Pressure Effects on Rheological Behavior of Melt Polymers – A Discussion in Relation to Polymer Processing

1986 ◽  
Vol 7 (1) ◽  
pp. 47-76 ◽  
Author(s):  
Yasushi Oyanagi ◽  
Kazuhisa Kubota
Keyword(s):  
Shear Stress ◽  
Injection Molding ◽  
Rheological Properties ◽  
Flow Behavior ◽  
Experimental Studies ◽  
Polymer Processing ◽  
Pressure Effects ◽  
Deformation Pattern ◽  
Melt Flow ◽  
Bulk Compressibility

Abstract Polymers have large bulk compressibility in the molten state /1/ and their rheological properties are largely affected by pressure applied in polymer processing. The volumetric strain induced by pressure consists of instantaneous and retarded elastic strains, both of which are proportional to pressure, and recover reversibly when pressure is removed. In many crystalline polymers, as observed by B. Maxwell for polyethylene, retarded elastic strain is large, and due mostly to pressure crystallization. This paper describes results of experimental studies relating pressure effects on rheological properties of melt polymers with polymer processing and bulk properties of products. The following items are discussed: pressure induced shear stress, analysis of local deformation pattern, critical shear stress for melt flow fracture, relationship between power law index and bulk compressibility, effects of hydrostatic pressure on melt flow behavior, pressure efficiency of injection molding, jetting phenomena, shrinkage in injection moldings, residual strain, and super-high-pressure injection molding process.

Effects of ultrasonic injection molding conditions on the plate processing characteristics of PMMA

2018 ◽  
Vol 38 (9) ◽  
pp. 905-914
Author(s):  
Yi-Jen Yang ◽  
Chung-Ching Huang
Keyword(s):  
Injection Molding ◽  
Manufacturing Industry ◽  
Flow Behavior ◽  
Pressure Sensors ◽  
Flow Characteristics ◽  
Local Heat ◽  
Skin Layer ◽  
Polymer Processing ◽  
Melt Flow ◽  
Diverse Field

AbstractPolymer processing is a crucial and diverse field in the manufacturing industry. We investigated the process characteristics and effects of injection molding using ultrasonic vibration. An ultrasonic device was installed in an injection mold; polymer was directly vibrated during injection. An ultrasonic oscillation device 45 mm in diameter was placed in the cavity and used to vibrate a poly(methyl methacrylate) melt at 19 kHz. The amplitude of the acoustic unit was set at 15 μm for the measurements. Moreover, cavity pressure sensors were positioned at the front and rear sides of the vibration region to determine the melt flow behavior under ultrasonic-assisted injection molding conditions. Because of the absorption of ultrasonic energy, local heat was generated inside the resin, thus improving the flow characteristics of the melt. Moreover, the melt flow behavior around the skin layer was changed; the molecular orientation and high shear effect were reduced. Furthermore, the freezing rate of the melt was reduced; thus, the amount of melt pressure lost through the cavity was decreased and the residual stress inside the injection-molded component generated during the photoelastic stress analysis was lower.

Application of ultrasonic-assisted injection molding for improving melt flowing and floating fibers

2016 ◽  
Vol 36 (2) ◽  
pp. 119-128 ◽  
Author(s):  
Yi-Jen Yang ◽  
Chung-Ching Huang ◽  
Jie Tao
Keyword(s):  
Injection Molding ◽  
Glass Fiber ◽  
Flow Behavior ◽  
Line Strength ◽  
Pressure Sensors ◽  
Weld Line ◽  
Flow Characteristics ◽  
Local Heat ◽  
Melt Flow ◽  
Ultrasonic Assisted

Abstract In this study, we investigated the use of ultrasonic technology in assisted injection molding and mold designs. We used an ultrasonic device installed in a mold to vibrate a melt directly, thereby converting kinetic energy into thermal energy. In addition, we developed three flat specimens of different thicknesses (3, 1, and 3-1-3 mm) produced by ultrasonic-assisted injection molds. An ultrasonic oscillation device 45 mm in diameter was placed in the cavity and used to vibrate a polycarbonate or a polycarbonate with 30% glass fiber melt at a frequency of 20 kHz. Furthermore, cavity pressure sensors were positioned at the front and rear of the vibration region for analyzing the melt flow behavior under ultrasonic-assisted injection molding conditions. Because of the absorption of ultrasonic energy, local heat was generated inside the resin, thus forming an oscillatory flow during the packing and holding stages, improving the flow characteristics of the melt, and changing the melt flow behavior around the skin layer to reduce the molecular orientation and high shear effect. The freezing rate of the melt was also reduced to eliminate the glass fiber streaks, floating fibers, and fiber orientation, particularly for thinner parts; the hesitation phenomena were then improved to increase the weld line strength.

scholarly journals Effects of Heating Temperature and Load Weight on Rheological Properties of Waste Plastic Cup

2021 ◽  
Vol 17 (1) ◽  
pp. 39-49
Author(s):  
Halimatuddahliana Nasution ◽  
Winny Winny
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Rheological Properties ◽  
Heating Temperature ◽  
Melt Flow Index ◽  
Flow Index ◽  
Melt Flow ◽  
Waste Plastic ◽  
Load Weight ◽  
Increasing Load

Analysis of heating temperature and load weight to the rheological properties of waste plastic cups is very important to gain fundamental understanding of the structure, characteristics, and processability of the material. The samples were tested using melt flow indexer. The heating temperature investigated were 180°C, 190°C, 200°C, 210°C, 220°C and 230°C, and the weight load were 1,875 g, 2,160 g, 2,835 g, 3,035 g and 3,450 g. The results obtained showed that the rheological properties of products such as melt flow index, shear stress and shear rate increased and the viscosity decreased with the increasing of heating temperature and load weight. For higher heating temperatures, the melt flow index, shear stress and shear rate of waste plastic cup increased significantly with the increasing load weight whereas the viscosity of waste plastic cup did not decrease significantly with the increasing load weight.

scholarly journals Rheological Behaviour of Polypropylene/Kenaf Fibre Composite: Effect of Fibre Size

2011 ◽  
Vol 471-472 ◽  
pp. 513-517 ◽  
Author(s):  
Abdan Khalina ◽  
E.S. Zainuddin ◽  
I.S. Aji
Keyword(s):  
Shear Stress ◽  
Fibre Composite ◽  
Flow Behavior ◽  
Polymer System ◽  
Flow Index ◽  
Processing Temperature ◽  
Melt Flow ◽  
Composite Effect ◽  
Fibre Size ◽  
Kenaf Fibre

In evaluating thermoplastics for their effective performance during processing, rheology properties are very useful. Similarly, in designing processing apparatus, knowledge of rheological behavior of composite melt is critical. In this study, melt flow and viscosity behavior of polypropylene/kenaf fibre composite was investigated using a single-screw extruder. Subsequently, flow behavior of the compounded formulation were evaluated by comparing the melt flow index, flow curve and viscosity curve of the PP and that of the composites at 190oC processing temperature and varying the fibre size. There appears to be a positive linear increase of the apparent shear stress with increase in the apparent shear rate and, as expected, viscosity values for the composite samples are much higher than the PP especially at larger fibre size. The additional of kenaf fibre in composite reduces the MFI value basically because of the hindrances in the plastic flow of the polymer. In addition the increase in viscosity with increase in fibre loading might contributed to the high specific area of the fibre in the matrix thereby increasing the shear stress in the composite. Moreover loading of polymer system with fibre tends to disturb or disorganize the normal free movement of the polymer and certainly hindered the mobility chain segments in flow.

Studying the Rheological Properties of a Polylactide Melt Mixed with Wood Filler

2021 ◽  
pp. 173-179
Author(s):  
Gul’naz A. Sabirova ◽  
◽  
Ruslan R. Safin ◽  
Nour R. Galyavetdinov ◽  
Aigul R. Shaikhutdinova ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Rheological Properties ◽  
Experimental Studies ◽  
Untreated Wood ◽  
Melt Flow Index ◽  
Production Costs ◽  
Flow Index ◽  
Low Grade ◽  
Wood Powder ◽  
Melt Flow

Composite materials based on wood filler are promising materials that are actively conquering the market. This is due to the advantages of using these materials in various fields: weather resistance and environmental compatibility, easy machining and possibility of recycling. Furthermore, it is sustainable use of wastes of timber sawing and furniture and woodworking industries, as well as low-grade wood. Wood powder is also known to be one of the components of consumables used in additive 3D printing technologies. Over the last decade, the commercial use of 3D printers has increased rapidly due to the fact that it allows creating prototype objects of complex shape based on a computer model. Experimental studies were carried out to determine the tensile strength and rheological properties of a composite made of polylactide 4043D, untreated wood powder brand 140 and wood powder thermally modified at 200 and 240 °C. The composite is intended for creation of three-dimensional objects by extrusion using a 3D printer. It was found that with an increase in the amount of filler in the composite, the tensile strength decreases. Also, samples with thermally modified filler show an increase in tensile strength in comparison with samples with untreated filler. Prototypes of 3D threads with different composition were obtained, during the study of which the melt flow index was examined. It was found that with increasing temperature of wood filler treatment the melt flow index increases. With a lower content of wood powder in the melt composition, there is a 2-fold increase in the melt flow index. The knowing of the rheological properties of the resulting compositions will allow achieving maximum performance and reduction of energy and production costs.

Glycerol as Plasticizer for Waste Polystyrene Based Metal Injection Molding (MIM) Binder

2013 ◽  
Vol 845 ◽  
pp. 837-840 ◽  
Author(s):  
Nurul Nadzirah Ismail ◽  
Khairur Rijal Jamaludin ◽  
Norhayati Ahmad
Keyword(s):  
Activation Energy ◽  
Injection Molding ◽  
Rheological Properties ◽  
Flow Behavior ◽  
Palm Stearin ◽  
Metal Injection Molding ◽  
Waste Polystyrene

Except for the binder characteristics and molding conditions, the powder loading has a very important effect on the compact distortion. Three types of feedstocks consist of water atomised SS316L powder with 55% waste polystyrene, 35% palm stearin and 10% glycerol were prepared. The powder loading of each feedstocks are 63%, 64% and 65% respectively. Effect of glycerol at different powder loading on rheological properties in term of flowability (n), activation energy (E) and moldability (α) were investigated. It has been observed that all feedstocks possess pseudoplastic flow behavior which is one of the most crucial requirements in MIM process. The addition of glycerol decreases the flowability index while increased the activation energy.

The Flow Behavior of Core Material and Breakthrough Phenomenon in Sandwich Injection Molding

2003 ◽  
Vol 18 (4) ◽  
pp. 405-411 ◽  
Author(s):  
D. Watanabe ◽  
U. S. Ishiaku ◽  
T. Nagaoka ◽  
K. Tomari ◽  
H. Hamada
Keyword(s):  
Injection Molding ◽  
Flow Behavior ◽  
Core Material
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