Yanming Han

Synthesis and properties of polyurethane foams prepared from heavy oil modified by polyols with 4,4′-methylene-diphenylene isocyanate (MDI)

The aim of the present study was to determine whether polyurethane (PU) foams can be prepared from heavy oil derived from biomass liquefaction. Since the hydroxyl number of the heavy oil was only 212 mg KOH/g, it was modified by polyols, and a hydroxyl number of 564.5 mg KOH/g was obtained. However, secondary hydroxyls rather than primary hydroxyls were introduced. As a result, when 10 wt.% activated heavy oil was added to bio-polyols, compressive strength of foams increased by 32% over that without the addition of heavy oil. When activated heavy oil wholly replaced polyethylene glycol 400, the high content of secondary hydroxyls depressed the foam reaction and resulted in partial dissociation of the heavy oil from the network structure and weakening of the thermal stability of the PU foams. Therefore, increasing the content of primary-hydroxyls by directional modification is necessary to make the process commercially feasible.

An Efficient Method for Cellulose Nanofibrils Length Shearing via Environmentally Friendly Mixed Cellulase Pretreatment

Cellulose nanofibrils (CNFs) have potential applications in the development of innovative materials and enhancement of conventional materials properties. This paper focused on the mixed cellulase hydrolysis with major activity of exoglucanase and endoglucanase on the cellulose length shearing. By the cooperation of two-step production route, including (1) enzymatic pretreatment using cellulase from Trichoderma viride and (2) mechanical grinding twice, a shorter cellulose nanofiber was fabricated. The influence of enzymatic charge and hydrolysis time on cellulose fibers was analyzed by using scanning electron microscopy (SEM), Fourier Transform Infrared Spectrometer (FTIR), and X-ray diffractometer (XRD). SEM images revealed that the surface morphology change, effective diameter sharpening, and length shearing of cellulose fibers are as a result of cellulase hydrolysis. The XRD suggested that the cellulase acted on the amorphous regions more strongly than the crystalline domains during layer-by-layer hydrolysis. The enzymatic charge and hydrolysis time significantly affected the yields and hydrolysis products concentration. The enzymatic pretreatment assisted mechanical grinding could improve the uniformity of CNF and helped to obtain CNF with exact length according to the requirement for special applications.

Use of near-infrared spectroscopy for prediction of biomass and polypropylene in wood plastic composites

Abstract The ratio of biomass to plastic in wood plastic composites (WPCs) is very important for the development of WPCs. This paper investigates the feasibility of predicting the biomass and polypropylene (PP) contents in three WPC species (Chinese fir/PP, poplar/PP and bamboo/PP) using near-infrared (NIR) spectroscopy combined with partial least squares regression (PLS). Several spectra pretreatments were applied to improve the models. Compared to other methods, baseline correction data processing gave the optimal model. The results of external validation showed that the coefficient of determination (R2), root mean square error of prediction (RMSEP) and the ratio of the standard deviation in the validation set to the RMSEP (RPD) were 0.930, 1.944 and 3.578 for biomass and 0.930, 1.958 and 3.587 for PP, respectively. It is concluded that NIR in combination with PLS is capable of reliable quantification of biomass and PP in a diversity of PP-based WPCs.

Effect of high residual lignin on the properties of cellulose nanofibrils/films

This work focused on an eco-friendly and facile method to produce lignocellulose nanofibrils (LCNFs) by the one-step grinding of original poplar wood. An array of detailed characterizations were performed to elucidate the effect of the residual lignin (22.1, 14.1, 8.2, 2.0, 0.4 and 0.2%) on the properties of LCNFs and its films. The LCNFs were rather sensitive to ultraviolet absorption, low-viscosity and anti-degradation properties. Morphological observations suggested that lignin particles homogeneously attach to the surface of cellulose nanofibrils for higher-residual-lignin samples. The results of chemical structures analysis demonstrated an effect of residual lignin amounts on the CrI. Further, the LCNF nanofilms exhibited enhanced hydrophobicity and mechanical properties. Overall, LCNFs are a renewable material with low environmental impact, low cost and they are being manufactured at a largescale. They also offer potential for a wide range of applications, such as ultraviolet protection, anti-degradation, and valuable reinforcing composite materials.Graphical Abstract

Bio-base polyurethane building material derived from lignin

The synthesis of bio-base polymer materials from renewable wood biomass resources has attracted lots of attention. Polyurethane building materials based on lignin were prepared by lignin polyol and isocyanate. Lignin was modified by polyethylene glycol and glycerol to obtain lignin polyol, and polyurethane material based on lignin was prepared from lignin polyol and isocyanate. Gel time for polymerization, morphology, compressive strength, thermal conductivity and burning behavior of lignin based polyurethane were investigated. The results showed that the apparent activation energy for the polymerization of lignin based polyurethane was low. Compressive strength changed with lignin polyol content, and reached peak value with 30% lignin polyol content. When lignin polyol content was 30%, the thermal conductivity was 0.02517 W/m·K. The heat release rate curves presented an initial peak followed by a drop and then the heat release processed in a gentle manner, reflecting the formation of flame retardant char as a barrier. It was detected that lignin could be used to prepare polyurethane in replacement of petroleum polyols. This study will pave the way for the application of lignin in bio-base polyurethane heat insulating building material.