[en] In an increasingly environmentally conscious society, there is a need to reduce the consumption and environmental impact of the non-renewable high-performance polymers used in today's life due to their versatility and better properties than other materials such as mechanical and thermal. In this context, in this Master's thesis materials composed of the thermoplastic elastomer called styrene-b- (ethylene-co-butylene)-b-styrene (SEBS) and a renowable filler agent called cellulose were developed with the intention of maintaining, and even improving, its most significant properties for potential applications such as the automotive industry and sensors. Cellulose was selected because of its great interest in the industrial field caused by different reasons: it is a natural source and, also, considerably reduces the production cost despite the fact that it generally contributes to the deterioration of certain properties. This results in the search for a balance between all these qualities. In addition, in polymer blends it is important to consider their chemical nature, which must be similar. Because of their characteristics: SEBS is hydrophobic and cellulose hydrophilic, one of the two materials must be modified. Therefore, two types of modifications were studied: cellulose derivatives with apolar groups to be similar to apolar SEBS and the maleic anhydride grafted SEBS (SEBS-g-MA) to increase its polarity. Once the most suitable materials were selected, a series of SEBS and SEBS-g-MA based films were prepared in which the different celluloses were incorporated with different concentrations, and a study of the morphological, structural, mechanical, thermal and electrical properties was carried out using various techniques: Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), tensile testing, Differential Scanning Calorimetry (DSC), Thermogravimetryc analysis (TGA) and dielectric measurements. This made it possible to identify which cellulose precursors and charge contents are the most suitable and interesting from the SEBS applicability point of view. In the morphological characterisation, the immiscibility of the materials was observed, as well as the existence of voids between the filler and the matrix, becoming more noticeable with the increasing of the filler agent content. This caused a decrease in the mechanical properties of the blends films compared to the pure copolymer film due to the lower stress transfer, although, depending on the materials, these properties loss is of different degree. Regarding the thermal properties, the immiscibility was reflected by the occurrence of each characteristic temperature with almost no change. Thermal stability also decreased due to the introduction of the biopolymer with lower resistance to degradation. However, the filling agent caused a positive effect on the electrical properties so that the conductivity increased. In the case of SEBS and ethylcellulose blends, since the decrease in elongation at break and Young's modulus compared to the other films was minor, while the electrical properties were improved, these blends were concluded to be the most promising. Finally, with the idea of obtaining a sustainable material with similar properties to commercial EC, the aim was to extract cellulose from agricultural waste such as poplar and functionalise it by adding bromoethane. The extraction and functionalisation was followed using TGA and FTIR techniques in order to confirm that the desired product was obtained. These techniques established that parameters such as the concentration of sodium hydroxide and temperature not only help the method but also degrade the cellulose, so it is necessary to deal with different parameters until the product is obtained with a viable yield.

[eu] Ingurumenaz gero eta kontzientziatuago dagoen gizarte honetan, errendimendu handiko polimero ez- berriztagarrien kontsumoa eta ingurumen-inpaktua murrizteko beharra dago. Izan ere, gaur egungo bizitzan hain erabiliak diren polimero ez-berriztagarri hauek, aldakortasun handia dute eta beste materialen aldean propietate hobeak dituzte, hala nola mekanikoak eta termikoak. Testuinguru honetan, Master Lan honetan, elastomero termoplastiko-estireno-b-(etileno-ko-butileno)-b- estirenoaz (SEBS) jatorri naturaleko betegarri batekin osatutako materialak garatu ziren. Zelulosa hautatu zen betegarri bezala. Izan ere, zelulosak interes handia du industria-eremuan, jatorri naturalekoa baita, eta, gainera, ekoizpen-kostua murrizten du eta. Nahiz eta horrela izan, osagarri honek, interes handiko propietate batzuk murriztu ditzake. Horren ondorioz, ezaugarri horien guztien arteko oreka bilatzen da. Gainera, polimeroen propietateak kontuan hartu behar izan ziren, antzekoak izan behar dira eta nahasketak egiteko orduan. Testuinguru horretan, SEBS hidrofobikoa eta zelulosa hidrofilikoa direnez, bi materialetako bat aldatu egin behar izan zen. Beraz, bi aldaketa mota aztertu ziren: zelulosaren deribatuak apolar taldeekin SEBS apolarra eta SEBS anhidrido maleikoarekin (SEBS- g-MA) funtzionalizatua antzekoak izateko, polaritatea handitzeko. Material egokienak hautatu ondoren, SEBS eta SEBS-g-MA oinarri hartuta hainbat film prestatu ziren. Horietan, zelulosa desberdinak nahastu ziren, kontzentrazio desberdinekin. Propietate morfologiko, mekaniko, termiko eta elektrikoen azterketa egin zen, ondorengo teknikak erabiliz: Mikroskopia Elektronikoa (SEM), Fourier Transformatu Infragorrien Espektroskopia (FTIR), trakzio-probak, Eskanetze Kalorimetria Diferentziala (DSC), Termogravimetria (TGA) eta neurketa dielektrikoak. Horri esker, SEBSaren aplikagarritasunaren ikuspegitik, zelulosa aitzindari propietateak eta karga edukiak kontuan hartuta, interesgarrienak identifikatu ahal izan ziren. Karakterizazio morfologikoetan materialen immiszibilitatea ikusi zen eta betelanaren eta matrizearen artako hutsuneak ere. Hustune hauek nabarmenagoak bihurtzen ziren osagarrien edukiak gehienenduz. Horrek nahasketen filmen propietate mekanikoak murriztea eragin zuen; kopolimero puruaren filmarekin alderatuta, tentsio- transferentzia txikiagoa zen. Propietate termikoei dagokienez, inmiszibilitatea konponente bakoitzaren tenperatura bereizgarrien agerpenarekin islatu zen, ia aldaketarik gabe. Egonkortasun termikoak ere murriztu egin zen, degradazioarekiko erresistentzia txikiago zuen biopolimeroa sartu zelako. Hala ere, betegarri agenteak eragin positiboa izan zuen propietate elektrikoetan eroankortasuna areagotu egin zuelako. SEBS eta etilzelulosa (EC) sistemaren kasuan, haustura- elongazioaren eta Youngen moduluaren murrizketa aurkeztu zuen gainerako filmekin alderatuta nahiz eta garrantzi gutxiagokoa izan. Propietate elektrikoak hobetu egin zirenez, nahaste horiek etorkizun handienekoak zirela ondorioztatu zen. Azkenik, EC komertzialaren antzeko propietateak dituen material jasangarri bat lortzeko asmoz, nekazaritzako hondakinetatik (makala, esaterako) zelulosa ateratzen saiatu zen, bromoetanoa erabiliz funtzionalizatu ahal izateko. Erauzketa eta funtzionalizazioa TGA eta FTIR tekniken bidez egin zen, nahi zen produktua lortu zela baieztatzeko. Horien bidez zenbait parametro kontuan hartu behar zirela baieztatu zen. Sodio hidroxidoaren kontzentrazioa eta tenperatura nahiz eta prozesua lagundu, zelulosaren degradazioa eragin zuten. Hori kontuan hartuta, parametro desberdinekin egin beharko litzateke probak, produktua etekin bideragarriarekin lortu ahal izateko.