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Cellulose, lignin, raw bagasse fiber, and extracted bagasse fibers chemically processed with different concentrations of sodium hydroxide solution and treatment time were measured by thermogravimetry analysis (TGA). The thermal characteristics of these fibers were determined by thermogravimetry (TG) and derivative thermogravimetry (DTG) profiles and analyzed based on the onset degradation temperature, peak rate of thermal decomposition, and residual weight. According to the observations from the experimental data from TGA and DTG profiles and literature reports, it was found that higher content of cellulose and lower content of lignin would result in higher onset degradation temperature, higher peak rate of decomposition, and lower residual weight. Statistical analysis of the onset decomposition temperatures, peak rate of weight loss, and residual weights of different extracted bagasse fibers showed that most of their values were significantly different. The three‐dimensional surface plots of onset decomp...

An increasing industrial interest is applications of kenaf and ramie fiber nonwovens for making automotive interior trim parts because of their excellent strength and renewability. This paper presents a study on the manufacture and evaluation of the kenaf/ramie nonwoven composite for this automotive end use. Carding, needle-punching, and wet bonding were used to fabricate the composite. End-use performance of the composite, in terms of tensile strength, thermal conductivity, dynamic mechanical property, and bonding structure, was tested using a series of instruments in accordance with the ASTM methods. Bonding performance of the polyvinyl alcohol binder and acrylic copolymer binder was also compared. Research results revealed that the acrylic-copolymer bonded composite was significantly anisotropic in both tensile and bending deformation and the polyvinyl-alcohol bonded composite was significantly anisotropic only in bending deformation. For the acrylic-copolymer bonded composite, increase of padding times helped enhance tensile properties. The acrylic-copolymer bonded composite also exhibited a better performance in dynamic thermal mechanical deformation but indicated insignificant difference of thermal conductivity compared to the polyvinyl-alcohol bonded composite.

Chemical coupling of maleated polyethylene (MAPE) copolymers at the interface in wood-fiber/high-density-polyethylene (HDPE) composites was investigated in this study. FTIR and ESCA analyses presented the evidence of a chemical bridge between the wood fiber and polymeric matrix through esterification. The feature peak of esterification occurred in the range between 1800 and 1650 cm−1 at FTIR spectra. Succinic and half succinic esters were the two primary covalent bonding products to cross-link the wood fiber and thermoplastic matrix. Maleated composites had a remarkable shift on most O1s and C1s spectra in respect to the wood, HDPE, and untreated composites. The binding energy of maleated composites at C1s and O1s spectra was around 282 eV and 530 eV, respectively. The mass concentration of chemical components at the interface was related to the coupling agent type, structure, and concentration. According to the FTIR and ESCA analyses, the coupling mechanisms of MAPEs were proposed. The interfacial morpho...

The coupling efficiency of seven coupling agents in wood-polymer composites (WPC) was investi- gated in this study. The improvement on the interfacial bonding strength, flexural modulus, and other mechanical properties of the resultant wood fiber/high-density polyeth- ylene (HDPE) composites was mainly related to the cou- pling agent type, function groups, molecular weight, con- centration, and chain structure. As a coupling agent, mal- eated polyethylene (MAPE) had a better performance in WPC than oxidized polyethylene (OPE) and pure polyeth- ylene (PPE) because of its stronger interfacial bonding. A combination of the acid number, molecular weight, and concentration of coupling agents had a significant effect on the interfacial bonding in WPC. The coupling agents with a high molecular weight, moderate acid number, and low concentration level were preferred to improve interfacial adhesion in WPC. The backbone structure of coupling agents also affected the interfacial bonding strength. Com- pared with the untreated composites, modified composites improved the interfacial bonding strength by 140% on max- imum and the flexural storage modulus by 29%. According to the statistical analysis, 226D and 100D were the best of the seven coupling agents. The coupling agent performance was illustrated with the brush, switch, and amorphous struc- tures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 93-102, 2005

The thermal degradation (weight loss) of individual FA and of catfish and menhaden oils collected from different refining steps was investigated by thermogravimetric analysis. The heat resistance of FA was partially dependent on chain length and degree of unsaturation. The weight loss of catfish and menhaden oils increased with increased heating temperatures, regardless of the oil refining process. All oil samples (except crude catfish oil) were decomposed after the heating temperature reached 550°C. Based on the thermogravimetric curves, the following thermal stability sequence at different refining steps for both catfish and menhaden oils was proposed: crude > degummed > neutralized > bleached > deodorized oils.

Effects of oil refining steps (degumming, neutralizing, bleaching, and deodorizing) on rheological properties of catfish oil were investigated. Four rheological models (Newtonian, Bingham, Herschel-Bulkley, and Casson) were used to fit the experimental data. Refined catfish oil behaves like a Newtonian fluid. Based on the Casson model, the yield stress values of oils gradually decreased after each refining step. The highest shear rate index (0.904) was observed in the deodorized oil. The Casson model was used to predict rheological properties because it works well at both lower and higher shear rates.

Macromolecular complexes of styrene sulfonate copolymers, poly(vinyl phenol-co-styrene sulfonate) (PKS) and poly(styrene-co-styrene sulfonate) (PS-co-SSS) with poly(ethylene oxide) (PEO) in aqueous solution were studied by NMR. The shift to lower frequency of the 1H chemical shift for the PEO ethylene group and the existence of strong nuclear Overhauser effect cross-peaks between the aromatic rings of PKS and the ethylene proton of PEO indicated that aromatic rings interacted with the PEO ethylene groups. Since the spectra of PS-co-SSS/PEO mixtures revealed complexes with structures similar to those formed with the phenolic copolymers, it was concluded that hydrogen bonding was not necessary for complex formation.

The dynamic curing process was studied by using differential scanning calorimetry (DSC) and modeled by two methods. One was based on the Kissinger and Ozawa approach, in which the activation energy was taken as a constant for all the heating rates. The whole curing process was modeled with two cure reactions. Reaction 1 exhibited the behavior of the autocatalytic reaction, whereas Reaction 2 was the nth order reaction. The effect of heating rate on the preexponential factor A1 of Reaction 1 was apparent. As the heating rate increased, the A1 decreased. There was no significant effect of heating rate on the preexponential factor A2 of Reaction 2 and the reaction orders for both reactions. The calculated results showed that the contributions of these two reactions to the total curing process were very different and changed with the heating rate. Except in the early cure stage, the calculated total degree of cure agreed well with the experimental data. Another method was based on the Borchardt and Daniels kinetic approach, where the activation energy of the cure reaction at each heating rate was determined separately. The whole curing process was modeled with one autocatalytic reaction. The fitting results showed that both preexponential factor and activation energy increased with the increment of the heating rate. As in the first method, the effect of heating rate on the orders of reaction was very small. The calculated results agreed well with experimental values in the early cure stage. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1911–1923, 2002

The tribological behavior of polytetrafluroethylene (PTFE) and PTFE composites with filler materials such as carbon, graphite, E glass fibers, MoS 2 and poly-p-phenyleneterephthalamide (PPDT) fibers, was studied. The present filler additions found to increase hardness and wear resistance in all composites studied. The highest wear resistance was found for composites containing (i) 18% carbon + 7% graphite, (ii) 20% glass fibers + 5% MoS2 and (iii) 10% PPDT fibers. Scanning electron microscopy (SEM) was utilized to examine composite microstructures and study modes of failure. Wear testing and SEM analysis showed that three-body abrasion was probably the dominant mode of failure for PTFE + 18% carbon + 7% graphite composite, while fiber pull out and fragmentation caused failure of PTFE + 20% glass fiber + 5% MoS2 composite. The composite with 10% PPDT fibers caused wear reduction due to the ability of the fibers to remain embedded in the matrix and preferentially support the load. Differential scanning calorimetry (DSC) analysis was also performed to study the relative heat absorbing capacity and thermal stability of the various composites in an effort to correlate these properties to the tribological performance. The results indicated that composites with higher heat absorption capacity exhibited improved wear resistance. The dominant interactive wear mechanisms during sliding of PTFE and its composites are discussed in view of the present findings. © 2002 Published by Elsevier Science B.V.

The curing process of epoxy prepreg was studied by means of differential scanning calorimetry analysis. The dynamic, isothermal, and combinations of dynamic and isothermal measurements were done over selected temperature ranges and isothermal cure temperatures. The heats of reaction for dynamic and isothermal cure were determined. The results show that the heat of the isothermal-cure reaction increased with the increment of temperature. The degree of cure was calculated from the heat of the isothermal-cure reaction. The complete cure reaction could be achieved at 220°C within a very short cure time. The changes of cure rate with time were given for the studied isothermal cure temperatures. To simulate the relationship between the cure rate and degree of cure, the autocatalytic model was used and the four parameters were calculated. Except in the late stage of the cure reaction, the model agrees well with the experimental data, especially at high temperatures. To account for the effect of diffusion on the cure rate, a diffusion factor was introduced into the model. The modified model greatly improved the predicted data at the late stage of cure reaction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1074–1083, 2002

Thermoreversible gelation of rodlike poly(A-stearyl-R-L-glutamate) in n-dodecane has been studied by differential scanning calorimetry, polarized light microscopy, visual observations, and temperature ramped fluorescence photobleaching recovery. Solutions spanning a wide range of concentra- tions can produce gels. In solutions that are initially liquid crystalline, long-range features such as cholesteric twist appear to be frozen by gelation. Although gelation is rapid, some of the polymer molecules retain significant mobility, allowing the gels to "cure" slowly.

Polyester (PET) swatches are treated with an electrical discharge plasma of a reactive atmosphere (tetrachlorosilane) to graft chlorosilane groups, subsequently hydrolyzed to very hydrophilic hydroxysilane groups. The Kawabata evaluation system for fabrics (KES-FB), high resolution microscopy, and surface tension measurements are used to investigate the physical properties of the fabrics before and after plasma exposure. The results show that the surface parameters are considerably modified by the treatment.

Preparation and shear and elongational rheology of cellulose solutions of different degrees of polymerization (DP) in N-methylmorpholine oxide monohydrate (lyocell) were investigated. The dissolution process takes place in two stages, depending on the content of low and high DP fractions from the dissolving pulp blends. The influence of the DP of cellulosic chains on elongational and shear viscosity is greater at low deformation rates. Low DP solutions behave more like viscous fluids and the increase of the chain length brings about an increase of the elastic component. Orientation induced by the convergence flow is enhanced by the higher DP cellulosic chains. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 396–405, 2001

Several quaternary ammonium salts, based on ethanolamine and diethanolamine, bearing C10 and C12 alkyl chains were synthesized comparatively with the corresponding amides. Smectic-type liquid crystal properties were observed only for the quaternary ammonium salts with either one or two C12 alkyl groups.

We have compared the interactions between Polyquaternium 10 and sodium dodecyl sulfate (SDS) with similar complexes of mono and diquaternary aminoalkylcarbamoyl cellulose derivatives by measuring the surface tension of their aqueous solutions. The results indicate that reduction of surface tension of aqueous solutions occurs via the formation of highly surface active polymer-surfactant complexes. At approximately a 1: 1 stoichiometric ratio of SDS to quaternary groups, a complex of low solubility forms which is more efficient at reducing surface tension than the surfactant alone. The ability of the polymer-surfactant complex to reduce surface tension appears to be independent of polymer architecture and dependent only upon adsorption of the surfactant species at the cationic polymer sites.

Blends with up to 20 percent ground vulcanized rubber (both crumb and 200-mesh powder particles) from recycled tires were prepared with asphalt cements of various grades (AC-5 to AC-30) and evaluated using dynamic mechanical analysis (DMA). Blends produced from powdered rubber particles exhibited Newtonian behavior at high temperatures. Similar behavior was not observed with crumb rubber blends. The mechanical properties of asphalt-rubber blends depend on the concentration of rubber additives, the particle sizes, and the chemical composition of the asphalt. The dynamic mechanical characteristics of all blends are discussed in terms of G*sin δ and G″ comparative data are presented according to the Strategic Highway Research Program binder specifications. Pressure aging vessel (PAV) tests of the asphalt-rubber blends revealed a significant difference between crumb rubber and powdered rubber additives. Simple blends of crumb rubber with asphalts ranging in grade from AC-5 to AC-30 exhibited phase separation during a thin-film oven aging test. In contrast, blends with powdered rubber appeared to remain compatible or at least partially compatible through the PAV process, and the blends retained the physical properties associated with the additive. The DMA data suggest that the low-temperature cracking resistance of asphalt–powdered rubber blends is enhanced.

The synthesis of a variety of substituted bisphenol A polysulfones, including nitro, amino, aminomethyl, ethyl, and methyl derivatives, is described. Nuclear magnetic resonance (NMR) (both proton and carbon, and several 2-D experiments) data confirm conclusions on the substitution site based on arguments on inductive effects in the phenyl rings. The proton ortho to the oxygen in the bisphenol A (BPA) residue is replaced in electrophilic substitution reactions. The degree of substitution was also calculated from the NMR results. The ethyl and methyl derivatives were expected, from the starting reactants, to each have a BPA ring substituted. The NMR data showed that, on the average, this is true. The nitro derivative also has substitution in every BPA ring, while the amino and aminomethyl derivatives have only intermittent BPA rings substituted. Measured degrees of substitution (DS) varied from 0.11 to 2.25.

The gas permeability, diffusivity, and solubility of a series of polysulfones bearing basic aryl substituents were determined at 35 °C and pressures up to 20 atm. Gas permeability and diffusivity values of the aryl-substituted polysulfones were markedly lower than those of unmodified polysulfone. These effects were ascribed to decreased fractional free volume and increased restriction to sub-Tg torsional motion in the substituted polymers. Polysulfone bearing benzylic amine substituents exhibited higher CO2 solubility and CO2/CH4 solubility selectivity than polysulfone, presumably due to favorable interactions between acidic CO2 molecules and basic −CH2-NH2 groups. CO2 diffusivity in polysulfone bearing benzylic amine substituents is lower than expected based on free volume considerations, suggesting that interactions between CO2 and benzylic amine moieties may be strong enough to impede CO2 mobility in the modified polymer. These results are consistent with infrared spectroscopy data which suggest that t...

A series of aromatic polyesters and aromatic poly(ester-amide)s have been synthesized by polycondensation of diacid chlorides containing preformed ester groups with 9,9-bis(p-hydroxyphenyl)fluorene or 9,9-bis(p-aminophenyl)fluorene, respectively. These polymers are easily soluble in polar aprotic solvents, and the polyesters are even soluble in chloroform; their solutions were cast into transparent, thin, flexible films. The polyesters are stable up to 324–335°C, while poly(esteramide)s are stable up to 401–409°C. The dielectric constant of these polymers is in the 3.2 to 4.15 range, being lower for polyesters. All these characteristics are discussed and compared with those of related polymers without fluorene units.

The self-diffusion coefficient, D s , of fluorescently tagged poly(γ-benzyl α,L-glutamate) has been measured throughout the isotropic regime in pyridine. Intrinsic viscosity, phase boundary studies, epifluorescence microscopy, computer modeling, and the diffusion rates themselves show that the labeling does not appreciably perturb the semiflexible rod structure of the polymer. It is also demonstrated that pyridine is a good solvent for poly(γ-benzyl α,L-glutamate), comparable to N,N'-dimethylformamide. As concentration increases, two or three regimes are found depending on the rod length. Dilute behavior holds to number densities, ν, well exceeding L -3 , where L is the rod length

We have studied ternary solutions of rodlike and random coil polymers in a common solvent. In these solutions, the rods scatter weakly, and almost all scattering comes from the coil component. From light scattering measurements, we gained information about the thermodynamic and hydrodynamic properties of the coil in rodlike polymer solutions.

The thermodynamics and mobility of a random-coil polymer were studied by light scattering in toluene solutions containing a rodlike polymer. The random-coil polymer was polystyrene (PS). The rodlike polymer was helical poly([gamma]-stearyl [alpha],L-glutamate), or PSLG, which aggregates end-to-end in toluene to produce long filaments. As PSLG is almost isorefractive with toluene, the scattering of PS can be measured in PSLG/toluene mixtures with almost no interference from PSLG. The apparent second virial coefficient of the PS component decreases rapidly with addition of the invisible rodlike polymer component, while the PS radius of gyration does not. The reduction of the virial coefficient, but not the size, of the random-coil polymer in the presence of PSLG is due to the occupation of connected (and linearly correlated) space. Parallel effects were observed in the mutual diffusion coefficient of the coil component, which increased with PS concentration at low rod content but did the opposite when enough PSLG was added. Extrapolated to zero PS content, the mutual diffusion coefficient is expected to approach closely the self-diffusion of trace quantities of PS in the PSLG/toluene solution. So obtained, the self-diffusion coefficient decreased with added rodlike PSLG, but not as fast as the viscosity increased; thus, themore » Stokes-Einstein relationship was not obeyed by PS probes in PSLG/toluene solutions. Scaling arguments are presented for the dependence of the size of a random coil in the presence of rods and for the crossover from Stokes-Einstein diffusion of the coil to a reptative type of motion. The available data are not well suited to test these relationships, due to limitations in the matrix concentration imposed by polymer incompatibility.« less

New thermostable polymers containing imide and phenylquinoxaline units have been prepared by solution polycondensation of diaminophenylquinoxaline coupled by ether, methylene, or sulfone linkages with diacid chlorides containing preformed imide rings. Solubility, thermal stability, and electroinsulating properties of these compounds are discussed and compared with those of related heterocyclic polymers previously reported.

Rayon/nylon skin/core composite fibers with enhanced adhesion were produced using a wire coating process. After spin finish removal by water washing, the nylon core fibers were pretreated with fumaric acid ( FA ) as an adhesion promoter and then coated with viscose rayon. Fourier transform infrared spectroscopy was used to identify the chemical bonds formed between FA and both rayon and nylon. The results indicate that carboxyl groups of FA reacted with amine end groups of nylon, forming amide bonds. Other carboxyl ends of FA reacted with hydroxyl groups of rayon, forming ester bonds. Due to the formation of these bonds, the interfacial adhesion in the composite fibers significantly improved under specific sets of application conditions.

This paper presents a new synthetic polycarboxylic compound, i.e. a benzocaine-modified maleic anhydride-cyclohexyl-1,3-dioxepin copolymer. p-Aminobenzoic acid is linked via an anaesthesine (p-aminoethylbenzoate, benzocaine) to the carboxylic groups of the copolymer, both as a spacer and to increase the hydrophobicity of the polymer through the phenyl group. The structure of the modified copolymer is characterized by thin-layer chromatography and by i.r. and n.m.r. spectroscopy.

The aim of this contribution is to determine the relationship existent between the chemistry and/or viscosity of some biodegradable polymer solutions and the morphology of micro- and nanospheres resulted after spray drying the solutions at room conditions either in the presence or in the absence of an encapsulated aqueous material. Using dichloromethane as solvent, the following polyesters were used to prepare 2 wt% solutions: polyhydroxybutyrate (PHB), polylactic acid (PLA), poly(lactic- co-glycolic acid) (PLGA) and Eastar Bio GP (GP). A comprehensive thermal characterization was also performed on all polymers to verify the relationships existent between the structure of polyesters and certain important parameters, such as Tg, T m, Td. It was observed that a decrease in the solution viscosity triggers the formation of smoother microspheres. When the viscosity becomes low enough the sprayed solution can lead to the development of well defined nanospheres instead of microspheres. Additionally, it was found that in the presence of an aqueous core the micro- and/or nanocapsules coalesce into larger micrometric aggregates, due to the plasticizing effects of water on the polyester.

Professor Cristofor I. Simionescu was born on July 17, 1920, in Dumbraveni-Suceava. His father was a high school teacher, and young Simionescu went to elementary school in his home town. After completing elementary school he went to Jassy and attended the prestigious “National Lyceum,” the roots of which stem from the “Michailean Academy.” He then began studies at the Polytechnic Institute of Jassy at the Faculty of Chemical Engineering. As a young student he was known for his enthusiasm and was recognized as an excellent young scientist. In 1944 Cristofor Simionescu graduated mugna cum lade from the Polytechnic Institute in Jassy. He obtained his first scientific degree in organic technology, i.e., Doctor of Technical Sciences, in 1948, and became Associate Professor at the Polytechnic Institute. In 1951 he was promoted to Full Professor and was appointed to the Chair of Natural and Synthetic Macromolecules. From 1953 until 1976 Professor Simionescu was Rector of the Polytechnic Institute of Jassy.

The anaerobic biodegradability of Polyhydroxybutyrate (PHB) was investigated to determine degradation kinetics and the effects of degradation on characteristics of the plastic. PHB was melt-pressed into plates of thicknesses 0.24, 0.5, 1.2, 3.5 and 5.0 mm. Three experiments, which assessed biodegradability based on evolved gaseous carbon, were performed according to ASTM D 5210. In addition, two mass loss studies were performed to facilitate the determination of degradation kinetics. Melt-pressed plates of the PHB were extracted from the degrading medium and weighed at appropriate time intervals for determining the degradation kinetics. In the mass-loss experiments, melt-pressed plates of the bioplastic with five different initial mass-to-surface-area ratios were investigated for the purpose of establishing a relationship between this parameter and decay rate coefficients for first order decay kinetics. It was found that the degradation rate coefficient of the PHB is dependent upon the initial mass-to-surface-area ratio of the bioplastic seemingly according to saturation kinetics. In the first anaerobic mass loss experiment, the degradation rate coefficients with respect to initial surface area of the 0.5-mm, 1.2-mm, and 3.5-mm PHA plates were 0.5846, 1.2920, and 2.0656 mg cm-2 d-1, respectively; in the second anaerobic mass loss experiment, the degradation rate coefficients with respect to initial surface area of the 0.24-mm, 1.2-mm, and 3.5-mm PHA plates were 0.3191, 0.7308, and 0.9484 mg cm-2 d-1, respectively. This data also demonstrated that the particular sewage sludge medium used to degrade the PHB has a significant impact on the degradation kinetics. Furthermore, the effects of biodegradation on certain characteristics of the bioplastic as determined by analyses such as DSC, FT-IR, and Size Exclusion Chromatography were tested.

Functional, nutritional, and thermal properties of freeze-dried protein powders (FPP) from whole herring (WHP), herring body (HBP), herring head (HHP), herring gonad (HGP), and arrowtooth flounder fillets (AFP) were evaluated. The FPP samples have desirable nutritional and functional properties and contained 63-81.4% protein. All FPP samples had desirable essential amino acid profiles and mineral contents. The emulsifying and fat adsorption capacities of all FPP samples were higher than those of soy protein concentrate. The emulsifying stability of WHP was lower than that of egg albumin but greater than that of soy protein concentrate. Thermal stability of the FPP samples is in the following order: HGP > HBP > WHP > HHP > AFP.

Polyethylene, a recyclable waste which is abundantly available either as virgin off specification material or from solid waste classification processes, was slightly chlorinated to improve its compatibility with asphalt. High density polyethylene, HDPE, and chlorinated polyethylene (CPE) modified asphalts were evaluated using dynamic mechanic analysis (DMA), DSC, and epifluorescence microscopy. The results confirm that CPE’s with low chlorine contents (

Different coalescence processes on 1D silver nanostructures synthesized by a PVP assisted reaction in ethylene glycol at 160 °C were studied experimentally and theoretically. Analysis by TEM and HRTEM shows different defects found on the body of these materials, suggesting that they were induced by previous coalescence processes in the synthesis stage. TEM observations showed that irradiation with the electron beam eliminates the boundaries formed near the edges of the structures, suggesting that this process can be carried out by the application of other means of energy (i.e. thermal). These results were also confirmed by theoretical calculations by Monte Carlo simulations using a Sutton-Chen potential. A theoretical study by molecular dynamics simulation of the different coalescence processes on 1D silver nanostructures is presented, showing a surface energy driven sequence followed to form the final coalesced structure. Calculations were made at 1000-1300 K, which is near the melting temperature of silver (1234 K). Based on these results, it is proposed that 1D nanostructures can grow through a secondary mechanism based on coalescence, without losing their dimensionality.

Cationic morpholine lipids 1 and 6 undergo complex phase transition patterns and exhibit metastable phases; lipids 1,2 and 6 become thermotropic liquid crystals through the first phase transition temperatures, whereas 5 and 7 lose birefringence and become opaque solids.

Natural and synthetic fibres and fabrics have been modified in cold plasma conditions in order to impart new qualities to support materials. Both static and dynamic installations designed to this aim are presented. Improved hydrophilicity, dyeability and flamme retardancy properties were achieved by grafting with either monomeric or polymeric substances.

The thermo-oxidative degradation ofPET was investigated. Using turbidimetric titration the distribution of molecular mass at different degradation steps was determined. Chemical and molecular transformations of the polymers during degradation were also analyzed. It is shown that vinylic end groups are involved in radical reactions and determine the increase of the molecular mass.

The thermal degradation of saturated and unsaturated poly(a-cyano-acrylate)s, i.e., poly(methyl α-cyanoacrylate) (PMCA), poly(ethyl α-cyanoacrylate) (PECA), poly(w-propyl α-cyanoacrylate) (PPCA), and poly(allyl α-cyanoacrylate) (PACA) has been investigated both in air and nitrogen. The thermal stability of poly(alkyl α-cyanoacrylate) decreases in the order PPCA > PECA > PMCA. Initially, the thermal stability of PACA is lower than that of PPCA, but at temperatures higher than 220°C the order is reversed due to crosslinking through pendant allylic bonds, which takes place up to 175°C.

The thermal degradation of certain trioxane-dioxolane copolymers obtained with boron trifluoride-acrylonitrile complex as initiator has been investigated. The thermal stability of samples, discussed in terms of topoenergetic values, was related both to copolymer composition and conversion. The most thermostable copolymers (∼5% weight loss at 300°C in air), having 5–8% dioxolane units, had the highest intrinsic viscosity in the series and were isolated at 35–50% conversion. The results obtained were compared with similar data for a commercial tri-oxane-ethylene oxide copolymer containing 95% formal units.

The thermo-oxidative degradation ofPET was investigated. Using turbidimetric titration the distribution of molecular mass at different degradation steps was determined. Chemical and molecular transformations of the polymers during degradation were also analyzed. It is shown that vinylic end groups are involved in radical reactions and determine the increase of the molecular mass.

It is shown that the isomerization of cis polyacetylene at 195°C for long periods is accompanied by structural modifications. Infra-red and pyrolysis gas-chromatography data suggest that the aromatization process occurs even at this temperature.