Kinetics of the thermal and thermo-oxidative degradation of polypropylene/halloysite nanocomposites

Polypropylene pyrolysis kinetics under isothermal and non-isothermal conditions: a comparative analysis

The kinetics of polypropylene pyrolysis has been studied under isothermal and non-isothermal conditions using Arrhenius and Kissinger–Akahira–Sunose (KAS) equations. Under isothermal conditions, applying first order kinetic model, activation energy (Ea) and pre-exponential factor (A) were investigated and observed as 119.7 kJ mol−1 and 1.2 × 1010 min−1, while in case of non-isothermal kinetics using Kissinger–Akahira–Sunose method, the average Ea and A were found to be 91.23 kJ mol−1 and 2.3 × 107 min−1, respectively. A comparison among the isothermal and non-isothermal reactions was made on the basis of kinetics parameters. The results from both the methods showed trivial variation in kinetic parameters of the pyrolysis reaction which may be due to two major reasons. Firstly, the selection of the kinetic model applied and secondly the inconsistency due to various experimental conditions used which can be reduced at optimized conditions. As the disposal of plastic materials need reliable kinetics information to model their decomposition reactions, therefore, the kinetics data thus obtained from pyrolysis reaction of model polypropylene will help in the utilization of polypropylene waste as energy source on industrial scale.

Upgrading Argan Shell Wastes in Wood Plastic Composites with Biobased Polyethylene Matrix and Different Compatibilizers

The present study reports on the development of wood plastic composites (WPC) based on micronized argan shell (MAS) as a filler and high-density polyethylene obtained from sugarcane (Bio-HDPE), following the principles proposed by the circular economy in which the aim is to achieve zero waste by the introduction of residues of argan as a filler. The blends were prepared by extrusion and injection molding processes. In order to improve compatibility between the argan particles and the green polyolefin, different compatibilizers and additional filler were used, namely polyethylene grafted maleic anhydride (PE-g-MA 3 wt.-%), maleinized linseed oil (MLO 7.5 phr), halloysite nanotubes (HNTs 7.5 phr), and a combination of MLO and HNTs (3.75 phr each). The mechanical, morphological, thermal, thermomechanical, colorimetric, and wettability properties of each blend were analyzed. The results show that MAS acts as a reinforcing filler, increasing the stiffness of the Bio-HDPE, and that HNTs further increases this reinforcing effect. MLO and PE-g-MA, altogether with HNTs, improve the compatibility between MAS and Bio-HDPE, particularly due to bonds formed between oxygen-based groups present in each compound. Thermal stability was also improved provided by the addition of MAS and HNTs. All in all, reddish-like brown wood plastic composites with improved stiffness, good thermal stability, enhanced compatibility, and good wettability properties were obtained.

Pyrolysis of polypropylene over zeolite mordenite ammonium: kinetics and products distribution

The present work reveals pyrolysis kinetics of polypropylene (PP) over zeolite modernite using thermogravimetry. The activation energy (Ea) and frequency factor (A) were calculated applying Ozawa Flynn Wall, Coats-Redfern, and Tang Wanjun methods. The Ea calculated by all the methods were found in accord with each other. The pyrolysis was also performed in a salt bath in the temperature range 350°C–390°C. It was observed that a temperature of 370°C is the optimum temperature for maximum liquid fuel production. Moreover, the amount of solid residue decreases with the rise in temperature. Similarly, gas fraction also shows linear relationship with temperature. The condensable and noncondensable fractions were collected and analyzed by gas chromatography-mass spectrometry. The fuel properties of the oil produced were assessed and compared with commercial fuel. These properties agree well with fossil fuel and therefore have potential applications as fuel.

Halogen-Free Flame-Retardant Compounds. Thermal Decomposition and Flammability Behavior for Alternative Polyethylene Grades

The effect of six halogen-free flame retardant (FR) formulations was investigated on the thermal stability of two low-density polyethylenes (LDPE) and one linear low-density polyethylene (LLDPE), by means of thermogravimetric analysis (TGA) under nitrogen and air atmosphere. The relative data were combined with flammability properties and the overall performance of the FRs was correlated with the type of branching in the polyethylene grades and to their processing behavior. The thermal degradation kinetics was further determined based on the Kissinger and Coats-Redfern methods. In terms of flammability, the addition of a triazine derivative and ammonium polyphosphate at a loading of 35 wt. %. was found to be the most efficient, leading to UL 94 V0 ranking in the case of the LDPE grade produced in an autoclave reactor.

Polyethylene-Matrix Composites with Halloysite Nanotubes with Enhanced Physical/Thermal Properties

The aim of the present work is to investigate the effect of halloysite nanotubes (HNT) on the mechanical properties of low-density polyethylene composites modified by maleic anhydride-grafted PE (PE-graft-MA). Polyethylene nanocomposites were prepared using an injection molding machine, Arburg Allrounder 320 C 500–170; the HNT content was varied at 0 wt %, 2 wt %, 4 wt % and 6 wt %, and the PE-graft-MA content was varied at 5 wt %. The composites were examined for their ultimate tensile stress, strain at ultimate stress, hardness, impact strength, melt flow rate, heat deflection temperature, Vicat softening temperature, crystallinity degree and phase transition temperature. It was found that the addition of halloysite nanotubes to low-density polyethylene (LDPE) led to an increased heat deflection temperature (HDT, up to 47 °C) and ultimate tensile strength (up to 16.00 MPa) while the Vicat softening temperature, strain at ultimate stress, impact strength and hardness of examined specimens slightly decreased. Processing properties of the materials specified by the melt flow rate (MFR) deteriorated almost twice. The results have demonstrated that the nanoparticles can reinforce enhance LDPE at low filler content without any considerable loss of its ductility, but only when halloysite nanotubes are superbly distributed in the polyethylene matrix.

The Impact of Halloysite on the Thermo-Mechanical Properties of Polymer Composites

Nanotubular clay minerals, composed of aluminosilicate naturally structured in layers known as halloysite nanotubes (HNTs), have a significant reinforcing impact on polymer matrixes. HNTs have broad applications in biomedical applications, the medicine sector, implant alloys with corrosion protection and manipulated transportation of medicines. In polymer engineering, different research studies utilize HNTs that exhibit a beneficial enhancement in the properties of polymer-based nanocomposites. The dispersion of HNTs is improved as a result of pre-treating HNTs with acids. The HNTs' percentage additive up to 7% shows the highest improvement of tensile strength. The degradation of the polymer can be also significantly improved by doping a low percentage of HNTs. Both the mechanical and thermal properties of polymers were remarkably improved when mixed with HNTs. The effects of HNTs on the mechanical and thermal properties of polymers, such as ultimate strength, elastic modulus, impact strength and thermal stability, are emphasized in this study.

Influence of Flame Retardants on the Melt Dripping Behaviour of Thermoplastic Polymers

Melt flow and dripping of the pyrolysing polymer melt can be both a benefit and a detriment during a fire. In several small-scale fire tests addressing the ignition of a defined specimen with a small ignition source, well-adjusted melt flow and dripping are usually beneficial to pass the test. The presence of flame retardants often changes the melt viscosity crucially. The influence of certain flame retardants on the dripping behaviour of four commercial polymers, poly(butylene terephthalate) (PBT), polypropylene (PP), polypropylene modified with ethylene-propylene rubber (PP-EP) and polyamide 6 (PA 6), is analysed based on an experimental monitoring of the mass loss due to melt dripping, drop size and drop temperature as a function of the furnace temperature applied to a rod-shaped specimen. Investigating the thermal transition (DSC), thermal and thermo-oxidative decomposition, as well as the viscosity of the polymer and collected drops completes the investigation. Different mechanisms of the flame retardants are associated with their influence on the dripping behaviour in the UL 94 test. Reduction in decomposition temperature and changed viscosity play a major role. A flow limit in flame-retarded PBT, enhanced decomposition of flame-retarded PP and PP-EP and the promotion of dripping in PA 6 are the salient features discussed.