Compatible blends of biorelated polyesters through catalytic transesterification in the melt

The transesterification during the melt blending of polylactide (PLA) and poly(butylene adipate-coterephthalate) (PBAT) was investigated in presence of Ti(OBu)4 as a catalyst. Both the effect of catalyst concentration and reaction duration was considered. The process was studied by analyzing the molecular weight of the polyesters by size exclusion chromatography (SEC). The rheological, thermal and morphological properties of the blends were investigated by melt flow rate, DSC and SEM analyses, respectively. Evidences about the formation of PBAT-PLA copolymers were obtained and discussed. The tensile properties of compression moulded films were also determined and correlated to the structure and phase morphology development of the blends. In particular, the use of Ti(OBu)4 resulted in the improvement of compatibility. Moreover, the decrease in stiffness and the increase in elongation at break with the increase of mixing time was observed, in good agreement with the improved compatibility of the modified blend

Comparative Study About Preparation of Poly(lactide)/ Organophilic Montmorillonites Nanocomposites Through Melt Blending or Ring Opening Polymerization Methods

The present article is focused onto the study of nanostructure, thermal and mechanical properties of nanocomposites composed of poly(lactide) (PLA), and a constant amount of montmorillonite (MMT) clays (3 wt %). Properly modified organoclays with easily available commercial compounds were prepared in order to allow the homogeneous dispersion of the hydrophilic clays in the polar polymer matrix; in particular, 2-hydroxyethyl-trimethylammonium (choline), polyethyleneoxide(15)-(hydrogenated tallow)-ammonium, and oligochitosan salts were used as surfactants as their structure can match the requirements of a biocompatible material. These organically modified MMTs (OMMTs) were used for preparing composites by melt blending or by in situ ring opening polymerization (using the clay surfactant as polymerization initiator) followed by melt dispersion into a PLA matrix. Structural, morphological, and thermo-mechanical properties of the products are compared in order to assess advantages and disadvantages of the two different preparation routes

Poly(lactic acid) (PLA) properties as a consequence of poly(butylene adipate-co-terephtahlate) (PBAT) blending and acetyl tributyl citrate (ATBC) plasticization

This study was aimed at the modulation of poly(lactic acid) (PLA) properties by the addition of both a low-molecular-weight plasticizer, acetyl tributyl citrate (ATBC), and a biodegradable aliphatic–aromatic copolyester, poly(butylene adipate-co-terephthalate) (PBAT). PLA/PBAT, PLA/ATBC, and PLA/PBAT/ATBC mixtures with 10–35 wt % ATBC and/or PBAT were prepared in a discontinuous laboratory mixer, compression-molded, and characterized by thermal, morphological, and mechanical tests to evaluate the effect of the concentration of either the plasticizer or copolyester on the final material flexibility. Materials with modulable properties, Young’s modulus in the range 100–3000 MPa and elongation at break in the range 10–300%, were obtained. Moreover, thermal analysis showed a preferential solubilization of ATBC in the PBAT phase. Gas permeability tests were also performed to assess possible use in food packaging applications. The results are discussed with particular emphasis toward the effects of plasticization on physical blending in the determination of the phase morphology and final properties

A model study of Ti(OBu)4 catalyzed reactions during reactive blending of polyethylene (PE) and poly(ethylene terephthalate)

The effect of metal catalysts in promoting the formation of the comb copolymer between a very lowdensity polyethylene (VLDPE) grafted with diethyl maleate and PET has been studied in this paper following a model study based on low molecular weight molecules resembling the local structure of the reactive groups in the reference macromolecules. Ti(OBu)4 was used as the catalyst and the reactions were carried out under the same conditions as in the case of the macromolecules species. The model mixtures have been analyzed by FT-IR, 1Hand 13CNMRspectroscopy, thermogravimetric analysis (TGA) and GC-MS and evidence of the degradation of ester bonds, deactivation of hydroxyl terminals of PET and the possible crosslinking of functionalized polyolefin have been observed. The molecular model process agrees with results obtained for the macromolecular system blending PET and VLDPE grafted with diethyl maleate in a Brabender mixer in the presence of Ti(OBu)4, as evaluated by mixer torque values and selective extraction results. Therefore, the present model study allows us to both obtain information about reaction mechanism in the complex melt biphasic system and to suggest new strategies to optimize the proces