Beyond size and shape: Physicochemical properties of microplastic test materials generated by cryomilling

ORCID

Abstract

Cryomilling is a widely used method to generate microplastic test materials for environmental impact studies. To date, changes in physical, chemical and thermal properties, as well as potential contamination, in cryomilled materials have been inadequately assessed. Here, six polymer samples, including fossil-fuel based polymers (LDPE and PP) and bio-based polymers (PLA, PBS and a PLA/PBAT blend), were cryomilled with their physicochemical properties assessed before and after milling. Particle morphology was influenced by starting material form; pellets produced microplastic fragments whereas films produced thin flakes. Particle size distribution was polymer dependent but smaller size fractions were achieved by using a smaller milling chamber. Cryomilling retained bulk polymer chemical characteristics, including weathering-induced changes, indicating its suitability for generating microplastic test materials without significant alteration during processing. Contamination was negligible from both plastic and metal components of the milling apparatus, validating the use of cryomilled microplastics for leaching and ecotoxicological studies. While overall chemical integrity was preserved, cryomilling caused an increase in the degree of crystallinity in PP, PBS and PLA. These results provide crucial insight into material properties, beyond size and shape, to better understand the influence of physicochemical properties on particle behaviour and draw meaningful associations between generated and environmental microplastics.

Publication Date

2026-03-15

Publication Title

Journal of Hazardous Materials

Volume

506

ISSN

0304-3894

Acceptance Date

2026-02-20

Deposit Date

2026-05-28

Embargo Period

2027-02-28

Funding

This work has received funding from the Natural Environment Research Council (NERC) through United Kingdom Research and Innovation (UKRI) for the Centre of Doctoral Training in Sustainable Management of UK Marine Resources (CDT SuMMeR) under grant agreement NE/W007215/1. Cole, Wilde and Thompson acknowledge funding from the Natural Environmental Research Council project “BioRisk” (NE/V007351/1). Wilde was also supported by the Community for Analytical Measurement Science through a 2021 CAMS Lectureship Award funded by the Analytical Chemistry Trust Fund. The authors gratefully acknowledge the Plymouth Electron Microscopy Centre (PEMC, Plymouth, UK) for the support and assistance with the scanning electron microscopy. Billy Simmonds is thanked for the use of FTIR and ICP-MS and Richard Hartley for the use and help with analysis for particle size analysis. Dr Rachel Coppock for the preparation of the milled mulch film sample. Additionally, the authors thank Laura McGregor (SepSolve, Peterborough, UK) for the beta Chromspace software used for Py-GC-MS data analysis. This work has received funding from the Natural Environment Research Council (NERC) through United Kingdom Research and Innovation ( UKRI ) for the Centre of Doctoral Training in Sustainable Management of UK Marine Resources ( CDT SuMMeR ) under grant agreement NE/W007215/1 . Cole, Wilde and Thompson acknowledge funding from the Natural Environmental Research Council project “BioRisk” (NE/V007351/1). Wilde was also supported by the Community for Analytical Measurement Science through a 2021 CAMS Lectureship Award funded by the Analytical Chemistry Trust Fund .

Keywords

Contamination, Cryomilling, Crystallinity, Microplastics, Test materials

Additional Files
Cryomilling_SI.pdf (5297 kB)

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This item is under embargo until 28 February 2027

Additional Files

Cryomilling_SI.pdf (5297 kB)

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