamad Hamdi Zainal-Abidin ◽  
...  
Keyword(s):  
Aspergillus Oryzae ◽  
Covalent Immobilization ◽  
Attenuated Total Reflection ◽  
Gravimetric Analysis ◽  
Thermal Gravimetric ◽  
Viable Option ◽  
Electrospinning Technique ◽  
X Ray ◽  
Pes Membrane ◽  
Thermal Stability Of

A novel greener MNC/PES membrane was developed through an electrospinning technique for lipase immobilization to catalyze the synthesis of ethyl valerate (EV). In this study, the covalent immobilization of Aspergillus oryzae lipase (AOL) onto an electrospun nanofibrous membrane consisting of magnetic nanocellulose (MNC) and polyethersulfone (PES) to produce EV was statistically optimized. Raman spectroscopy, Fourier-transform infrared spectroscopy: attenuated total reflection, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, thermal gravimetric analysis (TGA), and differential thermal gravimetric (DTG) of MNC/PES-AOL demonstrated that AOL was successfully immobilized onto the fibers. The Taguchi design-assisted immobilization of AOL onto MNC/PES fibers identified that 1.10 mg/mL protein loading, 4 mL reaction volume, 250 rpm stirring rate, and 50 °C were optimal to yield 72.09% of EV in 24 h. The thermal stability of MNC/PES-AOL was improved by ≈20% over the free AOL, with reusability for up to five consecutive esterification cycles while demonstrating an exceptional half-life of 120 h. Briefly, the electrospun MNC/PES fibers that immobilized AOL showed promising applicability in yielding relatively good EV levels. This study suggests that using MNC as fillers in a PES to improve AOL activity and durability for a longer catalytic process could be a viable option.

scholarly journals The influence of shaped TiO2 nanofillers on thermal properties of polyvinyl alcohol

2012 ◽  
Vol 77 (5) ◽  
pp. 699-714 ◽  
Author(s):  
Marija Radoicic ◽  
Zoran Saponjic ◽  
Milena Marinovic-Cincovic ◽  
Scott Ahrenkiel ◽  
Natasa Bibic ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Tio2 Nanoparticles ◽  
Polymer Matrix ◽  
Oxidative Degradation ◽  
Inert Atmosphere ◽  
Titania Nanotubes ◽  
Crystallinity Degree ◽  
Degradation Temperature ◽  
Thermal Stability Of ◽  
Thermo Oxidative Degradation

PVA-based nanocomposites consisting of shaped TiO2 nanocrystals (nanoparticles, nanotubes or nanorods) were synthesized by direct blending of polymer and titania nanocrystals solution or powder. In order to elucidate the influence of shape of titania nanocrystals on thermal stability of polymer matrix and particles interaction with PVA chain, structural and thermal characterizations of PVA/TiO2 nanocomposites were performed. Faceted nanoparticles increased the thermal stability of PVA matrix. Titania nanotubes and nanorods did not show any stabilizing effect on polymer matrix in argon atmosphere. The thermo-oxidative degradation temperature of PVA increased with addition of faceted TiO2 nanoparticles. The thermo-oxidative stability of the PVA matrix was affected more by the presence of titania nanotubes and nanorods in comparison with its thermal stability in inert atmosphere. The crystallinity degree (Xc=32 %) of PVA matrix slightly decreased in the presence of faceted TiO2 nanoparticles in nanocomposite sample.

scholarly journals Characteristics of Biodegradable Polylactide/Thermoplastic Starch/Nanosilica Composites: Effects of Plasticizer and Nanosilica Functionality

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Regina Jeziorska ◽  
Agnieszka Szadkowska ◽  
Ewa Spasowka ◽  
Aneta Lukomska ◽  
Michal Chmielarek
Keyword(s):  
Thermal Stability ◽  
Oxidative Degradation ◽  
Thermoplastic Starch ◽  
Silica Content ◽  
Screw Extruder ◽  
Elongation At Break ◽  
Twin Screw ◽  
Thermal Stability Of ◽  
Better Than ◽  
Thermo Oxidative Degradation

The effect of plasticizer (polydimethylsiloxanol) and neat (SiO2) or modified (having amine functional groups) silica (A-SiO2) on morphology, thermal, mechanical, and rheological properties of PLA/TPS blends compatibilized by maleated PLA (MPLA) was investigated. Toughened PLA/MPLA/TPS (60/10/30) blend containing 3 wt.% of plasticizer and various contents (1, 3, or 5 wt.%) of silica were prepared in a corotating twin-screw extruder. From SEM, it is clear that plasticized PLA/MPLA/TPS blend continuous porous structure is highly related to the silica content and its functionality. The results indicate that polydimethylsiloxanol enhances ductility and the initial thermal stability of the plasticized blend. DSC and DMTA analyses show that nucleation ability and reinforcing effect of A-SiO2on plasticized blend crystallization are much better than those of SiO2. Silica practically had no effect on the thermo-oxidative degradation. However, the composites with A-SiO2had better thermal stability than those with SiO2. Moreover, silica significantly improved the elongation at break.

scholarly journals Synthesis and photocatalytic properties of Sn–TiO2 nanomaterials

2020 ◽  
Vol 10 (01n02) ◽  
pp. 2060018
Author(s):  
E. M. Bayan ◽  
T. G. Lupeiko ◽  
L. E. Pustovaya ◽  
M. G. Volkova
Keyword(s):  
Phase Transition ◽  
Thermal Stability ◽  
Sol Gel ◽  
Rutile Phase ◽  
Photocatalytic Properties ◽  
Light Activation ◽  
X Ray ◽  
Tio2 Nanomaterials ◽  
Visible Light Activation ◽  
Thermal Stability Of

Sn-doped TiO2 nanomaterials were synthesized by sol–gel method. It was shown the phase compositions and phase transitions change with the introduction of different tin amounts (0.5–20[Formula: see text]mol.%). X-ray powder diffraction was used to study the effect of different tin amounts on the anatase–rutile phase transition. It was found that the introduction of ions increases the thermal stability of anatase modifications. The material’s photocatalytic activity was studied in reaction with a model pollutant (methylene blue) photodegradation under UV and visible light activation. The best photocatalytic properties were shown for material, which contains 5[Formula: see text]mol.% of Sn.

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