Application of a Hybrid Fusion Classification Process for Identification of Microplastics Based on Fourier Transform Infrared Spectroscopy.

Microplastic research is an emerging field. Consistent accurate identification of microplastic polymer composition is vital for understanding the effect of microplastic pollution in the environment. Fourier transform infrared (FT-IR) spectroscopy is becoming commonplace for identifying microplastics. Conventional spectral identification is based on library searching, a process that utilizes a search algorithm against digital databases containing single spectra of pristine reference plastics. Several conditions on environmental microplastic particles such as weathering, additives, and residues cause spectral alterations relative to pristine reference library spectra. Thus, library searching is vulnerable to misidentification of microplastic samples. While a classification process (classifier) based on a collection of spectra can alleviate misidentification problems, optimization of each classifier (tuning parameter) is required. Additionally, erratic results relative to the particular optimized tuning parameter can occur when microplastic samples originate from new environmental or biological conditions than those defining the class. Presented in this study is a process that utilizes spectroscopic measurements in a hybrid fusion algorithm that depending on the user preference, simultaneously combines high-level fusion with low- and mid-level fusion based on an ensemble of non-optimized classifiers to assign microplastic samples into specific plastic categories (classes). The approach is demonstrated with 17 classifiers using FT-IR for binary classification of polyethylene terephthalate (PET) and high-density polyethylene (HDPE) microplastic samples from environmental sources. Other microplastic types are evaluated for non-class PET and HDPE membership. Results show that high accuracy, sensitivity, and specificity are obtained thereby reducing the risk of misidentifying microplastics.

Mechanical characteristics of medical grade UHMWPE under dynamic compression.

The mechanical properties of medical grade ultrahigh molecular weight polyethylene (UHMWPE) are critical for the safety and integrity of UHMWPE implantation. Accordingly, the mechanical features of UHMWPE are tested under repeated stress-controlled and strain-controlled compression at room temperature. Some important effect factors, such as stress rate, mean stress, stress amplitude, strain rate, mean strain, strain range and multiple load steps are further considered in detail. Results indicate that the lower stress rate causes the greater accumulated plastic strain and the accumulated plastic strain rate becomes increasingly lower with increasing number of cycles. The strain range and accumulated plastic strain rate decrease rapidly in the first stage, and then become almost steady during the second stage. Especially, the accumulated plastic strain rate per cycle for each case is less than 0.01 %/cycle after the initial 100 cycles. This means that the plastic strain accumulates very slowly and the shakedown behavior always occurs. Moreover, obvious cyclic softening and stress relaxation behaviors can be observed under cyclic strain-controlled compression during the first 50 cycles. This indicates that the accumulated plastic stain in the initial 100 cycles and the cyclic stress relaxation during the first 50 cycles should be assessed for the functionality of UHMWPE implantation.

Outcome of isolated polyethylene tibial insert exchange after primary cemented total knee arthroplasty.

PURPOSE: Total knee arthroplasty using a modular design gives the possibility for an isolated exchange of the tibial polyethylene insert in patients with failed total knee arthroplasty. The success of this kind of surgery is still controversial. We analysed the clinical outcome after isolated tibial polyethylene insert exchange. METHODS: In this retrospective study we included 62 consecutive patients with an isolated tibial polyethylene insert exchange at our institution. The average follow-up was 35 months. For clinical evaluation we used the Oxford Knee score, the Knee Society score, the Turba score, and the Kujala score. The health-related quality of life was determined with the SF-36 score and the visual analogue pain scale. RESULTS: The operations were performed 73 months after primary total knee arthroplasty on average. The main reasons for isolated tibial polyethylene insert exchange were instability and wear. In the clinical outcome patients achieved 31.5 points in the Oxford Knee score, 120.5 points in the Knee Society score, 9.3 points in the Turba score, and 49.0 points in the Kujala score. Mean level of persisting pain was 2.2. In the SF-36 score patients achieved 36.3 points physical and 51.7 points mental. The overall survival for isolated tibial insert exchange revealed 72.2 % survival at 6.25 years follow-up with a repeat revision rate of 11 %. CONCLUSIONS: Isolated tibial polyethylene insert exchange revealed a good clinical outcome. There is a tendency for better results in comparison with the information given in literature for most of the parameters including a lower rate in repeat revision.

Characterization of post-consumer polyolefin wastes by hyperspectral imaging for quality control in recycling processes.

In this paper new analytical inspection strategies, based on hyperspectral imaging (HSI) in the VIS-NIR and NIR wavelength ranges (400-1000 and 1000-1700 nm, respectively), have been investigated and set up in order to define quality control logics that could be applied at industrial plant level for polyolefins recycling. The research was developed inside the European FP7 Project W2Plastics "Magnetic Sorting and Ultrasound Sensor Technologies for Production of High Purity Secondary Polyolefins from Waste". The main aim of the project is the separation of pure polyethylene and polypropylene adopting an innovative process, the magnetic density separation (MDS). Spectra of plastic particles and contaminants resulting from post-consumer complex wastes and of virgin polyolefins have been acquired by HSI and by Raman spectroscopy. The classification results obtained applying principal component analysis (PCA) on HSI data have been compared with those obtained by Raman spectroscopy, in order to validate the proposed innovative methodology. Results showed that HSI sensing techniques allow to identify both polyolefins and contaminants. Results also demonstrated that HSI has a great potentiality as a tool for quality control of feed (identification of contaminants in the plastic waste) and of the two different pure polypropylene and polyethylene flow streams resulting from the MDS-based recycling process.