Jinping Qu

Preparation, characterization and properties of PLA/TiO2 nanocomposites based on a novel vane extruder

Polylactide/TiO2 nanocomposites with different contents of nanoscale TiO2 were prepared by melt blending with a vane extruder in this work. SEM and TEM microphotographs indicate that the nanoparticles were well dispersed in the polymer matrix under the elongational flow field of the vane extruder. Crystallization and melting behavior were examined with DSC. The results show that TiO2 nanoparticles have an inhibition for the cold crystallization process of PLA to some extent and the cold crystallization temperature of nanocomposites shifted to a maximum value at about 106 °C with low TiO2 loadings (0.5 wt% or 1 wt%). Dynamic rheological measurements and TGA results show that the introduction of TiO2 has significantly improved the thermal stability. The toughness, surface wettability and UV resistance of the composites were also investigated in detail.

Characteristics Study of Polymer Melt Conveying Capacity in Vane Plasticization Extruder

A vane extruder is novel equipment for polymer processing. The materials were conveyed and plasticized by a group of vane plasticization units and the materials suffered normal stress during processing. An analytic model was developed to analyze the conveying capacity of melt in the vane plasticization unit of which the melt can be conveyed positively. The analysis of conveying capacity of melt in the vane plasticization unit shows that the conveying capacity increased with the rotate speed, eccentricity distance, vane width, inner-diameter of stator. And the leakage flow model was developed to show that the leakage flow is increased with the width of leakage gaps but decreased with the apparent viscosity of melt. The experiment results show a linear variation of production with rotating speed, and small dependence effect of production with die pressure variation.

Novel dynamic elongational flow procedure for reinforcing strong, tough, thermally stable polypropylene/thermoplastic polyurethane blends.

Thermoplastic polyurethane (TPU)/polypropylene (PP) blends of different weight ratios were prepared with a self-made vane extruder (VE), which generates global dynamic elongational flow, and a traditional twin-screw extruder (TSE), which generates shear flow. High-resolution scanning electron microscopy and polarizing microscopy showed a structure feature of fiber morphology and a clear interlocking structure of spherulites of PP/TPU blends prepared with a VE. The wide-angle X-ray diffraction results showed that the TPU/PP blend based on dynamic elongational flow had evident crystalline structure of the β form as a function of PP (90 wt %), compared to that of the conventional shear flow processing techniques. A significant improvement of the mechanical properties was obtained; the samples prepared with a VE had superior mechanical properties compared to those of the samples prepared with a TSE. Interestingly, differential scanning calorimetry curves showed that dynamic elongational flow could successfully improve the crystallinity of the PP/TPU blends. Furthermore, dynamic thermomechanical and thermogravimetric analysis curves revealed the apparent partial miscibility and strong interaction of the PP/TPU blends influenced by dynamic elongational flow, compared to that of TSE-extruded. Further research will provide significant understanding of the spherulite interface and high-performance manipulation of PP/TPU blends under dynamic elongational flow, achieving superior PP/TPU blends.

Properties of heat-treated sisal fiber/polylactide composites

Sisal fibers (SFs) were pretreated by heat treatment (HT). The SFs were mixed with a biodegradable material, polylactide (PLA), and the composites were prepared by hot press molding. The effects of the HT temperature and time on the mechanical properties of the composites were investigated, and the HT mechanism was studied by scanning electron microscopy and infrared, x-ray photoelectron, and nuclear magnetic resonance spectroscopies. The results show that an appropriate HT can remove strongly hydrophilic materials such as hemicelluloses from the fibers, and thus decrease their hydrophilicity, thereby improving the retting between the fibers and the matrix. This improves fiber–matrix interfacial adhesion, which can improve the mechanical properties of the composites. The HT also influences the fiber strength to some extent and affects the mechanical properties of composites.

Mechanical Properties of Poly(Butylene Succinate) Reinforced with Continuously Steam-Exploded Cotton Stalk Bast

Poly(butylene succinate) (PBS) was reinforced by cotton stalk bast fibers (CSBF), which had been pretreated by the continuous steam explosion method. The influence of water content in CSBF during the explosion and fiber content on the mechanical properties of CSBF/PBS biocomposites was investigated. The results showed that the incorporation of CSBF decreased the tensile and impact strength, while significantly enhanced the flexural strength, flexural modulus and tensile modulus. The mechanical properties of biocomposites reinforced by exploded fibers were much better than that of the biocomposites reinforced by non-exploded fibers. Biocomposites reinforced by fibers with 40 and 50 wt% water contents during the explosion had the best mechanical properties. The morphology of CSBF and biocomposites was evaluated by SEM, which demonstrated that fibers with 40 and 50 wt% water contents had better separation and rougher microsurfaces, indicating a better adhesion between PBS matrix and fibers.

Effect of Vibrating Extrusion on the Structure and Mechanical Properties of Isotactic Polypropylene

An electromagnetic dynamic plasticating extruder, invented by the authors, was used to prepare isotactic polypropylene (PP) sheets. Tensile and impact tests show that the extruded samples can simultaneously be reinforced and toughened along the flow and transverse directions in a moderate frequency and amplitude range. The microstructures of the obtained samples were characterized by differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), and scanning electron microcopy (SEM). The results indicate that the vibration plasticating extrusion affected the morphology of the PP extrudate, it especially resulted in finer spherulites, and move tie molecules, which account for the enhancement of the tensile strength and impact toughness of PP sheets in both extrusion and transversal directions.

Influence of process parameters on property of PP/EPDM blends prepared by a novel vane extruder

Abstract In this study, thermoplastic elastomers based on polypropylene (PP) and ethylene-propylene-diene terpolymer (EPDM) were prepared via direct melt blending in a novel vane extruder. The influence of processing temperature and rotor speed on the degree of cross-linking of the EPDM phase, the tensile properties, the melting behavior and the crystallization morphology of PP/EPDM blends was investigated. It was observed that the volume fraction (Vr) of the vulcanizate arriving swelling equilibrium reached the maximum value when the processing temperature was 190°C. The tensile properties showed better performance at 195°C, at which the PP/EPDM blend obtained good dispersive mixing performance. Moreover, the Vr of the vulcanizate arriving swelling equilibrium reached the maximum value when the rotor speed was 60 rpm, at which the dispersive mixing performance and tensile properties of the PP/EPDM blend were better.

Flammable and mechanical effects of silica on intumescent flame retardant/ethylene–octene copolymer/polypropylene composites

The flammable and the mechanical effects of silica (SiO2) on the halogen-free, flame-retarded ethylene–octene copolymer (POE)/polypropylene (PP) composites were investigated. Through the thermal stability analysis and the combustion test, it was found that the SiO2 had a synergistic effect on the intumescent flame retardant (IFR), especially when the SiO2 content was 3 wt%. According to the results of mechanical properties, the tensile strength of composites increased with the rising SiO2 content and most of the impact strength is retained. The fracture morphology showed the state of SiO2/IFR particles in the POE/PP blends, which reflected that with the increasing SiO2 content and the decreasing IFR content, the aggregates became less compact and the size of aggregates became smaller.

Composites of sisal fiber/polypropylene based on novel vane extruder: Effect of interface and damage on mechanical properties

Sisal fibers were pretreated by alkali and maleic anhydride, and then mixed with polypropylene to fabricate sisal fiber-reinforced composites by a self-made vane extruder based on elongational flow field. Maleic anhydride-grafted polypropylene was used as compatilizer to increase the fiber/matrix interactions. The influence of treatment on the fibers structure, the damage to fibers in processing, interfaces of composites and the mechanical properties of composites were investigated. It was observed that the surface of treated fibers was improved obviously compared with that of untreated fibers, which was believed to increase the adhesion between the fibers and matrix. However, the treated fibers were more likely to be damaged during processing. In comparison to unmodified system, the incorporation of treated fibers could significantly enhance the mechanical properties of composites, especially adding the compatilizer of maleic anhydride-grafted polypropylene. The flexural and impact strengths were maximum for the sisal fiber/polypropylene and maleic anhydride-grafted polypropylene composites, and its tensile strength was also improved significantly. The major contribution of this change should be that the morphology of fibers could be well preserved in elongational flow field, which based on the vane extruder showed a good application in fiber-reinforced composites.

Relationship between shear stress and shear strain of polymer melt under vibrating force field

Abstract When a sinusoidal vibration was superimposed in parallel on the flow direction of a polymer melt being extruded through a capillary, the shear stress and shear rate of the polymer melt were analysed with a constant velocity type dynamic rheometer of capillary (CVDRC) devised by the authors. By measuring the instantaneous data of capillary entry pressure, capillary volume flux (or absolute velocity of piston rod) and their phase difference in a vibrating force field, it was found that the relationship between the pulsating amplitude value coefficient of entry pressure and that of volumetric flowrate was an approximate power series; the wall shear stress and wall shear rate of low density polyethylene (LDPE) melt extruded dynamically under various amplitudes and frequencies also exhibited a non-linear proportional relationship.