Paper materials are renewable and recyclable and are often used for packaging applications, e.g., as in corrugated fiberboard boxes. From an engineering perspective, paper materials can be used to construct packaging with low weight but with high relative strength. However, compared to other packaging materials, it can be a challenge to design paper-based packaging for distribution chains with demanding conditions. Boxes made from paper can be sensitive to exposure of moisture, duration of load, and dynamic forces. Along the distribution chain, boxes can be exposed to forces that could potentially cause failure before the boxes intended service life is fulfilled. Therefore, it is important to know how to predict the failure distribution for a specific combination of packaging and distribution chain so that materials with the right properties can be chosen for a given purpose and the risk of failures can be minimized. In this project, we have investigated a statistical material model developed by Bernard D. Coleman. It is based on three material parameters that describe the cumulative distribution function (CDF) of a fiber-breaking behavior for an arbitrary load history. The model has been shown to work for fiber network systems subjected to constant load and constant load rate (CLR). Our purpose was to investigate if it is applicable for fiber network systems of higher structural hierarchy and for more complex load histories. To investigate this, we have performed compression tests with CLR on four different types of corrugated fiberboard and determined the material parameters. Afterward, we performed compression tests for a more complex load history. A periodic, triangular-shaped, load curve was chosen for cyclic testing. Finally, we used the material parameters from the CLR tests to determine the CDF for the periodic load cases. We compared the result with an empirical CDF. The CDFs showed to be in relatively good agreement, but there were some differences. We found that our measurements turned out to produce load history data that deviated from the intended load history. The material parameters were also shown to be less accurate than expected. Due to these deviations, we could not expect a perfect agreement between the CDFs. Therefore, we can not with certainty state that Coleman’s theory is applicable for varying load histories. However, despite the difficulties to experimentally achieve the intended load history, the results showed good agreement in several cases, and the deviations from the theory could possibly be explained by the load history deviations. To be certain, more accurate measurements with higher accuracy need to be done.

Environmental issues are more and more present in our societies. Pollution engendered by plastic waste have drastically increased these past decades, causing several threats to the ecosystem. Therefore, the need of new biodegradable plastics to replace the actual petroleum-based ones is urgent. Cellulose could be a potential substitute since it is a biopolymer, abundant on Earth. However its properties have to be enhanced to be competitive towards actual plastics. The aim of the project is therefore to get a better understanding of cellulose-cellulose interactions. It focuses on the adhesion between cellulosic surfaces. Contact adhesion measurements have been performed on cellulose beads, with different treatments. All the beads had the same size and same concentration. Some of them were native whereas others were charged (600 µeq/g). Half of the native beads were surface modified with a starch coating or a Layer by Layer technique using cationic starch and an anionic polyelectrolyte (EXPN64 or FennoBond 85E). The project included preparation of the surface modified beads, pull-off tests, where load and position were recorded as a function of time, as well as measurements of the contact area. It was found that a higher energy was needed to separate charged and surface modified beads, especially the ones modified with EXPN 64, compared to native beads. The project have also shown that the types of beads influenced the contact area and the strength. However a trend was sometimes difficult to find. The data and results obtained in this project could be further re-used to enlarge the study field and investigate the influence of other parameters (size, concentration) on the adhesion of cellulose beads. / Miljöfrågor är mer och mer närvarande i våra samhällen. plastavfall har ökat drastiskt de senaste decennierna och orsakat flera hot mot ekosystemet. Därför är behovet av ny biologiskt nedbrytbar plast för att ersätta de petroleumbaserade brådskande. Cellulosa kan vara en potentiell ersättare eftersom det är en biopolymer. Emellertid måste dess egenskaper förbättras för att vara konkurrenskraftiga gentemot petroleumbaserad plast. Syftet med projektet är därför att bättre förstå cellulosa-cellulosa-interaktioner. Den fokuserar på vidhäftningen mellan cellulosaytor. Kontaktvidhäftningsmätningar har utförts på cellulosapärlor med olika behandlingar. Alla pärlor hade samma storlek och koncentration. Vissa av dem var naturliga medan andra laddades (600 µeq/g). Projektet inkluderade beredning av ytmodifierade pärlor, utdragningstester, där belastning och position registrerades som en funktion av tiden, samt mätningar av kontaktområdet. Det visade sig att högre energi behövdes för att separera laddade och ytmodifierade pärlor, särskilt de modifierade med EXPN 64, jämfört med tonativa pärlor. Projektet har också visat att typerna av pärlor påverkade kontaktområdet och styrkan. Men en trend var ibland svår att hitta. Uppgifterna och resultaten som erhållits i detta projekt kan vidare användas för att förstora studiefältet och undersöka påverkan av andra parametrar (storlek, koncentration) på vidhäftningen av cellulosapärlor.

Biodegradable polymers are emerging as a new solution to satisfy the increasing demand of greenenvironmentally friendly material. At the same time, the interest for lighter and stronger structures never stops growing. In this paper, we report the production steps to achieve cellulose nanofibrils (CNF) composite filaments via a new green synthesis route known as wet spinning. This new technique avoids the traditional harmful viscose process and produces biodegradable CNF filaments with interesting mechanical properties. This approach is then applied to produce never seen before composite CNF filaments using a three-layered head extruder. In order to obtain conductive filaments, PEDOT/PPS is successfully mixed with CNF to produce in-situ composite filaments. Scanning electron microscopy (SEM), atomic force measurements and tensile tests are employed to characterize the properties of the filaments. / Biologiskt nedbrytbara polymerer börjar framträda som en lösning för det ökade behovet avmiljövänliga material. Samtidigt så växer intresset för lättare och starkare strukturer. I denna rapport tar vi upp produktionsstegen för att uppnå nanofibril komposit cellulosa fibrer (CNF), med hjälp av en ny grön polymerisation mest känd som ”wet spinning”. Med denna nya teknik så behövs inte dem traditionella miljöfarliga viskosprocesserna och man producerar biologiskt nedbrytbara CNF filaments med intressanta mekaniska egenskaper. Denna metod appliceras sen för att producera en komposit som aldrig setts innan. CNF fibrer som består av tre lager ”head-extruder”. För att få fibrer med ledningsförmåga så mixas PEDOT/PPS med CNF för att producera ”in-situ komposit fibrer”. Svepelektronmikroskop (SEM), atomkraftsmikroskopi och töjningstester används för att karaktärisera egenskaperna av fibrerna.

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This thesis deals with the wetting by oil mixtures of two different model cellulose surfaces. The surfaces studied were a regenerated cellulose (RG) surface prepared by spin-coating, and a film consisting of polyelectrolyte multilayers (PEM) of Poly(ethyleneimine) (PEI) and a carboxymethylated Microfibrillated Cellulose (MFC). After coating or covalently modifying the cellulose surfaces with various amounts of fluorosurfactants, the fluorinated cellulose films were used to follow the spreading mechanisms of the different oil mixtures. The viscosity and surface tension of the oil, as well as the dispersive surface energy of the cellulose surface, are essential parameters governing the spreading kinetics. X-ray Photoelectron Spectroscopy (XPS) and dispersive surface energy measurements were made on the cellulose films treated with fluorosurfactants. A strong correlation between the surface coverage of fluorine, the dispersive surface energy and the measured contact angle of the oil mixtures was found. For example, a dispersive surface energy less than 18 mN/m was required in order for the cellulose surface to be non-wetting (θe > 90º) by castor oil. Significant parts of this work were devoted to the development of cellulose surfaces for the wetting studies. The formation of a PEM consisting of PEI and MFC was studied and the total layer thickness and adsorbed amount were optimized by combining Dual Polarization Interferometry (DPI) with a Quartz Crystal Microbalance with Dissipation (QCM-D). The adsorption behaviour as well as the influence of the charge density, pH and electrolyte concentration of PEI, and electrolyte concentration of the MFC dispersion on the adsorbed amount of MFC were investigated. Results indicate that a combination of a high pH, a fairly high electrolyte concentration for PEI solution together with low or zero electrolyte concentration for the MFC resulted in the largest possible adsorbed amounts of the individual PEI and MFC layers. The structures of the two cellulose surfaces were characterised with atomic force microscopy measurements and a difference in terms of surface structure and roughness were observed. Both surfaces were however very smooth with calculated RMS roughness values in the range of a few nanometers. The adsorption behaviour of water-dispersible fluorosurfactants physically adsorbed at various concentrations onto the two model cellulose surfaces was investigated using DPI. The aggregate structure of an anionic fluorosurfactant, perfluorooctadecanoic acid, dispersed in water was studied by Cryo Transmission Electron Microscopy (Cryo-TEM). The fluorosurfactants had an adsorption and desorption behaviour in water which was dependent on the fluorinated chain length and the aggregation form of the fluorosurfactant. Perfluorooctanoic acid and a commercial cationic fluorosurfactant with a formal composition of CF3 (CF2)nSO2NH(CH2)3-4N(CH3)3+I- was found to desorb from the MFC and RG surfaces upon rinsing with water, whereas perfluorooctadecanoic acid was strongly adsorbed to the surfaces. It is essential for a fluorosurfacatant to be strongly adsorbed to the cellulose surface even after rinsing to yield hydrophobic and lipophobic (oleophobic) properties with a large contact angle for oils and water. / QC 20101103

The degradation of cellulose found in wood is one of the most important degradation processes for the carbon flux on earth. The degradation is performed by microorganisms that typically use enzymes. Since the cellulose in wood is crystalline and embedded in other polymers, making it inaccessible and durable, the enzymatic methods of cellulose degradation is also complex. In this thesis, the action of some of these enzymes, called cellulases, have been studied both fundamentally and for industrial purposes. By using model cellulose films and a quartz crystal microbalance it was found that endoglucanases not only depolymerize but also swell model cellulose films. Most probably, this contributes to the synergy seen between endoglucanases and exoglucanases. When an pulp fibers were pre--treated with endoglucanases and beaten subsequently, the fibers became more swollen than reference fibers. The effects of beating enzyme pre--treated fibers were investigated, indicating that endoglucanases improves the fiber/fiber interaction but also alters the behavior of the fibers in the beating process to become more susceptible to the beating. The second part of the thesis has been focused on the use of an albino fungi in order to decrease the amount of wood extractives in wood chips prior to thermo mechanical pulp production. The fungus decreased the most troublesome component, the triglycerides, by more than 90 percent in two weeks without any detrimental effects on pulp properties. On the contrary, pulp strength and optical properties were improved. / QC 20101117