Search

Poly(ethylene terephthalate) (PET), extensively employed in bottles, film, and fiber manufacture, has generated persistent environmental contamination due to its non‐degradable nature. The resolution of this issue requires the conversion of waste PET into valuable products, often achieved through depolymerization into monomers. However, the laborious purification procedures involved in the extraction of monomers pose challenges and constraints on the complete utilization of PET. Herein, a strategy is demonstrated for the polymer‐to‐polymer upcycling of waste PET into high‐value biodegradable and programmable materials named PEXT. This process involves reversible transesterifications dependent on ester bonds, wherein commercially available X‐monomers from aliphatic diacids and diols are introduced, utilizing existing industrial equipment for complete PET utilization. PEXT features a programmable molecular structure, delivering tailored mechanical, thermal, and biodegradation performance. Notably, PEXT exhibits superior mechanical performance, with a maximal elongation at break of 3419.2 % and a toughness of 270.79 MJ m−3. These characteristics make PEXT suitable for numerous applications, including shape‐memory materials, transparent films, and fracture‐resistant stretchable components. Significantly, PEXT allows closed‐loop recycling within specific biodegradable analogs by reprograming PET or X‐monomers. This strategy not only offers cost‐effective advantages in large‐scale upcycling of waste PET into advanced materials but also demonstrates its enormous prospect in environmental conservation. [ABSTRACT FROM AUTHOR]

Low‐cost airborne particle sensors are gaining attention for monitoring human exposure to indoor particulate matter. This study aimed to establish the concentrations at which these commercially available sensors can be expected to report accurate concentrations. We exposed five types of commercial integrated devices and three types of "bare" low‐cost particle sensors to a range of concentrations generated by three different sources. We propose definitions of upper and lower bounds of functional range based on the relationship between a given sensor's output and that of a reference instrument during a laboratory experiment. Experiments show that the lower bound can range from approximately 3 to 15 μg/m3. At greater concentrations, sensor output deviates from linearity at approximately 300‐3000 μg/m3. We also conducted a simulation campaign to analyze the effect of this limitation on functional range on the accuracy of exposure readings given by these devices. We estimate that the upper bound results in minimal inaccuracy in exposure quantification, and the lower bound can result in as much as a 50% error in approximately 10% of US homes. [ABSTRACT FROM AUTHOR]

Many consumer-grade low-cost particle sensors have recently entered the market, potentially providing a means of inexpensively monitoring indoor air quality and eventually being used to control building systems. In this study, we evaluate several such products: three bare sensors (BS) and five integrated devices (ID) containing one or more of these sensors and additional features. We collocated the sensors with reference instruments in a real indoor environment for two and half months. During this time, we conducted 27 particle emission events of several different types (incense, candle, toast, spray, cooking, humidifier and open window). All ID and BS exhibited an ability to respond to different PM sources, although the magnitude of their responses varied. The ratio of the time-integrated signals and peaks of the sensor signals to the reference instruments during each event varied from close to zero to around approximately three. Similarly, correlations between one-minute low-cost sensor data and similar reference instrument data varied widely among the sensors and devices tested, with R2 values between near zero and near one observed. [ABSTRACT FROM AUTHOR]