Studies of synergism between carbon black and stabilisers in LDPE photodegradation

Effect of Additives on Thermal Degradation and Crack Propagation Properties of Recycled Polyethylene Blends

Additives, such as antioxidants (AOs), carbon black (CB) and compatibilizers (COs), are used in recycled polymer blends for different reasons. AOs slow thermal degradation, CB gives blends a black color and protect them against ultraviolet (UV) light, and compatibilizers improve compatibility between the different phases of the mixture and consequently enhance the mechanical properties of the final blend. In this paper, the three additives were added to recycled polyethylene (PE) blends to study their effect on the final properties and to determine the best formulations that help improve the mechanical properties of recycled PE blends. Stress Crack Resistance (SCR) was accessed by performing Notched Crack Ligament Stress (NCLS) and Un-notched Crack Ligament Stress (UCLS). On the other hand, Oxidative Induction Time (OIT) was used to determine the oxidation time of the blends and the effect of each additive on this property. Based on the results of this study, it was proven that adding carbon black and antioxidants delay the thermal degradation of recycled PE blends and consequently improve the OIT. Otherwise, resistance to stress cracking is improved only by adding a compatibilizer to the reference blend.

Metal-doped carbon-supported/modified titanate nanotubes for perfluorooctane sulfonate degradation in water: Effects of preparation conditions, mechanisms, and parameter optimization

Metal-doped, activated carbon (AC) supported titanate nanotubes (Me/TNTs@AC) have been shown promising for photocatalytic degradation of per- and polyfluoroalkyl substances (PFAS). However, the preparation recipe of the adsorptive photocatalysts has not yet been optimized in terms of type and content of precursor ACs and the metal dopants as well as synthesizing conditions. In this work, the photocatalytic performance of Me/TNTs@AC was evaluated based on the effectiveness in defluorination of pre-sorbed perfluorooctane sulfonic acid (PFOS) after 4-h UV irradiation. Based on the experimental results, the highest photocatalytic mineralization efficiency (66.2 %) of PFOS was achieved using Ga/TNTs@AC prepared under the following conditions: Filtrosorb-400® = 50 wt%, Ga = 2 wt%, hydrothermal treatment temperature = 130 °C, hydrothermal duration = 72 h, and calcination temperature = 550 °C. To understand the underlying mechanisms, selected materials were characterized via X-ray diffraction, the BET surface area and pore volume, UV-vis diffuse reflectance spectrometry, and photoluminescence. The results revealed that the superior photoactivity of Ga/TNTs@AC is attributed to the Ga-facilitated formation of pure crystallized anatase phase during the calcination, high UV light absorption, formation of microscale hybrid AC-anatase-Ga phases, and oxygen defects induced by Ga³⁺. The information can facilitate preparation and optimization of composite photocatalysts for efficient adsorption and photocatalytic degradation of PFAS in water.

Visual, Non-Destructive, and Destructive Investigations of Polyethylene Pipes with Inhomogeneous Carbon Black Distribution for Assessing Degradation of Structural Integrity

Carbon black (CB) is used in polyethylene (PE) pipes to protect against thermal and photooxidation. However, when CB is not properly dispersed in the PE matrix during processing, white regions having little or no CB concentration, known as “windows,” appear within the CB/PE mixed black compound. In some cases, windows can drastically affect the structural integrity of both the pipe and butt fusion joint. In this work, PE pipes with varying amounts of windows were investigated for their characteristic window patterns, as well as quantifying the area fraction of windows (% windows). Tensile test on specimens with known % windows determined a critical limit above which the fracture strain rapidly degrades. Micro-tensile and micro-indentation results showed tear initiation at the window–black PE matrix boundary; however, they did not confirm the mechanism of tear initiation. In support of this work, a method of making thin shavings of a whole pipe cross section was developed, and the best viewing windows under cross-polarized monochromatic light were identified. In addition, a phased array ultrasonic test (PAUT) and microwave imaging (MWI) were directly applied to the pipe and confirmed the presence and patterns of the windows.

How to Build a Microplastics-Free Environment: Strategies for Microplastics Degradation and Plastics Recycling

Microplastics are an emergent yet critical issue for the environment because of high degradation resistance and bioaccumulation. Unfortunately, the current technologies to remove, recycle, or degrade microplastics are insufficient for complete elimination. In addition, the fragmentation and degradation of mismanaged plastic wastes in environment have recently been identified as a significant source of microplastics. Thus, the developments of effective microplastics removal methods, as well as, plastics recycling strategies are crucial to build a microplastics-free environment. Herein, this review comprehensively summarizes the current technologies for eliminating microplastics from the environment and highlights two key aspects to achieve this goal: 1) Catalytic degradation of microplastics into environmentally friendly organics (carbon dioxide and water); 2) catalytic recycling and upcycling plastic wastes into monomers, fuels, and valorized chemicals. The mechanisms, catalysts, feasibility, and challenges of these methods are also discussed. Novel catalytic methods such as, photocatalysis, advanced oxidation process, and biotechnology are promising and eco-friendly candidates to transform microplastics and plastic wastes into environmentally benign and valuable products. In the future, more effort is encouraged to develop eco-friendly methods for the catalytic conversion of plastics into valuable products with high efficiency, high product selectivity, and low cost under mild conditions.

Effect of organic additives on silver release from nanosilver-polyethylene composite films to acidic food simulant

The effects of organic additives (Irgafos 168, Irganox 1076, Tinuvin 622, Chimassorb 944, UV-P, and UV-531) on silver release from nanosilver-polyethylene composite films into an acidic food simulant (3% acetic acid) were investigated using inductively coupled plasma mass spectrometry. The limits of detection and quantification, coefficient of determination, and recoveries of the method used were 3.7ngL^-1, 12.4ngL^-1, 0.999, and 89-113%, respectively. The results indicated that additives can affect silver release via two simultaneous processes: (i) reactions between organic additives and silver that promote silver release from the composite film to the acidic food simulant; and (ii) the promotion or inhibition of silver release by affecting silver oxidation. High temperature and humidity treatment of the composite films was found to significantly increase silver release by promoting silver oxidation.