Thermal Stability Of Polymers Research Articles

Incorporation of Waste Orange Peels Extracts Into Pla Films

An important and hot-topic field in food packaging is the development of innovative active packaging, based on the incorporation of specific components, such as antioxidant and/or antimicrobial agents, able to modify the internal atmosphere or to be absorbed directly by the food, in order to prolong the product shelf-life. However, due to the increasing concerns of consumers about the plastics and the presence of synthetic chemical compounds in consumer goods, as well as, the importance of increasing environmental sustainability of the materials, has encouraged novel developments. This study is focused on the development of innovative, biodegradable and sustainable PLA-based active packaging solutions with the incorporation of natural antioxidant compounds recovered from agri-food wastes. An antioxidant extract was recovered through hydro-alcoholic extraction from waste orange peels, purified by resin absorption process and formulated as freeze-dried extract or spray-dried with pectin or cyclodextrins as carrier material. These three different formulations were incorporated into PLA films at different concentrations to investigate the influence of extract addition on polymer thermal stability and on colour and mechanical properties of films under accelerated light storage conditions.

Study of Surfactant–Polymer Flooding in High-Temperature and High-Salinity Carbonate Rocks

Secondary waterflood processes have low oil recovery in carbonate reservoirs as a result of their oil-wetness and heterogeneity. Surfactants in combination with polymer solutions can improve the oil recovery significantly from these reservoirs through ultralow interfacial tension (IFT), mobility control, and wettability alteration. However, application of surfactant–polymer (SP) flooding in high-salinity and high-temperature carbonate reservoirs is constrained by the thermal stability of polymers at elevated temperatures, compatibility of surfactants with a high concentration of divalent cations present in formation brines, and geochemical interactions with carbonate minerals. This research is focused on understanding surfactant and polymer interactions with formation brines containing high concentrations of divalent cations and thermal stability and transport of polymers in carbonate rocks at a high temperature (80 °C). Surfactant phase behavior experiments (with and without polymer) were performed to id...

Use of microperlite in direct polymerization of lactic acid

PLA is one of the most frequently used biodegradable polymers. In this work, PLA was synthesized by direct condensation polymerization of lactic acid in the presence of microperlite to obtain enhanced thermal stability of PLA polymer. Molecular weights of the synthesized polymers were determined by GPC. Chemical structure analyses was done by FTIR. The degree of crystallinity was evaluated by DSC and XRD. Thermal stability of polymers was investigated by DSC and TGA. It has been observed that the existence of perlite has significantly increased the crystallinity and degradation temperature, therefore, enhanced the thermal stability of the PLA.

Synthesis, characterization and properties of poly(N-allyl-tetrasubstituted imidazole)

A new poly(N-allyl-tetrasubstituted imidazole) containing furan rings and benzene ring was synthesized starting from 1-allyl-4,5-di(furan-2-yl)-2-phenyl-1H-imidazole (N-allyl-tetrasubstituted imidazole, monomer) using benzoyl peroxide as an initiator coupled with the mixture of benzene and water as solvents. The influence factors on the conversion of N-allyl-tetrasubstituted imidazole (monomer) were optimized by the orthogonal experiment. The structure and property of the obtained monomer and polymers were characterized by Fourier infrared spectroscopy, high-resolution mass spectroscopy, nuclear magnetic resonance spectroscopy, X-ray diffraction, gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis. Moreover, the luminescence property of monomer and polymers from the different polymerization conditions was investigated. The results showed that the luminescence property and thermal stability of polymer were related to molecular weight and the crystallization degree of polymer, and their thermal stability was markedly better than monomer. It suggested that poly(N-allyl-tetrasubstituted imidazole) had potential application in the fields of heat-resistant material and luminescence material.

Synthesis and characterization of fluorescent polyphenols anchored Schiff bases via oxidative polycondensation

Abstract A series of polyimines, bearing phenolic groups were successfully synthesized in aqueous alkaline solution via chemical oxidative polycondensation. Polymeric Schiff bases were synthesized by condensation of 2,4-dihydroxybenzaldehyde and 3-hydroxy-4-metoxybenzaldehyde with 2-aminophenol and 3-aminophenol. The molecular structures of the synthesized Schiff bases and their corresponding polymers were studied by FT-IR, UV-Vis, 1H-NMR and 13C-NMR spectroscopic methods. Thermal stability of the imine polymers was evidenced by their initial degradation temperatures found in the range of 170 °C to 271 °C without any sign of melting. The results of UV-Vis and cyclic voltammetry (CV) measurements were coherent with the optical Eg and the electrochemical E′g band gaps of the polyimines which were lower than those of their corresponding Schiff bases. Fluorescence spectral analysis of P4 (Schiff base polymer P4 derived from 3-aminophenol and 3-hydroxy-4-methoxybenzaldehyde) revealed a bicolor emission with blue and green light. Electrical conductivity of the synthesized imine polymers was measured by four-point probe technique. P4 showed the highest electrical conductivity as a result of iodine vapor contact time. Morphology characterization of the synthesized polyimines was carried out using a scanning electron microscope SEM at different magnifications. The study revealed that P4 is a promising candidate for both blue and green light emitters which could be used in the production of photovoltaic materials and solar cells.

Reactive modification of PVC membranes for the improved performance

Poly vinyl chloride (PVC) was chemically modified, and used for ultrafiltration to analyze the performance. Nonsolvent induced phase separation (NIPS) method was used to prepare membranes. The neat PVC membrane was casted and used as a control membrane. Modified membrane was prepared by reacting PVC with ethanolamine (EA) in the casting solution (labeled as CM-PVC). Pure water permeability (PWP) was evaluated by measuring pure water flux. Humic acid was used as model foulant solute to analyze flux and rejection ability of membranes. Flux and rejection data of neat and modified membranes were compared to prove the improvement in the filtration performance. The experimental results showed that for PVC and CM-PVC, PWP was calculated to be ~64 and ~143 L/m2.h, respectively, and the rejection of humic acid was found to be 98% and 100%, respectively. TGA was carried out to analyze the effect of chemical modification on the thermal stability of polymer. FT-IR analysis was another characterization technique used for the comparative study.

Degradation of polypropylene–poly-L-lactide blend by bacteria isolated from compost

Polypropylene (PP) degrading bacteria (P1 to P16) were isolated from compost using enrichment technique. Five isolates (P3, P6, P8, P10, and P13) were selected based on their degradation abilities. These isolates were identified as Bacillus spp. through biochemical characteristics and 16S rDNA sequence analysis. The isolates were tested for their ability to degrade blends of PP and poly-L-lactide (PLLA) (PP80 and PP80C6) in minimal media as well as in soil. In minimal media, the growth of bacteria increased with time, showing utilization of blend as carbon source. The protein content was estimated at the end of 15 days and maximum amount was secreted by isolate P8 indicating maximum potential to degrade polymers compared to other isolates. Scanning electron microscopy (SEM) results revealed the formation of biofilm on the polymer surface. Fourier-transform infrared spectroscopy (FTIR) analysis showed the formation of new bond at 2123 cm−1 and breakage of old C=O ester bond at 1757 cm−1 in case of polymer PP80C6. Thermogravimetric analysis (TGA) showed decrease in thermal stability of polymers after degradation. The carbon dioxide evolved from sample was measured and biodegradation degree was also calculated. The degree of biodegradation shown by the isolate P8 was 12% and the P6 was 10%. The results demonstrated that Bacillus species isolated from composted samples in this study provided promising evidence for the biodegradation of polypropylene and poly-L-lactide (PP-PLLA) blends in the environment.

Fabrication of Nafion/zwitterion-functionalized covalent organic framework composite membranes with improved proton conductivity

The construction of efficient proton transport channels in ion-conductive membranes is crucial to proton exchange membrane fuel cells (PEMFCs). Herein, zwitterion-functionalized covalent organic framework (Z-COF) with both ammonium groups and sulfonic acid groups was synthesized and blended with Nafion to prepare Nafion/Z-COF composite proton exchange membranes. The polymer-like feature of the Z-COF imparted favorable interactions between Z-COF and Nafion, and thus promoted the dispersion of Z-COF and the reorganization of ion clusters. The incorporation of Z-COF enhanced water retention property and the sulfonic groups on Z-COF provided additional proton-transport sites within the membranes. As a result, the low-energy-barrier paths for proton transport were created. The composite membranes with 10 wt% of Z-COF exhibited the highest proton conductivity of 0.22 S cm−1 at 80 °C and 100% RH, which was 57.1% higher than that of recast Nafion membrane. The enhanced proton conductivity also afforded the composite membrane a 45.7% increase in maximum power density of single fuel cell at 80 °C and 50% RH. The effects of Z-COF loading on membrane morphology, polymer chain mobility, thermal stability, water uptake and dimensional stability were also investigated.

Synthesis and Characterization of New Photoresponsive, Ortho and Para Oriented Azomethine Polymers

Five new azomethine polymers having aliphatic-aromatic moieties were synthesized by polycondensation reaction of dialdehydes and diamines. The dialdehyde monomers differ only in the orientation of the aromatic ring (ortho or para) and were synthesized by condensation reaction between aromatic aldehyde and 1,6-dibromohexane. The molecular mass of the monomers was recorded through E.I mass spectrum. The polymers structures were confirmed by elemental microanalysis, FT-IR, 1HNMR and UV-Vis Spectroscopy. The morphology of monomers and polymers was evaluated by scanning electron microscopy (SEM). All the polymers were soluble in DMSO (on heating) and somewhat in other solvents. Thermal stability of polymers was analyzed by thermogravimetry (TG) and differential thermal analysis (DTA), all the polymers showed good thermal stability higher than their corresponding monomers. The TG of polymers indicated maximum rate of weight loss (Tmax) within 412-708 °C. Fluorescence emission spectra of polymers were recorded and the results indicated that all the polymers were photo-responsive and indicated 1 to 4 emission bands with maximum within 349-606 nm. The limit of detection of polymers was within 0.625-1.25 ∆g/ml. The polymers were also examined for their antimicrobial activities against bacteria and fungi.

Synthesis and characterization of one, two and three-dimensional Cu(I) polymers supported by bipyridylamide ligands

Reaction of bipyridylamide ligands N-(3-pyridyl)nicotinamide (3-pna), N-(4-pyridyl)nicotinamide (4-pna) and N-(4-pyridyl)isonicotinamide (4-pina) with Cu(I) salts afforded four coordination polymers. X-ray crystallography analysis showed one-, two- and three-dimensional networks. The correlation between the pyridyl nitrogen donor disposition and dimensionality of the structures was discussed. Reflectance UV–Vis and fluorescence spectroscopic methods were used to characterize the MLCT features of these complexes. Thermal stability of the coordination polymers under nitrogen was also investigated.

Thermal stability of water-soluble polymers in solution

The thermal stability of carboxymethyl cellulose (CMC), kappa carrageenan (KC) and partially hydrolyzed polyacrylamide (HPAM) was evaluated in aqueous solution, by monitoring the viscosity of polymer solutions as a function of aging time at temperatures between 40 and 120 °C. The concept of half-life decomposition was used to determine the viscosity decay constant (τ, the time required for the specific viscosity of the solution to fall 1/e times the original viscosity) for each polymer, by applying the exponential decay viscosity model. The HPAM exhibited the greatest thermal stability, with τ values of 63.69 and 25.31 days at 80 and 100 °C, followed by CMC with τ values of 10.25 and 2.29 days at 80 and 100 °C, and KC with τ values of 3.89 and 1.26 days at 80 and 100 °C, respectively. The methodology used in this study made it possible to predict the time needed to reach certain levels of viscosity when the polymer solutions are exposed to different temperatures.

Structural characterizations, thermal behavior, and electrical measurements of the amidosulfonic acid catalyzed thermal ring‐opening polymerization of substituted cyclotriphosphazene in 1,2,4‐trichlorobenzene solution

AbstractIn this study, we aimed to design and synthesize poly[3,3,5,5‐tetrachloro‐1,1‐bis{spiro(2′,2″‐dioxy‐1′‐1″‐biphenylyl)}phosphazene] (3) in order to obtain a polymer which is resistant to moisture and hydrolysis and also contains chlorine atoms within its structure. For this reason, the polymerization experiments of polymer 3 were performed using ring‐opening polymerization (ROP) of 3,3,5,5‐tetrachloro‐1,1‐bis[spiro(2′,2″‐dioxy‐1′,1″‐biphenylyl)]cyclotriphosphazene (2) at different time and temperature. In particular, ROP of 2 was successful in 1,2,4‐trichlorobenzene solution in the presence amidosulfonic acid and promoter (CaSO4.2H2O) in sealed glass tubes under vacuum for 60, 72, and 96 hr at 220°C. The changes in molecular weight and molecular weight distribution of the polymer 3 were noted as a function of polymerization reaction time. The structure of polymer 3 was approved by gel permeation chromatography (GPC), FT‐IR, NMR spectroscopy (31P, 1H, 13C), and elemental analysis. The glass transition temperature (Tg) and thermal stability of polymer 3 were determined using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Dielectric properties of 3 were determined as a function of frequency at five different temperatures by an impedance analyzer. The activation energy of polymer 3 was calculated using Flynn–Wall–Ozawa (F–W–O) integral method.

Functional Polyethylenes with Precisely Placed Thioethers and Sulfoniums through Thiol–Ene Polymerization

The precise functionalization of polyethylenes, often accomplished through acyclic diene metathesis polymerization (ADMET), is a significant area of research that has improved polyethylene properties and performance. Here, the synthesis of precisely functionalized polyethylenes was accomplished using the thiol–ene step-growth (TES) polymerization. The simplicity and versatility of this technique allowed for the synthesis of a variety of polymers and enabled the study of carbon spacer length between and repeat unit symmetry about the resulting backbone thioether moiety. In addition, the backbone thioethers of some samples were functionalized postpolymerization with methyl triflate to produce polyethylenes containing sulfonium cations. All polymers were then characterized for their thermal stability, crystallinity, and morphology using differential scanning calorimetry (DSC) and X-ray scattering. While the carbon spacer length and repeat unit symmetry had no effect on polymer thermal stability, the incorpor...

High Performance Poly(ether-amide)s Derived from 1,1-Bis[4-(4-carboxy methylene phenoxy)-3-methyl phenyl] Cyclopentane and Aromatic Diamines

A series of new methyl substituted poly(ether-amide)s were synthesized by using direct Yamazaki’s phosphorylative polycondensation of novel diacid 1,1-bis[4-(4-carboxymethyl phenoxy)-3-methylphenyl] cyclopentane (BCMMP) with various aromatic diamines. These polymers were characterized by FTIR spectroscopy. Inherent viscosities of these polymers were in the range 0.25 to 0.42 dL/g indicating moderate molecular weight built-up. These polymers exhibited excellent solubility in various polar aprotic solvents such as NMP, DMSO, DMAc, DMF, pyridine, and were insoluble in THF, DCM and chloroform. X-Ray diffraction pattern of polymers showed that incorporation of methyl substituent on aromatic backbone and cardo cyclopentylidene moiety containing ether linkage and methylene spacer would disturb the chain regularity and packing, leading to amorphous nature. Thermal analysis by TGA showed excellent thermal stability of polymers. The glass transition temperature Tg were in the range 195–210°C. The structure-property correlation among this poly(ether-amide)s was studied, in view of these polymer’s potential applications as high performance polymers.

The relationship between structure and thermal property of two bisphenol A-derived polyphosphates

To overcome the disadvantage of liquid-phase flame retardant bisphenol A bis(diphenyl phosphate) (BDP) on processing and handling, two bisphenol A-derived solid polyphosphates, poly-phenoxyl bisphenol A phosphate (S-BDP) and poly-p-tolyl phenoxyl bisphenol A phosphate (PTPBP), were designed and synthesized from bisphenol A and dichlorophosphate by melting polymerization. PTPBP was different from S-BDP in a side-chain methyl group. The structures of polymers were characterized with FTIR, 1H-, 13C- and 31P-NMR. The molecular weight was determined by GPC. Thermal stabilities of polymers were studied by TGA. The results show that both polymers present good thermal properties. PTPBP is more stable than S-BDP at the beginning of decomposition, whereas at higher temperature the latter behaves better than the former. Furthermore, PTPBP gives more residue than S-BDP at the end of decomposition. It can, therefore, be concluded that thermal properties and char yield of compounds could be improved by increasing molecular weight and side-chain substituent. This knowledge will be helpful to design novel flame retardant. Polyphosphate flame retardant can be prepared by simple melting polymerization. A side-chain methyl group will influence molecular weight and thermal stability of polymer. The phosphates represent good thermal stability under low-heat environment and maintain their structure up to 300 °C in this study.

Application of Amino-Functionalized Nanosilica in Improving the Thermal Stability of Acrylamide-Based Polymer for Enhanced Oil Recovery

Amino-functionalized nanosilica (ANS) was prepared from nanosilica (NS) modified by 3-aminopropyltriethoxysilane. The amine groups on the ANS surface could be positively charged at acidic environment. As a result, compared to NS, ANS presented better dispersion stability and stronger interaction with functional groups on acrylamide-based polymer. Three systems, such as nanoparticle free polymer (PAS), NS/polymer (PAS-S), and ANS/polymer (PAS-AS), were prepared, and the thermal degradations of these systems in distilled water after deoxygenation were carried out at 100 and 140 °C. The variations of apparent viscosity, degree of hydrolysis, and average hydrodynamic radius in the aging process were investigated, and the results indicated that ANS could both inhibit the hydrolysis of amide groups and protect the polymer backbone to avoid the rupture of polymer molecule. As a result, PAS-AS exhibited much better thermal stability at harsh environment. The relative viscosity for PAS-AS after 12 h degradation at...

1,3,5-Triazine-based polymer: synthesis, characterization and application for immobilization of silver nanoparticles

Six s-triazine-based polymers were prepared through the nucleophilic reaction of 2,4-dichloro-6-substituted s-triazine derivatives with 1,4-diaminobutane employing conventional heating and microwave irradiation. The prepared polymers were characterized by using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). The microwave irradiation provides the target polymers in less reaction time with higher yields and purities; the results from the TGA revealed that microwave technique enhanced the thermal behavior of the prepared polymers. The effect of substituent on the thermal stability of polymers has the main factor, where incorporation of the aromatic ring on the triazine core in the prepared polymers increased their thermal stability. As a model for immobilization of silver nanoparticles (AgNPs), p-methoxy-s-triazine- 1,4-butadiamine (BDPMA) copolymer was used as an example in the presence and absence of hydrazine-hydrate. AgNPs were characterized by zeta potential, scanning electron microscope (SEM), X-ray powder diffraction analysis (XRD) and transmission electron microscope (TEM). Best results in term of particle size was obtained by using BDPMA in the absence of hydrazine hydrate, where the particle size of AgNPs was less than 20 nm as observed from TEM.

Preparation and characterization of gel polymer electrolyte based on electrospun polyhedral oligomeric silsesquioxane-poly(methyl methacrylate)8/polyvinylidene fluoride hybrid nanofiber membranes for lithium-ion batteries

As a kind of organic–inorganic hybrid materials with nanocage structure, polyhedral oligomeric silsesquioxane (POSS) has the advantages of good interaction with polymer and excellent thermal and mechanical stability. Star-shaped polyhedral POSS-poly(methyl methacrylate) (POSS-(PMMA n )8) with different molecular weights had been synthesized by sequential atom transfer radical polymerization (ATRP) with POSS-(C3H6Cl)8 as the initiator. Electrospun polyvinylidene fluoride (PVDF) composite gel polymer electrolytes (GPEs) modified by POSS-(PMMA n )8 were prepared, and their electrochemical and mechanical properties were assessed. The POSS-(PMMA n )8 particles were found to improve thermal stability and mechanical strength of the GPEs without decreasing electrochemical properties. Among all composite GPEs studied, the best comprehensive performance was obtained from PVDF-[POSS-(PMMA46)8] GPE: the porosity was 60.0%, and the tensile strength and the elongation at break were 4.94 MPa and 52.2%, respectively. Besides, the ionic conductivity was 4.85 × 10−3S cm−1 at room temperature, the electrochemical window could reach 6.0 V, and the interfacial impedance with Li electrode was 256.15 Ω. The cells with POSS-(PMMA)8-modified composite electrolytes also have good cycle performance. These results suggest that the PVDF-[POSS-(PMMA)8] composite GPEs are suitable for lithium-ion battery applications.

ROMP‐based boron nitride composites

ABSTRACTThe present work focuses on the investigation of the thermal and dielectric properties of composites obtained by surface‐modified hexagonal boron nitride (hBN) and ring‐opening metathesis polymerization (ROMP) based polymer. A new kind of high performance composites was developed based on using amino silane functionalized hBN (AS‐hBN) and bromine functional group possessing homo and copolymers synthesized via ROMP pathway. Aminosilane capped boron nitride (BN) and bromine bearing polymer backbone enhance the interaction between filler and the polymer chains. The effects of surface‐modified BN (AS‐hBN) and its content on the dielectric properties, and thermal resistance of composites, are systematically investigated and discussed. The resultant composites possess high electrical break over voltages. While all of the ROMP‐based films exhibit low ɛ′ value in a wide frequency range, in the case of the composite with 20% AS‐hBN and poly(bromooxanorbornene‐co‐cyclooctadiene) (ROMP‐BN‐6) displays very low dielectric constants in around 1.5 up to 1 MHz at 20 °C. This value is significantly lower than that of common polymer dielectrics, which is usually in the range of 3–6. Besides the lowest dielectric constant of ROMP‐BN‐6, it has also the smallest dielectric loss tangent even at high temperatures. Tan δ of ROMP‐BN‐6 is 0.003 and 0.0067 at 10 Hz–1 MHz at 20 °C, respectively. Thermal stability of polymers was also improved by introducing surface‐modified hBN. Polymers bearing 20% AS‐hBN are highly thermally stable up to ∼350 °C and gave 25% char yield at 800 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45658.

Mixed culture polyhydroxyalkanoate-rich biomass assessment and quality control using thermogravimetric measurement methods

Technology advancements for mixed culture polyhydroxyalkanoate production have been made in recent years at pilot scale, and efforts continue towards implementation of the first commercial scale production facilities. The purpose of the present work was to develop thermogravimetric analysis (TGA) methods for routine monitoring of polymer quantity and quality in PHA-rich activated sludge biomass, and for the recovered polymers. TGA quantification of the biomass PHA content correlated directly with the maximum extractable polymer (±2% gPHA/gTS). Acid pre-treatment of the biomass, prior to sample drying, significantly increased the polymer thermal stability in the biomass. This increase helps to improve the resolution of the PHA fraction of the biomass by TGA. From the TGA results, an extension to common solids analysis from Standard Methods, by including an intermediate volatile solids (IVS) assessment, was developed to quantify biomass PHA content. The IVS method entails sample volatilization and weight loss evaluation at a selected temperature between 200 and 300 °C. This intermediate temperature is in between the Standard Method sample drying (103 °C), and ashing (550 °C) oven incubations, for relative weight loss measurements that are made routinely for solids analysis. Thermogravimetric analyses were applied in isothermal polymer recovery experiments using either acetone or 2-butanol as extraction solvents. Trends in extractability as a function of extraction temperature and time correlated directly to the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) co-polymer composition in the biomass, over a 3-hydroxyvalerate in PHBV content ranging from 0 to 40 average weight percent, and a polymer weight average molecular mass between 200 and 600 kDa. Polymer type can be used to anticipate the extraction behavior, or conversely, as shown in the present work, isothermal polymer extraction trends can be used to infer the type of polymer present in the biomass.