Thermal Volatilization Research Articles

Thermal decomposition of cyclotriphosphazenes. I. Alkyl-aminoaryl ethers

1,3,5-Triisopropoxy-1,3,5-tris(4-aminophenoxy)-cyclotriphosphazene-[CTP (I)], 1,3,5-trineopentoxy-1,3,5-tris(4-aminophenoxy)-cyclotriphosphazene [CTP (II)], and 1,1,3,5-tetraneopentoxy-3,5-bis(4-aminophenoxy)-cyclotriphosphazene [CTP (III)] were prepared from hexachlorotricylophosphazene. Thermal decomposition of the crude CTP (I), CTP (II), and CTP (III) was studied by thermogravimetry, differential scanning calorimetry, and thermal volatilization analysis. Solid, gaseous, and high boiling degradation products were collected at different steps of thermal decomposition and identified by using infrared and gas chromatography mass spectrometry. On heating to 600°C, CTP (I) shows three main steps of weight loss, whereas both CTP (II) and CTP (III) show two overlapping steps. The first step of thermal decomposition of CTP (I) is observed at 150–200°C, where elimination of part of the aliphatic substituents and polymerization of the CTP (I) occurs. The opening of tricyclophosphazene rings at 220–370°C provokes further elimination of aliphatics and ammonia and formation of crosslinked structures. Phosphorus oxynitride structure bonded with carbonized polyaromatics is formed in the third step of thermal decomposition, accompanied by the elimination of aromatics and chain fragments at 400–500°C. In the case of CTP (II) and (III), simultaneous evaporation of virgin CTPs, opening of the phosphazene ring, and elimination of aliphatic substituents with the formation of crosslinked polymeric structures occur at 210–350°C. A phosphorus oxynitride-aromatic carbonized structure similar to that from CTP (I) is formed at 350–600°C. The process is accompanied by the elimination of aromatics and chain fragments. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 461–472, 1998

Thermal decomposition of cyclotriphosphazenes. I. Alkyl‐aminoaryl ethers

1,3,5-Triisopropoxy-1,3,5-tris(4-aminophenoxy)-cyclotriphosphazene-[CTP (I)], 1,3,5-trineopentoxy-1,3,5-tris(4-aminophenoxy)-cyclotriphosphazene [CTP (II)], and 1,1,3,5-tetraneopentoxy-3,5-bis(4-aminophenoxy)-cyclotriphosphazene [CTP (III)] were prepared from hexachlorotricylophosphazene. Thermal decomposition of the crude CTP (I), CTP (II), and CTP (III) was studied by thermogravimetry, differential scanning calorimetry, and thermal volatilization analysis. Solid, gaseous, and high boiling degradation products were collected at different steps of thermal decomposition and identified by using infrared and gas chromatography mass spectrometry. On heating to 600°C, CTP (I) shows three main steps of weight loss, whereas both CTP (II) and CTP (III) show two overlapping steps. The first step of thermal decomposition of CTP (I) is observed at 150–200°C, where elimination of part of the aliphatic substituents and polymerization of the CTP (I) occurs. The opening of tricyclophosphazene rings at 220–370°C provokes further elimination of aliphatics and ammonia and formation of crosslinked structures. Phosphorus oxynitride structure bonded with carbonized polyaromatics is formed in the third step of thermal decomposition, accompanied by the elimination of aromatics and chain fragments at 400–500°C. In the case of CTP (II) and (III), simultaneous evaporation of virgin CTPs, opening of the phosphazene ring, and elimination of aliphatic substituents with the formation of crosslinked polymeric structures occur at 210–350°C. A phosphorus oxynitride-aromatic carbonized structure similar to that from CTP (I) is formed at 350–600°C. The process is accompanied by the elimination of aromatics and chain fragments. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 461–472, 1998

Thermal degradation of poly(vinyl chloride) plastigels

An emulsion, poly(vinyl chloride) (PVC), was analyzed for its components and was used in the preparation of flexible PVC plates utilizing sol-gel processing technology. PVC contained an ether-soluble fraction having carboxylic acid carbonyl groups, a tetrahydrofurane (THF)-insoluble fraction having —COO− groups, and 0.15% aluminum. PVC was mixed with dioctyl phthalate (DOP) in a 0.3–0.8 DOP/PVC weight ratio and heated at 180°C for gelation. The yellowness index (YI) and tensile strength of the plastigels were increased with both heating time and DOP concentration. Infrared (IR) spectroscopy showed that the thermal oxidation and volatilization of DOP occurred simultaneously with dehydrochlorination of PVC upon heating of the plastigels. Agglomeration of PVC particles on mixing with DOP at low DOP levels caused longer gelation times than expected. © 1998 John Wiley & Sons, Inc. Adv in Polymer Techn 17: 63–71, 1998

A detailed analysis of the pyrolysis products from dioctyltin maleate and its mixture with PVC

The thermal decomposition of dioctyltin maleate (DOTM) and a blend of PVC and DOTM has been studied in air, nitrogen and under vacuum. TG was used to examine the effect of different amounts of DOTM on stability. The PVC/DOTM mixture shows delayed dehydrochlorination in both the air and inert environment compared with PVC. The blend shows more thermal stability in an inert atmosphere than in air. The decomposition products from a blend containing a high loading of DOTM were investigated using Thermal Volatilisation Analysis (TVA) and Subambient Thermal Volatilisation Analysis (SATVA). Gas, liquid and tar fractions were separated and analysed by IR spectroscopy, on-line mass spectrometry or GC-MS. High molecular weight polycyclic aromatic hydro-carbons (PAH) found in the pyrolysis of pure PVC were not found from the blend. The pyrolysis in the presence of air rather than inert atmosphere does not change the nature of the products, although the relative amounts may be different. Traces of oxygen-containing volatile products are formed from the blend, while most of the oxygen-containing groups formed in the polymer pass into the tar as large fragments split from the crosslinked network. Dioctytin dichloride is the most important product apart from HCl from the pyrolysis of the PVC DOTM mixture.

Thermal degradation studies of alternating copolymers—V. Degradation of the alternating copolymer of isopropenyl acetate and maleic anhydride

The thermal degradation of the alternating copolymer of isopropenyl acetate and maleic anhydride has been investigated using thermal volatilisation analysis (TVA), thermogravimetry (TG) and differential scanning calorimetry (DSC) under vacuum and nitrogen conditions using programmed heating up to 500 °C. The decomposition products, i.e. gas, liquid and tar fractions, have been separated and then analysed by GC-MS and FTIR spectroscopy. The structural changes in the copolymer during degradation at various temperatures up to 440 °C and also for isothermal heating for various periods at 170 °C have been investigated by FTIR spectroscopy.The alternating copolymer of IPA-MAn degrades in two main stages as the temperature is progressively raised. In the first stage up to about 260 °C, the acetate groups are completely eliminated from the isopropenyl units through side group reactions whilst leaving the backbone intact. Above 260 °C, the anhydride groups break down producing large quantities of CO 2 and CO along with gradual breakdown of the backbone to give a variety of other products. Unlike the homopolymer of isopropenyl acetate, the IPA-MAn copolymer leaves a significant amount of residue after 500 °C.By controlled degradation at 170 °C, acetate groups can be removed without decomposition of the MAn units, to produce what is in effect a new copolymer of regular structure with backbone double bonds conjugated to the anhydride carbonyls.

Thermal degradation of poly[2-(3-aryl-3-methylcyclobutyl)-2-hydroxyethyl methacrylate

Thermal degradations of poly[2-(3-phenyl-3-methylcyclobutyl)-2-hydroxyethyl methacrylate] [poly(PHEMA)], poly[2-(3-mesityl-3-methylcyclobutyl)-2-hydro-xyethyl methacrylate] [poly(MHEMA)] and poly[2-(3-tolyl-3-methylcyclobutyl)-2-hydroxyethyl methacrylate] [poly(THEMA)] have been studied using IR spectroscopy and thermogravimetry (TG). Programmed heating was carried out at 10 °C/min from room temperature to 500 °C. All the partially degraded polymers have been examined by IR spectroscopy. Thermal degradation of poly(PHEMA) has also been studied by thermal volatilisation analysis (TVA). In degradation of poly(PHEMA) and poly(MHEMA), product identification studies were done using IR, 1H and 13C-NMR, MS and GC-MS techniques. Depolymerization is the main reaction in thermal degradation of all three polymers up to about 300 °C. Intramolecular cyclisation to cyclic anhydride-type structures has been observed at temperatures above 300 °C. The cleaving of epoxide, ketone and diol compounds from side chains of the polymers is a common reaction for each of the polymers.

Combined hydro-pyrometallurgical method for the recovery of high lead/tin/bronze alloy from industrial scrap

The major item of concern of this work was to recover bronze alloys meeting DIN 1617 as specified applying combined hydrometallurgical and pyrometallurgical treatments. The hydrometallurgical leaching process utilizes hydrogen peroxide in ammonia to dissolve copper selectively. Lead and tin are then leached with hydrochloric acid in hot conditions. Lead chloride precipitates by cooling. Lead chloride so leached is converted into carbonate by leaching with sodium carbonate solution. Copper, lead and tin metals are recovered from the leach products by thermal reduction. Pyrometallurgical treatment involves melting with a carbon/alkali borate flux at 1150–1300°C for controlling slag quantity. Parameters affecting the recovery efficiency of the investigated methods, such as time, temperature, hydrogen peroxide concentration, and stoichiometric ratio of the leachants are given. Results obtained show that melting of bronze turnings failed to recover standard bronze alloys due to thermal volatilization of tin and escape of lead into the slag. Combined hydrometallurgical processes are significant for recovering metals as well as bronze alloys from the turnings. Hydrogen peroxide assists dissolution of the metals originally present in the scrap. Metals entering the slag are recycled in the same manner. Free metals are recovered from the leached products by thermal reduction with hydrogen or spent active carbon. The activation energy of the latter process amounts to 83.6, 12.7 and 51.73 kJ/mol for copper, lead and tin respectively. The maximum recovery efficiency of the suggested method amounts to 98.7%. A preliminary economic evaluation suggests that the process could be economically feasible.

Advanced lubricants for heat engines

AbstractAn advanced liquid lubricant for heat engines has been developed and tested successfully in a prototype engine. The lubricant possesses superior oxidation stability and high temperature stability. With the advent of new engine designs, stability should be measured in terms of both the temperature and the time for which the lubricant is subjected to it. This lubricant is designed to provide friction and wear protection for three to five minutes at 425°C (800°F) at the ring zone and maintains stability at an oil sump temperature of 171°C. The lubricant has been evaluated by the Cummins Engine Company. Out of a field of several dozen lubricants, six lubricants were selected for a prototype 200 h endurance tests. The NIST lubricant was one of the two lubricants that successfully finished the endurance testing. This paper provides an overview of the key lubricant design considerations, including oxidation and thermal stability, volatility, and deposit control, the prototype engine test conditions and the results.

Resorcinol bis(diphenyl phosphate), a non‐halogen flame‐retardant additive

AbstractThis paper is a review of Resorcinol bis(diphenyl phosphate) (RDP), a non‐halogen aromatic oligomeric phosphate flame‐retardant and flow modifier. Its high thermal stability and low volatility, compared with the triaryl phosphates, make it ideal for use in applications where high processing temperatures are requuired. Thermogravimetric data showing the effects of RDP on modified PPO and polycarbonate/ABS blends are presented. Current and potential end uses in thermoplastic resins and polyurethanes are discussed.

Thermal degradation studies of alternating copolymers: IV. The alternating copolymer of acenaphthylene and maleic anhydride

The thermal stability of an acenaphthylene and maleic anhydride (ACN-MAn) copolymer has been investigated in inert atmosphere using thermogravimetry-differential thermogravimetry (TG-DTG) and under vacuum by thermal volatilisation analysis (TVA). ACN-MAn copolymer has also been examined in air using TG-DTG. The condensable volatile degradation products from TVA experiments were separated by subambient TVA (SATVA) and investigated by FTIR spectroscopy, mass spectrometry (MS) and GC-MS techniques. The cold ring fraction was investigated by FTIR spectroscopy and GC. The degradation products from ACN-MAn copolymer were mainly similar to those from PACN i.e. acenaphthylene and acenaphthene, while other new products were also present. Mechanisms of formation of the degradation products have been discussed in detail. ACN-MAn copolymer shows greater stability in air, and is less stable than PACN both in air and an inert atmosphere. Controlled isothermal heating introduces conjugation into the copolymer chain.

Thermal degradation mechanisms of some addition polymers and copolymers

Basic degradation patterns of depolymerisation and side group reaction for addition homopolymer, are first outlined and some of the additional types of behaviour found in the case of random copolymers are illustrated. The latter include instances of direct interaction between adjacent dissimilar units. The effects of blending of two polymers on degradation behaviour are briefly considered. When interactions occur in the degradation of polyblends, which are normally heterogeneous, these fall into two distinct types, involving migration of small species, either radicals or molecules, across the phase boundary from one polymer into the other. Taking as a common theme the vinyl acetate (VA) monomer unit, the thermal degradation behaviour of PVA homopolymer, several VA random copolymers and some PVA polyblends are then examined, on the basis of research studies using TG and thermal volatilisation analysis (TVA). The latter approach allows further investigation of all of the degradation product fractions, from non-condensable gases to involatile residue, so enabling these to be well characterised and providing a basis for proposing degradation mechanisms. Finally, some recent work on alternating copolymers based on VA is presented to show some of the novel and interesting features of the breakdown of these structurally regular copolymers.

Thermal degradation of iron polymethacrylate

Iron polymethacrylate was synthesized by free radical solution polymerization of methacrylic acid, followed by replacement of the carboxylic proton with iron. Thermal volatilization analysis and thermogravimetry were used to study its thermal stability from ambient temperature up to 500oC. The results reveal that ferric oxide is left as residue at the end of the thermal degradation experiments.

THERMAL DEGRADATION STUDY OF SILOXANE-DGEBA EPOXY COPOLYMERS

Siloxane-modified DGEBA epoxy (ESDG) copolymers were prepared from Epikote 1001 and siloxane oligomers. Thermal stability studied by TGA of these ESDG copolymers indicates that thermal degradation is being effected by either structure or content of the siloxane moiety in the copolymers. The study reveals that siloxane-modified epoxy copolymer with phenyl-enriched siloxane oligomer (ESDG-7430) provides higher thermal stability than dimethyl siloxane modified copolymer (ESDG-8430). Delaying thermal degradation by the siloxane segment of ESDG copolymers is observed and the increase in thermal stability of copolymer is also observed consistently, with the increase of the siloxane content. These results indicate that the cause of the delaying degradation may be due to the siloxane segment being stable at the epoxy degradation temperature and the heat irradiated on the copolymer being absorbed by the siloxane segment which may dissipate that portion of thermal energy efficiently through its flexible siloxane structure. The delaying degradation behaviour is also confirmed by a direct pyrolysis/mass spectrometry (DP/MS) study, by the observation of the formation and contents (TIC and SIC) of the thermal degradative volatiles (TDVs). Nonflammability of ESDG copolymers as indicated by the LOI values is increased consistently with the increase in siloxane content in the copolymers. IR analysis and SEM/EDX observations on the char residue are also carried out.

Catalytic combustion gas turbine systems: the preferred technology for low emissions electric power production and co-generation

The operating requirements for practical catalytic combustion systems are presented. Catalytic materials for methane combustion are then reviewed in light of these operating requirements. Measured catalytic rates for methane oxidization for a number of active metal and oxide catalyst systems are reported and compared. The precious metals, particularly Pd, are most active. The oxides can exhibit high surface areas but in all cases have a much lower areal activity resulting in a substantially lower weight specific activity. Data on the thermal stability and volatility of both support and active components are presented and discussed in terms of the required operating temperatures. It is concluded that at the required operating temperature for modern gas turbines, most catalyst systems would not have sufficient stability and life. An alternative approach is to limit the catalyst temperature and to react a portion of the fuel after the catalyst. This process has substantial advantages. This latter system will be described and the important catalyst performance characteristics discussed. Test results demonstrate NO x levels below 2 ppm even at combustor outlet temperatures as high as 1500°C.

Thermal degradation of allyl methacrylate—methyl methacrylate copolymers

The thermal degradation of copolymers of allyl methacrylate (AMA) and methyl methacrylate (MMA) was studied by thermal volatilisation analysis (TVA), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The main pyrolysis products have been identified and mechanisms are proposed to account for their production.

Thermal degradation of poly(tertbutyl aziridine)-poly(methyl methacrylate) graft copolymer

The degradation behaviour of a high molecular weight PMMA sample in which approximately 2% of the MMA units have been modified and grafted with PTBA chains of molecular weight 5000, to give a product containing about 50% by weight of PTBA, has been investigated. The techniques used were the same as in recently reported investigations of PTBA, PTBA-PMMA block copolymer and poly( N-methyl- N-tertbutyl-aminoethyl methacrylate) (PMTBAEM), and included TG, DTA and thermal volatilisation analysis (TVA). Products from the TVA experiments were separated and characterised. The graft copolymer is less stable than PMMA and comparable in stability to PTBA. It appears that the grafted side chains degrade primarily to PTBA-related oligomeric material, accompanied by a small proportion of volatile products also derived from the PTBA chains, whereas the main backbone gives predominantly MMA monomer.

Fire‐retardant action of potassium nitrate in polyamide 6

AbstractThe addition of 10–20 wt.‐% of potassium nitrate (KNO3) to polyamide 6 (PA 6) improves the fire retardance of the polymer. The thermal decomposition behaviour of the PA 6/KN03‐mixture was studied using thermogravimetry, differential scanning calorimetry and thermal volatilisation analysis. Solid products of the thermal decomposition of the mixture were analysed by infrared spectroscopy, X‐ray diffraction and electron paramagnetic resonance. It was found that KNO, prevents flowing and dripping of the melt and promotes charring on the surface of the polymer which decreases its fire hazard and improves its fire retardance. On the other hand, KNO3 exothermally reacts with PA 6 in the condensed phase and supplies oxygen to the gas phase which increases the combustibility of PA 6. The mechanism of the chemical interaction of KN03 with PA 6 is discussed.

Thermal degradation of poly- N-methyl- N-tertbutyl-aminoethyl methacrylate

The thermal degradation behaviour of poly- N-methyl- N-tertbutyl-aminoethyl methacrylate (PMTBAEM) has been studied using thermogravimetry, differential thermal analysis and thermal volatilisation analysis, with programmed heating at 10 °C/min. Subambient TVA was used to separate the volatile degradation products, which were characterised by mass spectrometry and IR spectroscopy. The main volatile products were found to be isobutene and carbon dioxide. The less volatile liquid components of this product fraction were further separated by gas chromatography and identified by mass spectrometry: the main liquid product was tertbutylaziridine, while methanol and traces of methyl-tertbutyl-aminoethyl methacrylate (MTBAEM) were also identified. The cold ring (tar/wax) fraction products, which formed the largest product fraction, were examined by IR spectroscopy and found to consist of modified oligomers of MTBAEM. It is concluded that the degradation mechanism involves two distinct types of side group decomposition together with fragmentation, mainly at higher temperatures, of the modified chains.

Thermal degradation of poly [2-(3-chloro-3-methylcyclobutyl)-2-hydroxyethyl methacrylate

The thermal degradation of poly[2-(3-chloro-3-methylcyclobutyl)-2-hydroxyethyl methacrylate] [poly(CBHEMA)] has been studied by using thermal volatilisation analysis (TVA) and thermogravimetry (TG). Programmed heating was carried out at 10 °C min −1 from room temperature to 500 °C. Volatile products were separated by subambient TVA and identified by gasphase IR and MS, and GC-MS for volatile liquids. The cold ring fraction and partially degraded polymer have been examined by IR spectroscopy. The monomer was not formed during the degradation since HCl elimination from the chain began at about 150 °C, which is a low temperature for the production of monomer. However, some monomer homologues from the HCl-eliminated polymer were dedected as minor products. The polymer yields carbon monoxide, methane and oxygen as non-condensable products at − 196 °C. Carbon dioxide, hydrogen chloride, water and some unsaturated and saturated hydrocarbons were found in the volatile products. The liquid products of the degradation, the formation of anhydride ring structures and the mechanism of degradation are discussed.

Thermal degradation behaviour of poly(acenaphthylene)

The thermal stability of poly(acenaphthylene) (PACN) has been investigated in inert atmosphere and air using thermogravimetry-differential thermogravimetry (TG-DTG), and under continuous evacuation by thermal volatilization analysis (TVA). The condensable volatile degradation products from TVA experiments were separated by subambient TVA (SATVA) and investigated mainly by mass spectrometry (MS) and GC-MS techniques. The cold ring fraction (CRF) was investigated by IR spectroscopy MS and GC-MS. The degradation products from PACN were mainly acenaphthylene (major), acenaphthene and various oligomers, appearing as CRF: volatile degradation products amounted to only a little more than 1% and a similar amount of residue was formed. Mechanisms of formation of the degradation products have been discussed in detail. PACN shows more stability in air than in the inert atmosphere. The polymer was also pyrolysed at various temperatures under different environmental conditions and structural properties of the resulting polymers were investigated by IR spectroscopy.