Polylactide (PLA) is known as one of the most promising biopolymers as it is derived from renewable feedstock and can be biodegraded. During the last two decades, it moved more and more into the focus of scientific research and industrial use. It is even considered as a suitable replacement for standard petroleum-based polymers, such as polystyrene (PS), which can be found in a wide range of applications—amongst others in foams for packaging and insulation applications—but cause strong environmental issues. PLA has comparable mechanical properties to PS. However, the lack of melt strength is often referred to as a drawback for most foaming processes. One way to overcome this issue is the incorporation of chemical modifiers which can induce chain extension, branching, or cross-linking. As such, a wide variety of substances were studied in the literature. This work should give an overview of the most commonly used chemical modifiers and their effects on rheological, thermal, and foaming behavior. Therefore, this review article summarizes the research conducted on neat and chemically modified PLA foamed with the conventional foaming methods (i.e., batch foaming, foam extrusion, foam injection molding, and bead foaming).Keywords:polylactide (PLA);biofoams;chemical modification;foam extrusion;batch foaming;foam injection molding;bead foaming;rheology;crystallization;density reduction
View large Download slide View large Download slide Close modal Nanofiltration (NF) membranes have already been widely used owing to the merits of high permeability, energy saving, and selective separation. Here, a convenient way to prepare a functional layer of a composite NF membrane was investigated, which used taurine to replace a part of piperazine (PIP) in the aqueous phase in interfacial polymerization to decrease the cross-linking density of the polyamide network. Although the molecular weight cutoff by the membrane decreased to 2,000 Da, the interception to sulfates and negatively charged dyes was strengthened. As the taurine ratio increased, the surface layer thinned, and pure water permeation improved, but MgSO 4 rejection showed a tendency of ‘first-increase-then-decrease’ under the synergism of size exclusion and the Donnan effect. At the apex ratio of 4:1 (taurine: PIP), the T80 membrane showed >98% retention to sulfates, MgSO 4 , Na 2 SO 4 , and (NH 4 ) 2 SO 4 , and >98.7% rejection to anionic dyes, methyl blue, congo red, and acid chrome blue K (ABK). The film also exhibited excellent fouling resistance to emulsified oil, humic acid, and bovine serum albumin, and fractionation of ABK and NaCl. The high permeability of loose nanofiltration membranes. Taurine partially replaces piperazine. SO 3 H covered surface. Fractionation of dye and NaCl. Reduced cross-linking density.
Androgenic alopecia (AGA), also known as male pattern baldness, is one of the most common hair loss diseases worldwide. The main treatments of AGA include hair transplant surgery, oral medicines, and LDL laser irradiation, although no treatment to date can fully cure this disease. Animal models play important roles in the exploration of potential mechanisms of disease development and in assessing novel treatments. The present study describes androgen receptor (AR) in C57BL/6 mouse hair follicles that can be activated by dihydrotestosterone (DHT) and translocate to the nucleus. This led to the design of a mouse model of androgen-induced AGA in vivo and in vitro. DHT was found to induce early hair regression, hair miniaturization, hair density loss, and changes in hair morphology in male C57BL/6 mice. These effects of DHT could be partly reversed by the AR antagonist bicalutamide. DHT had similar effects in an ex vivo model of hair loss. Evaluation of histology, organ culture, and protein expression could explain the mechanism by which DHT delayed hair regrowth.
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