Advanced Materials Research Vols. 11-12

Abstract: This paper introduces the basic theory and significance to study injection molding defects. By virtue of the visualization experimental equipments, generation processes of several typical defects are directly observed and recorded. The generation mechanism of these defects is analyzed. Finally future study plan is advanced.

Abstract: The supercritical liquid technique has been studied in recent years, and the addition of a small amount of entrainer to supercritical liquid can greatly increase the solubility and the efficiency of extraction [1,2]. However, the investigations on the addition of entrainer to supercritical liquid are few [3,4]. In this paper, the influence of different entrainer to prepare the same material is studied, in which the alcohol is looked as entrainer and the carboatomic number increased from 2 to 5.

Abstract: A method for testing an air-spring was advanced in the beginning. Then ANSYS was utilized to simulate the static test. In the simulation, multiple load steps solution was carried out through APDL *DO-LOOP and array parameter method. Scalar parameter PRESSURE was established as inner pressure tracking parameter to update inner pressure. Table parameter PRESSURES was established as inner pressure output parameter to export inner pressure of each load step. Comparison was done between simulation result and test data to prove the feasibility of simulation. Finally, some major parameters such as cord angle and initial inner pressure were taken into account, which had remarkable effect on the air-spring’s performance.

Abstract: Distillation column of special materials having high viscosity or containing solid particles, etc in chemical and petrochemical process is studied in this paper. Packed-column does not fit into this situation and even in a plate column, because of high flow resistance on the plate; it will cause some problems, such as blocking, flooding and shutting down. Here the hydrodynamic performance of flow-guided fixed valve trays (FFVT) is introduced and its hydrodynamic performance has been experimentally studied. With flow-guided holes and trapezoid fixed valves to transfer momentum of the gas bursting forth in a horizontal way to the liquid, the flow on the FFVT is well-proportioned and stable. The hydrodynamic data have been correlated and equations have been obtained for the pressure drop, the entrainment and the gas velocity at weeping point, which can be used for the design of FFVT.

Abstract: The filling process of plastic precise gear is simulated by CAE software and the factors that influence injection molding accuracy in single cavity mold are discussed in this paper. With the assistant of visualization technology, the mechanism of filling unbalance which influences efficient injection molding was especially studied. The model of filling unbalance was supposed that was verified experimentally by visualization technique. It is clarified that the mechanism of filling unbalance results from dissymmetrical temperature distribution on the cross-section of runner, which is strongly influenced by the shear heat and the cooling process in the runner. At the same time, a new method was proposed for improving the filling imbalance by applying appropriate injection molding process without any changes in runner shape of multi-cavity mold.

Abstract: Loss tangent defined by the ratio of loss modulus to storage modulus, G”/G’, is widely used as a measure of energy loss for rubber materials. We can expect high loss tangent due to unstable state of polymer chains in large deformation. However, chemical cross-linking is usually introduced in no deformation where we cannot expect high loss tangent. Even if introduced in deformed state, polymer chains take relaxation before completion of cross-linking. In this study, hence, a novel two-step cure has been proposed. The loss tangent by two-step cure has been found to be higher than that by one-step cure in no deformation, showing effectiveness of the process proposed.

Abstract: Uncured, filled rubbers show remarkable nonlinear viscoelasticity as well as cured, filled rubbers. The nonlinearity may come from change in entanglement and filler network structures. Many people use dynamic modulus to characterize rubber materials. However, dynamic modulus cannot be defined at large strain. Hence we must study a viscoelastic function to be defined at large strain. In addition, we need other information to separate the effects of the change in entanglement and filler network structures on nonlinear viscoelasticity. In this work, we have measured simultaneously relaxation modulus G(γ,t) and electrical resistivity ρ(γ,t) for carbon black (CB)-filled, uncured styrene-butadiene copolymers (SBRs) at wide range of strains. Electrical resistivity at equilibrium, ρ(0,t), showed step-like change at the CB loading between 20 and 35 phr, indicating threshold for filler network formation should exist in the range of values in CB loading. Both G(γ,t) and ρ(γ,t) for the samples having CB loading to be higher than the threshold showed nonlinearity at the strain larger than shear strain γ=0.1, indicating rupture in filler network at large strain.

Abstract: A novel approach to functionalize polypropylene (PP) is presented. This method consists of two steps. Firstly, oligomers of glycidyl methacrylate (GMA) were synthesized via UV photo-polymerization using benzophenone (BP) as initiator. Secondly, the GMA oligomers were grafted onto PP, which was initiated by the free radicals generated through the reactivation of semipinacol dormant groups in the oligomers. By this method, the functionalization of PP could be facilely achieved in a simple system without either organic peroxide initiator or monomer; additionally, degradation of the substrate PP was not observed. This presentation is mainly focused on the characterization of the grafted PP products by XRD, DSC and TGA measurements. It is demonstrated that the melting temperature, crystallinity and the initial decomposition temperature of the grafted PP were all increased, compared with those of the origin PP; the functionalization of PP led to the change of the crystal form from the mixed form of α and β into only α form.

Abstract: A series of thermo-sensitive copolymers and interpenetrating network hydrogels were prepared using PNIPAAm and HEMA.The effects of the PNIPAAm/HEMA ratio on the swelling ratio ,and deswelling and reswelling kinetics of gels at different temperatures and drug release characteristics in vitro were discussed. The results showed that the copolymer and IPN hydrogels exhibited thermo-sensitive swelling characteristics. Therefore, the hydrogels may be useful in the controlled drug delivery systems.

Abstract: Copolymerization of MAn and CHDDVE was conducted by using azobisisobutyronitrile (AIBN) or benzoyl peroxide (BPO) as the initiator, ethyl acetate (EA) or n-butyl acetate (BA) as the solvent, and n-hexane as the precipitator. Effects of several factors on monomer conversion were studied, such as reaction time, reaction temperature, composition of the monomer feed (MAn/CHDDVE) and initiator concentration. Molecular weight and its polydispersity and polymer material morphology were characterized by gel permeation chromatography (GPC) and transmission electron microscope (TEM) technologies, respectively. It was demonstrated that CTC was formed in MAn/CHDDVE system, based on ultraviolet-visible spectroscopy (UV-vis) analysis. The product was alternating copolymer with high crosslinking degree, so it could not be dissolved in common solvents, e.g. water, chloroform, N, N-dimethyl formamide (DMF), tetrahydrofuran (THF) and acetone (Ac).