Abstract Replacing the plastics in packaging applications with bio based and biodegradable cellulosic materials, especially all cellulose composites, would be a sustainable alternative. The main problem would be the non ecological and non economic nature of the processing required by all cellulose composites due to the use of toxic and expensive chemicals such as cellulose solvents. In addition, the raw materials typically studied for all cellulose composites have been highly specialized cellulosic pulps. This thesis therefore explores the possibility of using NaOH/urea as a cellulose solvent together with commercially available chemical pulps from the paper and board industry for the production of sustainable all cellulose composites materials. Furthermore, the effect of calendering and fibre orientation was investigated. The methods used for characterizing the materials were tensile strength measurements, X Ray diffraction, imaging and the short compression strength test. In connection with the X Ray diffraction measurements a method for evaluating the crystallinity of cellulose was modified from the literature and partly automated. The results show that NaOH/urea is a suitable solvent for producing all cellulose composites within a significant shorter time than reported in the literature. In addition, the tensile strength of the paper used for this purpose could be increased up to ten times and it is shown that the dissolution of cellulose fibres was indeed only partial. The efficiency of the treatment is nevertheless greatly dependent on the pulps used and their hemicellulose and lignin content. Further post-processing in the form of calendering is not recommended because it weakens the composites. / Tiivistelmä Fossiilisien muovien korvaaminen biopohjaisilla ja -hajoavilla materiaaleilla pakkausteollisuuden sovelluksissa on ympäristön kannalta kestävä vaihtoehto, varsinkin kun materiaalina käytetään itselujittuva selluloosakomposiitti (eng. all-cellulose composite). Tämän materiaalin teollinen valmistus ei kuitenkaan ole vielä ollut taloudellisesti kannattavaa eikä ympäristöystävällistä, koska selluloosan liuotukseen tarvitaan kalliita ja ympäristölle haitallisia kemikaaleja. Lisäksi raaka-aineena on aiemmin käytetty kalliita erikoisselluloosakuituja. Edellä mainituista syistä tässä väitöskirjatyössä tutkitaan itselujittuvien selluloosakomposiittien valmistusta käyttäen raaka-aineina kaupallisesti saatavilla olevia selluloosakuituja ja niiden liuottimena NaOH/urean vesiliuosta. Tämän liuottimen etuja ovat vähäinen myrkyllisyys, edullisuus ja riittävien määrien saatavuus teolliseen tuotantoon. Lisäksi työssä tutkitaan kalanteroinnin ja kuituorientaation vaikutusta komposiitin ominaisuuksiin. Käytettyjä analyysimenetelmiä ovat röntgendiffraktio, elektronimikroskoopilla kuvantaminen ja erityyppiset mekaaniset testit. Röntgendiffraktiomittausten tulosten arvioinnissa käytetään aiemmin raportoidusta menetelmästä kehitettyä osin automatisoitua selluloosan kiteisyyden määrittämisen menetelmää. Tulosten perusteella voidaan sanoa, että NaOH/urea on sopiva liuotin itselujittuvien selluloosakomposiittien valmistukseen ja sillä prosessia voidaan nopeuttaa huomattavasti muihin raportoituihin menetelmiin verrattuna. Raaka-aineena käytetyn paperin vetolujuus parani liuotinkäsittelyllä jopa kymmenkertaiseksi. Liuotinkäsittelyn tehokkuus riippui paljon käytettyjen selluloosakuitujen tyypistä ja niiden hemiselluloosa- ja ligniinipitoisuuksista.

Biobased all-cellulose composites (ACCs), in which the matrix and the reinforcement are made out of the same material, have gained a noticeable increased attention in recent years. Their successful application would solve the commonly faced challenges with natural fiber composites regarding their chemical antipathy between the hydrophilic fiber and the usually hydrophobic polymer matrix, while still keeping the advantages of being environmental friendly. Moreover, the use of man-made continuous regenerated cellulose fibers for this purpose could result in unidirectional all-cellulose composites with excellent mechanical properties. In this study, a new processing technique for unidirectional all-cellulose composites, reinforced with continuous regenerated cellulose nanocomposite fibers, has been developed, where the fibers are wound directly after the coagulation bath and then welded together while still being swelled in order to form all-cellulose composite sheets without the need of adding any additional solvent or chemicals. Scanning electron microscopy and tensile testing were used to investigate and compare the microstructure and mechanical properties, of a reference material without nanoreinforced fibers and two variants reinforced with 2 % cellulose nanocrystals (CNCs) and 2 % halloysite nanotubes (HNTs). Analysis revealed that transparent all-cellulose composites with a high compaction degree and minimal warpage during shrinkage, showing high mechanical properties could be made. However, the addition of nanoreinforcements did not lead to any improvements.

Today’s consumption of textiles generates a large volume of textile waste. Therefore, it is needed to find solutions to re-use the textile waste rather recycling fibers into new fibers. Research using pre- and post-consumer textiles in composites is ongoing and an interesting direction. This thesis reports the recycling of discharged cellulose containing textiles by production of all-cellulose composites (ACCs). ACCs are composites consisting entirely of cellulose. ACCs from discarded denim and polycotton hospital sheets (PCO) were successfully produced with partial dissolution and two-step method. Discarded denim fabrics with 100% cotton (CO) and blend material (BCO) was sorted and shredded into fibers, then made into nonwovens by needle punching. The produced nonwoven laminates and intact hospital sheets were used as the reinforcement in the composites while dissolved cellulose in an ionic liquid (IL), 1-butyl-3-methyl imidazolium acetate ([BMIM][Ac]), was used as the matrix phase. The matrix is then regenerated by removal of the [BMIM][Ac] by washing to form the composite. The washed-out [BMIM][Ac] was collected and recycled in order to study the effect of its reusing as recycled cellulose solvent on mechanical properties of ACCs. Combinations of the different methods, materials and solvents were studied. The mechanical properties – tensile, flexural and impact properties and the void content of the produced composites were deter-mined. Microscopic analysis was done to study the cross-section of the composites. It could be concluded that the achieved values for the mechanical properties can be compared with ACCs found in literature. The results from the research implies that it is possible to find a new purpose for recycled textiles in the form of composites. With this approach, it is possible to avoid unnecessary disposal of textiles containing cellulose.