Ambient air-operated thermo-switchable adhesion of N-isopropylacrylamide-incorporated pressure sensitive adhesives.

Owing to the rise in global population and living standards, waste treatment has inevitably become a critical issue for a sustainable environment. In particular, for an effective recycling process, it is vital to disassemble different types of materials by removing adhesives used in the packaging. However, this removal process requires harsh solvents (acidic and organic) that are unfriendly to nature and may cause additional pollution. To address this issue, functional adhesive materials that can be removed without the use of harsh solvents have drawn significant attention. One promising approach is to utilize the stimuli-responsive polymers to synthesize pressure sensitive adhesives (PSAs); however, it is technically challenging to simultaneously satisfy (i) strong initial adhesion (without stimulus), (ii) stimuli-responsive sufficient reduction of adhesion, and (iii) reversibility. In this study, thermo-switchable PSAs were synthesized by copolymerizing N-isopropylacrylamide (NIPAM), which possesses thermal-responsive properties; acrylic acid, which endows adhesive properties; and 2-ethylhexyl acrylate, which has a low glass transition temperature to attain sufficient flexibility. The synthesized NIPAM-based thermo-switchable PSAs exhibited significantly high peel strength at room temperature (∼15.41 N/25 mm at 20 °C), which decreased by ∼97% upon heating (∼0.46 N/25 mm at 80 °C). Importantly, no residues remained due to the cohesive nature of NIPAM at high temperature. The reversible adhesion behaviour of the thermo-switchable PSAs was retained during repeated heating and cooling cycles. Therefore, the developed thermo-switchable PSA can enhance the reusability and recyclability of valuable materials and minimize the use of toxic chemicals for adhesive removal, contributing to a more sustainable future.

Association Between Ergonomic Burden Assessed Using 20-Item Agricultural Work-Related Ergonomic Risk Questionnaire and Shoulder, Low Back, and Leg Pain in Korean Farmers.

OBJECTIVES: This study aimed to determine the agricultural ergonomic burden in Korean farmers and to analyze its correlation with musculoskeletal pain. METHODS: In total, 1001 farmers (525 females and 476 males; mean age, 59.6±7.5years) who owned or rented a farm and belonged to an agricultural cooperative unit were recruited. Ergonomic burdens were assessed using a 20-item Agricultural Work-related Ergonomic Risk Questionnaire (20 agricultural works). The presence of musculoskeletal pain (shoulder, low back, and leg/foot), Farm Stressor Inventory, subjective stress index, and agricultural workload (low, moderate, somewhat hard, or hard) were collected using structured questionnaires. RESULTS: Factor analysis of the Agricultural Work-related Ergonomic Risk Questionnaire revealed a four-factor solution: neck and upper limb, trunk and push - pull, machine and heavy lifting, and repetitive trauma. Cronbach's alpha was greater than 0.65. For 18 of the 20 items, there was a significant association with the Farm Stressor Inventory, subjective stress index, and agricultural workload. The most frequent ergonomic burdens were squatting (51.2%), highly repetitive wrist movements (53.5%), shoulder flexion at 45-90° (51.2%), and trunk flexion or twisting at≥45° (48.8%). Ergonomic burdens were significantly different in 13 items between sexes. The musculoskeletal pain was associated with increased agricultural burdens in 10 items in male farmers and 14 items in female farmers. CONCLUSION: Increased agricultural ergonomic burdens were associated with musculoskeletal pain. Ergonomic burden showed different patterns between male and female farmers, with female farmers appearing to be more affected by ergonomic burden than male farmers.

Esophageal Motility Disorders in Patients With Esophageal Barium Residue After Videofluoroscopic Swallowing Study.

OBJECTIVE: To investigate esophageal motility disorders in patients with esophageal residual barium on chest x-rays after videofluoroscopic swallowing studies (VFSS) through high-resolution esophageal manometry (HREM). METHODS: We reviewed the records of 432 patients who underwent VFSS from September 2019 to May 2021, and 85 patients (19.7%) with large residual barium (diameter ≥1 cm) were included. As a result of HREM, motility disorders were classified as major or minor motility disorders according. Esophagogastroduodenoscopy and chest computed tomography results available were also reviewed. RESULTS: Among 85 patients with large residual barium in the esophagus, 16 patients (18.8%) underwent HREM. Abnormal esophageal motilities were identified in 68.8% patient: three patients (18.8%) had major motility disorders-achalasia (n=1), esophagogastric junction (EGJ) outflow obstruction (n=2)-and eight patients (50%) had minor motility disorders-ineffective esophageal motility (n=7), fragmented peristalsis (n=1). In those with normal esophageal motility, three patients of esophageal structure disorders (18.8%)-esophageal cancer (n=1), cardiogenic dysphagia (n=1), slight narrowing without obstruction of EGJ (n=1)-and two patients (12.5%) with chronic atrophic gastritis (n=2) were confirmed. CONCLUSION: Esophageal motility disorders were identified in 68.8% of 16 patients with large esophageal residual barium with three patients in the major and eight patients in the minor categories. Residual barium in the esophagus was not rare and can be a sign of significant esophageal motility disorders.

Size compatibility and concentration dependent supramolecular host-guest interactions at interfaces.

The quantification of supramolecular host-guest interactions is important for finely modulating supramolecular systems. Previously, most host-guest interactions quantified using force spectroscopic techniques have been reported in force units. However, accurately evaluating the adhesion energies of host-guest pairs remains challenging. Herein, using a surface forces apparatus, we directly quantify the interaction energies between cyclodextrin (CD)-modified surfaces and ditopic adamantane (DAd) molecules in water as a function of the DAd concentration and the CD cavity size. The adhesion energy of the ß-CD-DAd complex drastically increased with increasing DAd concentration and reached saturation. Moreover, the molecular adhesion energy of a single host-guest inclusion complex was evaluated to be ~9.51 kBT. This approach has potential for quantifying fundamental information toward furthering the understanding of supramolecular chemistry and its applications, such as molecular actuators, underwater adhesives, and biosensors, which require precise tuning of specific host-guest interactions.

Development of Poly(methyl methacrylate)-Based Copolymers with Improved Heat Resistance and Reduced Moisture Absorption.

Poly(methyl methacrylate) (PMMA) is widely used as a transparent material for optical applications, owing to its high light transmittance. However, it exhibits poor heat resistance and high moisture absorption, leading to distortion and deformation upon exposure to elevated temperatures and/or moisture. These structural changes decrease the transparency of PMMA, critically limiting its applicability. In this study, we synthesized poly(methyl methacrylate-co-styrene-co-acrylamide) (PMSAm) as a reference polymer and introduced one of four different comonomers [N-phenylmaleimide (PMI), N-cyclohexylmaleimide (CHMI), allyltrimethylsilane (ATMS), or 2,2,2-trifluoroethyl methacrylate (TF)] as a means to improve heat resistance and reduce moisture absorption. Four series of PMMA-based random copolymers (PMSAm-PMI, PMSAm-CHMI, PMSAm-ATMS, and PMSAm-TF) were synthesized by conventional thermal radical polymerization. All of the polymers synthesized exhibited improved heat resistance, with PMSAm-CHMI exhibiting the highest glass transition temperature (Tg = 122.54 °C) and 5% weight loss thermal decomposition temperature (T5d = 343.40 °C) as well as the lowest thermal expansion coefficient (90.3 µm m-1 °C-1). The highest hydrophobicity was exhibited by PMSAm-TF, with a water contact angle of 78.9°, indicating higher hydrophobicity compared to that of pure PMMA (69.4°). More importantly, high transparency (∼90%) was exhibited by all of the synthesized polymers. Thus, our copolymerization strategy successfully addresses the limitations, i.e., low heat resistance and high moisture absorption, of conventional PMMA-based materials.

A study on Zn recovery from other metals in the spent mixed batteries through a sequence of hydrometallurgical processes.

A study on selective separation of Zn from a leaching solution by disposal batteries including various type batteries was carried out to understand the recovery behaviour of Zn in leaching solution. Selective recovery of Zn in leaching solution including Mn, Cd, Cu ion was difficult due to its similar physicochemical behaviour. Experiment results by present leaching solution with 279 µm undersize indicated that the best condition for leaching is 1 M H2SO4, 250 rpm, 5 vol.% H2O2 and 353 K and the leaching efficient of Zn, Co and Mn is approximately 97%, respectively. The exclusive extraction behaviour of Zn by using D2EHPA is indicated that the best conditions for solvent extraction are to be 0.6 M D2EHPA diluted with kerosene, 30% saponification, 298 K, 5-min contact time and three-stage countercurrent extraction, and the O/A ratio 1, respectively. Recovery of Zn was with approximately 99.7% selectively from Mn, Co, Ni, Cd and Li. After scrubbing 5 times by pH 2 modified solution and single stripping experiment by 1.5 M H2SO4, the solution including Zn of 9.0 g/L can be produced.