We were thinking to make a research about the different solvents we could use for our project, Precious Plastic. We feel it could be interesting for all the community to know more about this topic.Maybe we can use them to melt, to join, to weld, to finishing, to clean or whatever else you can think.
For this proposal I am going to make a list of different solvents that could work for the different plastics, research about them then test them and share what we find out about them.orIt could be very useful if you have experience with more solvents, share it here, and we can build altogether a kind of database of the solvents we can use and for which purpose they work.
Coming from different sources I have found this different solvents for the different kinds of plastics we usually use, this is just a little overview of this topic, because just I am not a chemist, I would be very thankful if someone who really knows about this topic could help us.
I will start with the solvents oriented to PE and PP, just because they are the more difficult to work with. I know that for PS and ABS the history suggests it will be easier.
I will avoid to talk about too dangerous, hazardous or just difficult to find solvents, but if you have any idea of more we can test here, we are open for new suggestions.
Methyl ethyl ketone (MEK) C4H8O: Also known as Butanone. A large component of almost all plastic cements especially ABS and polystyrene cement. Can be bought pure. As butanone dissolves polystyrene and many other plastics, it is sold as “model cement” for use in connecting parts of scale model kits. Though often considered an adhesive, it is actually functioning as a welding agent in this context.
https://www.ilo.org/dyn/icsc/showcard.display?p_lang=en&p_card_id=0179&p_version=2 (International chemical safety card)
Acetone C3H6O: Found in small quantities in nail polish remover. Also found in various plastic cements. Also found in acrylic paint thinners and varnishes. Can be bought pure.
https://www.ilo.org/dyn/icsc/showcard.display?p_lang=en&p_card_id=0087&p_version=2 (International chemical safety card)
Xylene C8H10: It is used as a solvent. In this application, with a mixture of isomers, it is often referred to as xylenes or xylol. Areas of application include the printing, rubber and leather industries. It is a common component of ink, rubber and adhesives. In thinning paints and varnishes, it can be substituted for toluene where slower drying is desired, and thus is used by conservators of art objects in solubility testing. It can solve PP at high temperature.
https://www.ilo.org/dyn/icsc/showcard.display?p_lang=en&p_card_id=0086&p_version=2 (International chemical safety card)
Hi, I’m Suvda from Mongolia, studying my MSc Chemical Engineering in Budapest. I will be helping out in V4 in the summer and a little bit remotely from here as well.
I have found some interesting research papers on solvents oriented to PE and PP. The papers are usually about dissolving the polymers completely and the dissolving processes usually required heated solvents at high temperatures. I believe we can use lower temperatures than the required dissolution temperatures for our use of joining, welding, melting and finishing.
Dissolution of polymers in solvents SUMMARY:
1. LDPE can be dissolved at 85C in Toluene, xylene and trichloroethylene (5ml toluene dissolved 0.3g LDPE in 2.5 min, xylene and trichloroethylene dissolved it in 3 min) (Source #1)
2. HDPE can be dissolved above 130C in Decaline with 99% purity (Source #2). PE can be dissolved in 1,2,4-trichlorobenzene+0.015% Butylated Hydroxytoluene at 160C (Source #3).
3. PP can be dissolved at above 165C in Decaline with 99% purity (Source #2). PP can be dissolved in 1,2,4-trichlorobenzene+0.015% Butylated Hydroxytoluene at 160C (Source #3).
Source #1: Study on Dissolution of Low Density Polyethylene (LDPE)
This paper was about solving the problem of pipelines clogged by molten plastic feed during pyrolysis process. They experimented with LDPE powder, pellet and sheet forms, but the difference between their solubility was quite low. The solvents needed to heated to 85C except for the trichloroethylene (due to its boiling point of 86.7C), it was heated to 80C to avoid boiling of solvent.
Solvents experimented were benzene (banned in EU), toluene, chlorobenzene, isooctane, xylene and trichloroethylene. They used 5ml of each solvent and 0.3g of LDPE powder (This amount is only for experiment of dissolution rather than the required amount). When LDPE powders dissolve in solvents they swell and change their color to colorless, before they dissolve into solution.
The result of the paper: Toluene (2.5 min needed to dissolve 0.3g LDPE), xylene (3 min) and trichloroethylene (3 min) were more preferable to be used, as they have similar performance to benzene, as well as less hazardous compared to benzene.
This paper was also interesting, because it mentioned about dissolution/precipitation method, which is dissolving and precipitating the plastic with high recovery and purity. The method can be helpful to separate mixed plastic waste according to their difference in solubility and different heating temperature. Also, in the pyrolysis process, the dissolved LDPE solution can be directly cracked without precipitating it.
Source #2: Preparation of Ultra Thin PS, PP and PE Films on Si Substrate Using Spin Coating Technology
The polymers used in this study were PS, PE and PP were supplied in pellet form. Because of the amorphous structure of polystyrene, dissolving PS is relatively easy. Toluene anhydrous 99.8 % (Sigma Aldrich) was chosen as a solvent for polystyrene. Heating of the PS solution in toluene to 50 °C for 2 hours was sufficient to completely dissolve the polymer.
Polyethylene and polypropylene have high crystallinity degree structures, which means that to ensure dissolving of polymer pellets in solvent, the solution should be heated above the polymer melting temperature. These are 120-130 °C for PE and 160-165 °C for PP. To ensure fast polymer dissolving, the solvent must have a boiling point that is higher or comparable with the above mentioned temperatures and so decaline, anhydrous 99 % purity (Sigma Aldrich, mixture of cis and trans) was used (boiling point range of 189-191 °C).
Solutions of PE and PP in tetrahydrofuran (THF) and toluene are possible but require more than 6 hours to be obtained. When decaline was used as a solvent and the temperature was above 160 °C, complete polymer dissolving in both PE and PP cases were obtained in less than 3 hours. After the solution has been obtained, great care must be taken with its handling.
Source #3: Polymer-to-Solvent Reference Table
This table is for the Gel Permeation Chromatography where they use polymers in their appropriate solvent. From the tables, PS can be dissolved in Tetrahydrofuran (THF) at 25C, PP and PE can be dissolved in 1,2,4-trichlorobenzene+0.015% Butylated Hydroxytoluene at 160C. This method can be better than the Source #2 method since the PE, PP can be dissolved at low T.
Safety: Before working with any substance we need to read the MSDS of the substance. In the solvents case we need powerful fume extractor, goggles, sleeve length lab gloves and masks.
I will add on this forum topic whenever I have something substantial to share 🙂
It is great to see this topic addressed here. If there is time, if this topic could be expanded to include label adhesive solvents, hopefully find an earth friendly process.
Looking forward to your activities.
Test: To solve PP and PE with Xylene
Objective: To solve PP and PE with Xylene
Material: PP, HDPE, LDPE
Tools: Gloves, Mask, Safety glasses, little mug, Xylene
To shred some different kinds of PP, HDPE and LDPE.To put some Xylene in a mug.To put some flakes inside the mug with the Xylene and close the mug (if you do not close the mug, the solvent is going to evaporate with the air).To leave them for around 36h at room temperature.
This kind of plastics are really hard to solve in organic solvents, that because I was using Xylene. I know that it can be solved at higher temperatures during more time, but I realized that is not a point for our project to use solvents + temperature during long time, because we were going to use too much sources to reach the solution. It finally did not work.
Test: To solve PET with Acetone, MEK and D-Limonene
Objective: To solve PET
Tools: Gloves, Mask, Safety glasses, little mug, Acetone, MEK and D-Limonene
To shred PET. To put some Aceton, MEK and D-Limonene in different mugs.To put some PET flakes inside the mugs and close the mugs(if you do not close the mug, the solvent is going to evaporate with the air). To leave them for around 36h at room temperature.
It finally did not work.
Test: Melt PP and HDPE with Xylene
Objective: Melt PP and HDPE with Xylene
Material: PP flakes, HDPE flakes, Xylene (Cas number: 1330-20-7), glass
Precautions: Safety mask, safety glasses, gloves.
To shred some PP and HDPE and mixed it in a glass with xylene. 0.3g of plastic on 5ml of Xylene. Leave the mix at different temperatures and different times.
I have left the last experiment (after being 90’ at 110ºC) all night long (approx 12h)
Looks like the Xylene could work with these plastics, but with higher temperature and more time. This means that we are going to put on it too many sources on this task, that is the reason because I have stopped at that temperature and timing.
After leaving the last experiment 12h more, I have realized that the HDPE looks kind of melted, I have tested it before, but the HDPE was completely destroyed after being dried. I have also tried to stick it to another piece of HDPE but it was completely destroyed.
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