Evaluation of maleate, fumarate, and succinate diesters as potential green plasticizers
Bibliographic record
Abstract
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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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".