scholarly journals Characterization of the Fluidity of the Ultrasonic Plasticized Polymer Melt by Spiral Flow Testing under Micro-Scale

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 357 ◽  
Author(s):  
Bingyan Jiang ◽  
Yang Zou ◽  
Tao Liu ◽  
Wangqing Wu
Keyword(s):  
Size Effect ◽  
Amorphous Polymer ◽  
Polymer Melt ◽  
Mold Temperature ◽  
Polyamide 66 ◽  
Spiral Flow ◽  
Crystalline Polymers ◽  
Micro Scale ◽  
Flow Length ◽  
And Control

The fluidity of a molten polymer plasticized by ultrasonic vibration was characterized by spiral flow testing based on an Archimedes spiral mold with microchannels. Mold inserts with various channel depths from 250 to 750 µm were designed and fabricated to represent the size effect under micro-scale. The effect of ultrasonic plasticizing parameters and the mold temperature on the flow length was studied to determine the rheological nature of polymers and control parameters. The results showed that the flow length decreased with reduced channel depth due to the size effect. By increasing ultrasonic amplitude, ultrasonic action time, plasticizing pressure, and mold temperature, the flow length could be significantly increased for both the amorphous polymer polymethyl methacrylate (PMMA) and the semi-crystalline polymers polypropylene (PP) and polyamide 66 (PA66). The enhanced fluidity of the ultrasonic plasticized polymer melt could be attributed to the significantly reduced shear viscosity.

scholarly journals Prediction of the maximum flow length of a thin injection molded part

2020 ◽  
Vol 40 (9) ◽  
pp. 783-795
Author(s):  
Sara Liparoti ◽  
Vito Speranza ◽  
Annarita De Meo ◽  
Felice De Santis ◽  
Roberto Pantani
Keyword(s):  
Injection Molding ◽  
Maximum Flow ◽  
Mold Temperature ◽  
Complete Characterization ◽  
Rheological Parameters ◽  
Injection Molding Process ◽  
Spiral Flow ◽  
Molding Process ◽  
Molded Part ◽  
Flow Length

AbstractOne of the most significant issues, when thin parts have to be obtained by injection molding (i.e. in micro-injection molding), is the determination of the conditions of pressure, mold temperature, and injection temperature to adopt to completely fill the cavity. Obviously, modern computational methods allow the simulation of the injection molding process for any material and any cavity geometry. However, this simulation requires a complete characterization of the material for what concerns the rheological and thermal parameters, and also a suitable criterion for solidification. These parameters are not always easily reachable. A simple test aimed at obtaining the required parameters is then highly advantageous. The so-called spiral flow test, consisting of measuring the length reached by a polymer in a long cavity under different molding conditions, is a method of this kind. In this work, with reference to an isotactic polypropylene, some spiral flow tests obtained with different mold temperatures and injection pressures are analyzed with a twofold goal: on one side, to obtain from a few simple tests the basic rheological parameters of the material; on the other side, to suggest a method for a quick prediction of the final flow length.

scholarly journals Cavity Air Flow Behavior During Filling in Microinjection Molding

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
C. A. Griffiths ◽  
S. S. Dimov ◽  
S. Scholz ◽  
G. Tosello
Keyword(s):  
Flow Behavior ◽  
Air Flow ◽  
Polymer Melt ◽  
Mold Temperature ◽  
Quality Factors ◽  
Melt Temperature ◽  
Injection Speed ◽  
Microinjection Molding ◽  
Process Dynamics ◽  
Flow Length

Process monitoring of microinjection molding (μ-IM) is of crucial importance in understanding the effects of different parameter settings on the process, especially on its performance and consistency with regard to parts’ quality. Quality factors related to mold cavity air evacuation can provide valuable information about the process dynamics and also about the filling of a cavity by a polymer melt. In this paper, a novel experimental setup is proposed to monitor maximum air flow and air flow work as an integral of the air flow over time by employing a microelectromechanical system gas sensor mounted inside the mold. The influence of four μIM parameters, melt temperature, mold temperature, injection speed, and resistance to air evacuation, on two air flow-related output parameters is investigated by carrying out a design of experiment study. The results provide empirical evidences about the effects of process parameters on cavity air evacuation, and the influence of air evacuation on the part flow length.

scholarly journals Study on External Gas-Assisted Mold Temperature Control with the Assistance of a Flow Focusing Device in the Injection Molding Process

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 965 ◽  
Author(s):  
Nguyen Truong Giang ◽  
Pham Son Minh ◽  
Tran Anh Son ◽  
Tran Minh The Uyen ◽  
Thanh-Hai Nguyen ◽  
...  
Keyword(s):  
Injection Molding ◽  
Temperature Control ◽  
Mold Temperature ◽  
Injection Molding Process ◽  
Melt Flow ◽  
Flow Focusing ◽  
Molding Process ◽  
Heating Efficiency ◽  
Flow Length ◽  
Insert Plate

In the injection molding field, the flow of plastic material is one of the most important issues, especially regarding the ability of melted plastic to fill the thin walls of products. To improve the melt flow length, a high mold temperature was applied with pre-heating of the cavity surface. In this paper, we present our research on the injection molding process with pre-heating by external gas-assisted mold temperature control. After this, we observed an improvement in the melt flow length into thin-walled products due to the high mold temperature during the filling step. In addition, to develop the heating efficiency, a flow focusing device (FFD) was applied and verified. The simulations and experiments were carried out within an air temperature of 400 °C and heating time of 20 s to investigate a flow focusing device to assist with external gas-assisted mold temperature control (Ex-GMTC), with the application of various FFD types for the temperature distribution of the insert plate. The heating process was applied for a simple insert model with dimensions of 50 mm × 50 mm × 2 mm, in order to verify the influence of the FFD geometry on the heating result. After that, Ex-GMTC with the assistance of FFD was carried out for a mold-reading process, and the FFD influence was estimated by the mold heating result and the improvement of the melt flow length using acrylonitrile butadiene styrene (ABS). The results show that the air sprue gap (h) significantly affects the temperature of the insert and an air sprue gap of 3 mm gives the best heating rate, with the highest temperature being 321.2 °C. Likewise, the actual results show that the height of the flow focusing device (V) also influences the temperature of the insert plate and that a 5 mm high FFD gives the best results with a maximum temperature of 332.3 °C. Moreover, the heating efficiency when using FFD is always higher than without FFD. After examining the effect of FFD, its application was considered, in order to improve the melt flow length in injection molding, which increased from 38.6 to 170 mm, while the balance of the melt filling was also clearly improved.

Size Effect of Nanoparticle Diffusion in a Polymer Melt

2014 ◽  
Vol 47 (20) ◽  
pp. 7238-7242 ◽  
Author(s):  
Christopher A. Grabowski ◽  
Ashis Mukhopadhyay
Keyword(s):  
Size Effect ◽  
Polymer Melt ◽  
Nanoparticle Diffusion

A SIZE EFFECT STUDY ON THE SPLITTING CRACK INITIATION AND PROPAGATION IN OFF-AXIS LAYERS OF COMPOSITE LAMINATES

2021 ◽  
Author(s):  
YAO QIAO ◽  
QIWEI ZHANG ◽  
TROY NAKAGAWA ◽  
MARCO SALVIATO
Keyword(s):  
Crack Initiation ◽  
Size Effect ◽  
Fiber Reinforced Polymers ◽  
Structural Behavior ◽  
Crack Initiation And Propagation ◽  
Damage Mechanisms ◽  
Micro Scale ◽  
Morphological Studies ◽  
Initiation And Propagation ◽  
Macro Scale

This work proposes an investigation on size effects in micro-scale splitting crack initiation and propagation and their consequences on the macro-scale structural behavior carbon-fiber reinforced polymers under transverse tension. Towards this goal, size effect tests were experimentally conducted on both notch-free [90]n composites and specimens with different notch types under three-point bending. The mechanical tests were followed by morphological studies to identify the micro-scale damage mechanisms and their evolution. The results clearly show that splitting crack initiation in the transverse direction of composites not only happens at the fiber/matrix interface but also in the matrix. Moreover, the subsequent development of these damage mechanisms can depend on the structure size. This interesting phenomenon inherently leads to size-dependent structural behavior which can be described through Baznt’s Size Effect Laws. This study on the splitting crack initiation and propagation can provide unprecedented information for the calibration and validation of micromechanical models for the damage behavior of fiber composites at the microscale.

Viscous Dissipation of Polymer Melt in Micro Channels and Macro Channels

2014 ◽  
Vol 609-610 ◽  
pp. 521-525
Author(s):  
Bin Xu ◽  
Xiao Yu An ◽  
Liang Chao Li ◽  
Guang Ming Li
Keyword(s):  
Shear Rate ◽  
Viscous Dissipation ◽  
Unit Length ◽  
Experimental Studies ◽  
Polymer Melt ◽  
Characteristic Size ◽  
Micro Scale ◽  
Micro Channels ◽  
Macro Scale ◽  
The Difference

Viscous dissipation is the key factor impacting flowing characteristics of polymer melt. In order to study the difference between micro scale and macro scale, experimental studies of viscous dissipation at various shear rate were investigated with several polymers, including PMMA and HDPE, at different temperature when melts flow through 1000μm,500μm,350μm diameter channels of identical aspects ratio in the paper. The results indicate that the temperature rises caused by viscous dissipation increase with increasing shear rate and the temperature rise for some shear rate decreases with increasing melts temperature. The temperature rises decrease significantly with the reduction of the characteristic size of micro channel at the same shear rate. However, the average temperature rises per unit length increase when the character size of channel decreases. This indicates the shear friction gradually increases with the decrease of channel characteristic size. Therefore polymer melt viscous dissipation effects of micro scale dimensions are different from that of macro-scale dimensions.

Experimental Study of Flexible Electrohydrodynamic Conduction Pumping for Electronics Cooling

2018 ◽  
Author(s):  
Nicolas Vayas Tobar ◽  
Pavolas N. Christidis ◽  
Nathaniel J. O'Connor ◽  
Michal Talmor ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Flexible Electronics ◽  
Electronics Cooling ◽  
Thermal Control ◽  
Stable Operation ◽  
Space Applications ◽  
Manufacturing Method ◽  
Micro Scale ◽  
Wide Range ◽  
And Performance ◽  
And Control

As modern day electronics develop, electronic devices become smaller, more powerful, and are expected to operate in more diverse configurations. However, the thermal control systems that help these devices maintain stable operation must advance as well to meet the demands. One such demand is the advent of flexible electronics for wearable technology, medical applications, and biology-inspired mechanisms. This paper presents the design and performance characteristics of a proof of concept for a flexible Electrohydrodynamic (EHD) pump, based on EHD conduction pumping technology in macro- and meso-scales. Unlike mechanical pumps, EHD conduction pumps have no moving parts, can be easily adjusted to the micro-scale, and have been shown to generate and control the flow of refrigerants for electronics cooling applications. However, these pumping devices have only been previously tested in rigid configurations unsuitable for use with flexible electronics. In this work, for the first time, the net flow generated by flexible EHD conduction pumps is measured on a flat-plane and in various bending configurations. In this behavioral characteristics study, the results show that the flexible EHD conduction pumps are capable of generating significant flow velocities in all size scales considered in this study, with and without bending. This study also proves the viability of screen printing as a manufacturing method for these pumps. EHD conduction pumping technology shows potential for use in a wide range of terrestrial and space applications, including thermal control of rigid as well as flexible electronics, flow generation and control in micro-scale heat exchangers and other thermal devices, as well as cooling of high power electrical systems, soft robotic actuators, and medical devices.

scholarly journals Size effect in micro-scale cantilever beam bending

2011 ◽  
Vol 219 (3-4) ◽  
pp. 291-307 ◽  
Author(s):  
S. H. Chen ◽  
B. Feng
Keyword(s):  
Size Effect ◽  
Cantilever Beam ◽  
Micro Scale ◽  
Beam Bending
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