Poling influence on the mechanical properties and molecular mobility of highly piezoelectric P(VDF-TrFE) copolymer

The calorimetric, dielectric, and mechanical responses of highly piezoelectric 70/30 P(VDF-TrFE) displaying homogenous d33 of 219 pC N21 are studied. This work aims at better understanding the influence of poling on the mechanical properties of this copolymer. To explain the one decade mechanical modulus drop observed across the Curie transition, a stiffening process of the amorphous phase due to the local electric fields in the ferroelectric crystals is proposed. In poled P(VDF-TrFE), these fields are preferentially aligned resulting in a more stable and higher modulus below the Curie transition. This hypothesis accounts for the lower dielectric signals obtained with the poled sample. Through the Curie transition, the vanishing of these local electric fields, stemming from progressive disorientation and conversion of ferroelectric crystals to paraelectric ones, releases the constraints on the amorphous phase, leading to a storage modulus drop typical of a viscoelastic transition

Genushysteri : Feministiska stereotyper i svensk debatt 2009 till 2011

I denna uppsats undersöks vilka stereotyper om feminism och feminister som förekom i opinionsartiklar i Aftonbladet, Expressen, Svenska Dagbladet och på debattsidan Newsmill.se från och med 1 januari 2009 till och med 23 november 2011. Kriterierna var att skribenten tar avstånd från feminism och detta ska ske i artikeln i fråga. Vidare undersöktes vad dessa skribenter menar med jämställdhet om de ser detta som ettmål att eftersträva och hur detta mål ska uppnås utan feminism. Undersökningen tog fasta på begreppen feminism och jämställdhet och en tematisk analys av hur feminister som grupp framställs genomfördes. Utöver vanligt förekommande feministiska stereotyper, som att de är lättirriterade och splittrar kärnfamiljen, framkom även att feminister anses stå för odemokratiska värderingar. Begreppet jämställdhet definierades ofta som en kontrast till feminism och vissa menade att feminismen står i vägen för jämställdheten eller rent av skapar könsdiskrimineringen i samhället. I de fall åtgärder föreslogs handlade dessa mer om att sluta upp med åtgärder inriktade på kön och återgå till det sunda förnuftet än att arbeta aktivt för förändring. Många ansåg att jämställdheten kommer av sig själv bara vi slutar att tala om kön och andra samhällsgrupper. Detta kan ses som ett uttryck för en linjär historiesyn där jämställdhet är ett tecken på att civilisationen går framåt. Jämställdheten, oavsett vad man menar med begreppet, ses av de flesta som ett legitimt ideal och den utveckling som har uppnåtts kan inte gå tillbaka

Computational Studies of Poly(vinylidene fluoride)

Poly(vinylidene fluoride) (PVDF) is a versatile material with numerous applications, both potential and realized, in many industrial sectors. The extent of applications, ranging from cable and wire products, to sensors for the monitoring of respiration and heart-rate in medicine, indicates on the level of interest the materials science community has for this material. PVDF has the potential to be used in applications where its piezoelectric characteristics are utilized, but for this to be realized, a specific crystal structure, the polar β-phase, need to be present in the material. Since PVDF is polymorphic and usually crystallizes from melt or from solution into the non-polar α-phase, which is of little use in piezoelectric applications, the induction of the β-phase is an active field of research. With computational methods it is possible to study PVDF on a molecular level to gain better insights into the mechanisms behind the formation of this specific crystal structure. Conformational studies of PVDF, the effect of carbon nanotubes on the conformation as well as the mechanical properties of PVDF, copolymerization with trifluoroethylene and the effect of increased temperatures and pressures have been studied using molecular mechanics/dynamics and first principles methods. It has been found that carbon nanotubes mainly act as nucleating agents for the formation of β-phase PVDF as their effect on the mechanical properties of PVDF is relatively small. Furthermore, β-phase formation can be facilitated with very rapid cooling rates from the melt, hindering the transformation into the thermodynamically stable α-phase and by inclusion of trifluoroethylene units in the PVDF chain. With better insights into the mechanism of β-phase PVDF formation, it would ideally be possible to produce piezoelectric PVDF with better characteristics and possibly also in new and more efficient ways

Cykeldäck med automatisk anpassning av dubbfunktion beroende på yttertemperatur

Rapporten är framtagen med ekonomiska bidrag från Trafikverket, Skyltfonden. Ståndpunkter och slutsatser i rapporten reflekterar författaren och överensstämmer inte med nödvändighet med Trafikverkets ståndpunkter och slutsatser inom rapportens ämnesområden.Cyklister är sedan 2008 den grupp som skadas mest i trafiken. Halka eller försämrat väggrepp är ofta en betydelsefull faktor. Antalet cykelolyckor kan potentiellt minska genom användandet av vinterdäck för cyklar. Dubbdäck ger bra fäste på is men ökar cykelns rullmotstånd. Genom att låta dubbarna vila på ett gummimaterial med kraftig variation i hårdhet/styvhet/deformerbarhet vid olika temperaturer skulle man kunna framställa dubbade cykeldäck där metalldubbarnas kontakt med underlaget ändras beroende på temperaturen. Vid minusgrader skall således dubbarnas kontakt med underlaget vara betydligt medan det vid plusgrader skall råda mindre dubbkontakt. Projektet har utvärderat ett antal gummimaterial genom mekaniska tester (ex. hårdhet vid olika temperaturer) och konceptet har demonstrerats i ett proof-of-concept där kontakt med underlag för dubb och däck har utvärderats och friktionstester har genomförts. Temperaturberoende egenskaper för dubbade däck kan erhållas men konceptet måste utvecklas ytterligare då en lägre risk för halka vid rumstemperatur jämfört med vid minusgrader kunde påvisas för samtliga prototyper

”Någon som bryr sig” En kvalitativ enkätstudie om elevers uppfattningar om vad som kan vara orsaker till skolfrånvaro samt hur skolor kan arbeta förebyggande och åtgärdande

Studiens syfte var att undersöka elevers uppfattningar om faktorer som kan orsaka skolfrånvaro och vad de anser skolan skulle kunna göra för att öka närvaron. Då orsakerna till frånvaro kan vara flera har studien valt att särskilt belysa digitala mediers eventuella påverkan. För att studiens syfte skulle uppnås besvarades nedanstående frågeställningar: Vilka faktorer menar eleverna kan ligga till grund för skolfrånvaro? Vilka uppfattningar har eleverna om användandet av digitala medier som en påverkande faktor till skolfrånvaro? Hur anser eleverna att skolorna skulle kunna arbeta förebyggande och åtgärdande kring skolfrånvaro? Studiens empiri inhämtades i fyra olika kommunala elevklasser på högstadiet och på gymnasiet i två olika kommuner i Västsverige. 91 elever deltog i undersökningen genom att besvara var sin elevenkät i vilken deras uppfattningar om fenomenet framgår. Undersökningen är kvalitativ med en systemteoretisk ansats och ett salutogent perspektiv. De specialpedagogiska perspektiven är det relationella, det kompensatoriska samt dilemma perspektivet. Viktigt i studien har varit att få fram elevernas röst då det är deras skol- och internetvärld studien haft som avsikt att undersöka. I studiens resultat framkom att respondenterna såg flera tänkbara orsaker till frånvaro vilket visar att det är en komplex fråga. Gemensamt hos nästan samtliga elever var dock att de tror att trakasserier och mobbning på nätet kan vara en orsak till frånvaro i skolan. Det kan bland annat handla om elaka kommentarer, näthat, hemska rykten och bilder som sprids. Även att dataspel och spelberoende kan leda till skolfrånvaro är någonting som återkommande togs upp i elevernas svar. Flera av dem har bekanta som varit frånvarande från skolan på grund av spelande. De berättade också att kamrater försökt få dem att vara hemma från skolan för att spela. Annat som studien tyckt sig se är att det råder olika uppfattningar om var gränsen går för vad som ska räknas som skämt när det gäller så kallade pranks och sociala medier och vad som är trakasserier. I resultatet lyfts även många konkreta förslag från eleverna på hur skolorna kan arbeta förebyggande och åtgärdande i arbetet kring frånvaro. Också förslag på hur skolorna skulle kunna använda sig av digitala medier för att få elever till skolan redovisas. I den sista delen av resultatet kunde studien se att eleverna tänkte på det förebyggande och åtgärdande arbetet utifrån att det behövs en känsla av sammanhang, KASAM för att eleverna ska vilja vara i skolan. Även vikten av förtroendefulla relationer poängterades. Det behöver finnas någon i skolan som bryr sig om eleven. Om en elev inte kommer tills skolan behöver hen känna sig saknad

Biopolymerer som transportskydd för byggnadsmaterial

Construction materials are exposed to different conditions along the way from the sawmill, during storage and handling, until the materials are a part of the completed construction. During this time the materials may be exposed to moisture and dirt that can cause an attack by moulds. This, in turn, can give rise to health problems for individuals staying in the building and can also be the cause of a bad smell in the building. It is therefore necessary to protect the materials during this limited period of transport, storage, and handling.In this study two construction materials were used; untreated wood and plasterboard. As a possible protection for the materials coatings based on biopolymers were made. Biopolymers are totally degradable and are relatively cheap raw materials. The biopolymers used in this study were starch from potato, protein from corn, and acetylated mono- and diglyceride. Also, fungicides that function as inhibitors for mould growth were added to the coatings.Samples of wood and plasterboard were covered with the coatings using a paint sprayer. The samples were then exposed to a spore suspension containing spores from four of the most common mould species found attacking building material. The samples were then placed in three different climates differing in temperature and humidity. The conditions were in all three cases favourable for mould growth. The samples were placed in these conditions for a month and analysis of the growth on the samples was made once a week and according to a scale with five grades.The results varied very much between the samples, even between samples treated with the same coating, but an obvious trend gave indications of that it is possible to use biopolymers as protection for construction materials. In this study the coating based on the acetylated monoglyceride showed the best properties.Uppsatsnivå:

Effect of a Small Amount of Thermoplastic Starch Blend on the Mechanical Recycling of Conventional Plastics

The usage of bioplastics could increase in the future which may cause contamination of the waste streams of conventional plastics. The objective of this study was to investigate if a small amount of biopolymer contaminating conventional polymers would significantly affect mechanical and thermal properties. A starch-based plastic was first compounded by blending plasticised starch with PLA (polylactic acid). This polymer blend was subsequently compounded with HDPE (high density polyethylene), PP (polypropylene) or PET (polyethylene terephthalate) at 0%, 1% and 5% of the biopolymer. The compounds were characterised by tensile tests, Charpy impact tests, DSC (differential scanning calorimetry) and FESEM (field emission scanning electron microscopy). Tests showed that PE and PP were not significantly affected in terms of tensile strength and modulus but the elongation at break showed a strong reduction. PET was, on the other hand, incompatible with the starch-based plastic. Already at 1% contamination, PET had lost most of its impact strength

Utilization of a Portable Sampler for Liquefied Natural Gas Composition and Particles at Refueling Stations

LNG and LBG are environmentally beneficial when used for long-distance road transport. Their use may be the most feasible alternative for a rapid conversion of heavy-duty transports towards a sustainable society and the goals of Agenda 2030. However, the roll-out of LNG and LBG as transport fuels requires reliable determination of their composition and physical properties in order to secure the quality and emission levels. As learned from current state-of-art, it is highly challenging to take a representative sample of LNG/LBG for subsequent analysis in a laboratory. This requires the proper vaporization of the fuel while avoiding partial vaporization and loss of fuel constituents and particles. The goal was to construct and test a sampler that would be compact and transportable for the simultaneous sampling of gas and solid particles at a commercial refueling station. Close to theoretical LNG pipeline temperature (-160 oC) was achieved in the measurement system in about 10 min, leading to minimal pre-vaporization and potential for fast, true and repeatable measurements. During the final test particles were quantified to 0.2 mg/Nm3 gas, with major number of particles being metal, metal oxide and silica. The gas composition measurements demonstrated a repeatability, defined as %RSD, of 0.3 % for main component methane (99.0 %), 2.0 % for ethane (615 ppm) and pooled standard deviation for all measurable components were below 1.0 %.</p

Waste Management Option for Bioplastics Alongside Conventional Plastics

Bioplastics can be defined as polymers derived partly or completely from biomass. Bioplastics can be biodegradable such as polylactic acid (PLA) and polyhydroxyalkonoates (PHA); or non-biodegradable (biobased polyethylene (bio-PE), polypropylene (bio-PP), polyethylene terephthalate (bio-PET)). The usage of such bioplastics is expected to increase in the future due to new found interest in sustainable materials. At the same time, these plastics become a new type of waste in the recycling stream. Most countries do not have separate bioplastics collection for it to be recycled or composted. After a brief introduction of bioplastics such as PLA in UK, these plastics are once again replaced by conventional plastics by many establishments due to lack of commercial composting. Recycling companies fear the contamination of conventional plastic in the recycling stream and they said they would have to invest in expensive new equipment to separate bioplastics and recycle it separately. Bioplastics are seen as a threat to the recycling industry as bioplastics may degrade during the mechanical recycling process and the properties of the recycled plastics are seriously impacted. This project studies what happens when bioplastics contaminate conventional plastics. Three commonly used conventional plastics were selected for this study: polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET). In order to simulate contamination, two biopolymers, either polyhydroxyalkanoate (PHA) or thermoplastic starch (TPS) were blended with the conventional polymers. The amount of bioplastics in conventional plastics was either 1% or 5%. The blended plastics were processed again to see the effect of degradation. Mechanical, thermal and morphological properties of these plastics were characterized.   The results from contamination showed that the tensile strength and the modulus of PE was almost unaffected whereas the elongation is clearly reduced indicating the increase in brittleness of the plastic. Generally, it can be said that PP is slightly more sensitive to the contamination than PE. This can be explained by the fact that the melting point of PP is higher than for PE and as a consequence, the biopolymer will degrade more quickly. However, the reduction of the tensile properties for PP is relatively modest. It is also important to notice that when plastics are recovered, there will always be a contamination that will reduce the material properties. The reduction of the tensile properties is not necessary larger than if a non-biodegradable polymer would have contaminated PE or PP. The Charpy impact strength is generally a more sensitive test method towards contamination. Again, PE is relatively unaffected by the contamination but for PP there is a relatively large reduction of the impact properties already at 1% contamination. PET is polyester and it is by its very nature more sensitive to degradation than PE and PP. PET also have a much higher melting point than PE and PP and as a consequence the biopolymer will quickly degrade at the processing temperature of PET. As for the tensile strength, PET can tolerate 1% contamination without any reduction of the tensile strength. However, when the impact strength is examined, it is clear that already at 1% contamination, there is a strong reduction of the properties. It can also be seen that presence of TPS is more detrimental to PET than PHA is. This can be explained by the fact that TPS contain reactive hydroxyl groups that can react with the ester bond of PET. This will in other words lead to degradation of PET. The thermal properties show the change in the crystallinity. As a general conclusion, it can be said that the plastics become less crystalline when contaminated. The blends were also characterized by SEM. Biphasic morphology can be seen as the two polymers are not truly blendable which also contributes to reduced mechanical properties. Recycling of the contaminated polymer shows an increase in crystallinity. This means that when the polymers are processed, polymer degradation occur causing the polymer chains to gradually become shorter which will enhance the crystallization process. The study shows that PE is relatively robust againt contamination, while polypropylene (PP) is somewhat more sensitive and polyethylene terephthalate (PET) can be quite sensitive towards contamination