Search

This paper presents the analytical process of porous functionally graded graphene-reinforced truncated conical shells subjected to hydrostatic pressure and axial tension. Three types of graphene platelet (GPL) dispersion and three patterns of porous distribution were considered. A modified model, in which the volume fraction of the pores is regarded as the essential parameter, was built to evaluate the material properties. The static stability equations of the shells, coupled with the effect of the combined forces, were derived. The Galerkin integrate technique was employed to obtain the critical buckling hydrostatic pressure and axial tension. After the present method was validated, the influences of pores, GPLs, and shell geometrical characteristics were investigated in the parametric studies. The results show that the critical hydrostatic pressure and axial tension can be elevated by increasing the porous coefficient, semi-vertex, and length–thickness ratio. On the contrary, the critical pressure and tension are decreased with the rise of GPL mass fraction. [ABSTRACT FROM AUTHOR]

Incorporation of flexible monomer is regarded as a valid way to the chemical modification of the highly brittle poly(cyclohexene carbonate) (PCHC), which derived from the copolymerization of CO2 and cyclohexene oxide (CHO). However, toxic metal catalyst such as cobalt dominates these terpolymerizations which against the green development philosophy. Here, a series of environmentally benign aluminum porphyrin catalysts with different steric and electronic effects for the terpolymerization of CO2, CHO, and terminal epoxides with various flexible pendant alkyl groups to adjust the properties of PCHC is reported. The resulting terpolymers display a random distribution of cyclohexene carbonate along the backbone with a regulated terminal epoxide insertion from 30% to 70%. Moreover, the mechanical properties can be well regulated in a wide range indicating the feasibility of the present approach. The present study provides a green way to chemical modification of rigid PCHC. [ABSTRACT FROM AUTHOR]

A light-colored hydroxypropyl sulfonated alkali lignin (HSAL) was synthesized based on pine alkali lignin (AL) by grafted-sulfonation and crosslinking reaction processes. The reactions were evaluated by gel-permeation chromatography (GPC), infrared (IR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. The sulfonic group content and the molecular weight ( M w) of HSAL significantly increased, while the phenolic hydroxyl groups diminished by around 80% compared to AL. The color of HSAL turned to light yellow compared to the dark brown color of AL, that is, it stained less the fiber. The dispersity, heat stability, and dye uptake of dye bath with HSAL was significantly improved compared to sodium lignosulfonate, sulfomethylated AL, and dispersants of the naphthalene series. [ABSTRACT FROM AUTHOR]

A porous amino resin melamine–formaldehyde (MF) with a high content of hydroxymethyl groups was prepared via the polycondensation of an excess of formaldehyde with melamine. Polyethylene imine (PEI) was then grafted onto the porous amino resin via a Mannich reaction between the active hydroxymethyl groups on the MF resin and the amino group on PEI to synthesize a solid amine adsorbent (MF-g-PEI). A large amount of hydroxymethyl groups were generated on the synthesized amino resin due to the excess formaldehyde used in the polycondensation reaction, which will provide abundant active sites to firmly combine with PEI and thus, enhance the stability of the MF-g-PEI adsorbent. The BET surface area and the pore volume of MF-g-PEI prepared using the optimal conditions were 460 m2 g−1 and 0.76 cm3 g−1, respectively. The CO2 adsorption capacity of MF-g-PEI, with a PEI loading of 11.35% can reach 1.32 mmol g−1 at 10 °C, while its amine utilization efficiency can reach up to 48.9%. The adsorbents also exhibited significantly improved adsorption kinetics and regeneration performance. This work provides a novel method that can achieve a promising solid amine adsorbent by directly grafting PEI onto porous material in the absence of an intermediate. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide was adopted to oxidize alkali-pretreated regenerated cotton cellulose (RCC) with carboxylic content (CC) ranging from 3.2% to 15.6% depending on the H 2 O 2 /RCC molar ratios used, at the present of copper sulfate. FT-IR, 13 C-NMR, SEM and BET were performed to characterize the oxidized RCC (ORCC) structure, respectively. The FT-IR and 13 C-NMR results confirmed that the primary hydroxyl at C6 site in glucose units of RCC was selectively oxidized to carboxyl group by H 2 O 2 . SEM revealed that the pretreated regenerated cellulose by alkali solution would disentanglement the RCC fiber and increased its interface, resulting in promoting oxidation reaction. Additional evidence of reaction interfaces increment was provided by BET (BET), which presented the surface area increased from 10.12 to 17.92 m 2 /g by alkali-pretreated process, and ORCC15.6 achieved a significant increase value for 62.45 m 2 /g. TGA and TG-IR measurement illuminated that the content combustible gases such as methanol of ORCC released decrease, while the residual carbon increased with the increase of CC. Then, pentaerythritol (PER), RCC and ORCC were used as carbon sources (5 wt%) with microencapsulated ammonium polyphosphate (MFAPP, 5 wt%) in the epoxy resin (EP, 90 wt%). UL-94 testing, LOI and Cone calorimeter test (CCT) were characterized to evaluate the flame retardency of these EP-IFRs composites. Due to the introduction of carboxyl group into RCC improved the char amount of EP-IFRs (increased by 164.7% in comparison with PER), EP/MFAPP/ORCC15.6 was classified as V-0 with LOI of 29.5%. CCT evidenced excellent reaction of the EP/IFRs to fire since PHRR, THR and TSP was decreased by 42.4%, 47.6% and 50.5% in the presence of ORCC15.6 in comparison with PER, respectively. This study proposed a green and novel method to fabricate ORCC by H 2 O 2 and demonstrated ORCC15.6 was an excellent carbon source for EP-IRFs composites. [ABSTRACT FROM AUTHOR]