Fabio Bertini

Thermal degradation of chlorinated polystyrenes

Abstract p-Chlorostyrene was polymerized using a radical initiator, α,α′-azobis(isobutyronitrile). Polystyrene was chlorinated in the liquid phase using an SbCl3, catalyst combined with 10-trifluoroacetylphenothiazine. The chlorinated polymers were characterized spectroscopically and molecular weight measurements were carried out. The polymers were pyrolysed at 600°C, the pyrolysis products identified by means of gas chromatography/mass spectrometry and their relative percentages calculated. The differences in the products distributions gave helpful indications about the structure and the mechanism of degradation of the chlorinated polymers.

Thermal degradation of para-substituted polystyrenes

Abstract The thermal degradation of a series of para-substituted polystyrenes with electron-donating (CH3, NH2) and electron-attracting (NO2,Cl,Br) substituents has been studied in isothermal conditions at 600°C using pyrolysis chromatography/mass spectrometry and in dynamic conditions using thermogravimetry. The pyrolysis of these substituted polystyrenes gives monomer as the main product for all polymers (60–80 wt.%). The other distribution of products supports the view that thermodestruction of these polymers starts from a random chain scission. The main process for all substituted polystyrenes is depolymerization, similar to unsubstituted polystyrene. In the case of para-substituted polystyrenes a good linear dependence was found between Tmax on the thermogravimetry curve and the Hammett constants of the substituents (Tmax =403.5–67.486 σx). The results indicate that the Hammett relationship can describe quantitatively the trends in Tmax and thus thermostability of substituted polystyrenes and that thermostability of these polymers depends only on electronic nature of substituent and their possibility to stabilise macroradicals forming on chain scission.

Thermal behavior and degradation mechanism of brominated polystyrenes

Abstract Polystyrene samples have been brominated under various conditions. p-Bromostyrene has been polymerized using α,α′-azobisisobutyronitrile as initiator. The thermal behavior of these brominated polystyrenes was investigated by pyrolysis-gas chromatography/mass spectrometry and thermogravimetric analysis. The polymers have been characterized also by infrared spectroscopy and molecular weight measurements were carried out. The nature and the composition of the pyrolysis products gave useful indications about the structure and the mechanism of degradation of the brominated polymers.

Hardware components wastes pyrolysis: energy recovery and liquid fraction valorisation

Abstract Pyrolysis of hardware components wastes consisting mainly in computers and television components was performed under nitrogen. The degradation products were separated in three fractions, solid, liquid and gaseous. Analyses of the three phases were carried out using gas chromatography (GC), mass spectrometry (MS), thermal analysis and infrared spectroscopy. The energetic content of the gas phase and the economic value of the liquid phase were also determined. The gas fraction produced was rich in light hydrocarbons and hydrogen. Consequently, its calorific value was high and widely sufficient to make the pyrolysis process self-sustained. The main products of the liquid phase were phenol and isopropylphenol (ca. 50–80 wt.%). The presence of Br-based compounds, deriving from the flame retardant employed in hardware components, were also detected. A controlled combustion of the solid phase permitted to obtain the glass fibres unaltered, which can be recycled.

Hydrous pyrolysis of polystyrene

Abstract Thermal degradation of polystyrene has been investigated in the presence of water under subcritical conditions (hydrous pyrolysis). The experiments were carried out in closed systems under inert atmosphere, in the temperature range 300–350°C, at pressures up to 18 MPa, for 1–120 h. The products obtained, separated as gases, volatiles, and heavy compounds, were analyzed qualitatively and quantitatively by gas-chromatography, gas-chromatography/mass spectrometry and size exclusion chromatography. The results showed that the presence of water increases the yields of the volatile products, mainly in the first steps of the pyrolytic process, and leads to higher yields of monomer. This latter observation suggests a lowering of the secondary reactions extent.

Hydrous pyrolysis of silica-supported polystyrene

Thermal degradation of polystyrene has been studied in the presence of water under subcritical conditions (hydrous pyrolysis). The experiments were performed in closed systems under inert atmosphere, in the temperature range of 300-320°C, for 1-24 h. The results showed that the presence of water increases the yields of the volatile products, mainly in the first steps of the pyrolitic process, with a higher selectivity of monomer. In order to improve the effective phase contact between water and the polymer during the degradation, hydrous pyrolysis runs have been carried out on silica-supported polystyrene. Some of these experiments were performed using a stirred reactor. Under these conditions, the above effects appeared to be greatly emphasized. Qualitative and quantitative analyses of the degradation products have been reported for the series of runs investigated. The best recovery of styrene has been achieved at 320°C and 8 h, being close to 71%.

Investigation of thermal degradation of poly-(4-n-alkylstyrenes) with long alkyl chain (C6–C10) by pyrolysis-gas chromatography/mass spectrometry

The thermal degradation of a series of poly(4-n-alkylstyrenes), from hexyl to decyl, has been studied in isothermal conditions at 600°C using pyrolysis-gas chromatography/mass spectrometry. The type and composition of the pyrolysis products gave useful indications about the mechanism of thermal degradation. It was shown that the main thermal degradation process is depolymerization, like polystyrene. Other thermal reactions involve fragmentation of alkyl side chains. In particular, a new initiation process for depolymerization of polystyrene based polymers was found: a thermal electrocyclic reaction with the formation of divinylbenzene and alkane, and main chain scission with formation of two macroradicals. The formation of cyclic or polyaromatic structures does not take place.

Alternating olefin-carbon monoxide copolymers and their derivatives Preparation and characterization by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS)

Abstract Alternating copolymers of carbon monooxide and olefins (ethylene, styrenes and norbornadienes) and their modified polymers with primary amines, P 2 S 5 and P 2 O 5 were prepared. These were then pyrolyzed at 550°C for 10 s in a Py-GC/MS system. In each pyrolysis, hydrocarbons arising from the corresponding olefin comonomer were detected as the volatile products. Py-GC/MS confirmed that these 1,4-arrangements of the ketonic groups in the alternating copolymers were converted into pyrrole-, thiophene-, or furan-containing chains with primary amines, P 2 S 5 or P 2 O 5 , respectively. The oxygen-containing groups, which remained intact during the modification with P 2 S 5 , were detected in small amounts in the pyrolysates. While the pyrolysis of poly(dimethyl 7-oxabicyclo[2,2,1]hepta-2,5-diene-2,3-dicarboxylate) yielded benzene (derived from an acetylene triad formed by the retro-Diels Alder reaction), its alternating copolymer with carbon monoxide did not yield benzene upon pyrolysis.

Thermal degradation of alternating styrene-carbon monoxide copolymers

Abstract Thermal degradation of alternating carbon monoxide-styrene (Sty/CO) and -4-t-butylstrene (t-BuSty/CO) copolymers, which were prepared by a palladium catalyst, was studied by TGA and Py-GC/MS under different conditions, by varying pyrolysis temperature (450–600°C), sample size, heating rate of TGA, and time of flash pyrolysis (10–30 s). The main degradation products of Sty/CO in the order of abundance were styrene, ethylbenzene, toluene, and carbon monoxide. Those of t-BuSty/CO were their t-butyl derivatives. The kinetic analysis of the TGA curves gave 156 and 182 kJ mol−1 as the activation energies of Sty/CO and t-BuSty/CO, respectively.

Preparation of Ethene/Carbon Monoxide Copolymers Using Copper-Based Catalysts and Their Characterization by Pyrolysis-Gas Chromatography

Ethene/carbon monoxide copolymers were prepared using the catalyst system Cu(OAc) 2 /dppp (1,3-bis(diphenylphosphino)propane)/p-toluenesulfonic acid (p-TsOH) or BF 3. OEt 2 /p-benzoquinone. Pyrolysis-gas chromatography proves the alternating structure of the copolymers.