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

Journal of Hazardous Materials 2026 Score: 40 ? 0–100 AI score estimating relevance to the microplastics field. Papers below 30 are filtered from public browse.

Matthew Cole Richard C. Thompson, Lucy Howarth-Forster, Lucy Howarth-Forster, Matthew Cole Lucy Howarth-Forster, Lucy Howarth-Forster, Lucy Howarth-Forster, Richard C. Thompson, Richard C. Thompson, Robyn Barrett, Matthew Cole Matthew Cole Richard C. Thompson, Richard C. Thompson, Lucy Howarth-Forster, Robyn Barrett, Matthew Cole Rob Clough, Richard C. Thompson, Richard C. Thompson, Richard C. Thompson, Richard C. Thompson, Richard C. Thompson, Rob Clough, Matthew Cole Lisbet Srensen, Lisbet Srensen, Matthew Cole Jack Allen, Richard C. Thompson, Richard C. Thompson, Richard C. Thompson, Jack Allen, Jack Allen, Chris Powell, Chris Powell, Matthew Cole Richard C. Thompson, Richard C. Thompson, Richard C. Thompson, Richard C. Thompson, Richard C. Thompson, Richard C. Thompson, Richard C. Thompson, Matthew Cole Richard C. Thompson, Matthew Cole, Michael Wilde, Michael Wilde, Richard C. Thompson, Matthew Cole Richard C. Thompson, Matthew Cole

Summary

This study rigorously characterized how cryomilling — a common laboratory method for grinding plastics into research-grade microplastic test materials — changes the physical and chemical properties of the resulting particles beyond just breaking them into smaller pieces. While the bulk chemical identity of polymers was preserved, milling increased the crystallinity of some plastics and produced different particle shapes depending on whether the starting material was pellets or films. These findings are important for interpreting laboratory toxicity studies, since the physical form of test microplastics can affect how particles behave in experiments.

Polymers

LDPE PLA PP

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.

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