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In this paper, the crystalline modification of isotactic polypropylene (PP) based on rare earth β‑nucleating agent (WBG) with surface modification were investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). First, the relationship between the different functional additives for WBG surface modification and nucleation-inducing capability of WBG in PP matrix, as well as the possible reason for the change of nucleation-inducing capability of surface-treated WBG with different functional additives in PP matrix were further studied. It revealed that surface treatment can significantly improve the nucleation-inducing capability of WBG, especially silane coupling agent was more beneficial to increase the nucleation-inducing capability of WBG. Compared with titanate coupling agent and stearic acid, the aliphatic chain length of silane coupling agent was suitable to effectively entangle with the surrounding large molecular chain of PP, and not enough to dilute the large molecular chain of PP near it. In addition, the alkoxysilane groups can react with the carbonyl group of PP main chain so that the interaction between WBG and PP matrix was further enhanced and affinity was greatly improved between them. Hence the nucleation-inducing capability was improved. Second, the influence of WBG with surface modification on the crystalline structure and the stratified crystalline structure of PP was also studied. The results showed that silane coupling agent in three functional additives could further improve the β-crystal induction ability of WBG for PP modification. In view of the stratified crystalline structure of PP, the surface-treated WBG with coupling agent, especially with silane and stearic acid, could weaken the effect of cooling environment and was beneficial for further promoting the β-crystal formation in skin layer but also in core layer.

Chemically deuterated cellulose fiber was expected to provide novel applications due to its spectral, biological, and kinetic isotope effect. In this research, the performance of the chemically deuterated cotton fibers, including their mechanical property, enzymatic degradation performance, effect on bacterial treatment, and fast identification (near-infrared modeling) was investigated. The breaking tenacity of the deuterated cotton fibers was slightly lower, which might be attributed to the structural damage during the chemical deuteration. The glucose yield by enzymatic hydrolysis was less than that of the protonic cotton fibers, implying the deuterated fibers are less sensitive to enzymatic degradation. Furthermore, the deuterated fibers could promote the growth of bacteria such as Escherichia. coli, which was associated with the released low-level deuterium content. At last, the near-infrared technique combined with partial least squares regression successfully achieved a fast identification of the protiated and deuterated cotton fibers, which significantly promoted the potential application of deuterated cellulose as anticounterfeiting materials (e.g., special paper)., Graphical Abstract

The high content of lignin is the major disadvantage for kenaf fiber separation. In order to remove lignin effectively as well as to improve the dispersion of kenaf fibers, a novel degumming process with steam explosion followed by Fenton treatment was applied in the present study. Fibers prepared by traditional chemical degumming process and raw kenaf samples were employed as control. The fiber microstructure, chemical composition, and physical and mechanical properties were characterized and analyzed in this paper. The results revealed that steam explosion coupled with Fenton treatment could effectively remove the gum materials from kenaf bast, which performed noticeably effectively in lignin removal. The refined dry fibers showed a clean and smooth surface. The average fineness of the refined dry fibers degummed by the novel process was measured to be higher than 70 dtex, which is much better than fibers prepared by the traditional chemical degumming process. It can be concluded that the novel degumming process of combined steam explosion and Fenton treatment is feasible and effective for kenaf degumming.

Heat transfer during cooling process influences the formation of crystal modification of polypropylene (PP) with nucleating agent (β-nucleated polypropylene). In this study, finite element method (FEM) was applied to simulate the cooling process in PP. Additionally, the skin-core crystalline structure of β-nucleated polypropylene cooled at different temperatures was studied by a wide angle of X-ray diffraction (WAXD). The non-thermal crystallization behaviour of β-nucleated polypropylene was further studied based on the results of FEM. The results indicated that, based on temperature field, FEM was capable of calculating the cooling rate in the skin and core layers of samples. When the cooling temperature increased from 20 °C to 100 °C, the cooling rate decreased from 702.64 °C/min to 79.04 °C/min, and from 119.49 °C/min to 40.00 °C/min in the skin layer and core layer, respectively. The difference of cooling rates from the skin layer to the core layer decreases with the increasing of cooling temperature. Correspondingly, the skin-core crystalline structure is proved to react to the gradient of cooling rate. The non-thermal crystallization also implies that the relative content of β-phase increases with the increasing of temperature, which may attribute to the longer residence time in the temperature range from 105 °C to 140 °C. Keywords: Polypropylene, Finite element method, Skin-core crystalline structure, Non-thermal crystallization behaviour, Cooling rate