Water-Assisted Injection Molding System Based on Water Hydraulic Proportional Control Technique

Water-assisted injection molding（WAIM）, an innovative process to mold plastic parts with hollow sections, is characterized with intermittent, periodic process and large pressure and flow rate variation. Energy savings and injection pressure control can not be .attained based on conventional valve control system. Moreover, the injection water can not be supplied directly by water hydraulic proportional control system. Poor efficiency and control performance are presented by current trial systems, which pressurize injection water by compressed air. In this paper, a novel water hydraulic system is developed applying an accumulator for energy saving. And a new differential pressure control method is proposed by using pressure cylinder and water hydraulic proportional pressure relief valve for back pressure control. Aiming at design of linear controller for injection water pressure regulation, a linear load model is approximately built through computational fluid dynamics（CFD） simulation on two-phase flow cavity filling process with variable temperature and viscosity, and a linear model of pressure control system is built with the load model and linearization of water hydraulic components. According to the simulation, model based feedback is brought forward to compensate the pressure decrease during accumulator discharge and eliminate the derivative element of the system. Meanwhile, the steady-state error can be reduced and the capacity of resisting disturbance can be enhanced, by closed-loop control of load pressure with integral compensation. Through the developed experimental system in the State Key Lab of Fluid Power Transmission and Control, Zhejiang University, China, the static characteristic of the water hydraulic proportional relief valve was tested and output pressure control of the system in Acrylonitrile Butadiene Styrene（ABS） parts molding experiments was also studied. The experiment results show that the dead band and hysteresis of the water hydraulic proportional pressure relief valve are large, but the control precision and linearity can be improved with feed-forward compensation. With the experimental results of injection water pressure control, the applicability of this WAIM system and the effect of its linear controller are verified. The novel proposed process of WAIM pressure control and study on characteristics of control system contribute to the application of water hydraulic proportional control and WAIM technology.

Simulation and Experiment Research on the Proportional Pressure Control of Water-assisted Injection Molding

Water-assisted injection molding（WAIM）,a newly developed fluid-assisted injection molding technology has drawn more and more attentions for the energy saving,short cooling circle time and high quality of products.Existing research for the process of WAIM has shown that the pressure control of the injecting water is mostly important for the WAIM.However,the proportional pressure control for the WAIM system is quite complex due to the existence of nonlinearities in the water hydraulic system.In order to achieve better pressure control performance of the injecting water to meet the requirements of the WAIM,the proportional pressure control of the WAIM system is investigated both numerically and experimentally.A newly designed water hydraulic system for WAIM is first modeled in AMEsim environment,the load characteristics and the nonlinearities of water hydraulic system are both considered,then the main factors affecting the injecting pressure and load flow rate are extensively studied.Meanwhile,an open-loop model-based compensation control strategy is employed to regulate the water injection pressure and a feedback proportional integrator controller is further adopted to achieve better control performance.In order to verify the AMEsim simulation results WAIM experiment for particular Acrylonitrile Butadiene Styrene（ABS） parts is implemented and the measured experimental data including injecting pressure and flow rate results are compared with the simulation.The good coincidence between experiment and simulation shows that the AMEsim model is accurate,and the tracking performance of the load pressure indicates that the proposed control strategy is effective for the proportional pressure control of the nonlinear WAIM system.The proposed proportional pressure control strategy and the conclusions drawn from simulation and experiment contribute to the application of water hydraulic proportional control and WAIM technology.

Modeling and simulation of material distribution in the sequential co-injection molding process

In co-injection molding,the properties and distribution of polymers will affect the application of products.The focus of this work is to investigate the effect of molding parameters on the skin/core material distribution based on three-dimensional(3-D)flow and heat transfer model for the sequential coinjection molding process,and the flow behaviors and material distributions of skin and core melts inside a slightly complex cavity(dog-bone shaped cavity)are predicted numerically.The governing equations of fluids in mold are solved by finite volume method and Semi-Implicit Method for Pressure Linked Equations(SIMPLE)algorithm on collocated meshes,and the domain extension technique is employed in numerical method for this cavity to assure that the numerical algorithm is implemented successfully.The level set transport equation which is used to trace the free surfaces in co-injection molding is discretized and solved by the 5 th-order Weighted Essentially Non-Oscillatory(WENO)scheme in space and 3 rd-order Total Variation Diminishing Runger-Kutta(TVD-R-K)scheme in time respectively.Numerical simulations are conducted under various volume fraction of core melt,skin and core melt temperatures,skin and core melt flow rates.The predicted results of material distribution in length,width and thickness directions are in close agreement with the experimental results,which indicate that volume fraction of core melt,core melt temperature and core melt flow rate are principal factors that have a significant influence on material distribution.Numerical results demonstrate the effectiveness of the 3-D model and the corresponding numerical methods in this work,which can be used to predict the melt flow behaviors and material distribution in the process of sequential co-injection molding.

A Computational Study on Water-assisted Ammonolysis of N-Methyl β-Sultam

The ring opening of β-sultam v/a an H2O-assisted ammonolysis process was studied by using Density Functional Theory（DFT） method at the B3LYP/6-31G level as a further step in the theoretical investigation of the ammonolysis reaction of β-sultams. The calculated pathways are analogous to those previously described for the non-assisted ammonolysis reaction. Solvent effects were assessed by using the polarized continuum model（PCM） method. The results show that mode 1 and pathway a in channel Ⅱ are the most favorable ones in both the cases. The energy barrier of the cleavage of C-S bonds producing P1 is the highest among all the energy barriers. The presence of a solvent in the continuum model disfavors the reaction, whereas the participation of water in the ammonolysis reaction plays a positive role and reduces the active energy greatly. The relative energies of all the transition states in the assisted ammonolysis are 20-80 kJ/mol lower than those for the non-assisted reaction.

The effects of heat treatment on microfluidic devices fabricated in silica glass by femtosecond lasers

We fabricated complex microfluidic devices in silica glass by water-assisted femtosecond laser ablation and sub- sequent heat treatment. The experimental results show that after heat treatment, the diameter of the microehannels is significantly reduced and the internal surface roughness is improved. The diameters of the fabricated microehannels can be modulated by changing the annealing temperature and the annealing time. During annealing, the temperature affects the diameter and shape of the protrusions in microfluidic devices very strongly, and these changes are mainly caused by uniform expansion and the action of surface tension.

Sustainable synthesis of ammonium nickel molybdate for hydrodesulfurization of dibenzothiophene

This paper reports a sustainable,water-assisted,solid-state method for synthesizing ammonium nickel molybdate（（NH4）HNi2（OH）2（MoO4）2,ANM）,a precursor for an unsupported hydrodesulfurization（HDS） catalyst.The associated ANM formation mechanism is also discussed.The synthesis route consists of physical mixing of the raw materials,water-assisted grinding and heating.The formation mechanism involves replacement of a Mo atom by a Ni atom,generating the metastable intermediate（NH4）4（NiH6Mo6O（24））·5H2O.Heating of this intermediate at 120 ℃ removes the added water and produces ANM.Catalysts prepared by this method exhibit almost the same physicochemical properties and catalytic performance during the HDS of dibenzothiophene as materials made from ANM synthesized by a chemical precipitation procedure.Compared with traditional hydrothermal or chemical precipitation methods,this water-assisted,solid-state synthesis provides several significant advantages,including simplifying the synthetic procedure,reducing waste and energy costs and increasing product yields.These features will be highly important with regard to allowing the application of ANM in industrial-scale processes involving HDS reactions.This water-assisted,solid-state strategy can also be extended to the synthesis of isomorphous compounds such as ammonium cobalt（zinc and copper） molybdate.

Quantum Chemistry Study of Hydrolysis Mechanism of 1,2-Thiazetidine 1,1-Dioxide

The hydrolysis of 1,2-thiazetidine 1,1-dioxide has been studied by using ab initio and density functional theory at HF/6-31G*, MP2/6-31G* and B3LYP/6-31G* levels, showing there exist two potential theoretical products. One is N-ethyl amino-methyl sulfonate (P1) in which breaking of bond S–C is concerted, the other is 2-taurine methyl ester (P2) which involves two reaction processes with two different mechanisms: concerted and stepwise. There are two pathways of a and b in stepwise, and the former is the lowest in energy barrier in the hydrolysis of 1,2-thiazetidine 1,1-dioxide. The energy barriers of water-assisted hydrolysis of 1,2-thiazetidine 1,1-dioxide are obviously lower than those of no-water-assisted hydrolysis. Solvent effects have been considered by means of a polarizable continuum model (PCM).

Quantum Chemical Study on a New Mechanism of One-carbon Unit Transfer Reaction: The Water-assisted Mechanism

It is a theoretical study on the water-assisted mechanism of one-carbon unit transfer reaction, in which the en-ergy barrier for each transition state lowered by about 80—100 kJ/mol when compared with the one in no-water-involved mechanism. The water-assisted path 4 is the favorite reaction way. Our results well explained the presumption from experiments.

Theoretical Studies of Water’s and Methanol’s Effects on Alcoholysis of N-Benzyl-3-oxo-β-sultam

The mechanisms about the water’s and methanol’s effects on the alcoholysis of N-benzyl-3-oxo-β-sultam together with their differences have been studied by using density func- tional theory at the B3LYP/6-31G＊ level. The results, in comparison with a previous study on the relative reaction without the assistance of water and methanol, show that the added water or methanol can remarkably reduce the energy barrier of alcoholysis reaction of N-benzyl-3-oxo- β-sultam and the most favorite pathway is the breaking of C–N bond instead of S–N. It is also found that the reaction energy barrier of methanol-assisted alcoholysis is a little higher than that of the water-assisted one.

Proton Transfer Isomerization of Pyrazole in the Ground State:σ vs π Mechanism and Water Assisting Effect

The proton transfer isomerization of pyrazole and the water assisting effect by looping 1 to 4 water molecules on the singlet state potential energy surface have been investigated by using hybrid density functional theory method （B3PW91） with a 6-311＋＋G^＊＊ basis set. Two mechanisms were proposed to explain the mono- and multi-water assisting effects, respectively. The reactants and products of all groups have been characterized on their potential energy surfaces. For the isomerizafion of monomolecule pyrazole, the isomeriz＇ation energy barrier is 46.4 kcal·mol^-1. For the monohydration assisting mechanism, the reactant complex is connected to the product complex via two saddle points. The corresponding isomerization barriers are 46.7and 23.0 kcal·mol^-1, respectively. As to the multihydration assisting mechanism, the isomerization barriers are 12.0, 10.9 and 13.14 kcal·mol^-1 accordingly, when the number of water molecules is 2, 3 and 4, respectively. The multihydration assisting isomerization can occur in water-dominated environments, for example, in the organism, and thereby is crucial to energy transference. The deproton and dehydrogen energies of monomolecule pyrazole and various hydrated pyrazoles were calculated and then found much bigger than the isomerization barriers of their relative complexes, suggesting the impossibility of deprotonation or dehydrogenation. The isomerization of pyrazole is a proton-coupling-electron-migration process, but two different mechanisms are noticed, viz. σ- and π-type mechanisms. The π-bond of pyrazole participates in isomerization in the π-type mechanism, whereas only o-electron takes part in isomerization in the σ-type mechanism.

Modeling and Simulation of Hot Metal Desulfurization by Powder Injection

The desulfurization of hot metal by the mono-injection of lime powder and the co-injection of lime, calcium carbide and magnesium powders is mathematically modeled. The mono-injection model is derived from the continuity equation and is validated using experimental results and data previously reported in the literature. The co-injection model and the rate constant of the injected mixture are determined from the molar fractions and rate constants of the individual powders. The effect of the lime content of the mixture on the desulfurization dynamics is studied and discussed.

Honeycomb-patterned films of polystyrene/poly(ethylene glycol): Preparation, surface aggregation and protein adsorption

Highly ordered honeycomb-patterned polystyrene (PS)/poly(ethylene glycol) (PEG) films were prepared by a water-assisted method using an improved setup, which facilitated the formation of films with higher regularity, better reproducibility, and larger area of honeycomb structures. Surface aggregation of hydrophilic PEG and adsorption of bovine serum albumin (BSA) on the honeycomb-patterned films were investigated. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to observe the surface morphologies of the films before and after being rinsed with water. As confirmed by the FESEM images and the AFM phase images, PEG was enriched in the pores and could be gradually removed by water. The adsorption of fluorescence-labeled BSA on the films was studied in visual form using laser scanning confocal microscopy. Results clearly demonstrated that the protein-resistant PEG was selectively enriched in the pores. This water-assisted method may be a latent tool to prepare honeycomb-patterned biofunctional surfaces.

Micro powder injection molding——large scale production technology for micro-sized components

Micro powder injection molding (μPIM),a miniaturized variant of powder injection molding,has advantages of shape complexity,applicability to many materials and good mechanical properties. Co-injection molding has been realized between met-als and ceramics on micro components,which become the first breakthrough within the PIM field. Combined with the prominent characteristics of high features/cost ratio,micro powder injection molding becomes a potential technique for large scale production of intricate and three-dimensional micro components or micro-structured components in microsystems technology (MST) field.

Theoretical Studies of the Aminolysis for N-Methyl β-Sultam in Solution

The aminolysis and the effect of water on the aminolysis processes of n-methyl β-sultam have been studied using density functional theory （DFF） method at the B3LYP/6-31G＊ level. The stationary structures and energies have been investigated for both reactions to find two different reaction channels. Specific and general solvent effects have been evaluated and the most favored pathway was found. The presence of solvent disfavors the reaction, whereas the participation of water in the aminolysis reaction plays a positive role and reduces the activation energy greatly. All transition states in the assisted aminolysis are 35-70 kJ/mol lower than those for the non-assisted reaction.