Experimental Research on the Viscosity of Polymer Melts Filling through Micro Channels

2011 ◽  
Vol 314-316 ◽  
pp. 1346-1349
Author(s):  
Bin Xu ◽  
Yu Bin Lu ◽  
Guang Ming Li ◽  
Song Xue
Keyword(s):  
Shear Rate ◽  
Flow Model ◽  
Capillary Flow ◽  
Polymer Melt ◽  
Characteristic Size ◽  
Micro Channel ◽  
Test Results ◽  
Micro Channels ◽  
Rate Test ◽  
The Difference

Experimental observations indicate that the viscosity of polymer melt flowing through micro channel is altered with variation of characteristic size of micro channels. The explanation about the trend of various viscosity is inconsistent. In this paper, the micro channel dies of 1000μm ,500μm and 350μm diameter were developed and with several polymers, including PP , PS and HDPE, depending on the capillary flow model, the measurement experiments of polymer melt viscosity were investigated at various shear rate. Test results show that with micro-channel size decrease, the percentage reduction in viscosity increases and the difference of viscosities in different micro channels reduces with increasing shear rate.

Rheological Behavior of Polymethyl Methacrylate (PMMA) Filling through Micro Channels

2011 ◽  
Vol 189-193 ◽  
pp. 451-454 ◽  
Author(s):  
Bin Xu ◽  
Yu Bin Lu ◽  
Guang Ming Li ◽  
Song Xue ◽  
Bei Ping Xiang
Keyword(s):  
Polymethyl Methacrylate ◽  
Rheological Behavior ◽  
Capillary Flow ◽  
Rapid Development ◽  
Polymer Melt ◽  
Characteristic Size ◽  
Micro Channel ◽  
Channel Characteristic ◽  
Micro Channels ◽  
The Difference

With the rapid development of micro injection molding, the determination of melt rheological behavior within micro mold cavity is very important for the accurate simulation modeling. Yet several investigations show the viscosity of melt decreases with the reduction of micro channel characteristic size, but there has been no sufficient experimental data for the conclusion. In this paper, depending on the capillary flow model, the measurement experiments of polymer melt viscosity were investigated when Polymethyl Methacrylate (PMMA) was extruded through the micro channel dies of 1000μm ,500μm and 350μm diameter. Test results show that, as micro-channel size decreases, the viscosity increases and the difference of viscosities in different micro channels reduces with increasing shear rate. This indicates microscopic scale melt rheological behavior of PMMA is different from that of other materials.

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 on Viscous Dissipaition of Polymer Melt in Micro-Channels

2010 ◽  
Vol 97-101 ◽  
pp. 2527-2532 ◽  
Author(s):  
Tong Min Yu ◽  
Hai Xin Bei ◽  
Ze Yu Yan ◽  
Bin Xu ◽  
Hua Xu ◽  
...  
Keyword(s):  
Shear Rate ◽  
Viscous Dissipation ◽  
Amorphous Polymer ◽  
Polymer Melt ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Micro Channel ◽  
Aspect Ratios ◽  
Micro Channels ◽  
Macro Scale

The polymer melts viscous dissipation effects of micro scale dimensions are different from that of macro-scale dimensions. In this paper, the temperature rises due to viscous dissipation were investigated when amorphous polymer material, PMMA, flows through several micro-channels with the diameters of 350μm, 500μm and different aspect ratios. The results indicate that, temperature rises reduce with the increase of inlet temperature of melt and increase with increasing channel’s diameter and aspect ratio at the same shear rate. The outlet temperature rises due to viscous dissipation in all micro channels increase with the increase of shear rate. In addition, the outlet temperature rise grows faster with the decrease of micro-channel’s diameter. Therefore, viscous dissipation effect is significant and should not be neglected in micro channel.

A Simplified ‘Effective Circuit’ Fluid Flow Model for Forced Convection in Oblique Fin Configuration

2014 ◽  
Author(s):  
Nasi Mou ◽  
Poh Seng Lee ◽  
Saif A. Khan
Keyword(s):  
Fluid Flow ◽  
Mass Flow ◽  
Flow Model ◽  
Electrical Circuit ◽  
Flow Paths ◽  
Micro Channels ◽  
Discrete Flow ◽  
Actual Flow ◽  
The Difference ◽  
Full Domain

In this paper, a simplified ‘effective circuit’ fluid flow model is proposed to complement full-domain (geometry based) simulations of fluid flow in novel discrete oblique fin heat sinks. In the proposed model, the discrete flow paths are modeled as effective resistances, and the intersections between discrete flow paths are modeled as ‘nodes’. In an electrical circuit, the current of each branch can be derived from the current division rule, and hence the actual flow rates in the effective circuit are determined by the effective resistances. Simulink R2011b, a graphical extension to MATLAB for modeling and simulation of systems, is chosen to construct the equivalent circuit. The effective resistances are calculated using the well-known friction factor expressions for laminar flow in micro-channels. A full-domain geometry-based simulation is performed on CFX 14.0 serving as a benchmark for the developed ‘effective circuit’ fluid flow model. The results show that for a given total current value and mass flow rate, the difference of pressure drop over the whole heat sink between the simplified flow model and CFX simulation is within 13%. The mass flow distributions obtained from the simplified flow model and the CFX simulation exhibit a common distribution pattern. Interestingly, the simplified flow model is even able to capture flow migration — a distinctive phenomenon of flow in oblique fin geometries. We thus confirm the feasibility of the method of construction of our simplified ‘effective circuit’ fluid flow model.

RELATION BETWEEN SHEAR STRESS AND SHEARING TIME IN SELECTED LUBRICANT COMPOSITIONS

Tribologia ◽  
2018 ◽  
Vol 279 (3) ◽  
pp. 25-33 ◽  
Author(s):  
Ryszard CZARNY
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Rheological Properties ◽  
Tribological Properties ◽  
Shear Stresses ◽  
Test Results ◽  
Molybdenum Disulphide ◽  
Lithium Grease ◽  
Lubricant Composition ◽  
Rate Test

The paper presents the results of studies of the influence of fillers introduced into lubricating greases on changes in values of shear stresses in resulting lubricant compositions. These fillers were powders of graphite, molybdenum disulphide, and PTFE. They are added to grease to improve their tribological properties. They also impact the rheological properties of lubricating compositions, especially on the course of the shear stress, whose value decreases with the duration of the flow of these compositions. Knowledge of changes in the value of this stress is essential in designing central lubrication systems in which these compositions may be used. Tests were performed on lithium grease without fillers as well as on a composition of this grease with the fillers mentioned above. Measurements were carried out using a Rheotest 2.1 rheometer by changing the shearing time at selected gradients of shear rate. Test results have shown that both the kind of filler and the shearing time have an impact on the value of shear stress in the tested lubricant composition.

Effects of Polymer Morphology on the Rheological Behavior of Melt Within Micro-Channels

2008 ◽  
Author(s):  
Shia-Chung Chen ◽  
Rean-Der Chien ◽  
Song-Wei Huang ◽  
Chun-Sheng Chen
Keyword(s):  
Rheological Behavior ◽  
Polymer Melt ◽  
Degree Of Crystallinity ◽  
Micro Channel ◽  
Melt Temperature ◽  
Channel Size ◽  
High Crystallinity ◽  
Micro Channels ◽  
Micro Molding ◽  
Low Crystallinity

Micro molding has shown great commercial potential in recent years and determination of the rheological behavior of the polymer melt within micro structured geometry is vital for accurate simulation modeling of micro molding. The lack of commercial equipment is one of main hurdles in the investigation of micro melt rheology. In this study, a melt viscosity measurement system for low and high density polyethylene polymer melt flowing through micro-channels was established using a micro channel mold operated at a mold temperature as high as the melt temperature. For measured pressure drop and volumetric flow rate, capillary flow model was used for the calculation of viscosity utilizing Rabinowitsch correction. The calculated results of low crystallinity LDPE resin were also compared with those of high crystallinity HDPE resin to discuss the effect of degree of crystallinity on the viscosity characteristics of polymer within micro-channels. It was found that the measured LDPE and HDPE viscosity values in the test ranges are significantly lower (about 40∼56% and 22∼29% for LDPE and HDPE, respectively, flowing through a channel size of 150μm) than those obtained with a traditional capillary rheometer. Meanwhile, the percentage reduction in the viscosity value and the ratio of slip velocity relative to mean velocity all increase with decreasing micro-channel size. In the present study we emphasize that the rheological behavior of the high crystallinity HDPE and low crystallinity LDPE resins in microscopic scale are all different from that of macroscopic scale but HDPE displays a less significant lower. The reason can be attributed to for LDPE resin within the micro-channel can create the higher extra bonding force between the bulk chains than HDPE resin. Thus, it will have the lower adhesive force between the bulk chains with the micro-channel wall, resulting in higher degree of wall slip.

Rheological behaviour of low/high density polyethylene melt flowing through micro-channels

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Chun-Sheng Chen
Keyword(s):  
High Density Polyethylene ◽  
Capillary Flow ◽  
Rheological Behaviour ◽  
Polymer Melt ◽  
Volumetric Flow Rate ◽  
Wall Slip ◽  
High Density ◽  
Mean Velocity ◽  
Channel Size ◽  
Micro Channels

AbstractThe determination of the proper rheological behaviour of the polymer melt within micro structured geometry is vital for accurately simulating the micro moulding. The paucity of suitable equipments is one of main hurdles in the investigation of micro melt rheology. In the present study, a measurement system for the melt viscosity of low and high density polyethylene polymer melts flowing through micro-channels was established. The capillary flow model with Rabinowitsch correction was used in the calculations of the viscosity based on the measured pressure drop and volumetric flow rate. The effect of the morphology structure on the viscosity characteristics for both the LDPE and HDPE resins within micro-channels was investigated and discussed. It was found that the measured viscosity values for LDPE and HDPE in the test ranges are significantly lower (about 40~56% and 22~29% for LDPE and HDPE, respectively, flowing through a channel size of 150μm) than those obtained with a traditional capillary rheometer. Moreover, both the percentage reduction in the viscosity value and the ratio of the slip velocity to the mean velocity increase as the micro-channel size decreases. It can be observed that the rheological behaviours of the HDPE and LDPE resins in microscopic scale are different from those in macroscopic scale as a result of the wall slip effect. It also revealed that the wall slip occurs more easily for the LDPE resin within micro channels than HDPE resin due to enlarged effect of morphology structure.

Determining Method for Mixing and Compaction Temperature of Modified Asphalt Mixture

2017 ◽  
Vol 744 ◽  
pp. 83-86
Author(s):  
Xiao Hu Wu ◽  
Miao Miao Tian ◽  
Jin Yan
Keyword(s):  
Shear Rate ◽  
Asphalt Mixture ◽  
Test Results ◽  
Determination Method ◽  
Compaction Temperature ◽  
Modified Asphalt ◽  
Specific Temperature ◽  
The Difference ◽  
Relationship Of ◽  
The Relationship

According to the relationship of the viscosity and temperature when the mixture reached Optimum compaction effect and the shear rate, the viscosity shear rate of the testing modified asphalt mixture, 60s-1 has been found. The test results show that the difference between the compaction temperature of the modified asphalt mixture and the compaction temperature under the condition of the best compaction effect is 5°C. It shows that the temperature is satisfied with the specific temperature during construction, so the determination method is workable.

Experimental Study of Rheological Characteristics of Polymer Melts in the Micro-Die

2012 ◽  
Vol 550-553 ◽  
pp. 716-723
Author(s):  
Tofek Abddiem ◽  
Da Ming Wu ◽  
Jian Zhuang ◽  
Li Jun Hou ◽  
Ying Liu ◽  
...  
Keyword(s):  
Experimental Study ◽  
Shear Rate ◽  
Polymer Melts ◽  
Capillary Flow ◽  
Slip Rate ◽  
Polymer Melt ◽  
Wall Slip ◽  
Rheological Characteristics ◽  
Capillary Rheometer ◽  
Measured Viscosity

Compared with in the conventional scales, the rheological properties of polymer melts have changed in the micro-scales. Based on the principle of capillary flow and modified with the method of Bagley or zero die micro-die, the rheological characteristics of polypropylene (PP) were investigated using the HAAKE capillary rheometer under the micro-die and conventional die. The results show that: the viscosity of polymer melt modified with the method of bagley or zero die micro-die in the different L/D ratio of micro-die is the same and the shear viscosity of PP decreases with the increase of shear rate; Compared with the viscosity in the conventional scales, the measured viscosity of PP in the micro-scales was reduced by 46% in 0.25mm diameter die, 44% in the 0.20mm diameter die and 88% in the 0.15mm diameter die at the same shear rate; a layer of fixed polymer melt was found in the inwall of the micro-die through the calculation of wall slip rate.

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