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.

The interfacial property is of great importance for polymer composites materials. In this study, polylactide (PLA) and sisal fibers (SF) were melt‐blended to fabricate bio‐based composites via in situ reactive interfacial compatibilization with addition of triglycidyl isocyanurate (TGIC). The interfacial adhesion between PLA matrix and sisal fibers was improved, which was confirmed by scanning electron microscope characterization. TGIC played a hinge‐like role between fibers and matrix, which bonded the PLA molecular chain to the fiber surface. FTIR analysis after Soxhlet extraction demonstrated the bonding of PLA molecular chain to the fiber surface. At the same time, the interfacial reaction and microstructures of composites were further investigated by thermal and rheological analyses. Differential scanning calorimetry and dynamic rheological measurement indicated that the mobility of the PLA molecular chain in composites was restricted because of introduction of TGIC, which also reflecting the improved interfacial interaction between sisal fibers and PLA matrix. The tensile properties of composites were improved because of improved interfacial adhesion between sisal fibers and PLA matrix. POLYM. COMPOS., 39:E174–E187, 2018. © 2017 Society of Plastics Engineers

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–properties relationship of the composites.

In order to improve interfacial adhesion between poly(lactic acid) (PLA) and sisal fibers (SFs), bifunctional monomer bisoxazoline (BO) was introduced into melt‐blending process of fibers reinforced PLA composites via in situ reactive interfacial compatibilization. The morphology of fibers and their reinforced PLA composites, thermal, and mechanical properties of the composites were studied. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) results confirmed that PLA was successfully grafted onto the surface of fiber. BO played a hinge‐like role between PLA molecular chains and SFs. The interfacial reaction and the microstructures of the SF‐reinforced PLA composites were investigated by thermal analysis. The cold crystallization temperature of the composites increased by 6.5°C with the addition of 0.6 wt% BO and 20 wt% SF as compared with the composites without BO. Microdebonding test further confirmed that interfacial shear strength of samples with BO increased by more than 30.7% in comparison with unmodified samples. For composites with 20 wt% SF addition, tensile strength and modulus increased by 34% and 10%, respectively, with 1 wt% BO addition. Flexural strength and modulus increased by 25% and 8%, respectively, with the addition of 1.2 wt% BO. Impact strength of 1 wt% BO‐modified composites was 5.1 MPa, which is 17% higher than that of the composites without BO.

A novel type of co‐rotating nontwin screw geometry is presented in this paper. The left and right screw elements have a speed ratio of 2. In order to investigate the flow pattern and mixing mechanism in the channels of such two screws, a visualization prototype with a global transparent barrel was developed. A kind of colored sodium carboxymethyl cellulose solution was prepared and used as a tracer viscoelastic fluid. Four cameras were used to capture the instantaneous images during processing. A relationship model of the axial fill length and the fill degree of fluid was established. This is the first time that the flow patterns of a viscoelastic fluid partially filled in nontwin screw elements has been captured. An asymmetry phenomenon was found in the intermeshing region and another region far from it. It was also found that material dams experienced elongation in the single‐tip screw channel, and local pile‐ups of conveyed fluid were located at the top and bottom intermeshing regions. POLYM. ENG. SCI., 59:E24–E32, 2019. © 2018 Society of Plastics Engineers