Xiang Gang Li

Processing and Mechanical Properties of Starch and PVA Composite Reinforced by MCC

The thermoplastic processing and mechanical properties of starch and polyvinyl alcohol (PVA) composites reinforced with microcrystal cellulose (MCC) were investigated. Glycerol with 30 wt% was chosen as the plasticizer for starch and PVA, respectively. MCC with 2 wt% was used to reinforce the starch/PVA composite. The results showed that the mechanical properties of the obtained starch/PVA blend were best when the glycerol content was 30% of starch and 20% of PVA, and the weight ratio of PVA and starch was 4/6 (wPVA/wstarch). After the addition of MCC, the mechanical properties of the starch/PVA blends were improved, and the tensile strength was increased by 52%. Moreover, it was confirmed by rheological measurements that MCC could interact with the composite materials, which results in the improvement of the mechanical strength of the starch/PVA composites.

Preparation and Property Research of PC/PLA Composites Modified By ABS Blending

PC/PLA composite material introduces the degradability of PLA to PC with great performance, but their compatibility and impact resistance are poor. Aiming at this deficiency, ABS is used to modify PC/PLA. This paper established the ternary compound system of PC/PLA/ABS by melt blending and studied the impact of adding ABS and compatibilizer ABS-g-MAH on the composite’s morphology, thermal properties, rheology and mechanical properties. The results showed that: ABS bettered the brittle fracture of PC/PLA and improved the impact strength of composite with the optimum proportion of 30% of PC/PLA mass. In addition, ABS-g-MAH effectively improved the compatibility of the composites as well as mechanical properties of materials. With the increase of ABS, the crystallization ability of PLA in the composite improved and the thermal stability of the system deteriorated slightly, the melt shear viscosity of composite also decreased.

Effect of POSS on the Compatibility and Mechanical Properties of PC/PLA Blends

Polycarbonate/poly (lactic acid)/(PC/PLA) blends were modified by two kinds of POSS, glycidyl POSS (G-POSS) and Octa-ammonium POSS (O-POSS), respectively. The morphologies and mechanical properties of blends were investigated systematically. The results showed that the adding of O-POSS has a better effect on the compatibility of blend than adding G-POSS, the separate phase is invisible in the morphology of blends, and the mechanical properties of blends are improved significantly with the increase of added O-POSS.

Effect of AMPS and Clay on the Acrylic Acid Based Superabsorbent Hydrogels

A kind of superabsorbent hydrogels was synthesized by an optimized rapid solution polymerization of concertrated partically neutralized acrylic acid in the presence of an organic crosslinker agent under normal atmospheric conditions, 2-acrylamide-2-methyl propane sulfonic acid (AMPS) was added into the gels as co-polymerization monomer to enhance the ability of water absorption. Meanwhile, the hydrophilic nanosized clay Laponite XLG was also added into the gels for improving the shape stability and mechanical properties of gels. Through controlling the ratio of monomers and the content of nanosized clay, the superabsorbent hydrogels with excellent swelling ability and good mechanical properties could be gotten.

Study on the Mechenical Properties of PPC/PLA Blends Modified by POSS

Aliphatic polycarbonate Polycarbonate/poly (lactic acid)/(PPC/PLA) blends were prepared by melt blending, 1,2-propanediol isobutyl POSS (P-POSS) were added into the blends as a compatilizer and reinforcer. The morphologies, mechanical properties and rheological properties of blends were investigated systematically. The results showed that the adding of P-POSS could improve the compatibilization of PPC and PLA obviously. The thermal stability of the blends was enhanced but the crystallization was effected slightly. Moreover, the tensile strength and impact strength of blends exhibited a considerably increase.

Loss Angle Testing of Polymer Melts at High Shear Rate

Theoretical and experimental study of loss angle of polymer melts at high shear rate was done based on multi-function and all-electric rheometer (MAR) designed by the authors. The phase difference of the dynamic components of shear strain and shear stress at the capillary wall proved to be as same as the phase difference of superimposed vibration displacement and the entrance pressure. In order to get the loss angle, the intrinsic vibration displacement was defined and original signal was transformed from time domain representation to frequency domain representation by DFT. The experiment results show that the loss angle increases greatly with the increase of the superimposed vibration displacement frequency. It indicates that the viscous losses increase while the elastic properties decrease with the increase of the superimposed vibration displacement frequency. The loss angle didnt change notably with the increase of the piston steady velocity and the superimposed vibration displacement amplitude. This indicates that the viscoelastic properties keep consistence when the shear rate and piston amplitude changes.

The Frequency-Domain Analysis of the Rheological Data Acquired with Multi-Function and All-Electric Rheometer

The key parts of multi-function and all-electric rheometer (MAR) designed by the authors were introduced. The data processing method based on frequency-domain analysis were established. Intrinsic vibration displacement is defined to eliminate the effect of steady velocity displacement and extract the useful information of vibration displacement. The actual frequency, amplitude and phase of the superimposed vibration displacement and the entrance pressure were obtained by the frequency-domain analysis of the intrinsic vibration displacement and the entrance pressure. The control precision of the superimposed vibration displacement frequency and amplitude of MAR proved to be high. The direct current component of entrance pressure can be seen as the mean entrance pressure which stands for the flow resistance. The study of mean entrance pressure is useful in discovering the energy consumption mechanism of the polymer processing introduced vibration energy. Loss angle can be calculate according to the phase of entrance pressure and superimposed vibration displacement. The higher order harmonic of the entrance pressure can be used to characterize the nonlinear viscoelasticity of polymer melts. The factors which depend on the shear rate and influence the viscoelasitic properties can be studied by test the loss angle based on MAR.

Development and Application of Die Swell Data Gathering System Based on Multi-Function and all-Electric Rheometer

A real-time die swell data gathering system was developed based on laser diameter gauge in order to measure the die swell of the viscoelastic materials. Software of the system is compiled by C language. Data gathering, date display, data saving and date analysis were realized. Experimental procedures were established, by which the die swell can be acquired. The laser gauge is put 5cm under the die of self-developed multi-function and all-electric rheometer (MAR) to measure the diameter of the extrudate. The rheological behaviors of the PP/PS blends are tested. The change laws of the melt die swell ratio in the condition of different frequency and amplitude were obtained. Compared with the steady-state extrusion, after introducing vibration force field, the melt die swell ratio decreases obviously. The die swell ratio of the blends decrease in fluctuation state with the increase of the frequency; while decreases gradually with the increase of the amplitude. In addition, with the die length-diameter ratio increases, die swell ratio of the blends decreases gradually.

Processing and Mechanical Properties of Plasticized Starch by Different Plasticization Methods

The thermoplastic processing and mechanical properties of starch were investigated by different plasticization methods. Glycerol was chosen as the plasticizer for starch. The effect of glycerol with different amount was studied. The two plasticizing methods of direct adding and high-speed mixing of glycerol were used to plasticize starch, respectively. The results showed that the suitable processing temperatures ranged from 105°C to 140°C. The tensile strength of the obtained thermoplastic starch decreased and the breaking elongation ratio increased with the increase of glycerol content. When the percent of glycerol was 30%, the extrudate of platicized starch has excellent liquidity and the appearance of the extrudate was smooth. Compared with the plasticizing method of direct adding, the plasticization method of high-speed mixing is more beneficial to plasticize starch.

Study on the Crystallinity and Mechanical Properties of PC/PLA/LLDPE/ Montmorillonite Blends

Polycarbonate/poly (lactic acid)/(PC/PLA) blend is a kind of novel potential material for introducing the degradability of PLA to high performance PC. However, the bad compatibility between PC and PLA results in poor impact resistance and strength, which limits its applications. For resolving the problem, linear low density polyethylene (LLDPE) was added into blend to improve the mechanical properties, especially the toughness. Meantime, nanosized montmorillonite was also used as an additive for modifying the blend. The results showed that the the tensile and impact strength, the elongation at break of PC/PLA all be improved with the increase of LLDPE, the nanosized montmorillonite could also increase the strength of blends when the content is lower than wt5% of blends.