Department of Chemical Engineering, Indian Institute of Technology Guwahati, India

*Author to whom correspondences should be addressed. Email: dipban@iitg.ernet.in

Micro-nano plastic release affects our environment in multiple ways, and mitigation of this problem is still something that

is not understood completely. This study aims to understand the physics of Micro-Nano-Plastics (MNPs) released from the

inner polymer layer of a paper cup. Ingestion of MNPs through regular intake of hot beverages such as coffee and tea can

manifest potential health hazards in the future. Disposable paper cup releases MNPs within 10 min due to thermal

exposure to hot water/substance (90 - 110 °C). Surface instability leads to a spike in deformation and even disintegration

of such a film.

restricting substrates, the viscosity or density-imposed

stratification of the fluid layers, the ratio of the layer

thickness, velocity or stress jump across the surface

boundaries, and others to list is demonstrated by (Charru

et al., 1994). Extensive experimental and theoretical

efforts are being made to investigate the prominent

aspects of stratified two-layer fluid flow instabilities.

Past theoretical and experimental research indicates that

the bilayer pressure-driven Poiseuille flow (PPF) or

Couette flow (CF) can be unbalanced via finite-wave-

1983). Gravity, thermocapillary and electrostatic fields

drive interface instabilities. Linear stability primarily

discusses the destabilizing influence of heating the

system either at the top or bottom (Merkt et al., 2005),

investigated the extended-time morphology of patterns

such as holes, drops, or maze-like structures wherein

they used a variational formulation approach to obtain an

evolution equation grounded on an energy function with

the prediction of metastable states.

The release of MNPs from disposable paper cups is of

instability problem as enhanced chain mobility (ECM)

above the GTT of the polymer allows the initiation of

surface instability leading to a spike in deformation. An

even disintegration of such a film occurs when the hot

fluid with a temperature above 96 °C is brought into

contact with these linings. So thin polymer inner film

begins to rupture because of instability-induced

disintegration. Recent findings claim that these MNP

particles can travel around the body and may lodge in

organs. One of the alarming reason for the research and

The above system replica was made using thin paper

film on a glass substrate coated with polystyrene. When

the system is exposed to hot water, the inner

hydrophobic polymer film begins to dewet. The release

of Micro- Nano-Plastics has been characterized. FESEM

and AFM confirm the morphological alteration at the

polymer hot water interface. Finally, XRD

characterization confirms the presence of released

microplastic in the hot water content. Fig. 2 (a) and (b)

release under a thermal gradient of hot water, enhanced

chain mobility (ECM) above the glass transition

temperature (GTT) of the polymer allows the initiation

of surface instability leading to a spike in deformation

and even disintegration of the inner plastic film when the

hot fluid which is having a temperature above 96 °C

degraded cup surfaces under the thermal influence of hot

water, respectively. Images (c) and (d) show FESEM

images of normal and degraded cup surfaces under hot

water's thermal influence, respectively. Image (e) XRD

confirms the presence of released polystyrene MNP

inside hot water content after 10 min of exposure.

The roughness changes significantly upon exposure to

hot water from

typical inner polymer film to

Fig. 2(c) and (d) show FESEM images of normal cup

film ruptures, some MNP seeps into the hot water, and

some degrade and becomes rough. Fig. 2(e) XRD

confirms the presence of released polystyrene MNP

inside hot water content after 10 min of exposure.

1) Under the thermal influence, disposable paper

cup releases (MNPs) within 10 min of exposure, the

final content of the cup was then analysed under XRD

that showed a peak for PS, confirming that the polymer

morphology of the inner hydrophobic surface of the

film are reflected by AFM images. A significant surface

roughness improvement was observed on hot water

exposure to the film. Therefore, investigation infers that

the hot water exposure to the paper cups breaks down

the hydrophobic layer's physico-chemical and

mechanical properties.

1. Craster, R.V. & Matar. (2009). Dynamics and stability

of thin liquid films. Reviews of modern physics, 81(3),

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4. Merkt, D., Pototsky, A., Bestehorn, M. & Thiele, U.

(2005). Long-wave theory of bounded two-layer films

with a free liquid–liquid interface: short-and long-time

evolution. Physics of Fluids, 17(6).

5. Ranjan, V.P., Joseph, A. & Goel, S. (2021).

Microplastics and other harmful substances are released

from disposable paper cups into hot water. Journal of

Hazardous Materials, 404, 124118.

6. Beavers, G.S. & Joseph, D.D. (1967). Boundary

Health, 13; 17(4):1212. doi: 10.3390/ijerph17041212.

PMID: 32069998; PMCID: PMC7068600.