Evaluation of maleate, fumarate, and succinate diesters as potential green plasticizers
Notice bibliographique
Résumé
The research reported in this thesis aimed at evaluating plasticizer effectiveness and biodegradation rates of diesters synthesised from four-carbon diacids esterified with a linear alcohols ranging from ethanol (C2) to octanol (C8), and one branched alcohol, 2-ethylhexanol. The diacids were chosen due to their structural resemblance to the phthalate molecule, of which two were unsaturated (i.e., maleate: cis; fumarate: trans) and one saturated (i.e., succinate). The goal of this thesis was to gain insight on the influence of the geometry of the central structure and the length and branching of the side chains on plasticizer efficiency and biodegradability. The plasticizer candidates were blended with PVC at varying concentrations and the plasticizer effectiveness was evaluated by the measurement of the glass transition temperature Tg, tensile testing, dynamic mechanical thermal analysis (DMTA), and surface hardness. The obtained results were then compared to similar blends containing the commercial plasticizers DEHP and DINCH®. Biodegradation properties were assessed by exposing the common soil bacterium Rhodococcus rhodocrous (ATCC 13808) to candidate plasticizers with hexadecane as carbon source. The results revealed important differences arising from central structures and indicated that the saturated (succinate) and the cis-structure (maleate) made for the most efficient plasticizers. Further studies of the succinate revealed that any groups hindering free rotation around the central chain of the molecule reduced its plasticizing efficiency. Side chain length was important and maximum efficiency occurred for a side chain length around six carbons. The added ethyl branch in those diesters with 2 ethylhexyl side chains was not found to have an enhancing effect on plasticizer effectiveness. The biodegradation experiments revealed a crucial influence of the central structure, as the saturated compound (succinate) was rapidly degraded and metabolite buildup was small and only transient. Between the two unsaturated compounds, those with the ester groups in trans position (fumarate) were more quickly degraded than those in cis-position (maleate); the latter showing almost no degradation over the course of the experiment. This could also explain the observed slow biodegradation of phthalate diesters, in which the ester groups are in a similar arrangement as in the maleate. Slower degradation rates were found with increasing side chain length as well as branching, but effects were not as important as that of the central structure. Nonetheless, when linear side chains were used, no or only small, transient buildup of the released alcohol was found, contrarily to 2-ethylhexanol which built up significantly during the according experiments.Taken together, dibutyl and dihexyl diesters of succinic- and maleic acid showed the most promising results in terms of plasticizer efficiency and biodegradability, yet further toxicological experiments are required to determine if these are truly "green" plasticizers.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».