Photooxidation of vulcanized EPDM/montmorillonite nanocomposites

The photooxidation of a vulcanized ethylene-propylene-diene monomer (EPDM)/montmorillonite nanocomposite as well as EPDM/nanocomposite with stabilizers was studied under accelerated UV-light irradiation (λ ≥ 300 nm, 60 °C) for different times. The development of functional groups during oxidation was monitored by infrared spectroscopy. Photodegradation of the neat polymer and composites took place and the increases of absorbance in hydroxyl and carbonyl groups with irradiation times and also the decreases of the EPDM unsaturations were measured. The data indicated that the photooxidation products were not changed in the presence of the nanofiller. However, the presence of MMt was observed to dramatically enhance the rate of photooxidation of EPDM with a shortening of the oxidation induction time, leading to a decrease of the durability of the nanocomposites. On the other hand, it was observed that addition of stabilizers, either Tinuvin P or 2-mercaptobenzimidazole, was efficient in inhibiting the degradative effect of MMt.     

Neodymium Ziegler-Natta catalysts: Evaluation of catalyst ageing effect on 1,3-butadiene polymerization

Catalysts constituted by neodymium versatate, diisobutylaluminium hydride and t-butyl chloride were used in this work. After their synthesis, they were aged at 40 °C for 48 h. Afterwards, they were maintained at 10 °C for more 5, 15, 40, 80, 160 and 250 days and finally the aged catalysts were evaluated in butadiene polymerization. The polybutadienes were characterized by size exclusion chromatography (SEC) to determine the molecular weight characteristics and by infrared spectroscopy (FTIR) to determine the microstructure. The aim of this work is to evaluate the effect of ageing time on 1,4 polymerization of butadiene. The results showed that the stereoselectivity of the active sites was not affected by the ageing conditions. However, the catalyst activity increased for long times of ageing.     

Thermal and mechanical properties of in situ polymerized PS/EPDM blends

In situ polymerized PS/EPDM blends were prepared by dissolving poly(ethylene-co-propylene-co-2-ethylidene-5-norbornene) (EPDM) in styrene monomer, followed by bulk polymerization at 60 °C and 80 °C . EPDM has excellent resistance to such factors as weather, ozone and oxidation, attributed to its non-conjugated diene component, and it could be a good alternative for substituting polybutadiene-based rubbers in PS toughening. The in situ polymerized blends were characterized by dynamic mechanical analysis, thermogravimetric analysis, gel permeation chromatography, and tensile and Izod impact resistance tests. The PS/EPDM blends are immiscible and present two phases, a dispersed elastomeric phase (EPDM) in a rigid PS matrix whose phase behavior is strongly affected by the polymerization temperature. Mechanical properties of the blends are influenced by the increase in the average size of EPDM domains with the increase in the polymerization temperature and EPDM content. The blends polymerized at 60 °C containing 5 wt% of EPDM presents an increase in the impact resistance of 80% and containing 17 wt% of EPDM presents an increase in the strain at break of 170% in comparison with the value of PS. The blend polymerized at 80 °C containing 17 wt% of EPDM presents an increase in the strain at break of 480% and in impact resistance of 140% in comparison with the value of PS.     

Ageing and thermal degradation of plasma polymerised thin films derived from Lavandula angustifolia essential oil

The ageing and thermal degradation of polymer thin films derived from the essential oil of Lavandula angustifolia (LA) fabricated using plasma polymerisation were investigated. Spectroscopic ellipsometry and Fourier transform infrared (FTIR) spectroscopy were employed to monitor the optical parameters, thickness and chemical structure of the polyLA films fabricated at various RF powers over a period of 1400 h. The bulk of the degradation under ambient conditions was found to occur within the first 100 h after fabrication. The thermal degradation of the polyLA films was also investigated using the ellipsometry and FTIR. An increase in thermal stability was found for films fabricated at increased RF power levels. Between 200 and 300 °C, the properties indicate that a phase change occurs in the material. Samples annealed up to 405 °C demonstrated minimal residue, with retention ranging between 0.47 and 2.2%. A tuneable degradation onset temperature and minimal residue post-anneal demonstrate that the polyLA films are excellent candidates for sacrificial material in air gap fabrication.     

Thermal, ozone and gamma ageing of styrene butadiene rubber and poly(ethylene-co-vinyl acetate) blends

Ageing behaviour of SBR/EVA blends due to the effects of heat, ozone, and gamma radiation was studied with reference to blend ratio, three crosslinking systems (sulfur, peroxide and mixed) and a compatibiliser (SEBS-g-MA). It was found that an increase in the EVA content of the blends enhanced the ageing characteristics. Among the different crosslinking systems, a peroxide cured system exhibited the best retention of properties even after severe ageing. Tensile strength of peroxide cured SBR/EVA blends increased slightly after ageing for three days at 70 °C due to continued crosslinking, whereas tensile strength of all blends decreased on ageing at 100 °C. Compatibilisation with SEBS-g-MA improved the thermal, gamma and water ageing resistance of SBR/EVA blends.     

New fluorinated polymers bearing pendant phosphonic groups for fuel cell membranes: Part 1 synthesis and characterizations of the fluorinated polymeric backbone

Radical copolymerizations of chlorotrifluoroethylene (CTFE) with vinyl ethers such as 2-chloroethyl vinyl ether (CEVE) and ethyl vinyl ether (EVE) were performed at 75 °C in the presence of peroxide initiator. Three copolymers were obtained and characterized by means of both NMR and elemental analysis. Then, the chlorine atoms in the side chains were converted into iodine atoms by nucleophilic substitution, which was monitored by ¹H NMR spectroscopy. A series of five copolymers with different amounts of iodine atoms in the side chains were thus obtained. These copolymers exhibited molecular weight values of about 25,000 g mol⁻¹, and the thermal analysis of the copolymers showed a starting degradation from about 220 °C. The T_g values were in the range of 34-41 °C and showed a linear dependence versus the content of iodine atoms.     

Comparative study on the effect of partial replacement of silica or calcium carbonate by bentonite on the properties of EPDM composites

The effects of the partial replacement of silica or calcium carbonate (CaCO₃) by bentonite (Bt) on the curing behaviour, tensile and dynamic mechanical properties and morphological characteristics of ethylene propylene diene monomer (EPDM) composites were studied. EPDM/silica/Bt and EPDM/CaCO₃/Bt composites containing five different EPDM/filler/Bt loadings (i.e., 100/30/0, 100/25/5, 100/15/15, 100/5/25 and 100/0/30 parts per hundred rubber (phr)) were prepared using a laboratory scale two-roll mill. Results show that the optimum cure (t₉₀) and scorch (t_S2) time decreased, while the cure rate index (CRI) increased for both composites with increasing Bt loading. The tensile properties of EPDM/CaCO₃/Bt composites increased with the replacement of CaCO₃ by Bt from 0 to 30 phr of Bt. For EPDM/silica/Bt composites, the maximum tensile strength and E_b were obtained at a Bt loading of 15 phr, with enhanced tensile modulus on further increase of Bt loading. The dynamic mechanical studies revealed a strong rubber-filler interaction with increasing Bt loading in both composites, which is manifested by the lowering of tan δ at the glass transition temperature (Tg) for EPDM/CaCO₃/Bt composites and tan δ at 40 °C for EPDM/silica/Bt composites. Scanning electron microscopy (SEM) micrographs proved that incorporation of 15 phr Bt improves the dispersion of silica and enhances the interaction between silica and the EPDM matrix.     

Influence of polycaprolactone-triol addition on thermal stability of soy protein isolate based films

The influence of polycaprolatone-triol (PCL-T) on the thermal degradation properties of soy protein isolate (SPI)-based films was studied by thermogravimetry and infrared spectroscopy under nitrogen atmosphere. The results showed that in the absence of PCL-T the thermal degradation began between 292 °C (pure SPI films) and ca. 264 °C (SPI/SDS films with more than 20% of SDS), and these values decreased further to the range 250-255 °C for SPI/SDS/PCL-T films. At the same time, the temperature of maximum degradation rate (T_max) decreased from 331 °C (pure SPI film) to ca. 280 °C for SPI/SDS/PCL-T films with 39% PCL-T content. This behavior was also confirmed by the activation energy (E) values associated with the thermal degradation process. Apparently, the low thermal stability of PCL-T as compared to other film constituents, along with its plasticizer characteristics, is responsible for the decreased stability of SPI/SDS/PCL-T films. The FTIR spectra of gas products evolved during the thermal degradation indicated the formation of OH, CO₂, NH₃ and other saturated compounds, suggesting that the reaction mechanism involved simultaneous scission of the C(O)-O polyester bonds and C-N, C(O)-NH, C(O)-NH₂ and -NH₂ bonds of the protein.     

Long-term performance of poly(vinyl chloride) cables. Part 1: Mechanical and electrical performances

Cables insulated with plasticized poly(vinyl chloride) were aged in air at temperatures between 80 °C and 180 °C and their conditions were assessed by indenter modulus measurements, tensile testing, infrared (IR) spectroscopy and differential scanning calorimetry (DSC). Electrical testing of oven-aged cable samples was performed in order to relate the electrical functionality during a high-energy line break (HELB) to the mechanical properties and to establish a lifetime criterion. The mechanical data taken at room temperature after ageing could be superimposed with regard to ageing time and temperature. The ageing-temperature shift factor showed an Arrhenius temperature dependence. The jacketing material showed an immediate increase in stiffness (indenter modulus and Young's modulus) and a decrease in the strain at break on ageing; these changes were dominated by loss of plasticizer by migration which was confirmed by IR spectroscopy and DSC. The core insulation showed smaller changes in these mechanical parameters; the loss of plasticizer by migration was greatly retarded by the closed environment, according to data obtained by IR spectroscopy and DSC, and the changes in the mechanical parameters were due to chemical degradation (dehydrochlorination). A comparison of data obtained from this study and data from other studies indicates that extrapolation of data for the jacketing insulation can be performed according to the Arrhenius equation even down to service temperatures (20-50 °C). The low-temperature deterioration of the jacketing is, according to this scheme, dominated by loss of plasticizer by migration.     

Thermal stability of microencapsulated epoxy resins with poly(urea-formaldehyde)

A series of microcapsules filled with epoxy resins with poly(urea-formaldehyde) (PUF) shell were synthesized by in situ polymerization, and they were heat-treated for 2 h at 100 °C, 120 °C, 140 °C, 160 °C, 180 °C and 200 °C. The effects of surface morphology, wall shell thickness and diameter on the thermal stability of microcapsules were investigated. The chemical structure and surface morphology of microcapsules were investigated using Fourier-transform infrared spectroscope (FTIR) and scanning electron microscope (SEM), respectively. The thermal properties of microcapsules were investigated by thermogravimetric analysis (TGA and DTA) and by differential scanning calorimetry (DSC). The thermal damage mechanisms of microcapsules at lower temperature (<251 °C) are the diffusion of the core material out of the wall shell or the breakage of the wall shell owing to the mismatch of the thermal expansion of core and shell materials of microcapsules. The thermal damage mechanisms of microcapsules at higher temperature (>251 °C) are the decomposition of shell material and core materials. Increasing the wall shell thickness and surface compactness can enhance significantly the weight loss temperatures (T_d) of microcapsules. The microcapsules with mean wall shell thickness of 30 ± 5 μm and smoother surface exhibit higher thermal stability and can maintain quite intact up to approximately 180 °C.     

Preparation of 4(5)-vinylimidazole-co-acrylic acid copolymer and thermal performances related to applicability as PEM fuel cells

A series of acrylic acid and 4(5)-vinylimidazole copolymers for a non-hydrous proton transferring membrane used in polymer electrolyte membrane for fuel cell (PEMFC) are reported. The feed ratio of each monomer results in the variation of copolymer as evaluated by Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance spectroscopy (¹H-NMR). Differential scanning calorimeter and thermal gravimetric analyzer confirm the thermal properties of copolymer films with T_g at 105-177 °C and T_d above 230 °C. The simultaneous analysis of wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) suggests the thermal performance about the decrease in domain size as a consequence of the loss of moisture content in the membrane and the increase in domain size as a consequence of chain mobility after T_g. The proton conductivities under anhydrous condition of the copolymer membranes are in the range of 10⁻² S/cm even up to 120 °C.     

Structural and thermal characterization of sugarcane bagasse phthalates prepared with ultrasound irradiation

Chemical modification of sugarcane bagasse was achieved by esterification with phthalic anhydride in pyridine after ultrasound irradiation. The parameters including ultrasonic irradiation time 0-40 min, phthalic anhydride dosage 2.5-7.5 g, reaction time 30-150 min, and reaction temperature 80-115 °C were optimised and the extent of phthalation was measured by weight percent gain. It was found that degradation of the cell wall polymers occurred at higher temperature (>90 °C) under the experimental conditions used.FT-IR and CP/MAS ¹³C NMR spectroscopy studies also clearly produced evidence for phthalation reaction. The phthalated bagasse preparations showed decreased thermal stability after chemical modification.     

Investigation of physicochemical properties of biooils produced from yellow poplar wood (Liriodendron tulipifera) at various temperatures and residence times

Fast pyrolysis of yellow poplar wood (Liriodendron tulipifera) was performed under different temperature ranges and residence times in a fluidized bed reactor to maximize the yield of biooil. In this study, the pyrolysis temperature ranged from 400 °C to 550 °C, and the residence time of pyrolysis products was controlled between 1.2 and 7.7 s by inert nitrogen gas flow. The results revealed that the distribution of thermal degradation products (biooil, biochar, and gas) from the woody biomass was heavily influenced by pyrolysis temperature, as well as residence time. The highest yield of biooil was approximately 68.5 wt% (wet basis), with pyrolysis conditions of 500 °C and 1.9 s of residence time. Water content of the biooils produced at different temperatures was 25-30 wt%, and their higher heating values were estimated to be between 15 MJ/kg and 17 MJ/kg. Using GC/MS analysis, 30 chemical components were identified from the biooil, which were classified into 5 main groups: organic acids, aldehydes, ketones, alcohols, and phenols. In addition, biochar was produced as a co-product of fast pyrolysis of woody biomass, approximately 10 wt%, at temperatures between 450 °C and 550 °C. The physicochemical features of the biochar, including elemental analysis, higher heating values, and morphological properties by SEM, were also determined.     

Phenylethynylnaphthalic endcapped imide oligomers with reduced cure temperatures

A series of 4-(2-phenylethynyl)-1,8-naphthalic anhydride (PENA) endcapped imide oligomers with different chemical backbones and calculated number average molecular weights (Calc’d M_n) were successfully synthesized and characterized. The PENA-endcapped imide oligomers were mixtures of mono- and double-endcapped imide oligomers with polymerization degree (P_n) of 1-5 and number average molecular weights (M_n) of 2515-3851 g/mol. determined by GPC. Study on effect of chemical structures on the curing behaviors of two model compounds: PENA-m based on PENA and PEPA-m derived from 4-phenylethynylphthalic anhydride (PEPA) revealed that PENA-m showed the cure temperature of 50 °C lower than PEPA-m and the activity energy of thermal curing reaction for PENA-m was also lower than that of PEPA-m. The PENA-endcapped imide oligomers could be melt at temperatures of >250 °C with the minimum melt viscosity of 1.2-230 Pa s at 275-301 °C and the widen melt processing windows, along with 10-40 °C lower cure temperature than the PEPA-endcapped analogue.The PENA-endcapped imide oligomers could be thermally cured at 350 °C/1 h to afford the thermally cured polyimides with good combined thermal and mechanical properties including T_g of 344-397 °C (DMA), T_d of 443-513 °C, tensile strength of as high as 54.7 MPa, flexural strength of as high as 126.1 MPa and modulus of as high as 2.3 GPa, respectively.     

Study on thermal cure and heat-resistant properties of N-(3-acetylenephenyl)maleimide monomer

N-(3-acetylenephenyl)maleimide (3-APMI), was synthesized by reacting 3-aminophenylacetylene (3-APA) with maleic anhydride by the usual two-step procedure that included ring-opening addition to give maleamic acid, followed by cyclodehydration to maleimide. Structure of the monomer was confirmed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H NMR), elemental analysis (EA) and mass spectrum (MS). Thermal cure of the monomer was investigated by differential scanning calorimetry (DSC) and FTIR, then processing parameters and cure kinetics parameters were determined. The results showed that the monomer possesses excellent reactivity, whose cure peak temperature was 197.9 °C and cure reaction was almost complete after 4 h cure at 200 °C. Thermal properties of the cured monomer were determined by dynamic mechanical analysis (DMA) and the results show that glass transition temperature (represented by onset temperature of storage modulus) is high up to 460 °C. The results of thermogravimetry analysis (TGA) reveal that the cured monomer possessed excellent thermal stability, whose 10% weight loss temperature (T_10%) is 515.6 °C and char yield at 800 °C is 59.1%. All these characteristics make the 3-APMI monomer be an ideal candidate for matrix of thermo-resistant composites.     

Thermal quenching of fluorescence of freshwater, planktonic bacteria

This study aims to determine the thermal quenching properties of pure bacterial cultures as a means of aiding the development of fluorescence measurement in natural waters. The bacterium Pseudomonas aeruginosa was isolated from the urban River Tame, Birmingham, UK, and planktonic bacteria were grown in sterile, sealed glass jars, in 100 mL of sterile growth media at 37 °C for a maximum of 24 h. Samples were taken at T = 6 h and at T = 24 h, and thermal fluorescence quenching measured at 5 °C increments between 10 and 45 °C over 30 min. 3D excitation-emission matrix (EEM) plots were generated from the fluorescence analyses over time. It was found that the fluorescence of a microbial culture was significantly thermally quenched, but the results were dependent on the fluorophore type and the stage of the bacterial growth curve. Quenching was sometimes non-linear, presumably due to fluorophore production exceeding thermal quenching during the growth phase of the bacteria. Thermal quenching has the potential to allow us to confirm the importance of microbes in fluorescence signals by the non-linear response to increasing temperature, and to utilise the thermal fluorescence quenching properties of molecules to differentiate between fluorophores present during bacterial growth.     

The effects of thermal treatment on the antioxidant activity of polyaniline

The thermal stability of chemically synthesized polyaniline (PANI) was examined, including granular (G) polyaniline powders formed conventionally in an HCl medium, and nanorod (NR) samples prepared using a falling-pH synthesis. The samples were examined before and after dedoping (dd) using thermogravimetric analysis (TGA), which showed small mass losses in the 200-300 °C temperature range, and greater mass losses due to oxidative degradation at higher temperatures. Furthermore, samples were treated thermally at 100, 125, 150, 175, 200, 250 and 300 °C for 30 min in air. SEM images did not show any pronounced effect on the morphologies of the samples from thermal treatment up to 300 °C. The ratios of the intensities (Q/B) of the predominantly quinonoid (Q) and benzenoid peaks (B) from FTIR spectroscopic analysis revealed that NR-PANI and NR-PANIdd underwent cross-linking upon thermal treatment up to 175 °C and were oxidized after treatment above 175 °C. G-PANI and G-PANIdd also underwent the same chemical changes with oxidation occurring above 200 °C. The free radical scavenging capacity of the samples was evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, and was found to be independent of the spin concentrations of the samples. All samples exhibited a rapid decline in free radical scavenging capacity when exposed to temperatures above 200 °C, indicating that any polymer processing should be undertaken at temperatures less than this value to achieve high antioxidant activity.     

Thermal degradation kinetics of the biodegradable aliphatic polyester, poly(propylene succinate)

The preparation of the biodegradable aliphatic polyester poly(propylene succinate) (PPSu) using 1,3-propanediol and succinic acid is presented. Its synthesis was performed by two-stage melt polycondensation in a glass batch reactor. The polyester was characterized by gel permeation chromatography, ¹H NMR spectroscopy and differential scanning calorimetry (DSC). It has a number average molecular weight 6880 g/mol, peak temperature of melting at 44 °C for heating rate 20 °C/min and glass transition temperature at −36 °C. After melt quenching it can be made completely amorphous due to its low crystallization rate. According to thermogravimetric measurements, PPSu shows a very high thermal stability as its major decomposition rate is at 404 °C (heating rate 10 °C/min). This is very high compared with aliphatic polyesters and can be compared to the decomposition temperature of aromatic polyesters. TG and Differential TG (DTG) thermograms revealed that PPSu degradation takes place in two stages, the first being at low temperatures that corresponds to a very small mass loss of about 7%, the second at elevated temperatures being the main degradation stage. Both stages are attributed to different decomposition mechanisms as is verified from activation energy determined with isoconversional methods of Ozawa, Flyn, Wall and Friedman. The first mechanism that takes place at low temperatures is auto-catalysis with activation energy E = 157 kJ/mol while the second mechanism is a first-order reaction with E = 221 kJ/mol, as calculated by the fitting of experimental measurements.     

Sol-gel synthesis and characterization of LiNO3-Al2O3 composite solid electrolyte

Composite solid electrolytes in the system (1 − x)LiNO₃-xAl₂O₃, with x = 0.0-0.5 were synthesized by sol-gel method. The synthesis carried out at low temperature resulted in voluminous and fluffy products. The obtained materials were characterized by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy/energy dispersive X-ray, Fourier transform infrared spectroscopy and AC impedance spectroscopy. Structural analysis of the samples showed base centred cell type of point lattice of LiNO₃ for the composite samples with x = 0.1-0.2 and body centred cell for the sample with x = 0.3. A trace amount of α-LiAlO₂ crystal phase was also present in these composite samples. The thermal analysis showed that the samples were in a stable phase between 48 °C and 230-260 °C. Morphological analysis indicated the presence of amorphous phase and particles with sizes ranging from micro to nanometre scale for the composite sample with x = 0.1. The conductivities of the composites were in the order of 10⁻³ and 10⁻² S cm⁻¹ at room temperature and 150 °C, respectively.     

Microwave-treated layered double hydroxides containing Ni and Al: The effect of added Zn

Ni containing layered double hydroxides (LDHs) have been prepared by precipitation and hydrothermally treated under microwave irradiation for different periods of time. The solids have been calcined at three temperatures corresponding to stable phases formed during thermal decomposition of LDHs. The properties of the irradiated samples and of the calcined products were studied in order to ascertain whether the ageing treatment under microwave irradiation modifies not only the properties of the layered materials, but also the properties of the calcined products. A structural and textural study was carried out by PXRD, FT-IR and Vis-UV spectroscopy, thermal analyses (DTA and TG), N₂ adsorption/desorption at −196 °C and TEM microscopy; the reducibility of the nickel species was studied as well by TPR. The results show that the microwave treatment leads to better crystallized LDHs with modified thermal stability and reducibility. In addition, the degree of crystallinity of the layered precursors and their textural properties determine the properties of their thermal decomposition products.