Halogen-free Products Research Articles

Simultaneous Degradation, Dehalogenation, and Detoxification of Halogenated Antibiotics by Carbon Dioxide Radical Anions

Despite the extensive application of advanced oxidation processes (AOPs) in water treatment, the efficiency of AOPs in eliminating various emerging contaminants such as halogenated antibiotics is constrained by a number of factors. Halogen moieties exhibit strong resistance to oxidative radicals, affecting the dehalogenation and detoxification efficiencies. To address these limitations of AOPs, advanced reduction processes (ARPs) have been proposed. Herein, a novel nucleophilic reductant—namely, the carbon dioxide radical anion (CO2−)—is introduced for the simultaneous degradation, dehalogenation, and detoxification of florfenicol (FF), a typical halogenated antibiotic. The results demonstrate that FF is completely eliminated by CO2−, with approximately 100% of Cl− and 46% of F− released after 120 min of treatment. Simultaneous detoxification is observed, which exhibits a linear response to the release of free inorganic halogen ions (R2 = 0.97, p < 0.01). The formation of halogen-free products is the primary reason for the superior detoxification performance of this method, in comparison with conventional hydroxyl-radical-based AOPs. Products identification and density functional theory (DFT) calculations reveal the underlying dehalogenation mechanism, in which the chlorine moiety of FF is more susceptible than other moieties to nucleophilic attack by CO2−. Moreover, CO2−-based ARPs exhibit superior dehalogenation efficiencies (> 75%) in degrading a series of halogenated antibiotics, including chloramphenicol (CAP), thiamphenicol (THA), diclofenac (DLF), triclosan (TCS), and ciprofloxacin (CIP). The system shows high tolerance to the pH of the solution and the presence of natural water constituents, and demonstrates an excellent degradation performance in actual groundwater, indicating the strong application potential of CO2−-based ARPs in real life. Overall, this study elucidates the feasibility of CO2− for the simultaneous degradation, dehalogenation, and detoxification of halogenated antibiotics and provides a promising method for their regulation during water or wastewater treatment.

Further bans on brominated flame retardants in the US

On June 12, 2023, FRX Innovations, a developer and manufacturer of reportedly sustainable flame-retardant additives, announced that further bans on brominated flame retardants in the US unlocks an estimated, additional 100MM USD1 market for halogen-free products like its Nofia®.

Enhanced dehalogenation and coupled recovery of complex electronic display housing plastics by sub/supercritical CO2

Electronic display housing plastics contain a high amount of halogenated compounds such as brominated flame retardants (BFRs) and polyvinyl chloride (PVC). Compared with moderate critical conditions of conventional eco-friendly sub/supercritical carbon dioxide (Sc−CO2), a novel and sustainable procedure by using improved Sc−CO2 was developed for disposal of this type of plastic. The main merit of the process was that complex halogen-containing plastics were safely disposed and halogen-free products were recycled without using catalysts or additives. It was discovered that additive BFRs were initially extracted by Sc−CO2 technique and then it decomposed accompanied with PVC rapidly to form HBr and HCl, which could be separated by traditional bromine stripping techniques from seawater. Based on response surface methodology (RSM), the maximum debromination and dechlorination efficiencies were achieved at 99.51% and 99.12% respectively. After the treatment, halogen-free products such as solid carbon materials and organic chemical feedstocks were obtained. Mechanism study elucidated that free radicals reaction involving chain initiation, growth and termination induced the polymer decomposition to form these products. This study provides an applicable and green approach for disposal and recovery of halogen-containing plastics.

The Role of Labelling of Chemical Substances Contents in Recycling Promotion - Japanese Case

In this study, we investigate the effect of new legislative requirements on industrial product development. We use the case of Restriction of Hazardous Substances (RoHS) Directive and the development of halogen-free (HF) printed circuit board (PCB) in an attempt to answer the following questions: (1) What impacts can environmental regulations – such as RoHS Directive – have on the manufacturing industry? (2) How have the manufacturers – especially those outside the European Union (EU) –responded to the RoHS Directive? (3) How has the manufacturing of HF products progressed in the wake of the directive? In order to investigate these, we focused the issue of halogen in the thermosetting resin of PCB of mobile phone. We illustrated their time trend of HF PCB labelling method and actual Br existence among many manufacturers in each milestone of the regulations. Finally, almost manufacturer complied with RoHS Directive, but each starting time was different. The results of this research are the first example to illustrate this fact in the history of the electronic industry.

Effect of Moisture on Thermal Properties of Halogen-Free and Halogenated Printed-Circuit-Board Laminates

Moisture plays an important role in the integrity and reliability of printed circuit boards (PCBs). The presence of moisture in a PCB alters its thermal performance and thermomechanical properties, thereby affecting overall performance. Due to the shift in market trends toward halogen-free products, halogen-free PCB materials have recently gained popularity. There are many studies on the behavior of halogenated PCBs exposed to moisture, but there are less data available on the use of halogen-free flame retardants in PCBs. Therefore, it is necessary to understand the moisture behavior of halogen-free PCB materials and the effect of moisture on material thermal properties when compared with halogenated PCBs materials. In the past, the Center for Advanced Life Cycle Engineering has conducted thermal-property measurements on halogen-free PCB materials. Measurements were conducted per industry-adopted test methods, including preconditioning of test samples. Some measurement results did not match manufacturers' datasheets. This paper examines the dependence of out-of-plane coefficient of thermal expansion, glass-transition temperature, time to delamination, and decomposition temperature on the moisture content in halogenated and halogen-free PCB materials. Four types of PCB materials from two manufacturers, including two halogen-free and two halogenated, were tested in this paper. Furthermore, this paper investigates the suitability of IPC-TM-650 preconditioning steps for thermal-property measurements.

Eco-friendly hydrodehalogenation of electron-rich aryl chlorides and fluorides by photochemical reaction

Aryl chlorides and fluorides are smoothly hydrodehalogenated by irradiation either in neat i-PrOH or in a polar solution in the presence of hypophosphorous acid or triethylsilane. The procedure gives the halogen-free products in good to excellent yields under mild eco-friendly conditions and avoids the recourse to toxic metal catalysts.

Flame Retardant Polyethylene with Intumescent System Containing Macromolecule-Encapsulated Low Molecular Weight Charring Agent

Intumescent flame retardants are important halogen-free products used in polyethylene. However, their thermal stability and water-resistance are major shortcomings. In this work, a composite charring agent, pentaerythritol (PER) encapsulated by thermoplastic polyurethane (TPU) was used in an intumescent system to improve the flame retardancy of high density polyethylene (HDPE). The encapsulation of macromolecular charring agent TPU can effectively suppress the esterification reaction of PER and acid source in the intumescent system during processing. It can also remarkably decrease the water absorption, thus producing flame retardant HDPE with high performance. The synergistic effects of other common flame retardants including melamine phosphate, melamine polyphosphate and ammonium polyphosphate with TPU-encapsulated PER, as well as the ratio of charring agent to acid source were investigated so as to determine the optimum formula for use in HDPE. The flame retardant HDPE can reach limiting oxygen index of 33 and achieve UL-94 V-0 rating at 3.2 mm thickness when the ratio of MP/composite charring agent is 2:1 w/w.

A Review of Recent Progress in Phosphorus-based Flame Retardants

Recent patent and technical works indicate a growing interest in halogen-free solutions with the predominance of the literature focusing on phosphorus-based flame retardants. Patents published on the flame retardancy of polycarbonate and its blends significantly exceed the number of patents on flame retardancy of any other polymer. Bridged aromatic diphenyl phosphates, especially resorcinol bis(diphenyl phosphate) and bisphenol A bis(diphenyl phosphate) have found broad application because of their good thermal stability, high efficiency, and low volatility. Another actively reported group of compounds are the metal salts of dialkylphosphonic acid as well as calcium hypophosphite, which have recently been found to be particularly effective in poly(butylene terephthalate) and polycarbonate. These products are synergistic with a number of phosphorus and nitrogen-containing compounds, such as melamine salts, which seem to be very efficient and commercially useful in nylons. Printed wiring boards comprise the largest market for flame-retardant polymeric materials. Recently, there has been a strong interest in halogen free solutions in East Asia and Europe. A recent halogen-free introduction is the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, which can be reacted into epoxies. Another reactive product with some processing and property advantages is poly(m-phenylene methylphosphonate). Because of the banning of pentabromodiphenyl ether in Europe and voluntary withdrawal of this product from the market in the US, the polyurethane (PU) industry is searching for a more environmentally acceptable low-scorch alternative. Both halogenated and halogen-free solutions are being considered but the PU industry seems to have a preference for the halogen-free products, generally containing phosphorus.