Corrado Berti

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.

PET/PC blends and copolymers by one-step extrusion: 1. Chemical structure and physical properties of 5050 blends

Abstract Reactive blending on poly(ethylene terephthalate) (PET) and bisphenol A polycarbonate (PC) with a catalyst mechanically dispersed on polymers was performed by one-step extrusion for about 1 min at 275°C. The product appeared to be a transparent amorphous plastic with a single glass transition temperature. This approach provides a possibility to produce PET/PC block copolymers directly by extrusion of homopolymers or to create their compatible blends during one-step extrusion by varying the type and concentration of the catalyst.

PET/PC blends and copolymers by one-step extrusion: 2. Influence of the initial polymer composition and type of catalyst

One-step extrusion proved to be an innovative technique for the production of poly(ethylene terephthalate)/bisphenol A polycarbonate (PET/PC) compatible blends and copolymers by transesterification in the presence of a small amount of catalyst which was mechanically dispersed on the polymers before their extrusion. This method provides possibilities for producing a variety of polymeric materials with different thermal and physico-chemical properties by varying the initial polymer compositions, concentrations and type of catalyst.

Reactive blending of poly(ethylene terephthalate) and bisphenol-A polycarbonate: effect of various catalysts and mixing time on the extent of exchange reactions

Abstract The catalytic activity towards exchange reactions in poly(ethylene terephthalate) (PET)-bisphenol-A polycarbonate (PC) reactive blending was compared for various lanthanide compounds (based on europium, cerium, samarium, terbium and erbium), and for titanium- and calcium/antimony-based catalysts. The effect of reaction time on the extent of reaction was studied by selective solubility tests coupled with 1 H n.m.r. and a selective degradation procedure for PC sequences was carried out to achieve information on the PET block length change. Each of the above methods can be used to get information on the reaction extent; however, a better understanding of the reaction mechanism is achieved by using more than just a single method. Titanium showed a higher catalytic activity; however, lanthanide catalysts, especially those based on samarium, europium and cerium, allowed the block length in the PC/PET block copolymers formed by exchange reactions during melt mixing to be controlled more easily, and at the same time they did not promote the side-reactions that occurred in the presence of titanium- or calcium/antimony-based catalysts.

Reactive blending of commercial PET and PC with freshly added catalysts

Reactive blending of commercial poly(ethylene terephthalate) (PET) and bisphenol A polycarbonate (PC), with catalysts added in the form of powder dispersed on the polymers just before melt mixing, was performed in a Brabender Plasticord 2000 apparatus at 275°C. Catalytic activity of the catalysts freshly added to polymers was found to be much higher as compared with that of the residues of the same type of catalysts remaining in PET after its synthesis. Furthermore, the catalytic activity appeared to be strongly dependent on the structure of the ligand that influences the catalyst solubility in the polymer melt. N.m.r. spectroscopy, selective degradation of PC fragments, solubility tests in methylene chloride and d.s.c. measurements made it possible to range the catalysts studied according to their catalytic activity.

Refractive index of poly(thiocarbonate)s and poly(dithiocarbonate)s

Abstract The refractive indices and densities of recently synthesized poly(thiocarbonate)s and poly(dithiocarbonate)s were measured, and were used to determine the group contributions of thiocarbonate (OCOS) and dithiocarbonate (SCOS) groups to the molar refraction. The high refractive indices observed make these polymers, particularly the poly(dithiocarbonate)s, potentially interesting for optical applications (i.e. lenses and optical fibres).

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.

Polyethylene like polymers. Aliphatic polyesters of dodecanedioic acid 1. Synthesis and properties

A series of aliphatic polyesters has been synthesized starting from 1,12-dodecanedioic acid and aliphatic diols, bearing from 2 to 12 carbon atoms. These polymers, which were fully characterized in terms of chemical structure, molecular weight and thermal behaviour, were obtained as crystalline materials with melting points ranging from 70 to 90 °C and with a relatively high molecular weight. All the monomers used can be obtained from biomasses, as a consequence these materials can be an interesting alternative to synthetic polymers produced from petrochemical processes based on nonrenewable resources.

Sulfur containing polymers. Aromatic polydithiocarbonates and polythiocarbonates: synthesis and thermal properties

Abstract New polydithiocarbonates and polythiocarbonates were obtained by interfacial polymerization of bis(4-mercaptophenyl)methane, bis(4-mercaptophenyl)ether and bis(4-mercaptophenyl)sulfide with phosgene, bisphenol A bischloroformate and bisphenol A polycarbonate oligomers (–OH/–O–CO–Cl terminated). Polymerization process was carried out under interfacial conditions using a phase-transfer catalyst, as earlier described for the synthesis of polydithiocarbonates and polythiocarbonates from 2,2-bis(4-mercaptophenyl)propane. The structures of the polymers were examined by IR and NMR spectroscopies; their thermal properties were investigated by thermogravimetric analysis and differential scanning calorimetry. In particular, the effect of the substitution of one or both the ethereal oxygen atoms of the carbonate group by sulfur has been analyzed by comparing the Tg values and the ability to crystallize of the sulfur containing polymers with those of the corresponding polycarbonates.

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.