Thermal Degradation Behavior Of Poly Research Articles

Thermal Degradation Studies of Poly(2-ethyl hexyl acrylate) in the Presence of Nematic Liquid Crystals.

The thermal degradation behavior of Poly(2-ethyl hexyl hcrylate) (Poly(2-EHA)), blended with a commercially available nematic liquid crystal (LC) mixture, was investigated by thermal gravimetric analysis (TGA). Different heating rates, ranging from 5 to 200 °C/min, were applied under an inert atmosphere. Based on the TGA results, activation energies (Eα) at different conversion rates (α) were determined using three integral isoconversion methods: Flynn-Wall-Ozawa (FWO), Tang, and Kissinger-Akahira-Sunose (KAS). It can be noticed that the global evolution of these activation energies was the same for the three models. The coefficient of determination R2 presented values generally higher than 0.97. Using these models, the Eα value for the LC remains constant at 64 kJ/mol for all conversions rates. For the polymer Poly(2-EHA), applying the Tang and FWO models, the activation energy presents a variation ranging from 80 kJ/mol, for conversion α = 0.1, to 170 kJ/mol, for α = 0.9. For the third model (KAS), this energy varies between 80 and 220 kJ/mol in the same range of α.

Thermal degradation kinetics of Opuntia Ficus Indica flour and talc-filled poly (lactic acid) hybrid biocomposites by TGA analysis

This paper reports the effect of lignocellulosic flour and talc powder on the thermal degradation behavior of poly (lactic acid) (PLA) by thermogravimetric analysis (TGA). Lignocellulosic flour was obtained by grinding Opuntia Ficus Indica cladodes. PLA/talc/ Opuntia Ficus Indica flour (OFI-F) biocomposites were prepared by melt processing and characterized using Wide-angle X-ray scattering (WAXS) and Scanning Electron Microscope (SEM). The thermal degradation of neat PLA and its biocomposites can be identified quantitatively by solid-state kinetics models. Thermal degradation results on biocomposites compared to neat PLA show that talc particles at 10 wt % into the PLA matrix have a minor impact on the thermal stability of biocomposites. Loading OFI-F and Talc/OFI-F mixture into the PLA matrix results in a decrease in the maximum degradation temperature, which means that the biocomposites have lower thermal stability. The activation energies (Ea) calculated by the Flynn Wall Ozawa (FWO) and Kissinger Akahira Sunose (KAS) model-free approaches and by model-fitting (Kissinger method and Coats-Redfern method) are in good agreement with one another. In addition, in this work, the degradation mechanism of biocomposites is proposed using Coats-Redfern and Criado methods.

Thermal degradation behavior of poly[(R)-3-hydroxybutyrate-co-4-hydroxybutyrate

The thermal degradation behavior of poly[(R)-3-hydroxybutyrate-co-16 mol%-4-hydroxybutyrate] (P(3HB-co-16 mol%-4HB)) was investigated based on spectroscopic analysis of its pyrolyzates and two kinetic modeling approaches. Pyrolyzate analysis revealed that trans-crotonic acid, cis-crotonic acid, γ-butyrolactone, and their oligomers (dimers and trimers) were produced following thermal degradation of P(3HB-co-16 mol%-4HB). The kinetic analyses confirmed that the thermal degradation behavior of this copolymer changed depending on the time and/or temperature parameters. Specifically, this degradation process proceeded in at least two steps, (i) initial random degradation and (ii) subsequent 0th-order weight loss, which indicated unzipping degradation of the 3HB units. Based on 13C NMR and two-dimensional NMR methods, it was determined that the unzipping degradation of 3HB units starting from the chain end may stop or volatilize an oligomer when the reaction reaches a 4HB unit randomly present in the copolymer.

Potentiometric studies on the influence of poly(N-vinylpyrrolidone) on the thermal degradation behavior of poly(vinyl chloride) blends

Abstract The thermal degradation behavior of poly(vinyl chloride) (PVC) and poly(N-vinylpyrrolidone) (PVP) blends was investigated using potentiometric measurements of the released HCl gas during the degradation process, estimating the degree of discoloration of the degraded samples and measuring the thermal stability (Ts) values. The influence of the PVP percentage in the blend and, moreover, of the addition of commercial dibasic lead carbonate stabilizer to the blend was studied with regard to thermal stability. It turned out that the dehydrochlorination rate of the blend was promoted by increasing the PVP concentration in the blend.

Experimental and theoretical investigations of thermal degradation behaviors of poly(aryl ether sulfone)s

ABSTRACTDensity functional theory (DFT) calculation and pyrolysis gas chromatography mass spectrometry (PyGC/MS) analysis were combined to investigate the thermal degradation behavior of polysulfone, poly(ether sulfone) and poly(phenylene sulfone). A series of pyrolysis temperatures from 500°C to 700°C with the interval of 50°C were chosen for their PyGC/MS analyses, and the obtained results indicate that phenol as a pyrolysis product is preferentially generated over SO2 during their pyrolysis. In DFT calculations, their bond dissociation energies and first-stage fragmentation products diradicals at various temperatures were calculated by the M05-2x method, and their preferentially produced pyrolysates estimated from the obtained results are in accordance with the experimental findings.

Effect of ZnO on the Thermal Degradation Behavior of Poly(Methyl Methacrylate) Nanocomposites.

The influence of ZnO nanoparticles on the thermal degradation behavior of poly(methyl methacrylate) (PMMA) was tested using thermoanalytical techniques. The studied materials were investigated using TG, DTA, EGA, XRD, SEM and TEM. The ZnO nanoparticles were synthesized via precipitation by adding LiOH into Zn2+ water/ethylene glycol solutions. The ZnO-PMMA nanocomposites were prepared by adding the appropriate amount of ZnO into MMA and subsequent MMA radical polymerization. According to the experimental results and model-free isoconversional activation energy calculations, the addition of ZnO into PMMA played a double role. The ZnO concentrations up to 0.15% stabilized the composite by shifting the degradation interval toward higher temperatures and increasing the apparent activation energy relative to pure PMMA. At higher concentrations, the catalytic effect of ZnO started to prevail and was reflected in the lower temperature intervals of intense PMMA degradation and lower apparent activation energy. The addition of ZnO generally did not change the nature of the PMMA decomposition process.

Synthesis, thermal degradation and dielectric properties of poly[2-hydroxy,3-(1-naphthyloxy)propyl methacrylate

2-Hydroxy-3-(1-naphthyloxy)propyl methacrylate (NOPMA) monomer was synthesized from reaction of 2-[(2-naphthyloxy)methyl]oxirane with methacrylic acid in the presence of pyridine. The polymerization of NOPMA was carried out by free radical polymerization method in the presence of AIBN at 60 °C. The structure of monomer and polymer was characterized by 1H-NMR, 13C-NMR and FT-IR spectroscopy techniques. The glass transition temperature and average-molecular weights of poly(NOPMA) were measured using differential scanning calorimetry and gel permeation chromatography, respectively. The thermal degradation behavior of poly(NOPMA) has been investigated by FT-IR studies of the partially degraded polymer and thermogravimetry. The cold ring fractions (CRFs) were collected at two different temperatures, initially fraction-1 (CRF1) is from room temperature to 320 °C, and the other fraction-2 (CRF2) is from 320 to 500 °C. The volatile products of the degradation were trapped at −195 °C (in liquid nitrogen). All the fractions were characterized by FT-IR, 1H and 13C-NMR spectroscopic techniques, and the cold ring fractions (CRFs) were also characterized by GC–MS. For the degradation of polymer, the major compound between products of CRFs is α-naphthol. The GC–MS, FT-IR and NMR data showed that depolymerization corresponding to monomer was not prominent below 320 °C in the thermal degradation of poly(NOPMA). The mode of thermal degradation containing formation of the major products was identified. The dielectric permittivity (ε′), the loss factor (ε″) and conductivity (σac) were measured using a dielectric analyzer in the frequency range of 50 Hz to 20 kHz.

Chitosan from Muga silkworms (Antheraea assamensis) and its influence on thermal degradation behavior of poly(lactic acid) based biocomposite films

ABSTRACTThe research work is focused on extraction of chitin from Muga silkworms (MS) and its conversion into chitosan by chemical treatment process. The extracted amount of chitin and chitosan from MS were obtained ∼8 wt % and ∼7 wt %, respectively. Potentiometric titrations, conductometric titrations, elemental analysis, 1H‐NMR and FTIR analyses were employed to calculate the degree of deacetylation of chitosan (extracted at 80 ºC after 10 h) and found as 77% ± 2, 81% ± 1.8, 82% ± 2.4, 97.77% ± 0.3, and 82% ± 1.8, respectively. The deacetylation process of chitin showed pseudo‐first order reaction kinetics and activation energy was estimated as ∼15.5 kJ/mole. The extracted chitosan (at 80 ºC after 10 h) showed higher crystallinity and improved thermal stability with respect to chitosan extracted from other marine sources. Subsequently, poly(lactic acid) (PLA) and extracted chitosan dispersed biocomposite films were prepared by solution casting method. Significant dispersion of chitosan (extracted at 80 ºC after 10 h) micro‐particles were observed in biocomposite films using FESEM analysis. Due to chitosan interaction with PLA, significant reduction in thermal degradation and activation energy was observed during nonisothermal degradation scan of such films using Flynn‐Wall‐Ozawa and Kissinger‐Akahira‐Sunose models. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43710.

Effects of Molecular Weight on Thermal Degradation of Poly(α-methyl styrene) in Nitrogen

The effects of molecular weight on the thermal degradation behavior of poly(α-methyl styrene) (PAMS) was investigated by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) and thermogravimetric analysis (TGA). The Py-GC/MS analysis results showed that the degradation of PAMS with different molecular weights in nitrogen produced only the monomer, alpha-methylstyrene. The TGA results showed a pronounced reduction in the decomposition temperature with increasing molecular weight. The degradation kinetic parameters, calculated by the Kissinger and the Coats–Redfern methods, further revealed that the activation energy and the pre-exponential factor decreased with increasing molecular weight. Most importantly, the degradation order of the PAMS in nitrogen remained around 1, independent of the molecular weight, suggesting the maintenance of the depolymerization mechanism. All the above results provided an insight into the effects of molecular weight on the thermal degradation behavior of PAMS.

Thermal degradation of poly(lactide-co-propylene carbonate) measured by TG/FTIR and Py-GC/MS

Thermal degradation behaviors of poly(lactide-co-propylene carbonate)s (PLAPCs) with different PC contents were studied at various pyrolysis temperatures by the combination of thermo gravimetric analysis/Fourier transform infrared spectrometry (TG/FTIR) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) techniques. The activation energies of thermal degradation are calculated by Kissinger method. The experimental results indicate that increasing PC content in PLAPC chain lead to a decrease of maximum decomposition temperature. The activation energy of degradation increases with increasing PC content. The dominant degradation pathway is a backbiting ester interchange reaction involving OH chain ends of PLAPCs, resulting in the formation of cyclic oligomers. In addition, at a relative higher pyrolysis temperature, besides the major products propylene carbonate and lactide, small amounts of propenoic acid and acetaldehyde were also detected, showing a main intramolecular trans-esterification accompanied with chain scission decomposition mechanism.

Effect of modified silica on the crystallization and degradation of poly(3-hydroxybutyrate)

The crystallization and thermal degradation behaviors of poly(3-hydroxybutyrate) (PHB) filled with surface-modified silicas were analyzed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and dynamic thermogravimetric analysis (TG). The results of FTIR and TG confirmed that the substantial amounts of methyl methacrylate (MMA) and amidoamine (AMDA) were successfully grafted onto the hydrophilic silica surfaces. From DSC and TG analyses, it was indicated that the crystallization rate, crystallinity, melting temperature (Tm), content of the high Tm crystals, and thermal stability of PHB were affected by the type and amount of the silicas used and changed with the grafted chemicals. The hydrophobic silica has a better effect on enhancing crystallization rate and thermal stability of PHB than the hydrophilic silica due to the better compatibility with PHB. However, the MMA and AMDA grafted onto the hydrophilic silica surfaces effectively improved the crystallization and degradation effects of the hydrophilic silica. The addition of two parts AMDA-modified silica in a hundred parts PHB has the best improvement in terms of of the crystallization, melting characteristics, and thermal stability of PHB.

Thermal degradation mechanism of poly(hexamethylene carbonate)

Thermal degradation behaviors of poly(hexamethylene carbonate) (PHC) were investigated by means of thermogravimetric analysis (TGA), proton nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC) and pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS). Six types of PHC samples with different end groups and molecular weights were synthesized to systematically investigate the thermal degradation mechanism. Thermal degradation behaviors of the PHC samples were examined under both isothermal and non-isothermal conditions. The PHC samples showed distinct thermal degradation behaviors from other aliphatic polycarbonates (poly(propylene carbonate), poly(trimethylene carbonate) and poly(butylene carbonate)). The results indicated that the chain-end structure makes a slight effect on the thermal stability of PHC regardless of the molecular weight. During the non-isothermal degradation of PHC, four main reactions were illustrated: unzipping, intramolecular transesterification, β-H transfer and decarboxylation reactions. Intramolecular transesterification reaction dominantly occurs below 300 °C accompanying with unzipping reaction which can only be induced by hydroxyl end group, and releasing cyclic hexamethylene carbonate monomer and dimer. Above 300 °C, the four degradation reactions take place simultaneously.

Furan-based polyesters from renewable resources: Crystallization and thermal degradation behavior of poly(hexamethylene 2,5-furan-dicarboxylate)

In the present study poly(hexamethylene 2,5-furan dicarboxylate) (PHF), a polyester prepared from monomers derived from renewable resources, was synthesized by applying the melt polycondensation method. The polymer exhibited a melting temperature of about 145°C while the glass transition temperature was 7°C. After isothermal crystallization, PHF showed multiple melting behavior which was attributed to partial melting–recrystallization and final melting. The equilibrium melting temperature of the polymer was found to be 157°C, while the heat of fusion of the purely crystalline material was found to be 34kJ/mol (143J/g). A crystallization regime I to regime II transition was observed at 134°C as a breakpoint in the Lauritzen–Hoffman plot. The KgI and KgII values were calculated 0.9×105 and 1.76×105 respectively. Polarized optical microscopy was also employed for the study of the isothermal crystallization of PHF. PHF can be regarded thermally stable since its decomposition starts above 350°C. Thermal degradation kinetics were investigated by means of thermogravimetric analysis.

Thermal degradation kinetics of sucrose palmitate reinforced poly(lactic acid) biocomposites

The current work is focused on investigating the influence of novel bio-filler, “sucrose palmitate (SP)” on the thermal degradation behavior of poly(lactic acid) (PLA) biocomposites in order to render its suitability for food packaging application. Thermal degradation behavior of the PLA biocomposites was investigated by thermo-gravimetric analysis (TGA) using dynamic heating regime. The differential TG analysis revealed that there is no change in the Tmax value (357°C) for PLA and its composites up to 5wt% of bio-filler loading. This reveals that the sucrose palmitate acts as a protective barrier by decelerating the thermal degradation rate of PLA. In the case of 10wt% of the filler incorporated in the PLA matrix, Tmax rapidly shifted to lower temperature (324°C). This downturn in Tmax at higher loading of the filler is due to the increase in acidic sites and enhancement in the rate of degradation is observed. Differential scanning calorimetry (DSC) analysis revealed unimodal melting peak indicating the α-crystalline form of PLA. Based on the thermal degradation profile of sucrose palmitate, possible mechanism for degradation of PLA composites is proposed. The activation energies (Ea) of thermal degradation of PLA and PLA composites were evaluated by Flynn–Wall–Ozawa and Kissinger methods.

Thermal degradation of two different polymers bearing amide pendant groups prepared by ATRP method

Piperidinocarbonylmethyl methacrylate (PyCMMA) and 1-(piperidinocarbonyl) ethylmethacrylate (PyCEMA) monomers were synthesized. Polymerizations of PyCMMA and PyCEMA were carried out by atom transfer radical polymerization. The structure of monomers and polymers was characterized by 1H-NMR, 13C-NMR, and FT-IR spectroscopies. Characterization of poly(PyCMMA) and poly(PyCEMA) were carried out using differential scanning calorimetry and gel permeation chromatography. The experimental results showed that the reaction exhibited characteristics of controlled polymerization. The thermal degradation behaviors of poly(PyCEMA) and poly(PyCMMA) were studied using thermogravimetry and a single line vacuum system consisting of a degradation tube with a condenser for product collection. The poly(PyCEMA) and poly(PyCMMA) were heated from ambient temperature to 325 and 500 °C, respectively. The products of degradation were collected as a cold ring fraction (CRF). The CRFs of degradation were investigated by means of IR, 1HNMR, and GC-MS. For the degradation of both polymers, the major products of CRFs are piperidinocarbonyl methanol and 1,2-dipiperidino,1-oxo ethane. The GC-MS, IR, and NMR data showed that depolymerization below 325 °C to the corresponding monomer was not prominantin the thermal degradation of poly(PyCMMA). The mode of thermal degradation including formation of the major products was identified.

Enhancement of thermal stability and degradation kinetics study of poly(vinyl alcohol)/zinc oxide nanoparticles composite

The thermal degradation behaviors of poly(vinyl alcohol) (PVA) and PVA/zinc oxide (ZnO) composite are investigated using differential thermal analysis (DTA). The degradation activation energy ( Ed), frequency factor ( ko) and Avrami exponent ( n) as thermal kinetic parameters are calculated from the DTA results. The calculated values of Ed are 80.94 and 148.58 kJ mol−1 for PVA and PVA/ZnO composite, respectively, indicating the enhancement of the PVA thermal stability as ZnO nanoparticles are filled in PVA matrix. The n values are evaluated from the shape analyses of degradation peaks. From estimated n values, the degradation mechanisms are determined for both the complexes under investigation.

Effect of bioactive glass particles on the thermal degradation behaviour of medical polyesters

The thermal degradation behaviour of poly(ε-caprolactone) (PCL), poly(l-lactide) (PLLA) and poly(lactide/ε-caprolactone) (PLCL) and of composites of these polymers filled with bioglass particles was investigated by means of thermogravimetric analysis (TGA). According to the activation energies calculated by the Friedman approach, PCL showed the highest resistance to thermal degradation. Addition of bioglass induced a reaction between the ester groups of the polyesters and the SiO− groups present in the surface of bioglass particles which caused a 1.3–1.9 fold decrease in activation energies of the composites with respect to their unfilled polymer counterparts. This reaction was proven by the increase in the absorbance of the carboxylate peak in the infrared spectra of the composite films maintained at 210 °C and confirmed the random chain scission of the polymer chains. This fact caused a significant decrease in the featured thermal transitions of the polymers as determined by the differential scanning calorimetry (DSC) measurements.

Thermal degradation of poly(isobornyl acrylate) and its copolymer with poly(methyl methacrylate) via pyrolysis mass spectrometry

In this work, the thermal degradation characteristics of poly(isobornyl acrylate) (PIBA), and its copolymer with PMMA, P(MMA-co-IBA) were investigated via direct pyrolysis mass spectrometry. Thermal degradation behavior of poly(isobornyl methacrylate) (PIBMA) was also studied for a better understanding of thermal degradation mechanism of PIBA. For both PIBA and PIBMA, γ-H transfer from the isobornyl ring to the carbonyl group was predominantly effective in thermal degradation. As a consequence of evolution of isoborylene, poly(acrylic acid) was produced. Trans-esterification reactions due to intermolecular interactions lead to evolution of H2O. Upon loses of CO2 and CO crosslinked units with higher thermal stabilities were generated. In case of P(MMA-co-IBA), intermolecular interactions between PIBA and PMMA chains were detected. Based on evolution of methanol, a trans-esterification reaction between the MMA and acrylic acid units generated by loss of isobornylene from PIBA chains was proposed.

Fabrication and thermal degradation behavior of poly(vinyl chloride) particle coated with polythiophene and polyaniline

Nanocomposites of polythiophene and polyaniline with poly(vinyl chloride) (PTh/PVC and PAn/PVC) were prepared successfully in aqueous media in the presence of different surfactants such as hydroxypropyl cellulose (HPC) and Poly(vinyl alcohol) (PVA). PVC particles were coated with PAn and PTh by using chemical oxidative polymerization method. These core–shell nanocomposites were characterized such as morphology, chemical structure and thermal stability by using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) respectively. FTIR spectrum analysis confirmed that the nanocomposite was formed in present of surfactant. TGA curves revealed that presence of surfactant can drastically increase the thermal stability of PAn/PVC and PTh/PVC nanocomposites.

Thermal degradation behaviour of poly(vinyl chloride) in the presence of poly( N′-acryloyl benzhydrazide)

The thermal degradation behaviour of poly(vinyl chloride), PVC, in the presence of poly( N′-acryloyl benzhydrazide), PABH, has been studied using continuous potentiometric determination of the evolved hydrogen chloride gas from the degradation and by measuring the extent of discoloration of the degraded samples. Blending this polymeric additive with dibasic lead carbonate, DBLC, reference stabilizer in different ratios had synergistic effects on both the thermal stability and the extent of discoloration of PVC.