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Conventional plastics have been used for decades in a diverse range of applications, however, many are resistant to degradation, leading to environmental pollution and their manufacture is dependent on non-renewable fossil fuels. Therefore, there has been an increasing need for eco-friendly biodegradable materials from renewable resources. Poly(lactic acid) (PLA) is a compostable polyester with a hydrolysable backbone that is susceptible to biodegradation and produced from renewable feedstocks. PLA has mechanical qualities comparable to non-biodegradable plastics, and currently is commercialized as food-packaging polymer for short shelf-life products. However, while PLA hydrolysis at elevated temperatures proceeds abiotically, ultimately releasing lactic acid and short chain oligomers, the role of microorganisms is unclear. Since PLA short-shelf life products are disposed after use, understanding the role of microorganisms and the effect of degradation on microbial populations in the environment is important. Therefore, the aims of this research was to (a) determine the relative importance of biotic and abiotic factors on PLA degradation; (b) to isolate putative fungal PLA degraders from the surface of PLA when buried in compost or soil and to test their ability to degrade PLA; (c) to assess the impact of PLA degradation on fungal communities when entering compost systems. The roles of abiotic and biotic factors in the degradation of high molecular weight PLA were investigated by comparing degradation rates in compost, soil and sterile water at temperatures of 25°, 37°, 45°, 50° and 55°C. Tensile strength loss and molecular weight decline of PLA in microorganism-rich compost and soil were greater than chemical hydrolysis in sterile water at elevated temperatures (above 45°C) indicating microorganisms can directly enhance PLA degradation. Since extensive fungal growth was observed on the surface of PLA when buried in compost and soil, putative fungal PLA degraders were isolated from PLA surface and their community profile on PLA surface was compared with the compost and soil community with a molecular method, terminal restriction fragment polymorphism (TRFLP). Among the identified fungi, Thermomyces lanuginosus was the dominant isolate recovered and shown to enhance PLA degradation in compost at 50°C. The fungal community profile on PLA surface was different than the fungal profile in compost and soil suggesting enrichment for PLA degraders on the surface of PLA. In order to determine the impact of PLA degradation on the fungal compost community, two different high molecular weight PLA sources, films and granules were buried in compost at 10%, 25% and 50% (w/w) concentration for 4 months at 25°C and 50°C and the community profile analysed by TRFLP and pyrosequencing. TRFLP revealed that when PLA did not degrade, the fungal community shifted back toward the initial compost community profile, however, when PLA degraded to its monomers releasing lactic acid at 50°C at a concentration of 50% (w/w) it changed the fungal community profile and decreased the fungal diversity. Pyrosequencing revealed that the presence of PLA enriched for Thermomyces in the compost population over time.

Nowadays, plastic waste poses one of the greatest risks to the environment. Plastics affect the environment at all stages of their life cycle. Bioplastics have become widely used as a substitute for conventional plastics, without detailed examination of their behavior in real environmental conditions. As a result, it is assumed that they can accumulate in the environment and the question arose as to how to identify them. The main goal of this thesis is to develop a method based on sample pyrolysis that is suitable for the identification and determination of the amount of PLA microplastics in soil and other solid matrices. Three types of soils and sludge were used for analysis. These matrices were spiked to obtain concentration ranges 0,2% - 5,0%. The pyrolysis resulted in evolution of gases with the signals m/z 29, 43 and 44, witch originated from PLA and are suitable for qualitative and quantitative analysis. Analysis of PLA in sludge was more complicated due to similarity of gases evolved from pure matrices. We tested three approaches based on analysis of signal´s peak areas, intensities and temperatures of gas evolution. While the first approach failed, the last two approaches appeared to be promising for qualitative and quantitative analysis of PLA in the sludge. Several methods suitable for qualitative and quantitative analysis of even very small amounts of PLA in soils and sludge have also been designed/developed. These methods were based on analysis of the composition and dynamics of the released gases and the characterisctic degradation temperatures.

Dans le contexte actuel, où la préservation des ressources et le développement durable sont devenus des enjeux importants de ce siècle, la production de matériaux tant performants que respectueux de l’environnement est devenue indispensable. Ainsi, ce travail de thèse porte sur l’élaboration de matrices poreuses de biopolymères en utilisant la technologie CO2 supercritique (CO2-SC). L’utilisation du PLA permet de produire des matrices 100% biosourcées et biodégradables, alors que l’utilisation de CO2-SC permet de diminuer l’impact écologique des procédés de mise en forme. Dans un premier temps une étude paramétrique de la mise en forme de matrice de PLA par une méthode de séparation de phase thermique (TIPS) couplée à un séchage par CO2 a été réalisée. Elle a permis de produire des matrices microcellulaires de faible densité (entre 60 et 320 kg/m3) et aux propriétés structurales mécaniques modulables. L’ensemble du procédé a fait l’objet d’une analyse de cycle de vie et il a été démontré que l’utilisation du CO2-SC en remplacement de la lyophilisation a réduit d’entre 50 et 90% l’impact environnemental. Dans un second temps une étude in-situ de la séparation de phase par tomographie-X en rayonnement synchrotron a permis de mieux comprendre la mécanistique de notre procédé. Enfin, la dernière partie de ce travail a été consacré à la mise en forme de matrice de PLA sans solvant, en utilisant le CO2-SC comme agent gonflant. Les résultats obtenus ont servi à réaliser une étude comparative des deux procédés développés. / In the present context, where the preservation of resources and sustainable development became the main issues of this century, the production of more efficient and environmentally friendly materials is essential. Thus, this work deals with thedevelopment of biobased polymeric porous matrix using SC-CO2. The use of PLA makes it possible to produce 100% biosourced and biodegradable matrices, while the use of CO2-SC reduces the ecological impact of the shaping processes. In a first step, a parametric study of PLA matrix shaping by a thermal induced phase separation (TIPS) method coupled to CO2 drying was performed. Low density microcellular matrices were obtained with tunable structural and mechanical properties. The whole process was analyze by life cycle assessment and the results showed that SC-CO2 replacing freeze drying has reduced the environmental impact between 50 and 90%. Secondly, a phase separation in situ study by tomography-X synchrotron radiation tomography allowed us to better understand the mechanics of our process. Finally, the last part of this work was devoted to the implementation of a solvent free process, using SC-CO2 as a blowing agent. The results obtained were used to carry out a comparative study of the two processes developed.

Södra DuraPulp is a relatively new eco-composite, made from natural wood fibers and polylactic acid (PLA), which comes from corn starch. Until now, there are only few applications for DuraPulp, mainly in the area of design. To find new fields of application, more knowledge about its mechanical material properties are of great interest.This study deals with characterizing the mechanical properties of DuraPulp in an analytical way by means of micromechanical modelling and evaluation with help of Matlab. The mechanical properties for PLA were taken from scientific literature. Not all properties of the wood fibers could be found in literature (particularly Poisson’s ratios were unavailable). Therefore, they partly had to be assumed within reasonable boundaries. These assumptions are later validated regarding their influence on the final product.Figures and tables were used to present and compare the in- and out-of-plane E-Moduli, shear moduli and Poisson’s ratios of DuraPulp. The calculated in-plane E-Moduli were then compared to those obtained from an earlier study, where DuraPulp was tested in tension. The results showed that experimental and analytical values are very similar to each other. / Södra DuraPulp är en relativt ny eco-komposit, tillverkat av naturliga trä fibrer och polylactic syra som kommer från majsstärkelser. I dagsläget finns det få användningsområden för DuraPulp, huvudsakligen används det inom design. För att expandera användningsområdet behövs det mer kunskaper angående de mekaniska egenskaperna för materialet. Studien handlar om att karakterisera de mekaniska egenskaperna för DuraPulp på ett analytiskt sätt i form av mikro-mekanisk modellering och evaluering med hjälp av Matlab. De huvudsakliga mekaniska egenskaperna för PLA kunde hämtas från flera vetenskapliga källor, men de motsvarande mekaniska egenskaperna för fibrer kunde inte alla valideras. Delvis antogs dem i rimliga gränser och deras inverkan validerades med hjälp av en parameter studie.Figurer och tabeller användes för att presentera och jämföra in- och ut-plan E-Moduler, skjuvmoduler och tvärkontraktionstalen av DuraPulp. De beräknade in-plan E-modulerna för DuraPulp jämfördes med motsvarande E-moduler från en tidigare studie där DuraPulp genomgick dragtest. Resultatet visade att analytiska och experimentella värden överensstämmer bra med varandra.

Η παρούσα εργασία αναφέρεται σε νανοσύνθετα βιο-αποικοδομήσιμα οργανικά πολυμερή, με κύρια πολυμερική μήτρα το πολυγαλακτικό οξύ (PLA). Η ερευνητική κοινότητα δείχνει μεγάλο ενδιαφέρον για την χρήση και την ανάπτυξη των βιοδιασπώμενων πολυμερών. Με αυτά αναμένεται να μειωθούν οι επιπτώσεις των πλαστικών υλικών στο περιβάλλον. Στην βιβλιογραφία υπάρχει μεγάλη δραστηριότητα για την ανάλυση του ανθρακικού αποτυπώματος των διασπώμενων πολυμερών. Επίσης, η ερευνητική κοινότητα εστιάζει την προσοχή της και στην μελέτη των ιδιοτήτων των βιοδιασπώμενων πολυμερών. Στο μέλλον αναμένεται να μπορέσουν να χρησιμοποιηθούν σε τομείς που τώρα, λόγω των περιορισμένων μήχανικών τους ιδιοτήτων δεν εφαρμόζονται. Βασικό αντικείμενο μελέτης στην εργασία αυτή ήταν η αλληλεπίδραση οργανικών σφαιρικών νανοσωματιδίων από πολυ(οξικό βινυλεστέρα) με το πολυγαλακτικό οξυ. Για να δημιουργηθεί μια εικόνα της συμπεριφοράς του πολυγαλκατικού οξέος σαν πολυμερική μήτρα, συντέθηκαν και αξιολογήθηκαν μίγματα απο ομοπολυμερή πολυ(οξικού βινυλεστέρα) (PVAc) πολυβινυλικης αλκοόλης (PVOH) και πολυαμιδίου (PA11, PA12). Ύστερα παρασκευάσθηκαν νανοσύνθετα φιλμ απο νανοσωματίδια δικτυωμένου πολυστυρολίου (NPs-PS), δικτυωμένου πολυ(οξικού βινυλεστέρα) (NPs-PVAc) και νανοσωματίδια δικτυωμένης παλυ(βινυλικής αλκοόλης) (με βαθμούς υδρόλυσης H.D.: 100, 50, 48 και 38%). Εν συνεχεία, στην πολυμερική μήτρα απο PLA εισήχθησαν νανοδομές δικτυωμένου πολυ(στυρενοσουλφονικού δεκαέξυλου τριμεθυλαμμωνίου) (PSSAmC16-ΑΝ) σε διάφορες αναλογίες (1, 2, και 5%) και νανοδομημένα δίκτυα δικτυωμένου πολυστυρολίου (PS-NN). Τέλος οι μηχανικές ιδιότητες όλων των φιλμ αξιολογήθηκαν μέσω δοκιμής τάσης-εφελκυσμού και τα μορφολογικά τους χαρακτηριστικά μελετήθηκαν μέσω της ηλεκτρονιακής μικροσκοπίας σάρωσης SEM. / The scientific community shows great interest in the use and development of biodegradable polymers, due to their low impact on the environment. In literature there is plenty of research activity on the analysis of biodegradable polymers in comparison to the CO2 emission during the life cycle of polymer products. The carbon footprint of biodegradable polymers is far smaller than those of conventional polymers. The biodegradable materials are so desirable because these are expected to overcome significant problems such as environmental pollution, waste management issues which are created by plastics, as well as their oil dependence. Thus, the research community is focused on the study of the properties of biodegradable polymers and their potential use in applications where their design is mainly limited by the material's mechanical properties, such as modulus, strength and other characteristic properties of the behavior of the polymers (such as miscibility, optical transparency and barrier properties). In the present work blends of PLA with the homopolymers polystyrene (PS), polyvinyl acetate (PVAc) and polyamides (PA11, PA12) were made and the quality of the synthesized films was assessed. In a further step, spherical organic nanoparticles of PS, PVAc (either non-hydrolyzed or hydrolyzed with hydrolysis degree H.D.: 100, 50, 48 and 38%) as well as assymetric nanostructures of polystyrene sulfonate ammonium salt (PSSAmC16-AN) and PS-NN were incorporated into the PLA matrix in various percentages (1, 2, and 5%). Afterwards the mecahanical properties of the blends were evaluated by stress-strain measurements, whereas their morphological characteristics were tested through scanning electron microscopy (SEM).

Some mechanical properties of DuraPulp, a bio-based, bio-degradable composite made from polylactic acid (PLA) and pulp fibers, were determined. Focus was put on the conditions during productions whereby three different press times were studied. Additionally, two different material compositions (PLA to fiber ratios) were used. Uniaxial tensile tests with two different load rates, one and 50 mm/min, were performed. An increase in maximum strength and E-modulus of DuraPulp was observed by increasing the press time, while PLA content decreased the maximum strength and E modulus.

[ES] Este trabajo de investigación tiene como objetivo general el desarrollo de formulaciones sostenibles a base de ácido poliláctico (PLA) mediante la incorporación de resinas naturales, resina de colofonia y derivados de resina de colofonia como agentes modificadores. La génesis de la presente tesis doctoral parte del interés de evaluar el efecto de los derivados de colofonia en las propiedades del PLA, tras observar los efectos positivos generados por estos aditivos en polímeros biodegradables de almidón termoplástico (TPS). Al tener como punto de partida los efectos positivos de los derivados de colofonia en el TPS, sería fácil continua la evaluación de los mismos aditivos en el PLA. Sin embargo, como secuencia razonable se comenzó por analizar los efectos de la propia resina de colofonia, y un derivado simple, continuando posteriormente con el análisis de derivados más complejas. Para finalizar con el análisis de derivados de colofonia en las propiedades del PLA, se utilizó un derivado experimental con el doble de complejidad. Este es derivado de colofonia con aducto de anhídrido maleico. A diferencia de la resina de colofonia, los derivados de colofonia presentan mayor estabilidad térmica y mayor estabilidad frente a la oxidación al aire libre. La evaluación de los efectos de la resina de colofonia y sus derivados en las propiedades del PLA se realizaron en cuatro estudios, compilados a su vez en tres grupos. Como epilogo de la investigación, se evaluó la posibilidad de incorporar la resina natural de la flor de Clusia rosea al ácido polilactico. Esta flor es conocida como Copey o mamey silvestre, la cual es una planta endémica del caribe. La evaluación del efecto de esta resina en el PLA se realizó como estudio número cinco, dando lugar a un último grupo, número cuatro. ¿ Grupo 1, uso de resinas de colofonia y un derivado común (ambos de bajo peso molecular). o Primer estudio ¿ Grupo 2, uso de dos derivados de colofonia (de alto peso molecular). o Segundo estudio ¿ Grupo 3, uso de derivado de colofonia con aducto de anhídrido maleico. o Tercer estudio o Cuarto estudio ¿ Grupo 4, evaluación de resina natural de flor de Clusia rosea. o Quinto estudio El procesado de los materiales se realizó por incorporación directa de los derivados de colofonia, mediante extrusión fundido. A continuación, las mezclas extruidas fueron trituradas en forma de granza o pellet, para posteriormente producir probetas normalizadas de ensayo mediante inyección por moldeo, las cuales se utilizaron en la caracterización. / [CA] Aquest treball de recerca té com a objectiu general el desenvolupament de formulacions sostenibles a base d'àcid polilàctic (PLA) mitjançant la incorporació de resines naturals, resina de colofònia i derivats de resina de colofònia com a agents modificadors. La gènesi de la present tesi doctoral part de l'interés d'avaluar l'efecte dels derivats de colofònia en les propietats de l'àcid polilàctic, després d'observar els efectes positius generats per aquestos additius en polímers biodegradables de midó termoplàstic (TPS). En tindre com a punt de partida els efectes positius dels derivats de colofònia en el TPS, seria fàcil continuar l'avaluació dels mateixos additius en el PLA. No obstant això, com a seqüència raonable es va començar per analitzar els efectes de la pròpia resina de colofònia, i un derivat simple, continuant posteriorment amb l'anàlisi de derivats més complexos. Per a finalitzar amb l'anàlisi dels derivats de colofònia en les propietats del PLA, es va utilitzar un derivat experimental amb el doble de complexitat. Aquest és derivat de colofònia amb adducte d'anhídrid maleic. A diferència de la resina de colofònia, els derivats de colofònia presenten major estabilitat tèrmica i major estabilitat enfront de l'oxidació a l'aire lliure. L'avaluació dels efectes de la resina de colofònia i els seus derivats en les propietats del PLA es van realitzar en quatre estudis, compilats al seu torn en tres grups. Com epilogue de la investigació, es va avaluar la possibilitat d'incorporar la resina natural de la flor de Clusia rosea a l'àcid polilàctic. Aquesta flor és coneguda com Copey o mamey silvestre, la qual és una planta endèmica del caribe. L'avaluació de l'efecte d'aquesta resina en el PLA es va realitzar com a estudi número cinc, donant lloc a un últim grup, número quatre. ¿ Grup 1, ús de resines de colofònia i un derivat comú (tots dos de baix pes molecular). o Primer estudi ¿ Grup 2, ús de dos derivats de colofònia (d'alt pes molecular). o Segon estudi ¿ Grup 3, ús de derivat de colofònia amb adducte d'anhídrid maleic. o Tercer estudi o Quart estudi ¿ Grup 4, avaluació de resina natural de flor de Clusia rosea. o Cinqué estudi El processament dels materials es va realitzar per incorporació directa dels derivats de colofònia, mitjançant extrusió. A continuació, les mescles extruides van ser triturades en forma de gransa o pèl·let, per a posteriorment produir provetes normalitzades d'assaig mitjançant injecció per emotlament, les quals es van utilitzar en la caracterització. / [EN] This research aims to develop sustainable formulations based on polylactic acid (PLA) by incorporating natural resin, rosin resin, and rosin resin derivatives as modifying agents. The genesis of this doctoral thesis is based on the interest in evaluating the effect of rosin resin derivatives on the properties of polylactic acid after observing the positive results generated by these additives in biodegradable polymers of thermoplastic starch (TPS). Having as a starting point the positive effects of rosin resin derivatives in TPS, it would be easy to continue evaluating the same additives in PLA. However, as a proper sequence, the evaluations were initiated by analyzing the effects of the rosin resin and a simple derivative, then continuing to investigate more complex derivatives. To finish with the analysis of rosin resin derivatives in the properties of PLA, an experimental rosin resin derivative with twice the complexity was used. This is a rosin resin derivative with maleic anhydride adduct. Unlike rosin resin, rosin resin derivatives exhibit higher thermal and oxidation stability. The effects evaluation of rosin resin and its derivatives in the properties of PLA were carried out in four studies. They were compiled into three groups. As an epilogue to this research, the possibility of incorporating the natural resin of the Clusia rosea flower into polylactic acid was evaluated. This flower is called Copey or wild mamey, an endemic plant native to the Caribbean. This resin effect in the PLA was evaluated as study number five, giving rise to the last group, number four. ¿ Group 1, use of rosin resin and a common derivative (both of low molecular weight). ¿ First study ¿ Group 2, use of two rosin resin esters (high molecular weight). ¿ Second study ¿ Group 3, use of rosin reisn derivative with maleic anhydride adduct. ¿ Their study ¿ Fourth study Group 4, evaluation of the natural resin from the Clusia rosea flower. ¿ Fith study The material was processed by directly incorporating the rosin resin derivatives by melt extrusion. Subsequently, the extruded mixtures were crushed as pellet to produce normalized testing samples through injection molding. These testing samples were then used in the characterization. / Gracias a la Universitat Politècnica de València y al grupo de investigación DEMES por el apoyo a través del contrato predoctoral para la formación de personal investigador financiado por la estructura de investigación de la UPV – subprograma 2 (FPI-2018-S2-31946). Al Programa de Movilidad para estudiantes de doctorado de la Universitat Politècnica de València por la ayuda para “Estancias en Centros Extranjeros de Prestigio”. / Rosa Ramírez, HDL. (2023). Desarrollo de formulaciones de ácido poliláctico (PLA) basadas en la incorporación de derivados de la colofonia [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/194754

No description available.

Polylactic acid (PLA) is an aliphatic polyester, derived from sustainable natural sources that is biodegradable and can be industrially composted. This material has been in the spotlight recently due to its sustainability and properties. However it has been invented in 1932 by Carothers and then patented by DuPont in 1954 (Standau et al. 2019). The properties of this material though limit its use for applications mainly in the medical sector and in some cases single use packaging. In this research, PLA based blends with improved rheological and thermomechanical properties are investigated. The focus is based in proposing strategies in improving these properties based on commercial methods and processing techniques. In this work, commercial grade PLA has been blended with polycaprolactone (PCL) and polybutylene succinate (PBS) in binary and ternary formulations via twin screw extrusion. PCL has been known to act as an impact modifier for PLA, but to cause a corresponding reduction in strength. Results showed that the binary PLA blends containing PBS and PCL, had reduced viscosity, elastic modulus and strength, but increased strain at break and impact strength. Morphological and thermal analysis showed that the immiscibility of these additives with PLA caused these modifications. Incorporation of a small loading of PBS had a synergistic effect on the PLA-PCL blend properties. Miscibility was improved and enhanced mechanical properties were observed for a ternary blend containing 5wt% of both PBS and PCL compared to binary blends containing 10% of each additive. To increase heat resistance of PLA, the material’s crystallinity has to be increased. However PLA has a relatively slow crystallisation rate making it difficult and expensive to be used in commercial applications where heat resistance is needed. For this reason the chiral nature of PLA has been used to investigate the effect of stereochemistry of PLA in crystallisation. Optically pure PDLA was added to its enantiomer in small amounts (up to 15%) and the properties and crystallisation mechanism of these blends was investigated. Results showed that the addition of PDLA accelerated crystallinity and developed a stucture that increased heat resistance, melt strength and stiffness. Finally, a processing model of developing a fully stereocomplex PLA part based in commercial techniques is proposed. Injection moulded PLA showed even higher heat resistance without the need of further processing the product (increasing crystallinity). / Floreon