Martino Colonna

Synthesis and radiocarbon evidence of terephthalate polyesters completely prepared from renewable resources

Monomers used for the synthesis of terephthalate polyesters have been prepared starting from renewable resources. In particular, dimethyl terephthalate was synthesised starting from bio-limonene while butanediol was synthesised starting from bio-succinic acid. Using these bio-monomers it was possible to synthesise polyesters with the same chemical structure and molecular weight of commercially available polymers. Moreover, the polymers obtained from bio-based monomers, present the same thermal properties of the polyesters obtained using petrol-derived monomers. A poly(butylene terephthalate) completely obtained from renewable resources was also synthesised. The radiocarbon and isotope mass spectroscopy analysis confirmed that this polyester contains 94 ± 3% of bio-based material.

New catalysts for poly(butylene terephthalate) synthesis: 1. Titanium–lanthanides and titanium–hafnium systems

Abstract A complete study of the catalytic activity of lanthanide- and hafnium acetylacetonate catalysts in PBT synthesis was conducted in order to investigate any improvement in the process and/or in the properties of the final polymer with respect to the industrially used titanium tetrabutoxide (TBT) catalyst. Small scale polymerization and subsequent scale up in higher capacity reactors showed that TBT-Hf(acac) 4 and TBT-La(acac) 3 mixed catalysts were more active with respect to TBT as single catalyst. Decreases in polymerization time and THF formation were also observed, which in turn can improve the productivity of the whole process. Furthermore, for similar values of molecular weight, a lower melt viscosity (and thus better processability and crystallizability) was obtained by using mixed catalysts, presumably due to weaker interactions of the polymer terminal groups to lanthanum and hafnium metals with respect to titanium.

Sustainable polyesters for powder coating applications from recycled PET, isosorbide and succinic acid

A new method for the synthesis of polyesters that combines the chemical recycling of poly(ethylene terephthalate) (PET) with the use of monomers derived from renewable resources, such as isosorbide and succinic acid, has been developed. A kinetic study has been performed in order to determine the best catalyst for PET depolymerisation with isosorbide and for the subsequent polycondensation of PET oligomers with succinic acid. Using the correct amounts of isosorbide and succinic acid it is possible to obtain polymers which well fit the properties (glass transition temperature and end-group composition) necessary for powder coating applications. The coating produced using this new environmentally friendly approach presents applicative properties similar, and in some cases superior, to those of a commercial coating obtained from non-renewable resources.

New catalysts for poly(butylene terephthalate) synthesis. Part 3: effect of phosphate co-catalysts

Abstract An exhaustive study of the co-catalytic activity of phosphates on titanium and titanium/hafnium based catalytic systems in poly(butylene terephthalate) synthesis was conducted in order to investigate any improvement in the process and/or in the properties of the final polymer with respect to the industrially used titanium based catalyst. Small scale polymerisation and subsequent scale up in higher capacity reactors showed a strong co-catalytic effect of phosphates. A screening on model compounds showed NaH 2 PO 4 to be the most active co-catalyst. The co-catalysts had a stronger effect on titanium with respect to hafnium. Decreases in polymerisation time and tetrahydrofuran formation were observed, which in turn can improve the productivity of the whole process. Moreover, the use of phosphate improved the thermal stability of the final polymers.

Effect of carboxyl end groups content on the thermal and electrical properties of poly(propylene terephthalate)

Abstract Poly(propylene terephthalate) (PPT) samples with different carboxyl terminal groups content were synthesized in bulk and characterized in terms of chemical structure and molecular weight. The thermal behavior was examined by thermogravimetric analysis and differential scanning calorimetry. All the polymers under investigation show a good thermal stability, however decreasing with increasing carboxyl terminal groups content. No significant change of the glass transition temperature as well as melting temperature values was found in the samples under investigation; on the contrary, the crystallization rate of PPT was found to be affected by carboxyl terminal groups content, regularly decreasing as the amount of –COOH terminal groups is increased. This trend was interpreted on the basis of the interactions among the terminal groups of the polymeric chains, which determine a decrease in the chain mobility. Direct current (dc) electrical behavior was also investigated. The dc charging/discharging currents and electrical conductivity are studied as a function of temperature, time of applied voltage and amount of –COOH terminal groups. The conductivity values were found to increase as the content of –COOH end groups was increased, due to an increment of amount of ionic charge carriers.

New catalysts for poly(butylene terephthalate) synthesis. 2. Kinetic comparison using model compounds

Abstract A kinetic study of poly(butylene terephthalate) polymerization from dimethyl terephthalate and butanediol, using a catalyst mixture composed of titanium tetrabutoxide and hafnium acetylacetonate, in 1:3 molar ratio, was performed and compared to the standard titanium only catalyst. Arrhenius parameters were obtained from model reactions for both stages of polymerization. The mixed catalyst showed a consistently higher pre-exponential factor ( A ) and a higher activation energy ( E a ) in the Arrhenius equation compared to the industrially used catalyst. For this reason the mixed catalyst, as observed in actual polymerizations, is more active at high temperature.

Bactericidal Activity of Aqueous Acrylic Paint Dispersion for Wooden Substrates Based on TiO2 Nanoparticles Activated by Fluorescent Light

The photocatalytic effect of TiO2 has great potential for the disinfection of surfaces. Most studies reported in the literature use UV activation of TiO2, while visible light has been used only in a few applications. In these studies, high concentrations of TiO2, which can compromise surface properties, have been used. In this work, we have developed an acrylic-water paint dispersion containing low TiO2 content (2 vol %) for the inactivation of microorganisms involved in hospital-acquired infections. The nanoparticles and the coating have been characterized using spectroscopic techniques and transmission electron microscopy, showing their homogenous dispersion in the acrylic urethane coating. A common fluorescent light source was used to activate the photocatalytic activity of TiO2. The paint dispersion showed antimicrobial activity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The coating containing the TiO2 nanoparticles maintained good UV stability, strong adhesion to the substrate and high hardness. Therefore, the approach used is feasible for paint formulation aimed at disinfection of healthcare surfaces.

A Sustainable Route to a Terephthalic Acid Precursor.

A new synthetic pathway for the production of p-toluic acid has been developed starting from reagents derived from renewable resources. A Diels-Alder reaction between sorbic and acrylic acids is followed by a combined dehydrogenation/ decarboxylation process, providing p-toluic acid in high yields. This route permits to use milder conditions compared to other Diels-Alder approaches reported in the literature, and therefore can contribute to a more sustainable terephthalic acid production.

A Novel One-Pot Synthesis Ofesters Byexchange Reactions between Carbonates and Anhydrides

Abstract A new method for the synthesis of esters by exchange reaction between anhydrides and carbonates, without any solvent, in the presence of Ti or Sn based catalyst is presented.

Modification of PET by reactive blending with sulfonated esters, 1. Synthesis and characterization of PET-ionomers

A new route of synthesis of ionomers has been found: when PET is treated in a Brabender with a sulfonated ester, transesterification reactions occur providing a new polymer, characterized by a lower molecular weight and ionic groups as chain ends. The presence of the ionic groups causes strong modifications in the thermal properties of the material.