Influence of Extrusion Screw Speed and CNT Concentration on the Mechanical and EMI Properties of PC/ABS Based Nanocomposites.

This study investigates the effect of extrusion screw speed and carbon nanotube (CNT) concentration on the thermal, mechanical, and electromagnetic interference shielding effectiveness (EMI SE) properties of Polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) and its polymer nanocomposites (PNCs) by means of design of experiments (DoE) approach. A masterbatch method was employed to obtain the best dispersion of the CNTs throughout the polymer matrix. This study evaluates the thermo-mechanical characterisation of the polymers and PNCs at varying screw speeds to assess filler matrix bonding. The results highlight that CNT concentration has a significant effect on all mechanical properties, while screw speed only affects the Charpy impact strength and flexural properties of the samples. Compounding at 200 rpm has the best flexural and tensile strength, which is attributed to the best filler matrix bonding (highest storage modulus) of the PNCs. The best EMI SE results were obtained at 10 wt.% CNTs. This research contributes valuable insights into the effect of CNT concentration and extrusion screw speed on the mechanical, thermal and EMI SE properties of PC/ABS and its PNCs.

The Effects of Incorporating Nanoclay in NVCL-NIPAm Hydrogels on Swelling Behaviours and Mechanical Properties.

Following the formulation development from a previous study utilising N-vinylcaprolactam (NVCL) and N-isopropylacrylamide (NIPAm) as monomers, poly(ethylene glycol) dimethacrylate (PEGDMA) as a chemical crosslinker, and Irgacure 2959 as photoinitiator, nanoclay (NC) is now incorporated into the selected formulation for enhanced mechanical performance and swelling ability. In this research, two types of NC, hydrophilic bentonite nanoclay (NCB) and surface-modified nanoclay (NCSM) of several percentages, were included in the formulation. The prepared mixtures were photopolymerised, and the fabricated gels were characterised through Fourier transform infrared spectroscopy (FTIR), cloud-point measurements, ultraviolet (UV) spectroscopy, pulsatile swelling, rheological analysis, and scanning electron microscopy (SEM). Furthermore, the effect of swelling temperature, NC types, and NC concentration on the hydrogels' swelling ratio was studied through a full-factorial design of experiment (DOE). The successful photopolymerised NC-incorporated NVCL-NIPAm hydrogels retained the same lower critical solution temperature (LCST) as previously. Rheological analysis and SEM described the improved mechanical strength and polymer orientation of gels with any NCB percentage and low NCSM percentage. Finally, the temperature displayed the most significant effect on the hydrogels' swelling ability, followed by the NC types and NC concentration. Introducing NC to hydrogels could potentially make them suitable for applications that require good mechanical performance.

Synthesis and Characterisation of Hydrogels Based on Poly (N-Vinylcaprolactam) with Diethylene Glycol Diacrylate.

Poly (N-vinylcaprolactam) is a polymer that is biocompatible, water-soluble, thermally sensitive, non-toxic, and nonionic. In this study, the preparation of hydrogels based on Poly (N-vinylcaprolactam) with diethylene glycol diacrylate is presented. The N-Vinylcaprolactam-based hydrogels are synthesised by using a photopolymerisation technique using diethylene glycol diacrylate as a crosslinking agent, and Diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide as a photoinitiator. The structure of the polymers is investigated via Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy. The polymers are further characterised using differential scanning calorimetry and swelling analysis. This study is conducted to determine the characteristics of P (N-vinylcaprolactam) with diethylene glycol diacrylate, including the addition of Vinylacetate or N-Vinylpyrrolidone, and to examine the effects on the phase transition. Although various methods of free-radical polymerisation have synthesised the homopolymer, this is the first study to report the synthesis of Poly (N-vinylcaprolactam) with diethylene glycol diacrylate by using free-radical photopolymerisation, using Diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide to initiate the reaction. FTIR analysis shows that the NVCL-based copolymers are successfully polymerised through UV photopolymerisation. DSC analysis indicates that increasing the concentration of crosslinker results in a decrease in the glass transition temperature. Swelling analysis displays that the lower the concentration of crosslinker present in the hydrogel, the quicker the hydrogels reach their maximum swelling ratio.

Modulation of the Lower Critical Solution Temperature of Thermoresponsive Poly(N-vinylcaprolactam) Utilizing Hydrophilic and Hydrophobic Monomers.

Four-dimensional printing is primarily based on the concept of 3D printing technology. However, it requires additional stimulus and stimulus-responsive materials. Poly-N-vinylcaprolactam is a temperature-sensitive polymer. Unique characteristics of poly-N-vinylcaprolactam -based hydrogels offer the possibility of employing them in 4D printing. The main aim of this study is to alter the phase transition temperature of poly-N-vinylcaprolactam hydrogels. This research focuses primarily on incorporating two additional monomers with poly-N-vinylcaprolactam: Vinylacetate and N-vinylpyrrolidone. This work contributes to this growing area of research by altering (increasing and decreasing) the lower critical solution temperature of N-vinylcaprolactam through photopolymerisation. Poly-N-vinylcaprolactam exhibits a lower critical solution temperature close to the physiological temperature range of 34-37 °C. The copolymers were analysed using various characterisation techniques, such as FTIR, DSC, and UV-spectrometry. The main findings show that the inclusion of N-vinylpyrrolidone into poly-N-vinylcaprolactam increased the lower critical solution temperature above the physiological temperature. By incorporating vinylacetate, the lower critical solution temperature dropped to 21 °C, allowing for potential self-assembly of 4D-printed objects at room temperature. In this case, altering the lower critical solution temperature of the material can potentially permit the transformation of the 4D-printed object at a particular temperature.

Strategies for Developing Shape-Shifting Behaviours and Potential Applications of Poly (N-vinyl Caprolactam) Hydrogels.

Stimuli-responsive hydrogels are one type of smart hydrogel, which can expand/contract in water according to changes in the surrounding environment. However, it is difficult to develop flexible shapeshifting behaviours by using a single hydrogel material. This study exploited a new method to utilise single and bilayer structures to allow hydrogel-based materials to exhibit controllable shape-shifting behaviours. Although other studies have demonstrated similar transformation behaviours, this is the first report of such smart materials developed using photopolymerised N-vinyl caprolactam (NVCL)-based polymers. Our contribution provides a straightforward method in the fabrication of deformable structures. In the presence of water, the bending behaviours (vertex-to-vertex and edge-to-edge) were achieved in monolayer squares. By controlling the content and combination of the NVCL solutions with elastic resin, the bilayer strips were prepared. The expected reversible self-bending and self-helixing behaviours were achieved in specific types of samples. In addition, by limiting the expansion time of the bilayer, the layered flower samples exhibited predictable self-curving shape transformation behaviour in at least three cycles of testing. These structures displayed the capacity of self-transformation, and the value and functionality of the produced components are reflected in this paper.

Synthesis of NVCL-NIPAM Hydrogels Using PEGDMA as a Chemical Crosslinker for Controlled Swelling Behaviours in Potential Shapeshifting Applications.

Stimuli-responsive hydrogels have recently gained interest within shapeshifting applications due to their capabilities to expand in water and their altering swelling properties when triggered by stimuli, such as pH and heat. While conventional hydrogels lose their mechanical strength during swelling, most shapeshifting applications require materials to have mechanical strength within a satisfactory range to perform specified tasks. Thus, stronger hydrogels are needed for shapeshifting applications. Poly (N-isopropylacrylamide) (PNIPAm) and poly (N-vinyl caprolactam) (PNVCL) are the most popular thermosensitive hydrogels studied. Their close-to-physiological lower critical solution temperature (LCST) makes them superior candidates in biomedicine. In this study, copolymers made of NVCL and NIPAm and chemically crosslinked using poly (ethylene glycol) dimethacrylate (PEGDMA) were fabricated. Successful polymerisation was proven via Fourier transform infrared spectroscopy (FTIR). The effects of incorporating comonomer and crosslinker on the LCST were found minimal using cloud-point measurements, ultraviolet (UV) spectroscopy, and differential scanning calorimetry (DSC). Formulations that completed three cycles of thermo-reversing pulsatile swelling are demonstrated. Lastly, rheological analysis validated the mechanical strength of PNVCL, which was improved due to the incorporation of NIPAm and PEGDMA. This study showcases potential smart thermosensitive NVCL-based copolymers that can be applied in the biomedical shapeshifting area.

A real-time measurement of general practice workload in the Republic of Ireland: a prospective study.

BACKGROUND: Demand for GP services in the Republic of Ireland (RoI) is increasing, and the resultant escalation in workload demands is an issue of growing concern. Accordingly, the accurate measurement and description of GP workload is essential to inform future healthcare planning. AIM: To provide a real-time measurement of GP workload with respect to hours worked and of proportional time expenditure on typical workload activities. DESIGN AND SETTING: A prospective study among GPs in the RoI that took place from January 2019 to March 2019. METHOD: Participants were invited to enrol in the study by direct email invitation and via notifications posted within GP-specific monthly journals; online forums; and a social media platform. Participants used a time-management software program to self-record workload activity in real time over 6 weeks. RESULTS: In total, 123 GPs were included for final analyses with a total of 8930 hours of activity recorded. The mean duration of a two-session day (excluding break-time) was 9.9 hours (95% confidence interval [CI] = 9.7 to 10.0; interquartile range [IQR] 7.9 to 13.9). Of this time, 64% was spent on clinical consultations. In total, 25.4% of activity was recorded outside the hours of 9.00 am and 5.00 pm. An average of 12.4 face-to-face consultations were completed per session of activity. The mean duration of a 10-session week was greatest for the partner (50.8 hours; 95% CI = 49.8 to 51.9) and >55-year-old (50.8 hours; 95% CI = 49.3 to 52.2) demographics, relative to their respective colleagues. CONCLUSION: To the authors' knowledge, this is the first study to provide an objective, accurate, and granular real-time measurement of GP workload in the RoI, demonstrating the significant volume and variety of work undertaken by GPs in the RoI.