ABSTRACT To improve the elongation at break of poly (lactic acid) (PLA) and retain its shape memory properties, in this study, polyethylene glycol (PEG) was employed as a plasticizer and incorporated chain extenders ADR‐4370 and ADR‐4400. The effects of PEG and chain extender on the microstructure, mechanical properties, shape memory properties, thermal properties, stability, and optical properties of the ADR/PEG/PLA films were investigated. The results showed that the chain extenders improved the interfacial compatibility and further increased the elongation at break. The shape memory recovery ratio ( R r ) of the films was highest at a recovery temperature of 80°C. The composite films with higher PEG molecular weight exhibited better shape memory performance. With increasing ADR‐4370 content, R r first increased and then decreased, whereas with increasing ADR‐4400 content, R r increased continuously, and orientation‐induced crystallization was generated. PEG promoted PLA crystallization; chain extender‐induced chain extension/branching and interfacial coupling inhibited crystal growth. ADR‐4370 enhanced the thermal stability of the films at the high‐temperature stage, and ADR‐4400 improved the thermal stability at the initial stage. UV–Vis spectroscopy showed that the ADR‐4370‐modified films exhibited significantly enhanced UV shielding and markedly reduced visible‐light transparency, whereas ADR‐4400 caused relatively small changes.
ABSTRACT Stereolithography (SLA) enables rapid fabrication of polymeric microneedles with tunable geometries, but their mechanical response depends on both nominal CAD parameters and fabrication‐induced dimensional deviations. Here, we investigated how microneedle architecture, dimensional fidelity, and slenderness influence the compressive response and insertion performance of SLA‐printed polymeric microneedles. Conical and pyramidal arrays with systematic variations in basal dimension and height were characterized in terms of height, basal dimension, tip‐region dimension, and base‐to‐tip ratio. Axial compression tests showed that increasing basal dimension generally increased resistance to deformation, whereas increasing height promoted more compliant and instability‐sensitive responses. Experimental instability loads were determined from force–displacement curves and compared with Euler–Johnson‐based predictions using nominal CAD geometry, as‐printed equivalent‐section geometry, and a local critical‐section approximation based on measured tip‐region dimensions. The global as‐printed equivalent‐section model markedly overestimated the experimental instability loads, whereas the local critical‐section representation provided the closest agreement for both geometries. Optical Coherence Tomography of multilayer Parafilm M provided complementary assessment of microchannel formation under insertion‐like conditions. These findings establish a fabrication‐aware framework for mechanically evaluating SLA‐printed polymeric microneedles.
ABSTRACT Radical photopolymerization is a key technique in the production of advanced polymeric materials, including applications in 3D printing, photolithography, and regenerative medicine. Its efficiency strongly depends on the composition and concentration of the photoinitiating system. This study presents spectroscopic and kinetic investigations of radical polymerization initiated by two‐component systems comprising novel 1(3) H ‐anthra[1,2‐d]imidazol‐6,11‐dione derivatives as photosensitizers and acetic acid derivatives as electron‐donating co‐initiators, with potential application in dental materials. The objective was to evaluate how the chemical structure and concentration of the photosensitizer, as well as the type and concentration of the co‐initiator, influence polymerization efficiency. Raman spectroscopy was employed to monitor monomer conversion by analyzing changes in the intensity of characteristic CC vibrational bands, while microcalorimetry enabled determination of heat evolution during polymerization. The developed photosensitizers exhibited strong absorption in the blue‐light region emitted by dental curing lamps and demonstrated high photoinitiating efficiency, dependent on their concentration and comparable to that of commercial photoinitiator, camphorquinone. Notably, effective polymerization was achieved with a low photosensitizer content (0.03 wt%). These findings indicate that the proposed systems are promising candidates for innovative dental photopolymerizable materials.
ABSTRACT Cd(II)‐IIPs and NIPs were fabricated via surface imprinting in an aqueous system using UiO‐66‐NH 2 as carrier, 3‐mercaptopropionic acid as functional monomer, and N ‐isopropylacrylamide as temperature‐sensitive monomer. An optimized polymer (Cd(II)‐IIP 23 ) exhibited a Cd(II) uptake capacity of 1153.68 mg g −1 , reaching equilibrium within 120 min. Its high selectivity aligns with the Hard‐Soft Acid–Base theory. The temperature‐sensitive monomer imparts a “temperature switch” effect, enabling efficient adsorption at low temperatures and desorption (63.84%) upon heating. Notably, at 40°C, the material demonstrates unique “intelligent screening” selectivity for Cd(II). This work offers an innovative approach combining high capacity, selectivity, rapid kinetics, and environmental friendliness for heavy metal ion removal and recovery.
ABSTRACT Intense shear during micro‐injection molding generates viscous dissipation. In this study, a test apparatus was developed to measure the temperature rise induced by viscous dissipation. Using high‐density polyethylene (HDPE), flow experiments were conducted in microcapillary dies with diameters of 350, 500, and 1000 μm. By integrating experimental measurement with numerical simulation, a temperature field reconstruction method was proposed to obtain the actual wall temperature distribution along the flow direction. Based on the Cross‐WLF viscosity model, the evolution of melt viscosity affected by dissipation‐induced temperature rise was systematically analyzed. The results show that melt viscosity decreases along the flow path, featuring a sharp drop near the inlet followed by a gradual decline. Increasing the shear rate intensifies viscous dissipation, leading to a temperature rise and nonlinear viscosity reduction. At an inlet temperature of 240°C and a shear rate of 10,000 s −1 in the 1000 μm die, the viscosity reduction per unit length reaches 71%. A distinct scale effect is observed: as the die diameter decreases, the influence of viscous dissipation becomes more prominent. At identical conditions (220°C, 10000 s −1 ), the viscosity reduction per unit length in the 350 μm die is 133% higher than in the 1000 μm die.
