Polylactide Materials Research Articles

Design of toughed bio-based polylactide/polyamide 11 blends with regulatable size of dispersed phase and spherulites by interfacial stereocomplex crystallites

Enhancing the ductility of polylactide (PLA) through toughening modification to expand the application range of PLA aligns with the requirements of green development. In this study, eco-friendly bio-based plastic polyamide 11 (PA11) was chosen to modify poly(l-lactide) (PLLA). PA11 and poly(d-lactide) (PDLA) were grafted onto the main chain of ADR via simple reactive processing and utilized as reactive compatibilizers to improve toughening efficiency of PA11. The successful preparation of the graft copolymer was confirmed through 1H NMR, FT-IR and DSC, and a detailed investigation was conducted on how the composition and concentration of the compatibilizer influence the mechanical properties, phase morphology, crystallization, and nucleation behaviors of PLLA/PA11 blends. Elongation at break of the 5 % PDLA/PA11 graft copolymers toughed PLLA was as high as 222 % at 30 % PA11 content, which was 17 times greater than the PLLA toughened by pristine PA11 without compromising the strength. PLLA and PA11 were immiscible binary blends with PA11 droplet/PLLA matrix phase separated morphologies in the molten state. Based on the calculation of interfacial tension, the grafted copolymer would be mainly distributed at the interface between the two phases. The dispersion of PA11 droplet in PLLA matrix was improved since the interfacial interaction force was enhanced through in-situ reaction. The increase of the nucleation site and decrease of the spherulites size were worked synergistically by stereocomplex (SC) crystallites and PA11. Under the impact of reducing the size of the dispersed phase and spherulites, the toughness of blends was enhanced. This study provided valuable insights into the control of PLLA immiscible blend morphology and elucidated the relationship between the size of dispersed phase and spherulites and the ultimate mechanical performance of bio-based PLA materials.

The Development of Polylactide Nanocomposites: A Review

Polylactide materials present a promising alternative to petroleum-based polymers due to their sustainability and biodegradability, although they have certain limitations in physical and mechanical properties for specific applications. The incorporation of nanoparticles, such as layered silicate (clay), carbon nanotubes, metal or metal oxide, cellulose nanowhiskers, can address these limitations by enhancing the thermal, mechanicals, barriers, and some other properties of polylactide. However, the distinct characteristics of these nanoparticles can affect the compatibility and processing of polylactide blends. In the polylactide nanocomposites, well-dispersed nanoparticles within the polylactide matrix result in excellent mechanical and thermal properties of the materials. Surface modification is required to improve compatibility and the crystallization process in the blended materials. This article reviews the development of polylactide nanocomposites and their applications. It discusses the general aspect of polylactides and nanomaterials as nanofillers, followed by the discussion of the processing and characterization of polylactide nanocomposites, including their applications. The final section summarizes and discusses the future challenges of polylactide nanocomposites concerning the future material’s requirements and economic considerations. As eco-friendly materials, polylactide nanocomposites offer significant potential to replace petroleum-based polymers.

Ultrahigh strength and toughness of polylactide added with EGMA elastomer of a small amount processed via pressure-induced flow above the glass transition temperature

Elastomer toughening is widely recognized as a highly effective strategy for enhancing the mechanical performance of plastics. However, the improvement in toughness generally comes at the cost of a drastic sacrifice in tensile strength. In this work, ethylene–acrylic ester-glycidyl methacrylate random terpolymer (EGMA) of a small amount of 5 % in mass was applied as a toughening agent of polylactide (PLA), with the assistance of a pressure-induced flow processing at above the glass transition temperature. The obtained PLA blend showed simultaneously improved tensile strength and impact toughness. The tensile strength and Young′s modulus maintained at a relatively high level of 58 MPa and 2.1 GPa, respectively, and the notched Izod impact strength reached up to 54 kJ/m2, which was 27 times higher than that for neat PLA (1.9 kJ/m2). The increased toughness was primarily attributed to a synergistic effect of the reduced crystal sizes, reduction in phase domain sizes and enhanced interfacial interactions. This study provided a cost-effective and feasible approach to achieving strong and super-tough PLA materials, which held a significant potential for PLA widespread applications.

Absorption of water molecules on the surface of stereocomplex-crystal spherulites of polylactides: An in-situ FT-IR spectroscopy investigation

The correlation between water molecules and polylactide was clarified. The crystallinity in stereocomplex (SC) crystal spherulites was investigated using microbeam wide-angle X-ray diffraction. The crystallinity was higher in the central region, and edge-on lamellae grew in a twisted manner. The hydrogen bonding in SC-crystal spherulites was evaluated via microbeam FT-IR spectroscopy in a humidity-controlled cell. The water-derived bands corresponding to OH vibration and HOH bending increased with increasing humidity. Microbeam FT-IR spectroscopy was used to evaluate the water absorption behavior of crystalline films depending on their position. Coarse-grained molecular dynamics simulations indicated that the number of adsorbed water molecules increased with decreasing crystallinity. In SC-crystal spherulites, water molecules are absorbed in both amorphous and crystalline regions but with greater difficulty in the crystalline regions. These insights into water molecule absorption on SC-crystal spherulite can facilitate the development of polylactide materials with controlled biodegradability for advanced medical and optical applications.

Pengaruh Proses Annealing Terhadap Akurasi Dimensi Dan Kuat Tarik 3D Printing Menggunakan Filamen ST-PLA

3D printing is a tool used to make objects / test specimens in 3 dimensions, using the main material made from polymer. In 3D printers there are two types of filaments that are often used today, namely Polylactic acid or polylactide (PLA) material and Acrylonitrile butadiene styrene (ABS), the material used in this study is PLA material, this material was chosen because it has several advantages. Poly(lactic acid) (PLA) biodegradable thermoplastics have been used in various industrial fields including automotive, computer, food, and electrical equipment also used in medical devices, PLA is a biodegradable thermoplastic sourced from natural starches such as corn and sugarcane. Therefore, this study aims to find the highest tensile strength in PLA materials using several levels of testing, The highest tensile test result at one parameter level will be carried out by the annealing process to determine the effect of the annealing process on the tensile test specimen. The research method used in this study is the Taguchi method designed L9 with 3 factors and 3 levels, using the Analysis of Variance (ANOVA) analysis method. The test results showed that the highest tensile strength was located in study number 5, which was 44.866 Mpa, and the lowest average tensile test value was in study number 4, which was 40.033 Mpa.

Composite Polylactide Materials Based on Amorphized Hydroxyapatite and Brushite for 3D Printing

Composite Polylactide Materials Based on Amorphized Hydroxyapatite and Brushite for 3D Printing

Enhancing mechanical and shape memory properties of polylactide/polyamide elastomer blends via reactive blending with a chain extender

AbstractThe structure and properties of incompatible polylactide (PLA)/polyamide elastomer (PAE) blends were tailored by a chain extender specifically the styrene–glycidyl acrylate copolymer Joncryl ADR4368 (ADR). Various PLA/PAE/ADR blends with different compositions were prepared by melt blending, and their morphology, crystallization behavior, and mechanical and the shape memory properties were systematically investigated. The results showed a uniform dispersion of PAE particles in the PLA matrix for the PLA blends with a reduction in particle size upon the addition of ADR. The crystallization of PLA was retarded, which was confirmed by a decrease in the melt crystallization temperature and an increase in cold crystallization temperature in the PLA/PAE/ADR blends. Rheological analysis showed an improvement in the melt elasticity of the PLA/PAE binary blend due to the presence of ADR, possibly attributed to the formation of long‐chain‐branched copolymers at the interface. Notably, the PLA/PAE/ADR blend exhibited superior toughness, featuring an elongation at break of 288% and a notched impact strength of 37 kJ·m−2, along with a high shape memory fixation rate and recovery rate when the ADR content was 1 wt%. Furthermore, the underlying toughening mechanism was elucidated. This work may offer an industrially scalable relevant model to fabricate high‐performance PLA materials.

ТЕХНОЛОГІЧНІ ОСОБЛИВОСТІ ОДЕРЖАННЯ КРОХМАЛЬВМІСНИХ ПОЛІЛАКТИДНИХ МАТЕРІАЛІВ ДЛЯ 3D ДРУКУ

Polylactide composite materials with organic filler-modifier starch, inorganic filler -calcium carbonate and plasticizer – epoxidized soybean oil for 3D printing have been developed. On the basis of the modular deformation method of calculation the elastic-plastic and deformation properties of the developed modified polylactide materials are determined. The change of modulus of deformation, modulus of elasticity, modulus of high elasticity depending on the composition of the composite is revealed. The surface hardness, Vicat softening point and thermomechanical characteristics of the developed polylactide materials are determined

Preferential formation of stereocomplex crystals in poly(L-lactic acid)/poly(D-lactic acid) blends by a fullerene nucleator

Selective formation of stereocomplex (sc) crystallization in enantiomeric poly(L-lactic acid)/poly(D-lactic acid) (PLLA/PDLA) blends is considered as one of the most effective and promising way to improve the mechanical and thermal properties of polylactide (PLA) materials. However, homocrystallization (hc) prevails over sc crystallization in high-molecular-weight (HMW) PLLA/PDLA blends. Herein, we propose a simple and straightforward approach for fabricating sc crystallization and suppress hc crystallization for HMW PLLA/PDLA blends through the addition of C70 as a nucleator. Non-isothermal crystallization and wide-angel X-ray diffraction studies demonstrate that, the incorporation of 1 wt% C70 overwhelmingly leads to the formation of sc crystallites, while preventing the formation of hc crystallites. Isothermal crystallization experiments at 140 °C reveal a significant reduction in the half-crystallization period of the PLLA/PDLA blend upon the addition of C70. Fourier-transformed infrared spectroscopy suggests that, the improved intermolecular interactions between PLLA and PDLA chains, as well as the inhibition of molecular chain diffusion and mobility, contribute to the accelerated formation of sc facilitated by C70. The enhanced sc crystallization results in a 15.5 °C higher thermal stability in the as-prepared PLLA/PDLA blend with 1 wt% C70 compared to the neat counterpart.

Polylactide-based networks containing dynamic tetraphenylethane groups for 3D printed repairable and reprocessable constructs

This study aims to synthesize sustainable polylactide (PLA) materials, specifically polyester-urethanes based on PLAs with various molecular weights, to enhance thermal shape stability through crosslinking and enable reprocessing due to the presence of a new type of dynamic/reversible covalent bonds in the polymer structure. PLA-based networks containing dynamic bonds were prepared by coupling (using hexamethylene diisocyanate) PLA star polymers bearing four terminal -OH groups with a low molecular weight diol containing groups that undergo reversible dissociation upon heating. The PLAs prepolymers of two molecular weights (Mn = 3700 and 7800 g/mol) were synthesized via cationic polymerization of D,L-lactide to obtain the networks of different crosslinking densities. The low molecular weight diol, containing a tetraphenylethane moiety (TPE) with an easy dissociating bond, was synthesized from 4-hydroxybenzophenone. Networks without reversible bonds, containing 1,1′-bi-2-naphthol (binol) instead of TPE units, were also prepared as a reference. All networks were analyzed by Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis and were subjected to tensile tests. The tensile strength of all networks was in the range of 22–45 MPa. The elongations at break of networks differed based on the type of used low molecular weight diol, with values in the range of 28–67% for TPE-containing networks, in comparison with 10% for reference samples. Rheological studies of these materials were performed at a higher temperature (150 °C) to clearly demonstrate the behavioral differences between networks with and without “reversible” bonds. Only the networks with TPE groups were able to recover their previous strength after strain deformation at 150 °C in four subsequent cycles. Moreover, it was shown that networks with reversible groups were repairable and 3D printable at temperatures as low as 150 °C, while those containing non-reversible bonds did not exhibit such capability.

Sustainable polylactide materials with the function of blocking a specific wavelength of light based on aloe-emodin

Polylactide, a biodegradable polymer, can alleviate white pollution, but the use of polylactide in food packaging is limited by high transmittance to light with a specific wavelength, UV (185–400 nm) and short-wavelength visible (400–500 nm) light. Herein, the polylactide end-capped with renewable light absorber aloe-emodin (PLA-En), is blended with commercial polylactide (PLA) to fabricate the polylactide film with the function of blocking light with a specific wavelength, PLA/PLA-En film. Only 40 % of light around 287 and 430 nm transmits through PLA/PLA-En film incorporating 3 mass% of PLA-En, while the film still maintains good mechanical properties and high transparency more than 90 % at 660 nm because of the good compatibility with PLA. The PLA/PLA-En film exhibits stable light-blocking properties under light irradiation and anti-solvent migration under the immersion of fat simulant. Almost no PLA-En migrated out of the film with the molecular weight of PLA-En only 2.89 × 104 g/mol. Compared with PLA film and commercial PE plastic wrap, the designed PLA/PLA-En film exhibits a better preservative effect on riboflavin and milk for inhibiting the production of 1O2. This study offers a green strategy for developing UV and short-wavelength light protective food package film based on renewable resource.

Development of Stereocomplex Polylactide Nanocomposites as an Advanced Class of Biomaterials-A Review.

This review paper analyzes the development of advanced class polylactide (PLA) materials through a combination of stereocomplexation and nanocomposites approaches. The similarities in these approaches provide the opportunity to generate an advanced stereocomplex PLA nanocomposite (stereo-nano PLA) material with various beneficial properties. As a potential "green" polymer with tunable characteristics (e.g., modifiable molecular structure and organic-inorganic miscibility), stereo-nano PLA could be used for various advanced applications. The molecular structure modification of PLA homopolymers and nanoparticles in stereo-nano PLA materials enables us to encounter stereocomplexation and nanocomposites constraints. The hydrogen bonding of D- and L-lactide fragments aids in the formation of stereococomplex crystallites, while the hetero-nucleation capabilities of nanofillers result in a synergism that improves the physical, thermal, and mechanical properties of materials, including stereocomplex memory (melt stability) and nanoparticle dispersion. The special properties of selected nanoparticles also allow the production of stereo-nano PLA materials with distinctive characteristics, such as electrical conductivity, anti-inflammatory, and anti-bacterial properties. The D- and L-lactide chains in PLA copolymers provide self-assembly capabilities to form stable nanocarrier micelles for encapsulating nanoparticles. This development of advanced stereo-nano PLA with biodegradability, biocompatibility, and tunability properties shows potential for use in wider and advanced applications as a high-performance material, in engineering field, electronic, medical device, biomedical, diagnosis, and therapeutic applications.

Supertoughened Polylactide via the Addition of Low Content Poly(ε-caprolactone) and Tensile Deformation above the Glass Transition Temperature

Polylactide (PLA) is considered as an ideal alternative of petroleum-based plastics due to its high tensile strength and biodegradability. However, the low impact strength limits its extensive application in the engineering field. In this work, a supertough binary PLA blend was fabricated through pre-stretching above the glass transition temperature to a certain pre-strain. The biodegradable and biocompatible poly(ε-caprolactone) (PCL) was used as a toughening modifier for the PLA/PCL 95/5 (wt/wt) blend. It was found that the impact strength increased with the increase in pre-strain. The highest notched Izod impact strength reached 251 kJ/m2 at the pre-strain of 400%, nearly 132 times of that for neat PLA (1.9 kJ/m2). To our knowledge, such fabulous impact toughness has not been referred in literature. Even at the pre-strain of 150%, the blend exhibited a sufficiently high notched Izod impact strength of 149 kJ/m2. Small-angle X-ray scattering demonstrated a typical structural feature of combination of PLA shish-kebabs and oriented PCL lamellar stacks due to strain-induced crystallization. The wide-angle X-ray diffraction indicated that PLA crystals had high orientation at the pre-strain of 200% and above. The crystallinity of the PLA matrix increased with the increase in pre-strain, which was consistent with the increasing trend of impact strength. The high orientation of shish-kebabs and increased crystallinity of PLA matrix were the key factors for drastically toughening PLA. This work provides a feasible and effective method to manufacture competitive PLA materials, which can be extended to improve impact toughness of other brittle glassy polymers.

Progress of Ring-Opening Polymerization of Cyclic Esters Catalyzed by Iron Compounds

Aliphatic polyesters such as polylactide (PLA) and polycaprolactone (PCL) have attracted much attention due to their prominent features of environmentally friendly materials with good biocompatibility and biodegradability. The commercialized PLA and PCL materials have been commonly prepared at high temperature using tin octanoate as catalysts: however, a higher temperature of polymerization potentially causes broader dispersity or/and lower molecular weight of the resultant polymers; most importantly, residual tin catalysts in the polymer products may be harmful to mammals and/or other living organisms in the ocean. As an abundant metal in the earth, not only is iron an essential element in the human body but also its compounds play important roles in pharmaceutical and polymerization chemistry. Recently, iron-based compounds have been proved to be efficient promoters of ring-opening polymerization of cyclic esters under mild conditions. Herein the progress of iron compounds used for the ring-opening polymerization (ROP) of cyclic esters is reviewed in order to develop practical catalysts for industrial processes in the future.

Numerical Investigation of the Effect Infill from Different Unit cells Structure on Mechanical Behaviour

This study aims to identify the effect of infill on mechanical behaviour, especially the yield stress and modulus young of polylactide materials with different unit cell structures such as gyroid, diamond, square, and re-entrant but same porosity with value of 60%. Using Computational aided design (CAD) software and analyzed using the finite element method. The results show that the square structure has the highest strength in terms of mechanical behaviour such as yield stress with a value of 27 MPa, while the gyroid is 25.5 MPa, diamond is 25.3 MPa, re-entrant is 23.3 MPa and young modulus square is 2233MPa gyroid is 2199 MPa, diamond is 2195 MPa re- entrant 2182 MPa. In this study, it was also found that the thickness struth of the unit cell and modulus young had a very strong linear correlation with R2 = 0.96 which explains that the higher the thickness value, the higher the modulus young value. The results of this study also show that although lattice structures, especially square ones, have the highest value, TPMS structures, such as gyroids and diamonds, have more stable performance because these structures have an even stress distribution, thereby reducing the risk of failure of the structure. besides that, the researchers concluded that this TPMS can be used as a solution to improve structural performance.

Physico-Chemical, Mechanical, and Biological Properties of Polylactide/Portulaca oleracea Extract Electrospun Fibers.

Electrospinning was used to create fibrous polylactide (PLA) materials loaded with Portulaca oleracea (P. oleracea) plant extract obtained by supercritical carbon dioxide. Morphological, physico-chemical, mechanical, and biological characteristics of the fibers were studied. According to the SEM results, the diameters of smooth and defect-free fibers fabricated by a one-pot electrospinning method were at micron scale. All the obtained materials possess good mechanical properties. Additionally, it was found that the composite fibers exhibited considerable antioxidant activity. The antimicrobial activity of the fibrous materials against Gram-positive and Gram-negative bacteria was determined as well. In vitro studies showed that the electrospun biomaterials had no cytotoxic effects and that the combination of PLA and the P. oleracea extract in the fiber structure promoted cell survival and proliferation of normal mouse fibroblasts. The obtained results reveal that microfibrous mats containing the polyester-PLA and the plant extract-P. oleracea can be suitable for applications in wound healing.

Local biocompatibility and biochemical profile of hepatic cytolysis in subcutaneous implantation of polylactide matrices

The aim of the study was to investigate local biocompatibility and systemic effects of nonwoven polylactide (PLA) matrices on blood and liver parameters after their subcutaneous implantation in Wistar rats.Materials and methods. Bioabsorbable fibrous PLA matrices were produced by electrospinning and had dimensions (10 × 10 mm², thickness of no more than 0.5 mm; fiber diameter in the matrix ~1 μm) appropriate for subcutaneous implantation in white laboratory rats. Polymer implants were sterilized in ethylene oxide vapor. Thirty days after the implantation of PLA matrices, local biocompatibility according to GOST ISO 10993-6-2011, cellular parameters (total leukocyte count, hemogram, erythrocyte count, hemoglobin concentration), and biochemical blood parameters (lactate concentration, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels) were studied, and a standard histologic evaluation of the liver was performed.Results. PLA matrix samples were mild local irritants on a scale of 1–1.9 points according to GOST ISO 10993-6-2011 criteria 30 days after the subcutaneous implantation. The median density of distribution of multinucleated giant cells (MNGCs) in the connective tissue around and in PLA matrices was 1,500 (1,350; 1,550) per 1 mm² of a slice. Pronounced leukocytic reaction due to lymphocytosis was noted (an increase by 1.7 times compared with a sham-operated (SO) control group, р < 0.02). The absence of a significant neutrophil count in the blood revealed sterile inflammation proceeding in the subcutaneous tissue around the PLA materials. Normalization of hepatic cytolysis markers (ALT and AST activity) in the blood without pronounced changes in the structure of the liver and the number of binuclear hepatocytes was noted. These markers were increased in SO controls (ALT up to 123% and AST up to 142%, p < 0.001 compared with values in the intact group).Conclusion. Nonwoven PLA matrices are biocompatible with subcutaneous tissue, undergo bioresorption by MNGCs, and have a distant protective effect on the functional state of the liver in laboratory animals. Hypotheses on the detected systemic effect during subcutaneous implantation of PLA matrices were discussed; however, specific mechanisms require further study.

Composite polylactide materials based on amorphisized hydroxyapatite and brushite for 3D- printing

Composite polylactide materials based on amorphisized hydroxyapatite and brushite for 3D- printing

ОСОБЛИВОСТІ ВПЛИВУ ЕПОКСИДОВАНОЇ СОЄВОЇ ОЛИВИ НА ВЛАСТИВОСТІ ПОЛІЛАКТИДНИХ МАТЕРІАЛІВ

Polylactide composite materials with the plasticizer-compatibilizer epoxidized soybean oil, which are filled with organic filler starch and inorganic – calcium carbonate, have been developed. Based on instrumental methods of analysis, the influence of epoxidized soybean oil on the features of physicochemical interactions in the system was investigated. A change in the rheological and thermophysical properties of the developed polylactide materials was established depending on the component composition.

Biocompatibility and biocidal effects of modified polylactide composites.

Polylactide (PLA) materials treated with antimicrobial fillers represent a suitable alternative to the production of medical devices. Their advantage is that they can prevent the growth of microorganisms and the formation of microbial biofilms on the surface and around composites. The work is focused on the evaluation of biocompatibility and biocide effect of PLA composite films filled with vermiculite and graphene oxide modified with silver (Ag+ and Ag nanoparticles), hexadecylpyridinium (HDP) and hexadecyltrimethylammonium (HDTMA) cations and their degradation leachates monitored at 1-3-6-month intervals. The antimicrobial effect of the leachates was detected by microdilution methods on gram-negative (Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis), gram-positive (Staphylococcus aureus, Streptococcus salivarius) bacteria and yeast (Candida albicans). The biocidal effect of composites on biofilm formation on the surface of composites was monitored by Christensen method and autoaggregation and motility tests. The biocompatibility of the composite and the leachates was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) cytotoxicity assay. The evaluation of the antimicrobial effect of the leachates demonstrated that leachates of PLA composite filled with graphene oxide and Ag+ showed a stronger antimicrobial effect than leachates of PLA composite filled with vermiculite and Ag+ and Ag nanoparticles. The leachates of PLA composites containing vermiculite with HDP and HDTMA cations had a higher antimicrobial effect on G+ bacteria and yeast than G- bacteria. Bacterial growth, biofilm formation, autoaggregation and motility of the tested bacteria were most inhibited by the composite with vermiculite and Ag+ and Ag nanoparticles. Even after a 6-month degradation of this composite, bacterial growth and biofilm formation continued to be strongly inhibited up to 42 and 91%, respectively. The cytotoxic effect was proved only in the leachate of the composite with vermiculite containing HDP after 6 months of its degradation. Tests evaluating the biocompatibility of materials have shown that the vermiculite is the most preferred carrier and can be used in the future to bind other compounds. The study confirmed that PLA composite filled with vermiculite and Ag+ and Ag nanoparticles was the most stable and effective composite with the best biocompatible and biocidal properties.