Analysis of thermally and UV-Vis aged plasticized PVC using UV-Vis, ATR-FTIR and Raman spectroscopy

Non-destructive detection and identification of plasticizers in PVC objects by means of machine learning-assisted Raman spectroscopy

Vibrational spectroscopic techniques, such as Raman spectroscopy, as a non-destructive method combined with machine learning (ML), were successfully tested as a quick method of plasticizer identification in poly(vinyl chloride) - PVC objects in heritage collection. ML algorithms such as Convolutional Neural Network (CNN), Random Forest (RF), Support Vector Machines (SVM), and Linear Discriminant Analysis (LDA) were applied to the classification and identification of the most common plasticizers used in the case of PVC. The CNN model was able to successfully classify the five plasticizers under study from their Raman spectra with a high accuracy of (98%), whereas the highest accuracy (100%) was observed with the RF algorithm. The finding opens doors for the development of robust and economical tools for conservators and museum professionals for fast identification of materials in heritage collections.

Mattel's ©Barbie: Preventing Plasticizers Leakage in PVC Artworks and Design Objects through Film-Forming Solutions

The main conservation problem of p-PVC artworks is phthalate-based plasticizer migration. Phthalate migration from the bulk to the surface of the materials leads to the formation of a glossy and oily film on the outer layers, ultimately reducing the flexibility of the material. This study aimed to develop a removable coating for the preservation of contemporary artworks and design objects made of plasticized polyvinyl chloride (p-PVC). Several coatings incorporating chitosan, collagen, and cellulose ethers were assessed as potential barriers to inhibiting plasticizer migration. Analytical techniques including optical microscopy (OM), ultraviolet/visible/near-infrared spectroscopy (UV/Vis/NIR), Fourier transform infrared spectroscopy with attenuated total reflection (FTIR-ATR), and scanning electron microscopy (SEM) were utilized to evaluate the optical and chemical stability of selected coating formulations applied to laboratory p-PVC sheet specimens. Subsequently, formulations were tested on a real tangible example of a design object, ©Barbie doll, characterized by the prevalent issue of plasticizer migration. Furthermore, the results obtained with the tested formulations were evaluated by a group of conservators using a tailored survey. Finally, a suitable coating formulation capable of safeguarding plastic substrates was suggested.

Leaching behaviors of dissolved organic matter from face masks revealed by fluorescence EEM combined with FRI and PARAFAC

Despite numerous studies investigating the occurrence and fate of microplastics, no effort has been devoted toward exploring the characteristics of dissolved organic matter (DOM) leached from face masks mainly made of plastics and additives used in large quantities during the COVID-19 pandemic. By using FTIR, UV-vis, fluorescence EEM coupling with FRI and PARAFAC, and kinetic models of leaching experiments, we explored the leaching behaviors of face mask-derived DOM (FM-DOM) from commonly used face masks including N95, KN95, medical surgical masks, etc. The concentration of FM-DOM increased quickly at early 0-48 h and reached equilibrium at about 48 h measured in terms of dissolved organic carbon and fluorescence intensity. The protein-like materials ranged from 80.32 % to 89.40 % of percentage fluorescence response (Pi,n) were dominant in four types of FM-DOM analyzed by fluorescence EEM-FRI during the leaching experiments from 1 to 360 h. Four fluorescent components were identified, which included tryptophan-like components, tyrosine-like components, microbial protein-like components, and fulvic-like components with fluorescence EEM-PARAFAC models. The multi-order kinetic model (Radj2 0.975-0.999) fitted better than the zero-order and first-order kinetic model (Radj2 0.936-0.982) for all PARAFAC components of FM-DOM based on equations derived by pseudo kinetic models. The leaching rate constants (kn) ranged from 0.058 to 30.938 and the half-life times (T1/2) ranged from 2.73 to 24.87 h for four FM-DOM samples, following the solubility order of fulvic-like components (C4) > microbial protein-like components (C3) > tryptophan-like components (C1) > tyrosine-like components (C2) for FM-DOM from four types of face masks during the leaching experiment from 0 to 360 h. These novel findings will contribute to the understanding of the underappreciated environment impact of face masks in aquatic ecosystems.

Quantitative analysis of microplastics and nanoplastics released from disposable PVC infusion tubes

The exposure of micro- and nanoplastics (MNPs) via medical device is still unknown to us. Herein, a visual quantitative detection of polyvinyl chloride (PVC) MPs and a fluorescent quantitative detection of PVC NPs were developed. To overcome the aggregation of PVC NPs, sodium dodecylbenzene sulfonate was used as the stabilizer of PVC NPs. The brand-new disposable PVC infusion tubes were found to carry PVC MPs with the average total number (ATN) of 931.4 particles and PVC NPs with the average mass of 0.040 μg, respectively. For four typical infusion fluids such as 0.9% sodium chloride, 5% glucose, 5% sodium bicarbonate, hydroxyethyl starch 40 sodium chloride, the released PVC MPs and NPs were ranged from 1003.6 ∼ 3494.6 particles and 0.042 ∼ 0.087 μg, respectively in stimulating normal infusion scenario (room temperature 4 h). The released PVC MPs and NPs were also increased with the infusion duration and temperature. The released PVC MPs are mainly in granular form, accounting for 38 ∼ 49% of the total PVC MPs. Our findings indicate PVC MNPs can enter the blood vessel directly with the infusion fluids during intravenous infusion and the PVC MNPs exposure risk towards patients deserves more attention.

Influence of operating parameters on the yield of micro-plastics from plastics incineration

Plastics account for a large proportion of domestic waste. However, micro-plastics will be produced after the plastic is incinerated. The purpose of this study is to find out the change rule of micro-plastics produced during incineration under different conditions. Combining micro-FTIR and PCA algorithm is a good tool to identify the micro-plastics. The PE, PP and PVC micro-plastics are distinguished using PCA-FTIR spectra. The results show different incineration conditions significantly affect the output of micro-plastics. The yield of micro-plastics increases with increasing temperature for both PP and PVC. And the yield of micro-plastics decreases with the increase in flow rate. The maximum amount of micro-plastics is produced by PE, which is 6.62 × 103 after 1 g PE incineration. The yield of micro-plastics in the co-incineration of PE and PP, as well as PE and PVC, significantly increased to 1.42 and 1.89 times of the calculated values, respectively. The nano-particles are also observed. The FTIR and EDS results show that the nano-particles are the products of incineration of plastics, including partly CH bond and unburned carbon, tar and ash.

Non-destructive recognition of copy paper based on advanced spectral fusion and feature optimization

In order to provide more clues for ongoing investigations and case handling, as well as achieve fast, non-destructive, and accurate identification of copy paper found at crime scenes, this study aims to utilize advanced spectral fusion technology to characterize and identify the three-dimensional features of the "origin-manufacturer-brand" of copy paper. Confocal Raman Microscopic and Fourier transform infrared spectroscopy were employed to collect spectral data from 200 samples from four regions (Shandong, Henan, Shaanxi, Jiangsu). The effects of different preprocessing methods, such as Hilbert transformation and deconvolution, on the model's ability to distinguish were compared. Feature variables were extracted using principal component analysis, and Bayesian discriminant classification models were constructed based on single infrared spectroscopy, Raman spectroscopy, and three types of spectral fusion datasets. By comparing the classification accuracy of different models, the primary fusion based on the full spectrum dataset was selected as the optimal model for the three-dimensional feature classification of copy paper. The accuracy achieved for origin (96%), manufacturer (100%), and brand (100%) was satisfactory, and the classification results were highly accurate. This study provides valuable insights and serves as a reference for its application in forensic science research.

Towards the Understanding of the Aging Behavior of p-PVC in Close Contact with Minced Meat in the Artwork POEMETRIE by Dieter Roth

This paper presents scientific investigations into the materiality and aging behavior of a copy of Dieter Roth's multiple POEMETRIE (1968), mainly made of p-PVC components and minced meat, with the aim of informing conservation-restoration strategies. The main issues were represented by plasticizer migration, fat diffusion, and leakage, which led to the formation of a sticky surface layer. Replicas of p-PVC without minced meat were prepared and artificially thermally aged, while several techniques were used to investigate both the artwork and the replicas in terms of materials and degradation state. These include UV/Vis imaging, pH measurements, FTIR-ATR, and Py-GC/MS. In addition to showing that p-PVC-based materials composed of slightly different plasticizers were affected by similar degradation pathways (i.e., plasticizer migration, yellowing, etc.), this study reports that fat components were also shown to be unstable, resulting in migration/leakage in different directions, where their degradation amplified that of the p-PVC bags. This work represents a first study of plasticizer migration and fat diffusion in the art and conservation context. Also, an ammine-wax type of lubricant was identified in the most recent p-PVC formulations as the replicas selected for this study, thus providing an important source of information in different polymer-based research areas.

Effect of solvents on intra- and inter-molecular interactions of oligothiophenes

CONTEXT

Oligothiophenes have long been used as model compounds to understand the chemistry of polythiophenes. Herein, we have some quantum chemical calculations and intra- and inter-molecular interaction calculations of a series of oligothiophenes such as terthiophene, quintetthiophene, sevensthiophene, terthiophene-terthiophene, terthiophene-water, terthiophene-methanol, and terthiophene-chloroform performed by time-dependent density functional theory (TD-DFT), density functional theory (DFT), and Multiwfn: a multifunctional wavefunction analyzer. The UV-vis spectra, HOMO-LUMO energies, NBO analysis, MEP, molecular structures, and electronic properties were computed using DFT/TD-DFT at the level of B3LYP/6-31+ G (d,p) and described. The nature of molecular interactions between terthiophene and solvents like water, methanol, and chloroform were also investigated using non-covalent interaction index (NCI), reduced density gradient (RDG), localized orbital locator (LOL), and electron localization function (ELF) topological analyses. Besides, Fukui functions and energy of population density-of-states were computed using the same method. The calculation results show that there are some changes in the terthiophene with the addition of solvent to the medium.

METHODS

DFT calculations were performed using the Gaussian 09 software and GaussView 5.0 visulation program. Multiwfn software is used to calculate the reduced density gradient (RDG) scatterplots, non-covalent interactions (NCI), ELF, LOL, Fukui analysis, and energy of population density-of-states of oligothiophenes.