TGA In Nitrogen Research Articles

Tuning the thermal properties of poly(ethylene)‐like poly(esters) by copolymerization of ε‐caprolactone with macrolactones, in the presence of a pyridylamidozinc(II) complex

ABSTRACTLinear aliphatic poly(ester)s, as thermoplastic materials, are more and more envisaged as the potential “green” alternative to traditional plastics. Aliphatic polyesters having long methylene chain behave as “polyethylene‐like” materials and can be prepared by ring‐opening polymerization (ROP) of macrolactones. A pyridylamidozinc(II) complex was used for the ROP of ε‐caprolactone (CL) and of two large ring size lactones, the ω‐6‐hexadecenlactone (6HDL) and the ω‐pentadecalactone (PDL). High turnover frequencies were observed for the CL polymerization, while for the macrolactones, an entropy‐driven behavior was recognized. Random copolymerizations of the PDL with 6HDL and of the macrolactones with CL were successfully achieved, and the copolymer microstructure was ascertained by NMR and MALDI analyses. The copolymer melting temperatures, measured by DSC, and the thermal degradation behavior, studied by TGA in nitrogen and air atmosphere, were dependent on the copolymer's composition. © 2020 Wiley Periodicals, Inc. J. Polym. Sci.2020,58, 528–539

Simplified structure of the condensed phase of fire retarded PA6 nanocomposites in TGA as related flammability

This paper concerns with the analysis of the nature of the mass residue of PA6 and its nanocomposites in nitrogen. To assess the structure of the condensed phase during pyrolysis, this study presents thermal (by TGA in nitrogen) and condensed phase analysis of the residue (by FTIR-ATR) of PA6 nanocomposites consisting of phosphorous based flame retardants (FR) and/or nanoparticles (based on modified Montmorillonite clay). The thermal analysis reveals that the nanoparticles do not change the pyrolysis kinetics of PA6 whereas the FR does. The FR and NC used in the polymer nanocomposites (PNC) are capable of changing the structure of the char compared with pure PA6, where the char structure consists of polycyclic aromatic hydrocarbons (PAH) whereas the PA6 does not leave any considerable amount of mass residue. This residue analysis for decomposition samples in TGA in Nitrogen of the PA6/FR/NC composites complements previously published work for gas phase analysis ( FTIR-gas) as well as cone calorimeter characterization for their flammability. The overall aim, addressed here also, is to find out to what extent microscale measurements (e.g. TGA/FTIR/DSC/ATR) can be used a priori to delineate the flammability of polymer fire retarded composites. It is shown that FTIR-gas and FTIR (ATR) residue can be used to determine the fire retardant action (solid and/or gaseous) only qualitatively.

Synthesis and properties of new polyamide/multiwalled carbon nanotube nanocomposites containing a pyridine group

AbstractThe effects of multiwalled carbon nanotubes (MWCNTs) on the thermal properties and flame retardancy of a new polyamide (PA) derived from glutaric acid and aromatic diamine were investigated in this work. The synthesized PA containing pyridine and trialkylamine groups was characterized by 1H NMR and SEC. The PA unit structure was geometrically optimized at the B3LYP/6‐311++G(d, p) level of theory. PA showed a glass transition temperature of 151 ºC. PA nanocomposites containing two different amounts of MWCNTs were prepared via the solution intercalation technique with the solvent N,N‐dimethylacetamide. Transmission electron microscopy showed that MWCNTs were exfoliated in the polymer matrix, resulting in well‐dispersed morphologies at 3 wt% MWCNT content. The redox behaviors of PA and the nanocomposites were examined using cyclic voltammetry (CV). PA showed a reversible oxidation process in the CV scan. Thermal and flammability properties of the nanocomposites were studied by TGA in nitrogen and air, DSC and with a microscale combustion calorimeter. The TGA results showed that the addition of MWCNTs resulted in a substantial increase in the thermal stability and char yields of the nanocomposites compared with neat PA. The heat release rate and total heat release were significantly reduced in the presence of MWCNTs. © 2013 Society of Chemical Industry

Preparation, characterization and thermal degradation study of poly(amide imide)s based on tri-component mixture of PMDA/BTDA, diamines and acid chloride

A series of poly(amide imide)s (PAIs) having alternate (amide–amide) and (imide–imide) units (polymers 1–14 and 22–35), and random distribution of amide-imide linkages (polymers 15–21 and 36–42) were prepared by low temperature solution polymerization of benzene-1,2,4,5-tetracarboxylic dianhydride (PMDA)/benzophenone-3,3′,4,4′-tetracarboxylic dianhydride (BTDA), diamines (cyclic and aromatic) and acid chloride in dimethylforamide. All the polymers were readily soluble in polar aprotic solvents with inherent viscosities in the range of 0.134–0.878. The process of cycloimidization of poly(amide amic acid)s (PAAs) to PAIs was investigated by TGA and FT-IR techniques at four different temperatures i.e., 175, 200, 225, and 260 °C. The rate of cycloimidization was calculated by taking into account the theoretical weight loss (WT), obtained from [n × Mw (H2O)/Mw (RU)] W, where Mw (H2O) molecular weight of water, W weight of PAA taken for TGA, Mw (RU) the molecular weight of repeat unit of PAA, n number of water molecules eliminated per repeat unit of PAA upon cycloimidization. For a particular diamine, the extent of percentage cycloimidization at the end of the isothermal heating was higher for PAAs containing trimellitic anhydride chloride (TMAc) unit, irrespective of the nature of the dianhydride and diamine. Thermal and thermooxidative degradation of PAIs was investigated by TGA in nitrogen and oxygen atmosphere. The initial decomposition temperatures (IDT) of polymers are above 260 °C, and vary widely (from 260 to 501 °C) depending upon the structure of the polymer backbone. PAIs containing TMAc exhibited higher thermal stability as compared to those polymers having diacid chloride units, in both N2/O2 atmospheres.

Linear and branched alkyl substituted octakis(dimethylsiloxy)octasilsesquioxanes: WAXS and thermal properties

A series of octakis(dimethylsiloxy)octasilsesquioxanes bearing linear and branched alkyl substituents has been prepared in high yield by Pt-catalyzed hydrosilylation of alkenes with octakis(hydrodimethylsiloxy)octasilsesquioxane, chain length varying between C3 and C8 for the straight-chain derivatives and between C5 and C7 for the branched-chain derivatives. On the basis of a WAXS study, we showed that the linear derivatives are amorphous and that the interdigitation of alkyl chains between neighboring POSS molecules increases as the alkyl chain length increases from propyl to octyl. The thermal behavior of these compounds was studied by DSC, polarized optical microscopy and TGA in nitrogen and air atmosphere. The derivatives with shorter n-alkyl chains from C3 to C6 crystallize below 0 °C whereas the derivatives with longer n-alkyl chains (C7 and C8) can be regarded as amorphous glasses with a T g around –100 °C. The morphology and thermal properties change considerably with branching of the alkyl chain. Melting points above ambient temperature were found for the iso-hexyl and iso-heptyl POSS derivatives whereas the iso-pentyl POSS derivative is liquid at 25 °C. From the values of the heat of fusion as well as entropy of fusion, it was concluded that packing of the side groups in the crystal structure increases as the size of the branched alkyl group increases. TGA evidenced a negative effect of the branching of the alkyl chain on the thermal stability in air.

Synthesis and characterization of new semifluorinated linear and hyperbranched poly(arylene ether phosphine oxide)s through B 2 + A 2 and AB 2 approaches

A new phosphorus containing trifluoromethyl-activated bisfluoro B 2 monomer has been synthesized successfully by coupling reaction of 4-methoxyphenylphosphonic dichloride and the Grignard salt of 5-bromo-2-fluorobenzotrifluoride. This monomer was converted to linear poly(arylene ether phosphine oxide)s by nucleophilic displacement of the fluorine atom on the benzene ring with several diphenols. The B 2 monomer was further demethylated to form an AB 2 monomer which on self condensation yielded hyperbranched poly(arylene ether phosphine oxide) with identical phosphorous containing moiety. The products obtained exhibit weight-average molecular weights as high as 600,000 g mol −1 in SEC. These linear and hyperbranched poly(arylene ether phosphine oxide)s showed thermal stability as high as 516 °C for 10% weight loss in TGA in nitrogen and showed glass transition temperatures up to 253 °C in DSC. All the polymers were soluble in a wide range of organic solvents, e.g., CHCl 3, THF, NMP and DMF, however, the hb sample showed a significant lower solution viscosity compared to linear samples of similar molar mass. Transparent thin films of linear poly(arylene ether phosphine oxide)s casted from dichloromethane exhibited tensile strengths up to 50 MPa, a modulus of elasticity up to 0.95 GPa and elongation at break up to 36% depending on their exact repeating unit structures. No free standing films could be prepared from the hb analogue due to the missing entanglements, but stable thin polymer films on silicon wafers with high hydrophobicity were formed which showed water contact angles as high as 91°.

Structure of the condensed phase and char of fire-retarded PBT nanocomposites by TGA/ATR in N 2

Recently phosphorous-based fire retardants and nanoparticles are promoted as alternatives to halogenated fire retardants to reduce toxicological damage to the environment. To assess the condensed phase during pyrolysis, this study presents thermal (by TGA in nitrogen) and condensed phase analyses of the residue (by FTIR–ATR) of PBT modified by a phosphinate FR and/or nanoparticles (sepiolite). The thermal analysis shows that the nanoparticles do not change the pyrolysis kinetics of PBT whereas the phosphinate FR does. The condensed phase analysis shows that both the phosphinate FR and the nanoparticles change the structure of the char compared to the structure of the char from pure PBT. In contrast to the pure polymer, which leaves a char consisting of oligomeric components of PBT, the fire-retarded polymer (by phosphinate and /or nanoparticles) leaves a char consisting of polycyclic aromatic hydrocarbons (PAH). The PAH structure of the char is expected to make the char stronger and capable to withstand erosion in full-scale fire tests. This observation is verified from the strength analysis of the char residue in intermediate-scale flammability experiments, such as those in the cone calorimeter, where char is formed behind the flames in the absence of oxygen.

Synthesis and Characterization of Novel Organosoluble Polychloro Substituted Aromatic Poly(Ether Ketone)s

AbstractA novel monomer of tetrachloroterephthaloyl chloride (TCTPC) was prepared by the chlorination of terephthaloyl chloride catalyzed by ferric chloride at 175‐180 °C for 10 h, and confirmed by FTIR, MS and elemental analysis. A series of new polychloro substituted poly(aryl ether ketone)s with inherent viscosities of 0.58‐0.65 dL/g have been prepared from TCTPC with aromatic ether monomers by electrophilic Friedel‐Crafts acylation in the presence of DMF with anhydrous AlCl3 as a catalyst in 1,2‐dichloroethane. Glass‐transition temperatures of these polychlorinated polymers ranged from 267 to 280 °C by DSC. The degradation temperature at 5% weight loss by TGA in nitrogen for these polymers ranged from 486 to 534 °C, and the char yields at 700 °C were 54‐65%. The polymers having a weight‐average molecular weight in the range of 65,900‐79,300 are all amorphous and readily soluble in polar solvents such as DMF, DMSO and NMP at room temperature. All the polymers formed transparent, strong, and flexible films, with tensile strengths of 86.1‐99.7 MPa, Young's moduli of 2.32‐3.35 GPa, and elongations at break of 10‐15%.

Palladium-catalyzed silation of adamantanedi- and triol, leading to adamantane–siloxane alternating polymers with high heat resistance

Palladium-catalyzed dehydrocoupling reactions of 1,3-adamantanediol (Ad(OH)2) with excess amounts of PhMeSiH2 and PhSiH3 gave silated products, Ad(OSiPhMeH)2 and Ad(OSiPhH2)2, respectively, in good yield. 1,3,5-Adamantantriol (Ad(OH)3) also underwent silation with PhMeSiH2 under the same conditions. When silation of Ad(OH)2 was carried out with 1equiv of PhSiH3, a polymer consisting of a repeating unit of –O–Ad–OSi(OH)Ph– was obtained. The polymer thus obtained showed high heat resistance and Td5=420°C and Td10=512°C were noted by its TGA in nitrogen. It was also found that thermal stability of the polymer was improved by using Ad(OH)3 as a comonomer.

A fluorescent copolyimide containing perylene, fluorene and oxadiazole units in the main chain

A quaternary copolyimide containing perylene, fluorene and oxadiazole units in the backbone, named as OPFF x, was designed and synthesized by a one-step polycondensation under high temperature. The successful polymerization was proved by both elemental analysis and FT-IR spectra. Weight average molecular weight of the polymer was in the range of 2.02–3.09 × 10 4 as measured by GPC. OPFF x with low oxadiazole content has good solubility in common organic solvents such as chloroform and tetrahydrofuran. Thin film of OPFF x could be prepared by directly spin-coating of its chloroform solution onto quartz glass. The polymer showed high thermal stability and the temperature of 10% weight loss was higher than 494 °C as measured by TGA in nitrogen, and no apparent glass transition temperature was observed from DSC measurement in nitrogen up to 350 °C. The film of OPFF x irradiated by ultraviolet light emitted strong reddish-orange fluorescence. Cyclic voltammetry measurement indicated that OPFF x could be easily reduced ( n-doped). Thus, the polymer may potentially be used as a thermal stable light-emitting and electron transporting material for light-emitting diodes.

Photosensitive poly(amic acid)/organoclay nanocomposites

A project was carried out aimed at reducing the coefficient of thermal expansion (CTE) of photosensitive polyimide formulations (photoresists) through the incorporation of small amounts of an organoclay. The organoclay was formed by a cation exchange reaction between a NA+-montmorillonite clay and an ammonium salt of dodecylamine. Two polyimide precursors, a poly(amic ester) (PAE) and a poly(amic acid) (PAA), were used in this study. The PAE was prepared by direct polymerization of 2,2′-bis-(3-amino-4-hydroxyphenyl)hexafluoropropane and bis(n-butyl)ester of pyromellitic acid in the presence of phenylphosphonic dichloride as an activator. The polymer had an inherent viscosity of 0.23dL/g. The PAA copolymer was prepared by polymerization of pyromellitic dianhydride, oxydiphthalic anhydride and oxydianiline. The polymer had an inherent viscosity of 1.00dL/g. Two photosensitive resin/clay formulations were prepared from these two PI precursors using 2,3,4-tris(1-oxo-2-diazonaphthoquinone-5-sulfonyloxy)-benzophenone as the photosensitizer and 3wt% organoclay. The films obtained from the PAA formulation were transparent and tough, while the films prepared from the PAE formulation were opaque and brittle. Both X-ray diffraction and transmission electron microscope analyses showed that, although the organoclay was not dispersed well in the PAE matrix, it was dispersed in the PAA matrix on a nanometer scale. The clay particles remained well dispersed after the PAA film was thermally imidized. The CTE of the polyimide film obtained was 23% lower than that of a similar film that did not contain the organoclay. The temperature at which the polyimide underwent a 5% weight loss when subjected to TGA in nitrogen was also increased by 13%. The photosensitive PAA/clay nanocomposite showed a sensitivity of 301mJ/cm2 and a contrast of 1.66 when a 0.2wt% tetramethylammonium hydroxide developer was used. A line/space pattern with a resolution of 10 μm was obtained from this formulation.

Preparation and properties of polymers of carboxylated polybutadiene containing sucrose

This paper describes the attachment of sugar (sucrose) to low molecular weight carboxylated polybutadiene (esterification) to produce a new class of synthetic polymers. The products were characterized by I.R. and N.M.R. spectroscopy. Their thermal and thermooxidative characteristics are discussed from DSC and TGA in nitrogen and air. The polyurethanes obtained were studied.