Considering that the large quantity of waste electrical and electronic equipment plastics generated annually causes increasing environmental concerns for their recycling and also for preserving of raw material resources, decreasing of energy consumption, or saving the virgin materials used, the present challenge is considered to be the recovery of individual polymers from waste electrical and electronic equipment. This study aims to provide an update of the main identification methods of waste electrical and electronic equipment such as spectroscopic fingerprinting, thermal study, and sample techniques (like identification code and burning test), and the characteristic values in the case of the different analyses of the polymers commonly used in electrical and electronic equipment. Additionally, the quality of the identification is very important, as, depending on this, new materials with suitable properties can be obtained to be used in different industrial applications. The latest research in the field demonstrated that a complete characterization of individual WEEE (Waste Electric and Electronic Equipment) components is important to obtain information on the chemical and physical properties compared to the original polymers and their compounds. The future directions are heading towards reducing the costs by recycling single polymer plastic waste fractions that can replace virgin plastic at a ratio of almost 1:1.

https://www.mdpi.com/2313-4321/4/3/32/pdf

Waste Electrical and Electronic Equipment: A Review on the Identification Methods for Polymeric Materials

Nanofiber technology in the ex vivo expansion of cord blood-derived hematopoietic stem cells

This study reports the preparation of a flexible nanofibrous probe for the rapid colorimetric detection of dopamine. To this aim, gold nanoparticles (AuNPs) were immobilized on the surface of electrospun nanofibrous membrane to obtain a new hybrid material. This hybrid structure would benefit from the properties of both nanofibers and AuNP, being (a) the porosity and high surface area of nanofibers, and (b) the unique optical properties of AuNP. The electrospun poly(ethylene terephthalate) (PET) nanofibrous membrane was alkaline treated in NaOH aqueous solution, followed by immersion in the AuNP solution. The morphology of AuNP-PET membranes was characterized using a field emission scanning electron microscopy. The AuNP-PET probes showed quick, visible color change (from red to dark blue) in the presence of dopamine at the physiological pH values. The visual detection limit was 0.5 μM. The color difference based on the formula of the L*a*b* color space was used to quantify the concentration of dopamine. The color difference increased almost linearly in the 0.5–500 µM concentration range. The presence of electrostatically adsorbed AuNP on the surface of nanofibers, along with the flexibility of the nanofibrous membrane, was responsible for fast, sensitive, and on-site detection of dopamine.

Colorimetric determination of dopamine using an electrospun nanofibrous membrane decorated with gold nanoparticles

We report herein a unique means to periodically pattern polymeric materials on individual carbon nanotubes (CNTs) using a controlled polymer crystallization method. One-dimensional (1D) CNTs were periodically decorated with polymer lamellar crystals, resulting in nano-hybrid shish-kebab (NHSK) structures. The periodicity of the polymer lamellae varies from 20 to 150 nm. The kebabs are approximately 5-10 nm thick (along CNT direction) with a lateral size of approximately 20 nm to micrometers, which can be readily controlled by varying crystallization conditions. Both polyethylene and Nylon 66 were successfully decorated on single-walled carbon nanotubes (SWNTs), multiwalled carbon nanotubes (MWNTs), as well as vapor grown carbon nanofibers (CNFs). The formation mechanism was attributed to \"size-dependent soft epitaxy\". Because NHSK formation conditions depend on CNT structures, it further provides a unique opportunity for CNT separation. The reported method opens a gateway to periodically patterning polymers and different functional groups on individual CNTs in an ordered and controlled manner, an attractive research field that is yet to be explored.

/pdf/polymer-crystallization-driven-periodical-patterning-on-2vqx9qfue0.pdf

Polymer crystallization-driven, periodical patterning on carbon nanotubes

Branched polyesters based on the polyethylene terephthalate were synthesized by incorporating isophthalic acid (IPA) and trimellitic anhydride (TMA). TMA has the branching agent role. During the esterification step, only terephthalic acid, IPA, and ethylene glycol were reacted and TMA was added at the beginning of the polycondensation step. Reaction progress was studied using water production and mixing torque increase during esterification and polycondensation steps, respectively. Polycondensation time increases with IPA and decreases with TMA. Fourier transform infrared spectroscopy spectrum shows the production of polyester. Randomness and sequence length were studied using 13CNMR. Results reveal that randomness increases with TMA. Crystallinity and morphology of samples were studied using differential scanning microscopy (DSC). DSC thermograms show that samples turn to an amorphous structure by adding IPA and TMA with decreasing glass transition temperature, Tg. X-ray diffraction spectra approve changing nature similar to DSC results. Dynamic light scattering results present that with an increase in TMA, some size-increasing particles were detected. The rheological behavior of samples was studied using RMS. By adding TMA, the elastic behavior of samples changes to viscous behaviors.

Branched polyester based on the polyethylene tere/iso phthalate and trimellitic anhydride as branching agent

Poly(ethylene terephthalate) or PET is a polymer that finds extensive application in wide-­ranging areas. The incorporation of nanofillers in PET imparts significant enhancements to its properties such as mechanical strength, permeability, electrical conductivity, and thermal stability, among others. These property improvements make PET nanocomposites interesting candidates for numerous existing and emerging applications. This chapter reviews the present state-of-the-art technology developments in the synthesis and characterization of PET nanocomposites incorporating nanofillers such as graphene, carbon nanotubes, nanoclays, and other inorganic nanoparticles. The chapter also discusses various technological challenges and their implications on future trends of PET nanocomposite technology.

N.S. Korivi

Papers

Preparation, characterization, and applications of poly(ethylene terephthalate) nanocomposites