Textiles made from natural sources, such as cotton and flax, have advantages over those made of synthetic fibers in terms of sustainability. Unlike major synthetic fibers that have a negative impact on the environment due to poor biodegradability, cotton cellulose is a renewable material.Cotton cellulose fibers exhibit various attractive characteristics such as softness and inexpensiveness. Cellulosic textiles can be easily wetted, since the structure contains a large amount of hydrophilic hydroxyl groups, and when water repellency is needed, this is a disadvantage. Currently, paraffin waxes or fluorinated silanes are used to achieve hydrophobicity, but this contradicts the concept of green chemistry since these chemicals are not biodegradable. The use of bio-based materials like forest residues or side-streams from forest product industries might be a good alternative, since this not only decreases the pressure on the environment but can also increase the value of these renewable resources.Betulin is a hydrophobic extractive present in the outer bark of birch trees (Betula verrucosa). Nowadays, the birch bark containing betulin generated in the paper industry is disposed of by incineration as a solid fuel to provide energy, but this application is not highly valuable and this motivates us to see whether betulin can be used as a hydrophobe to prepare waterproof cellulosic textiles. Methods of dip-coating, film compression molding and grafting were performed to build “betulin-cellulosic textile system” to render the textile with hydrophobicity and other functions. The textile impregnated in a solution of betulin-based copolymer exhibited a contact angle of 151°, which indicated that superhydrophobicity can be reached. AATCC water spray test results showed that cellulosic textile coated with betulin-based film had a water repellency of 80, which is the third highest class according to the rating standards. Betulin-grafted textiles were also prepared and showed a static water contact angle of 136°, and an antibacterial property with a bacterial removal of 99%.This thesis proposes that betulin can be used as a green alternative in functional material preparation. By developing betulin, a more value-added application rather than incineration can be achieved.

Cellulosa, vilken är huvudkomponenten i växter förekommer rikligt i naturen, både på land och i havet. Cellulosabaserade material har i tusentals år använts av människan för dagliga förnödenheter som bränsle och konstruktionsmaterial. Cellulosa isolerades först av den franske forskaren Anselme Payen 1838. I det moderna samhället har applikationerna av cellulosa blivit mer omfattande i och med mer kunskap om cellulosans kemi, vilket även resulterat i modifiering av dess struktur och därmed produkter med nya egenskaper vilka kan möta dagens nya krav. I denna avhandling har kunskap om hur cellulosan kan modifieras, speciellt med avseende på att öka hydrofobiciteten, dvs att minska förmågan att absorbera vatten samt att öka kompabiliteten i kompositmaterial.Cellulosafibrer används ofta som förstärkning i kompositmaterial. I detta arbete användes en ny typ av mikrocellulosa – ett cellulosaderivat, cellulosaoxalat (COX), för framställning av polymersammansättningar. COX hydrofoberades först av maleaterad polypropylen (MAPP) eller oljesyra för att erhålla en bättre kompatibilitet med den hydrofoba matrisen av polypropylen (PP). Det konstaterades att en komposit bestående av 60% PP och 40% MAPP-hydrofoberad COX visade 16% högre draghållfasthet och 106% högre Youngs modul än ren PP. Vid användning av oljesyra för hydrofobering av COX är det möjligt att undvika att använda toxiska katalysatorer för att fullborda förestringen mellan COX och oljesyra, vilket kan leda till en mer miljövänlig process.På samma sätt användes naturligt förekommande föreningar med syftet att framställa hydrofoba cellulosabaserade textilier. Betulin, en naturprodukt isolerad från björkens bark, användes för att modifiera vätbarheten hos cellulosabaserade textilier med tre olika metoder. Textilfibrer modifierades genom att de behandlades i en betulinlösning varefter de torkades och kunde därefter uppvisa en statisk vattenkontaktvinkel (SWCA) på 153°. Därefter ytbehandlades textilfibrer med en betulinbaserad film, vilken uppvisade ett vattenavvisande värde på 80 enligt ett standardtest från American Association of Textile Chemists and Colorists (AATCC). Framställning av betulin-ympad cellulosabaserad textil, visade inte bara hydrofoba egenskaper (SWCA upp till 136°) utan även antibakteriella egenskaper med mer än 99% reduktion av bakterier.Baserat på resultaten från denna avhandling öppnas möjligheter att modifiera cellulosa och erhålla vattenavstötande eller mer kompatibla material för framställning av kompositmaterial. Ökade möjligheter att använda biprodukter, t.ex. betulin och oljesyra, från de skogsindustriella processerna i ett bioraffinaderiperspektiv, kan även bidra till mer hållbara och miljövänliga processer och ökade ekonomiska värden.

As a main structural component of plants, cellulose is naturally abundant and widely distributed on earth. Although the chemical formula of cellulose was determined in 1838, human beings have been using cellulose to produce daily necessities, such as textiles and paper, for thousands of years. In modern society, the applications of cellulose have expanded considerably as the understanding of the chemistry of cellulose has increased, and researchers have been able to alter the structure of cellulose to obtain new properties to meet new requirements. With this strategy of structure alteration, this work demonstrated new methods of hydrophobization of cellulose to prepare emerging materials with new or improved properties.Cellulose is commonly used for reinforcement in composites. In this study, a new type of microcellulose, cellulose oxalate (COX), was used to prepare polymeric composites. COX was first hydrophobized by maleated polypropylene (MAPP) or oleic acid to obtain better compatibility with the hydrophobic matrix of polypropylene (PP). It was found that a composite consisting of 60% PP and 40% MAPP-hydrophobized COX had a 16% higher tensile strength and a 106% higher Young’s modulus than neat PP. When oleic acid was used to hydrophobize COX, it was possible to avoid using toxic catalysts to complete the esterification between COX and oleic acid. This fact makes the process environmentally friendly.Similarly, considering environmental protection, natural compounds were used to prepare hydrophobic cellulosic textiles. Betulin, a kind of wood extract and by-product in the forestry industry, was used to modify the wettability of cellulosic textiles. The textiles underwent a dip-dry-cure process from a betulin solution had a static water contact angle (SWCA) of 153°. Textiles coated by a betulin-based film exhibited a water-repellency score of 80 according to a standard test from the American Association of Textile Chemists and Colorists (AATCC). Betulin-grafted cotton textiles were also prepared, and such textiles showed not only hydrophobic properties (SWCA up to 136°) but also antibacterial properties, with bacterial removal of more than 99%.This thesis proposes that hydrophobized cellulosic materials can be used in various fields, both related and unrelated to waterproof applications. Furthermore, by-products in the forestry industry, such as betulin and oleic acid, are advocated for use because of their biodegradability and value.