Preparation of Nanoscale Particles of Five Major Polymers as Potential Standards for the Study of Nanoplastics

Abstract

the environment. Also, despite low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), and polystyrene (PS) being the most prevalent polymers in the world, [6] more than 90% of toxicity studies using nanoplastics have examined only PS or poly(methyl methacrylate). [3] Thus, standard nanoplastic particles of the polymers most commonly encountered in the environment are urgently needed. [3,5] Ideally, such standard nanoplastic particles should not contain impurities, should have morphologies that can be defined for standardization, and should have properties that are comparable with those of commercial polymers. Impurities should be avoided because they may cause matrix interference during instrumental analysis as well as unexpected effects on the organisms during toxicity tests, and they may also alter the properties of the particles (e.g., alter their chemical adsorption behavior). Spherical shape was targeted in this study because the sphere, which is the simplest uniform shape, is easily standardized. In addition, spherical particles can be used as a fundamental reference shape to explore how different morphological features affect the behavior or toxicity of particles. The properties of the particles should be comparable with those of commercial polymers because nanoplastics are fragments of commercial plastic products that break off during use or after disposal.Although several types of commercial nanoplastic particles are currently available, their properties make them unsuitable for use as standard materials. PS and PVC nanoparticles prepared by emulsion polymerization are available; however, this method can result in particles containing high concentrations of impurities such as surfactants. [7] Although PS particles can be prepared by surfactant-free emulsion polymerization, use of this method results in an electrostatic charge on particles that may alter their behavior in organisms. [8,9] In addition, functional monomers such as acrylic acid are commonly incorporated into surfactant-free emulsion polymers. [8] Nanoplastic particles are also commercially available for LDPE, but they are composed of extremely low molecular weight polymers (weightaverage molecular weight [M w ] < 10 kg mol −1 , as determined in our laboratory) compared with that reported for the commercial polymer (M w = 30-400 kg mol −1 ). [10,11] To date, several methods for preparing nanoplastic particles using grinding (e.g., by a ball mill), polymerization, Nanoplastics are likely ubiquitous in the environment, and their potential toxic effects are a concern. However, quantitative information about the distribution of nanoplastics is still lacking, and toxicity tests are limited to a few select polymers because of the lack of appropriate standard materials, which should be nanoscale particles with standardizable morphologies, properties comparable to those of commercial polymers, and no impurities. Here, a precipitation-based method for preparing spherical nanoscale particles wit...

Size-Controlled Preparation of Polyethylene Nanoplastic Particles by Nanoprecipitation and Insights into the Underlying Mechanisms

“…The number-average and weight-average molecular weights were 18.1 and 81.2, respectively, and the degree of crystallinity and melting temperature were 41.4% and 107.0 °C, respectively; 13 these parameters were all within the ranges reported in the literature for commercial polymers. 13 ■ NANOPRECIPITATION Nanoprecipitation was conducted as previously reported (Figure 1). 13 The experimental conditions used in the present study are listed in Table 1.…”

“…These roundness values were high enough for us to consider all of the particles obtained to be spherical. 13 The mean particle diameter increased linearly from 496 to 997 nm when the polymer concentration was increased from 1 to 10 mg•mL −1 (Figure 3C). This increase of particle size can be explained by the fact that the growth rate increased and the nucleation rate decreased in the same polymer concentration range (Figure 4).…”

“…Particle roundness was around 0.98 at polymer concentrations up to 20 mg·mL –1 and was slightly lower at polymer concentrations of 30 mg·mL –1 (0.96) and 40 mg·mL –1 (0.95) (Figure B). These roundness values were high enough for us to consider all of the particles obtained to be spherical …”

“…13 ■ NANOPRECIPITATION Nanoprecipitation was conducted as previously reported (Figure 1). 13 The experimental conditions used in the present study are listed in Table 1. The LDPE sheets were dissolved in xylene at 110 °C.…”

Quantitative assessment of in vivo distribution of nanoplastics in bivalve Ruditapes philippinarum using reliable SERS tag-labeled nanoplastic models

“…A universal emulsion method may be helpful to extend labeling plastic types to PE, PP, PVC, etc . 45…”