Thermal degradation of recycled polypropylene toughened with elastomers

Mechanical and Thermal Properties of Wood-Fiber-Based All-Cellulose Composites and Cellulose-Polypropylene Biocomposites

This article explores wood-fiber-based fabrics containing Lyocell yarn in the warp and Spinnova-Lyocell (60%/40%) yarn in the weft, which are used to form unidirectional all-cellulose composites (ACC) through partial dilution in a NaOH-urea solution. The aim is to investigate the role of the yarn orientation in composites, which was conducted by measuring the tensile properties in both the 0° and 90° directions. As a reference, thermoplastic biocomposites were prepared from the same fabrics, with biobased polypropylene (PP) as the matrix. We also compared the mechanical and thermal properties of the ACC and PP biocomposites. The following experiments were carried out: tensile test, TGA, DSC, DMA, water absorption test and SEM. The study found no significant difference in tensile strength regarding the Spinnova-Lyocell orientation between ACC and PP biocomposites, while the composite tensile strength was clearly higher in the warp (Lyocell) direction for both composite variants. Elongation at break doubled in ACC in the Lyocell direction compared with the other samples. Thermal analysis showed that mass reduction started at a lower temperature for ACC, but the thermal stability was higher compared with the PP biocomposites. Maximum thermal degradation temperature was measured as being 352 °C for ACC and 466 °C for neat PP, and the PP biocomposites had two peaks in the same temperature range (340-474 °C) as ACC and neat PP combined. ACCs absorbed 93% of their own dry weight in water in just one hour, whereas the PP biocomposites BC2 and BC4 absorbed only 10% and 6%, respectively. The study highlights the different properties of ACC and PP reference biocomposites that could lead to further development and research of commercial applications for ACC.

Modeling of the Kinetics of Polyoxymethylene Decomposition under Oxidative and Non-Oxidative Conditions

Research on the thermal and thermo-oxidative degradation of polyacetals allows for the development of effective methods of utilization of the waste of these polymers towards the recovery of monomers. For this purpose, in addition to qualitative analysis, it is necessary to understand the mechanisms of chemical reactions accompanying the decomposition process under the influence of temperature. Therefore, in this article, with the experimental results from the thermal analysis of the POM homopolymer of three various stages of life-POM-P-unprocessed sample; POM-R-recycled sample, and POM-O-sample waste-we took steps to determine the basic kinetic parameters using two well-known and commonly used kinetic models: Friedman and Ozawa-Flynn-Wall (OFW). Knowing the values of the course of changes in apparent activation energy as a function of partial mass loss, theoretical curves were fitted to the experimental data. The applied calculation models turned out to be consistent in terms of the nature of the curve changes and similar in terms of E_a in the entire range of mass loss. Both kinetic models showed a very similar course of the E_a curves. The samples that decompose under oxidative conditions obtained the best fit for the reaction of nth order with autocatalysis by product B model and the samples that decompose under inert conditions for the n-dimensional nucleation according to the Avrami-Erofeev model.

An approach to assess and identify polymers in the health-care waste of a Brazilian university hospital

This work presents the health-care waste (HCW) management and an approach to assess and identify polymers in a General Surgery Unit - Internment Service (GSU) of a Brazilian university hospital, to estimate the main polymers presenting in medical devices that are consumed during a year, discarded either as infecting (Group A) or as scarifying residue (Group E). Among the waste produced from the medical devices, 3.14 ton (98.79%) were composed of polymers (63.06% of plastics and 35.73% elastomers) while around 0.03 ton (1.21%) by metals. The proposed approach is composed of 4 steps: (1) Collecting data about consumed medical devices to be categorized into the residues Groups (A and E); (2) Identifying the polymeric composition with information provided by suppliers; (3) Characterizing the polymer functional groups by Fourier-Transform Infrared Spectroscopy (FTIR) and (4) Determining the polymer melting point by Differential Scanning Calorimetry (DSC). According to the results, the analyzed HCW was composed mainly of polypropylene (80.88%), high-density polyethylene (5.28%), polystyrene (4.51%), and cellulose (3.58%), from a total of 11 different polymers.

Effect of reprocessing cycles on the degradation of PP/PBAT-thermoplastic starch blends

The solid waste management problems caused by the accumulation of plastics require measures to mitigate the environmental damage, and mechanical recycling of plastics is among the possible solutions. In this context, the present study aimed to evaluate the effects of mechanical recycling on the properties of a polypropylene/poly(butylene adipate co-terephthalate)-thermoplastic starch blend (PP/PBAT-Thermoplastic starch blend) when it was subjected to seven reprocessing cycles by a single-screw extruder. The observations by infrared spectroscopy indicated that the chemical structures of the blend and the polypropylene matrix did not present significant changes with the reprocessing cycles. The X-ray diffraction analyses showed that the PP crystals were most affected when reprocessed in their pure form. The observations by thermogravimetry and differential scanning calorimetry indicated that the thermal stability of the blend was higher than that of polypropylene during the extrusion cycles. The scanning electron microscopy images indicated a weak interfacial interaction between the components of the blend, and the mechanical properties showed that the reprocessing improved the elasticity modulus and yield stress, with a consequential decrease of the impact strength.