The UV-excitable fluorescent poly(lactic acid) (PLA) fibers were spun by the traditional melt spinning process, and the effects of the fluorescent powder content (w(FP)) and draw ratio (DR) on the structure and properties of the fluorescent PLA fibers were investigated, respectively. The results showed that the emission spectra of fluorescent PLA fibers were peaked at 530 nm after UV excitation, indicating the PLA fibers would emit green light under UV light. With the increasing of w(FP), the relative fluorescence intensity of PLA fibers increased gradually, whereas more and larger protrusions were formed on the fiber surface due to the agglomeration of fluorescent powder, both the crystallinity and mechanical properties of fluorescent PLA fiber showed the decreasing trend with the increase of w(FP). With the increase of DR, the tensile strength of fluorescent PLA fibers increased gradually, whereas the relative fluorescence intensity of PLA fibers increased firstly and then decreased, and the highest fluorescence intensity was obtained when the DR was 3.6. In addition, the confocal laser scanning microscope can be used well to simulate the 3D distribution of fluorescent powder among the PLA fibers. POLYM. ENG. SCI., 56:373–379, 2016. © 2016 Society of Plastics Engineers

The flax and equivalent proportion of poly(l-lactic acid)/poly(d-lactic acid) (PLLA/PDLA) were melt compounded and injection molded to prepare flax-reinforced polylactide stereocomplex (sc-PLA) bio-composite, and the effect of alkali treatment on the structure and properties of flax as well as the flax/sc-PLA composite was investigated. SEM and FTIR results showed hemicellulose in flax was almost completely removed after alkali treatment and the treated flax (ALK-flax) bundles were more separated with a cleaner surface than untreated flax (UN-flax). DSC results showed homo-crystallites (hc, T_m = 160–170°C) and stereocomplex crystallites (sc, T_m ∼210°C) coexisted in sc-PLA and flax/sc-PLA composites. Compared with sc-PLA, the total crystallinity and sc-crystallinity of flax/sc-PLA composite increased regardless of whether the flax were treated with alkali, whereas ALK-flax/sc-PLA composite showed a little higher crystallinity than UN-flax/sc-PLA composite. TGA results confirmed ALK-flax/sc-PLA composite had a higher thermal degradation temperature than UN-flax/sc-PLA composite. The mechanical tests indicated although the mechanical properties of sc-PLA increased significantly by reinforcing with flax, the ALK-flax/sc-PLA composite showed little lower mechanical properties than UN-flax/sc-PLA composite. The alkali treatment of flax had no obvious influence on the Vicat softening temperature (VST) of flax/sc-PLA composites, a higher heat resistance with VST at ∼155°C could be obtained for flax/sc-PLA composite. POLYM. ENG. SCI., 55:2553–2558, 2015. © 2015 Society of Plastics Engineers

A new dissolving process (two-step dissolving process), that is, cellulose was first swelled to the maximum in aqueous 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) solution, and then dissolved by stirring under vacuum to remove excessive water, was developed to prepare the cellulose/[BMIM]Cl spinning dope with high quality. The results showed that the initial water contents in [BMIM]Cl have great influence on the swelling and dissolution of cellulose, and the suitable swelling range of aqueous [BMIM]Cl solution, in which cellulose can be swollen but not dissolved, was 2–5% water content. In this range, the higher water content in aqueous [BMIM]Cl solution, the more swelling time would be taken for cellulose to reach the maximal swelling ratio. Based on these results, cellulose/[BMIM]Cl spinning dopes were prepared by using two-step dissolving process. In the range of our experiments, cellulose spinning dopes prepared by the two-step dissolving process had better properties, such as fewer particles, lower apparent viscosity, and higher uniformity, compared with the direct dissolving process. By using this new dissolving process, the spinning performance of cellulose/[BMIM]Cl dopes was improved, and the mechanical properties of regenerated cellulose fibers were better than those prepared by the direct dissolving process. Therefore, it is a good way to prepare cellulose/[BMIM]Cl spinning dopes by using the new dissolving process. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers