Ultrasuodatusmembraanin modifiointi entsyymeillä suodatusominaisuuksien parantamiseksi

Tämän diplomityön tarkoituksena oli kiinnittää lakkaasientsyymi polyeetterisulfonimembraaniin suodatusominaisuuksien parantamiseksi. Lakkaasientsyymin tiedetään pilkkovan ligniiniä ja kiinnittämällä lakkaasientsyymi membraaniin tavoiteltiin ligniinin aiheuttaman membraanin likaantumisen vähentämistä. Tällöin vältyttäisiin lisäksi erilliseltä esikäsittely vaiheelta ja voitaisiin saada puhtaampi lopputuote. Lakkaasientsyymivalmisteena tutkimuksessa käytettiin Novozym® 51003 ja ristisilloittajana käytettiin glutaarialdehydiä. Vapaan ja kiinnitetyn lakkaasientsyymin aktiivisuuden määritettiin 2,2-atso-bis(3- etyylibentsotiatsolyyli-6-sulfonihappo):n avulla. Lakkaasin kiinnittymistä membraaniin tutkittiin ATR-FTIR spektroskoopilla kiinnittymisen varmentamiseksi. Lakkaasi modifioituja membraaneja testattiin koivu-uute suodatuksella ja adsorptio kokeella. Lakkaasientsyymi saatiin kiinnitettyä membraaniin ristisilloittajan avulla, mutta lakkaasilla modifioitujen membraanien vesivuot laskivat noin puoleen alkuperäisestä. Koivu-uuteen suodatuksissa modifioidusta membraanista ei saatu permeaattia lävitse, mutta adsorptiokokeen tulosten perusteella voidaan todeta lakkaasientsyymin pilkkoneen ligniiniä. Kiinnitetyn lakkaasin aktiivisuus vaihteli rinnakkaisten määritysten välillä, minkä vuoksi lakkaasin kiinnitysmekanismin lisätutkiminen olisi tarpeen luotettavimpien tulosten saamiseksi.

Modification of commercial poly-lactide for extrusion coated food packaging applications

Poly-L-lactide (PLLA) is a widely used sustainable and biodegradable alternative to replace synthetic non-degradable plastic materials in the packaging industry. Conversely, its processing properties are not always optimal, e.g. insufficient melt strength at higher temperatures (necessary in extrusion coating processes). This thesis reports on research to improve properties of commercial PLLA grade (3051D from NatureWorks), to satisfy and extend end-use applications, such as food packaging by blending with modified PLLA. Adjustment of the processability by chain branching of commercial poly-L-lactide initiated by peroxide was evaluated. Several well-defined branched structures with four arms (sPLLA) were synthesized using pentaerythritol as a tetra-functional initiator. Finally, several block copolymers consisting of polyethylene glycol and PLLA (i.e. PEGLA) were produced to obtain a well extruded material with improved heat sealing properties. Reactive extrusion of poly-L-lactide was carried out in the presence of 0.1, 0.3 and 0.5 wt% of various peroxides [tert-butyl-peroxybenzoate (TBPB), 2,5-dimethyl-2,5-(tert-butylperoxy)-hexane (Lupersol 101; LOL1) and benzoyl peroxide (BPO)] at 190C. The peroxide-treated PLLAs showed increased complex viscosity and storage modulus at lower frequencies, indicating the formation of branched/cross linked architectures. The material property changes were dependent on the peroxide, and the used peroxide concentration. Gel fraction analysis showed that the peroxides, afforded different gel contents, and especially 0.5 wt% peroxide, produced both an extremely high molar mass, and a cross linked structure, not perhaps well suited for e.g. further use in a blending step. The thermal behavior was somewhat unexpected as the materials prepared with 0.5 wt% peroxide showed the highest ability for crystallization and cold crystallization, despite substantial cross linking. The peroxide-modified PLLA, i.e. PLLA melt extruded with 0.3 wt% of TBPB and LOL1 and 0.5 wt% BPO was added to linear PLLA in ratios of 5, 15 and 30 wt%. All blends showed increased zero shear viscosity, elastic nature (storage modulus) and shear sensitivity. All blends remained amorphous, though the ability of annealing was improved slightly. Extrusion coating on paperboard was conducted with PLLA, and peroxide-modified PLLA blends (90:10). All blends were processable, but only PLLA with 0.3 wt% of LOL1 afforded a smooth high quality surface with improved line speed. Adhesion levels between fiber and plastic, as well as heat seal performance were marginally reduced compared with pure 3051D. The water vapor transmission measurements (WVTR) of the blends containing LOL1 showed acceptable levels, only slightly lower than for comparable PLLA 3051D. A series of four-arm star-shaped poly-L-lactide (sPLLA) with different branch length was synthesized by ring opening polymerization (ROP) of L-lactide using pentaerythritol as initiator and stannous octoate as catalyst. The star-shaped polymers were further blended with its linear resin and studied for their melt flow and thermal properties. Blends containing 30 wt% of sPLLA with low molecular weight (30 wt%; Mwtotal: 2500 g mol-1 and 15000 g mol-1) showed lower zero shear viscosity and significantly increased shear thinning, while at the same time slightly increased crystallization of the blend. However, the amount of crystallization increased significantly with the higher molecular weight sPLLA, therefore the star-shaped structure may play a role as nucleating agent. PLLA-polyethylene glycol–PLLA triblock copolymers (PEGLA) with different PLLA block length were synthesized and their applicability as blends with linear PLLA (3051D NatureWorks) was investigated with the intention of improving heat-seal and adhesion properties of extrusion-coated paperboard. PLLA-PEG-PLLA was obtained by ring opening polymerization (ROP) of L-lactide using PEG (molecular weight 6000 g mol-1) as an initiator, and stannous octoate as catalyst. The structures of the PEGLAs were characterized by proton nuclear magnetic resonance spectroscopy (1H-NMR). The melt flow and thermal properties of all PEGLAs and their blends were evaluated using dynamic rheology, and differential scanning calorimeter (DSC). All blends containing 30 wt% of PEGLAs showed slightly higher zero shear viscosity, higher shear thinning and increased melt elasticity (based on tan delta). Nevertheless, no significant changes in thermal properties were distinguished. High molecular weight PEGLAs were used in extrusion coating line with 3051D without problems.

Exploring two cases of Piano Teacher Education in Finland and Germany

Research about music instrument teacher education is scattered and fairly recent, especially in the European context. The purpose of this study was to explore two cases of piano teacher education programs at higher music education institutions, one in Finland, and one in Germany, to gain insights into the preparation of piano teachers for their professional working life. The aim was to identify issues for consideration in curriculum development of piano teacher education to enhance the teaching and learning of piano playing, and to ultimately increase musical practice and engagement among young learners. Nine semi-structured interviews with piano teacher educators, heads of program, other lecturers within the program, and student piano teachers in both cases were analyzed using applied thematic analysis. Three main themes with subcategories emerged: (1) the organization of the piano teacher education program, such as the structure, the content, the learning environments provided, and the development mechanisms of the program; (2) the views on the piano teacher profession, the working environment and resulting requirements, including further education during professional life; and (3) the professional skills and teacher identity development of student teachers. While the supposed working environments and requirements of future piano teachers, the student teachers' development characteristics, and the content were found reasonably concurrent in both cases, the structure of the teacher education program, and the organization of learning environments presented notable differences. While the complete teacher qualification in the Finnish case was offered as option in the Bachelor and Master of Music program within the piano department, the German case offered a separate program for music instrument educators. Other main differences concerned the organizations of practical teaching experiences, and the linking of practical with theoretical pedagogy. Conviction and enthusiasm for improving piano and other music instrument teacher education seemed remarkable. These improvements could include the development of a comprehensive teacher education pedagogy for music instrument teacher educators, intensified cross-linking within and of higher music education institutions in local contexts, and the expansion of professional development opportunities.