Polymer Degradation and Stability (v.132, #C)
Editorial Board (IFC).
Editorial by Alfonso Jiménez; Arantxa Eceiza; José M. Kenny (1).
Characterization and disintegrability under composting conditions of PLA-based nanocomposite films with thymol and silver nanoparticles by Marina Ramos; Elena Fortunati; Mercedes Peltzer; Alfonso Jimenez; José María Kenny; María Carmen Garrigós (2-10).
Active nanocomposite films based on poly(lactic acid) (PLA), thymol and silver nanoparticles (Ag-NPs) were prepared and characterized. PLA films containing 6 and 8 wt% thymol and 1 wt% Ag-NPs were processed by extrusion to obtain binary and ternary formulations. The addition of thymol and Ag-NPs modified the PLA thermal, optical and barrier properties; in particular water vapour permeability (WVP), maintaining oxygen transmission rate (OTR) values unchanged. Homogeneous surfaces in all films were obtained as proved by FESEM micrographs. The presence of the active additives enhanced the disintegration rate of PLA under composting conditions, which was completed in 14 days. Results suggest that these nanocomposite films could be considered promising degradable active packaging materials with low environmental impact.
Keywords: Poly(lactic acid); Thymol; Silver nanoparticles; Active packaging; Disintegration; Characterization;
Biodegradation behavior of starch-PVA films as affected by the incorporation of different antimicrobials by Amalia I. Cano; Maite Cháfer; Amparo Chiralt; Chelo González-Martínez (11-20).
The effect that the incorporation of different antimicrobial substances into S-PVA films had on their disintegration and biodegradation process was analysed. To this end, starch, PVA and S-PVA films containing different concentrations of neem oil, oregano essential oil and silver nanoparticles were submitted to composting conditions in order to determine the disintegration and biodegradability percentages for 73 and 45 days, respectively. Additionally, thermogravimetric and structural analyses were also carried out throughout the composting period. The biodegradation and disintegration behavior of S-PVA films was intermediate between S and PVA films. The addition of neem and oregano essential oils slightly affected the biodegradation and disintegration profile of starch-PVA films, enhancing both disintegration and biodegradation levels. So, the presence of these antimicrobials did not compromise the compostable and biodegradable character of the starch-PVA blend films. Nevertheless, the biodegradation capacity of films containing 9.8% silver species was seriously affected, reaching values of only 58% after 45 days of composting, despite their high disintegration capacity. Thus, lower silver concentrations are recommended in order to avoid possible alterations in compost microbial activity.
Keywords: Neem oil; Oregano essential oil; Silver nanoparticles; Composting process; Disintegration;
Polyurethane elastomers from polyols based on soybean oil with a different molar ratio by Kamila Mizera; Joanna Ryszkowska (21-31).
The aim of this work was to determination of the influence of different molar mass of used soybean oil (SO)- based polyols on the properties of tested polyurethane elastomers (PUR), with a different content of hard segments (HS). The chemical structure and degree of phase separation of tested materials were characterized via Fourier transform infrared spectroscopy (FTIR). The thermal properties were determined by thermogravimetry (TGA) and differential scanning calorimetry (DSC). The mechanical properties were tested by dynamic mechanical thermal analysis (DMTA) and by static tensile test. Also hardness and wear resistance were carried out. The replacement of the petrochemical polyol by soy-based polyol make changes in chemical constitutions and thermal decomposition of PURs. PURs with SO polyol with lower molar mass had a higher thermal resistance, mechanical and physico-mechanical properties.
Keywords: Polyurethane elastomers; Soybean oil; Hard segments; Molar ratio;
Modification of flexible polyurethane foams by the addition of natural origin fillers by Anna Bryśkiewicz; Milena Zieleniewska; Katarzyna Przyjemska; Piotr Chojnacki; Joanna Ryszkowska (32-40).
A series of flexible polyurethane foams (FPFs) with the addition of substrates from renewable resources were prepared, in order to investigate the influence of these fillers on the foam’s properties. For this purpose, FPFs were synthesized with the addition of walnut shells and hazelnut shells. Thermogravimetric Analysis (TGA) was used to assess the influence of these filler on thermal stability and degradation processes of polyurethane foams. Phase transitions in tested foams were analyzed using Differential Scanning Calorimetry (DSC) and Dynamical Mechanical Analysis (DMA). Fourier Transformed Infrared Spectroscopy (FTIR) was carried out, in order to assess the influence of tested fillers on chemical structure of FPFs. Moreover, a series of physical (apparent density) and mechanical (hardness, flexibility, irreversible strain) measurements were carried out, in order to assess the influence of this type of modification on the properties of polyurethane foams. Results of these measurements indicate that it is possible to prepare FPFs with the addition of fillers from renewable resources, with improve thermal stability and desired physical and mechanical properties.
Keywords: Flexible polyurethane foam; Thermal stability; Mechanical properties; Renewable resources; Walnut shells; Hazelnut shells;
The effect of phosphorus containing polyol and layered double hydroxides on the properties of a castor oil based flexible polyurethane foam by Sandra Gómez-Fernández; Lorena Ugarte; Cristina Peña-Rodriguez; M. Ángeles Corcuera; Arantxa Eceiza (41-51).
In this work the effect of the addition of a phosphorus containing polyol (E560) and different type of layered double hydroxides (LDH) to flexible polyurethane foams synthesized with a castor oil based polyol (LB50) is reported. A carbonate intercalated commercial synthetic hydrotalcite (LDH-CO3) and modified LDH with intercalated hydrogen phosphate and bis(2-ethylhexyl) hydrogen phosphate (LDH-HPO4 and LDH-HDEHP, respectively) were used. The density and the compression force deflection values of the foams increased with the addition of E560, while the effect of the different LDH depended on their dispersion degree, which was analyzed by X-ray diffraction. It was found by thermogravimetric analysis that E560 catalyzed the first degradation stage whereas LDH, especially those modified with phosphorus, showed a barrier effect which delayed the thermal degradation with respect to unfilled foams containing E560. It was also observed by pyrolysis combustion flow calorimetry that the combination of E560 with LDH led to decrease the total heat release and heat release capacity comparing to foams fully synthesized with LB50. Both E560 and LDH resulted also to decrease the peak heat release rate separately in both stages of degradation.
Keywords: Layered double hydroxides; Anionic clay; Polyurethane; Polyurethane foam; Nanocomposite; Phosphorus polyol;
Biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/thermoplastic polyurethane blends with improved mechanical and barrier performance by Antonio Martínez-Abad; Jennifer González-Ausejo; José María Lagarón; Luis Cabedo (52-61).
Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) polymers pose a green alternative to fossil-fuel derived polymers, as they exhibit good biocompatibility, biodegradability and outstanding barrier performance compared to other biopolyesters. However, their excessive brittleness has not yet been overcome without compromising barrier performance. In this work, a native ester-based thermoplastic polyurethane (TPU) not stabilised against hydrolysis, has been thoroughly assessed for the first time as an additive in melt blends with PHBV. Phase segregation in scanning electron microscopy (SEM) confirmed the immiscibility of the two polymers, however a degree of interaction has been found. Wide-angle X-ray scattering and differential scanning calorimetry revealed no major effect of the TPU on the crystallinity of the PHBV phase. The onset and kinetics of thermal degradation was not altered by the presence of the TPU up to 50 wt% content. Blends with increasing TPU contents showed a gradual decrease in the modulus of elasticity and tensile strength, while a substantial increase in elongation at break has been found for contents of TPU above 20 wt%, which resulted an improvement in the overall toughness of the blends. The excellent barrier performance of the PHBV against water vapour and aroma compounds was shown to be unaffected by TPU loads of ≤30 wt%. Full decomposition of neat PHBV and PHBV/TPU blends below 50 wt% TPU content was achieved after 40 days according to biodisintegration standards (ISO 20200). The study puts forward the potential use of TPU to improve the mechanical performance of these natural biopolyesters without compromising the barrier properties or the biodisintegratibility of the melt blends.
Keywords: PHBV; TPU; Biodisintegration; Melt blending; Biodegradable polymers;
Advanced biobased and rigid foams, based on urethane-modified isocyanurate from oxypropylated gambier tannin polyol by Alice Arbenz; Alberto Frache; Fabio Cuttica; Luc Avérous (62-68).
Rigid and biobased urethane-modified isocyanurate (PUIR) foams with an isocyanate/hydroxyl molar ratio equal to 3, were synthesized from glycerol-based and/or gambier tannin-based polyols, obtained by oxypropylation process. The content of each polyol was varied progressively and respectively from 0 to 100%. The synthesized PUIR foams were fully characterized and compared. Density, compressive modulus, thermal conductivity and closed-cell content were studied. Cell morphology was also observed by scanning electron microscopy. Furthermore, thermal stability and flammability were investigated to study the impact of the aromatic structure provided by the tannins. The results show that the tannin-based polyol favors some PUIR foams properties such as fire retardancy and high compressive strength behavior.
Keywords: Tannin; Oxypropylation; Urethane-modified isocyanurate; Foam;
Improving enzymatic polyurethane hydrolysis by tuning enzyme sorption by Caroline Gamerith; Enrique Herrero Acero; Alessandro Pellis; Andreas Ortner; Robert Vielnascher; Daniel Luschnig; Barbara Zartl; Karolina Haernvall; Sabine Zitzenbacher; Gernot Strohmeier; Oskar Hoff; Georg Steinkellner; Karl Gruber; Doris Ribitsch; Georg M. Guebitz (69-77).
In this study we investigated the ability of amidases to hydrolyse polyurethane polyester co-polymers. In order to improve enzyme adsorption, a polyamidase from Nocardia farcinica (PA) was fused to a polymer binding module from a polyhydroxyalkanoate depolymerase from Alcaligenes faecalis (PA_PBM). The activity of these enzymes and of various commercially available amidases on a synthesized soluble model substrate was compared. The recombinant native PA showed the highest activity of 10.5 U/mg followed by PA_PBM with an activity of 1.13 U/mg. Both enzymes were able to cleave the urethane bond in polyurethane-polyesters with different degree of crystallinity as shown by FTIR. According to LC-TOF analysis the monomer 4,4′-diaminodiphenylmethane (MDA) and the oligomers 4-hydroxybutyl (3-(3-aminobenzyl)phenyl)carbamate [B], bis(4-hydroxybutyl) (methylenebis(3,1-phenylene))dicarbamate [C] and 4-(((3-(3-(((4-hydroxybutoxy)carbonyl)amino)benzyl)phenyl)carbamoyl)oxy)butyl (4-hydroxybutyl) adipate [D] were released. The polymer with a higher content of the rigid segment, MDA, was hydrolysed to a lower extent. Interestingly, despite the lower activity on the soluble model substrate, the PA_PBM fusion enzyme was up to 4 times more active on the polymer when compared with the native enzyme, confirming the relevance of enzyme adsorption for efficient hydrolysis.Scheme of enzymatic PU hydrolysis by PA or PA_PBM leading to the release of 4,4′-diaminodiphenylmethane.Display Omitted
Keywords: Polyurethane; Polyamidase; Enzymatic degradation; Polyurethane model substrate; Functionalization;
Development and applicational evaluation of the rigid polyurethane foam composites with egg shell waste by Milena Zieleniewska; Michał K. Leszczyński; Leonard Szczepkowski; Anna Bryśkiewicz; Małgorzata Krzyżowska; Karolina Bień; Joanna Ryszkowska (78-86).
This study was designed towards the development of a series of rigid polyurethane foam (RPUF) composites with egg shells (ES) used as natural filler. Another goal was the determination of the filler content influence on the structure of the materials as well as on their physico-mechanical and biological properties. The synthetic procedure for the production of RPUF composites with high content of the natural filler was successfully established and the properties of obtained materials were tested using a variety of analytical procedures. Infrared spectroscopy was applied in order to analyse the chemical constitution of the materials as well as the degree of phase separation and changes related to the aging process. Scanning electron microscopy was used to determine the changes in cell structure of the materials and thermal degradation processes were investigated using thermogravimetric analysis. Powder x-ray diffraction experiments were performed in order to verify the presence of crystalline phase in the samples. Additionally the apparent density, dimensional stability, water absorption, friability and compressive strength were determined for synthesised materials. The biological properties of the obtained RPUFs were examined using the toxicity test employing human monocyte cell line as well as by bacteria adhesion tests. The selection of the optimal product was based on the optimisation of the renewable substrate content and the application properties in order to develop an environmentally-friendly material with the most valuable characteristics.
Keywords: Polyurethane foams; Renewable sources; Egg shells; Biocomposites; Mechanical properties; Biological properties;
Impact of hydrothermal ageing on the thermal stability, morphology and viscoelastic performance of PLA/sisal biocomposites by O. Gil-Castell; J.D. Badia; T. Kittikorn; E. Strömberg; M. Ek; S. Karlsson; A. Ribes-Greus (87-96).
The influence of the combined exposure to water and temperature on the behaviour of polylactide/sisal biocomposites coupled with maleic acid anhydride was assessed through accelerated hydrothermal ageing. The biocomposites were immersed in water at temperatures from 65 to 85 °C, between the glass transition and cold crystallisation of the PLA matrix. The results showed that the most influent factor for water absorption was the percentage of fibres, followed by the presence of coupling agent, whereas the effect of the temperature was not significant. Deep assessment was devoted to biocomposites subjected to hydrothermal ageing at 85 °C, since it represents the extreme degrading condition. The morphology and crystallinity of the biocomposites were evaluated by means of X-Ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The viscoelastic and thermal performance were assessed by means of dynamic mechanic thermal analysis (DMTA) and thermogravimetry (TGA). The presence of sisal generally diminished the thermal stability of the biocomposites, which was mitigated by the addition of the coupling agent. After composite preparation, the effectiveness of the sisal fibre was improved by the crystallisation of PLA around sisal, which increased the storage modulus and reduced the dampening factor. The presence of the coupling agent strengthened this effect. After hydrothermal ageing, crystallisation was promoted in all biocomposites therefore showing more fragile behaviour evidencing pores and cracks. However, the addition of coupling agent in the formulation of biocomposites contributed in all cases to minimise the effects of hydrothermal ageing.
Keywords: Biocomposites; Polylactide (PLA); Natural fibres; Sisal; Hydrothermal ageing; Degradation; Performance; Mechanical fibre effectiveness;
Design of biodegradable blends based on PLA and PCL: From morphological, thermal and mechanical studies to shape memory behavior by Iván Navarro-Baena; Valentina Sessini; Franco Dominici; Luigi Torre; Jose M. Kenny; Laura Peponi (97-108).
Blending commercial homopolymers represents a low cost and an easy scalable process to extend the use of the pristine homopolymers to an industrial level. Actually, the processing of blends by extrusion is the usual solution followed in the industry. However, commonly polymer blends are immiscible, provoking phase separation, which can be in the macro, micro or nano scale, depending on the polymers as well as on the processing conditions, affecting the final properties of the blends. Therefore, this paper aims to study the shape memory behavior in biodegradable blends based on poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) in different concentrations. A completely thermal and mechanical characterization of the blends was performed, correlating the results with the observed morphology. In addition, two different biodegradation studies were performed in order to correlate the effect of each homopolymer with the degradation behavior of the biodegradable blends.
Keywords: Biodegradable polymers; PLA; PCL; Shape memory; Polymer blends;
Impact of corona treatment on PLA film properties by Jeancarlo R. Rocca-Smith; Thomas Karbowiak; Eva Marcuzzo; Alessandro Sensidoni; Francesca Piasente; Dominique Champion; Olivier Heinz; Pauline Vitry; Eric Bourillot; Eric Lesniewska; Frédéric Debeaufort (109-116).
Different types of PLA films treated by corona are currently available in the market for coating or printing applications. However, data relative to its impact on PLA film properties are scarce and do not generally consider industrial scale production. The objective of this study was to assess the impact of corona treatment on the surface, structure and barrier properties of bi-oriented PLA films produced at industrial scale. Thus, a comparative study between corona treated (CT) and non-corona treated (NCT) PLA films was conducted.The surface of films was studied using Attenuated Total Reflectance Fourier Infrared Spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and goniometry measurements. The structure of films was analyzed with thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and uniaxial tensile analysis. The barrier properties of films to three gases (He, O2, CO2) were also determined.This study unambiguously revealed that corona treatment led to modifications in both surface and bulk of PLA films. In particular, surface analysis displayed the well-known capability of corona treatment to chemically and physically modify the surface of PLA films at the nanometer scale by increasing polarity and roughness. The structural analysis displayed a slight increase in the crystallinity degree and slight modifications in mechanical properties of films. This probably originated from temperature increase associated to corona treatment, which favored physical changes (e.g. relaxation, crystallization) of a part of the bi-orientated PLA chains, and therefore highlights the importance of such an industrial step on the film properties for packaging applications. As a result of these modifications, the barrier properties of films to three gases (He, O2, CO2) are also slightly improved.
Keywords: Poly (lactic acid) – PLA; Corona treatment; Surface modification; Food packaging; Biodegradable polymer;
Electron beam radiation effects on properties and ecotoxicity of PHBV/PLA blends in presence of organo-modified montmorillonite by Idris Zembouai; Mustapha Kaci; Stéphane Bruzaud; Isabelle Pillin; Jean-Luc Audic; Shima Shayanfar; Suresh D. Pillai (117-126).
The present article reports a study of oxidative degradation under eBeam irradiation of neat PHBV, neat PLA and PHBV/PLA blend (50/50 w/w) with and without Cloisite 30B (C30B) (3 wt%) at absorbed doses of 1 and 10 kGy. The changes in the chemical structure, the molecular weight, the thermal, mechanical and barrier properties as well as the morphology were evaluated. The data showed that eBeam irradiation of PHBV/PLA blend leads to oxidation reactions involving ester groups in both neat PLA and neat PHBV resulting in the formation of hydroperoxides groups. The presence of C30B in the polymer blend has no influence on the nature of the degradation process. However, the good dispersion of C30B nanoparticles provides more stability to the molar mass and the thermal, mechanical and barrier properties of PHBV/PLA blend. At absorbed dose of 10 kGy, the irradiated samples are completely safe. Furthermore, ecotoxicity testing of both non irradiated and irradiated samples clearly showed no toxicity.
Keywords: PHBV; PLA; Cloisite 30B; Polymer blend; eBeam irradiation and degradation;
Decomposition mechanism of polyesters based on 2,5-furandicarboxylic acid and aliphatic diols with medium and long chain methylene groups by Zoe Terzopoulou; Vasilios Tsanaktsis; Maria Nerantzaki; George Z. Papageorgiou; Dimitrios N. Bikiaris (127-136).
Three different polyesters have been synthesized using 2,5-dimethylfuran dicarboxylate (DMFD) and diols with 5, 6 and 9 methylene groups, namely poly(pentylene 2,5-furanoate) (PPeF), poly(hexylene 2,5-furanoate) (PHF) and poly(nonylene 2,5-furanoate) (PNF), respectively. These polyesters that can be prepared from monomers derived from renewable resources were synthesized by melt polycondensation technique. Their structure was confirmed by 1H NMR spectroscopy. Thermal stability of polyesters was investigated using thermogravimetric analysis (TGA) and their decomposition mechanism was evaluated with Pyrolysis-Gas chromatography/Mass spectroscopy (Py–GC/MS). It was found that all polyesters decompose with a similar way and decomposition takes place mainly via β-hydrogen bond scission and less extensive with homolytic scission.
Keywords: Poly(alkylene 2,5-furan dicarboxylate) polyesters; Biobased polyesters; Thermal degradation; Decomposition mechanism;
Co-crystallization phenomena in biosynthesized isotactic poly[(R)-lactate-co-(R)-2-hydroxybutyrate]s with various lactate unit ratios by Taizo Kabe; Ken'ichiro Matsumoto; Satsuki Terai; Takaaki Hikima; Masaki Takata; Masahiro Miyake; Seiichi Taguchi; Tadahisa Iwata (137-144).
Poly[(R)-lactate-co-(R)-2-hydroxybutyrate], which is biosynthesized as a random co-polyester by microbial organisms, with various ratios of lactic acid (LA) to hydroxybutyrate monomers has been isothermally crystallized to investigate its thermal properties and crystal structure changes. Differential scanning calorimetry on the isothermally crystallized samples detected endothermic peaks due to the melting of the crystals at all LA unit ratios. Melting temperatures of the copolymers increased from ca. 107 °C–146 °C as the LA unit ratio increased. Glass transition temperatures also increased from 24 °C to 44 °C with increasing LA unit ratio. A melting temperature was observed even at LA unit ratios around 50%. Wide-angle X-ray measurements also revealed that co-crystallization occurred at all samples, including at LA unit ratios of ca. 50%. Despite of “jumping” phenomena many co-crystallizable random copolymers having, the lattice constants changed “linearly” from resembling poly[(R)-lactate] to poly[(R)-2-hydroxybutyrate] depending on the LA unit ratio. This unique co-crystallization behavior is discussed in detail.
Keywords: Microbial polyester; Co-crystallization; Random copolymer;
Effect of chitosan and catechin addition on the structural, thermal, mechanical and disintegration properties of plasticized electrospun PLA-PHB biocomposites by M.P. Arrieta; J. López; D. López; J.M. Kenny; L. Peponi (145-156).
In this paper the processing and properties of flexible electrospun biocomposites based on poly(lactic acid) (PLA) blended with 25 wt% of poly(hydroxybutyrate) (PHB), plasticized with 15 wt% of acetyl(tributyl citrate) (ATBC) and further loaded with 1 wt% and 5 wt% of chitosan (Ch) or catechin (Cat) microparticles are reported. Both fillers present a high content of hydroxyl groups on their surfaces. The morphological, structural, thermal and mechanical performance of electrospun biocomposites was investigated. The lowest amounts of Ch or Cat added (1 wt%) produced better interactions among PLA, PHB and plasticizer. Chitosan produced some bead defects in the fibers, which leads to a reduction of the mechanical performance on biocomposites. Catechin antioxidant effect improved the thermal stability of biocomposites and produced beads-free fibers with better mechanical performance. All biocomposites were disintegrated in composting conditions showing their possible applications as biodegradable films.
Keywords: PLA; PHB; Chitosan; Catechin; Plasticizer; Electrospinning;
Processing of edible films based on nanoreinforced gelatinized starch by Valentina Sessini; Marina P. Arrieta; José Maria Kenny; Laura Peponi (157-168).
Fully biobased edible films were prepared using native potato starch plasticized with glycerol and further reinforced with catechin (Cat) and starch nanocrystals (SNC) obtained by acidic hydrolysis from waxy maize starch granules. The thermal stability of starch nanocrystals obtained at different pH was studied, resulting on a decreasing in thermal stability at higher pH values. The X-ray diffraction patterns of the plasticized reinforced materials display complete destructuration of starch by solvent casting process. Plasticized films showed lower onset degradation temperatures than non-plasticized starch film. The reduction of the inter- and intra-molecular bonds interaction within the polymer matrix due to glycerol presence leads to a decrease of the thermal stability of the whole system. On the other hand, Cat and SNC produced an increase on the thermal stability of the bionanocomposites delaying the beginning of the thermal decomposition of starch/glycerol systems of about 20 °C. The mechanical performance was also improved in the ternary bionanocomposite edible films. All the edible films were fully disintegrated in compost conditions suggesting their possible applications as biodegradable edible films for packaging.
Keywords: Starch; Starch nanocrystals; Catechin; Edible films; Biodegradability;
New fully bio-based PLLA triblock copoly(ester urethane)s as potential candidates for soft tissue engineering by M. Fabbri; M. Soccio; M. Costa; N. Lotti; M. Gazzano; V. Siracusa; R. Gamberini; B. Rimini; A. Munari; L. García-Fernández; B. Vázquez-Lasa; J. San Román (169-180).
Novel fully bio-based poly(lactic acid) copoly(ester-urethane)s have been successfully synthesized. The new system is composed of a series of A-B-A triblock copolymers, where A, hard block, is poly(lactic acid) and B, soft block, is an ad hoc designed random aliphatic copolyester, poly(butylene succinate/azelate), characterized by high flexibility. Triblock units are joined by hexamethylene diisocyanate, known chain extender that allows the obtaining of polymers with high molecular weights. The samples synthesized were subjected to a detailed molecular, thermal, structural and mechanical characterization.The results obtained, show that copolymerization leads to better mechanical response with respect to poly(lactic) acid homopolymer. Moreover, the presence of the soft block in the main polymer chain facilitates the process of biodegradability. Nanoparticles of selected copolymers fabricated by using the nanoprecipitation method showed rounded morphology and average hydrodynamic diameters around 180 nm. Cellular behavior was assessed using human fibroblasts in vitro assays and results showed absence of cytotoxicity and a good cellular adhesion and proliferation on all the copolymer surfaces.
Keywords: Poly(lactic acid); Bio-based polymers; Triblock copolymers; Solid-state properties; Biocompatibility;
Characterization and enzymatic degradation study of poly(ε-caprolactone)-based biocomposites from almond agricultural by-products by Arantzazu Valdés; Octavio Fenollar; Ana Beltrán; Rafael Balart; Elena Fortunati; José María Kenny; María Carmen Garrigós (181-190).
Reinforced poly(ε-caprolactone) (PCL)/almond skin (AS) biocomposites were prepared by extrusion and injection moulding at different AS contents (0, 10, 20, 30 wt%) in order to revalorize this agricultural residue. AS particles were characterized by field emission scanning electron microscopy (FESEM), attenuated total reflectance infrared spectroscopy (ATR-FTIR) and thermogravimetric analysis (TGA). Hemicelluloses were the first compound thermally degraded (263 ± 2 °C) followed by cellulose (330 ± 5 °C) and lignin (401 ± 3 °C) with a remaining residue of 20% which was associated to the fibre content present in AS. Mechanical, morphological, thermal, and water absorption properties; and enzymatic degradation using Pseudomonas lipase were evaluated for the obtained biocomposites. A significant improvement in Young's modulus with a gain of 73% at 30 wt% AS loading was obtained compared to neat PCL. An increase in Shore D hardness and decrease in elongation at break and impact energy were also observed with increasing AS content caused by the reinforcement effect. Lower DSC thermal enthalpies and higher crystallinity were obtained for the biocomposites. Some decrease in thermal stability and higher water absorption values were also found with AS addition. Finally, the presence of AS retarded the enzymatic degradation of PCL, showing neat PCL higher weight loss after 25 days of study followed by PCL with 10 wt% AS.Display Omitted
Keywords: Agricultural by-products; Almond skin; Poly(ε-caprolactone); Reinforcement; Enzymatic degradation;
Novel biodegradable aliphatic copolyesters based on poly(butylene succinate) containing thioether-linkages for sustainable food packaging applications by Laura Genovese; Nadia Lotti; Massimo Gazzano; Valentina Siracusa; Marco Dalla Rosa; Andrea Munari (191-201).
Poly(butylene succinate) (PBS) based random copolyesters containing thioether-linkages were synthesized by melt polycondensation, and characterized from the molecular and thermo-mechanical point of view. Permeability to O2 and CO2 gases and biodegradation rate in compost have been also evaluated. The synthesized semicrystalline copolymers have proved to be thermally stable and characterized by PBS crystal phase. The main effect of copolymerization was a lowering in the crystallinity degree and a decrease of T m with respect to homopolymer. The dependence of T m on composition was described by Baur's equation. Slightly different surface hydrophilicity has been also displayed. Mechanical properties and the biodegradation rate turned out to be deeply influenced by the copolymers composition, in particular the higher the thiodiethylene glycol mol% the higher the elongation at break and the biodegradation extent. It is worth mentioning that the synthesized copolymers displayed better barrier properties to both studied gases with respect to commercial Poly(lactic acid).
Keywords: Poly(butylene succinate); Random copolymers; Solid-state properties; Biodegradable polymers;
Biodegradable polyesters based on star-shaped lactic acid oligomers by A. Frydrych; Z. Florjańczyk; M. Charazińska; M. Kąkol (202-212).
Catalytic polymerization of ε-caprolactone and copolymerization of maleic anhydride and propylene or ethylene oxide carried out in the presence of star-shaped L-lactic acid oligomers were studied. The analysis of the reaction products by means of GPC, MALDI ToF and 1H NMR show that the applied processes allowed to combine oligomers with polyesters produced by ring opening polymerization and obtain a new type of lactic acid copolymers of relative molar masses in the range 15–60 kg/mol. DSC studies revealed that the formed polyesters segments were fully or partially miscible with poly(lactic acid) core causing the reduction of its glass transition temperature. Selected copolymers were subjected to enzymatic degradation, which indicated that all of these compounds underwent partial decomposition. An analysis of weight loss showed, however, that the degradation occurred more slowly than in the case of poly(lactic acid) of similar molar masses and chain architecture.
Keywords: Lactic acid; Copolymers; Biodegradable polyesters; Ring opening polymerization;
Cardanol derivatives as innovative bio-plasticizers for poly-(lactic acid) by Antonio Greco; Alfonso Maffezzoli (213-219).
This work is aimed to study the suitability of a bio based compound, cardanol acetate (CA), as plasticizing agent of poly(lactic acid) (PLA). Compared to other natural derived plasticizers, cardanol acetate is not obtained from food crops but as a by product of cashew nut extraction. In addition, the cardanol derived plasticizers can be obtained by the use of non toxic and low environmental impact reagents. The plasticizing effectiveness of cardanol acetate was confirmed by the decrease of the glass transition temperature and flexural modulus, which were comparable to those obtained by the use of conventional oil based plasticizers, such as diethylhexyl phthalate (DEHP). In addition, calorimetric analysis revealed that the addition of the plasticizer, both cardanol derived and phthalate, involves a significant increase of the crystallization kinetics. An analysis of the flexural strength and deformation at break indicated that the increase of the crystallization kinetics has more dramatic effects compared to the decrease of the glass transition, particularly at low plasticizer content, finally leading to a decrease of the ductility. At higher plasticizer content, an increase of the ductility is observed, and PLA plasticized by 10% of CA showed a significant higher deformation at break than PLA plasticized by DEHP. In addition, plasticizer migration tests showed a lower weight loss of PLA plasticized by CA compared to DEHP plasticized PLA, which indicates the potential higher stability of properties of the cardanol derived plasticizer.
Keywords: Cardanol; Plasticizer; Poly(lactic acid); Durability;
Effect of SWCNT introduction in random copolymers on material properties and fibroblast long term culture stability by Ilaria Armentano; Elena Fortunati; Matteo Gigli; Francesca Luzi; Rosa Trotta; Ilaria Bicchi; Michelina Soccio; Nadia Lotti; Andrea Munari; Sabata Martino; Luigi Torre; Josè Maria Kenny (220-230).
Polymeric nanostructured biomaterials can be used as synthetic cell interfaces with important applications in the study and control of cellular processes. Herein, we developed multifunctional nanocomposites based on synthesized biodegradable and biocompatible copolyesters of poly(butylene 1,4-trans-cyclohexanedicarboxylate) (PBCE) containing ether–linkages, and single walled carbon nanotubes (SWCNTs), employed as functional phase. Surface, thermal and mechanical characterization of the polymer and nanocomposite films were performed. The influences of AC conductivity and interfacial polarization on dielectric relaxation process, as well as the correlation between the dielectric behaviors and SWCNT content were investigated by measuring the dielectric properties. The effect of SWCNT incorporation, and amount of ether-oxygen atoms was also investigated in terms of fibroblast long-term culture stability, by performing adhesion and proliferation studies of cells seeded on the biomaterial surface, at different time points. Results showed that polymeric conductive nanocomposites were successfully developed with a low percolation threshold, and SWCNT presence maintained the polymer thermal degradation behavior. Moreover, the culture of primary fibroblasts indicated that these advanced functional materials are biocompatible and guarantee the cell adhesion and growth, being suitable substrates for regenerative medicine applications. Finally, their versatile structure and chemical properties may provide a robust platform to gain insight into cell–biomaterial interactions, being an important step towards the better understanding and control of cell interactions with nanomaterials.
Keywords: SWCNT; Ether-linkages; Polyesters; Biocompatibility;