Bio-based Blends Research Articles

Fully Bio-Based Blends of Poly (Pentamethylene Furanoate) and Poly (Hexamethylene Furanoate) for Sustainable and Flexible Packaging.

In the present study, bio-based polymeric blends have been prepared for applications in the field of sustainable food packaging, starting from two furan-based homopolymers, poly(hexamethylene 2,5-furanoate) (PHF) and poly(pentamethylene 2,5-furanoate) (PPeF). PHF and PPeF were synthesized by two-step melt polycondensation-a solvent-free synthetic strategy-and then binary physical mixtures, PHF/PPeF, with different weight compositions were prepared by dissolution in a common solvent. The blends were processed into compression-moulded films, and molecular, morphological, structural, thermal, and mechanical characterizations were subsequently carried out. Blending did not negatively affect the thermal stability of the parent homopolymers, and good compatibility between them was observed. This strategy also allowed for the modulation of the chain rigidity as well as of the crystallinity, simply by acting on the relative weight amount of the homopolymers. From a mechanical point of view, the presence of PPeF led to a reduction in stiffness and an increase in the elongation at break, obtaining materials with an elastomeric behaviour. Evaluation of the gas barrier properties confirmed that the good barrier properties of PHF were preserved by blending. Finally, lab-scale composting tests confirmed a greater weight loss of the mixtures with respect to the PHF homopolymer.

Exploring the Processing Potential of Polylactic Acid, Polyhydroxyalkanoate, and Poly(butylene succinate-co-adipate) Binary and Ternary Blends.

Biodegradable and bio-based polymers, including polyhydroxyalkanoate (PHA), polylactic acid (PLA), and poly(butylene succinate-co-adipate) (PBSA), stand out as sustainable alternatives to traditional petroleum-based plastics for a wide range of consumer applications. Studying binary and ternary blends is essential to exploring the synergistic combinations and efficiencies of three distinct biopolyesters. A comprehensive evaluation of melt-extruded binary and ternary polymer blends of PHA, PLA, and PBSA was conducted. Scanning electron microscopy (SEM) analyses revealed a heterogeneous morphology characteristic of immiscible blends, with a predominant spherical inclusion morphology observed in the majority of the blends. An increased PBSA concentration led to an elevation in melt viscosity and elasticity across both ternary and binary blends. An increased PHA content reduced the viscosity, along with both storage and loss moduli in the blends. Moreover, a rise in PHA concentration within the blends led to increased crystallinity, albeit with a noticeable reduction in the crystallization temperature of PHA. PLA retained amorphous structure in the blends. The resultant bio-based blends manifested enhanced rheological and calorimetric traits, divergent from their pure polymer counterparts, highlighting the potential for optimizing material properties through strategic formulation adjustments.

Miscibility prediction of polylactic acid/polyhydroxyalkanoate blends by molecular dynamics simulations

Blending polylactic acid (PLA) with polyhydroxyalkanoates (PHAs) represents a compelling approach to achieve fully bio-based blends with favorable properties. This work employed molecular dynamics (MD) simulations to study the miscibility of PLA and PHA with different side chain functional groups. The miscibility of the blends was assessed through analyzing snapshots of the blends, pair correlation function, radius of gyration, interaction energy, solubility parameter, and Flory−Huggins interaction parameter. Results revealed that the miscibility with PLA is predominantly affected by the polarity of the side chain functional group of PHA. To achieve effective blending with PLA, it is advisable to use PHAs with non-polar side chain groups. Examination of the glass transition temperature (Tg) for the miscible blends reveals that the rigidity of PLA can be reduced by blending with PHA bearing non-polar side chain functional groups.

Processing and Evaluation of Bio-Based Paramylon Ester/Poly(butylene succinate) Blends for Industrial Applications

Poly(butylene succinate) (PBS) was melt-blended with paramylon based mixed ester, paramylon propionate hexanoate (PaPrHe) and characterized for its morphology, thermal and mechanical properties. The PBS/PaPrHe blends were found to be immiscible throughout the loading range of PaPrHe (10–90 wt%), with individual glass transition peaks. Due to the immiscibility, there was phase separation observed in the bulk, evident by sea-island morphology. However, further observation of the micro-structure revealed that, in low PaPrHe loading (10–30 wt%), there was a micron to sub-micron order distribution of PBS particles and partially miscible PBS/PaPrHe phase. On increasing the PaPrHe to 50 wt% and beyond, the sub-micron scale domains fused to form a co-continuous morphology. As a result, the impact strength of PBS increased from 6.6 to 16.4 kJ/m2 in the 50/50 blend. Under tensile loading, the strength at break and elongation decreased after the introduction of less-flexible PaPrHe particles in the blend. This could be countered by uniaxially stretching the blended films with 10–30 wt% PaPrHe, after which the tensile strength increased by up to 380% (from 33–52 MPa to 165–200 MPa) compared to the unstretched films, attributable to the increased degree of orientation of the molecular chains. In terms of thermal processability, all the blend ratios had high thermal degradation temperature (>350 °C), higher than the melt-flow temperature (124–133 °C) providing a wide processing window. Overall, PBS/PaPrHe blend is a novel bio-based blend with properties suitable for packaging, mulching, and related applications.

Industrial byproducts as adhesive allies: Unraveling the role of proteins and isocyanates in polyurethane wood bonding

Wooden structures are becoming increasingly popular in the construction world. However, these structures often rely on synthetic adhesives, raising concerns about the environmental risks associated with their chemical composition. In response to these concerns, this study aims to explore sustainable alternatives, particularly focusing on polyurethane adhesives that incorporate proteins from industrial byproducts. The investigation involved three protein sources: soybean meal, shrimp shells, and skim milk, modified under mild alkaline conditions to obtain protein concentrates. These concentrates were then incorporated into the adhesives at varying protein contents: 5%, 10%, and 15%. Additionally, two isocyanate systems were examined, one being petrochemical-based and the other a partially bio-based blend. Chemical, thermal, optical, and mechanical characterizations were conducted to evaluate the adhesive performance. This study demonstrates that the adhesives’ thermal properties remain unaffected by both the protein content and the isocyanate system. However, these factors influence the adhesive penetration into the wood substrate. Ultimately, the results suggest that higher protein content offers superior retention of mechanical strength in adhesives compared to the petrochemical reference when subjected to humid conditions. Overall, this research demonstrates the potential of proteins from industrial byproducts as sustainable adhesive allies, providing valuable insights into their interactions with different isocyanates.

Understanding the Effects of Adding Metal Oxides to Polylactic Acid and Polylactic Acid Blends on Mechanical and Rheological Behaviour, Wettability, and Photo-Oxidation Resistance.

Biopolymers are of growing interest, but to improve some of their poor properties and performance, the formulation of bio-based blends and/or adding of nanoparticles is required. For this purpose, in this work, two different metal oxides, namely zinc oxide (ZnO) and titanium dioxide (TiO2), at different concentrations (0.5, 1, and 2%wt.) were added in polylactic acid (PLA) and polylactic acid/polyamide 11 (PLA/PA11) blends to establish their effects on solid-state properties, morphology, melt behaviour, and photo-oxidation resistance. It seems that the addition of ZnO in PLA leads to a significant reduction in its rigidity, probably due to an inefficient dispersion in the melt state, while the addition of TiO2 does not penalize PLA rigidity. Interestingly, the addition of both ZnO and TiO2 in the PLA/PA11 blend has a positive effect on the rigidity because of blend morphology refinement and leads to a slight increase in film hydrophobicity. The photo-oxidation resistance of the neat PLA and PLA/PA11 blend is significantly reduced due to the presence of both metal oxides, and this must be considered when designing potential applications. The last results suggest that both metal oxides could be considered photo-sensitive degradant agents for biopolymer and biopolymer blends.

Dielectric and rheological performances of cellulose acetate, polylactic acid and polyhydroxybutyrate-co-valerate biobased blends

This study presents a new approach to formulating cellulose acetate (CA), polylactic acid (PLA), and polyhydroxybutyrate-co-valerate (PHBV) biobased blends, with a focus on their dielectric and rheological performances for an electrical insulation application. FTIR and rheological analysis showed a molecular interaction in PHBV:CA and PLA:CA blends between the carbonyl groups of PLA and PHBV, and the hydroxyl groups of CA. Dielectric study showed that temperature, frequency, and polymer nature are key parameters influencing the blends' dielectric constant (ε′) and loss factor (ε'') for room and high temperatures. Even though CA-based blends possessed the highest dielectric constants at room temperature, they showed the lowest thermal-sensitive behavior. The measured dielectric properties showed potential applications of PLA-based blends for low-temperature electrical insulation and CA-based blends for high-temperature electrical insulation.

Influence of Biochar and Bio-Oil Loading on the Properties of Epoxy Resin Composites.

In this study, we evaluated the use of bio-oil and biochar on epoxy resin. Bio-oil and biochar were obtained from the pyrolysis of wheat straw and hazelnut hull biomass. A range of bio-oil and biochar proportions on the epoxy resin properties and the effect of their substitution were investigated. TGA curves showed improved thermal stability for degradation temperature at the 5% (T5%), 10% (T10%), and 50% (T50%) weight losses on bioepoxy blends with the incorporation of bio-oil and biochar with respect to neat resin. However, decreases in the maximum mass loss rate temperature (Tmax) and the onset of thermal degradation (Tonset) were obtained. Raman characterization showed that the degree of reticulation with the addition of bio-oil and biochar does not significantly affect chemical curing. The mechanical properties were improved when bio-oil and biochar were incorporated into the epoxy resin. All bio-based epoxy blends showed a large increase in Young's modulus and tensile strength with respect to neat resin. Young's modulus was approximately 1955.90 to 3982.05 MPa, and the tensile strength was between 8.73 and 13.58 MPa for bio-based blends of wheat straw. Instead, in bio-based blends of hazelnut hulls, Young´s modulus was 3060.02 to 3957.84 MPa, and tensile strength was 4.11 to 18.11 Mpa.

Effect of Cross-Linkers on the Processing of Lignin/Polyamide Precursors for Carbon Fibres

This work reports the use of cross-linkers in bio-based blends from hydroxypropyl-modified lignin (TcC) and a bio-based polyamide (PA1010) for possible use as carbon fibre precursors, which, while minimising their effects on melt processing into filaments, assist in cross-linking components during the subsequent thermal stabilisation stage. Cross-linkers included a highly sterically hindered aliphatic hydrocarbon (Perkadox 30, PdX), a mono-functional organic peroxide (Triganox 311, TnX), and two different hydroxyalkylamides (Primid® XL-552 (PmD 552) and Primid® QM-1260 (PmD 1260)). The characterisation of melt-compounded samples of TcC/PA1010 containing PdX and TnX indicated considerable cross-linking via FTIR, DSC, DMA and rheology measurements. While both Primids showed some evidence of cross-linking, it was less than with PdX and TnX. This was corroborated via melt spinning of the melt-compounded chips or pellet-coated TcC/PA1010, each with cross-linker via a continuous, sub-pilot scale, melt-spinning process, where both Primids showed better processability. With the latter technique, while filaments could be produced, they were very brittle. To overcome this, melt-spun TcC/PA1010 filaments were immersed in aqueous solutions of PmD 552 and PmD 1260 at 80 °C. The resultant filaments could be easily thermally stabilised and showed evidence of cross-linking, producing higher char residues than the control filaments in the TGA experiments.

Tailoring thermal and thermomechanical properties of biobased blends by hybridization of difuran benzoxazine with polysiloxane‐based benzoxazine and epoxy monomers

AbstractA difuran bio‐based benzoxazine (SA‐dfda) was synthesized by a three‐stage process from difurandiamine (DFDA) and 2‐hydroxybenzaldehyde with a final yield of 90%. Three copolymer systems were prepared by blending the difuran bio‐resin with epoxy resin (DGEBA), conventional benzoxazine (BA‐a), and polysiloxane‐based benzoxazine precursor [Pr(BA‐3aptms)] at different ratios. In order to study the effect of the renewable content on the main characteristics of the materials, thermal, thermomechanical, and morphological analyses were performed. The bio‐based benzoxazine/epoxy systems exhibited the lowest polymerization temperature with enhanced processability. However, the incorporation of epoxy slightly decreased the mechanical properties of materials. Bio‐based copolymers containing 5 wt%. of polysilsesquioxane precursor showed the highest glass transition temperatures, thermal stability, and char yields. All the copolymers exhibited good flame retardant properties as it was observed by their limiting oxygen index values (>21) and UL‐94 tests (V‐0 or V‐1). The copolymerization of bio‐based benzoxazines with different thermoset resins such as epoxy or benzoxazines can be used as a strategy to develop novel materials with tailor‐made properties.

“In situ” compatibilization of poly(L-lactic acid)/epoxidized soybean oil bio-blends by reactive additives

Three reactive additives, i.e., dicumyl peroxide (DCP), styrene-glycidyl methacrylate oligomer (Joncry® ADR 4370 S) and 1, 4-phenyl diisocyanate (PDI), were used to compatibilize polyL-lactic acid (PLLA)/epoxidized soybean oil (ESO) bio-based blends via one-step melt blending. The bio-blends were characterized by means of Fourier transform infrared spectroscopy, field emission scanning electron microscopy, dynamic mechanical analysis, dynamic rheological analysis, thermogravimetric analysis, contact angle testing, differential scanning calorimetry and tensile testing. It is confirmed that the reactive additives interact with PLLA and ESO, and “in situ” graft copolymers are formed, which improves the interfacial compatibility. The stiffness of PLLA/ESO/additive bio-blends is greater than that of the PLLA/ESO blend, reflecting the enhanced interfacial adhesion between the PLLA and ESO phases. The melt viscosity and elasticity of the PLLA/ESO/4370 S and PLLA/ESO/PDI bio-blends are significantly improved, showing obvious non-Newtonian behaviors because of branched entanglements generated by chain extensions. However, the addition of DCP reduces the complex viscosity because the chain scissions destroy the macromolecular entanglements. The thermostability of the PLLA/ESO blend is decreased by the reactive additives. The surface hydrophobicity of PLLA/ESO/additive blends is improved due to the formation of branched grafts. The crystallinity of PLLA/ESO/additive bio-blends is increased because the “in situ” grafts serve as nucleating agents. The tensile strengths of the PLLA/ESO/4370 S and PLLA/ESO/PDI bio-blends are significantly increased due to the enhanced interface adhesion. The inferior tensile properties of the PLLA/ESO/DCP blends are ascribed to the degradation of the PLLA matrix. “In situ” reaction mechanisms for the compatibilized blends are proposed.

Preparation and properties of binary green blends from poly(butylene succinate-co-adipate) and β-(1,3)-d-glucan ester derivative

Propionate-hexanoate mix ester of paramylon (PaPrHe), a bio-based β-(1,3)- d -glucan photosynthesized by Euglena, was blended with poly(butylene succinate- co -adipate) (PBSA) and analysed for its physical properties. The morphology of the blend was revealed using a combination of selective enzymatic etching and SEM. The morphology changed from phase separated to co-continuous and then uniform dispersion with increasing PBSA content. In particular, the 10% PaPrHe loading had a unique sub-micron level dispersion with a median particle diameter of 0.6 μm. This ratio also had the highest toughness (67.3 kJ/m 2 ) among all the ratios, surpassing even neat PBSA (53.2 kJ/m 2 ). X-ray analyses of thermally stretched films showed high degree of orientation (94%) and crystallinity in the PBSA rich blends, leading to a 160–400% increase in the tensile strength. All the blend ratios had high thermal stability and melt-processability making the PBSA/PaPrHe green blend a sustainable alternative for packaging and mulch-film applications. • Bio-based blends from PaPrHe and PBSA were prepared using melt-extrusion. • 90/10 PBSA/PaPrHe had a sub-micron level dispersion with median particle dia: 0.6 μm. • The elongation at break and toughness could be tuned based on PBSA loading. • X-ray analyses of stretched films show high degree of orientation and crystallinity. • All the blend ratios had high thermal stability suitable for several applications.

Electrospun Poly(3-Hydroxybutyrate-Co-3-Hydroxyvalerate)/Olive Leaf Extract Fiber Mesh as Prospective Bio-Based Scaffold for Wound Healing.

Polyhydroxyalkanoates (PHAs) are a family of biopolyesters synthesized by various microorganisms. Due to their biocompatibility and biodegradation, PHAs have been proposed for biomedical applications, including tissue engineering scaffolds. Olive leaf extract (OLE) can be obtained from agri-food biowaste and is a source of polyphenols with remarkable antioxidant properties. This study aimed at incorporating OLE inside poly(hydroxybutyrate-co-hydroxyvalerate) (PHBHV) fibers via electrospinning to obtain bioactive bio-based blends that are useful in wound healing. PHBHV/OLE electrospun fibers with a size of 1.29 ± 0.34 µm were obtained. Fourier transform infrared chemical analysis showed a uniform surface distribution of hydrophilic -OH groups, confirming the presence of OLE in the electrospun fibers. The main OLE phenols were released from the fibers within 6 days. The biodegradation of the scaffolds in phosphate buffered saline was investigated, demonstrating an adequate stability in the presence of metalloproteinase 9 (MMP-9), an enzyme produced in chronic wounds. The scaffolds were preliminarily tested in vitro with HFFF2 fibroblasts and HaCaT keratinocytes, suggesting adequate cytocompatibility. PHBHV/OLE fiber meshes hold promising features for wound healing, including the treatment of ulcers, due to the long period of durability in an inflamed tissue environment and adequate cytocompatibility.

Tuning mechanical properties of poly (vinyl alcohol) and its influence on different concentrations of epoxidized vegetable oils

The proliferation in substituting traditional petrochemical-based polymer with biobased polymer blends to achieve sustainable materials with outstanding physical, mechanical properties, and biodegradability has been investigated. To emanate biodegradable films with better mechanical properties, the biobased blend of poly (vinyl alcohol) (PVA) was formed with three different oil epoxies namely Castor Oil Epoxy (COE), Mustard Oil Epoxy (MOE), and Til Oil Epoxy (TOE) with varying weight ratios. To examine the changes in physical and mechanical properties, various tests were performed such as tensile test, Shore-D hardness test, and sealability. The permeability of the samples has been studied by the water vapor transmission rate test. Solubility tests in various solvents impart an idea about the workable environment of the samples. Among different PVA/COE blends, the PVA/COE 80/20 blend showed the highest tensile strength while the highest hardness and elongation at break percentage was observed in PVA/COE 60/40 blend. In the case of PVA/MOE blends, PVA/MOE 40/60 blend displayed the best results for hardness and tensile strength while PVA/MOE 30/70 blend possessed the highest value for percentage elongation at break. Lastly, PVA/TOE 30/70 blend exhibited the highest value for tensile strength and percentage elongation at break. PVA/MOE 20/80 sample performed best in a basic environment. In nutshell, PVA modification with epoxide oil can improve the mechanical and biodegradable properties owing to the enhanced crosslinking and hydrophobic association. Ultimately, it was found that PVA/COE 80/20 blend has the best properties to be used as a film forming material as it has performed better or shown comparable properties in most of the tests. The resultant films can be widely used in the packaging industry for packing foodstuffs like fruit, vegetables, dairy products, etc., and also for drink packaging (beverage packaging).

Tailoring compatibility and toughness of microbial poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/bio-based polyester elastomer blends by epoxy-terminated hyperbranched polyester

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a type of promising bio-based thermoplastic for food packaging but find restricted industrial applications due to its brittleness and poor processability that is caused by its large spherulite sizes. In this study, for the purpose of toughening PHBV, bio-based engineering polyester elastomers (BEPE) were synthesized and blended with PHBV to prepare fully bio-based blends. In order to improve the compatibility and toughness of the BEPE/PHBV blends, epoxy-terminated hyperbranched polyesters (EHBP) were synthesized, which could be homogeneously dispersed into the PHBV/BEPE blends and improve the compatibility between the two phases of the matrix. The results showed that compared to those of the PHBV/BEPE blends, the elongation at break, impact strength and tensile toughness of the PHBV/BEPE blends with 3.0phr EHBP were enhanced by 134.2 %, 76.8 %, and 123.5 %, respectively. The crystallization study demonstrated the crystallization rate of PHBV/BEPE blends decreased due to the addition of EHBP. The reasons lied in that the addition of EHBP leads to chemical cross-linking between PHBV and BEPE. Meanwhile, the formation of hydrogen bonding, co-crystallization and chain entanglement increased the adhesion between PHBV and BEΡE, which generated the superior toughness of the blends.

Morphology and permeability of bio-based poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene succinate) (PBS) and linear low-density polyethylene (LLDPE) blend films control shelf-life of packaged bread

Poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene succinate) (PBS) and linear low-density polyethylene (LLDPE) were blended to produce bio-based packaging via blown-film extrusion. Blend ratios modified morphology, crystallinity and relaxation temperatures (T α ) of the films. Binary mixtures caused phase separation and non-homogeneous fibrous microstructures of immiscible polymers. Bio-based blend films containing LLDPE (LLDPE/PBAT and LLDPE/PBS) gave less homogeneous structures than PBAT/PBS films. The formation of oriented fibrous networks subsequently controlled mechanical and barrier properties of the blend films. LLDPE blending modified C=O carbonyl groups in PBAT and PBS, forming voids in topographic images indicating incompatibility. PBAT and PBS blends showed good compatibility and adhesion of polymer interface, causing smooth and compact structures with minimal surface roughness. Incorporation of PBAT and PBS sharply reduced crystallinity of LLDPE/PBAT and LLDPE/PBS films. LLDPE/PBAT blends had lower T α than neat PBAT and LLDPE, while T α of PBAT/PBS blends proportionally decreased at increasing PBS which indicated diverse polymer miscibility and molecular mobility. Water vapor permeability (WVP) and oxygen permeability (OP) fitted with polynomial and exponential equations, respectively and depended on blend ratios. Films containing higher PBS had combined higher WVP and lower OP, delaying fungal growth in packaged bread due to dehydration. Ratios of PBAT, PBS and LLDPE blend films clearly affected mold growth and crumb hardness during storage. Regardless of film components, the firmness of bread crumbs increased linearly with package WVP. Conversely, mold growth had insignificant correlation with OP. Moisture loss from bread crumbs due to high WVP showed dominant effects on microbial growth. Blending PBAT and PBS modified the morphology and permeability of bio-based films and increased the shelf-life of packaged bread. • Systematic investigations for packaging properties in bio-based PBAT/PBS/PE blends. • FTIR intensity ratios effectively monitor bonding and morphology modifications. • H 2 O and O 2 permeability in PBAT/PBS/PE blends fitted to cubic and exponential model. • Hardness of packaged bread linearly increased with water vapor permeability. • Water vapor permeability majorly affected mold growth and increasing crumb hardness.

Rheology of complex biobased quaternary blends: Poly(lactic acid) [poly(ethylene oxide)]/poly(ether-b-amide)/poly(amide 11)

Linear and nonlinear viscoelastic approaches are used to study multiphase biobased blends of poly(lactic acid), poly(amide 11), poly(ether-b-amide) (PEBA), and poly(ethylene oxide) (PEO) in a wide range of compositions. The novelty of this work resides in (a) the study of hybrid quaternary blends with droplet-matrix as well as cocontinuous morphology, (b) the effect of the PEO and PEBA blend components on the rheological properties, and (c) the investigation of the nonlinear viscoelastic regime for complex hybrid blends. Correlations are established between blend morphology and rheological behavior. Among the different linear rheological approaches, i.e., elastic modulus, complex viscosity, yield stress, Cole–Cole plots, Han plots, and Mavridish–Shroff or Booij–Palmen plots, the latter is the most sensitive allowing extraction of a relaxation time from the plot. The results correlate reasonably well with the different morphologies of the blends. Both, linear and nonlinear methods lead to compatible results, distinguishing among blends with droplet-matrix, partially continuous dispersed phase and fully cocontinuous morphologies. Moreover, for the first time, the analysis of the nonlinear parameter, Q0, allows a qualitative comparison of the interfacial areas of blends with a dispersed phase-matrix morphology at different continuity levels and those with cocontinuous morphology.

Lifting the quality of fused filament fabrication of polylactic acid based composites

The development of well-designed polylactic acid (PLA) based composite filaments through fused filament fabrication (FFF) is crucial, as PLA printed parts are characterized by a high brittleness. Here we focus on FFF composite formation using ductile poly (butylene adipate-co-terephthalate) (PBAT), the nanoclay cloisite and the chain extender Joncryl. A high modulus, flexibility, toughness and notched impact strength result upon combining PLA/PBAT (80:20; mass basis) with a sufficiently high cloisite amount (1–5 phr) supported by a suited Joncryl amount (0.3 phr). A fine PBAT dispersion is then ensured, as confirmed by scanning and transmission electron microscopy. For high cloisite amounts (e.g. 10 phr) the crystallinity and vicat softening temperature enhance but cloisite aggregation is unavoidable, leading to a strong reduction in tensile strain and toughness. Annealing increases crystallinity thus material strength, rigidity and impact, at least partially overruling the need of a fine dispersion. Novel radar charts are also reported to select an optimal bio-based blend suitable for different end-user applications by adjusting the composition and possible post-annealing of printed products.

Poly(lactic acid) (PLA)/Poly(butylene succinate-co-adipate) (PBSA) Compatibilized Binary Biobased Blends: Melt Fluidity, Morphological, Thermo-Mechanical and Micromechanical Analysis.

In this work poly(lactic) acid (PLA)/poly(butylene succinate-co-adipate) (PBSA) biobased binary blends were investigated. PLA/PBSA mixtures with different compositions of PBSA (from 15 up to 40 wt.%) were produced by twin screw-extrusion. A first screening study was performed on these blends that were characterized from the melt fluidity, morphological and thermo-mechanical point of view. Starting from the obtained results, the effect of an epoxy oligomer (EO) (added at 2 wt.%) was further investigated. In this case a novel approach was introduced studying the micromechanical deformation processes by dilatometric uniaxial tensile tests, carried out with a videoextensometer. The characterization was then completed adopting the elasto-plastic fracture approach, by the measurement of the capability of the selected blends to absorb energy at a slow rate. The obtained results showed that EO acts as a good compatibilizer, improving the compatibility of the rubber phase into the PLA matrix. Dilatometric results showed different micromechanical responses for the 80–20 and 60–40 blends (probably linked to the different morphology). The 80–20 showed a cavitational behavior while the 60–40 a deviatoric one. It has been observed that while the addition of EO does not alter the micromechanical response of the 60–40 blend, it profoundly changes the response of the 80–20, that passed to a deviatoric behavior with the EO addition.

Renewable and Tough Poly(l-lactic acid)/Polyurethane Blends Prepared by Dynamic Vulcanization.

Melt blending of homopolymers is an effective way to achieve an attractive combination of polymer properties. Dynamic vulcanization of fatty-acid-based polyester polyol with glycerol and poly(l-lactic acid) (PLLA) in the presence of hexamethylene diisocyanate (HDI) was performed with the aim of toughening PLLA. The dynamic vulcanization in an internal mixer led to the formation of a PLLA/PU biobased blend. Melt torque, Fourier transform infrared (FTIR), and gel fraction analysis demonstrated the successful formation of cross-linked polyurethane (PU) inside the PLLA matrix. Scanning electron microscopy (SEM) analysis showed that the PLLA/PU blends exhibit a sea–island morphology. Gel fraction analysis revealed that a rubbery phase was formed inside the PLLA matrix, which was insoluble in chloroform. FTIR analysis of the insoluble part shows the appearance of an absorption band centered at 1758 cm–1, related to the crystalline carbonyl vibration of the PLLA component, thus suggesting the partial involvement of PLLA chains in the cross-linking reaction. The overall content of the PU phase in the blends significantly affected the mechanical properties, thermal stability, and crystallization behavior of the materials. The overall crystallization rate of PLLA was noticeably decreased by the incorporation of PU. At the same time, polarized light optical microscopy (PLOM) analysis revealed that the presence of the PU rubbery phase inside the PLLA matrix promoted PLLA nucleation. With the formation of the PU network, the impact strength showed a remarkable increase while Young’s modulus correspondingly decreased. The blends showed slightly reduced thermal stability compared to the neat PLLA.