Biobased step-growth polymers : chemistry, functionality and applicability

Inspired by the opportunity to obtain materials with interesting new properties and further stimulated by the increasing oil prices and the augmenting environmental concerns, renewed interest in biobased polymers has recently arisen. Extensive efforts are being invested in extracting useful starting materials from renewable resources and to use these molecules to synthesize novel polymers. The aim of this study was to investigate the potential of several biobased monomers as starting compounds to synthesize polycondensate resins suitable for coating or toner applications. An in-depth study of the chemistry, functionality and the structure-property relations of such polymers was performed. Step-growth polymers with specific characteristics with respect to molecular weight (distribution), end-group structure and thermal properties were targeted. This part of the project included a detailed study of the suitable reaction conditions to polymerize the biobased starting materials, which often have limited reactivity and thermal stability. Polyesters were prepared by reacting the 1,4:3,6-dianhydrohexitols (DAHs, i.e. isosorbide, isoidide and isomannide) with dicarboxylic acids such as succinic acid. The bicyclic structures of the DAHs introduce sufficient chain rigidity and, thus, already for the relatively low molar masses required for coating resins sufficiently high glass transition temperatures (Tg) were obtained. Series of linear and branched terpolyesters were synthesized, of which the average number of reactive end-groups per polymer chain could be adjusted by varying the amount of polyols present in the reaction mixture. It was shown that the exo-oriented hydroxy-groups present in isoidide and isosorbide are more reactive in melt polycondensation reactions, using non-activated dicarboxylic acids, than their endo-oriented counterparts present in both isomannide and isosorbide. In addition, we found that the anhydro ether rings of isomannide are susceptible to ring-opening at elevated temperatures, in contrast to the ether rings of isosorbide and isoidide, which appear to be stable under these conditions. When using isoidide or isomannide to synthesize polyesters, semi-crystalline polymers are obtained, while polymerization of isosorbide with dicarboxylic acids yields amorphous materials. To obtain carboxylic acid-functional polyesters, linear hydroxy-functional polyesters were reacted with citric acid in the melt. Model reactions were carried out to investigate the chemistry of this modification reaction and the resulting end-group structures. Interestingly, citric acid is transformed into a more reactive anhydride species close to its melting temperature of 153 ºC. Therefore, the modification of hydroxy-functional polymers with the thermally labile citric acid can be performed at relatively low temperatures. In addition, the modified products can be cured with conventional cross-linkers (vide infra) at moderate temperatures, which is probably partly due to anhydride formation at the polyester chains ends, accelerating the curing reaction. Aliphatic, biobased polycarbonates were prepared by polymerization of the DAHs, in combination with other diols and/or polyols, using several types of carbonyl sources such as triphosgene, diphenyl carbonate and bis(ethyl/phenyl carbonate) species derived from the DAHs. It proved to be difficult to control the end-group structures of the polycarbonates when using the highly reactive phosgene derivatives, whereas the interchange reactions of the biobased diols with diphenyl carbonate required high reaction temperatures to achieve sufficient conversion. Thermal degradation occurred through an unzipping mechanism and decarboxylation. To prevent these detrimental side reactions, the hydroxy-groups of the DAHs were first converted to carbonate linkages using chloroformates, followed by melt interchange reactions of the resulting molecules with primary diols and/or polyols. These polymerizations do not require too high reaction temperatures, thereby limiting degradation and resulting in the desired hydroxy-functional copolycarbonates with satisfactory Tgs and molecular weights. Another route to functionalized, aliphatic polycarbonates was investigated, involving alcoholysis of high molecular weight poly(cyclohexene carbonate) by polyol species such as trimethylolpropane and 1,3,5-cyclohexanetriol. The obtained polycarbonates have significantly enhanced functionalities as well as reduced molecular weights and Tgs, all suitable for coating applications. The various hydroxy-functional polymers were mixed with free or e-caprolactam-blocked polyisocyanate curing agents and applied as coatings by either solution casting or powder coating. Polymers with carboxylic acid end-groups were cured using epoxy-compounds or ß- hydroxyalkylamides. The resulting polyester and poly(ester/carbonate urethane) coatings were tested for chemical, mechanical and UV stability. In addition, the rheological properties of these materials were investigated. Networks obtained by curing branched polymers perform better than those prepared from linear polymers, which is mainly due to the enhanced crosslink density of the former systems. Solvent and impact resistant coatings were prepared from linear and branched, biobased polycondensates. In addition to the conventional curing agents used in this study, several novel, biobased, e-caprolactam-blocked diisocyanates proved efficient in cross-linking branched polyesters and polycarbonates, leading to fully biobased, chemically and mechanically stable, glossy coatings with very promising properties

Polyuretanes, polyurethaneureas and polyureas and use thereof

The present invention is to a chain extended polyurethane, polyurethaneurea and/or polyurea segmented copolymer wherein the polyurethane, polyurethaneurea or polyurea segment contain a chain extender having an amide segment, an ester segment or a combination of amide and ester segments

Tailormade regelgeving voor windturbineparken op de Noordzee

Op 16 oktober 2014 is het voorstel voor de Wet windenergie op zee (hierna: het wetsvoorstel of de wet) aan de Tweede Kamer aangeboden. Zoals de naam van het wetsvoorstel al doet vermoeden, betreft het de regelgeving voor de realisatie en exploitatie van windturbineparken op zee. Het wetsvoorstel bevat onder meer een nieuw wettelijk instrument, namelijk het kavelbesluit. In dit artikel wordt het voorgestelde wettelijk systeem uiteengezet. Daarbij zal waar nodig een aantal vragen worden gesteld, in de hoop dat deze gedurende het wetgevingsproces nog beantwoord kunnen worden. The Legitimacy and Effectiveness of Law & Governance in a World of Multilevel Jurisdiction

Hydrophobic, self-replenishing coatings for polar substrates

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Carbohydrate-based PBT copolyesters from a cyclic diol derived from naturally occurring tartaric acid: a comparative study regarding melt polycondensation and solid-state modification

2,3-O-Methylene-L-threitol (Thx) is a cyclic carbohydrate-based diol prepared by acetalization and subsequent reduction of the naturally occurring tartaric acid. The structure of Thx consists of a 1,3-dioxolane ring with two attached primary hydroxyl groups. Two series of partially bio-based poly(butylene terephthalate) (PBT) copolyesters were prepared using Thx as a comonomer by melt polycondensation (MP) and solid-state modification (SSM). Fully random copolyesters were obtained after MP using mixtures of Thx and 1,4-butanediol in combination with dimethyl terephthalate. Copolyesters with a unique block-like chemical microstructure were prepared by the incorporation of Thx into the amorphous phase of PBT by SSM. The partial replacement of the 1,4-butanediol units by Thx resulted in satisfactory thermal stabilities and gave rise to an increase of the Tg values, this effect was comparable for copolyesters prepared by MP and SSM. The partially bio-based materials prepared by SSM displayed higher melting points and easier crystallization from the melt, due to the presence of long PBT sequences in the backbone of the copolyester. The incorporation of Thx in the copolyester backbone enhanced the hydrolytic degradation of the materials with respect to the degradation of pure PBT.Peer ReviewedPostprint (published version

Coping with weight change during the life cycle : a qualitative study

Individuals can experience weight fluctuations during their life. This is associated with events, such as work, marriage, having children or social pressure. Weight change can affect health related quality of life and one’s attitude and is a situation that needs to be coped with. Research in this area is limited, especially taking different life events into consideration and how individuals cope with weight change. Therefore, the purpose of this study was to examine how certain events are associated with weight change, how weight change influences health related quality of life and how individuals cope with the weight change. Five individuals were invited to participate in a semi-structured interview that assessed how certain events influenced their weight, how this affected them emotionally, physically and mentally and how they coped with the weight change. Data were obtained through individual, semi-structured interviews. Following prolonged engagement and transcription, the data were inductively analyzed and organized into emerging patterns and themes. In addition, the data were deductively analyzed. The findings revealed that weight fluctuations were triggered by significant single events or a combination of events. Results indicated that unintended gained weight could lead to decreased HRQL and intended weight loss could lead to an increased HRQL. Weight gain could negatively influence one’s self-image while weight loss could increase energy levels and work as a motivator to lose more weight. Weight change did not only affect attitudes and HRQL but also the importance of the event that was associated with the weight change. Eventually depending on the chosen coping strategy - problem-focused or emotion focused - the individuals lost, gained weight or maintained the same weight. This study suggests that losing weight does not only lead to a better HRQL (e.g., increased energy levels) but also a different attitude, such a thinking that it is possible to eat those things that one ate before attempting to lose weight and in turn gaining weight again. All in all, there are many different ways that weight can be influenced, there are different ways that an individual can be affected and there are different ways of coping

Polyesters, polycarbonates and polyamides based on renewable resources

In this chapter, we have given an overview of a range of biomass-based polymers prepared through polycondensation chemistry. This is by no means an exhaustive summary of available starting materials and polymers. Still, it is clear that this rapidly expanding field of research opens up new synthetic pathways to performance polymers with exciting novel properties. Some of these biobased polycondensates can rival conventional polymers from petro-chemistry in terms of mechanical and chemical performance and a limited number have already found their way to the market place. Further development of bio-refining processes is expected to improve the availability and economics of the discussed starting materials and polymers. Several of the presented polymers can be produced in existing process equipment with only minor adjust ments. Typically, improved temperature control and an inert atmosphere are required to prevent degradation and discoloration of the bio-based products. In addition, more sustainable and milder synthetic routes as well as more effective catalysis are necessary to make optimal use of biomass, constituting stimuli for new research into the field of step-growth polymerization