PLA-based Polymers Research Articles

Preliminary Insight Into Torsion of Additively-Manufactured Polylactic Acid (PLA)-Based Polymers

BackgroundPolymers in practical applications often face diverse torsional loads, such as polymeric gears, couplings, scaffolds, etc. Meanwhile, additive manufacturing enables the creation of intricate geometries for specific needs and its application to fabricate various component parts has grown exponentially. Nevertheless, research on cyclic and reversed cyclic torsional loading of additively-manufactured polymers is very limited.ObjectiveMechanical characterization of monotonic, cyclic, and reversed cyclic torsion in polylactic acid (PLA), PLA Premium, and PLA Tough materials.MethodsSpecimens were 3D-printed with a 0° build orientation using an extrusion technique and two infill orientation angles (± 45° and 0°/90°). Specimens were subjected to underwent monotonic, cyclic, and reversed cyclic torsion until failure.ResultsRegardless of material type, ductile fracture governed the behavior under monotonic loading and brittle failure under cyclic and reversed cyclic loadings. Specimens with a ± 45° infill orientation outperformed their 0°/90° counterparts across all materials, with PLA Premium exhibiting superior performance compared to PLA and PLA Tough. Importantly, it was demonstrated that the previously-proposed multilinear idealized shear stress-shear strain curve, developed for monotonic loading of 15 different polymers, also applies to the envelope curves of cyclic and reversed cyclic loading in PLA-based polymers. Thus, it is useful as material model input for numerical simulation purposes.

Production of supertough and semiconductive PLA-based polymer blend nanocomposites by kinetic microstructural control

Polymer nanocomposites with superior multi-functional properties can be fabricated by tuning their morphology. In this work, a supertough and semiconductive polylactide (PLA)-based polymer blend nanocomposite (PBNANO) was produced for the first time via melt blending with a core-shell rubber (CSR) and carbon nanotubes (CNT). Reference binary blends (PLA/CSR and PLA/CNT) revealed that, when added separately, 20 wt% of CSR and 0.25 wt% of CNT were the suitable quantities to achieve a supertough and a semiconductive PLA-based material, respectively. Based on the obtained results, PLA/CSR/CNT PBNANOs with 20 wt% of CSR and CNT amounts between 0.15 and 0.50 wt% were prepared in one extrusion step. Although supertoughness was achieved in all the cases, the PBNANOs were insulating due to the selective localization of the CNT in the poly(methyl methacrylate) (PMMA) shell of the CSR and the good dispersion of the CSR nanoparticles. However, a supertough and semiconductive PLA-based PBNANO was obtained by a two-step melt compounding. Using this processing sequence, a worse dispersion of the CSR was obtained, allowing contact between some CSR nanoparticles. The differences in PBNANOs morphology prepared in one or two extrusion steps were determined by TEM and corroborated by rheological measurements. In the case of the two extrusion steps PBNANO, the CNT were located in both the PLA matrix and in the shell of the CSR. This morphological change enabled the PBNANO to be conductive, as the CNT percolation was achieved in this case while still remaining supertough.

Exploring the utilization of polylactic acid-based materials in medicine: Contemporary innovations and trends

A biocompatible, non-toxic substance is polylactic acid (PLA), which is also biodegradable. This material has been studied for decades and has been commercially used in some fields. The potential of defined PLA for different medical applications, including drug delivery systems, wound healing, bone implants, and vascular grafts, was described in this paper. Various methods of characterization and modification of PLA have been investigated to optimize its properties for specific applications. Typically, additional polymers are introduced into PLA to enhance its functional properties. The key feature of PLA is its capacity for degradation in the human body without introducing harmful byproducts. Adjustments to PLA composition can control degradation rates, influencing drug delivery or the persistence of implants. By applying a cold plasma treatment in order to alter the PLA-based polymer's surface, the capacity of the material to transport drugs may be changed. The change of parameters in coaxial electrospinning can produce different PLA-based products for different use. However, certain challenges remain, such as improving the adhesion of PLA and production of low-price PLA.

Manufacturing Millimeter-Wave Horn Antennas Using 3D Printing and Direct Electrodeposition

Additive manufacturing has undergone huge development in recent years. It has become commonplace both for the hobbyist community and industry, with important applications in several domains (e.g. biomedical, aerospace and automotive). Its main strength lies in the fact that custom parts can be quickly prototyped and manufactured, regardless of their complexity. However, many of the 3D printing techniques still have limitations in terms of strength, materials, production speed and overall usability. One of the main limitations is that most techniques utilize polymers, which are intrinsically non-conductive. This limits their use in electronics and telecommunication applications.Meanwhile, a lot of equipment used in telecommunications, such as antennas, tuners, waveguides, etc. remain very expensive due to complex and time-intensive manufacturing techniques. This leads to high prices, long lead times and limitations in the complexity of the geometries. The main goal of this research is to develop a fast and cost-effective method to produce conductive structures using additive manufacturing, more specifically fused deposition modeling (FDM) 3D printing. A special focus is put on horn antennas for microwave applications, as this application is very demanding on both the accuracy of the geometry and the conductivity of the structure.The approach in this work mainly consists of two steps: optimizing the plating conditions on flat test samples and extending this knowledge to the three-dimensional horn antenna. The chosen material is a PLA-based polymer with carbon black as an additive, which provides the polymer with some electrical conductivity (factor ~107 lower than copper). This conductivity is too low for any meaningful application but allows for the use of electrodeposition of copper directly onto the polymer to increase the conductivity. By focusing on reducing the distance from the electrical contact to the surface to be plated and by tuning the deposition parameters, high-quality uniform copper deposition is obtained on test samples. The achieved results outperform the current state-of-the-art in this field.The knowledge acquired from the test samples is then applied to the horn antenna. To this end a conductive antenna holder is developed. The antenna holder serves to keep the potential as constant as possible over the entire antenna surface in order to promote homogeneous deposition. It also aligns the electrodes, keeping the distance between electrodes as constant as possible and preventing short circuits. This method results in good partial coverage and again produces better results than can be found in the literature. However, direct deposition of a nicely uniform layer over the entire surface remains very challenging. An indirect electrodeposition method using conductive silver paint is used to produce the final version of the printed horn antenna.Measurements in an anechoic chamber demonstrate that the copper-coated version of the printed antenna has similar radiation performance as a commercial counterpart. An exponential horn antenna is made with decent performance, demonstrating the ease of production of more complexly shaped antennas. Our antennas can be produced within a couple of hours at a fraction of the price of commercial counterparts ($3 instead of $500-1500). This opens up new possibilities to quickly validate simulation results of new antenna designs. Further research focuses on the use of electroless plating to obtain more homogeneous copper deposition on three-dimensional structures, as well as extending our methodologies to more complex geometries.

Properties of PLA-co-PBSu Copolymers Rapidly Synthesized by Reactive Processing

This work describes the synthesis of poly(lactic acid) by the ring-opening polymerization of L-lactide in the presence of oligo(butylene succinate) with two different molecular weights (Mn = 6100 and 16300 g/mol) as a macroinitiator during reactive processing. The macroinitiators were added in concentrations 1 wt%, 2.5 wt%, 5 wt%, 10 wt% and 15 wt% in respect to the L-lactide mass in the premix. The properties of the received copolymers were extensively studied with spectroscopic techniques, GPC, DSC, XRD, TGA as well as nanoindentation. Blocky copolymers were received with number average molecular weights ranging from 30 to 100 kg/mol, which decreased with increasing the PBSu content in the feed. The introduction of the flexible PBSu chains decreased the single glass transition detected, while DSC and XRD gave indications that both components crystallized in the copolymers with PBSu premix content > 5 wt%. Thermal stability was maintained and depended on the composition and molecular weight. Nanoindentation showed that despite the decreasing trend of hardness and elastic modulus with increasing PBSu content, the PLA-PBSu 2.5% copolymers had simultaneously higher elasticity modulus and strength compared to the other compositions, possibly because of a complementary effect of their high molecular weight and crystallinity. These copolymers were promising for production with continuous reactive extrusion, a novel, fast and economically viable method to commercially produce PLA-based polymers.

Correlation of Two Biodegradability Indices of PLA-Based Polymers under Thermophilic Aerobic Laboratory Conditions

The biodegradation of bioplastics is a topic of interest worldwide. This work aims to measure the biodegradability of five polylactic acid (PLA)-based bioplastics under aerobic, thermophilic laboratory conditions and correlate their weight loss with their CO2 generation over a 3-month period, as both are considered indexes of biodegradation. The experimental design was based on the simulation of composting conditions by placing the bioplastic samples mixed with compost in sealed glass vessels that were regularly opened. The results showed significant variability in biodegradation, as dry weight losses ranged from 15.1–99.7%, while CO2 generation ranged from 9.2–14.9 g C–CO2/kg dry mixture (bioplastic + inoculum) depending on the sample. Moreover, no significant correlation between the weight losses and the gross CO2 production was calculated (p = 0.656), indicating the importance of carefully selecting the methods to assess biodegradation potential. This lack of correlation also reveals that different pathways are likely involved during the biodegradation of bioplastics and that the weight loss alone cannot indicate the conversion of solid C to CO2. This work proposes the need to develop an optimal degradation index for bioplastics that would provide a better understanding of their biodegradability in composting reactors. This index should combine dry weight loss and CO2 generation to assess the biodegradation of bioplastics with high confidence.

Effect of Amorphousness Degrees and Intermolecular Interactions between Lithium Perchlorate (LiClO4) and Polylactic Acid (PLA) on the Conductivity PLA-Based Polymer Electrolyte Performance

Background: The polymer electrolyte membrane serves as a separator and electrolyte in an energy storage device. The structural properties of the host polymer electrolyte have a significant impact on the conductivity value. Objective: The purpose of this study is to investigate the effect of amorphousness and intermolecular interaction degrees between LiClO4 and PLA on the conductivity performance of prepared PLA- based polymer electrolyte film. Methods: The polymer electrolyte film of LiClO4-complexed PLA was prepared with various weight percentages of LiClO4 salt (10%, 20%, 30%, 40%, 50%, and 60%) in PLA by using a solution casting technique. Results: PLA with 50% LiClO4 had the highest degree of amorphousness and the highest percentage of interacting carbonyl groups, which resulted in the highest conductivity of 2.56 x 10-5 S cm-1. Conclusion: Finally, the optimum composition of LiClO4 for the amorphousness, interaction of carbonyl group and conductivity are obtained, which can be used for further research to improve the conductivity value to apply it into energy storage devices’ development.

Mineral-filled biopolyester coatings for paperboard packaging materials: barrier, sealability, convertability and biodegradability properties

Abstract Changing trends in packaging materials has been driven by increasing environmental awareness as well as legislation. In this context, paperboard-based packaging have become increasingly popular due to its bio-based origin, potential biodegradability and physical properties. However, conventional systems lack behind in barrier performance and heat sealability. Hence, the addition of functional layers have been considered as alternative solutions to this challenge. Here we propose a biodegradable PLA-based polymer coating filled with minerals (0–10 wt% loading), namely, talc, kaolin and calcium carbonate, all of which were used in surface application on uncoated folding box board. For this purpose, we used a pilot-scale extrusion unit that produced materials that were tested for key properties. We found that the presence of filler in the PLA layer improved both water vapor (up to 16 %) and oxygen (up to 56 %) barrier properties. Moreover, the main effect of the fillers was observed in heat sealability, which was improved via adhesion at low temperatures, resulting in full fiber tear. Cup forming was less effected by filler loading in the PLA coating while repulping tests indicated the presence of large flakes of the polymer coating in 1 %-consistency slurries. Finally, biodegradability was slightly delayed in filler-containing samples (biodegradation within 10–60 days), most likely due to the nucleating effect of the fillers. Nevertheless, all the samples can be classified as biodegradable. Overall, our results represent a step forward in scale-up adoption of PLA-based coatings most useful in the development of packaging materials.

Stiff-Elongated Balance of PLA-Based Polymer Blends.

In this study, polymer blends with a mechanical property balance based on poly(lactic acid) (PLA), stiff polymer, and elongated polymer were developed. First, the binary blends PLA-elongated polymer [ethyl vinyl acetate (EVA) or polyethylene], or PLA-stiff polymer [polystyrene or poly(styrene-co-methyl methacrylate) (SMMA)] blends were studied using dynamic mechanic analysis (DMA) and analyzed using Minitab statistical software to determine the factors influencing the elongation or stiffness of the blends. Then, ternary blends such as elongation-poly(lactic acid)-stiff, were made from the binary blends that presented optimal performance. In addition, three blends [EVA–PLA–SMMA (EPS)] were elaborated by studying the mixing time (5, 15, and 15 min) and the added time of the SMMA (0, 0, and 10 min). Specifically, the mixing time for EPS 1, EPS 2, and EPS 3 is 5 min, 15 min, and 15 min (first EVA + PLA for 10 min, plus 5 min PLA-EVA and SMMA), respectively. Mechanical, thermal, rheological, and morphological properties of the blends were studied. According to DMA, the results show an increase in elongation at break (εb) and do not decrease the elastic module of poly(lactic acid). Nevertheless, EPS 3 excels in all properties, with an εb of 67% and modulus of elasticity similar to PLA. SMMA has a significant role as a compatibilizing agent and improves PLA processability.

Influence of lactide vs glycolide composition of poly (lactic-co-glycolic acid) polymers on encapsulation of hydrophobic molecules: molecular dynamics and formulation studies

The work demonstrates the preparation of PLGA (PLGA 50:50, PLGA 75:25) nanoparticles, to encapsulate a hydrophobic molecule (coumarin-6), using the microreactor-based continuous process. The formulations were characterized using dynamic light scattering and transmission electron microscopy to determine their size, homogeneity, zeta potential, and surface morphology. The resulting nanoparticles were safe to the CHO cells (≈80% cell survival), at the concentration of ≤600 µg/mL and were successfully taken up by the cells, as demonstrated using confocal microscopy. Moreover, imaging flow cytometry confirmed that the nanoparticles were internalized in 73.96% of the cells. Furthermore, molecular dynamics simulation and docking studies were carried out to explore the effect of polymer chain length of PLGA and lactide vs glycolide (LA:GA) ratio on their compatibility with the coumarin-6 molecules and to study the coiling and flexibility of PLGA in the presence of coumarin-6 molecules. Flory–Huggins interaction parameter (χ) was calculated for polymer chains of varying lengths and LA:GA ratio, with respect to coumarin-6. χ parameter increased with increase in polymer chain length, which indicated superior interaction of coumarin-6 with the smaller chains. Amongst all the polymeric systems, PLGA55 exhibited the strongest interaction with coumarin-6, for all the chain lengths, possibly because of their homogeneous spatial arrangements and superior binding energy. PLGA27 showed better compatibility compared to PLGA72 and PGA, whereas PLA-based polymers exhibited the least compatibility. Analysis of the radius of gyration of the polymer chains in the polymer–coumarin-6 complexes, at the end of molecular dynamics run, exhibited that the polymer chains displayed varying coiling behavior and flexibility, depending upon the relative concentrations of the polymer and coumarin-6. Factors like intra-chain interactions, spatial arrangement, inter-chain binding energies, and polymer–coumarin-6 compatibility also influenced the coiling and flexibility of polymer chains.

Towards More Sustainable Materials for Geo-Environmental Engineering: The Case of Geogrids

Plastic materials are widely used in geotechnical engineering, especially as geosynthetics. The use of plastic-based products involves serious environmental risks caused by their degradation. Innovative research has been focusing on biodegradable polymers of natural origin, especially on poly(lactic acid) (PLA), to reduce the use of plastics. This study aims to explore the potentiality of biopolymers for the production of geogrids, measuring the chemical and mechanical characteristics of raw materials and of prototype samples, similar to those available on the market. First, chemical composition and optical purity were determined by hydrogen nuclear magnetic resonance (1H-NMR) and polarimetry. Furthermore, samples of uniaxial and biaxial geogrids were custom-molded using a professional 3D printer. Mechanical properties were measured both on the filament and on the prototype geogrids. The maximum tensile resistance was 6.76 kN/m for the neat-PLA filament and 10.14 kN/m for uniaxial prototype geogrids produced with PLA-based polymer mixed with titanium dioxide. PLA-based materials showed higher tensile properties than polypropylene (PP), the most common petroleum derivative. Conversely, such biomaterials seem to be more brittle and with scarce elongation rate respect PP. Nonetheless, these results are encouraging and can support the use of PLA-based materials for innovative biodegradable geosynthetics production, especially if used in combination with live plants.

Tribological and Dynamical Mechanical Behavior of Prototyped PLA-Based Polymers.

It is essential to combine current state-of-the-art technologies such as additive manufacturing with current ecological needs. Due to the increasing demand for non-toxic biodegradable materials and products, human society has been searching for new materials. Consequently, it is compulsory to identify the qualities of these materials and their behavior when subjected to various external factors, to find their optimal solutions for application in various fields. This paper refers to the biodegradable Polylactic acid (PLA)-based filament (commercially known as Extrudr BDP (Biodegradable Plastic) Flax) compared with the biodegradable composite material PLA-lignin filament whose constituent’s trade name is Arboblend V2 Nature as a lignin base material and reinforcement with Extrudr BDP Pearl, a PLA based polymer, 3D printed by Fused Deposition Modeling technology. Certain mechanical properties (tensile strength, bending strength and DMA—Dynamic Mechanical Analysis) were also determined. The tribology behavior (friction coefficient and wear), the structure and the chemical composition of the biodegradable materials were investigated by SEM—Scanning Electron Microscopy, EDX—Energy Dispersive X-Ray Analysis, XRD—X-Ray Diffraction Analysis, FTIR—Fourier Transform Infrared Spectrometer and TGA—Thermogravimetric Analysis. The paper also refers to the influence of technological parameters on the 3D printed filaments made of Extrudr BDP Flax and the optimization those of technological parameters. The thermal behavior during the heating of the sample was analyzed by Differential scanning calorimetry (DSC). As a result of the carried-out research, we intend to recommend these biodegradable materials as possible substituents for plastics in as many fields of activity as possible.

Mechanical and Geometric Performance of PLA-Based Polymer Composites Processed by the Fused Filament Fabrication Additive Manufacturing Technique.

In this work, the effect of short carbon fibre (CF) on the mechanical and geometric properties of 3D printed polylactic acid (PLA) composite parts processed using the Fused Filament Fabrication (FFF) technique have been analysed. Tensile, flexural and interlaminar shear strength (ILSS) tests were performed to obtain the mechanical performance of the different samples. The surface quality and geometric accuracy of the printed specimens were also evaluated. Finally, Scanning Electron Microscope (SEM) images of the printed samples are analysed. The results revealed that the addition of carbon fibres effectively improved all assessed mechanical properties of PLA-CF composites as compared to the neat PLA. In particular, Flat PLA-CF samples showed an average increase in tensile performance of 47.1% for the tensile strength and 179.9% for the tensile stiffness in comparison to the neat PLA. From the flexural behaviour point of view, Flat PLA-CF samples revealed an increase in average flexural strength and stiffness of 89.75% and 230.95%, respectively in comparison to the neat PLA. Furthermore, PLA-CF samples depicted the best ILSS performance. In general, the use of short carbon fibre as reinforcement did not affect the dimensional accuracy of the PLA-CF samples, and even improved the surface roughness in certain cases, particularly in Flat and On-edge orientations.

Antimicrobial additives for poly(lactic acid) materials and their applications: current state and perspectives.

Poly(lactic acid)-based antimicrobial materials received considerable attention as promising systems to control microbial growth. The remarkable physicochemical properties of PLA such as renewability, biodegradability, and US Food and Drug Administration (FDA) approval for clinical use open up interesting perspectives for application in food packaging and biomedical materials. Nowadays, there is an increasing consumer demands for fresh, high-quality, and natural foods packaged with environmentally friendly materials that prolong the shelf life. The incorporation of antimicrobial agents into PLA-based polymers is likely to lead to the next generation of packaging materials. The development of antimicrobial PLA materials as a delivery system or coating for biomedical devices is also advantageous in order to reduce possible dose-dependent side effects and limit the phenomena of antibiotic resistance. This mini-review summarizes the most recent advances made in antimicrobial PLA-based polymers including their preparation, biocidal action, and applications. It also highlights the potential of PLA systems as efficient stabilizers-carriers of various kinds of antimicrobial additives including essential oils and other natural compounds, active particles and nanoparticles, and conventional and synthetic molecules.

Assembling copper nanowires at the interface and in discrete phases in PLA-based polymer blends

This work examines the effects of kinetic parameters on the assembly of copper nanowires (CuNWs) in discrete phases and at the interface in two distinct blend systems: a high interfacial tension blend of poly(lactic acid), PLA, /low density polyethylene (LDPE) and a low interfacial tension blend of PLA/poly(butylene adipate-co-terephthalate), PBAT. CuNWs were synthesized through electrodeposition in a porous alumina oxide template. Considering the surface polarity of polymer melts and the hydrophilicity of the surface of CuNWs, the particles should be located in the more polar phase (PLA in PLA/LDPE or PBAT in PLA/PBAT). TEM images confirm that when CuNWs are initially premixed with the more polar phase, they remain in that phase in a stable fashion irrespective of the interfacial tension of the system. However, when the particles are premixed with the less polar phase, to investigate kinetic effects, different behaviors are observed; in PLA/LDPE blends, CuNWs partition between both phases, while in PLA/PBAT blends, CuNWs assemble at the interface and in the less polar PLA phase. The effects of mixing time and shear rate on these phenomena are examined, and importantly, for the low interfacial tension PLA/PBAT blend, it is shown that CuNWs can be assembled in a stable fashion at the interface. The mechanism of interfacial assembly of these cylindrically shaped CuNWs in PLA/PBAT is the result of enhanced bulk migration in the less polar PLA phase and slow migration rate across the interface.

Conductivity and Microstructure Study of PLA-Based Polymer Electrolyte Salted With Lithium Perchloride, LiClO4

Conductivity and Microstructure Study of PLA-Based Polymer Electrolyte Salted With Lithium Perchloride, LiClO4

Design and thermoregulation of a new microextrusion dispense head for 3D-plotting of thermally sensitive thermoplastics

Three-dimensional plotting of micro-extruded filaments is a promising method for the manufacture of porous structures in thermoplastic polymers. However, it has been noted that conventional dispense head systems for this microextrusion are unsuitable for the reliable processing of thermally sensitive polymers like poly(lactic acid) (PLA): the batch polymer remains in the molten state prior to processing and it will degrade under this thermal load, leading to polymer chain reduction. Therefore, a new dispense head system was developed which thermally separates a cold material supply zone from the hot extrusion zone and allows for the processing of PLA-based polymers without severe degradation. This manuscript discusses the design of the new dispense head and compares its thermoregulation with that of a conventional system by means of finite element modeling and infrared imaging. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Conjugation of Bioactive Groups to Poly(lactic acid) and Poly[(lactic acid)‐co‐(glycolic acid)] Films

A novel PLA-based polymer containing reactive pendent ketone or hydroxyl groups was synthesized by the copolymerization of L-lactide with epsilon-caprolactone-based monomers. The polymer was activated with NPC, resulting in an amine-reactive polymer which was then cast into thin polymeric films, either alone or as part of a blend with PLGA, before immersion into a solution of the cell adhesion peptide GRGDS in PBS buffer allowed for conjugation of GRGDS to the film surfaces. Subsequent 3T3 fibroblast cell adhesion studies demonstrated an increase in cellular adhesion and spreading over films cast from unmodified PLGA. Hence the new polymer can be used to obtain covalent linkage of amine-containing molecules to polymer surfaces.

Future directions for the research and development of polyesters: From high-performance to environmentally friendly

Abstract We discuss the future directions for the research and development of polyester-based materials. In the discussion of polyesters as industrial materials, one direction is the development of high-performance materials. Poly(ethylene terephthalate) (PET), known as one of the most important polyesters, was developed early in the 1940s. We discuss two approaches to the development of high-performance materials suitable for injection-molding applications using PET units. The first approach is development of high-performance materials by copolymerization with bibenzoic acid (BB), which has a rigid structure, and the second approach is development of liquid-crystal polyesters (LCPs) with superior thermal resistance and excellent flowability using PET units. The other future direction for research and development is the targeting of environmentally friendly materials. Poly(lactic acid) (PLA), derived from bio-based materials, is a very important material because it can realize the carbon neutral cycles. Nevertheless, the practical properties of PLA itself are unsatisfactory compared to other plastics derived from fossil resources. We have developed PLA-based polymer alloys with various practical properties by utilizing a newly developed nanoalloy technology.

High-Performance Microtiter Plates for Immunosorbent Assays Made of Renewable Resources: Polylactic Acid Biopolymer as a Substitute for Synthetic Polystyrene

Most immunoassays are based on microtiter plates with conventional polystyrene (PS) as a solid support. PS is produced from crude oil. The production of PS plates consumes several hundred thousands tons of valuable raw material of limited supply. Also, disposing of PS plates by incineration produces a complex mixture of pollutants including dioxins and polycyclic aromatic hydrocarbons (1), and it adds excess CO2 to the atmosphere. In contrast, biopolymers such as polylactic acids (PLAs) are produced from renewable resources; they are biodegradable and their CO2 balance is neutral. PLA-based polymers have successfully replaced synthetic polymers in several applications, including some recent applications in immunology (2)(3). For the development of a PLA formula suitable as a matrix for immunoassays, the physical properties and surface characteristics of the polymer had to be improved for the present study. Surface characteristics are affected by factors such as monomer content, the nature and concentration of various additives, and molding and releasing conditions. Moreover, lot-to-lot reproducibility is affected by industrial fermentation and extraction procedures. For this study, the injection-molding process commonly used for PS was adapted to the PLA polymer to produce an experimental batch of 96-well microtiter plates from suitable PLA formulations. The performance of these plates in an ELISA was compared with conventional commercial PS plates. We used recombinant measles virus hemagglutinin protein (H-ELISA) as antigen for the detection of measles-specific IgG (4)(5)(6). We analyzed a panel of 426 human sera using 96-well prototype microtiter plates made of PLA. The procedure was applied essentially as described (5). All study participants or their parents gave informed consent. Results were compared with those obtained with the same antigen and commercial PS Maxisorp microtiter plates (NUNC). Statistical analysis of data was performed with SigmaStat software (Jandel Scientific). A z …