Key Engineering Materials Vol. 561

Abstract: According to studying the mechanism of open mill mixing in low temperature and its intelligent mixing theory, based on the analysis of the experimental results getting from the self-developed XK-160E type open mill, we established a mathematical model for predicting the mix Mooney viscosity. The inspection and verification of mathematical model results showed that the predicted Mooney viscosity was very close to the practical value indicating a good predictive effect．

Abstract: The six-wing synchronous varying clearance rotors which have been designed for the mixing of short fiber-rubber composite material have special structure, and considering the characteristic of the short fiber-rubber composite material, the flow situation of mixed rubber is very complex. However, the flow field of the six-wing synchronous varying clearance rotors can be analyzed by ADINA. So, the flow situation and mixing situation of the mixed rubber can be analyzed and judged by the FEA results such as the pressure field, viscosity field, shearing force field and velocity field.

Abstract: As unfavorable molding defect, weld lines often result in reduced mechanical properties and poor appearance quality of injection molded parts. In this present work, effects of gate locations on the tensile strength of weld lines were investigated by changing the distances between two gates in 10mm, 20mm and 25mm, respectively. Test specimens were prepared with an all-electrical injection molding machine under different process parameters (injection speed, injection pressure and melt temperature). Visualization method and scanning electron microscope (SEM) were employed to further discuss mechanical test results. Study results indicated that tensile strength of injection molded weld lines was lessened as the increase of gate distances. Higher injection speed, higher injection pressure and lower melt temperature induced to lower weldline tensile strength whatever the gate locations were. Study results also illustrated that it was gate location rather than molding conditions had the most decisive influence on the weldline mechanical properties.

Abstract: Nowadays, with the rapid development of aerospace, auto, communication, consumer electronics and other fields, precision injection molding has been widespread concerned. P-V-T (Pressure-Specific-volume-Temperature) properties are inherent characteristics of polymers. In this paper, P-T parameters were set up in packing stage to achieve constant specific-volume control. Numerical simulation of P-V-T control strategy with Moldflow was carried out. Compared with conventional control strategy, the results showed that P-V-T control of precision injection molding could bring out more uniform density distribution, reduction in volume shrinkage and warpage of molded parts. It was concluded that the P-V-T control method could effectively improve the molding quality of the plastic product.

Abstract: Introduced a experiment measuring method of polymer melt bulk modulus. This method based on the PVT reciprocity principle of polymer melt. Depending on liquid attribute of polymer melt, which means pressure changing caused micro variety of volume of certain quality melt in sealed container, polymer melt bulk modulus under the different temperature and pressure could be measured. According with the Polymer Free Volume Theory, the result proved the scientificity of this method.

Abstract: In this paper, employing the mixing theory of polymer and the numerical simulation of polymer processing, numerical simulation model for dispersive mixing of solid powders in polymer matrix is studied, and a multi factor accumulative size distribution function is established. Based on this, the dispersive mixing processes of black carbon/natural rubber are studied using three-dimension dynamic numerical simulation, and the influences of operating conditions on the dispersive mixing of black carbon are analyzed. The simulation results show that the final size of solid powder aggregates is depended on the rotational speed of rotors. When the maximum shear stress of polymer flow field is sufficient to overcome the cohesive force of solid powder aggregates, the size of aggregates distribution will be related with mixing time.

Abstract: The influence of curing pressure on rubbers’ mechanical properties was researched with experiment. The results show that the curing pressure increased appropriately can improve the curing rate and shorten the curing time. Meanwhile the curing pressure increased also can enhance the tensile strength and 300% stress at definite elongation of the rubber cured but reduce the elongation at break, tension set, tearing strength and the abrasion property of the tread rubber. The properties of each rubber are different from each other with the same curing pressure.

Abstract: Using the intelligent open mill mixing experimental platform, in the light of the all-steel radial tire tread formula, according to the experimental results and using regression analysis method and analysis software, we completed the establishment of the dispersion mathematical model about the open mill rubber. And through the inspection and verification of the model, we know that the multiple correlation coefficient of the model was 0.773 and the level of significance of the t-statistic and F-statistic are less than 0.01, also the absolute error between the predicted value of this model and the measured value is less than 0.7. It shows that the model is quite significant and can be applied.

Abstract: Polymer melt flowing in the multiplying element and matched die was simulated for the flowing uniformity and pressure distribuiton based on ANSYS. The results of simulation revealed that the height difference between outlet and inlet sections of the channels in multiplying element, the length of transition region and forming region of molding die all affected pressure distribution and velocity uniformity at the outlet.

Abstract: Based on the advantages of polymer materials over other materials, rotors which are made of the polymer material, are the functional elements of the rotor-assembled strand, and rotate under certain mass flow rate to obtain heat transfer enhancement and online automatic cleaning. The paper carried out numerical studies on heat transfer and friction loss characteristics of the tube fitted with rotors of different spaces. The comparison of the field synergy angle between plain tube and the tube fitted with rotors was also presented in the paper. The numerical data had good agreement with the experimental data. The numerical studies indicated that the field synergy angle of the rotors inserted tube were significantly smaller than that of the plain tube, which validated that the rotors could significantly enhance heat transfer process and had a better comprehensive performance of heat transfer enhancement though extra friction loss was generated. In addition, both the Nusselt number and friction factor of the tube fitted with rotors increased with the increasing space between rotors; the thermal performance factor of the rotors were all higher than 1, which validated the heat transfer enhancement function of the rotors; meanwhile, the thermal performance factor increased with the space between rotors.