Degradation Temperature Of Polymer Research Articles

Nano and micro co‐filled aluminum nitride/magnesium dihydrate—Silicone rubber composites for high voltage insulation

AbstractCo‐filled composites of micro magnesium dihydrate (MDH) and hydrophobically treated nano aluminum nitride (nH‐AlN) fillers in high temperature vulcanizing silicone gum are studied for thermal and dielectric characteristics for use as an insulating material in high voltage applications. The study begins with description of the compounding protocol adopted, followed by spectroscopic and optical characterization. Fourier transform infrared spectroscopy (FTIR) and energy dispersive X‐ray spectroscopy (EDX) analysis are used to verify the presence of nH‐AlN and MDH in the composites. Thermal analysis through thermogravimetric analysis revealed a stark enhancement in the onset of polymer degradation temperature, with an improvement of 208 °C achieved at 30 phr by weight loading level of MDH. Volume resistivity of 9.71 E14 Ω‐cm is obtained at 30 phr weight loading of MDH and 5 phr of nH‐AlN. AC, +DC, and −DC dielectric strength improved by 1.09, 2.06, and 1.08 times for co‐filled composites at 30 phr MDH and 5 phr nH‐AlN loading levels over unitary filled composite. Effect of dielectric polarization on dielectric constant and dissipation factor is studied at various frequencies. Limitations while conducting dry arc resistance test at standard voltage of 12.50 kV is discussed, with modification in dry arc resistance test voltage to 16.95 kV. The results are presented and discussed here.

Poly(vinylidene fluoride-co-hexafluoropropylene) based tri-composites with zeolite and ionic liquid for electromechanical actuator and lithium-ion battery applications

In order to improve the multifunctionality of polymer composites for advanced applications a novel tri-composite material is presented based on the inclusion of MFI zeolite and the ionic liquid (IL) 1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN]) in an electroactive poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer matrix. Tri-composites were produced by solvent casting with a relative overall filler content up to 40 wt.%. A compact film morphology is obtained, and the polymer degradation temperature and degree of crystallinity are independent on the filler content and type. On the other hand, the polymer crystalline phase depends on the presence of the IL but is independent of its content. Regarding the mechanical properties, it is observed that the IL has a plasticizing effect with a significant contribution to the reduction of the Young's modulus from 151 MPa for the pristine polymer to 92 MPa for the 30 wt.%/10 wt.% IL/MFI content sample. A high ionic conductivity value at room temperature of 3.9 × 10−5 S.cm−1 was obtained for the tri-composite with the highest IL content (30 wt.%/10 wt.% IL/MFI). The tri-composite system was studied as solid polymer electrolyte (SPE) for battery and bending actuator applications, demonstrating the multifunctionality of the material. The sample with the best cycling performance was observed for the highest MFI content (10 wt.%/30 wt.% IL/MFI) with a discharge capacity value of 110 mAh.g−1 and maintaining almost 80% of its initial capacity after 30 cycles at the C/10 rate. Regarding to the bending performance, the best bending actuation was detected for highest IL content (30 wt.%/10 wt.% IL/MFI), related to the ionic conductivity of the sample. Thus, it is demonstrated that the new tri-composite system, due to its tunable characteristics as a function of the relative IL and zeolite contents, is suitable for a next generation of multifunctional polymer composite materials for advanced applications.

Modeling the degradation of polyamide-12 by biocompatible fuels using artificial neural networks

In the first stage of this work, the degradation temperature of polyamide-12 was investigated using biocompatible fuels as a reference with different temperatures by thermogravimetric analysis (TGA) test. Those fuels were containing 20% and 85% ethanol as well as ethanol-free. In the second stage, the multilayer perceptron (MLP) neural network and radial basis function neural network (RBF) were designed to predict the degradation temperature of polyamide-12. Fuel temperature, ethanol percentage, and the time of placing samples in the fuel were selected as input and polymer degradation temperature was defined as network output. The results obtained from the modeling were compared with the results obtained from the test TGA. The results obtained from neural networks MLP and RBF showed slight differences with the experimental results that can be used as an efficient and low-cost tool to predict the degradation temperature of polymers.

Microwave-assisted synthesis of the lipase-catalyzed ring-opening copolymerization of ε-caprolactone and ω-pentadecanolactone: Thermal and FTIR characterization

Abstract Microwave-assisted synthesis of the lipase-catalyzed ring opening polymerization of ε-caprolactone (ε-CL) and ω-pentadecanolactone (ω-PDL) monomers was studied. A series of P(CL-co-PDL), with different molar feed ratios, including (ε-CL/ω-PDL) 100/0, 75/25, 50/50, 25/75, and 0/100, were synthesized. The resulting polyesters were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The microwave-assisted polymerization of the monomers reached high conversions (91–95%) within 60 min. FTIR spectra showed the typical absorption bands of these polyesters. A very intense band in the carbonyl region, which was shifted from 1,720 cm−1 for PCL to 1,732 cm−1 for PPDL homopolymer, as well as peaks owing to methylene groups in the 2,990–2,850 cm−1 range. DSC results revealed that all polyester samples were semi-crystalline. Interestingly, the copolymers exhibited only one melting peak (T m), and their T m values linearly increased from 57°C to 95°C as PPDL concentration was increased. Thermal stability of polyesters also depended on PDL content; an increase in PDL concentration increases polymer degradation temperature (T d).

Thermal properties of basalt/Cissus quadrangularis hybrid fiber reinforced polylactic acid biomedical composites

In this experimental study, biomedical composites of different formulations of basalt, Cissus quadrangularis fibers are melt-mixed with polylactic acid in a twin screw extruder. The standard specimens are prepared from extruded pellets using injection molding technique. Controlled crystallization temperatures are maintained throughout the compounding process to reduce degradation of the matrix and fibers. The thermal characterizations of the composites are examined by differential scanning calorimetry and thermogravimetric analysis. The thermal test results clearly indicate that the incorporation of basalt and C. quadrangularis fibers in polylactic acid results in improved thermal properties. The degree of crystallinity percentage is comparatively more for high fiber content composites. The inclusion of basalt fibers increases the polymer degradation temperature and helps to slow down the degradation of polylactic acid. Significant enhancement in the thermal stability of the biomedical composites is specimen having 12 mass percentage of basalt fiber and 0.5 mass percentages of C. quadrangularis fibers in 87.5 mass percentage of polylactic acid. A further increase in the mass percentage of C. quadrangularis affects the thermal property of the composites. The addition of Cissus is to improve estrogenic effect in implants and it is observed that the optimum mass percentage of Cissus is about 1–0.5%. The morphological structure of the composites is studied using scanning electron microscope to understand the structural interlocking characteristics of the fibers in the matrix.

The effect of incorporating ionic liquid into polyethersulfone-SAPO34 based mixed matrix membrane on CO2 gas separation performance

The present study was conducted to investigate the effect of incorporating ionic liquid into flat sheet polyethersulfone-SAPO-34 mixed matrix membrane on the performance of CO2 separation. This was achieved by blending the ionic liquid emim(Tf2N), at different concentrations, with polymer-filler solution using solvent evaporation method. All fabricated membranes were characterized by field emission scanning electron microscopy and thermo gravimetric analysis. The membranes were observed to have dense structure as indicated by FESEM and lower polymer degradation temperature from TGA. The performance of CO2/CH4 separation of the new ionic liquid incorporated membranes was compared against that of pure mixed matrix membrane at pressures ranging from 10 to 30bars. The experimental results show that the incorporation of ionic liquid into PES-SAPO-34 membrane resulted in more efficient CO2 separation. However, the permeance decreased when the pressure increased. The ideal CO2/CH4 selectivity determined from this study with the highest ionic liquid concentration is 62.6 as compared to 20.7 of pure mixed matrix membrane. This significant improvement of CO2/CH4 selectivity indicates that the ionic liquid can be used to enhance CO2 separation from CO4/CH4 mixture.

Synthesis and Thermal Behavior of Polyacrylonitrile/Vinylidene Chloride Copolymer

Polyacrylonitrile fiber encompasses a broad range of products based on acrylonitrile (AN) which is readily copolymerized with a wide range of ethylenic unsaturated monomers giving rise to polymers with different characteristics and applications. Such products can be designed for cost-effective, flame and heat resistant solutions for the textile industry, aircraft and automotive markets. In the present work acrylonitrile was copolymerized with vinylidene chloride (VDC) by conventional suspension polymerization process via redox system, with an initial content of 10%/mass of the VDC monomer. The copolymer average molecular weight was obtained by Gel Permeation Chromatography (GPC) and by intrinsic viscosity analysis. To control the polymerization process continuously, qualitative and quantitative analysis of the chloride content in the PAN AN/VDC copolymer structure was accomplished by using X-ray fluorescence and potentiometric titration techniques. A good correlation was found between these two techniques, leading to a straightforward verification of VDC in the polymer structure. The thermal behavior of PAN AN/VDC copolymer was performed by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The results showed that VDC monomers exhibited a nearly stoichiometric reaction with acrylonitrile, copolymerizing about 90% of its initial mass. VDC changed significantly the polyacrylonitrile thermal behavior, decreasing the polymer degradation temperature by about 40-50°C.

Poly(lactic acid)-Based Composites Containing Natural Fillers: Thermal, Mechanical and Barrier Properties

Natural filler/poly(lactic acid)-Based composites have been prepared by melt blending in order to investigate the resulting thermal, mechanical, and oxygen permeability properties. To this aim, several wastes or by-products (namely, cellulose fibers, wood sawdust, hazelnut shells, flax fibers, corn cob and starch) have been used, ranging from 10 to 30 wt%. The presence of these fillers is responsible of a slight reduction of the polymer degradation temperature in nitrogen as well as of a significant increase of the storage modulus as a function of the filler content. The experimental data obtained by dynamic mechanical analysis have been mathematically fitted, employing three micromechanical models (namely, Voigt, Reuss and Halpin–Tsai). Furthermore, the presence of cellulose or starch has turned out to significantly reduce the polymer oxygen permeability. Finally, in order to fully assess the feasibility of such materials, an economic analysis has been carried out and discussed.

Polystyrene composites with very high carbon nanotubes loadings by in situ grafting polymerization

Abstract

Effect of relative humidity on carvacrol release and permeation properties of chitosan based films and coatings

The influence of water vapour conditions on mass transport and barrier properties of chitosan based films and coatings were studied in relation to surface and structural properties. Water contact angles, material swelling, polymer degradation temperature, barrier properties (PO2, PCO2, WVP) and aroma diffusion coefficients were determined. The solvent nature and the presence of carvacrol influenced the surface and structural properties and then the barrier performance of activated chitosan films. Increasing RH from 0% to 100% led to a significant increase in material swelling. The plasticization effect of water was more pronounced at high humid environment, while at low RH the matrix plasticization was induced by carvacrol. The deposit of a thin chitosan layer on polyethylene decreased PO2 and PCO2 both in dry and humid conditions. The carvacrol release from the chitosan matrix was strongly influenced by RH. A temperature increase from 4 to 37°C also had an impact on carvacrol diffusivity but to a lesser extent than RH.

Polyethylene glycol/clay nanotubes composites

Nanocomposites of poly(ethylene) glycol (PEG) 20000 filled with clay nanotubes (HNTs) were prepared. The thermal properties obtained from thermogravimetry and differential scanning calorimetry were correlated to the morphology imaged by scanning electron microscopy. Low amounts of HNTs generate compact structure while large amounts of HNTs create craters and voids. The decrease of polymer degradation temperature in the presence of large amount of nanoclay (ca. 80 wt%) is a consequence of the morphology at the mesoscale range. The thermal opposite effect observed in the HNTs low regime (up to ca. 20 wt%) is due to the gas entrapment into the nanoparticles lumen. The quantitative analysis of the PEG 20000 enthalpy of melting in the presence of HNTs allowed us to characterize the polymer adsorption onto the nanoclay surface.

Recycling Ability of Biodegradable Matrices and Their Cellulose-Reinforced Composites in a Plastic Recycling Stream

The effect of multiple injection-moulding reprocessing of three biodegradable matrices on their mechanical properties, melt flow rate, molecular weight, phase transition temperatures and degradation temperature is presented. It has been found that, with successive reprocessing, tensile, flexural and impact strength decreased. Drop in mechanical properties has been assigned to degradation of the matrices, as corroborated by melt flow and molecular weight analysis. Although reprocessing did not significantly affect the glass transition, it diminished the melting point and degradation temperature of polymers. Results indicate that neat PLLA can be recycled for up to five times without suffering a drastic loss in mechanical and thermal properties. The aliphatic polyester Mater-Bi TF01U/095R can be recycled for up to 10 times, whilst starch-based Mater-Bi YI014U/C wastes should be destined to composting, since its recyclability is very poor. The effect of reprocessing on composites reinforced with chemithermomechanical pulp (CTMP) followed the tendencies observed for the neat matrices. Whilst CTMP-fibres behave mainly as filler in PLLA composites, reinforced thermoplastic starch-based composites presented enhanced mechanical properties and recyclability.

Conjugation of Soybean Oil and It’s Free-Radical Copolymerization with Acrylonitrile

The conjugated soybean oil was synthesized through the isomerization reaction of soybean oil to transformed the structure of linoleic acid into conjugated linoleic acid structure, and Rhodium complexes (RhCl(Pph3)3) was used as catalyst. The efficiency on the conjugation of catalyst RhCl (Pph3)3, tin dichloride dehydrate (SnCl2·2H2O) and triphenylphosphine (Pph3) were evaluated. The results showed when RhCl(Pph3)3, SnCl2·2H2O and Pph3 are 9.25, 9.0 and 13.1 mg in 100 g soybean oil respectively, the highest conversion of conjugation achieved 96%. The free radical copolymerization of conjugated soybean oil with acrylonitrile (AN) and dicyclopentadiene (DCP) was studied. AIBN was used as the initiator. FT-IR and 1H-NMR results indicates that the conjugated soybean oil with AN and DCP did occur free radical copolymerization with the initiator AIBN. The product is light yellow powder. The thermal properties of the soy-based copolymer were investigated by TG and DSC. The initial degradation temperature of polymers is higher then 250 °C.

Organized Formation of 2D Extended Covalent Organic Frameworks at Surfaces

The development of nanoscale masking for particle deposition is exceedingly important to push the future of nanoelectronics beyond the current limits of lithography. We present the first example of ordered hexagonal covalent nanoporous structures deposited in extended arrays of near monolayer coverage across a Ag(111) surface. The networks were formed from the deposition of the reagents from a heated molybdenum crucible between 370 and 460 K under ultrahigh vacuum (UHV) onto a cleaned Ag(111) substrate and imaged using a scanning tunneling microscope (STM). Two surface covalent organic frameworks (SCOFs) are presented; the first is formed from the deposition of 1,4-benzenediboronic acid (BDBA) and its dehydration to form the boroxine-linked SCOF-1, the second is formed from the co-deposition of BDBA and 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) to form a dioxaborole-linked SCOF-2 network. The networks were found to produce nanoporous structures of 15 A for SCOF-1 and 29 A for SCOF-2, which agreed with theoretical pore sizes determined from DFT calculations. Both SCOFs were found to have exceptional thermal stability, maintaining their structure until approximately 750 K, which was found to be the polymer degradation temperature from thermal gravimetric analysis (TGA).

Synthesis and thermo-mechanical characterization of high performance polyurethane elastomers based on heterocyclic and aromatic diamine chain extenders

Two series of 4,4′-diphenylmethane diisocyanate (MDI) and poly(ethylene glycol adipate) (PEGA)-based polyurethane and polyurethaneurea elastomers were synthesized via a one-shot polymerization method and characterized using FTIR, 1H NMR and 13C NMR. The samples in the first series are extended by aliphatic diol chain extenders while in the second series mixtures of aliphatic diols and furanic or aromatic diamine chain extenders are used. TGA experiments revealed that with furanic or aromatic diamine chain extenders the polymer degradation temperature is shifted 90 °C upwards, irrespective of the annealing time at 100 °C according to ASTM 0573-99. The values of Young's modulus and of the tensile strength are higher and the strain at break is lower for the samples in series 2 compared to those in series 1. Increasing the annealing time at 100 °C lowers Young's modulus. Dynamic mechanical thermal analyses points to a progressive microphase separation with annealing time.

Thermogravimetric Study of Polyethylene Catalytic Degradation by Zeolites

Commercial samples of high density polyethylene were decomposed over faujasites (FAU) type zeolites (Y-type) using thermal gravimetric analysis (TGA). The catalytic activity and behavior of the FAU-zeolites catalysts were determined. It was found that the degradation temperature of polymer strongly depends on the catalytic acidity of the zeolites. HY zeolite was identified as the most active catalyst due to its strong acidity. The results showed that the activation energy decrease with the amount of catalyst added.

Fluorine- and Hydroxyl-Terminated Hyperbranched Poly(phenylquinoxalines) (PPQs) from Copolymerization of Self-Polymerizable AB and AB2, BA, and BA2 Monomers

The AB and AB2 quinoxaline monomers 2-(4-hydroxyphenyl)-3-phenyl-6-fluoroquinoxaline and 3-(4-hydroxyphenyl)-2-phenyl-6-fluoroquinoxaline (HPFQ) and 2,3-bis(4-hydroxyphenyl)-6-fluoroquinoxaline (BHFQ) were copolymerized to afford different degree of linear defects in hydroxyl-terminated hyperbranched poly(phenylquinoxalines) (HT-HPPQs). The other set of BA and BA2 monomers 2-(4-fluorophenyl)-3-phenyl-6-(4-hydroxyphenoxy)quinoxaline and 2-(4-fluorophenyl)-3-phenyl-6-(4-hydroxyphenoxy)quinoxaline (FPHPQ) and 2,3-bis(4-fluorophenyl)-6-(4-hydroxyphenoxy)quinoxaline (BFHPQ) were also copolymerized to prepared fluorine-terminated hyperbranched poly(phenylquinoxalines) (FT-HPPQs). On the basis of a MALDI−TOF study of the HT-HPPQ sample (AB2 20 mol %), random copolymerization indeed occurred. In the case of HT-HPPQ, the properties of polymer such as solubility, solution viscosity, Tg, and polymer degradation temperature were greatly influenced by the number of hydroxyl group on the surface. However, the properties of FT-HPPQ were much less influenced by the number of fluorine on the surface. The copolymers of AB and AB2 were soluble in most of aprotic solvents and phenolic solvents displaying intrinsic viscosities ranged from 0.27 to 1.11 dL/g in m-cresol at 30.0 ± 0.1 °C and glass transition temperatures (Tgs) ranged from 239 to 274 °C. Copolymers of BA and BA2 were also soluble in most of aprotic solvents and phenolic solvents displaying intrinsic viscosities ranged from 1.01 to 1.15 dL/g in m-cresol at 30.0 ± 0.1 °C. HT-HPPQs and FT-HPPQs underwent 5% weight losses when subjected to thermal gravimetric analysis ranged from 511 to 568 °C and from 556 to 588 °C in nitrogen atmosphere, respectively. The enhanced thermal stabilities of FT-HPPQs could be attributed to the fluorine terminal groups on the macromolecule surfaces. The melt viscosities of the HT-HPPQ sample (AB2 20 mol %) was greater than 107 Pa·s in the lower frequency range determined as a function of frequency sweep on a RMS-800 rheometer at 320 °C. The melt viscosity linearly decreased as the frequency increased. Thus, HT-HPPQ containing a 20 mol % AB2 monomer unit displayed a lower melt viscosity compared to its linear analogue at whole frequency range. However, the relative melt viscosity decrease of hyperbranched PPQ compared to its linear analogue was less than expected due to the formation of possible inter- and intramolecular hydrogen bonding.

Epoxy-silica polymers as restoration materials. Part II

Room temperature reaction of the epoxy resin poly(bisphenolA-co-epichlorohydrin), glycidyl end-capped with the coupling agent (3-aminopropyl)triethoxysilane, in 1:2 (1), 1:1 (2) and 2:1 (3) molar ratios, leads, after curing for three months at room temperature, to glassy, transparent, crack-free solids which were investigated by SEM, TGA, DSC, NIR and Raman spectroscopy. SEM investigations show substantially a great homogeneity over the entire area with absence of cracks, veins and/or fissures and without formations of clusters and/or aggregates. The conversion of oxirane rings, as found by Raman spectroscopy, decreases by increasing the epoxy/amine ratio, with conversion percentages ranging from 95.3 to 81.3%. As a common feature, the presence in 1, 2 and 3 of Si–O–Si linkages increases the polymer degradation temperature and thermal oxidative stability relative to the parent epoxy resin by shifting the weight loss to higher temperatures. Differently from mixtures 2 and 3, which show the Tg at 90 °C, the mixture 1 does not exhibit any detectable glass transition.

Ion beam assisted unzipping of PMMA

Ion beam assisted thermal depolymerisation of poly (methyl methacrylate) (PMMA) thin films, 1 μm thick, has been studied in the temperature range RT – 400°C using a 300 keV He + beam at very low fluence (<10 12 ions cm −2). The experiments have been performed using an in situ mass spectrometer in a 10 −7 torr vacuum chamber. A relevant methyl methacrylate monomer (MMA) evolution (mass signal m/ z=100) at temperature (150°C) well below the polymer degradation temperature (360°C) has been detected during irradiation. These results have been compared with gas evolution during room temperature ion irradiation where volatile products different from monomer are known to be produced due to chain scission events. The low-temperature depolymerisation induced by ion irradiation performed on PMMA at temperature higher than T g (105°C) is promoted by the presence of beam-induced reactive species acting as initiators.

Synthesis and characterization of polyamides and polyureas with acyclic and cyclic bipyridinediyl diamino structures in the polymer backbone

AbstractA series of polyamides and polyureas containing cyclic (1b, 1c, and 1d) or acyclic (2b, 2c, and 2d) bipyridinediyl diamino units in the polymer backbone were prepared. By introducing aliphatic or aromatic comonomers, it was possible to influence the degree of rigidity of the resulting polymers. In the synthesis of the polymers 2c and 2d two new azamacrocycles 5 and 6, respectively, were also produced and they were isolated and characterized. 1H‐NMR and IR spectral data support the structure of the synthesized compounds. Thermal analysis data indicate that the polyureas posses lower PDT (polymer degradation temperature) values with respect to the corresponding polyamides.