ACS polymers Au最新文献

Thermoplastic polymer materials include both plastics and elastomers. Elastomers stand out as a crucial class of materials because of their wide-ranging applications. Polymers that can depolymerize back to their original monomers present a hopeful avenue to tackle the problems associated with polymer sustainability. In recent years, a great deal of research has been centered on the chemical recycling of monomers of polymers, and there are numerous reviews on this topic. Nevertheless, these reviews typically classify materials according to polymerization methods or polymer types, seldom taking into account the functional classification of the products. This method of categorization creates difficulties for those interested in material application scenarios, as they find it hard to obtain relevant information. Hence, this perspective takes a function-oriented approach, offering solutions for recyclable thermoplastic elastomers (TPEs) by classifying them into polyurethanes, copolyesters, and polyolefins with specific sequence control (e.g., homo, random, alternating, triblock, pseudotriblock, and multiblock). We offer an overview of the synthesis methods of various polymers and the properties of the constructed TPEs, making comparisons with those of conventional TPEs. Special attention is given to the depolymerization process, including the necessary conditions and recovery efficiency of the constituent monomers. Finally, we put forward future directions for the chemical recycling of TPEs, highlighting the critical issue of "monomer reuse and performance degradation over successive recycling cycles" that has been overlooked. This perspective seeks to promote more in-depth, cross-disciplinary research involving both academic and industrial partners to develop next-generation TPEs with improved sustainability.

Polyvinylidene fluoride (PVDF) electrospun nanofiber membranes (ENMs) could potentially be used in membrane contactors (MCs) for environmental applications, such as the removal of dissolved CH₄ from anaerobic effluents. In this work, a PVDF flat-sheet ENM fabrication protocol, including the electrospinning processing and the subsequent hot-pressing treatment (HP), has been developed to produce hydrophobic membranes with suitable integrity and pore size distribution for gas–liquid separations in MCs. The HP study explored the effects of pressure (1, 10, and 20 MPa), temperature (25, 60, 80, and 120 °C), and time (2, 4, 6, and 10 min) on the morphological properties and hydrophobicity of the membranes. Our research revealed that fibers in the PVDF ENMs began to sinter at temperatures above 60 °C when hot-pressed between 1 and 20 MPa. ENM samples were prepared at different dope compositions (10–15% PVDF, 0.00–0.043% LiCl). After HP (≥1 MPa, ≥60 °C, and 6 min), the membrane thickness and water contact angle (WCA) decreased considerably, and lower pore sizes with narrower distributions were obtained. At higher pressure (10 MPa), a noticeable decrease in thickness (from 270 to 38 μm) and WCA (from 139 to 110°) was observed. Additionally, pore size distribution shifted toward a predominant narrow peak of around 0.40 μm. HP enhanced the uniformity of the PVDF crystalline structure without altering its overall crystallinity degree (40–42%). The HP ENM exhibited a comparable dissolved CH₄ recovery performance to a commercial PVDF membrane and demonstrated sufficient mechanical integrity to endure operating conditions, maintaining a stable performance for at least 80 h.

Cyanate esters are key thermosetting resins for composite materials that require structural integrity and resistance to elevated temperatures. Because cyanate ester composites require relatively high processing temperatures, they are susceptible to the formation of process-induced residual stresses, which compromise their overall strength and durability. Process modeling is a key strategy for optimizing processing parameters to minimize such residual stresses. A necessary component of effective and efficient process modeling of composites is computationally established resin property evolution relationships for a range of processing parameters. In this study, the physical, mechanical, and thermal properties of a cyanate ester resin are established as a function of processing time and temperature using experimentally validated molecular dynamics modeling. The results show that the properties are strongly dependent on the processing temperature. At processing temperatures above 160 °C, the properties quickly approach their fully cured values, whereas at processing temperatures below 140 °C, the chemical cross-linking is significantly inhibited, and processing times to complete cure are relatively long. The evolution of the physical, mechanical, and thermal properties as a function of processing time is established, which is critical data needed as input into multiscale process modeling and optimization of cyanate ester composites for computationally driven composite design.