Analyzing the interactions and miscibility of silk fibroin/mucin blends

Mucin, a glycoprotein with viscoelastic properties, and silk fibroin, a protein excreted from silkworms with properties of thermal and mechanical resistance, have been probed as building blocks in the design of biomaterials. Aiming to evaluate the interaction and miscibility between mucin and fibroin, we synthesized silk fibroin and mucin (SF/MU) blends for biomedical applications. The morphological analysis of the SF/MU blends showed the presence of two phases, suggesting a partial miscibility between the polymers. The degradation temperature of the SF/MU blends increased with an increase in the silk fibroin content, indicating that silk fibroin contributed to the thermal stability of the blends. The glass transition temperature of the SF/MU blends lay between the values of the pure polymers. The Fourier-transform infrared spectroscopy results pointed out that the interaction between fibroin and mucin occurred between the amine group of silk fibroin and mucin carboxyl and hydroxyl groups. The outcomes of this work provided essential information on the miscibility of the SF/MU blends. These findings will be critical for further studies with fibroin and mucin-based biomaterials, especially in mucoadhesive systems and wound healing applications.     

Compression molding and melt‐spinning of the blends of poly(lactic acid) and poly(butylene succinate‐co‐adipate)

Poly(lactic acid) (PLA) is a biobased polymer made from biomass having high mechanical properties for engineering materials applications. However, PLA has certain limited properties such as its brittleness and low heat distortion temperature. Thus, the aim of this study is to improve toughness of PLA by blending with poly(butylene succinate‐co‐adipate) (PBSA), the biodegradable polymer having high toughness. Polymer blends of PLA and PBSA were prepared using a twin screw extruder. The melt rheology and the thermal property of the blends were examined. Further the blends were fabricated into compression molded parts and melt‐spun fiber and were subjected to tensile and impact tests. When the PBSA content was low, PBSA phase was finely dispersed in the PLA matrix. On the other hand, when the PBSA content was high, this minor phase dispersed as a large droplet. Mechanical properties of the compression molded parts were affected by the dispersion state of PBSA minor component in PLA matrix. Impact strength of the compression molded parts was also improved by the addition of soft PBSA. The improvement was pronounced when the PBSA phase was finely dispersed in PLA matrix. However, the mechanical property of the blend fibers was affected by the postdrawing condition as well as the PBSA content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41856.     

Preparation of hybrid PU/PCL fibers from steviol glycosides via electrospinning as a potential wound dressing materials

In this study, the synthesis and application of biocompatible steviol glycosides based polyurethane/poly (ε-caprolactone) (PU/PCL) fibers was performed by electrospinning as a potential wound dressing materials that can be used for the closure of nonhealing wounds. During electrospinning, steviol glycoside-based polyurethane structures were used in blend formation with poly (ε-caprolactone) for easy producibility. Steviol glycosides are a natural abundant and easily accessible source as the main component of the wound dressing material due to their free hydroxyl groups, high biocompatibility, and hydrophilicity. The structure of steviol glycosides is composed of saccharide units and the free OH groups. Thus, steviol glycosides act as a crosslinker within the polyurethane structure and provides mechanical strength. For the production of steviol glycosides based PU/PCL fibers first, the steviol glycosides as a monomer were isolated from the stevia rebudiana. Then, polyurethane structures containing stevia glycoside were synthesized with hexamethylene diisocyanate, lactose and PEG-200 by solution polymerization technique. PCL was added to the prepared polyurethanes in a ratio of 1:2 and formation of nanofiber structure. The prepared wound dressing material was characterized by Fourier transform infrared, atomic force microscopy, and scanning electron microscope techniques. Swelling degree, water content and oxygen permeability assay of the steviol glycosides based PU/PCL wound dressing material was determined. In biocompatibility test, cell viability value of PU/PCL fibrous materials in indirect cytotoxicity test was determined as 86.9% and cell adhesion on hybrid PU/PCL fibers was showed as morphological. In accordance with this target, the steviol glycosides based PU/PCL wound dressing material can be produced easily and low cost. As a result, the wound dressing materials obtained with their high biocompatibility and low costs will be an effective and fast method for the healing of open wounds of diabetics.     

Keratin–polyhydroxyalkanoate melt‐compounded composites with improved barrier properties of interest in food packaging applications

Sustainable biocomposite materials based on the combination of polyhydroxyalkanoates with a keratin additive derived from poultry feathers were successfully developed via melt compounding. Suitable dispersions for low loadings of the additive in the biopolymeric matrix were achieved by the melt‐mixing technique. A good physical interaction between the polymeric matrix and the additive was observed by scanning electron microscopy (SEM). Reductions in water, limonene, and oxygen permeability of the pure polymer to less than a half of its initial value for the composite containing 1 wt % of keratin additive were achieved. This composition was also found to exhibit optimum mechanical performance. As a result, these materials offer significant potential in fully renewable packaging applications based on polyhydroxyalkanoates with enhanced barrier performance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39947.     

Fabrication and improved performance of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) for packaging by addition of high molecular weight natural rubber

The packaging industry is searching for alternative materials to attain environmental sustainability. Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate (PHBV) is a semicrystalline polymer that meets this sustainability goal since it is bioderived and biodegradable. However, its brittle nature and relatively high water permeation and transmission rates make it unsuitable for packaging applications. In addition, PHBV has poor mechanical, thermal, and rheological properties above 160 °C, limiting its use in cast sheets and thermo‐formed packaging applications. To improve these properties, new blends of PHBV with high molecular weight natural rubber at 5, 10, 15, and 25% by weight were fabricated, and physico‐chemical properties of the blends were characterized. The rubber in the blends aided in the following: increased thermal stability since the complex viscosities of the blends were improved by one log over pure PHBV at 170 °C, created more uniform melting peaks attesting to improved homogeneity, decreased water permeation to a level similar to that of traditional thermoplastics; increased the elongation at break, and stabilized the Young's modulus. Therefore, these blends can potentially be used in‐place of traditional, petroleum‐based thermoplastics in cast sheets and thermoforms. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43937.     

Enhanced impact strength of compatibilized poly(lactic acid)/polyamide 11 blends by a crosslinking agent

Maleated poly(lactic acid) (PLA-g-MA) was prepared through melt grafting of maleic anhydride onto a PLA backbone with the aid of a radical initiator. PLA-g-MA thus formed was incorporated into PLA/polyamide 11 (PA11) blends as a reactive compatibilizer. By morphological observation, it was assessed that PLA-g-MA lowered the interfacial energy and strengthened the interface between PLA and PA11. However, the compatibilized PLA/PA11 blends did not show significant improvement of impact strength compared with noncompatibilized PLA/PA11 blends. Measurements of the molecular weight and impact strength of PLAs compounded with various amounts of radical initiators revealed that decreased molecular weight of PLA by the radical initiator used for the preparation of PLA-g-MA is responsible for this unexpected result. To compensate the decrease of the molecular weight, a crosslinking agent was incorporated in the preparation step of PLA-g-MA. It was found that the crosslinking agent is effective in preventing the molecular weight reduction. As a result, the impact strength of the PLA/PA11 blend was enhanced to a great extent by the PLA-g-MA prepared with the crosslinking agent.     

Degradation studies during water absorption,aerobic biodegradation,and soil burial of biobased thermoplastic starch from agricultural waste/polypropylene blends

Thermoplastic starch (TPS) from agricultural waste consisting of different amylose/amylopectin ratios was blended with polypropylene (PP) for degradation studies. The agricultural waste material was obtained from seeds and tubers with low starch contents of ～50%. Non‐Fickian behavior was observed for the water absorption test, and water uptake increased with increases in amylopectin content. The biodegradation was assessed based on the extent of carbon conversion, and was found to be dependent on the water absorption behavior and molecular structure of the starch component. Outdoor soil burial showed greater weight loss and deterioration in tensile properties compared to indoor soil burial. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Statistical optimization of compatibilized blends of poly(lactic acid) and acrylonitrile butadiene styrene

A mixture design of experiment and subsequent regression analysis was used to study the effects of two additives on blends of poly(lactic acid) (PLA) and acrylonitrile butadiene styrene (ABS). Statistical analysis was used to find a blend with a balance of high toughness, strength, and stiffness. The blends were prepared by lab scale reactive extrusion and injection molding. Least‐square regression models of statistically significant effects were built by analysis of variance (ANOVA). Using these models, optimization studies were used to study the predicted maximum values of each measurement criteria. Very large increases were seen in the measured responses with relatively small changes in additive content. Compared to the neat blend without additives, the impact strength was increased by over 600%, the elongation at break was increased by over 1000%, the tensile strength increased by 11%, and the tensile modulus increased by over 7%. Surprisingly, the composite optimization, which included all measured criteria, occurred at a point that allowed all four criteria values to remain very close to their individual maximums. The result is a partially biobased blend that does not sacrifice strength or stiffness to achieve very high toughness. © 2016 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44516.     

Natural weathering studies of biobased thermoplastic starch from agricultural waste/polypropylene blends

Thermoplastic starch (TPS) obtained from agricultural waste was blended with polypropylene (PP) for natural weathering studies. The agricultural waste material was obtained from seeds and tubers with a starch content of approximately 50%. Commercial‐grade TPS and native tapioca‐based TPS were also prepared for comparison. The biobased TPS/PP extruded sheets were exposed to natural weathering for six months and their deterioration in weight, tensile properties, thermal properties, and relative molecular weight were monitored. SEM micrographs revealed the formation of surface cracking and the presence of microorganisms. FTIR spectrum indicated an increase in the carbonyl index over time as a result of the formation of degradation products. TPS/PP blends made from agricultural waste showed a better resistance to natural weathering compared to the other high starch formulation. The higher starch content in the blend system encouraged the rapid degradation process due to the combined effect of UV radiation with oxidation, moisture, temperature, and microbial attack. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Extruded versus solvent cast blends of poly(vinyl alcohol‐co‐ethylene) and biopolymers isolated from municipal biowaste

Water‐soluble biopolymers (SBO) were isolated from the alkaline hydrolysate of two materials sampled from an urban waste treatment plant; that is, an anaerobic fermentation digestate and a compost. The digestate biopolymers contained more lipophilic and aliphatic C, and less acidic functional groups than the compost biopolymers. The SBO were blended with poly (vinyl alcohol‐co‐ethylene), hereinafter EVOH. The blends were extruded and characterized by FTIR spectroscopy, size exclusion chromatography (SEC)– multi angle static light scattering (MALS) analysis, and for their thermal, rheological, and mechanical properties. The blends behavior depended on the type of SBO and its relative content. Evidence was obtained for a condensation reaction occurring between the EVOH and SBO. The best results were obtained with the blends containing up to 10% SBO isolated from the biowaste anaerobic digestate. Compared with the neat EVOH, these blends exhibited lower melt viscosity and no significant or great difference in mechanical properties. The results on the extrudates, compared with those previously obtained on the same blends obtained by solvent casting, indicate that the blends properties depend strongly also on the processing technology. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43009.     

Miscible blends of biobased poly(lactide) with poly(methyl methacrylate): Effects of chopped glass fiber incorporation

Poly(lactide) (PLA) and poly(methyl methacrylate) (PMMA) are melt compounded with chopped glass fiber using laboratory scale twin‐screw extrusion. Physical properties are examined using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), tensile testing, impact testing, X‐ray computed tomography (CT) scanning, and field emission scanning electron microscopy (FE‐SEM). Molecular weight is determined using gel permeation chromatography (GPC). Miscibility of the blends is implied by the presence of a single glass transition temperature and homogeneous morphology. PLA/PMMA blends tend to show positive deviations from a simple linear mixing rule in their mechanical properties (e.g., tensile toughness, modulus, and stress at break). The addition of 40 wt % glass fiber to the system dramatically increases physical properties. Across all blend compositions, the tensile modulus increases from roughly 3 GPa to roughly 10 GPa. Estimated heat distortion temperatures (HDTs) are also greatly enhanced; the pure PLA sample HDT increases from 75 °C to 135 °C. Fiber filled polymer blends represent a sustainable class of earth abundant materials which should prove useful across a range of applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44868.     

Ultra-flexible PLA-based blends for the manufacturing of biodegradable tamper-evident screw caps by injection molding

Mono-material in the manufacturing of oil-based plastic bottles has been so far not considered because of the poor flexibility of polyethylene terephthalate (PET). The undercuts of PET caps (i.e., the threads of the screw caps) would be torn-off during the ejection step of the injection/compression molding processes that are commonly used to fabricate them. In this respect, the present work deals with the design and development of innovative biodegradable polyester-based blends with high flexibility, intended for the manufacturing of screw-cap, being this element the most critical in the implementation of the complete bottle. The blend is based on polylactic acid and it is tailored for injection molding of tamper-evident screw plastic caps by the addition of another biodegradable polyester, that is, polybutylene adipate-co-terephthalate. The effect of the addition of a barrier agent, polyvinyl alcohol, on the overall behavior of the blends was also studied in the perspective of the implementation of caps featuring barrier properties against water vapor and oxygen. The same material could be, however, easily tailored for the fabrication of the bottle body and printed label to get to the mono-material bottle. Twin-screw corotating extrusion of the compound, injection molding of the plastic material for the fabrication of the screw caps, and evaluation of the thermophysical and mechanical properties of the screw caps are hereinafter discussed. The biodegradable polyester-based blends are found to be suitable for injection molding of the tamper-evident screw caps, exhibiting adequate flexibility during ejection from the mold. The screw caps can also boast appreciable mechanical strength and impact resistance as well as good thermal stability.     

Hydrolytic stability of polylactide and poly(methyl methacrylate) blends

The hydrolytic stability of polylactide/poly(methyl methacrylate) (PLA/PMMA) blends prepared using a twin‐screw extrusion process was investigated. The effects of hydrolysis were monitored in neutral and alkaline media at 80 °C by tracking the changes in molecular weight distribution, weight loss, water uptake, and crystallization behavior. The crystallinity of PLA in blends prior to hydrolysis was shown to be largely hindered by the presence of PMMA. However, PLA recrystallized rapidly during hydrolysis. The PMMA in the blends was shown to provide increased hydrolytic and structural stability to the blends. In the neutral medium, the presence of PMMA delayed and reduced the weight loss but did not significantly affect PLA degradation kinetics. On the other hand, in the alkaline medium, the weight loss rate was strongly decreased in presence of PMMA and the kinetics of degradation was shown to be depend on PMMA content. The microstructure of these blends throughout the hydrolysis process was also examined by scanning electron microscopy. A porous structure, with interconnected pores in the 20–50 nm range, was developed due to the selective removal of PLA. Based on these morphological observations, erosion mechanism of PLA/PMMA blends was discussed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45991.     

Effect of two different plasticizers on the properties of poly(3‐hydroxybutyrate) binary and ternary blends

Plasticized poly(3‐hydroxybutyrate) (PHB) films were obtained by solvent casting. The effects of two different additives on several properties of PHB have been examined, utilizing tributyrin and poly[di(ethyleneglycol) adipate] (A). Based on changes in the glass transition temperature (T_g) and cold crystallization temperature of host PHB, the two components are miscible with PHB and they can act as plasticizers. Binary and ternary blends were obtained by adding both plasticizers separately or together, respectively. The effect of plasticizer addition on the optical transparency, water vapor permeability, and tensile properties of the films was studied. It was found that the blends remain transparent and water vapor permeability was maintained constant until a 20 wt % of plasticizer content. Plasticizing effect was corroborated and it depended on the plasticizer percentage. Binary blends had an increased plasticity, in concordance with T_g diminution of PHB. Although ternary blends presented T_g diminution, mechanical properties were not improved probaby due to strong interactions between plasticizers. Finally, binary and ternary blends presented enhanced properties, causing an increment on processability. A correct knowledge between the formulation of the film and the role played by each component could allow getting custom films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46016.     

Development and characterization of a poly (vinyl alcohol) and sodium alginate blend foam for wound dressing loaded with propolis and all-trans retinoic acid

Propolis is a complex mixture of phytochemicals, with antibacterial, anti-inflammatory, and healing properties. All-trans retinoic acid is implicated in wound healing by stimulating angiogenesis, cell recruitment, extracellular matrix deposition, and reepithelization. The incorporation of both agents to a polymeric wound dressing composed of poly (vinyl alcohol) and sodium alginate may result in improved healing allied to controlled release, fluid uptake, and wound protection. In the present work, we have physically characterized this wound dressing and analyzed its release kinetics. The anti-inflammatory capacity was assayed. SEM images showed a highly porous structure with a diverse morphology. FTIR spectra displayed a highly cross-linked structure with both polymers connected by hydrogen bonds and acetal bridges. The wound dressings were able to retain great volumes of PBS. Propolis and vitamin A releasing behavior were maintained for 6 h. The concentrations of the biologically active substances were capable of promoting anti-inflammatory action in an erythrocyte membrane stabilization model. The wound dressings obtained here showed adequate physical properties. The fabrication process did not affect the anti-inflammatory capacity. Further tests are needed to ensure the biocompatibility and to assess other biological activities of the therapeutic agents.     

Highly toughened polylactide by renewable Eucommia ulmoides gum

Polylactide (PLA) derived from natural sources has attracted increasing interest and has provided a promising alternative to traditional plastics derived from petroleum sources. With no loss of environmental friendly features, PLA was highly toughened by Eucommia ulmoides gum (EUG) derived from Eucommia ulmoides oliv. The dynamic mechanical analysis, scanning electron microscopy (SEM), and differential scanning calorimetry results show that the PLA–EUG blends were immiscible systems. SEM micrographs revealed that EUG particles were well dispersed in the PLA matrix with number‐average particle diameters of 2–4 μm. The mechanical properties indicated that the tensile strength decreased with increasing EUG contents, but the elongation at break and the impact strength were enhanced. The notched impact strength of the blends improved by 5.9‐fold compared to that of neat PLA. The PLA–EUG blends exhibited distinct shear‐thinning behavior; this indicated good processability, and the storage modulus and loss modulus of the PLA–EUG blends increased with EUG content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46017.     

Films made from polyethylene‐co‐acrylic acid and soluble biopolymers sourced from agricultural and municipal biowaste

Blends were obtained from polyethylene‐co‐acrylic acid (PEAA) with 248 kDa molecular weight and two water soluble biopolymers isolated from the hydrolysate of postharvest tomato plant and urban biowaste compost. The two hydrolysates were constituted respectively from a polysaccharide (SP) with 27 kDa molecular weight and a lignin‐like polymer (LP) with 75 kDa molecular weight containing aliphatic and aromatic C moieties substituted by carboxyl, hydroxyl, and amino groups. Evidence was obtained for reactions occurring between the biopolymers and the synthetic polymer leading to new polymers with 151 to 1243 kDa molecular weights. The thermal and mechanical properties of the blends were studied. Compared with neat PEAA, the PEAA‐LP blends containing 5 to 10% LP exhibited 2 to 5× higher molecular weights, 10 to 50% lower crystallinity, 2 to 6× higher Young's modulus, over 3× higher stress at yield point and somewhat lower strain at break (55–280% vs. over 300%). On the contrary the PEAA‐SP blends exhibited 6 to 13% lower crystallinity and the same mechanical properties as neat PEAA. The results offer scope for investigating biopolymers sourced from other biowastes to understand more the reasons of the observed effects and exploit their full potential to modify or to replace synthetic polymers. Perspectives of economic and environmental benefits are discussed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41909.     

Evaluating PE/PLA interfacial tension using ternary immiscible polymer blends

Blending with ethylene-based flexible polymers such as polyethylene (PE) is one of the strategies to toughen poly(lactic acid) (PLA), an inherently brittle biodegradable plastic enjoying growing demands worldwide. Interfacial tension plays a crucial role in blend formulation. Yet several literature reports on the PE/PLA interfacial tension contradict each other, giving ~5 mN/m and ~11 mN/m. In this work, we demonstrate that the PE/PLA interfacial tension is at least 9 mN/m. We use a cocontinuous PE/polystyrene (PS)/PLA ternary blend. Scanning electron microscopy (SEM) revealed complete wetting morphology with PS phase separating PE and PLA phases in the ternary blend. In addition, the complete wetting behavior was maintained at a PS volume fraction as low as 3%. This morphology together with the Harkins equation, indicate that the PE/PLA interfacial tension is higher than 10.5 ± 1.4 mN/m at 180°C.     

Design of an antibacterial gelatin based on a covalent protein–protein coupling

An antibacterial peptide (AMP), i.e., nisin, was covalently bound to gelatin through a protein–protein coupling. Various reaction conditions were tested to study and optimize parameters of grafting e.g., orientation and density of AMP, which could impact the final antibacterial activity of the modified biopolymer. Modification was investigated by Fourier transform infrared (FT‐IR) spectroscopy and zeta potential. The antibacterial activity of the nisin‐enriched gelatin was evaluated against two staphylococci bacterial strains, i.e., Staphylococus epidermidis and Staphylococcus aureus. A higher activity was found for gelatin modified at pH = 7.4 revealing an influence of the nisin orientation on the protein antibacterial property. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41825.     

Effect of the melt‐mixing condition on the physical property of poly(l‐lactic acid)/poly(d‐lactic acid) blends

The effect of the mixing condition in a mill‐type mixer on the thermal property and the crystal formation of the poly(l ‐lactide)/poly(d ‐lactide) blends is investigated. The blends melt‐mixed at 200 and 210 °C under application of a high shear flow tend to show a single melting peak of the stereocomplex crystal (SC) in the differential scanning calorimetry first and second heating processes without indicating the trace of the melting of homo‐chiral crystal. The mixing at an elevated temperature causes a serious thermal degradation. Further kneading of the blends at an elevated temperature higher than T_m of SC causes the transesterification between the same enatiomeric chains forming block copolymers of l ‐ and d ‐chains. This block copolymer acts as a nucleating agent of SC and the compatibilizing agent between poly(l ‐lactide) and poly(d ‐lactide) and promotes the formation of SC. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45489.