Complex phase behavior and state of miscibility in Poly(ethylene glycol)/Poly(l‐lactide‐co‐ε‐caprolactone) Blends

A miscibility and phase behavior study was conducted on poly(ethylene glycol) (PEG)/poly(l ‐lactide‐ε‐caprolactone) (PLA‐co‐CL) blends. A single glass transition evolution was determined by differential scanning calorimetry initially suggesting a miscible system; however, the unusual T_g bias and subsequent morphological study conducted by polarized light optical microscopy (PLOM) and atomic force microscopy (AFM) evidenced a phase separated system for the whole range of blend compositions. PEG spherulites were found in all blends except for the PEG/PLA‐co‐CL 20/80 composition, with no interference of the comonomer in the melting point of PEG (T_m = 64 °C) and only a small one in crystallinity fraction (X_c = 80% vs. 70%). However, a clear continuous decrease in PEG spherulites growth rate (G) with increasing PLA‐co‐CL content was determined in the blends isothermally crystallized at 37 °C, G being 37 µm/min for the neat PEG and 12 µm/min for the 20 wt % PLA‐co‐CL blend. The kinetics interference in crystal growth rate of PEG suggests a diluting effect of the PLA‐co‐CL in the blends; further, PLOM and AFM provided unequivocal evidence of the interfering effect of PLA‐co‐CL on PEG crystal morphology, demonstrating imperfect crystallization in blends with interfibrillar location of the diluting amorphous component. Significantly, AFM images provided also evidence of amorphous phase separation between PEG and PLA‐co‐CL. A true T_g vs. composition diagram is proposed on the basis of the AFM analysis for phase separated PEG/PLA‐co‐CL blends revealing the existence of a second PLA‐co‐CL rich phase. According to the partial miscibility established by AFM analysis, PEG and PLA‐co‐CL rich phases, depending on blend composition, contain respectively an amount of the minority component leading to a system presenting, for every composition, two T_g's that are different of those of pure components. © 2013 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014 , 52, 111–121     

Development of new approach based on Raman spectroscopy to study the dispersion of expanded graphite in poly(lactide)

A new approach has been developed to study the dispersion/delamination of expanded graphite (EG) in poly(lactide) (PLA) by using Raman spectroscopy. This technique is more sensitive and therefore fully complementary to more standard dispersion characterization techniques like SEM, TEM and X-ray diffraction. The incorporation of EG into PLA was carried out by a twin-screw micro-extruder. The effects of the dispersion and delamination of EG on the thermal and thermo-mechanical properties of polylactide-EG nanocomposites were investigated. In contrast to the standard techniques, Raman spectroscopy was able to show a partial exfoliation, which could therefore explain the slight improvement of the PLA-EG thermal and thermo-mechanical properties.     

Poly Lactic Acid (PLA) Nanocomposites: Effect of Inorganic Nanoparticles Reinforcement on Its Performance and Food Packaging Applications

Poly lactic acid (PLA) is a compostable, as well as recyclable, sustainable, versatile and environmentally friendly alternative, because the monomer of PLA-lactide (LA) is extracted from natural sources. PLA’s techno-functional properties are fairly similar to fossil-based polymers; however, in pristine state, its brittleness and delicacy during processing pose challenges to its potential exploitation in diverse food packaging applications. PLA is, therefore, re-engineered to improve its thermal, rheological, barrier and mechanical properties through nanoparticle (NP) reinforcement. This review summarises the studies on PLA-based nanocomposites (PLA NCs) developed by reinforcing inorganic metal/metallic oxide, graphite and silica-based nanoparticles (NPs) that exhibit remarkable improvement in terms of storage modulus, tensile strength, crystallinity, glass transition temperature (Tg) value, antimicrobial property and a decrease in water vapour and oxygen permeability when compared with the pristine PLA films. This review has also discussed the regulations around the use of metal oxide-based NPs in food packaging, PLA NC biodegradability and their applications in food systems. The industrial acceptance of NCs shows highly promising perspectives for the replacement of traditional petrochemical-based polymers currently being used for food packaging.     

The Cytotoxic Effect of Apis mellifera Venom with a Synergistic Potential of Its Two Main Components—Melittin and PLA2—On Colon Cancer HCT116 Cell Lines

Colon carcinogenesis is ranked second globally among human diseases after cardiovascular failures. Bee venom (BV) has been shown to possess in vitro anticancer effects against several types of cancer cells. The two main biopeptides of Apis mellifera BV, namely, melittin (MEL) and phospholipase A2 (PLA2), are suspected to be the biomolecules responsible for the anticancer activity. The present work aims to evaluate the cytotoxic effect of the A. mellifera venom on human colon carcinoma cells (HCT116), and to assess the synergistic effect of MEL and PLA2 on these cells. After analyzing, through high-pressure liquid chromatography, the proportions of MEL and PLA2 on BV, we have established a cell viability assay to evaluate the effect of BV, MEL, PLA2, and a mixture of MEL and PLA2 on the HCT116 cells. Results obtained showed a strong cytotoxicity effect induced by the A. mellifera venom and to a lower extent MEL or PLA2 alone. Remarkably, when MEL and PLA2 were added together, their cytotoxic effect was greatly improved, suggesting a synergistic activity on HCT116 cells. These findings confirm the cytotoxic effect of the A. mellifera venom and highlight the presence of synergistic potential activities between MEL and PLA2, possibly inducing membrane disruption of HCT116 cancer cells. Altogether, these results could serve as a basis for the development of new anticancer treatments.     

Determination of Crystallization and Melting Behaviour of Poly-lactic Acid and Polypropyleneblends as a Food Packaging Materials by Differential Scanning Calorimeter

The food packaging materials commonly used is made from polymers synthetic base on petroleum derivatives. However, the use of synthetic polymers has negative impacts on the environment, because it is difficult to degrade naturally either by biotic or abiotic process. This is a problem for the environment and therefore it needs to do the assessment of the technology to reduce the degree of difficulty on its degradation or to find a new material that can be degradable naturally. One of the most important properties of food packaging materials is the polymer crystallinity. This refers to the overall level of crystalline component in relationship to its amorphous component. It is directly related to many of key properties exhibited by a semi-crystalline polymer including brittleness, toughness, stiffness or modulus, optical clarity, creep or cold flow, barrier resistance and long-term stability. Thus, in this study, PP blends with the PLA and meltsat 250^oCfor 4 hours, and investigates their crystallization and melting behavior using DSC at cooling rate of 10 and 40^oC/min. The results show that base on their thermograms, with increasing the cooling rate will decreasing the crystallinity or increasing amorphous area underthe peaks.     

New Polylactic Acid Composites for Packaging Applications: Mechanical Properties,Thermal Behavior,and Antimicrobial Activity

The interest in antimicrobial packaging materials based on polylactic acid (PLA) polymers has increased due to the need to improve food safety and environment quality and also to find alternatives to synthetic polymers made from petrochemicals. PLA films by addition of different fillers (grape wastes and celery fibers) were obtained. The mechanical, thermal, surface, and antimicrobial properties of the films were evaluated. The incorporation of inexpensive fillers into the PLA matrix could reduce costs and the studied formulations offer approaches to realize composites with high performances and antimicrobial response, suitable for film food-active packaging materials, especially by use of grape wastes.     

Composites of Wood and Biodegradable Thermoplastics: A Review

This paper is an overview of current understanding in the areas of composites made from biodegradable thermoplastics and wood fillers. The review finds that the composite properties depend on the type of wood filler, the choice of polymer matrix, the wood filler content, the compatibilization technique used and the processing parameters. The extent of interfacial adhesion and the filler morphology are identified as the underlying factors that control the composite properties. Future research needs are identified, including establishment of fundamental relationships between quantified interfacial adhesion and end-use properties and advanced modelling of biodegradation processes.     

Poly(lactic acid)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer/sepiolite nanocomposites: Investigation of thermo‐mechanical and morphological properties

In this study, sepiolite nanoclay is used as reinforcing agent for poly(lactic acid) (PLA)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer (SEBS‐g‐MA) 90/10 (w/w) blend. Effects of sepiolite on thermal behavior, morphology, and thermomechanical properties of PLA/SEBS‐g‐MA blend were investigated. Differential scanning calorimetry results showed 7% improvement in crystallinity at 0.5 wt% of sepiolite. The nanocomposite exhibited approximately 36% increase in the tensile modulus and 17% increase in toughness as compared with the blend matrix at 0.5 and 2.5 wt% of sepiolite respectively. Field emission scanning electron microscopy and transmission electron microscopy images exhibited sepiolite‐induced morphological changes and dispersion of sepiolite in both PLA and SEBS‐g‐MA phases. Dynamic mechanical analysis and wide angle X‐ray diffraction present evidences in support of the reinforcing nature of sepiolite and phase interaction between the filler and the matrix. This study confirms that sepiolite can improve tensile modulus and toughness of PLA/SEBS‐g‐MA blend.     

Properties of acrylonitrile butadiene rubber (NBR)/poly(lactic acid) (PLA) blends and their foams

Abstract

Thermoplastic elastomers and their foams were prepared by blending elastomeric acrylonitrile butadiene rubber (NBR) and rigid poly(lactic acid) (PLA) with various PLA compositions ranging between 0 and 40%. The thermal and mechanical properties and the morphologies of the blends with various PLA contents were investigated through universal testing machine, differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscope analysis. The rheological properties during gel formation were in situ monitored through the evolution of torque with curing time. Furthermore, the microcellular structures and physical properties of the NBR/PLA foams prepared using organic blowing agents were studied. The NBR/PLA blends showed a two-phase morphology made of a continuous NBR matrix and micron or submicron nodules and the tensile strength and modulus; also, hardness of the NBR/PLA blends increased with the increase of the added PLA content. While the foamed samples exhibited a similar cell structure and foaming ratio to that of the pure NBR, the cell formation was considerably reduced as the added PLA content exceeded 30%. We conclude that the mechanical properties of NBR thermoplastic elastomer as well as its foams can be controlled by a judicious introduction of rigid and biodegradable PLA.     

Surface functionalized waste-silk fabric engineered with polylactic acid & activated charcoal for oil/solvent recovery from oily wastewater

The present study reports using waste silk fabric functionalized using Polylactic acid (PLA) and Activated charcoal for oil/solvent recovery from simulated seawater (3.5% NaCl-based water). An average of 91% separation was visible in the functionalized waste silk fabric with an efficiency up to 20 cycles towards petroleum oils/solvents from simulated seawater. Further, the functionalized waste fabric showed hydrophobic properties with a water-based contact angle of 105° and oil/solvent absorption towards petroleum oils and organic solvent, with a surface free energy of 52.46 mN m⁻¹. The functionalized waste silk also showed permeation flux of 658, 386, and 993 L m⁻² h⁻¹, for Petrol, Diesel, and n-Hexane, respectively. The results show that PLA/Activated-charcoal engineered waste silk can be effectively applied for practical oil/solvent recovery from simulated seawater. Utilizing waste silk fabric further supports in reducing the global carbon footprints as silk does not emit and/-or produce carbon dioxide due to its green origin and generating the circular economy approach.