Thermal decomposition products of copoly(arylene ether sulfone)s characterized by direct pyrolysis mass spectrometry

Influence of the Processing Conditions on the Mechanical Performance of Sustainable Bio-Based PLA Compounds

Cellulose/PLA-based blends (up to 77 vol./vol.% of the added fibers) for applications in extrusion-based technology were realized in an internal mixer by setting different operating conditions. In particular, both the mixing time and temperature were increased in order to simulate a recycling operation (10 or 25 min, 170 or 190 °C) and gain information on the potential reuse of the developed systems. The torque measurements during the compound’s preparation, and the compound’s mechanical tensile features, both in the static and dynamic mode, were evaluated for each investigated composition. The final results confirmed a reduction of the torque trend over time for the PLA matrix, which was attributed to a possible degradation mechanism, and confirmed by infrared spectroscopy. The mechanical behaviour of the pristine polymer changed from elastoplastic to brittle, with a significant loss in ductility going from the lower mixing temperatures up to the higher ones for the longest time. Through the addition of cellulose fibers into the composite systems, a higher stabilization of the torque in the time and an improvement in the mechanical performance were always verified compared to the neat PLA, with a maximum increase in the Young modulus (+100%) and the tensile strength (+57%), and a partial recovery of the ductility.

Synthesis and Characterization of Copoly(Ether Sulfone)s with Different Percentages of Diphenolic Acid Units

New functionalized Poly(ether sulfone)s having different molar ratio (10, 20, 30, 50, 70, 100 mol%) of 4,4-bis phenoxy pentanoic acid unit (diphenolic acid; DPA) units were synthesized and characterized by (1H and 13C)-NMR, MALDI-TOF MS, FT-IR, DSC and DMA analyses. The microstructural analysis of the copolymers, obtained by 13C-NMR using an appropriate statistical model, shows a random distribution of copolymer sequences, as expected. The presence of different amount of DPA units along the polymer chains affects the chemical and physical properties of the copolymers. The Tg and the contact angle values decrease as the molar fraction of DPA units increases, whereas the hydrophilicity increases. NMR and MALDI-TOF MS analyses show that all polymer chains are almost terminated with hydroxyl and chlorine as end groups. The presence of cyclic oligomers was also observed by MALDI-TOF MS analysis.

Thermal Degradation Processes of Aromatic Poly(Ether Sulfone) Random Copolymers Bearing Pendant Carboxyl Groups

Thermal degradation processes of poly(ether sulfone) random copolymers having different molar amount of diphenolic acid (DPA) units were studied by direct-pyrolysis/mass spectrometry, stepwise pyrolysis-gas chromatography/mass spectrometry and thermogravimetric techniques. Results highlighted that thermal degradation processes occur in the temperature range from 370 to 650 °C, yielding a char residue of 32–35 wt%, which decreases as the mol% of DPA units rises. The pyrolysis/mass spectra data allowed us to identify the thermal decomposition products and to deduce the possible thermal degradation mechanisms. Thermal degradation data suggest that the decarboxylation process of the pendant acid moiety mainly occurs in the initial step of the pyrolysis of the copolymers studied. Successively, the scission of the generated isobutyl groups occurs in the temperature range between 420 and 480 °C. Known processes involving the main chain random scission of the diphenyl sulfone and diphenyl ether groups were also observed.

Synthesis and characterization of SPDSCD and its flame retardant application on epoxy resins

In this study, a flame retardant agent, 2,4,8,10-tetraoxo-3,9-diphosphospiro[5.5]undecane spirophosphate-4,4-diaminopair benzene disulfone-1,3,5-himetriazine (SPDSCD), is synthesized through a direct polycondensation reaction. SPDSCD is a chemically expanded phosphorus-containing flame retardant in epoxy resins (EP). The molecular structure of SPDSCD and thermal stability are characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy, and thermogravimetric analysis, and EP/SPDSCD composites were investigated in detail. These properties are associated with the phosphorus-containing spiro structure on the main molecular chain which can promote condensation polymerization into carbon during pyrolysis, the new nitrogen-containing carbon source, and the triazine structure. SPDSCD shows good thermal stability and low flammability, the weight loss from 500 to 800 °C was only 6.1 wt%, and the residual mass at 800 °C was 48.9 wt%. With the addition of SPDSCD, the flame retardant quality of the composites was gradually enhanced, the carbon residue becomes denser, which isolates heat transfer and inhibits the volatilization of flue gas. The addition of 20 wt% SPDSCD in the EP sample was associated with a limited oxygen index (LOI) value of 26% and a vertical burning V-0 rating. Cone calorimeter test shows that the peak heat release rate is reduced by 75%; the heat release rate curve enters the heat release platform area with a value lower than the first peak, TSP is reduced by 24%, the ac-CO₂Y value reduced by 25.6%, indicating that SPDSCD/EP produced less CO₂, which obviously prevented the combustion of volatile gas. SPDSCD exerted a charring and barrier effect in the condensation phase. Using basic characterization and flame retardancy testing, this work determined that SPDSCD has good flame retardancy when added to EP.

In this study, a flame retardant agent, 2,4,8,10-tetraoxo-3,9-diphosphospiro[5.5]undecane spirophosphate-4,4-diaminopair benzene disulfone-1,3,5-himetriazine (SPDSCD), is synthesized through a direct polycondensation reaction.

Synthesis, structure–property and flame retardancy relationships of polyphosphonamide and its application on epoxy resins

A series of polyphosphonamides (PPDA) with heteroatoms and phosphonamide structures are proposed as highly effective flame retardants in epoxy resins (EP).

Low temperature sputtered TiO2 nano sheaths on electrospun PES fibers as high porosity photoactive material

Low temperature approach based on combining electrospinning and reactive sputtering processes to realise a porous mesh of PES fibers wrapped by TiO₂ nano-sheaths, active under UV illumination.

Comparative study on polyimides derived from isomeric diphenylsulfonetetracarboxylic dianhydrides

In this study, three diphenylsulfonetetracarboxylic dianhydride (DSDA) isomers namely 2,2′,3,3′-DSDA (3,3′-DSDA), 2,3,3′,4′-DSDA (3,4′-DSDA) and 3,3′,4,4′-DSDA (4,4′-DSDA) were prepared from the corresponding diphenylthioethertetracarboxylic dianhydride isomers. Based on the three DSDA isomers, a series of isomeric polyimides were prepared. The properties, such as film-forming ability, solubility, wide-angle x-ray diffraction, thermal and mechanical properties as well as rheological behavior, were compared among the isomeric polyimides. It was found that 4,4′-DSDA-based polyimides had much better film-forming ability than 3,3′-DSDA- and 3,4′-DSDA-based polyimides. 3,4′-DSDA-based polyimides had better solubility than 3,3′-DSDA- and 4,4′-DSDA-based polyimides. Furthermore, for a given diamine, the glass transition temperatures of the polyimides from the three DSDA isomers decreased in the order of 3,3′-DSDA > 3,4′-DSDA > 4,4′-DSDA, while the 5% weight loss temperatures in both air and nitrogen atmospheres of the polyimides mainly increased in the order of 3,3′-DSDA < 3,4′-DSDA < 4,4′-DSDA. Moreover, 3,4′-DSDA- and 4,4′-DSDA-based polyimides showed much better melt stability than 3,3′-DSDA-based polyimide.