Chemical Recycling of Polystyrene with Tertiary Amine Switchable Hydrophilicity Solvents
Bibliographic record
Abstract
Nearly 40 metric tonnes of expanded polystyrene (XPS) waste is collected through Kingston’s curbside recycling program annually before being outsourced to companies with the means to recycle it. However, transporting XPS foam products is not economically viable. Therefore, a significant challenge is finding an efficient way to reduce the volume of the XPS foam prior to transportation since it has a very low density, consisting of up to 98% air. Currently, XPS products are compacted physically which requires the use of expensive compactors and energy-intensive compression processes. In 2011, Jessop et al. demonstrated that N,N-dimethylcyclohexylamine (DMCHA), a solvent with relatively low toxicity and volatility, can be used to recycle XPS using a greener approach. DMCHA is relatively hydrophobic under neutral conditions (e.g., in water), but becomes more hydrophilic when exposed to carbonated water (CO2 dissolves in water, forming carbonic acid which protonates the DMCHA). I have worked on optimizing this process via the following steps. Firstly, the XPS is dissolved in a small volume of DMCHA in its hydrophobic, neutral form. Then, the PS-DMCHA mixture is added to carbonated water causing the DMCHA to become hydrophilic and to dissolve in the aqueous solution, resulting in a layer of PS on the surface. The PS can then be easily collected and air-dried. By adding a 30 wt.% PS/DMCHA solution to carbonated water at 60oC, I have been able to achieve a typical purity of 95 wt.% of the final XPS (i.e., 5 wt% of DMCHA remains in the XPS), determined by 1H NMR.
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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 | 0.001 |
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".