Enhanced thermal stabilization and reduced color formation of plasticized Poly(vinyl chloride) using zinc and calcium salts of 11-maleimideoundecanoic acid

Organic fertilizer facilitates the soil microplastic surface degradation and enriches the diversity of bacterial biofilm

The land-use of organic fertilizers is considered as an important sustainable method for resource utilization, which may have an impact on the microplastic behaviors in the soil. Here, a 240-d dark culture experiment was conducted to reveal the degradation and biofilm characteristics of degradable and refractory granule microplastics in soil and soil-fertilizer systems. The results indicated that microplastics generally exhibited a weak weight loss as well as a specific etiolation on the surface after the culture, especially polyvinyl-chloride and polyhydroxyalkanoates (PHA). Increase in carbon-oxygen functional groups and the changes of oxygen/carbon ratios were noticed, which implied that oxidation and degradation occurred on the surface of microplastics during the cultural process. The changes were more intense on the degradable PHA, and the fertilized-soil treatment than those of the refractory microplastics and the pure soil. Moreover, the addition of organic fertilizers enriched the community diversity of bacterial biofilm on multiple microplastic surfaces. In this regard, the animal fertilizers provided a stronger effect than the plant fertilizers. Overall, the soil, fertilizer and microplastic types affected the community structure and diversity of bacterial biofilm. The outcomes of this study would provide a theoretical basis for the utilization of organic matters for agricultural soil applications.

Kinetics of thermal oxidative degradation of poly (vinyl chloride) containing Ca and Sn at low temperature

Calcium metal soap and polyol (dipentaerythritol) additives are replacing or partially replacing organotin in poly(vinyl chloride) (PVC) heat stabilizers due to their low cost, nontoxicity and safety. Therefore, investigating the low-temperature thermal oxidative degradation of stabilized plasticized PVC from the source is essential for recycling. This work uses isothermal thermogravimetry to investigate the thermal degradation process and isothermal discoloration of PVC/calcium metal soap/dipentaerythritol/organotin soft products with excellent heat resistance at 453-503 K and under air atmosphere. The chemical kinetics method is used to fit a single equation model of mass loss and time during the thermal oxidation degradation of PVC, and the kinetic equation obtained is: -ln(1 - α) = 3.83 × 10³exp (-6834.4/T)t. When the temperature is 453-503 K, the calculation results are basically consistent with the experimental data and are independent of the heating rate and temperature changes. In addition, the isothermal discoloration of different PVC materials was tested under air atmosphere at 468 K. The results show that when the test material is PVC/calcium metal soap/dipentaerythritol/organotin, the heat aging time to become completely blackened is longer than that of the blank sample, which indicates a strong interaction occurs between Sn, Ca and dipentaerythritol complexes and PVC molecules, inhibiting the release of hydrogen chloride. At the same time, in order to recover PVC and prevent it from carbonization, if the temperature is set to 486 K, the thermal oxidation degradation time of PVC should be less than 130 min.

Facile Synthesis of Di-Mannitol Adipate Ester-Based Zinc Metal Alkoxide as a Bi-Functional Additive for Poly(Vinyl Chloride)

A new di-mannitol adipate ester-based zinc metal alkoxide (DMAE-Zn) was synthesized as a bi-functional poly(vinyl chloride) (PVC) thermal stabilizer for the first time. The materials were characterized with Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). Characterization results confirmed the formation of Zn–O bonds in DMAE-Zn, and confirmed that DMAE-Zn had a high decomposition temperature and a low melting point. The thermal stability of DMAE-Zn on PVC also was tested by a conductivity test, a thermal aging test, and a UV-visible spectroscopy (UV-VIS) test. PVC stabilized by DMAE-Zn had a good initial color and excellent long-term stability. UV-VIS also showed that the conjugated structure in PVC stabilized by DMAE-Zn was almost all of the triene, suggesting that the addition of DMAE-Zn would suppress the formation of conjugated structures above tetraene. The dynamic processing performance of PVC samples tested by torque rheometer indicated that, having a good compatibility with PVC chains in the amorphous regions, DMAE-Zn contributed a good plasticizing effect to PVC. DMAE-Zn thus effectively demonstrates bi-functional roles, e.g., thermal stabilizers and plasticizers to PVC. Furthermore, FT-IR, a HCl absorption capacity test, and a complex ZnCl₂ test were also used to verify the thermal stability mechanism of DMAE-Zn for PVC.

PVCP-based anthropomorphic breast phantoms containing structures similar to lactiferous ducts for ultrasound imaging: A comparison with human breasts

The purpose of this work was to obtain an anthropomorphic phantom with acoustic properties similar to those of breast tissue, possessing lactiferous duct-like structures, which would be a first for this type of phantom. Breast lesions usually grow in glandular tissues or lactiferous ducts. Shape variations in these structures are detectable by using ultrasound imaging. To increase early diagnosis, it is important to develop computer-aided diagnosis (CAD) systems and improve medical training. Using tissue-like materials that mimic known internal structures can help achieve both of these goals. However, most breast ultrasound phantoms described in the literature emulate only fat tissues and lesion-like masses. In addition, commercially available phantoms claim to be realistic, but do not contain lactiferous duct structures. In this work, we collected reference images from both breasts of ten healthy female volunteers aged between 20 and 30 years using a 10 MHz linear transducer of a B-mode medical ultrasound system. Histograms of the grey scale distribution of each tissue component of interest, the grey level means, and standard deviations of the regions of interest were obtained. Phantoms were produced using polyvinyl chloride plastisol (PVCP) suspensions. The lactiferous duct-like structures were prepared using pure PVCP. Solid scatterers, such as alumina (mesh #100) and graphite powders (mesh #140) were added to the phantom matrix to mimic glandular and fat tissue, respectively. The phantom duct-like structure diameters observed on B-mode images (1.92 mm ± 0.44) were similar to real measures obtained with a micrometer (2.08 mm ± 0.23). The phantom ducts are easy to produce and are largely stable for at least one year. This phantom allows the researchers to elaborate the structure at their will and may be used in training and as a reference for development of CAD systems.

Polyvinyl chloride plastisol breast phantoms for ultrasound imaging

Ultrasonic phantoms are objects that mimic some features of biological tissues, allowing the study of their interactions with ultrasound (US). In the diagnostic-imaging field, breast phantoms are an important tool for testing performance and optimizing US systems, as well as for training medical professionals. This paper describes the design and manufacture of breast lesions by using polyvinyl chloride plastisol (PVCP) as the base material. Among the materials available for this study, PVCP was shown to be stable, durable, and easy to handle. Furthermore, it is a nontoxic, nonpolluting, and low-cost material. The breast's glandular tissue (image background) was simulated by adding graphite powder with a concentration of 1% to the base material. Mixing PVCP and graphite powder in differing concentrations allows one to simulate lesions with different echogenicity patterns (anechoic, hypoechoic, and hyperechoic). From this mixture, phantom materials were obtained with speed of sound varying from 1379.3 to 1397.9ms(-1) and an attenuation coefficient having values between 0.29 and 0.94dBcm(-1) for a frequency of 1MHz at 24°C. A single layer of carnauba wax was added to the lesion surface in order to evaluate its applicability for imaging. The images of the phantoms were acquired using commercial ultrasound equipment; a specialist rated the images, elaborating diagnoses representative of both benign and malignant lesions. The results indicated that it was possible to easily create a phantom by using low-cost materials, readily available in the market and stable at room temperature, as the basis of ultrasonic phantoms that reproduce the image characteristics of fatty breast tissue and typical lesions of the breast.