Currently, most commercial polyols used in the production of polyurethane (PU) foam are derived from petrochemicals. To address concerns relating to environmental pollution, a sustainable resource, namely, castor oil (CO), was used in this study. To improve the production efficiency, sustainability, and compressive strength of PU foam, which is widely used as an impact-absorbing material for protective equipment, PU foam was synthesized with CO-based multifunctional polyols. CO-based polyols with high functionalities were synthesized via a facile thiol-ene click reaction method and their chemical structures were analyzed. Subsequently, a series of polyol blends of castor oil and two kinds of castor oil-based polyols with different hydroxyl values was prepared and the viscosity of the blends was analyzed. Polyurethane foams were fabricated from the polyol blends via a free-rising method. The effects of the composition of the polyol blends on the structural, morphological, mechanical, and thermal properties of the polyurethane foams were investigated. The results demonstrated that the fabrication of polyurethane foams from multifunctional polyol blends is an effective way to improve their compressive properties. We expect these findings to widen the range of applications of bio-based polyurethane foams.
In this study, the thermal percolation behavior for the thermal conductivity of nanocomposites according to the lateral size of graphene nanoplatelets (GNPs) was studied. When the amount of GNPs reached the critical concentration, a rapid increase in thermal conductivity and thermal percolation behavior of the nanocomposites were induced by the GNP network. Interestingly, as the size of GNPs increased, higher thermal conductivity and a lower percolation threshold were observed. The in-plane thermal conductivity of the nanocomposite containing 30 wt.% M25 GNP (the largest size) was 8.094 W/m·K, and it was improved by 1518.8% compared to the polymer matrix. These experimentally obtained thermal conductivity results for below and above the critical content were theoretically explained by applying Nan’s model and the percolation model, respectively, in relation to the GNP size. The thermal percolation behavior according to the GNP size identified in this study can provide insight into the design of nanocomposite materials with excellent heat dissipation properties.
Waste recycling is a necessary step for environmental conservation. To this end, polyester can be easily collected and recycled into end products. To promote the use of recycled polyester, it is important to expand its range of applications. We earlier reported the fabrication of recycled polyester thermal-bonded nonwovens. In this study, recycled nonwoven fabrics were dyed with Terminalia chebula dye without the use of additional mordants. To optimize the dyeing conditions, the dyeing time, dyeing temperature, and liquor concentration were varied, and the color strength, color changes, fastness properties, thermal stability, and morphology were evaluated. Further, the antibacterial activity of the dyed nonwoven was also estimated. T. chebula dyed the colored recycled rapid melting PET fiber (R-RM) nonwoven brown via the dyeing process, and the dyeablity was improved by increasing the dyeing temperature, time, and liquor concentration. The rubbing and sweat fastness properties were found to be excellent. T. chebula dye imparted efficient antibacterial properties to the R-RM nonwovens against Staphylococcus aureus and Klebsiella pneumonia. The results obtained in this study are expected to broaden the range of natural dyed recycled polyester fabric applications.
Despite the positive outlook of various organizations on the prevalence of eco-friendly cars, Korea’s electric vehicle market is small, and growth is slow. To identify factors that hinder consumer awareness and the spread of eco-friendly vehicles, news articles and online postings on eco-friendly vehicles from 1 January 2006 to 31 December 2020 were collected and analyzed using text mining techniques. This study found that Korean consumers thought hybrid vehicles were fuel-efficient and quiet; however, there were concerns about battery life and safety due to poor battery performance and complaints about battery replacement. Nevertheless, consumers thought electric cars were sophisticated, luxurious, youthful, clean, and that technical problems would be resolved in the future. The inconveniences of charging and short-distance driving, the expenses and the lack of various dispute settlement measures have been shown to lower the intention to purchase electric vehicles.
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