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The influence rule of the content ratio of cellulose, hemicellulose, and lignin on the tensile strength of sisal fibers (SFs) and the interfacial strength of SFs and poly lactic acid (PLA) ...

Untreated sisal and coir fibers (USF and UCF), alkali-treated sisal and coir fibers (ASF and ACF), and alkali-treated sisal/coir hybrid fibers (ASF/ACF) reinforced polylactide (PLA) composites were prepared by compression molding technique. The materials were characterized in terms of tensile, flexural, and impact properties. While all mechanical tests showed that the composites reinforced by alkali-treated fibers could withstand more fracture strain than untreated fibers reinforced composites which could be attributed to the improved interfacial adhesion between alkali-treated fibers and matrix related to the remove of lignin, hemicellulose and pectin by the alkali treatment, the addition of ACF in PLA/ASF composites improved the impact strength of PLA/ASF/ACF composites and showed a positive effect. More fibers tended to be torn apart or fractured, but less pulled out with the increase of coir fiber content. Compared to other composites, the ASF/ACF-reinforced PLA composites offered superior mechanical properties when the ratio of sisal to coir was 7:3. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

The in situ reactive interfacial compatibilization and properties of polylactide/sisal fiber biocomposites made via melt blending with an epoxy-functionalized terpolymer elastomer, ethylene/methyl acrylate/glycidyl methacrylate (EGMA), were investigated. Scanning electron microscopy results showed that the introduction of EGMA improved the interfacial adhesion between the sisal fibers (SF) and matrix, which was ascribed to the improved interfacial compatibilization between the polylactide and fibers via in situ reaction with EGMA during the melt-blending processing. It was also observed that the EGMA tends to weld on the surface of the fibers, which is called a self-weld fiber structure. The interfacial reaction and microstructure of the composites were further investigated by FTIR characterization, and thermal and rheological analyses. The results demonstrated that the mobility of the polylactide molecular chain was restricted due to the enhanced interfacial interaction of the composites. The addition of EGMA improved the toughness of the polylactide/sisal fiber composites without much decline in the tensile strength. Polylactide/sisal fiber composites with a good stiffness-toughness balance were obtained.

With the addition of poly (butylene-adipate-terephthalate) (PBAT) and a commercial grade epoxy-functionalized oligomer Joncryl ADR@-4368 (ADR), a blend of polylactic acid (PLA) and sisal fibers (SF) were melt-prepared via in-situ reactive process to improve the toughness and interfacial bonding of polylactide/sisal fiber composites. Fourier Transform infrared spectroscopy (FTIR) analysis demonstrated chemical bonding between sisal fibers and matrix, and scanning electron microscope characterization indicated the enhancement of interfacial adhesion between PLA matrix and sisal fibers. The micro-debonding test proved that the interfacial adhesion between PLA and SF was improved because of ADR. The presence of ADR behaved like a hinge among sisal fibers and matrix via an in-situ interfacial reaction, and compatibility between PLA and PBAT was also augmented. The introduction of PBAT exerted a plasticization effect on composites. Therefore, the toughness of PLA/SF composites was significantly elevated, while the tensile strength of composites could be well preserved. The paper focused on the demonstration of interfacial interaction and structure&ndash, properties relationship of the composites.

A simple approach to decorate multi-walled carbon nanotube (MWCNT)&ndash, reduced graphene oxide (RGO) hybrid nanoparticles with zinc oxide (ZnO) nanorods is developed to improve the electrical and mechanical properties of poly(vinyl chloride) (PVC)/MWCNT&ndash, RGO composites. The ZnO nanorods act as &ldquo, joint&rdquo, in three-dimensional (3D) MWCNT&ndash, RGO networks and the hybrid particles strongly interact with PVC chains via p-&pi, stacking, hydrogen bonds, and electrostatic interactions, which we confirmed by scanning electron microscopy (SEM) and Raman analysis. By introducing the ZnO nanorods, the RGO&ndash, ZnO&ndash, MWCNT hybrid particles increased 160% in capacitance compared with MWCNT&ndash, RGO hybrids. Moreover, the addition of RGO&ndash, MWCNT to PVC resulted in the mechanical properties of PVC being enhanced by 30.8% for tensile strength and 60.9% for Young&rsquo, s modulus at the loadings of 2.0 weight percent (wt.%) and 1.0 wt.%, respectively. Meanwhile, the electrical conductivity of PVC increased by 11 orders of magnitude, from 1 &times, 10&minus, 15 S/m to 1 &times, 4 S/m for MWCNT&ndash, RGO loading at 5.0 wt.%.

To improve the interfacial bonding of sisal fiber reinforced polylactide biocomposites, polylactide (PLA) and sisal fibers (SF) were melt-blended to fabricate bio-based composites via in situ reactive interfacial compatibilization with the addition of an epoxy-functionalized oligomer (ADR). The FTIR analysis and SEM characterization demonstrated that PLA molecular chain was bonded to the fiber surface and epoxy-functionalized oligomer played a hinge-like role between sisal fibers and PLA matrix, which resulted in improved interfacial adhesion between fibers and PLA matrix. The interfacial reaction and microstructures of composites were further investigated by thermal and rheological analyses, which indicated that the mobility of the PLA molecular chain in composites was restricted because of the introduction of ADR oligomer, which in turn reflected the improved interfacial interaction between SF and PLA matrix. These conclusions were further investigated by the calculated activation energies of glass transition relaxation (△Ea) of composites via dynamic mechanical analysis. The mechanical properties of PLA/SF composites were simultaneously reinforced and toughened via addition of ADR oligomer. The interfacial interaction and structure-properties relationship of composites are key points of this study.

The acetate-based ionic liquid (AcIL) [EMIM][Ac] does not fully dissociated into isolated ions in extremely diluted water solution (0.5 mol% of IL). Still, ion pairs exist via the through-space weak van der Waals force between H6 of the cation and Hb of the anion. In this ion pairs, except for H6 and Hb, all other hydrogen atoms (i.e., H2, H4, H5, H7, H8) are totally hydrated by water; the acetate anion suffers from a more extent of hydration due to its higher hydrophilicity. One dimension (1D) nuclear magnetic resonance (NMR) ( 1 H, 13 C, 15 N,) and two dimensions (2D) NMR are used in this study. 2D NMR used includes through-space 1 H– 1 H NOSEY (nuclear Overhauser effect spectroscopy), through-bond 1 H– 13 C HSQC COSY (heteronuclear single-quantum correlation spectroscopy), and HMBC COSY (heteronuclear multiple-bond correlation spectroscopy). The much stronger (H245/anion) or weaker (H78/anion) hydrogen-bonding interaction in the pure [EMIM][Ac] disfavors the association of ions in the diluted state due to a better hydrogen-bonding donor or a weaker hydrogen-bonding strength, respectively. However, H6/anion with the moderate hydrogen-bonding strength and the moderate hydrogen-bonding donating ability existed in the pure [EMIM][Ac] plays the role in determining the associating ion pairs. The proportion of hydrogen-bonding interaction between hydrogens in the cation with anion (100%) is approximately quantified in descending order as follows: H2 (42%), H4 (24%), H5 (22%), H6 (6%), H7 (5%), and H8 (1%).

To improve the interfacial bonding of sisal fiber-reinforced polylactide biocomposites, polylactide (PLA) and sisal fibers (SF) were melt-blended to fabricate bio-based composites via in situ reactive interfacial compatibilization with addition of a commercial grade epoxy-functionalized oligomer Joncryl ADR@-4368 (ADR). The FTIR (Fourier Transform infrared spectroscopy) analysis and SEM (scanning electron microscope) characterization demonstrated that the PLA molecular chain was bonded to the fiber surface and the epoxy-functionalized oligomer played a hinge-like role between the sisal fibers and the PLA matrix, which resulted in improved interfacial adhesion between the fibers and the PLA matrix. The interfacial reaction and microstructures of composites were further investigated by thermal and rheological analyses, which indicated that the mobility of the PLA molecular chain in composites was restricted because of the introduction of the ADR oligomer, which in turn reflected the improved interfacial interaction between SF and the PLA matrix. These results were further justified with the calculation of activation energies of glass transition relaxation (∆Ea) by dynamic mechanical analysis. The mechanical properties of PLA/SF composites were simultaneously reinforced and toughened with the addition of ADR oligomer. The interfacial interaction and structure–properties relationship of the composites are the key points of this study.

In this study, regenerated cellulose was prepared from ionic liquid 1-butyl-3-methylimidazolium acetate ([Bmim]Ac) solution using anti-solvent compressed CO 2 of different pressures. And other anti-solvents like water, ethanol and acetonitrile were also employed to regenerate cellulose to provide comparisons. The two-dimensional nuclear magnetic resonance (2D NMR), namely heteronuclear single quantum coherence (HSQC) and heteronuclear multiple bond coherence (HMBC), and attenuated total reflectance Fourier transform infrared spectroscopy (ATR–FTIR) indicated that carboxylate zwitterions [Bmim + -COO − ] formed through the chemical reactions between CO 2 and [Bmim]Ac. Besides, FTIR, wide-angle X-ray diffraction (XRD), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to provided structure characterization of native and regenerated cellulose using different anti-solvents. The results show that the crystallinity of cellulose decreases during the dissolution and regeneration process. And a crystal transformation of cellulose I to cellulose II was verified. The stability of the regenerated cellulose is lower than that of native cellulose. A higher compressed CO 2 pressure results in a smoother surface, a thicker shape and a more homogeneous texture of regenerated cellulose.