High Molecular Weight PLA Research Articles

Novel catalyst-solvent system for high molecular weight polylactic acid synthesis via azeotropic solution polycondensation method

ABSTRACT Polycondensation for PLA synthesis is widely used due to its cost-effectiveness, but it often leads to low molecular weight PLA. To address this limitation, researchers have explored different catalysts, with the stannous chloride and p-toluene sulfonic acid combination being a popular choice. However, this method typically yields PLA with a MW of no more than 35000 g/mol, which is unsuitable for commercial applications. In contrast, ring-opening polymerization is considered the most effective method for synthesizing high MW PLA, despite its complexity and cost. Industrial-scale production predominantly employs ROP due to its capability to produce high MW PLA. The use of stannous octoate as a catalyst for ROP has shown promise in synthesizing higher MW PLA. However, its sensitivity to water limits its use in polycondensation, where stannous chloride is commonly employed but is not capable of synthesizing high MW PLA. This study explores the use of stannous octoate for the synthesis of high MW PLA with higher yield.

A response surface methodology for the use of MIL‐101 as a catalyst for the one‐step synthesis of lactide

Lactide is a vital monomer for producing high molecular weight polylactic acid (PLA) through ring‐opening polymerization. This study synthesized crude lactide from L‐lactic acid with MIL‐101 as the catalyst. MIL‐101 is a metal‐based catalyst with organic ligands (MOF) that was prepared by reacting Cr(NO3)3.9H2O with terephthalic acid (BDC). The formation of MIL‐101 was confirmed from Fourier‐transform infrared (FTIR) analysis. The role of MIL‐101 and the effect of temperature, time, and MIL‐101 loading, as well as their interactions in the conversion of lactic acid to crude lactide, were then investigated using the response surface method (RSM). Crude lactide was analyzed using 1H‐nuclear magnetic resonance (NMR) spectroscopy to confirm the presence of lactide. The RSM results indicated that the highest conversion of 22.84% can be obtained using a temperature of 175 °C, 1.5% w/w MIL‐101 loading, and a reaction time of 5 h. The RSM model showed that the interaction of MIL‐101 loading and reaction time strongly affected the conversion of lactic acid to lactide, with a P‐value of 0.0021 and an F‐value of 50.45. In contrast, the interaction of catalyst loading and temperature did not significantly affect the conversion of lactic acid to lactide, with a P‐value of 0.2565 and an F‐value of 1.75.

Detection and elimination of trace d-lactic acid in lignocellulose biorefining chain: Generation, flow, and impact on chiral lactide synthesis.

High chiral purity of lactic acid is a crucial indicator for the synthesis of chiral lactide as the primary intermediate chemical for ring-open polymerization of high molecular weight polylactic acid (PLA). Lignocellulose biomass is the most promising carbohydrate feedstock for commercial production of PLA, but the presence of trace d-lactic acid in the biorefinery chain adversely affects the synthesis and quality of chiral lactide. This study analyzed the fingerprint of trace d-lactic acid in the biorefinery chain and found that the major source of d-lactic acid comes from lignocellulose feedstock. The naturally occurring lactic acid bacteria and water-soluble carbohydrates in lignocellulose feedstock provide the necessary conditions for d-lactic acid generation. Three strategies were proposed to eliminate the generation pathway of d-lactic acid, including reduction of moisture content,conversion of water-soluble carbohydrates to furan aldehydes in pretreatment, and conversion to l-lactic acid by inoculating engineered l-lactic acid bacteria. The natural reduction of lactic acid content in lignocellulose feedstock during storage was observed due to the lactate oxidase-catalyzedoxidation of l- and d-lactic acids. This study provided an important support forthe production of cellulosic l-lactic acid with high chiral purity.

Blown film stability for low, medium, and high molecular weight polylactic acid and their tensile properties

Three poly (lactic acid) (PLA) resins with molecular weight (Mw) equal to 55 (3251D), 125 (L105) and 163 (LX175) kg/mol were characterized in terms of capillary viscosity, mechanical and thermal properties and used to produce blown films. The effect of temperature, extrusion rate, stretching (TUR) and blow-up (BUR) ratios were evaluated to determine the optimum processing conditions for blown films based on the bubble stability and to determine their final tensile properties. As expected, the processing temperature was the most critical parameter on the film stability. The lower Mw PLA showed limited processing stability. Stable conditions were found at higher temperature (200°C) for higher Mw. These results correlate with the PLA viscosity (melt strength). Finally, the PLA film tensile strength (TS) strongly depended on their processability. For example, 3251D and L105 required high stretching (TUR = 3.4 and 7) for maximum TS (30 and 64 MPa) with a low blow-up ratio (BUR = 1.02–1.15). However, a moderate increase in BUR (10% at TUR = 3) led to a substantial drop in TS (from 29 MPa to 21 MPa for PLA 3251D and 44 MPa–34 MPa for L105). Overall, LX175 was the most interesting resin with 49 MPa TS which was independent of the BUR and TUR used in this investigation.

Bioaugmentation with a defined bacterial consortium: A key to degrade high molecular weight polylactic acid during traditional composting

Polylactic acid (PLA) is commercialized as a compostable bio-thermoplastic. PLA degrades under industrial composting conditions where elevated temperatures are maintained for a long timeframe. However, these conditions cannot be achieved in a non-industrial compost pile. Therefore, this study aims to degrade high molecular weight PLA films by adding a PLA-degrading bacterial consortium (EAc) comprised of Nocardioides zeae EA12, Stenotrophomonas pavanii EA33, Gordonia desulfuricans EA63, and Chitinophaga jiangningensis EA02 during traditional composting. With EAc-bioaugmentation, PLA films (5–30% w/w) had complete disintegration (35 d), 77–82% molecular weight reduction (16 d), and higher CO2 liberation and mineralization than non-bioaugmented composting. Bacterial community analyses showed that EAc-bioaugmentation increased the relative abundance of Schlegelella, a known polymer degrader, and interacted positively with beneficial indigenous microbes like Bacillus, Schlegelella and Thermopolyspora. The bioaugmentation also decreased compost phytotoxicity. Hence, consortium EAc shows potential in PLA-waste treatment applications, such as backyard and small-scale composting.

Cyclic l-lactide synthesis from lignocellulose biomass by biorefining with complete inhibitor removal and highly simultaneous sugars assimilation.

Cyclic chiral lactide is the monomer chemical for polymerization of high molecular weight polylactic acid (PLA). The synthesis of cyclic l-lactide starts from poly-condensation of l-lactic acid to a low molecular weight prepolymer and then depolymerized to cyclic l-lactide. Lignocellulose biomass is the most promising carbohydrate feedstock for lactic acid production, but the synthesis of cyclic l-lactide from l-lactic acid produced from lignocellulose has so far not been successful. The major barriers are the impurities of residual sugars and inhibitors in the crude cellulosic l-lactic acid product. Here we show a successful cyclic l-lactide synthesis from cellulosic l-lactic acid by lignocellulose biorefining with complete inhibitor removal and coordinated sugars assimilation. The removal of inhibitors from lignocellulose pretreatment was accomplished by biodetoxification using a unique fungus Amorphotheca resinae ZN1. The nonglucose sugars were completely and simultaneously assimilated at the same rate with glucose by the engineered l-lactic acid bacterium Pediococcus acidilactici. The l-lactic acid production from wheat straw was comparable to that from corn starch with high optical pure (99.6%), high l-lactic acid titer (129.4 g/L), minor residual total sugars (~2.2 g/L), and inhibitors free. The cyclic l-lactide was successfully synthesized from the regularly purified l-lactic acid and verified by detailed characterizations. This study paves the technical foundation of carbon-neutral production of biodegradable PLA from lignocellulose biomass.

Studies on the degradation and characterization of a novel metal-free polylactic acid synthesized via lipase-catalyzed polymerization: A step towards curing the environmental plastic issue

Polylactic acid (PLA) is becoming one of the most paramount polymers due to its eco-friendly, biocompatible, and biodegradable nature. The feedstock (lactic acid) employed for PLA synthesis can be produced from agro-resources. Polylactic acid is expected to replace many conventional polymers, notably those used in food packaging and agricultural mulch. PLA processing techniques are ring-opening polymerization and direct condensation reactions. Mostly, polycondensation reaction uses a metal catalyst (Zn/Sn oxides), which is not safe for biomedical applications as it contains metal contamination. To make PLA more commercially appealing, ways to accelerate its degradation are constantly pursued. The work will include the synthesis of novel biodegradable metal-free bioplastic to solve the environmental plastic problems. A bioprocess was developed for manufacturing high molecular weight PLA using an enzymatic polymerization process. FTIR, NMR, GPC, XRD, DSC, TGA, and SEM analysis demonstrated the considerable change in the characteristic, morphological and thermal structures of PLA. Lactide formation was analyzed by FTIR and NMR study, followed by the monomer polymerization using lipase enzyme. The degree of crystallinity drops by 11.12% after degradation. GPC and TGA analysis confirmed the maximum M W loss and lowered T max by 46 °C after being buried in compost. SEM analysis showed the existence of cracks and voids after degradation. This new approach for the synthesis of metal-free degradable PLA would encourage its use for plastic and biomedical products in the future. • High molecular weight metal-free PLA synthesized through the enzymatic process. • Metal-free PLA can be used in a variety of food and biomedical application. • PLA degraded after one month in compost, and M W dropped 88%. • SEM images revealed a change in surface morphology from smooth to cracks and holes.

Vibrational Spectroscopy Analysis of Oligothiophene Blend Film

One of the challenges in fabricating organic semiconductor thin film is to produce bettermolecular ordering that compromise its electronic properties. Molecular ordering of amorphous thin film can be improved in many ways. Here, high molecular weight polylactic acid (PLA) is introduced as binding matrix to promote 3'''-didodecyl-2,2':5',2'':5'',2'''-quaterthiophene (4T) film’s homogeinity across indium tin oxide (ITO) surface. Molecular ordering of the spin coated biodegradable PLA and 4T blend film processed at ambient atmosphere was studied using two vibrational spectroscopy methods. The complementary analysis of infrared absorption spectrum and Raman spectrum had identified several vibrational modes contributed by thiophene rings and alkyl functional groups. The Raman analysis implied there is a slight change of thiophene ringsʼ molecular orientation due to compressive stress after introduction of polymer. Microscopic characteristics of oligothiophenes especially at the π-π conjugated backbones contained crucial information in order to exploit the oligothiophene as flexible electronics devices.

Depolymerization of End‐of‐Life Poly(lactide) to Lactide via Zinc‐Catalysis

AbstractThe chemical recycling of poly(lactide) (PLA), especially the initial depolymerization step was studied. High molecular weight PLA was depolymerized in the presence of zinc catalyst to lactide, the industrial relevant chemical for the synthesis of high molecular weight PLA; therefore, an efficient recycling is feasible without the need for depolymerization reagents. An excellent performance was observed for zinc(II) acetate with turnover frequencies of up to ∼260 h−1at 200–210 °C. Noteworthy, the lactide was isolated in high purity by reactive distillation. Furthermore, the zinc(II) acetate catalyst was recycled up to five times.

Stiffness of HIV-1 Mimicking Polymer Nanoparticles Modulates Ganglioside-Mediated Cellular Uptake and Trafficking.

The monosialodihexosylganglioside, GM3, and its binding to CD169 (Siglec‐1) have been indicated as key factors in the glycoprotein‐independent sequestration of the human immunodeficiency virus‐1 (HIV‐1) in virus‐containing compartments (VCCs) in myeloid cells. Here, lipid‐wrapped polymer nanoparticles (NPs) are applied as a virus‐mimicking model to characterize the effect of core stiffness on NP uptake and intracellular fate triggered by GM3‐CD169 binding in macrophages. GM3‐functionalized lipid‐wrapped NPs are assembled with poly(lactic‐co‐glycolic) acid (PLGA) as well as with low and high molecular weight polylactic acid (PLAlMW and PLAhMW) cores. The NPs have an average diameter of 146 ± 17 nm and comparable surface properties defined by the self‐assembled lipid layer. Due to differences in the glass transition temperature, the Young's modulus (E) differs substantially under physiological conditions between PLGA (E PLGA = 60 ± 32 MPa), PLAlMW (E PLA lMW = 86 ± 25 MPa), and PLAhMW (E PLA hMW = 1.41 ± 0.67 GPa) NPs. Only the stiff GM3‐presenting PLAhMW NPs but not the softer PLGA or PLAlMW NPs avoid a lysosomal pathway and localize in tetraspanin (CD9)‐positive compartments that resemble VCCs. These observations suggest that GM3‐CD169‐induced sequestration of NPs in nonlysosomal compartments is not entirely determined by ligand–receptor interactions but also depends on core stiffness.

On the nucleation of polylactide by melt-soluble oxalamide based organic compounds

In this work, a series of oxalamide based organic compounds (OBOC) are synthesized and their capability to enhance the nucleation of polylactide is reported. The OBOCs are soluble in the polylactide melt and crystallize upon cooling, providing surface for heterogeneous nucleation to the polylactide matrix. One interesting observation is that the nucleation efficiency of the OBOCs increases at high cooling rates, making the use of OBOCs as a nucleating agent attractive for industrial processing conditions. The paper addresses the mechanism involved in the cooling rate dependence on the nucleation efficiency of the OBOC: The nucleation efficiency of polylactide is significantly enhanced in the presence of OBOC crystals, as a transcrystalline PLA morphology grows from the OBOC crystal surface (at relatively low supercooling from the equilibrium melting temperature of PLA). However, such crystallization of PLA occurs only when the OBOC crystals are formed at or below 145 °C while cooling at 10 °C/min. In contrast, when the OBOC crystals are formed above 145 °C (i.e. from a lower supersaturated state), the OBOC crystals display a significantly reduced capability for PLA nucleation. These findings override the possibility of both epitaxy and soft-epitaxy as a plausible nucleation mechanism. Supported by polarized optical microscopy, differential scanning calorimetry, plate-plate rheology and molecular modelling we evaluate the possibility of nucleation resulting from local stresses imposed on the polylactide melt invoking stress-enhanced nucleation. The imposed local shear rates, facilitated by the rapid growth of the OBOC crystals, are found high enough to facilitate contour orientation of the high molecular weight PLA chains next to the growing OBOC crystals, confirming the possibility for stress-enhanced nucleation. In addition, we identify surface roughness of OBOC crystals as a second parameter that influences the PLA nucleation process; the OBOC crystallization at high supersaturation is expected to yield smaller/defected OBOC crystals, which are presumed to provide high surface area and surface roughness. In contrast, when the OBOC crystals are grown at lowered supersaturation (>150 °C), they are bound to anneal during crystallization, providing a smoother surface and lower surface area – retrospectively exhibiting a decreased capability to promote the PLA nucleation, irrespective of the PLA supercooling. Interestingly, both the surface roughness of OBOC crystals and the local stresses they impose on the PLA melt increase when the OBOC crystal growth proceeds from a highly supersaturated state, providing an explanation to the cause of the favored crystallization of PLA at the high cooling rates in the presence of the chosen OBOCs.

Eco-friendly poly(lactic acid) microbeads for cosmetics via melt electrospraying

Microbeads (MBs) are essential materials for cosmetic and healthcare applications. However, environmental pollution has recently emerged as a concern due to the non-degradability and adsorption property of persistent organic pollutants (POPs) in environmental conditions, particularly in the marine environment. Therefore, the development of biodegradable MBs via eco-friendly methods is urgently demanded. Poly(lactic acid) (PLA) is a biodegradable and melt-processable aliphatic polyester which can be obtained from raw materials in nature. In this study, the high molecular weight PLA was pre-treated by electron beam (E-beam) irradiation in order to adjust the melt viscosity. Subsequently, the PLA MBs were prepared by varying the processing parameters via an eco-friendly melt electrospraying process. During the time, the PLA MBs showed bulk degradation which lead to decrement of the residual weight, thermal and structural stability. On the other hand, the crystallinity of PLA MBs was significantly increased due to the degradation of amorphous region. Furthermore, the PLA MBs showed poor POPs adsorption behavior compare with the commercial MBs because of low specific surface area. From these results, the PLA MBs via green method have a great potential to replace the non-degradable MBs in cosmetics.

Bacillus pumilus B12 Degrades Polylactic Acid and Degradation Is Affected by Changing Nutrient Conditions.

Poly-lactic acid (PLA) is increasingly used as a biodegradable alternative to traditional petroleum-based plastics. In this study, we identify a novel agricultural soil isolate of Bacillus pumilus (B12) that is capable of degrading high molecular weight PLA films. This degradation can be detected on a short timescale, with significant degradation detected within 48-h by the release of L-lactate monomers, allowing for a rapid identification ideal for experimental variation. The validity of using L-lactate as a proxy for degradation of PLA films is corroborated by loss of rigidity and appearance of fractures in PLA films, as measured by atomic force microscopy and scanning electron microscopy (SEM), respectively. Furthermore, we have observed a dose-dependent decrease in PLA degradation in response to an amino acid/nucleotide supplement mix that is driven mainly by the nucleotide base adenine. In addition, amendments of the media with specific carbon sources increase the rate of PLA degradation, while phosphate and potassium additions decrease the rate of PLA degradation by B. pumilus B12. These results suggest B. pumilus B12 is adapting its enzymatic expression based on environmental conditions and that these conditions can be used to study the regulation of this process. Together, this work lays a foundation for studying the bacterial degradation of biodegradable plastics.

Mechanical, rheological and anaerobic biodegradation behavior of a Poly(lactic acid) blend containing a Poly(lactic acid)-co-poly(glycolic acid) copolymer

The goal of this work is to examine the thermal, rheological, mechanical and thermophilic anaerobic biodegradation performance of PLA blends containing a highly degradable polymer. Here random copolymers consisting of Poly(l-lactic acid) (PLLA) and Poly(glycolic acid) (PGA) structural units (75:25 M ratio) were synthesized at three different molecular weights (Mw = 16, 58 and 113 kg mol−1) and melt blended with a high molecular weight PLA homopolymer. The glass transition temperature (Tg) of poly(lactic acid-co-glycolic acid) (PLGA) was lower than that of PLA and increased with copolymer molecular weight. A single Tg intermediate to that of the two blend constituents was observed suggesting miscibility. Polymer blends showed enhanced methane production at early stages of anaerobic degradation with the rate increasing with increasing PLGA content and decreasing PLGA molecular weight. Blends exhibited a decrease in modulus and tensile strength as compared to pure PLA. Likewise, a decrease in ductility for all but the lowest molecular weight copolymer containing blend was observed. The zero-shear viscosity of polymer blends scaled predictably with PLGA content and exhibited reduced sensitivity to shear-rate. It is envisioned that this strategy could be applied for those applications where recycling is prohibitive such as at universities, hospitals and stadiums where mixed waste streams containing plastics and other waste types, such as food and paper, can be anaerobically co-digested and the resulting biogas used as fuel.

Development of eco-environmental nano-emulsified active coated packaging material

Coated packaging film with nano-emulsified polylactic acid (PLA) was prepared as an extended shelf life package for chicken fillet. PLA was prepared by direct polycondensation to be prepared after that nanoparticles by solvent displacement as potential coating for packaging systems. The characterizations of PLAwere done by thermo-gravimetric measurement size exclusion chromatography and differential scanning calorimetry. Additionally, the particle size distribution was measured by dynamic light scattering which exhibited narrow particle size distribution with mean particle size ≈70 nm. The effect of PLA nanoparticles coating was evaluated as an active packaging for a chicken fillet stored at 4 °C. An aerobic plate, coliforms counts (APC) and sensory score were also studied. The Low molecular weight PLA (LM-PLA) reduces APC by 1.5 log cfu/g and coliforms count by 75 MPN/g than the control and extended the storage time more than 2 days. Meanwhile, a high molecular weight PLA (HM-PLA) significantly reduces APC by 2.1 log cfu/g and coliforms count by 107 MPN/g lower than the control beside extended the storage time by more than 3 days. Although dipping in lactic acid 1% for 5 min and 2% for 10 min was increased the storage time to 11th and 15th days respectively. Moreover, the sensory score of chicken fillet packaged in PLA were significantly high.

Facile melt processing technique for the preparation of super ductile PLA–PEG multiblock copolymers: The roles of catalyst and antioxidant loadings

The unprecedented use of chain-scission reaction to constitute a facile and one-pot approach for the preparation of multiblock copolymers consisting of poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG) from high molecular weight PLA was demonstrated. This involves two consecutive steps including melt transesterification (1) of PLA with PEG catalyzed by nontoxic titanium-based catalyst in an internal mixer to form short-chain block copolymers, followed by chain extension (2) using hexamethylene diisocyanate (HDI) to obtain long-chain multiblock copolymer products. Due to the primary concern on the counterbalance between chain-scission and exchange reactions, the effects of catalyst and antioxidant loadings were investigated. Excessive addition of the catalyst beyond optimal point not only deteriorated the formation of desirable products in step 1 (due to accelerated thermal degradation of PEG), but also posed detrimental effects on the efficacy of the chain extension in step 2 and mechanical properties of the final products. When appropriate amount of catalyst (0.75 phr) was used in combination with antioxidant, the long-chain copolymers exhibited extraordinarily high ductility with strain-to-break values exceeding 500%.

Synthesis and structures of aluminum ion-pair complexes that act as L- and racemic-lactide ring opening polymerization initiators

Seven aluminum ion-pair complexes (1–7) were synthesized by reaction of NNO Schiff base ketoimines with differing substituents with tris(2,6-dimethylphenoxy) aluminum dimer in an inert atmosphere glovebox at room temperature. The complexes were characterized with 1H, 13C, and 19F nuclear magnetic resonance spectroscopy, absorbance spectroscopy, and elemental analysis. Furthermore, the dinuclear nature of the complexes was elucidated with single crystal X-ray crystallography and 27Al NMR. The ion-pair complexes consisted of a bis-ligating homoleptic ketoiminate with octahedral coordination as an aluminum cation complex and a tetrahedral aluminum anion complex of 2,6-dimethylphenoxide. Each ion-pair was used to initiate the ring opening polymerization (ROP) of L- and rac-lactide to poly-lactic acid (PLA) in toluene at 100 °C at a 100:1 [LA]:[ion-pair] ratio. Proton NMR spectra showed percentage conversions of monomer to polymer of 96–99% in 18 h. The isolated polymeric materials were determined to have moderate molecular weights with low to moderate polydispersity index values using gel permeation chromatography. The bis-ligated aluminum cation and tetraphenoxide aluminate anions of 1 were isolated into separate compounds (8 and 9) with unreactive counter ions, and each yielded low molecular weight PLA under the polymerization conditions. Thus, lactide polymerization appeared to require both ion-pair components to yield the moderately high molecular weight PLA, and this was investigated spectroscopically.

Effect of molecular weight on the nucleation efficiency of poly(lactic acid) crystalline phases

PLA is well known to exhibit a low degree of crystallinity and slow crystallization kinetics. It is also a polymorphic material with two slightly different crystalline phases named α and α’. This work aimed at investigating the effect of PLA crystalline phases on the kinetics of crystallization, by means of a simple, telling and expedient technique, known as self-nucleation. To achieve this purpose, PLA samples were first crystallized at various temperatures to change the mix in the α and α’ phases. The samples were then partially melted by increasing the temperature near the melting temperature and then crystallized again upon cooling to examine the effect of the α and α’ crystal remnants on the non-isothermal crystallization behavior. A double crystallization peak was clearly evidenced for self-nucleated PLA samples indicative of the different crystallization efficiency of the two PLA phases using a specific thermal protocol. Thermal analysis, XRD and optical microscopy were combined to examine the effect of cooling rate and holding time at a given partial melting temperature on the ratio between the two observed crystallization peaks. Moreover, effect of molecular weight of PLA on the crystallization kinetics and the self-nucleation of PLA was investigated. The self-nucleation experiments revealed that the low and high-molecular weight PLA exhibited the highest non-isothermal crystallization temperature, Tcmax, equal to 160 °C for the samples isothermally crystallized in the range of temperature between 80 and 130 °C. Although for the high-molecular weight PLA Tcmax was a function of the original crystalline phase as well as the phase transition mechanism, for the low-molecular weight PLA, it was constant regardless of what the initial crystalline phase was. Based on crystallization and melting enthalpies, the proportion of the α and α’ phases was quantified using deconvolution analysis.

Divergent [{ONNN}Mg-Cl] complexes in highly active and living lactide polymerization.

Chloro-magnesium complexes of divergent tetradentate-monoanionic {ONNN}-type ligands which formed as either mononuclear or dinuclear complexes are reported. These complexes catalyze the ring-opening polymerization of lactide with high activity and in a living manner, and enable the synthesis of well-defined stereo-diblock copolymers with Mn > 200 kDa, as well as stereo-n-block copolymers (n = tri, tetra) with high molecular weights by sequential monomer addition. Thermal and crystallographic characterizations revealed that even the very high molecular weight PLA copolymers crystallized in a stereocomplex phase, and that their degradation temperature was as high as 354 °C.

Properties and medical applications of polylactic acid: A review

Polylactic acid (PLA), one of the well-known biodegradable polyesters, has been studied extensively for tissue engineering and drug delivery systems, and it was also used widely in human medicine. A new method to synthesize PLA (ring-opening polymerization), which allowed the economical production of a high molecular weight PLA polymer, broad- ened its applications, and this processing would be a potential substitute for petroleum-based products. This review described the principles of the polymerization reactions of PLA and, then, outlined the various materials properties affect- ing the performance of PLA polymer, such as rheological, mechanical, thermal, and barrier properties as well as the pro- cessing technologies which were used to fabricate products based on PLA. In addition, the biodegradation processes of products which were shaped from PLA were discussed and reviewed. The potential applications of PLA in the medical fields, such as tissue engineering, wound management, drugs delivery, and orthopedic devices, were also highlighted.