Pyrolysis of cyclo-aromatic diesters

Studies on the pyrolysis of cyclo-aromatic diesters derivatives of 3-phenylprop-2-en-1-ol are presented. The diesters are obtained during catalyzed esterification process of a stoichiometric ratio of 3-phenylprop-2-en-1-ol with suitable cycloaliphatic or aromatic acid anhydride in the solvent-free medium. As an acid anhydrides cyclohexane-1,2-dicarboxylic anhydride, cis-4-cyclohexene-1,2-dicarboxylic anhydride, bicyclo[2.2.1]-5-heptene-2,3-dicarboxylic anhydride, and phthalic anhydride were applied. The thermal properties of obtained compounds under inert atmosphere were tested by means of differential scanning calorimetry and thermogravimetry coupled with FTIR analysis. The pyrolysis products were determined and the probable mechanism of their decomposition was proposed.     

Poly(trimethylolpropane trimethacrylate) modified with esters derivatives of 3-phenylprop-2-en-1-ol

Journal of Thermal Analysis and Calorimetry - The main objective of this paper was to study the influence of the diesters derivatives of naturally occurring alcohol: 3-phenylprop-2-en-1-ol, on the...     

Succinic or glutaric anhydride modified linear unsaturated (epoxy) polyesters

A series of N-alkyl-N-alkyl′-pyrrolidinium-bis(trifluoromethanesulfonyl) imide (TFSI⁻) room temperature ionic liquids (RTILs) has been investigated by means of thermogravimetric analysis (TG), differential scanning calorimetry, FT-IR spectroscopy, and X-ray diffraction analysis. These compounds exhibit a thermal stability up to 548–573 K. The mass loss starting temperature, T _ml, falls in a narrow range of temperatures: 578–594 K. FT-IR spectra, performed before and after 24 h isothermal experiments at 553 and 573 K, have confirmed their great thermal stability. Below the ambient temperature, these compounds exhibit a complex behavior. N-methyl-N-propyl-pyrrolidinium-TFSI is the sole liquid which crystallizes without forming any amorphous phase even after quenching in liquid nitrogen. Its crystalline phase has a melting point, T _m, of 283 ± 1 K. When the amorphous solid is heated, the N-butyl-N-ethyl-pyrrolidinium-TFSI presents a glass transition temperature, T _g, at 186 K followed by a cold crystallization, T _cc, at 225 K, and a final T _m at 262 K. The N-butyl-N-methyl-pyrrolidinium-TFSI exhibits a T _g between 186 and 181 K, its cold crystallization leading to two different solid phases. Solid phase I has a melting point T _I,m = 252 K and phase II, T _II,m = 262 K. When the amorphous phase is obtained at a cooling rate of 10 K/min, its T _cc is 204 K, and a metastable solid phase (III) is obtained which transforms into the phase II at 226 K. However, when the sample is quenched, the amorphous phase transforms into phase II at T _cc = 217 K and phase I at 239 K. P₁₅-TFSI exhibits the most complicated pattern as, on cooling, it leads to both a crystallized phase at 237 K and an amorphous phase at 191 K. On heating, after a T _g at 186 K and a T _cc at 217 K, two solid–solid phase transitions are observed at 239 K and 270 K, the final T _m being 279 K.     

Synthesis and thermal behavior of linear neryl diesters in inert and oxidative atmosphere

The studies on the synthesis and thermal properties of linear neryl diesters were presented. The linear neryl diesters can be successfully obtained during butylstannoic catalyzed esterification process. The final conversion of nerol and carboxylic groups was higher than 95 % using a stoichiometric molar ratio of reagents in mild conditions. The high yield products were prepared after longer time than previously studied geranyl diesters. It was directly connected with the steric hindrance and lower susceptibility of nerol to esterification process than geraniol. The TG/FTIR/QMS studies proved that the thermal properties and decomposition mechanism of neryl diesters differ considerably in inert and oxidative atmosphere. The diesters were thermally stable up to 200 °C in inert atmosphere. Their decomposition was run as a one-step process. The analyses of the volatile products emitted during their pyrolysis indicated on the ester and O-neryl bonds cleavage. It resulted in the formation of monoterpene hydrocarbons, cyclic acid anhydrides, ketones, or aldehydes. However, the studied compounds were less thermally stable in air than in helium. Their decomposition happened in two steps. The first step ranges from 185–228 °C to almost 326–380 °C with mass loss above 88 %. The formation of acyclic or alicylic monoterpene hydrocarbons, cyclic acid anhydrides, ketones, alkenes, alkanes, carbon dioxide, and water was expected. It indicated on the asymmetrical distrupt of the bonds, partial oxygenation, and decarboxylation of emitted gaseous fragments. The second step of decomposition was observed in temperatures ranges from 380 to above 560 °C. In this step carbon dioxide and water were mainly emitted. It was the result of the oxidation of the residue formed during the fist step.     

The influence of tertiary aromatic amines on the BPO initiated cure of unsaturated epoxy polyesters with styrene studied by non-isothermal DSC

The influence of tertiary aromatic amines on the course of BPO initiated cure reaction of unsaturated epoxy polyesters with different styrene content has been studied by non-isothermal differential scanning calorimetry. Unsaturated epoxy polyesters prepared from cyclohex-4-ene-1,2-dicarboxylic anhydride, maleic anhydride and suitable aliphatic glycol: ethylene glycol or 1,4-butanediol or 1,6-hexanediol were dissolved in vinyl monomer (styrene) resulting in a styrene content of 20–80% by weight. The styrene solutions of polyesters were subjected to the cure reaction with suitable curing agent: benzoyl peroxide (BPO) used in various concentration (0.5–3.0 wt%) or the mixture of BPO/stoichiometric ratio of chosen tertiary aromatic amines: (N,N-dimethylbenzylamine (BDMA) or 2,4,6-tri(dimethylaminomethyl) phenol (DMP-30). The curing characteristic such as: temperature of the cure initiation (T _onset), peak maximum temperature (T _max), final cure temperature (T _end), heat generated during the cure reaction (ΔH) were evaluated. It has been found that the course of the cure reaction depended on the styrene content in prepared compositions and the initiating system used. The performed investigations confirmed that one of the applied tertiary aromatic amine: BDMA was an effective promoter for BPO decomposition process, causing a decrease in characteristic curing temperatures of unsaturated epoxy polyesters with styrene. The organic peroxide-amine interactions caused the promotion of BPO decomposition to benzoyloxy radicals at lower temperatures and thus accelerated the copolymerization process. However, DMP-30 was a very sluggish promoter for BPO decomposition, probably due to the presence of both hydroxyl group, their ortho-position to two of three amine groups and their branched structure. The redox reaction between BPO and DMP-30 probably resulted in non-radical products or radical formation which was incapable of initiating the polymerization reaction.     

Thermal analysis of polyesters containing oxirane groups

The preliminary studies of the thermal behaviour of polyester obtained in polycondensation process of cyclohex-4-ene-1,2-dicarboxylic anhydride and ethylene glycol and its new epoxidized form have been performed. The thermal characterization of initial polyester and its completely oxidized form was done by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The non-isothermal DSC was applied to determine the influence of time and the temperature on the chemical modification of initial polyester using 38-40% solution of peracetic acid. On the basis of DSC profiles it has been found that the endothermic transition, due to the degradation process of initial polyester was characteristic feature under controlled heating program. The two characteristic transitions for the new epoxidized polyester, the exothermic peak corresponded to the thermal crosslinking of epoxidized polyester (322.8–336.4°C) and the endothermic decomposition peak of the cured material (363.8–388.9°C) were observed. The peak maximum temperatures (Tmax) and the heat of cross-linking reaction (ΔH_c) for epoxypolyester prepared at 20–60°C under 1–4 h were evaluated. The Tmax1 were almost independent from epoxidation conditions, while, the values of ΔH_c were dependent from conditions of synthesis. The ΔH_c values of this process decreased when time of oxidation increased. The highest values of ΔH_c at 40°C were obtained. Additionally, TG experiments confirmed two separated degradation steps of the new epoxidized polyester indicating the ester (370–380°C) and ether (450–460°C) bond breakdown.     

Thermal studies on the starch-g-copolymers prepared from two terpene acrylate monomers under oxidative conditions

The simultaneous thermal studies (TG/DTG/DSC) coupled with the FTIR analysis of the gaseous decomposition products created under oxidative heating of starch-g-poly(neryl acrylate) and starch-g-poly(geranyl acrylate) copolymers have been presented. To these studies, the copolymers with the following grafting percents (G) were selected: starch-g-poly(neryl acrylate) copolymers: 36.6?±?0.3%, 40.3?±?0.4%, 42.8?±?0.4% and starch-g-poly(geranyl acrylate) copolymers: 28.9?±?0.2%, 32.4?±?0.6%, 35.6?±?0.4%. The performed tests proved that the thermal resistance of the copolymers was strongly dependent on their G values, despite a small difference in the G values between the samples. The slight increase (ca. 6.2–6.7%) in the G value caused the significant drop of the thermal stability of all the studied materials. The TG/DTG/DSC studies confirmed at least three-stage decomposition mechanism of the copolymers where simultaneous pyrolysis, oxidation, dehydration and decarboxylation processes took place. The TG/FTIR analyses showed the emission of various structure fragments; among them, one can mention the creation of some organic fragments such as aldehyde, acid, alkene, alkane, furan fragments, CH₄ and inorganic species (CO₂, CO, H₂O) as a result of the oxidative decomposition processes of the studied copolymers. In addition, the conducted studies demonstrated similar decomposition course and mechanism for both types of the copolymers, regardless of the monomer type used to the graft process.

     

Physical sorption and thermogravimetry as the methods used to analyze linear polymeric structure

An increased interest in polymer optical fibers can be observed in the last years. One of the main problems in the technology of these fibers is achieving good optical and thermal stability of used polymer materials. This paper presents a series of manufactured poly(methyl methacryalte) samples which quality was investigated using the physical sorption and the thermogravimetry methods. Studies were carried out to optimize the composition of the starting mixtures used to obtain proper polymer optical fibers.