Foamability of Cellulose Palmitate Using Various Physical Blowing Agents in the Extrusion Process

Polymer foams are widely used in several fields such as thermal insulation, acoustics, automotive, and packaging. The most widely used polymer foams are made of polyurethane, polystyrene, and polyethylene but environmental awareness is boosting interest towards alternative bio-based materials. In this study, the suitability of bio-based thermoplastic cellulose palmitate for extrusion foaming was studied. Isobutane, carbon dioxide (CO(2)), and nitrogen (N(2)) were tested as blowing agents in different concentrations. Each of them enabled cellulose palmitate foam formation. Isobutane foams exhibited the lowest density with the largest average cell size and nitrogen foams indicated most uniform cell morphology. The effect of die temperature on foamability was further studied with isobutane (3 wt%) as a blowing agent. Die temperature had a relatively low impact on foam density and the differences were mainly encountered with regard to surface quality and cell size distribution. This study demonstrates that cellulose palmitate can be foamed but to produce foams with greater quality, the material homogeneity needs to be improved and researched further

Effects of thiol substitution in deep-eutectic solvents (DESs) as solvents for metal oxides

This study deals with an investigation of how substitution of an alcohol group by a thiol group in mixtures of choline chloride with a series of bio-sourceable molecules affects the physico-chemical properties of the mixtures and their ability to dissolve metal oxides. All of the thiol mixtures studied showed a higher affinity and selectivity for late transition metals and the physical properties of the mixtures were improved compared to their alcohol analogues (i.e. lower viscosity, wider liquid range). The metal solubility was assessed via determination of the final concentration of the metal oxides dissolved in thiol mixtures via inductively coupled plasma optical emission spectroscopy (ICP-OES). The thiol function selectively improved the solubilities of the late transition metal oxides (i.e. copper and zinc), which are valuable metals often present as residue in industrial waste. The solubility of iron oxides was much lower than that of the valuable metals, which is a significant benefit in industrial applications. The different solubilization behaviour of metal oxides in the thiol and alcohol mixtures was further investigated via UV-vis absorption and infrared spectroscopy. This study allowed the potential of these deep-eutectic solvents for the selective recovery of metals to be assessed

Pitkäketjuisten selluloosaestereiden ominaisuudet ja applikaatiot

Environmental awareness and growing concern about plastic waste and the depletion of non-renewable resources have boosted interest in bio-based polymers in recent years. Although the fraction of bio-based polymers in the global plastics market is still small, the demand and share of bio-based polymers is rapidly increasing. The aim of this dissertation was to prove that fully bio-based long chain cellulose esters have the potential to replace traditional oil-based plastics in selected applications. In this research, the long chain cellulose esters were synthesized with different side chain lengths (C6-C18) and the influence of side chain length on barrier, mechanical and thermal properties was demonstrated. In order to study the differences in pulp reactivity and properties of cellulose esters, the molar mass of commercial softwood dissolving pulp was decreased in a controlled manner by ozone-hydrogen peroxide treatment. This research proved that decreasing cellulose molar mass enabled the synthesis of long chain cellulose esters with better reaction efficiency than with the original cellulose. In addition, both the cellulose molar mass and the degree of substitution could be controlled. The resulting long chain cellulose esters formed transparent, flexible and heat sealable films with good water vapor barrier and mechanical properties. Cellulose esters formed smooth and homogeneous coatings with good adhesions when nanocellulose (CNF) films and virgin kraft papers were coated. The long chain cellulose ester coatings also significantly improved the moisture barrier properties of CNF film and kraft paper – these values decreased linearly as a function of ester chain length up to 50% from non-coated values. These coatings also significantly improved the surface smoothness of CNF films by decreasing nano-roughness. The long chain cellulose ester coatings made the material heat sealable and, in addition, the coatings had no antimicrobial activity, and only few microbes adhered to the surface of these films. These results demonstrate that long chain cellulose ester coatings have potential in future packaging applications where surface smoothness, heat sealability and good water vapor barrier properties are required. Injection molding of long chain cellulose esters and their blends was also studied and the mechanical properties were investigated. The results indicate that thermoplastic long chain cellulose esters are completely processable without any addition of a plasticizer, which is very unusual in the case of cellulose esters. This research proves that these materials have good potential to be used in injection molding applications.Ympäristötietoisuus, kasvava huoli muovijätteistä sekä uusiutumattomien luonnonvarojen ehtyminen ovat viime vuosina kasvattaneet kiinnostusta biopohjaisiin polymeereihin. Biopohjaisten polymeerien kysyntä kasvaa nopeasti, mutta niiden osuus muovien kokonaismarkkinasta on edelleen pieni. Tämän väitöskirjan tavoitteena oli osoittaa, että täysin biopohjaisilla pitkäketjuisilla selluloosaestereillä on mahdollisuus korvata perinteiset öljypohjaiset muovit tietyissä sovelluksissa. Tässä tutkimuksessa valmistettiin pitkäketjuisia selluloosaestereitä eri sivuketjujen pituuksilla (C6-C18) ja tutkittiin sivuketjujen vaikutusta selluloosaestereiden mekaanisiin, termisiin ja barrier-ominaisuuksiin. Kaupallisen liukoselluloosan moolimassaa alennettiin kontrolloidusti esikäsittelemällä selluloosaa otsonilla ja vetyperoksidilla, jotta saatiin selville selluloosan moolimassan vaikutus massan reaktiivisuuteen ja selluloosaestereiden ominaisuuksiin. Tutkimuksessa havaittiin, että selluloosan moolimassan alentaminen mahdollisti selluloosaestereiden syntetisoinnin paremmalla reaktiotehokkuudella kuin alkuperäistä selluloosaa käyttämällä. Samalla myös selluloosaestereiden moolimassaa ja substituutioastetta pystyttiin kontrolloimaan. Pitkäketjuiset selluloosaesterit muodostivat läpinäkyviä, joustavia ja kuumasaumautuvia filmejä, joilla oli myös alhainen vesihöyryn läpäisevyys sekä hyvät mekaaniset ominaisuudet. Päällystettäessä nanoselluloosafilmejä ja käsittelemätöntä voimapaperia selluloosaestereillä, muodostui tasainen ja homogeenisen pinta, jolla oli hyvä tarttuvuus. Pitkäketjuiset selluloosaesteripinnoitteet alensivat myös merkittävästi nanoselluloosafilmien ja voimapaperin vesihöyryn läpäisevyyttä; läpäisevyysarvot alenivat lineaarisesti ketjunpituuden kasvaessa. Samalla myös nanoselluloosafilmien pinnankarheus parani huomattavasti ja pinnoite mahdollisti materiaalin kuumasaumauksen. Selluloosaesteripinnoitteilla ei myöskään ollut antimikrobista aktiivisuutta. Tulokset osoittivat, että pitkäketjuisia selluloosaesteripinnoitteita voidaan hyödyntää tulevaisuuden pakkaussovelluksissa, joissa vaaditaan sileää pintaa ja hyvää vesihöyryn läpäisemättömyyttä. Lisäksi pitkäketjuisten selluloosaestereiden prosessoitavuutta ja mekaanisia ominaisuuksia tutkittiin ruiskuvalun avulla. Nämä termoplastiset selluloosaesterit olivat täydellisesti prosessoitavissa ilman lisäaineistusta, mikä on selluloosaestereiden tapauksessa harvinaista. Tämän perusteella pitkäketjuisilla selluloosaestereillä on hyvät mahdollisuudet korvata perinteisiä muoveja esimerkiksi ruiskuvaluapplikaatioissa

Injection Molding of Thermoplastic Cellulose Esters and Their Compatibility with Poly(Lactic Acid) and Polyethylene

Interest in biobased polymers from renewable resources has grown in recent years due to environmental concerns, but they still have a minimal fraction of the total global market. In this study, the injection molding of thermoplastic cellulose octanate (cellulose C8) and cellulose palmitate (cellulose C16) were studied. The mechanical properties of injection-molded test specimens were analyzed by using tensile testing, and the internal structure of injection-molded objects was studied by using a field emission scanning electron microscopy (FE-SEM). We showed that thermoplastic cellulose C8 and cellulose C16 were completely processable without the addition of a plasticizer, which is very unusual in the case of cellulose esters. The compatibility of cellulose esters with poly(lactic acid) (PLA) and biopolyethylene (bio-PE) was also tested. By compounding the cellulose esters with PLA, the elongation of PLA-based blends could be improved and the density could be reduced. The tested thermoplastic cellulose materials were fully biobased, and have good future potential to be used in injection molding applications

Improved Reactivity and Derivatization of Cellulose after Pre-Hydrolysis with Commercial Enzymes

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