High-resolution 2D Raman mapping of mono- and bicomponent filament cross-sections

Approaches for the preparation and evaluation of hydrophilic polyethylene and polyethylene terephthalate microplastic particles suited for toxicological effect studies

When performing effect studies to investigate the impact of microplastic (MP) on cell lines, algae, or daphnia, it is advantageous if such experiments can be performed without the use of surfactants. The need for surfactants arises from the fact that finely milled pristine MP particles generally are hydrophobic. Methods for the preparation of larger amounts of hydrophilic and hence artificially aged MP particles and approaches for their characterization are of high importance. Here we present methods to artificially age polyethylene terephthalate (PET) and low-density polyethylene (PE) using alkaline and acidic treatments that reproducibly result in large quantities of particles below 5 µm with considerably increased hydrophilicity. The artificially aged MP particles were characterized using particle counting by single-particle extinction and scattering (SPES), particle size by laser diffraction measurements, zeta potential using electrophoretic light scattering, hydrophobicity index (Hy) through dark-field (DF) microscopy, chemical composition by inductively coupled plasma-mass spectrometry (ICP-MS), Fourier transform infrared (FTIR) microscopy, and Raman microscopy. The hydrophobicity index values obtained should allow the aged MP particles to be characterized as qualitative reference materials (RMs) with an ordinal property. Evidence for the maintained integrity and hydrophilicity of the artificially aged MP particles (in powder form) over time was obtained by measurements of zeta potential with a 33-month interval. Uniformity of subsampling with respect to particle number concentration in suspensions within a 10-day period was also investigated. It provided evidence for the possibility of reproducible spiking of a specific number of hydrophilic MP particles with relative standard deviations (RSDs) from 6.2 to 13.6%. For the development of future reference materials of artificially aged microplastics, they should be characterized for an ordinal property (artificial age as Hy-index) and nominal property (identity of PET or PE based on spectral matching).

Locally Self-Adjustive Smoothing for Measurement Noise Reduction with Application to Automated Peak Detection

Smoothing is a widely used approach for measurement noise reduction in spectral analysis. However, it suffers from signal distortion caused by peak suppression. A locally self-adjustive smoothing method is developed that retains sharp peaks and less distorted signals. The proposed method uses only one parameter that determines the global smoothness of data, while balancing the local smoothness using the data itself. Simulation and real experiments in comparison with existing convolution-based smoothing methods indicate both qualitatively and quantitatively improved noise reduction performance in practical scenarios. We also discuss parameter selection and demonstrate an application for the automated smoothing and detection of a given number of peaks from noisy measurement data.

Application of Infrared Pyrolysis and Chemical Post-Activation in the Conversion of Polyethylene Terephthalate Waste into Porous Carbons for Water Purification

In this study, we compared the conversion of polyethylene terephthalate (PET) into porous carbons for water purification using pyrolysis and post-activation with KOH. Pyrolysis was conducted at 400-850 °C, followed by KOH activation at 850 °C for samples pyrolyzed at 400, 650, and 850 °C. Both pyrolyzed and post-activated carbons showed high specific surface areas, up to 504.2 and 617.7 m2 g-1, respectively. As the pyrolysis temperature increases, the crystallite size of the graphite phase rises simultaneously with a decrease in specific surface area. This phenomenon significantly influences the final specific surface area values of the activated samples. Despite their relatively high specific surface areas, pyrolyzed PET-derived carbons prove unsuitable as adsorbents for purifying aqueous media from methylene blue dye. A sample pyrolyzed at 650 °C, with a surface area of 504.2 m2 g-1, exhibited a maximum adsorption value of only 20.4 mg g-1. We propose that the pyrolyzed samples have a surface coating of amorphous carbon poor in oxygen groups, impeding the diffusion of dye molecules. Conversely, post-activated samples emerge as promising adsorbents, exhibiting a maximum adsorption capacity of up to 127.7 mg g-1. This suggests their potential for efficient dye removal in water purification applications.

The molecular level degradation state of drift plastics in the Sea of Japan coastline

Polyethylene (PE) and polyethylene terephthalate (PET) are among the most abundant plastics polluting the oceans. However, their environmental fate depends on how they have been weathered. Due to its unique geography, the Sea of Japan is a pollution hotspot where plastics accumulate. In this study, the structures of plastics, having drifted into the Sea of Japan coastline environment, were analyzed with a particular focus on examining polymer crystallization and carbonyl formation; two factors which influence microplastic formation and the adsorption of contaminants onto plastic surfaces. PE in the coastal environment did not show evidence of crystallization, although carbonyl formation did increase. By contrast, PET bottles were shown to not be uniform in structure, with unaged bottles being less crystalline in the neck component compared to the body. Because of this difference, in environmental PET bottles, it was the bottle neck that showed increases in crystallization and carbonyl group formation.

Recent advances on melt-spun fibers from biodegradable polymers and their composites

Biodegradable polymers have become important in different fields of application, where biodegradability and biocompatibility are required. Herein, the melt spinning of biodegradable polymers including poly(lactic acid), poly(butylene succinate), polyhydroxyalkanoate (PHA), poly(ɛ-caprolactone) and their biocomposites is critically reviewed. Biodegradable polymer fibers with added functionalities are in high demand for various applications, including biomedical, textiles, and others. Melt spinning is a suitable technique for the development of biodegradable polymer fibers in a large-scale quantity, and fibers with a high surface area can be obtained with this technique. The processing variables during spinning have a considerable impact on the resulting properties of the fibers. Therefore, in this review, the processing-property relationship in biodegradable polymers, blends, and their composites is provided. The morphological characteristics, load-bearing properties, and the potential application of melt-spun biodegradable fibers in various sectors are also provided.

Effects of Nanoscale Morphology on Optical Properties of Photoluminescent Polymer Optical Fibers

Bicomponent photoluminescent polymer optical fibers (PL-POFs) have been melt-spun and in-situ drawn to different extents. The results suggest that scattering in the sheath can effectively increase the photoluminescent dye excitation probability in the fiber core. The core/sheath PL-POFs are made of a semi-crystalline fluoropolymer sheath of low refractive index (RI) and an amorphous cycloolefin polymeric core of high RI, which is doped with a luminescent dye. The axial light emission, as well as the guiding attenuation coefficients of the core/sheath PL-POFs, have been measured using a side-illumination set-up. The incident blue laser is down-converted to red light, which is re-emitted and partially guided by the core. The axial light emission is measured at the fiber tip as a function of the distance of the illumination position to the integrating sphere. It is demonstrated that the presence of a semi-crystalline sheath significantly enhances the axial light emission and that it also lowers the attenuation coefficient, compared to the emission and guiding properties of PL core-only fibers. Additionally, the attenuation coefficient has been found to be lower in more strongly drawn PL-POFs. Wide-angle X-ray diffraction and small-angle X-ray scattering experiments reveal structural differences in differently drawn PL-POFs that can be linked to the observed differences in the optical properties.

Recyclability of Opaque PET from High Speed Melt Spinning: Determination of the Structures and Properties of Filaments

Recycling opaque Polyethylene terephthalate (PET), which contains 1 to 10 wt % TiO₂ submicron particles, has become of interest in the past few years. However, the bottle-to-fiber recyclability of opaque PET has not been assessed yet. In this work, opaque PET packaging has been characterized, and high-speed melt-spun filaments with different amounts of opaque PET (30–50–100%) blended with standard transparent recycled PET (rPET) have been produced in a pilot system. The opaque PET filaments produced have also been compared to a transparent rPET blend with masterbatch PET/TiO₂ at different amounts of filler (1–3–6 wt %), produced with the same parameters. The structure-properties relationship of rPET melt-spun fibers has been investigated with crystallinity measurements, amorphous and crystalline phases orientation, and tenacity. It has been observed that the degree of crystallinity, the crystalline and amorphous phases orientation and the tenacity decreases with opaque PET addition and, to a lesser extent, with TiO₂ addition. It has been suggested that TiO₂ particles are not entirely responsible for the decrease in mechanical properties of opaque PET filaments since opaque rPET filaments have inferior properties to r-PET/TiO₂ filaments at the same filler content.

Structure-Property Relationship in Melt-Spun Poly(hydroxybutyrate-co-3-hexanoate) Monofilaments

Poly(hydroxybutyrate-co-3-hexanoate) (PHBH) is a biodegradable thermoplastic polyester with the potential to be used in textile and medical applications. We have aimed at developing an upscalable melt-spinning method to produce fine biodegradable PHBH filaments without the use of an ice water bath or offline drawing techniques. We have evaluated the effect of different polymer grades (mol% 3-hydroxy hexanoate, molecular weight etc.) and production parameters on the tensile properties of melt-spun filaments. PHBH monofilaments (diameter < 130 µm) have been successfully melt-spun and online drawn from three different polymer grades. We report thermal and rheological properties of the polymer grades as well as morphological, thermal, mechanical, and structural properties of the melt-spun filaments thereof. Tensile strengths up to 291 MPa have been achieved. Differences in tensile performance have been correlated to structural differences with wide-angle X-ray diffraction and small-angle X-ray scattering. The measurements obtained have revealed that a synergetic interaction of a highly oriented non-crystalline mesophase with highly oriented α-crystals leads to increased tensile strength. Additionally, the effect of aging on the structure and tensile performance has been investigated.

Fitting of 2D WAXD data: Mesophases in polymer fibers

This data article presents fitting results of wide-angle x-ray diffraction (WAXD) patterns of melt-spun polymer fibers from amorphous materials (polycarbonate (PC), cyclo-olefin polymer (COP), copolyamide (coPA), polyethylene terephthalate glycol (PETG)) and semi-crystalline materials (polyethylene terephthalate (PET), poly-3-hydroxybutyrate(P3HB)). The data was fit using the fitting algorithms, previously described in the publication by Perret and Hufenus ‘Insights into strain-induced solid mesophases in melt-spun polymer fibers’ [1]. Fitting results of WAXD data and details about azimuthal, equatorial, meridional or off-axis profiles are presented in sections 1.1-1.2. SAXS patterns of fibers, melt-spun from amorphous materials, are shown in section 1.3. Fiber production parameters are given in section 2.1, and a description of the WAXD measurements and fitting details, e.g., the chosen fitting parameters, are given in section 2.2.

2D Raman, ATR-FTIR, WAXD, SAXS and DSC data of PET mono- and PET/PA6 bicomponent filaments

This data in brief article summarizes structural data obtained from monocomponent melt-spun and offline drawn poly(ethylene terephthalate) (PET) monofilaments, as well as from melt-spun bicomponent core-sheath PET-polyamide 6 (PA6) filaments. The diameters of the single filaments range from 27 µm to 79 µm. Presented analysis techniques and results thereof are (i) Raman mapping of filament cross-sections: 2D maps of peak positions, widths, peak area ratios; (ii) attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR): ATR-FTIR spectra and extraction of surface crystallinity; (iii) wide-angle x-ray diffraction (WAXD): WAXD patterns and extraction of average crystallinity; (iv) small-angle x-ray scattering (SAXS): SAXS patterns and determined crystallite sizes and long-spacings; (v) differential scanning calorimetry (DSC): thermograms and extracted average crystallinity as well as thermal properties; (vi) atomic force microscopy (AFM): AFM image of the surface of an embedded fiber cross-section. For more information, see the publication by E. Perret et al. 'High-resolution 2D Raman mapping of mono- and bicomponent filament cross-sections' [1].