Shuangbao Zhang

Enhancement of mechanical properties of composites made of calcium carbonate modified bamboo fibers and polypropylene

Abstract The work aimed at the improvement of the mechanical properties of bamboo fiber-polypropylene composites (BaFPPC) by treatment of the fibers with CaCO3 at various concentrations of the solution (0.05, 0.1, 0.2, and 0.3 mol l-1). CaCO3 particles were successfully deposited in situ to bamboo fibers by means of ionic reaction of Na2 CO3 and CaCl2 aqueous solution at various temperatures. Then BaFPPC were produced, and various tests on single fibers and the composites were performed. The compatibility between BaF and PP matrix was improved by the treatments. The crystallinity of inorganic materials was significantly affected by the reagent’s concentration. A 10.4% increase in tensile strength and a 16.7% increase in tensile modulus were observed after fiber treatment with CaCO3 at a concentration of 0.2 mol l-1.

Interfacial Properties of Bamboo Fiber-Reinforced High-Density Polyethylene Composites by Different Methods for Adding Nano Calcium Carbonate

The focus of this study was to observe the effect of nano calcium carbonate (CaCO3) modification methods on bamboo fiber (BF) used in BF-reinforced high-density polyethylene (HDPE) composites manufactured by extrusion molding. Two methods were used to introduce the nano CaCO3 into the BF for modification; the first was blending modification (BM) and the second was impregnation modification (IM). In order to determine the effects of the modification methods, the water absorption, surface free energy and interfacial properties of the unmodified composites were compared to those of the composites made from the two modification methods. The results revealed that the percentage increase in the weight of the composite treated by nano CaCO3 decreased and that of the IMBF/HDPE composite was the lowest over the seven months of time. The results obtained by the acid-base model according to the Lewis and Owens-Wendt- Rabel-Kaelble (OWRK) equations indicated that the surface energy of the composites was between 40 and 50 mJ/m2. When compared to the control sample, the maximum storage modulus (E′max) of the BMBF/HDPE and IMBF/HDPE composites increased 1.43- and 1.53-fold, respectively. The values of the phase-to-phase interaction parameter B and the k value of the modified composites were higher than those of the unmodified composites, while the apparent activation energy Ea and interface parameter A were lower in the modified composites. It can be concluded that nano CaCO3 had an effect on the interfacial properties of BF-reinforced HDPE composites, and the interface bonding between IMBF and HDPE was greatest among the composites.

Dipping Modification with Nano-CaCO3 to Improve Tensile Properties of Individual Bamboo Fiber for Developing Bamboo–Plastic Composite

ABSTRACT Nano-CaCO3 dipping modification was proposed to improve the tensile performance of individual bamboo fiber prepared by sulfate process. Effects of nano-CaCO3, EDTA-2Na concentration, and dipping time on the morphological and mechanical of fiber were characterized. Results show that sulfate isolated fiber surface is smooth and porous, providing potential adsorption site for nano-particle. Under nano-CaCO3 1.00 × 10–2 g/mL, EDTA-2Na 6.25 × 10–4 g/mL, and a dipping time of 25 min, both the number and the size distribution of nano-CaCO3 are relatively uniform while tensile parameters achieve maximums (i.e., tensile strength 1302.47 MPa, modulus of elasticity 61.83 GPa, and elongation at break 3.38%).

The Effect of Alkali Treatment on Properties of Dopamine Modification of Bamboo Fiber/Polylactic Acid Composites

In this study, a synergistic treatment including dopamine (DA) modification and alkali pretreatment on bamboo fiber (BF) was used as reinforcement in a polylactic acid (PLA) matrix to improve the mechanical and thermal properties of BF/PLA composites. The effects of the sodium hydroxide loading rate on the performance of mussel-inspired dopamine-modified bamboo fiber and the BF/PLA composites were evaluated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), mechanical testing (examining flexural, tensile, and impact properties), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Analysis of the composites suggested that the optimal condition was treatment with a 4 wt % solution of NaOH and a 1 wt % concentration of dopamine. Compared with the untreated bamboo fiber/polylactic acid composites, the synergistic treatment improved the thermal properties and mechanical properties; flexural, tensile, and impact strengths increased by 16.1%, 34.4%, and 3.7%, respectively. It was further verified that appropriate alkali treatment was a promising approach in promoting the effect of dopamine-modified coating while maintaining the crystal structure of the cellulose.

Mussel-Inspired Polydopamine as a Green, Efficient, and Stable Platform to Functionalize Bamboo Fiber with Amino-Terminated Alkyl for High Performance Poly(butylene succinate) Composites

A new and eco-friendly mussel-inspired surface modification pathway for bamboo fiber (BF) is presented in this study. The self-assembly polydopamine (PDA) coating can firmly adhere on BF surface, which also serves as a bridge to graft octadecylamine (ODA) for hydrophobic surface preparation. The as-formed PDA/ODA hybrid layer could supply abundant hydrophobic long-chain alkyls groups and generated a marked increase in BF surface roughness and a marked decrease in surface free energy. These changes provided advantages to improve fiber–matrix interfacial adhesion and wettability. Consequently, high performance was achieved by incorporating the hybrid modified BF into the polybutylene succinate (PBS) matrix. The resultant composite exhibited excellent mechanical properties, particularly tensile strength, which markedly increased by 77.2%. Meanwhile, considerable high water resistance with an absorption rate as low as 5.63% was also achieved. The gratifying macro-performance was primarily attributed to the excellent interfacial adhesion attained by hydrogen bonding and physical intertwining between the PDA/ODA coating on the BF and the PBS matrix, which was further determined by fracture morphology observations and dynamic mechanical analysis. Owing to the superior adhesive capacity of PDA, this mussel-inspired surface modification method may result in wide-ranging applications in polymer composites and be adapted to all natural fibers.

The Properties of Particleboard Made from Alkaline-treated Wheat Straw and Methylene Diphenyl Diisocyanate Binder

Properties were evaluated for particleboard made from polymethylene polyphenyl polyisocyanate (pMDI) binder and wheat straw treated with sodium hydroxide (NaOH) and ammonia hydroxide (NH3·H2O) solutions. The crystallinity (Xc) of wheat straw and board properties including internal bond strength (IB), thickness swelling after 24 h (24 hTS), modulus of rupture (MOR), and modulus of elasticity (MOE) were investigated. XRD indicated that the crystallinity of wheat straw was increased with the mass fraction range from 1% to 3%, and the bending properties of board were also improved. MOR and MOE were significantly (P < 0.05) improved, and a positive correlation with solution mass fraction was shown. Bending properties, especially MOE, were superior to the requirements in GB/T 4897-2015. IB of NaOH solution treated board was also significantly higher (P < 0.05), but results for IB of ammonia solution treated and 24 hTS for board treated with both solutions failed to meet the standard. Effects of the two solutions were not the same according to a t-test, and the effects of NaOH were better.