Engineering
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Forming Micro-and Nano-Plastics from Agricultural Plastic Films for Employment in Fundamental Research Studies
Chapters
Summary July 27th, 2022
We show the formation and dimensional characterization of micro- and nanoplastics (MPs and NPs, respectively) using a stepwise process of mechanical milling, grinding, and imaging analysis.
Transcript
Anton Astner:This protocol describes the preparation of engineered micro and nanoplastics sourced from a wide range of polymer feed stocks, such as pellets and films representing authentic model materials. This method efficiently forms micro nanoplastics through a simple mechanical procedure involving cryogenic milling, seething and wet grinding that can serve a surrogate materials for environmental studies. To begin retrieve foam from roll and cut P B A T foam into strips with a paper cutter pre soak fragments in deionized water for 10 minutes and transfer the foam material into a cryogenic container.
Slowly add 200 milliliters of liquid nitrogen to a cryogenic container transfer pres soaked foam fragments or pellets carefully into the cryogenic container with steel tweezers. Next, transfer frozen foam fragments or pellets into a blender and process for 10 seconds. Add 400 milliliters of DI water and blend the foam water slurry for five minutes.
Transfer slur into a buchner funnel with a filter and apply vacuum for one hour. Then transfer the sample with the funnel into a vacuum oven. Dry at 30 degrees Celsius for at least 48 hours.
Weigh polymer film or pellet samples and transfer into a 50 milliliter glass jar. Place the rectangular delivery tube with a 20 mesh seed in the slot in front of the rotary cutting milk and raise the delivery tube until it hits the stock pin. Position the glass plate over the milling chambers face and secure it with the adjustable clamp.
Next place a 50 milliliter glass jar under the mill outlet. Position the sliding side arm support on the mill slightly off center on the front glass and tighten with the neural bolt. Insert the hopper funnel on top of the mill into the opening of the upper milling chamber.
Plug a line cord into a power outlet and press the cord switch to start the mill operation. Feed the sample slowly and add the next batch of film or pellet fragments after the audible noise reduces. After processing the film or pellet fragments press the cord switch to stop the mill operation for approximately 20 minutes to cool down.
Clean the cutting chamber with a spatula and bristle brush And collect particles in the glass jar. Remove the 20 mesh 840 micrometer delivery tube and replace it with the 60 mesh delivery tube. Upon completion of the first batch reintroduce the collected material into the mill hopper.
Follow the same procedure for the 60 mash milling fraction. Recover the remaining particles in the chamber and add them to the collected main fraction. Prepare a slurry of microplastics.
Start by taking di water into a glass beaker and insert a stirring bar. Introduce eight grams of the collected 250 micrometer plastic fraction. Place the glass beaker on a stirring plate and stir magnetically for 24 hours at 400 rotations per minute.
To soak the particles in water transfer the particles into a plastic container. Fill in additional two one liter plastic containers with di water, which will be used to rinse off endearing particles on the grinder's hopper. During the grinding process.
Place stones with a 46 green size in the wet friction grinder and fasten the center nut. Hand tight with a 17 millimeter wrench add the hopper on top and fasten the four bolts with the five millimeter Allen wrench. Place a one liter plastic collection jar under the outlet of the collider.
Place a second empty one liter bucket next to the outlet which will be used for exchanging while processing. Switch the power on and carefully adjust the gauge clearance by turning the adjustment wheel clockwise, corresponding to a positive 0.10 micrometer shift from the zero position until hearing the grinding stones touch. Next, adjust the flexible measurement ring to zero and turn the wheel counterclockwise immediately.
By default, the speed is adjusted to 1500 revolutions per minute. Turn the adjustment wheel clockwise until the stones touch and gently fill the water nanoplastic slurry into the hopper. Decrease the gap continually to a clearance gauge of negative 2.0 corresponding to a negative 0.20 micrometer shift from the zero position after the slurry was introduced.
Collect the slurry by exchanging the collection buckets. Once the filling level and the bucket exceeds 0.5 liters collect and reintroduce the particles into the grinder between 30 to to 60 times higher. Passes result in smaller particle size.
Wash endearing particles on the hopper with the prepared DI water bottle to allow suitable slurry mixing while processing. Recover the slurry and stir for four hours at 400 rotations per minute at 25 degrees Celsius to allow it to mix well let the slurry stand for 48 hours to stabilize. The numerical analysis revealed the bimodal particle size distribution for nanoplastics produced from both feed stocks.
The main particle populations for nanoplastics from P B A T pallets were at approximately 79 and 530 nanometers, and corresponding number density frequency values were at 25 and 5%respectively. On the other hand, nanoplastics derived from P B A T foams possessed size maxima at approximately 50 and 106 nanometers with corresponding number density frequency values of 11 and 10%respectively. FTIR R results for P B A T Nanoplastics indicate a distinct decrease in absorbance values between 980 and 1200 centimeter inverse reflecting the starch component leaching during wet grinding.
Consistent with previous study observations Anton Astner:For microplastic formation from plastic film and pellets cryogenic pretreatment induces embrittlement to the plastics. It mimics the impact of environmental weathering but not perfectly, which allows accelerated defragmentation. The cryo milling procedure combined with the wet grinding process allows the processing of numerous differently plastic feed stocks to form authentical micro nanoplastics used in environmental studies studies.
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