Synthesis and thermal decomposition of poly(dodecamethylene terephthalamide)

A kind of semiaromatic polyamide, poly(dodecamethylene terephthalamide) (PA12T) was synthesized via a polycondensation reaction of terephthalic acid and 1,12‐dodecanediamine. The structure of prepared PA12T was characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance (¹H‐NMR), and elemental analysis. The mechanical properties of PA12T were also studied. The thermal behavior of PA12T was determined by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. Pyrolysis products and thermal decomposition mechanism of PA12T were analyzed by pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS). Melting temperature (T_m), glass transition temperature (T_g), and decomposition temperature (T_d) of PA12T are 310°C, 144°C, and 429°C, respectively. The Py‐GC/MS results showed that the pyrolysis products were mainly composed of 32 kinds of compounds, such as benzonitrile, 1,4‐benzenedicarbonitrile, N‐methylbenzamide, N‐hexylbenzamide, and aromatic compounds. The major pyrolysis mechanisms were β‐CH hydrogen transfer process, main‐chain random scission, and hydrolytic decomposition. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Effects of the injection‐molding temperatures and pyrolysis cycles on the butadiene phase of high‐impact polystyrene

Recycling is a thermal process in which polymers are melted to produce new products. It is possible that these thermal processes could modify their mechanical and thermal properties. Polymer degradation can be characterized with thermogravimetric analysis and differential scanning calorimetry. Recycled materials tested with these methods have shown variations in some thermal properties, such as the glass‐transition temperature and thermal degradation onset, but the sensitivity of these methods is not sufficient to investigate the changes in the characteristics of polymers when materials are exposed to moderate temperature conditions or several thermal cycles. To study these structural changes, a much more sensitive technique, such as pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS), is needed. Small variations in the structure can be determined by Py–GC/MS. Each pyrolysis product can be identified by its retention time and mass spectrum with the use of reference literature. In this work, we have studied structural changes in high‐impact polystyrene as a function of the injection‐molding temperature and pyrolysis cycles. The results do not show significant changes in samples processed at different temperatures with Py–GC/MS, but the values of the pyrolysis products differ as a function of the pyrolysis cycles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effect of ultrafine zinc borate on the smoke suppression and toxicity reduction of a low‐density polyethylene/intumescent flame‐retardant system

The production of smoke, carbon monoxide (CO), and carbon dioxide (CO₂) were investigated with cone calorimetry testing when low‐density polyethylene (LDPE), LDPE treated with an intumescent flame retardant (IFR), and LDPE treated with an IFR and ultrafine zinc borate (UZB) combusted under irradiation. The results of the testing showed that UZB could depress smoke production and reduce the amount of CO and CO₂. The components of the pyrolytic gas and its contents were identified and measured with pyrolysis–gas chromatography/mass spectrometry (Py–GC–MS) when LDPE, LDPE/IFR, and LDPE/IFR/UZB were pyrolyzed at 400°C for 20 s. The Py–GC–MS results implied that UZB had an important influence on the components and contents of the pyrolytic gas of LDPE/IFR. UZB mechanisms of smoke suppression and toxicity reduction with respect to LDPE/IFR are proposed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

An effective flame retardant for poly(ethylene terephthalate) synthesized by phosphaphenanthrene and cyclotriphosphazene

A novel flame retardant [9,10‐Dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxideÔtriphosphazene (DOPO–TPN)] based on phosphaphenanthrene and cyclotriphosphazene was synthesized and used to improve the flame retardancy of poly(ethylene terephthalate) (PET). The structure of DOPO–TPN was characterized by nuclear magnetic resonance, Fourier transform infrared spectroscope (FTIR), and elemental analysis. PET/DOPO–TPN composites with different amount of DOPO–TPN were prepared and the flame retardancy was determined by limiting oxygen index (LOI) and vertical burning test (UL‐94). With the incorporation of 5 wt % DOPO–TPN, the composite achieved a LOI value of 34% and UL‐94 V‐0 rating. The thermal properties of the PET/DOPO–TPN composites were investigated by thermogravimetric analysis. The flame retardant mechanism was investigated by pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS), FTIR, and scanning electron microscopy (SEM). The Py‐GC/MS results showed that DOPO based fragments would exist in the gas phase during the pyrolysis of PET/DOPO–TPN composites which demonstrated that DOPO–TPN could act through gas‐phase action to exert flame retardant effect. The results of FTIR and SEM demonstrated that DOPO–TPN could promote the formation of compact and intact char residues to inhibit the heat and combustible gas transmission in condensed phase. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45246.     

Identification and Characterization of Phospholipids with Very Long Chain Fatty Acids in Brewer’s Yeast

Yeast lipids and fatty acids (FA) were analyzed in Saccharomyces pastorianus from seven breweries and in the dietary yeast supplement Pangamin. GC–MS identified more than 30 FA, half of which were very‐long chain fatty acids (VLCFA) with hydrocarbon chain lengths of ≥22 C atoms. Positional isomers ω‐9 and ω‐7 were identified in FA with C18–C28 even‐numbered alkyl chains. The most abundant ω‐7 isomer was cis‐vaccenic acid. The structure of monounsaturated FA was proved by dimethyl disulfide adducts (position of double bonds and cis geometric configuration) and by GC–MS of pyridyl carbinol esters. Ultra‐high performance liquid chromatography‐tandem mass spectrometry with negative electrospray ionization identified the phospholipids phosphatidylethanolamine, phosphatidylinositol and phosphatidylcholine, with more than 150 molecular species. Wild‐type unmutated brewer's yeast strains conventionally used for the manufacture of food supplements were found to contain VLCFA.     

Study on the grafting of PET onto the glass fiber surface during in situ solid‐state polycondensation

An in situ solid‐state polymerization process was developed to produce long glass fiber reinforced poly(ethylene terephthalate) (PET) composites. As reported in our last article, one advantage of this new process is that the good wetting of reinforcing fiber can be obtained for using low‐viscosity oligomer as raw materials. In this article, the grafting of PET macromolecular chain onto the surface of reinforcing glass fiber during in situ solid‐state polycondensation (SSP) will be investigated, which was believed to be another advantage for this new process and should be very important for thermoplastic composite. The reinforcing glass fiber after removing ungrafted PET from a long glass fiber reinforced PET composite by solvent extraction was investigated by SEM, pyrolysis‐gas chromatography mass spectrometry (Py‐GC/MS), DSC, and FTIR. The information from morphology of SEM photos of glass fiber surface, the spectrum of Py‐GC/MS, the melt peak at differential scanning calorimetric (DSC) curve, and the spectrum of Fourier transform infrared Raman spectroscopy (FTIR) gave a series evidence to prove the presence of grafted PET layer on the surface of silane‐coupling‐treated glass fiber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 775–781, 2006     

Heat Treatment Effect on Lignin and Carbohydrates in Corsican Pine Earlywood and Latewood Studied by PY–GC–MS Technique

Lignin-derived degradation products from non-treated (NT) and heat-treated (T) Corsican pine (Pinus nigra subsp. laricio) obtained by pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) were investigated, whereby the earlywood (EW) and latewood (LW) parts of the annual ring were considered separately. The data evaluation was done by principal component analysis (PCA) and the Kruskal–Wallis test. There are no differences in the pyrolysis products composition between EW and LW, but NT and T samples were discernible by PCA applied to Py–GC–MS data. Less phenols with longer chains (4-vinylguaiacol, and trans-isoeugenol) than those with shorter chains (guaiacol, 4-methylguaiacol) and an increase of anhydrosugar (AHS) were found among the pyrolysis products after heat treatment. These signs for autocondensation and side chain cleavages in the lignin during heat treatment were more evident in the EW than in the LW and for the crystallization of cellulose. A slight decrease of the carbohydrate/lignin ratio (C/L) after heat treatment indicates a greater degradation of carbohydrates compared to lignin. The relation of pyrolysis products of lignin and mechanical properties of wood was evaluated by regression analysis. An inverse correlation between short-chain phenols and MOE and a direct correlation between long-chain phenols and compression strength was found in case of NT wood, while a weak positive correlation could be observed between short-chain phenols and the density in T wood.     

Synthesis,characterization, and pyrolysis of ferrocenyl unit containing organosilicon polymers

New polyferrocenylsiloxanes (PFSXs) and polyferrocenylsilazanes (PFSZs) with linear or linear‐cyclic structure were prepared. The ceramic yields of the polymers were estimated by thermogravimetric analysis (TGA) and bulk pyrolysis, which closely depend on molecular structures. Compared with that of their linear counterparts having comparable molecular weights, the ceramic yields of linear‐cyclic PFSX and PFSZ were much higher. The pyrolysis process was investigated by lysis character is (TGA) highly depend on their molecular weights and structures, infrared spectra, and pyrolysis‐gas chromatography‐mass spectra (Py‐GC‐MS) analysis. The results indicated rather amount of ferrocene‐based small molecules were formed during the pyrolysis of linear polymers in the range of 25–300°C, whereas the existence of crosslinking or branched structure in the linear‐cyclic polymers prohibited this transformation, and therefore, dramatically improved the ceramic yields. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

PY‐GC/MS an effective technique to characterizing of degradation mechanism of poly (L‐lactide) in the different environment

The biotic and abiotic degradation of poly (L‐lactide) (PLLA) has been studied with pyrolysis gas chromatography mass spectrometry (Py‐GC‐MS). A mixed culture of compost micro‐organisms was used as the biotic medium. Size‐exclusion chromatography (SEC), gas chromatography‐mass spectrometry (GC‐MS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were utilized to monitor the degradation and degradation mechanism. Differences in pH, molecular weight, surface structure, and degradation mechanisms were noted between sample aged in biotic and abiotic medium. Using fractionated Py‐GC‐MS at 400 and 500°C, acetaldehyde, acrylic acid, lactoyl acrylic acid, two lactide isomers, and cyclic oligomers up to the pentamer were identified as thermal decomposition products of PLA as well as some other not completely identified products. The ratio of meso‐lactide to L‐lactide was lower in the sample aged in the biotic media than the abiotic media. This is a result of the preference of the micro‐organisms for L‐form of lactic acid and lactoyl lactic acid rather than the D‐form that in turn influences the formation and the amounts of meso and D,L‐lactide during the pyrolysis. Based on SEM micrographs, it was shown that degradation in the biotic medium proceeded mainly via a surface erosion mechanism, whereas bulk erosion was the predominant degradation mechanism in the abiotic medium. The SEC and Py‐GC‐MS data indicate that degradation was faster in the biotic than in the abiotic sample. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2369–2378, 2000     

A facile one‐step method for spherical support preparation of Ziegler‐Natta catalyst

This study reports a novel one‐step method to synthesize a new spherical support for Ziegler‐Natta catalyst under moderate condition. The support is obtained from a dispersion system where the particle stabilizer polyvinylpyrrolidone plays a main role to stabilize the spherical particles. The new chemical of the support is CH₃CH₂OMgOCH(CH₂Cl)₂, which is first reported here, has been approved by newly filed patents and also confirmed by solution NMR, solid state NMR, pyrolysis‐gas chromatography‐mass spectrometry (Py‐GC‐MS), and ICP‐MS. The support and catalyst particles have uniform distributions. The catalyst prepared from this support has been evaluated with high activity. The polypropylene obtained has high isotacticity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41014.     

Pyrolysis studies of polyethylene terephthalate/silica nanocomposites

The decomposition of pure polyethylene terephthalate (PET) and PET/silica nanocomposites was investigated by thermal gravimetry (TG) and pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS). The influence of the nanosized silica on the pyrolysis properties of the composites was found from the results that the activation energies of decomposition and the residual carbon content increase with silica nanoparticles. It is deduced that the increase of the activation energies and the residual carbon content result from the adsorption of the decomposed products on the surface of silica. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Flame retardancy of poly(butylene terephthalate) blended with phosphorous compounds

The thermal degradation and flame retardancy of poly(butylene terephthalate) (PBT) were studied with a focus on the effect of phosphorous compounds. Thermogravimetric analysis, pyrolysis/gas chromatography/mass spectrometry (Py/GC/MS), and elemental analysis were used to analyze the flame retardancy, which were observed by an Underwriters Laboratory UL‐94 test and a cone calorimeter. The 50% degradation temperatures of PBT blends with phosphorous compounds were the same as that of neat PBT. Six scission products were assigned by Py/GC/MS. The burning times of the UL test of several PBT blends were much shorter than that of neat PBT. The relation between flame retardancy and thermal degradation was analyzed with respect to the results of the scission products and the char in burned polymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2326–2333, 2004     

Flame retarding mechanism of Polyamide 6 with phosphorus‐nitrogen flame retardant and DOPO derivatives

A novel flame‐retardant composite was prepared by introducing a phosphorus‐nitrogen flame retardant and DOPO‐SiO₂ into PA6. DOPO‐SiO₂ was synthesized successfully in a one‐step process. PA6/OP1314/DOPO‐SiO₂ achieved a UL 94 V‐0 rating with an LOI value of 31%. The maximum mass loss rate of decomposition decreased significantly and char residue increased to 11.6 wt % compared with that of pure PA6. The compacted and dense char was formed due to the combination of the P‐N flame retardant and DOPO‐SiO₂. The complex viscosity of PA6/OP1314/DOPO‐SiO₂ increased considerably which tend to prevent the dripping phenomenon. The flame‐retardant mechanism of PA6/OP1314/DOPO‐SiO₂ was also investigated by Fourier transform infrared spectroscopy FTIR at different temperatures and the pyrolysis products were investigated by pyrolysis gas chromatography/ mass spectrum (Py‐GC/MS). It was assumed that DOPO‐SiO₂ and the hypophosphite of OP1314 possess excellent flame retardancy during the gaseous phase. Meanwhile, melamine and phosphate reacted with the pyrolytic products of PA6 to protect the matrix during the condensed phase. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42932.     

Thermal degradation mechanism of poly(ether imide) by stepwise Py–GC/MS

The thermal degradation of poly(ether imide) (PEI) was studied through a combination of thermogravimetric analysis and stepwise pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) techniques with consecutive heating of the samples at fixed temperature intervals to achieve narrow temperature pyrolysis conditions. The individual mass chromatograms of various pyrolysates were correlated with pyrolysis temperatures to determine the pyrolysis mechanism. The major mechanisms were two‐stage pyrolysis, involving main‐chain random scission, and carbonization. In the first stage, the scission of hydrolyzed imide groups, ether groups, and isopropylidene groups produced CO+CO₂ and phenol as the major products and was accompanied by chain transfer of carbonization to form partially carbonized solid residue. In the second pyrolysis stage, the decomposition of the partially carbonized solid residue and remaining imide groups formed CO+CO₂ as the major product along with benzene and a small amount of benzonitrile. The yield of CO+CO₂ was the largest fraction in the total ion chromatogram of the evolved gas mixtures. Hence, the thermal stability of the imide group was identical to the maximum thermogravimetry loss rates in the two‐stage pyrolysis regions. Afterward, carbonization dominated the decomposition of the solid residue at high temperatures. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1151–1161, 2001     

Evaluation of the phytomass source for composite preparation

The properties of lignocellulose materials from the trunk and bark of trees, and from agricultural sources were investigated by thermogravimetry (TG) and pyrolysis–gas chromatography/mass spectrometry (Py‐GC/MS). The goal was to learn which of the phytomass sources is the most accessible to dehydration and aldol reactions, and in this way could be considered suitable for composite preparation by the thermal pressing treatment. The bagasse second differential thermal analysis peak in air is at the highest temperature acceptable for intermolecular dehydration/crosslinking, and therefore we consider bagasse to be the most suitable candidate for composite preparation. From the TG results in air at 250°C, it follows that willow wood and bagasse are the most thermally resistant sources. The data obtained by Py‐GC/MS analysis showed glycolaldehyde and acetic acid as dominant markers related to adhesion properties via aldol condensation. The detected sum amount of glyceraldehyde and acetic acid decreases in the order: beech wood > bagasse > acacia wood > sugar beet pulp, whereas the remaining species produced much less of it. By comparing results run at above conditions with composite preparation using the pressing thermal treatment at a temperature of 150°C and pressures up to 800 kPa, the suggested evaluation was examined for application on sugar beet residue. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Viscoelastic properties of Japanese lacquer film

The storage modulus (E′) and loss modulus (E″) of Japanese lacquer films were measured over a temperature range of −150 to 400°C. Three relaxation processes labeled α, β, and γ were detected at 80, −60, and −140°C, and their apparent activation energies (ΔE) were 63–91, 13, and 9 kcal/mol, respectively. These were attributed to the micro-Brownian motions of polymerized urushiol, the molecular motion related to the absorbed water, and the motions of methylene groups in the side chains, respectively. With aging at room temperature, the location of the α peak shifted to higher temperature and its ΔE value decreased. This result was ascribed to the autoxidative polymerization of urushiol. The E′ of lacquer films increased with heat treatments at 100°C or above. When treated at temperatures below 200°C, the location of the α peak shifted to higher temperature, with a reduction in the ΔE value. Heat treatments at 200°C or above resulted in remarkable shrinkage and weight loss of films owing to the pyrolysis of lacquer constituents. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1727–1732, 1999     

Synthesis of ω‐amino‐α‐phenylcarbonate alkanes and their polymerization to [n]‐polyurethanes

Aliphatic [n]‐polyurethanes have recently been synthesized from ω‐isocyanato‐α‐alkanols or, more traditionally, by cationic ring‐opening polymerization of cyclourethanes or by the Bu₂Sn(OMe)₂‐promoted polycondensation of ω‐hydroxy‐α‐O‐phenylurethane alkanes. For the latter procedures, the conditions employed do not seem to be suitable for highly functionalized monomers. In contrast, the polymerization of ω‐amino‐α‐phenylcarbonate alkanes is expected to occur under milder conditions. ω‐Amino‐α‐phenylcarbonate alkanes have been synthesized from 6‐aminohexanol (1) and 3‐aminopropanol (6). The procedure involves the N‐Boc protection of the amino group, followed by activation of the alcohol. Removal of the N‐Boc affords the corresponding ω‐amino‐1‐O‐phenyloxycarbonyloxyalkane hydrochlorides. Other oligomeric comonomers between 1 and 6 have been prepared. The polymerization of these precursors takes place in the absence of metal catalysts to afford the corresponding linear and regioregular [n]‐polyurethanes. The procedure described is useful for the preparation of stable ω‐amino‐α‐phenylcarbonate alkane derivatives, which possess varied chain lengths between the terminal functions. These monomers yield [n]‐polyurethanes having various structures starting from just two aminoalkanols. The polyurethanes were obtained in high yields, with reasonable molecular weight and polydispersity values, and they were characterized spectroscopically and thermally. These studies reveal constitutionally uniform structures that are free of carbonate or urea linkages. Copyright © 2010 Society of Chemical Industry     

Synthesis of two Unique Compounds,a Ceramide and a Cerebroside,Occurring in Human Stratum Corneum

The cerebroside 1a and the ceramide 1b , both playing important roles in epidermal barrier function, were synthesized by N‐acylation of 1‐O‐glucosylated C₁₈‐sphingosine 2 and C₁₈‐sphingosine 8 , respectively, with O‐acyl fatty acid 3 . The required compound 3 was obtained from ω‐hydroxy fatty acid 6 and linoleic acid 7 by esterification. The ω‐hydroxy C₃₀‐fatty acid 6 was prepared as follows: Copper‐catalyzed coupling of ω‐hydroxy alkyl halide 11 with the Grignard reagent derived from bromo compound 13 afforded after oxidation C₁₇‐aldehyde 15 . Wittig reaction with phosphonium salt 10 , derived from ω‐bromo‐tridecanoic acid 9 , and subsequent hydrogenation and O‐deprotection furnished 6 in high yield.     

Structure and properties of ultra‐high molecular weight bisphenol a polycarbonate synthesized by solid‐state polymerization in amorphous microlayers

The structure and properties of ultrahigh molecular weight polycarbonate synthesized by solid‐state polymerization in micro‐layers (SSP_m) are reported. A low molecular weight prepolymer derived from the melt transesterification of bisphenol A and diphenyl carbonate as a starting material was polymerized to highly amorphous and transparent polycarbonate of molecular weight larger than 300,000 g mol^?1 in the micro‐layers of thickness from 50 nm to 20 µm. It was observed that when the polymerization time in micro‐layers was extended beyond conventional reaction time, insoluble polymer fraction increased up to 95%. Through the analysis of both soluble and insoluble polymer fractions of the high molecular weight polycarbonate by ¹H NMR spectroscopy and pyrolysis‐gas chromatography mass spectrometry (Py‐GC/MS), branches and partially crosslinked structures have been identified. The thermal, mechanical and rheological properties of the ultra‐high molecular weight nonlinear polycarbonates synthesized in this study have been measured by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and rheometry. The nonlinear chain structures of the polymer have been found to affect the polymer's thermal stability, mechanical strength, shear thinning effect, and elastic properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41609.     

Comparison of thermal degradation characteristics of poly(arylene sulfone)s using thermogravimetric analysis/mass spectrometry

Thermal degradation of poly(arylene sulfone)s had been studied by the combination of thermogravimetric analysis/mass spectrometry (TG/MS) with pyrolysis/gas chromatography/mass spectrometry (Py‐GC/MS) techniques. Through these two methods, the pyrolysates from poly(ether sulfone) (PES) and polysulfone (PSF) were identified in 11 and 21 sets of evolution curves, respectively, from room temperature to 900 °C. Among these pyrolysates, 12 products from PES and 25 products from PSF were obtained. The major mechanism for both PES and PSF was one‐stage pyrolysis involving main chain random scission and carbonization with evolution of SO₂ and phenol as major products. Although the initial thermal stability of PES was lower than that of PSF, the formation of sulfide groups in the condensed phase from PES, through reduction of sulfone group by hydrogen radicals, increased the fire retardation behavior of PES. In PES, the ether and sulfone groups showed similar thermal stability. The thermal stability of functional groups in PSF were in the order of sulfone < ether < isopropylidene group. The scission of the ether group in PSF, with evolution of phenol as the major product, reached maximum evolution amount at the temperature of the maximum thermogravimetry loss of TG (T_max). The scission of isopropylidene groups at high temperature (>580 °C) evolved higher mass derivatives that lower the fire retardancy of PSF. By using a simplified kinetic model, PES showed maximum activation energy with a conversion ratio of 0.2–0.3, which implies a high fire retardant effect of sulfide formation in PES. A comparative study with the proposed model and experimental data showed the theoretical pyrolysis curves to be in agreement with the experimental curves for PES and PSF pyrolysis, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2387–2398, 2001