Low density polyethylene, expanded polystyrene and expanded polypropylene: Strain rate and size effects on mechanical properties

The amount of generated plastic waste has increased dramatically, up to 20 times, over the past 70 years. More than 50% of municipal plastic waste is composed of polystyrene (PS), polypropylene (PP), and low-density polyethylene (LDPE) products. Therefore, this work has developed a kinetic model that can fully describe the thermal decomposition of plastic mixtures, contributing significantly towards the efficiency of plastic waste management and helping to save the environment. In this work, the pyrolysis of different plastic mixtures, consisting of PP, PS, and LDPE, was performed using a thermogravimetric analyzer (TGA) at three different heating rates (5, 20, and 40 K/min). Four isoconversional models, namely Friedman, Flynn–Wall–Qzawa (FWO), Kissinger–Akahira–Sunose (KAS), and Starink, have been used to obtain the kinetic parameters of the pyrolysis of different plastic mixtures with different compositions. For the equi-mass binary mixtures of PP and PS, the average values of the activation energies were 181, 144 ± 2 kJ/mol obtained using the Freidman and integral (FWO, KAS, and Starink) models, respectively. However, higher values were obtained for the equi-mass ternary plastic mixtures of PP, PS, and LDPE (Freidman: 255 kJ/mol, FWO: 222 kJ/mol, KAS: 223 kJ/mol, and Starink: 222 kJ/mol). The most suitable reaction mechanisms were obtained using the Coats–Redfern model. The results confirm that the most controlling reaction mechanisms obey the first-order (F1) and the third-order (F3) reactions for the pyrolysis of the equi-mass binary (PS and PP) and equi-mass ternary (PS, PP, and LDPE) mixtures, respectively. Finally, the values of the pre-exponential factor (A) were obtained using the four isoconversional models and the linear relationship between ln A and the activation energy was confirmed.

Niedermolekulare ('flüchtige') Radiolyseprodukte von Kunststoffen wurden mittels Thermodesorption-Gaschromatographie-Massenspektrometrie untersucht. Nach einem qualitativen Screening von sechs medizinisch verwendeten Kunststoffen und Untersuchungen an LDPE- und Polypropylen-Folien lag der Schwerpunkt auf der quantitativen Bestimmung der Radiolyseprodukte von Polystyrol. Eine Sterilisationsdosis von ca. 25 kGy erzeugte in allen untersuchten medizinischen Kunststoffen -- Spritzgußtypen von PS, MABS, PA-6, PVC, HDPE und PP -- nachweisbare Mengen von niedermolekularen Radiolyseprodukten, die für beträchtliche Zeit in der polymeren Matrix eingeschlossen bleiben. Diese Produkte und ihre Konzentrationen sind charakteristisch für die einzelnen Kunststoffe. Die Hauptprodukte von Polystyrol (PS) sind Acetophenon, Benzaldehyd, Phenol, 1-Phenylethanol und Phenylacetaldehyd; ihre Konzentrationen liegen um etwa eine Größenordnung unter denen des Reststyrols und Styrol-Dimers. Die Produkte werden (neben aliphatischen Verbindungen) auch in MABS, einem Styrol-Copolymeren, gebildet. Das Hauptprodukt von Polyamid-6 ist Pentanamid, die wichtigsten Radiolyseprodukte von PVC und Polypropylen sind Fragmente von Additiven, d. h. von Organozinn-Stabilisatoren bzw. Phenol-Antioxidantien. In HDPE entstehen nur Spuren von Kohlenwasserstoffen, Aldehyden, Ketonen und Carbonsäuren. Im Gegensatz zu früheren Berichten werden flüchtige Produkte auch in LDPE-Folien für längere Zeit zurückgehalten und in PP-Folien wesentlich länger als erwartet. Die Folien liefern Fingerprint-Chromatogramme mit sehr charakteristischen Mustern von strahlen-induzierten Peaks; nach 25 kGy liegen die Konzentrationen der Produkte um etwa eine Größenordnung unter der der Ethylenoligomere. Neben der Identifizierung der Produkte wurden Versuche zum Einfluß der absorbierten Dosis und der Desorptionstemperatur durchgeführt. Die Frage, ob die mit der TDS analysierten Produkte genuin sind oder strahlen-induzierte Artefakte, wird diskutiert, außerdem die mögliche Existenz zyklischer Produkte, der Nachweis einer Bestrahlung nach niedrigen Dosen (1 kGy) sowie die Entstehung von Fragmenten von Antioxidantien mit atypischer Struktur. Die Quantifizierung basiert auf der Annahme, daß flüchtige Verbindungen -- unter dynamischen Bedingungen und oberhalb der Glasübergangstemperatur Tg -- vollständig aus einer polymeren Matrix desorbiert werden können. Quantitative Desorptionsbedingungen wurden für die Hauptprodukte von PS etabliert, die Kalibrierung erfolgte durch Injektion externer Standards. Nach ca. 25 kGy liegen die Konzentrationen von 1-Phenylethanol (1-Pet) und Acetophenon (Acp) bei ca. 6-8 ppm bzw. 30-40 ppm (mg/kg), ihre strahlenchemischen Ausbeuten liegen im Bereich von 2.5 bis 3.5 nmol/J (1-Pet; G 0.03) und 10 bis 15 nmol/J (Acp; G 0.13). Die Konzentrationen der anderen Hauptprodukte -- Benzaldehyd, Phenol, Phenylacetaldehyd und Benzoesäure -- sind von vergleichbarer Größenordnung; sie scheinen sich während mehrjähriger Lagerung nicht zu verändern und die Ergebnisse mit einigen 'realen' Proben (bestrahlten Petrischalen etc.) zeigen, daß es zumindest nach Sterilisationsdosen möglich ist, eine Bestrahlung von Polystyrol nachzuweisen. Zur Kontrolle des analytischen Systems wurde ein umfassendes Testprogramm entwickelt, bestehend aus Sensitivitäts-, Wiederfindungs- (Recovery) und TDS-'Performance'-Tests. Außerdem wurde eine neue Desorptionstechnik, die Desorption von Polymerlösungen mit Lösungsmittelausblendung, erfolgreich getestet; Versuche zur Identifizierung von Spuren-Radiolyseprodukten in PS ergaben einen weiteren potentiellen 'Marker' für den Bestrahlungsnachweis (1-Phenyl-1-propanon). Schließlich wurden mit einer eigens entwickelten GC-Methode zur splitlos-Injektion von Benzol-Standards die Konzentrationen von Benzol in bestrahltem PS bestimmt. Die Ergebnisse werden kurz unter analytischen und strahlenchemischen Gesichtspunkten betrachtet, und ihre Implikationen für einen Bestrahlungsnachweis und für die Sicherheit von Medikalprodukten und Verpackungsmaterialien werden diskutiert.

UV-rad effected on thermal and mechanical properties (density, Shore D hardness, melt flow index, DSC) properties were studied for polypropylene (PP) blended with low density polyethylene (LDPE) at different ratios (10% PP+90% LDPE), (25%PP+75%LDPE). Results shows decreasing of blend density with increasing of PP content and increasing of it after UV-RAD for (15 hr.), also Shore D hardness decreased at the first ratio of PP (10%) then it increased with increasing of PP contain. Also Shore D increases after UV rad for (15 hr.). Melt flow index (MFI) decreased after UV rad, also the UV rad leads to increasing of crystallinity regions of blends.

Brittleness of a polymeric material has a direct relationship with the material's performance and furthermore shares an inverse relationship with that material's flexibility. The concept of flexibility of materials has been understood but merely explained with a hand-waving manner. Thus, it has never been defined by a calculation, thereby lacking the ability to determine a definite quantitative value for this characteristic. Herein, an equation is presented and proven which makes determining the value of flexibility possible. Such an equation could be used to predict a material's flexibility prior to testing it, thus saving money and valuable time for those in research and in industry. Substantiating evidence showing the relationship between flexibility of polymers and their respective mechanical properties is presented. Further relating the known tensile properties of a given polymer to its flexibility is expanded upon by proving its relationship to the linear coefficient of thermal expansion for each polymer. Additionally, determining flexibility for polymers whose chemical structures have been compromised by respective solvents has also been investigated to predict a solvent's impact on a polymer after exposure. Polymers examined through literature include polycarbonate (PC), polystyrene (PS), teflon (PTFE), styrene acrylonitrile (SAN), acrylonitrile butadiene styrene (ABS), poly(ethersulfone) (PES), low density polyethylene (LDPE), polypropylene (PP), poly(methyl methacrylate) (PMMA), and poly(vinylidene fluoride) (PVDF). Further testing and confirmation was made using PC, PS, ABS, LDPE, PP, and PMMA.

Bayesian methods allow borrowing of historical information through prior distributions. The concept of prior effective sample size (prior ESS) facilitates quantification and communication of such prior information by equating it to a sample size. Prior information can arise from historical observations; thus, the traditional approach identifies the ESS with such a historical sample size. However, this measure is independent of newly observed data, and thus would not capture an actual "loss of information" induced by the prior in case of prior-data conflict. We build on a recent work to relate prior impact to the number of (virtual) samples from the current data model and introduce the effective current sample size (ECSS) of a prior, tailored to the application in Bayesian clinical trial designs. Special emphasis is put on robust mixture, power, and commensurate priors. We apply the approach to an adaptive design in which the number of recruited patients is adjusted depending on the effective sample size at an interim analysis. We argue that the ECSS is the appropriate measure in this case, as the aim is to save current (as opposed to historical) patients from recruitment. Furthermore, the ECSS can help overcome lack of consensus in the ESS assessment of mixture priors and can, more broadly, provide further insights into the impact of priors. An R package accompanies the paper.

Coal and plastic waste co-pyrolysis by thermal analysis–mass spectrometry

Oil yield optimization from co-pyrolysis of low-density polyethylene (LDPE), polystyrene (PS) and polyethylene terephthalate (PET) using simplex lattice mixture design

This study investigates the influence of incorporating 30 wt.% polyolefin elastomer (POE) on the physical, mechanical, and microstructural properties of 3D printed three widely used thermoplastic: acrylonitrile butadiene styrene (ABS), low density polyethylene (LDPE), and polypropylene (PP). Three ABS-POE, LDPE-POE, and PP-POE blends were prepared by melt mixing method and printed by direct granule-based material extrusion, and finally the printability, microstructure, thermal, and mechanical properties aiming for potential usage in various applications were investigated. Dynamic Mechanical Thermal Analysis (DMTA) results revealed a notable shift in the glass to rubber phase to a higher temperature range and an increase in the glass transition temperature due to the presence of POE elastomers. Mechanical properties of the 3D printed samples were meticulously examined and compared with prior research. All blend samples containing 30 wt.% POE exhibited significantly enhanced ductility, attributed to aligned polymer chain reactions. ABS-POE samples demonstrated superior mechanical properties compared to PP-POE and LDPE-POE samples, likely attributed to fewer potential failure points, as evidenced by Scanning Electron Microscope (SEM) analysis of fractured cross-sections of 3D-printed samples immersed in liquid nitrogen. Additionally, 3D-printed samples with combined infill orientations (0° and 90°) were generated and subjected to tensile strength testing. Furthermore, samples 3D-printed specimens by honeycomb filling pattern for compression tests were included in the study. Microstructure analyses identified common 3D printing defects responsible for failure modes in the printed samples.

Polypropylene/starch blends were prepared using starch of different botanical source. The influence of starch type and starch content on thermal properties and morphology of polypropylene/starch blends was studied. Corn and potato starches were used as starch source. The starch content in the blends was 7 and 15 wt-%. Characterization of PP and PP/starch blends by (DSC), (TGA), and (SEM) was carried out to obtain information on miscibility among PP and starch. The starch domains exhibited characteristic voids be due to thermal degradation.

High pressure capillary rheometry of polymeric fluids

The intercalation degree of nanoclays in polymeric foamed nanocomposites containing clays is a key parameter determining the final properties of the material, but how intercalation occurs is not fully understood. In this work, energy dispersive X-ray diffraction (ED-XRD) of synchrotron radiation was used as an in-situ technique to deepen into the intercalation process of polymer/nanoclay nanocomposites during foaming. Foamable nanocomposites were prepared by the melt blending route using low-density polyethylene (LDPE), polypropylene (PP), and polystyrene (PS) with surface treated nanoclays and azodicarbonamide (ADC) as the blowing agent. Foaming was induced by heating at atmospheric pressure. The time and temperature evolution of the interlamellar distance of the clay platelets in the expanding nanocomposites was followed. Upon foaming, interlamellar distances of the nanocomposites based on LDPE and PP increase by 18% and 16% compared to the bulk foamable nanocomposite. Therefore, the foaming process enhances the nanoclay intercalation degree in these systems. This effect is not strongly affected by the type of nanoclay used in LDPE, but by the type of polymer used. Besides, the addition of nanoclays to PP and PS has a catalytic effect on the decomposition of ADC, i.e., the decomposition temperature is reduced, and the amount of gas released increases. This effect was previously proved for LDPE.

Jute fiber (Hessian cloth) reinforced low-density polyethylene (LDPE) composites were prepared by heat press molding techniques. The mechanical properties such as tensile strength (TS), bending strength (BS), and elongation at break of the composites were studied. The enhancement of TS (33%) and BS (50%) were obtained as a result of reinforcment jute fabrics in LDPE. In order to improve the mechanical properties and adhesion between jute and LDPE, hessian cloth were each treated with 2-hydroxyl ethyl methacrylate (HEMA). The HEMA-treated jute composite showed higher tensile and bending strength compared to untreated jute composite and LDPE. Dielectric properties like dielectric constant and loss tangent (tan δ) of jute, LDPE and composites were studied. Ferro to paraelectric phase transition occurred in both treated and untreated jute composites containing more than 20% jute. Water uptake behaviors of the composite were monitored and HEMA-treated composite showed lower water absorption behavior. The adhesion nature of jute and LDPE also characterized by scanning electronic microscopy (SEM), better adhesion was observed between HEMA-treated jute and LDPE over untreated ones.

Study of microplastics with semicrystalline and amorphous structure identification by TGA and DSC.

Volatile organic compounds as fingerprints for identifying marine plastics.

Ultraviolet (UV) stability of γ-irradiated poly(tetrafluoroethylene), 2°-PTFE, powder-filled low-density polyethylene (LDPE) was studied in this work. The mechanical and thermal properties of 2°-PTFE powder-filled LDPE were discussed in our previous work (Akınay and Tinçer, 1999). It already has been shown that silane coupling agents (SCAs) result in improvements in mechanical properties. The UV stability of these samples was followed by a comparision between strain at break measured after UV irradiation and the initial strain at break, in terms of their ratio defined as residual elongation. The development of carbonyl index was also determined by infrared measurements. To get further UV stability, a hindered amine light stabilizer (HALS) was also used. Whereas addition of 2°-PTFE slightly enhanced the UV stability of LDPE, mercapto type silane (A-189) treatment appeared to increase the UV stability compared with the other types of silane treatments. HALS highly improved the UV stability of untreated and silane-treated 2°-PTFE–filled LDPE at given UV irradiation time. Although we observed some fluctuations in the experimental data of HALS and SCA treated 2°-PTFE–filled LDPE, the coaddition of HALS and SCAs showed synergetics effects in the UV stability compared with the separate additions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 877–888, 1999