Fine grinding of thermoplastics by high speed friction grinding assisted by guar gum

Abstract

High speed friction grinding has been used to grind plant and food substances in water but never been explored for grinding of thermoplastics like polylactic acid (PLA), low and high density polyethylene and polypropylene. Such grinding was investigated in this work and was made possible by using 0.5% guar gum solution instead of just water because increasing the viscosity of water reduced their settling and the speed of passing through the grinder. Tensile, flexural, and impact strengths of the plastics were studied and higher grinding efficiency of PLA could be explained by its low elongation‐at‐break compared to low density polyethylene, high density polyethylene, and polypropylene. The microplastics (2000–45 μm) were studied for mass and particle size distributions and by scanning electron microscopy, 13C CP/MAS NMR, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. In addition, viscosity of guar gum and contact angles was measured. This new technology can produce finely ground microplastics (710–45 μm) for a variety of applications.

Small micro- and nanoplastic test and reference materials for research: Current status and future needs

“…Furthermore, they typically do not allow the plastic-associated chemical composition of environmental sMP and NP to be replicated. A possible 'intermediary case' is the solvent-dissolution or melting of polymer particles in a solvent followed by extrusion or spray drying of particles in the desired size range (Bhagia et al, 2021). Using this approach, it is possible to partially retain the chemical composition of the plastics, but the physical properties (shape, density, porosity and morphology) are not representative of the particles formed from the degradation of larger particles or plastic items during use or in the environment.…”

“…Although yields were not explicitly reported, the authors describe stock solutions of the final NP materials at concentrations ranging from 4.8 to 40.8 μg mL À1 , which was sufficient for conducting toxicity tests in the study. A combination of dry and wet milling in water, solvent or surfactant has also been shown to improve the yield of lower size ranges (Bhagia et al, 2021), and has been applied in most of the studies reviewed herein (Table 1). The approach has achieved the production of nonhomogenous (in size and shape) particles for a range of polymers, including PS, PP, PE, PET, polybutylene adipate terephthalate and polyether ether ketone.…”

“…The approach has achieved the production of nonhomogenous (in size and shape) particles for a range of polymers, including PS, PP, PE, PET, polybutylene adipate terephthalate and polyether ether ketone. Wet high-speed friction grinding has recently been investigated as an option for the production of MP and sMP, and a significant improvement in the yield of PE, PP and PLA particles in the lower size range was obtained by modifying the aqueous grinding media with 0.5% guar gum (Bhagia et al, 2021). Minimal impact on the physicochemical properties was observed by this process.…”

The Relationship between a Rotational Molding Processing Procedure and the Structure and Properties of Biobased Polyethylene Composites Filled with Expanded Vermiculite

“…Additionally, it is ideal if the particle size distribution curve is Gaussian like. These properties are difficult to obtain because polymer materials are fragile to elevated temperatures, which can occur while grinding [ 6 ].…”