Biodegradable Blends Research Articles

Thermo-Mechanical Properties of Injection Molded Components Manufactured by Engineered Biodegradable Blends

Engineering of ductile, tough and thermal resistant PLA-based materials requires blending of PLA with other constituents by reactive twin-screw co-rotating extrusion to achieve compounds with adequate thermo-mechanical properties. Then, the compound of the polymeric blends must be melt processed to the final shape with an additional technology, namely the injection molding. The two-stage process the polymeric blends must undergo and the different rheological properties the blends must feature to be suitable to the different processing steps make extremely difficult to engineer the material. Extrusion compounding requires high viscous materials low melt flow index (MFI), while injection molding requires materials with low viscosity (high MFI). To overcome these shortcomings, this manuscript deals with the design of novel biodegradable PLA-based blends that rely on mixing PLA grades with different MFI (i.e. very low for extrusion and high for injection molding), each chosen to feature the rheological characteristics needed for each step of the two-stage transformation process. The ratio of the two PLA-grades inside the blends was the matter of the present investigation. The blends were subsequently tested for the manufacturing of single-use biodegradable and thermal resistant injection molded small cups, specifically designed for brewing of hot beverages. Lastly, the thermo-mechanical performance of the as-is and annealed cups were studied. Experimental evidences show blending of two-different grades of PLA is a promising route to formulate low impact polymeric materials suitable for demanding packaging solutions.

Extrusion blow molding of environmentally friendly bottles in biodegradable polyesters blends

Increasing awareness of the environmental impact of oil-relying plastic materials is prompting Academia and manufacturing industry to develop eco-friendly materials and alternative technological solutions. Blown bottles and containers represent a significant share of the worldwide plastic market and great environmental concern is arising about their disposal. Generally, blown plastic bottles are made of three different materials: (i) a cap manufactured from High Density Polyethylene (HDPE), (ii) a bottle body manufactured from Polyethylene Terephthalate (PET), (iii) a label manufactured from printed Low Density Polyethylene (LDPE). The disposal of blown bottles requires, therefore, the separation of the different materials and, then, their individual recovery. An eco-friendly alternative to multi-material blown bottles is the development of a bottle entirely made from a biodegradable polymeric blend, designed to be suitable for manufacturing both the cap, the bottle body and the label. In this framework, the present manuscript deals with the design and development of novel biodegradable blends based on bio-based polyesters. The blends are herewith specialized for extrusion blow molding of the bottle body, although they could be further customized for both the cap and the label. Twin-screw co-rotating extrusion of the compounds, extrusion blow molding of the compounds for bottle manufacturing and the evaluation of the thermo-physical and mechanical properties of the bottles are hereinafter reported. The novel polymeric blends are found to be suitable for extrusion blow molding of the bottle body, also exhibiting valuable performances in terms of mechanical strength and impact resistance as well as protection against gas permeation and light transmission.

Morphology and Properties of a New Biodegradable Material Prepared from Zein and Poly(butylene adipate-terephthalate) by Reactive Blending.

In this study, zein, a renewable natural biopolymer from corn, was used to prepare a new biodegradable material with poly(butylene adipate-terephthalate) (PBAT) by reactive blending in the presence of poly(ethylene glycol diglycidyl ether) (PEGDGE). The effects of blending temperature and zein content on the morphology and mechanical and thermal properties of PBAT/zein blends with or without PEGDGE were investigated. Because of the high reactivity of the epoxy group in PEGDGE, the interfacial compatibility between zein and PBAT was improved greatly, and zein exhibited as a spheral phase with smaller size and finer dispersion in the PBAT matrix after the introduction of PEGDGE. Therefore, PEGDGE served as a plasticizer and reactive compatibilizer in the PBAT/zein blending system. Both the tensile strength and elongation at break of the blends with PEGDGE were improved greatly compared with those of the blends without PEGDGE but decreased gradually with the increase of zein content. These findings may provide a feasible way to utilize zein widely, and the new biodegradable blends with excellent stretchability could be used as packing materials in the future.

Isothermal crystallization kinetics of biodegradable poly(lactic acid)/poly(ε‐caprolactone) blends compatibilized with low‐molecular weight block copolymers

The isothermal crystallization kinetics of biodegradable blends made of poly(lactic acid) (PLA) and poly(ε‐caprolactone) (PCL) compatibilized with two different low molecular weight block copolymers, that is, ε‐caprolactone/tetramethylene ether glycol and ε‐caprolactone/aliphatic polycarbonate (CB), was done. Blends were prepared by melt mixing in an extruder, while isothermal crystallization kinetics and morphologies were investigated by thermal (differential scanning calorimetry) and thermo‐optical (quantitative polarized light optical microscopy [qPLOM]) quantitative methods. Data were analyzed using the Avrami equation, revealing 2D and 3D growth and simultaneous heterogeneous nucleation. The presence of low molecular weight compatibilizers, that is, 2,000 g mol−1, accelerated the PLA crystallization rate by two to threefold when compared with neat PLA, with high degrees of crystallinity (40–43%) as confirmed by PLOM images. The activation energy (Ea) showed that PCL inhibits PLA crystallization; however, the addition of block copolymers used as compatibilizers of the blends reduced Ea values, increasing the chain mobility of PLA and thus increasing the crystallization rate. POLYM. ENG. SCI., 59:E161–E169, 2019. © 2018 Society of Plastics Engineers

Biodegradability of blends based on aliphatic polyester and thermoplastic starch

In this work, biodegradable aliphatic polyester blends of polycaprolactone and polylactide were melted and blended with a natural and biodegradable thermoplastic starch (TPS). The TPS employed in this study was obtained by plasticization of isolated wheat starch using glycerol as plasticizer. Morphology as well as thermal properties of the blends was investigated, and water vapor permeability as a barrier property was also monitored. The biodegradability of the biodegradable blends was performed by a composting process on laboratory scale. The composting process was conducted in an adiabatic closed reactor for 21 days and during the composting process, the temperature, pH value, % moisture and volatile matter and evolved CO2 were monitored. Biodegradation of the blends was determined by weight loss, as well as monitoring of morphological surface change. The thermophilic phase prevailed in the composting process, indicating intensive biodegradation of substrate as well as biodegradation of investigated ternary blends. Since microorganisms use starch as a carbon source, addition of TPS causes considerable acceleration of biodegradation of ternary blends due to higher water vapor permeability as a result of the hydrophilic nature of starch. The thermoplastic starch was first degraded within the blend, which was facilitated access to the microorganisms of other ingredients in the blend, encouraging the biodegradation of other components.

Influence of thermoplasticized starch on physical-chemical properties of new biodegradable carriers intended for forest industry

In this work, the influence of different concentrations of thermoplasticized starch on thermal, mechanical, biodegradation and phytotoxic properties of biodegradable blend carrier composed of poly(lactic acid) and poly(butylene adipate‑co‑terephtalate) was investigated. The results showed that the addition of poly(butylene adipate‑co‑terephtalate) increased elasticity of PLA materials, whereas the presence of thermoplasticized starch promoted higher biodegradation rate of the investigated materials. Moreover, the prepared materials did not show phytotoxic effect on plant, thus proving potential application in forest industry as a biodegradable carrier for multiplication of plants.

Effect of Selected Commercial Plasticizers on Mechanical, Thermal, and Morphological Properties of Poly(3-hydroxybutyrate)/Poly(lactic acid)/Plasticizer Biodegradable Blends for Three-Dimensional (3D) Print.

This paper explores the influence of selected commercial plasticizers structure, which are based on esters of citric acid, on mechanical and thermal properties of Poly(3-hydroxybutyrate)/Poly(lactic acid)/Plasticizer biodegradable blends. These plasticizers were first tested with respect to their miscibility with Poly(3-hydroxybutyrate)/Poly(lactic acid) (PHB/PLA) blends using a kneading machine. PHB/PLA/plasticizer blends in the weight ratio (wt %) of 60/25/15 were then prepared by single screw and corotating meshing twin screw extruders in the form of filament for further three-dimensional (3D) printing. Mechanical, thermal properties, and shape stability (warping effect) of 3D printed products can be improved just by the addition of appropriate plasticizer to polymeric blend. The goal was to create new types of eco-friendly PHB/PLA/plasticizers blends and to highly improve the poor mechanical properties of neat PHB/PLA blends (with majority of PHB) by adding appropriate plasticizer. Mechanical properties of plasticized blends were then determined by the tensile test of 3D printed test samples (dogbones), as well as filaments. Measured elongation at break rapidly enhanced from 21% for neat non-plasticized PHB/PLA blends (reference) to 328% for best plasticized blends in the form of filament, and from 5% (reference) to 187% for plasticized blends in the form of printed dogbones. The plasticizing effect on blends was confirmed by Modulated Differential Scanning Calorimetry. The study of morphology was performed by the Scanning Electron Microscopy. Significant problem of plasticized blends used to be also plasticizer migration, therefore the diffusion of plasticizers from the blends after 15 days of exposition to 110 °C in the drying oven was investigated as their measured weight loss. Almost all of the used plasticizers showed meaningful positive softening effects, but the diffusion of plasticizers at 110 °C exposition was quite extensive. The determination of the degree of disintegration of selected plasticized blend when exposed to a laboratory-scale composting environment was executed to roughly check the “biodegradability”.

Studies on the mechanical, barrier, optical, and characterization of photo-/biodegradable LDPE-PLA blend with nanoclay for packaging film application

LDPE-poly-lactic acid (PLA) (60:40%) was melt blended with nanoclay (1, 2, and 3%) and benzophenone (3%) using maleic anhydride-grafted LLDPE (LLDPE- g-MAn; 3%) as compatibilizer in a twin screw compounding extruder. Tubular blown films extruded using Dr Collins blown film extruder were subjected to various mechanical tests like tensile strength, elongation at break, and so on, optical tests, and permeability tests for oxygen and water vapor. The tensile strength was increased as the nanoclay percentage was increased (upto 2 wt%) and the elongation at break was decreased. Tear strength was increased, burst strength was decreased, and the dart impact strength was constant. The coefficient of friction was little decreased. The haze was increased and luminous transmittance was decreased. Water vapor transmittance and oxygen gas permeability were decreased. Scanning electron microscope images were taken to determine the morphological changes on the samples. Characterization by X-ray diffraction was carried out to analyze the shift in peak when nanoclay was blended at various proportions. In conclusion, LDPE with benzophenone is photodegradable and PLA is biodegradable. Hence, in this study, LDPE-PLA (60:40%) with benzophenone (3%) is photo-/biodegradable. Inclusion of nanoclay increased the mechanical properties like tensile strength, tear strength, and barrier properties. Furthermore, nanoclay improves the compatibility apart from LLDPE- g-MAn.

Development of a biodegradable antifibrotic local drug delivery system for glaucoma microstents.

To prevent implant failure due to fibrosis is a major objective in glaucoma research. The present study investigated the antifibrotic effects of paclitaxel (PTX), caffeic acid phenethyl ester (CAPE), and pirfenidone (PFD) coated microstent test specimens in a rat model. Test specimens based on a biodegradable blend of poly(4-hydroxybutyrate) biopolymer and atactic poly(3-hydroxybutyrate) (at.P(3HB)) were manufactured, equipped with local drug delivery (LDD) coatings, and implanted in the subcutaneous white fat depot. Postoperatively, test specimens were explanted and analyzed for residual drug content. Fat depots including the test specimens were histologically analyzed. In vitro drug release studies revealed an initial burst for LDD devices. In vivo, slow drug release of PTX was found, whereas it already completed 1 week postoperatively for CAPE and PFD LDD devices. Histological examinations revealed a massive cell infiltration in the periphery of the test specimens. Compact fibrotic capsules around the LDD devices were detectable at 4–36 weeks and least pronounced around PFD-coated specimens. Capsules stained positive for extracellular matrix (ECM) components. The presented model offers possibilities to investigate release kinetics and the antifibrotic potential of drugs in vivo as well as the identification of more effective agents for a novel generation of drug-eluting glaucoma microstents.

Cold crystallization kinetics of biodegradable polymer blend; controlled by reactive interactable and nano nucleating agent

Poly(lactic acid) (PLA) is famous for its crystalline nature and ability to show exothermic crystallization (cold crystallization) peak during heating cycle of differential scanning calorimetric study. To get an insight into the mechanism of cold crystallization of PLA in its promising forms like biodegradable blend and biodegradable blend nanocomposite, a kinetic study has conducted and reported in the present study. Biodegradable blend of PLA has prepared with poly(hydroxybutyrate) (PHB). Subsequently, blend nanocomposite has prepared using organically modified layered nano silicate. Maleic anhydride has used as a reactive compatibilization agent to modify the interface of the partially miscible blend of PLA and PHB. Kinetics and mechanism of crystallization have monitored through isothermal cold crystallization method on the basis of Avrami relationship. Avrami exponent ‘n’ and equilibrium rate constant ‘K’ value has taken into consideration to quantify the crystallization rate. The half-life of crystallization and equilibrium melting point also has estimated as additional findings to confirm the estimated rate of crystallization. Variation in the energy of activation (Ea) using Arrhenius relation and regime transitions during crystallization process through Lauritzen–Hoffman (L-H) equation also have been reported.

Rheological and thermal characterization of PCL/PBAT blends

The development of biodegradable blends is an important option for reducing environmental impacts generated by the use of plastics, besides increasing the knowledge biodegradable polymers and its associations. In this contribution, rheological and thermal characteristics of neat PCL and PBAT and PCL/PBAT blends melt mixed in an internal laboratory mixer were evaluated. The results suggested that the blends are immiscible but there is a strong interaction between the components. Crystallization kinetics can be represented by Pseudo-Avrami model.

Chitosan/polyethylene glycol fumarate blend films for wound dressing application: in vitro biocompatibility and biodegradability assays

Blending is one of the effective approaches in preparing tailored materials with a wide range of properties. Thus, chitosan-based polymers have been fabricated and used as wound dressings since they possess better properties than those of the constituent materials. The objective of this work was to evaluate the biocompatibility and biodegradability of biodegradable blend films based on polyethylene glycol-co-fumarate (PEGF) and chitosan (Ch). The blend films of Ch/PEGF were prepared by solution casting/solvent evaporation method. Degradation behavior of these blend films was evaluated in a simulated fluid at physiological pH supplemented with lysozyme at a concentration similar to that in human serum by weight loss of the films and changes in the pH of media. When the pH of incubation media was analyzed, with an increase of PEGF content in the blend films, the degradation rate increased accordingly. The pH of the media of samples was not significantly changed at any measured time point and all films kept their integrities during 28 days. The biocompatibility of the films and cell behavior on the surface of these films were investigated by in vitro tests. Biological assessment using mouse fibroblast cell line L929 on the blend films of Ch/PEGF indicated that films supported the attachment, spreading and proliferation of cells. Since the Ch/PEGF films are biocompatible with the tailored biodegradation rate, they might have a great prospective position in the application of wound dressings.

Improvement of mechanical properties and thermal stability of biodegradable rice starch–based films blended with carboxymethyl chitosan

Biodegradable blend films from rice starch (RS) and carboxymethyl chitosan (CMCh) were produced and characterized. Color, opacity, mechanical properties, thermal properties, swellability, oxygen and water permeability, and biodegradability of the RS–CMCh blend films are reported. Interaction and compatibility of films components were evaluated by using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction. Increased yellowness, total color difference and transparency, and decreased redness, lightness and whiteness index were observed in the blend films as incorporation of CMCh increased. Addition of 50% w/w of CMCh into the RS matrix increased the tensile strength of the RS–CMCh blend film by 35% and the elongation at break by 28%. Addition of CMCh improved the thermal stability of the RS–CMCh films. Incorporation of 12, 33 and 50% w/w CMCh in the blend films increased the swelling ratio by around 850%, 3985% and 3404% at 24 h, respectively, when compared with the RS film. The oxygen permeability of all the films increased as relative humidity increased. The FTIR spectra suggested that interactions may be present between the OH groups of RS and the COO groups of CMCh. Scanning electron microscopy images revealed that the cross-sectional fracture surfaces of all the films were smooth and homogenous. The RS film exhibited a priming effect in the biodegradation study. The addition of 50% w/w CMCh led to a decrease in mineralization of the blend films.

Performance and drug release studies of poly (ɛ-caprolactone)/γ-poly (glutamic acid) fibrous membranes

Fibrous membranes of poly(ɛ-caprolactone)/γ-poly(glutamicacid) (PCL/γ-PGA) composites were successfully produced via an electrospinning process. In doing so, the water solubility of florfenicol (FF) could be enhanced and the drug release properties of FF could be controlled. The mechanical, morphologic, and thermal properties of the fibrous membranes of PCL/γ-PGA were studied by using an electronic single fiber strength machine, scanning electron microscopy, and differential scanning calorimetry. The wettability of the fibrous membranes of PCL/γ-PGA was also measured as discussed in the subsequent section. Fourier transform infrared spectroscopy was applied in the structural analysis of the PCL/γ-PGA-FF fibrous membranes. The results indicated that FF was well blended in the composite membranes of PCL/γ-PGA. In vitro dissolution tests showed that PCL/γ-PGA (85/15; 8%) as both a biodegradable and biocompatible blend may improve the solubility of FF. Therefore, fibrous membranes of PCL/γ-PGA may represent ideal materials for the controlled drug release in various clinical applications.

Effect of Babassu Natural Filler on PBAT/PHB Biodegradable Blends: An Investigation of Thermal, Mechanical, and Morphological Behavior.

Blending of biodegradable polymers in combination with low-price organic fillers has proven to be a suitable approach to produce cost-effective composites in order to address pollution issues and develop products with superior mechanical properties. In the present research work PBAT/PHB/Babassu composites with 25, 50, and 75% of each polymer and 20% of Babassu were produced by melting extrusion. Their thermal, mechanical, and morphological behavior was investigated by differential scanning calorimetry (DSC), tensile testing, and scanning electron microscopy (SEM). Blending PBAT with PHB inhibited the crystallization of both polymers whereas adding Babassu did not significantly change their melting behaviour. Incorporation of Babassu reduced the tensile strength of its respective blends between 4.8 and 32.3%, and elongation at break between 26.0 and 66.3%. PBAT as highly ductile and low crystalline polymer may be seen as a crystallization tool control for PHB as well as a plasticizer to PBAT/PHB blends and PBAT/PHB/Babassu composites. As PBAT content increases: (i) elongation at break increases and (ii) surface fracture becomes more refined indicating the presence of more energy dissipation mechanisms. As PBAT/PHB/Babassu composites are biodegradable, environmental friendly, and cost effective, products based on these compounds have a great potential since their mechanical properties such as ductility, stiffness, and tensile strength are still suitable for several applications even at lower temperatures (−40 °C).

Non-isothermal degradation kinetics of virgin linear low density polyethylene (LLDPE) and biodegradable polymer blends

The thermal degradation kinetics of several polymers, including biodegradable blends were investigated in non-isothermal thermogravimetry using several analytical methods. Virgin linear low density polyethylene (LLDPE) and LLDPE blends with polystarch-N (PSN), a prodegradant starch additive material used in 20 and 40 wt%., were investigated to determine the degradation behaviour of such materials in pyrolysis conditions. The results were compared to those obtained with virgin low (LDPE) and high density polyethylene (HDPE). An analytical solution model was also developed to assess the two degradation steps of the biodegradable blends which enabled the assessment of the apparent activation energy (Ea) of each material in the blend on its own based on the initial and final degradation temperatures. It was observed that the thermal behaviour and Ea value didn’t change significantly with the increase of biodegradable prodegradant, which shows that biodegradable blends can be treated with similar conditions regardless of the content of the biodegradable masterbatch present in the blend.

Preparation and property testing of polymer blends of poly(lactic acid) and poly(butylene succinate) plasticised with long-chain fatty acids

ABSTRACTThis study investigates the influence of three fatty acids (lauric acid, palmitic acid, and stearic acid) on biodegradable polymer blends based on poly(lactic acid) (PLA) and poly(butylene succinate) (PBS), containing different weight ratios (100:0, 100:2, and 100:4) of fatty acids on the transparency, mechanical properties, morphology, contact angle, and water vapour permeability. All of the blends were pressed into thin films and tested. The experimental results showed that the properties of the samples varied with chain length and amounts of the fatty acids. Thus, it could be concluded that use of fatty acids opens up new ways for the plasticisation of PLA/PBS blends for use as new bioplastics.

Fully Biodegradable Poly(lactic acid)/Poly(propylene carbonate) Shape Memory Materials with Low Recovery Temperature Based on in situ Compatibilization by Dicumyl Peroxide

Fully biodegradable blends with low shape memory recovery temperature were obtained based on poly(lactic acid) (PLA) and poly(propylene carbonate) (PPC). By virtue of their similar chemical structures, in situ cross-linking reaction initiated by dicumyl peroxide (DCP) between PLA and PPC chains was realized in PLA/PPC blends. Therefore, the compatibility between PLA and PPC was increased, which obviously changed the phase structures and increased the elongation at break of the blends. The compatibilized blends had a recovery performance at 45 °C. Combining the changes of phase structures, the mechanism of the shape memory was discussed. It was demonstrated that in situ compatibilization by dicumyl peroxide was effective to obtain eco-friendly PLA/PPC blends with good mechanical and shape memory properties.

Characterization of 3D Printed PLA/PCL/TiO2 Composites for Cancellous Bone

The reproduction of a 3D bone structure with suitable porosity, which allows the flow of nutrients, blood, oxygen and mineral, remains a problem using conventional methods. A material that mimics their properties was developed by optimizing the ratio of a biodegradable blend of immiscible polylactic acid (PLA) and poly-e-caprolactone (PCL). In this study, PLA and PCL particularly optimize the strength of the artificial cancellous bone by supplying the initial support strength lasting 6 months to 2 years and allowing for the gradual degradation desired in the human body. This study focused on the mechanical properties of successfully printed 3D structures. The ultimate tensile strength was modified by blending different ratios of PLA and PCL resulting in an optimum value of approximately 30 MPa when the ratio of PLA to PCL reached 3:1. The addition of 1 wt.% of titanium dioxide (TiO2) to the immiscible PLA/PCL composite and the modification of the interface area between them resulted in the formation of a binding force that allowed for an increase in the tensile strength up to 37 MPa. Besides the mechanical properties, the in vitro biocompatibility of PLA/ PCL/TiO2 composites was examined. A vigorous cell growth was observed in the cells cultivated with the PLA/PCL/TiO2 composites and the unimpeded ability to differentiate into osteoblast also was found. The resulting properties of the 3D printed structures indicate promising applications in the fields of bone tissue engineering and cancellous bone grafting.

Viscoelastic modelling of creep and stress relaxation behaviour in PLA-PCL fibres

In case of high performance athletes, ligaments are the most commonly injured tissues. Current gold standard process for replacement of ligament is autografting. Research in the field of biodegradable polymers (as a possible ligament device) has helped in overcoming the various drawbacks of autografting. Biodegradable blend of polylactic acid and polycaprolactone (PLA-PCL) have been proposed for use in a medical device to repair injured ligaments. By using a mathematical model, this study aims to characterise the non-linear viscoelastic properties of PLA-PCL fibres. In the present study, two modified models were used; the Burger’s model and three-element standard solid model. The model parameters were calibrated by using the tensile and creep experimental data. In case of Burger’s model, the parameters were significantly affected by the stress level. This functional stress dependency was represented by a second degree polynomial. By employing the previously computed parameters, the stress relaxation data of PLA-PCL fibres was used to check the model simulations. Only the predictions generated from the modified three-element standard solid model were found to be in an agreement with the experimental data. This model enables representing the general viscoelastic response of PLA-PCL fibres through a unique set of parameters.