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

Micromechanical analysis and fracture mechanics of Poly(lactic acid) (PLA)/Polycaprolactone (PCL) binary blends

Even Poly(lactic acid)/polycaprolactone (PLA/PCL) blends have been studied in literature, the deformation mechanism that is related to the toughness increment with respect to pure PLA has not been investigated in detail. The novelty of this work is to understand in depth the correlation between the micromechanical deformation processes occurring in PLA/PCL blends to the macromechanical properties, their morphology and their fracture mechanism.PLA/PCL blends containing increasing amount of PCL (from 10 up to 40 wt%) were produced. A novel characterization approach, not yet investigated for these blends, was carried out by dilatometric uniaxial tests using a videoextensometer. The shape of the dilatometric curves coupled with SEM analysis revealed how changing the PCL amount different concurrent micromechanical deformation processes occurred. When 10 wt% of PCL was added only particles debonding occurred leading to lower enhancement of elongation at break; at 20 wt% both debonding and voids growth along the tensile direction occurred, while at 40 wt% of PCL shear yielding was predominant that lead to a great enhancement of the elongation at break. The PLA/PCL blends capability to absorb energy at slow rate, was evaluated by the elasto-plastic fracture approach based on the ESIS load separation criterion. The results obtained was then correlated with the final blend morphology

Wheat bran addition as potential alternative to control the plasticizer migration into PLA/PBSA blends

Wheat bran (WB) was investigated as potential filler for controlling the plasticizer migration in poly(lactic acid) (PLA)/poly(butylene succinate adipate) (PBSA) binary blends (with 60 wt.% of PLA and 40 wt.% of PBSA). The migration process of three different biobased and biodegradable plasticizers [Triacetin (TA), acetyl tri-n-butyl citrate (ATBC) and oligomeric lactic acid (OLA)] was investigated adding them at a fixed amount of 10 wt.%. TA revealed the greater mass loss over the time as confirmed from the calculation of the diffusion coefficients. The addition of WB in different amount (from 10 to 30 wt.%) revealed its tendency to influence the diffusion process in a manner strictly dependent on its content. The great dimensions of the WB, however, weaken the material suggesting to adopt a preliminary dimensional reduction of the filler to mitigate the negative effect observed on the mechanical properties. From this study emerged the WB potential to be used as filler for controlling the plasticizer migration, thus suggesting a possible valorization of this waste byproduct in biobased and biodegradable materials

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