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Studies on thermal-oxidative stability of a phosphorated antioxidant, synthesized from a natural and renewable resource cashew nut shell liquid (CNSL) was investigated, using a classical thermoanalytical method-thermogravimetric (TG/DTG) in air atmosphere. Its use as an antioxidant agent on the mineral oils NH10 and NH20 was evaluated in comparative studied with a commercial product (diphenyl phosphate – Aldrich). The addition of 1.2–2.0 wt% of phosphorated cardanol compound to the mineral oils has improved their thermal-oxidative stability on 14–18 °C, respectively. The occurrence of major thermal degradation events at higher temperatures ( T max ) on additivated oils is an excellent indication of the phosphorated cardanol compound antioxidant properties.

Pseudo-interpenetrating polymer networks (p-IPNs) of an epoxy resin and poly(methyl methacrylate) (PMMA) were synthesized simultaneously. Methyl methacrylate (MMA) was polymerized with benzoyl peroxide in the presence of an oligomeric epoxy resin, which contained stoichiometric amounts of either a tetrafunctional [i.e., ethylenediamine (EDA)] or hexafunctional [i.e., triethylenetetramine (TETA)] crosslinking agent. The resulting materials would be useful for aerospace, automotive, medical, and dental applications. The structure of the epoxy resin (i.e., tetraglycidyl 4,4′-diamine diphenyl methane) was confirmed by elemental analysis and IR and NMR spectroscopies. The thermal, mechanical, and kinetic behaviors of the polymeric networks produced from this oligomeric epoxy resin and the p-IPNs of this crosslinked epoxy with linear PMMA were compared. Time-resolved IR spectroscopy of the cyclic ether group in the epoxy at 906 cm−1 revealed kinetic information between 40 and 80°C for a complex reaction scheme. In the absence of MMA, the asymptotic final conversion of epoxide groups was achieved after (1) 60 min of chemical crosslinking at 50°C and (2) 30 min of crosslinking at 80°C with tetrafunctional EDA. In the presence of 10 wt % MMA, asymptotic final conversions of the epoxide group were achieved after (1) 150 min at 40°C, (2) 80 min at 50°C, and (3) 30 min at 80°C. In agreement with other kinetic studies based on the same epoxy resin but different crosslinking agents, these solvent-free polymerizations were diffusion-controlled during the later stages of chemical crosslinking because the apparent reaction order was very close to unity, via an unsteady state batch reactor model with lumped-parameter kinetics. The thermal expansion coefficients of the crosslinked epoxy resin increased at higher concentrations of PMMA, but hexafunctional TETA produced a higher crosslink density and reduced the thermal expansion relative to the same networks and p-IPNs prepared with tetrafunctional EDA. Elastic modulus, fracture stress, and toughness increased synergistically when the epoxy resin was crosslinked with EDA at 40°C in the presence of 10 wt % MMA. This p-IPN exhibited minimal shrinkage, on the order of 0.15%, during the actual polymerization. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1858–1868, 2003

The conductivities of blends of low-density polyethylene and poly(4-vinyl pyridine) (P4VP) were studied. The blends were synthesized by in situ sorption and thermal polymerization of 4-vinylpyridine in low-density polyethylene. They showed, after iodine doping, conductivities of 1.7 to 5.0 × 10−7 S cm−1 at 298 K, depending on the P4VP mass increment into the matrix. Their conductivities were one order of magnitude higher for measurements at 338 K. The optimum ratio of iodine to pyridine (n) which gave the highest conductivity was 0.21. The thermal stability of doped blends was acceptable for their uses as electrochemical devices. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 939–944, 2003

LDPE/P4VP films synthesized by in situ sorption and thermal polymerization of 4-vinylpyridine, (4VP), were used for conductivity investigations. The conductivities of swollen films varied from 7×10−6 to 1.21×10−3 S.cm−1 at room temperature depending on P4VP mass increase in the host matrix. For the temperature range of 303–333K the conductivity varied from 7×10−6 to 2.66×10−3 S.cm−1. A comparison between Arrhenius and VTF plots for conductivity measurements showed a best fit for temperature dependence according Arrhenius modified equation. The materials are stable for temperatures below 645 K.

Ion exchange between H + and Eu 3+ and/or Tb 3+ was studied in the material modified by in situ sorption and thermal polymerization of acrylic acid in low-density polyethylene (LDPE-PAA) and in the composite system LDPE-Fe 2 O 3 -PAA. Fluorescence spectroscopy showed evidence of Eu 3+ and/or Tb 3+ ion exchanges in these materials. The matrix LDPE-PAA after Eu(III) ion exchange presented luminescence (excitation 265 nm). This was explained by an energy-transfer process from the matrix LDPE-PAA to Eu 3+ ions. The LDPE-PAA matrix after simultaneous Eu 3+ /Tb 3+ ion exchange exhibited Eu 3+ and Tb 3+ ion luminescence (excitation 265 nm), confirming an energy-transfer process from LDPE-PAA to Eu 3+ ions in LDPE-PAA-Eu 3+ -Tb 3+ matrix. Fe 2 O 3 in LDPE-Fe 2 O 3 -PAA quenched the matrix for excitation at 265 nm and no emission at the region 400 nm was observed. The luminescence of Tb 3+ ions in the matrix LDPE-Fe 2 O 3 -PAA-Tb 3+ (excitation 265 nm) was partially quenched by Fe 2 O 3 . However, a weak emission of Eu 3+ ions was observed (excitation 265 nm) in the matrix LDPE-Fe 2 O 3 -PAA after simultaneous Eu 3+ and Tb 3+ ion exchanges, suggesting an energy transfer from Tb 3+ to Eu 3+ ions.

Pseudo interpenetrating polymer networks were prepared by a sequential method using a high molecular weight natural rubber and poly(methyl methacrylate), PMMA. The thermal properties and morphology were investigated varying the average molar mass between crosslinks ( M c ) and the composition. The extent of crosslinking of natural rubber plays a major role in the transitions domains whatever the sample composition. As the crosslink density decreases, only one T g value is observed ( M c of 500 and 1000 g/mol). Comparison between the pseudo IPNs at different M c values and compositions indicates that there are no significant differences in the thermal stabilities of the materials. Crosslinking and the component composition had a strong effect on the morphological patterns of the samples. For a higher crosslink density ( M c =142 g/mol), close and compact phase domains can be seen. The morphologies for lower crosslink densities ( M c of 500 and 1000 g/mol) showed fibrillar domains characteristic of the PMMA.

The morphology of low-density polyethylene (LDPE) modified by in situ sorption and thermal polymerization of acrylic acid (AA) in the matrix was examined. The microstructure of the LDPE/poly(acrylic acid) (PAA) materials after Eu 3+ and UO 2 2+ ion exchange was investigated. The phase behavior of these materials was analyzed using X-ray diffraction, scanning electron microscopy (SEM), and thermal measurements (DSC). The X-ray diffraction studies showed that PAA is located at amorphous region of the matrix. The LDPE/PAA surface, as investigate by SEM, was apparently homogeneous before and after Eu 3+ and UO 2 2+ ion exchange, respectively. Two T g values were found for the LDPE/PAA material before and after Eu 3+ ion exchange. Also, three and four T g values were found for LDPE/PAA after UO 2 2+ ion exchange depending on the amount of UO 2 2+ in the modified matrix. This indicates microphase domains in the LPDE/PAA-, LPDE/PAA/Eu 3+ -, and LPDE/PAA/UO 2 2+ -modified materials, although a lack of visible phase separation in the micrographs was observed.

The structures of low-density polyethylene (LDPE) modified by in situ sorption and thermal polymerization of 4-vinylpyridine (4VP) and of methyl methacrylate (MMA) were studied. The phase behavior of these materials was investigated by means of X-ray diffraction, scanning electron microscopy (SEM), and by thermal measurements (DSC). The diffraction studies indicated that the polymerization occurs at the amorphous domains of the matrix, except for the case of 4VP (168.0%), in which polymerization at the crystalline domains of LDPE matrix was also observed. These materials showed at least two T g values, indicating microphase separation. The morphology of LDPE-P4VP was different from that of LDPE-PMMA.

The effects of the temperature and fine particles of Fe2O3 upon methyl methacrylate (MMA) thermal polymerization in low density polyethylene (LDPE) matrix were investigated. The MMA mass increment in the composite matrix is a temperature dependent process. It reaches values 10 folds higher at 90°C compared to the mass increment at 60°C. The apparent polymerization rate is dependent of Fe2O3 concentration reaching a maximum at 0.17–0.26 % of Fe2O3 in the composite. The thermal process is catalysed by Fe2O3.

We investigated the effects of hydroquinone monomethyl ether concentration and film thickness upon the thermal polymerization of acrylic acid on low-density polyethylene. The thermal polymerization of acrylic acid on low-density polyethylene depended on the concentration of hydroquinone monomethyl ether inhibitor. It was a free-radical reaction with initiation on the film surface and then proceeding to the bulk matrix. The process was not controlled by monomer diffusion for the range of film thickness of 90–200 μm. It became a diffusion-controlled process at higher film thicknesses ( > 200 μm). A film layer of up to 100 μm was proposed as the limiting thickness for a diffusion-free process. © 1993 John Wiley & Sons, Inc.

The H+ UO22+ ion exchange in aqueous solution was studied in the material modified by in situ sorption and thermal polymerization of acrylic acid in low density polyethylene films. Fluorescence spectroscopy was used to observe the percentage of UO22+ exchange. The effects of temperature and film thickness in the exchange process were analyzed. The percentage of the H+ UO22+ exchange were twice as that observed for Eu3+. Simultaneous H+ Eu3+/UO22+ ion exchange in LDPE-PAA matrix was investigated and from fluorescence spectra they showed no evidence of energy transfer from UO22+ to Eu3+.

The effect of iron oxides particles mixed in natural rubber (NR) or aged natural rubber (ANR) from Manihot glaziovii were investigated. IR spectroscopy showed that α-Fe2O3 inhibits or retards the thermal degradation (200°C) of ANR, but it does not inhibit or retard the thermal degradation of NR. A retardation effect is observed using iron (III) oxide in both ANR and NR. Using both oxides, longer autoxidation induction periods of ANR and NR are observed (150°C). The periods were extended for a higher content of rubber hydroperoxide concentration. The inhibition or retardation of autoxidation using Fe3O4 in both ANR and NR is not evident. We suggest an interaction between hydroxyl groups of hydroperoxide, mainly present in aged natural rubber, and the iron oxide surface.

The nature of the species produced after sorption and thermal polymerization of acrylic acid, methyl methacrylate and 4-vinylpyridine in low density polyethylene-iron (III) oxide composite was investigated by Mossbauer and IR spectroscopies. The values of the Mossbauer parameters indicate no change in the oxidation state of iron (III) in the LDPE-Fe2O3 composite before and after sorption and thermal polymerization of the monomers. Acrylic acid interacts with iron (III) oxide particles yielding acrylates, hydroacrylates, polyacrylates and polyhydroacrylates. The iron (III) oxide particles remained unchanged after sorption and thermal polymerization of methyl methacrylate although some thermal polymerization is observed in the presence of Fe2O3-doped LDPE. Iron (III) oxide acts as catalyst for the radical polymerization of methyl methacrylate on LDPE-Fe2O3. The interaction of iron (III) oxide and 4-vinylpyridine after its sorption and thermal polymerization in LDPE-Fe2O3 is mainly by coordination bonding of the pyridine ring of the polymer to the iron of Fe2O3.

The present work shows the aspects related to the synthesis and thermogravimetric analysis of thiophosphorated and phosphorated compounds from hydrogenated cardanol. Studies on thermal-oxidative stability were investigated, using a classical thermoanalytical-thermogravimetric method (TG/DTG) in an air atmosphere. Its use as an antioxidant additive in hydrogenated naphthenic NH10, NH20 and NH140 oils was evaluated. The addition of 1.2% synthesized compounds to the oils has improved their thermal-oxidative stability by 5-15ºC. The occurrence of major thermal degradation events at higher temperatures (Tmax) in additivated oils is a good indication of the antioxidant properties of the thiophosphorated and phosphorated cardanol compounds antioxidant properties.

The Mőssbauer spectrum of Fe2O3 dispersed in PTFE is a doublet (IS=0.33 – 0.35 mm/s; QS=0.89 – 0.90 mm/s) and is unaltered by prolonged exposure to acrylic acid. Under exposure to X-rays, a new Fe (III) site is found, which differs from the preextant site in having a different microenvironment asymmetry. Acrylic acid treatment of preirradiated PTFE-iron (III) oxide composite generates an environment of a great distortion around iron nuclei as shown by the quadrupole splitting (QS=1.11 mm/s). These results show that X-rays sensitize Fe(III) towards asymmetric sites in finely dispersed iron (III) oxide particles in the amorphous region of the matrix.

Low density polyethylene can be modified by acrylic acid sorption and in situ thermal polymerization and grafting, at 60–90°C. Iron (III) oxide dispersed on low density polyethylene increases the extent of acrylic acid sorption and polymerization/grafting, both in (X-ray) preirradiated and non-preirradiated polyethylene. This effect is better observed at 60°C. The ratio between the weight gain on non irradiated and preirradiated matrix is higher at 60°C than at 90°C.

Iron oxide finely dispersed on polytetrafluoroethylene (PTFE) affects the behavior of this polymer with regard to acrylic acid and vinyl acetate sorption. Acrylic acid photopolymerization and grafting onto x-ray preirradiated PTFE are also affected. Infrared, Mossbauer, and ESR spectroscopies show that PTFE-embedded iron oxide is not transformed to iron acrylate, although it is converted to iron acetate by exposure to acetic acid. X-ray-induced polytetra-fluoroethylene free radicals are longer lived in the polymer-oxide composite than in plain polytetrafluoroethylene.