Die opening-induced microstructure growth in extrusion foaming of thermoplastic sheets

2016 ◽  
Vol 36 (2) ◽  
pp. 129-138 ◽  
Author(s):  
Abhishek Gandhi ◽  
Naresh Bhatnagar
Keyword(s):  
Rotational Speed ◽  
Expansion Ratio ◽  
Pressure Drops ◽  
Maximum Expansion ◽  
Foaming Process ◽  
Extrusion Foaming ◽  
Critical Process Parameters ◽  
Die Temperature ◽  
Morphological Transformations ◽  
Thermodynamic Instability

Abstract In this study, the influence of die opening gap on foam attributes during a microcellular extrusion foaming process was investigated. Lower die openings developed higher pressure drops on the foams, as a result of which greater thermodynamic instability was stimulated and, consequently, higher cell density foams along with enhanced expansion ratios were achieved. Further investigations were performed to study the synergistic influence of altering die opening with critical process parameters, namely, screw rotational speed and die temperature, on the foam expansion ratio and morphological transformations. Higher screw rotational speed induced shear nucleation phenomenon, which further enhanced the foaming process significantly. Also, an optimum die temperature was observed, which developed maximum expansion ratio at the lowest die opening gap. This study intends to enhance the understanding of extrusion foam processing among academia as well as among industries.

scholarly journals Bitumen Foaming Optimisation Process on the Basis of Rheological Properties

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1854 ◽  
Author(s):  
Marek Iwański ◽  
Grzegorz Mazurek ◽  
Przemysław Buczyński
Keyword(s):  
Half Life ◽  
Expansion Ratio ◽  
Fractional Factorial ◽  
Effective Control ◽  
Maximum Expansion ◽  
Foaming Process ◽  
Original Apparatus ◽  
Foam Properties ◽  
Foamed Bitumen ◽  
Intended Use

This article discusses the results of bitumen foam properties optimisation with respect to three factors: air pressure, bitumen temperature and amount of water. The test materials were unmodified bitumen 50/70 and bitumen 50/70 modified with 2.5% synthetic wax. The experiment was designed according to the 3(3−1) fractional factorial design. The distribution of parameters of bitumen foam were measured with the authors’ original apparatus using a laser beam. This measurement method increased the accuracy of maximum expansion ratio (ER) and half-life (HL) estimation. Based on HL and ER results, it was found that the foaming process increased bitumen stiffness due to the dynamic ageing of the bitumen. The experimental design allows more effective control over the properties of foamed bitumen with respect to its intended use. The presence of synthetic wax extended the half-life of the bitumen foam.

Effects of pressure drop rate and CO2 content on the foaming behavior of newly developed high-melt-strength polypropylene in continuous extrusion

2020 ◽  
pp. 0021955X2094311
Author(s):  
Eric Kim ◽  
Mu Sung Kweon ◽  
Sandra Romero-Diez ◽  
Anvit Gupta ◽  
Xuejia Yan ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Strong Dependence ◽  
Expansion Ratio ◽  
Average Cell Size ◽  
Average Cell ◽  
Melt Strength ◽  
Pressure Drops ◽  
Foaming Behavior ◽  
Die Temperature ◽  
Drop Rate

We report systematic studies on the foamability of our novel high-melt-strength long-chain branched polypropylene under supercritical CO2. Continuous foaming experiments were conducted using a tandem extrusion system and a set of filamentary dies with similar pressure drops but different pressure drop rates. The foam expansion was controlled by varying the temperature at the die exit. Under identical CO2 loadings, the expansion ratio plotted as a function of die temperature exhibited similar shapes across multiple pressure drop rates. However, the shape of the curve varied across different amounts of CO2, under which the highest achievable expansion ratio occurred at a lower die temperature with increasing CO2 content. The cell density displayed strong dependence on both the pressure drop rate and the amount of dissolved CO2. The effect of the latter became more apparent at lower pressure drop rates. The average cell size decreased with increasing CO2 loading but generally showed weak dependence on pressure drop rate except at the highest value.

FOAMING AND MOISTURE CROSSLINKING OF VINYL TRIETHOXY SILANE GRAFTED ETHYLENE–PROPYLENE–DIENE TERPOLYMER

2022 ◽  
Author(s):  
Zhengwei Lin ◽  
Qinghong Zhang ◽  
Gongliang Wang ◽  
Jie Mao ◽  
Martin Hoch ◽  
...  
Keyword(s):  
High Efficiency ◽  
Low Cost ◽  
Side Reaction ◽  
High Energy ◽  
Expansion Ratio ◽  
Ethylene Propylene ◽  
Foaming Process ◽  
The Matrix ◽  
High Energy Absorption ◽  
Ethylene Propylene Diene Terpolymer

ABSTRACT Moisture crosslinking of polyolefins has attracted increasing attention because of its high efficiency, low cost, and easy processing. However, the crucial shortcoming of moisture crosslinking is that the side reaction of peroxide scorch (precrosslinking) simultaneously occurs in silane grafting. It has been recognized that making peroxide precrosslinking useful is an effective way to broaden the application of moisture crosslinking. A novel foaming process combined with moisture crosslinking is proposed. The matrix of ethylene–propylene–diene terpolymer grafted with silane vinyl triethoxysilane (EPDM-g-VTES) was prepared by melt grafting, with dicumyl peroxide as initiator. Foaming was then carried out with azodicarbonamide (AC) as the blowing agent by making use of precrosslinking. Subsequently, the EPDM-g-VTES foams were immersed in a water bath to achieve moisture crosslinking with dibutyl tin dilaurate as the catalyst. The results showed that VTES was grafted onto EPDM and the EPDM-g-VTES foams were successfully crosslinked by moisture. The EPDM-g-VTES compounds with AC obtained great cells by compression molding with the help of precrosslinking. The mechanical property of the EPDM-g-VTES foam was improved by moisture crosslinking. The moisture-cured foam with 4 wt% AC had an expansion ratio of about three times, which could bear large deformation and showed a high energy-absorption effect.

Effect of rare earth nucleating agent on supercritical CO2 foaming behavior of block copolymerized polypropylene

2021 ◽  
pp. 026248932110536
Author(s):  
Yun Zhang ◽  
Yadong He ◽  
Chunling Xin ◽  
Yanbin Su
Keyword(s):  
Rare Earth ◽  
Saturation Temperature ◽  
Nucleating Agent ◽  
Expansion Ratio ◽  
Good Effect ◽  
Cell Diameter ◽  
Average Cell ◽  
Foaming Process ◽  
Foaming Temperature ◽  
Crystal Content

The rare earth nucleating agent was used to modify block copolymerized polypropylene (PPB) in foaming process. The results show that the crystallization of PPB and the melting temperature of β-crystal increased gradually with increased β-crystal nucleating agent content. The total crystallinity decreased with amount of addition increasing, and the relative content of β-crystal increased first and then decreased. When β-crystal nucleating agent content was 0.4 wt%, the relative β-crystal content reached the maximum value of 95.27%, and the final crystal grain refinement significantly. The addition of rare earth β-crystal nucleating agent has a good effect on improving the uniformity of foam cells. Under the same content of β-crystal nucleating agent and pressure, the average cell diameter and expansion ratio increased with the saturation temperature increasing. After the foaming temperature reaches 155°C, the expansion ratio began to decrease, which was also consistent with the changed trend of relative β-crystal content. At the same content of temperature and relative β-crystal, as the foaming pressure increased, the cell diameter decreased gradually, and the expansion ratio increased first, and then decreased.

Evaluation of the Performance of a Sirocco Fan Driven by a Diesel Engine in Mist Sprayer Applications

2011 ◽  
Author(s):  
Roberto Bettocchi ◽  
Mirko Morini ◽  
Michele Pinelli
Keyword(s):  
Diesel Engine ◽  
Numerical Simulations ◽  
Electric Motor ◽  
Rotational Speed ◽  
A Priori ◽  
Integrated System ◽  
Pressure Drops ◽  
Experimental Campaign ◽  
Sirocco Fan ◽  
Correct Design

The coupling of a sirocco fan, used to supply air to a mist sprayer, and a Diesel engine is studied in order to enhance the performance of the integrated system. In this case, the main problem for the correct design of the fan arises from the fact that it is not possible to define a priori the operating point. In fact, the rotational speed is not fixed as in the case of an electric motor driven fan, but is determined as an equilibrium of the power supplied by the engine and the power absorbed by the fan to recover the pressure drops of the mist sprayer system. In this paper, the experimental campaign performed to characterize the existent fans is presented. Moreover, the sprayer duct is characterized by using literature correlations and by performing numerical simulations. Then, the collected data are elaborated in order to scale the fans in order to enhance the performance of the system.

Shape Characteristics and Condensation Heat Transfer of Supersonic Steam Jet in Subcooled Water

2017 ◽  
Author(s):  
Wang Fangnian ◽  
Qin Huan ◽  
Chen Yaodong ◽  
Bai Ning ◽  
Xing Mian ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Expansion Ratio ◽  
Penetration Length ◽  
Shape Identification ◽  
Maximum Expansion ◽  
Heat Transfer Correlations ◽  
The Look ◽  
Experimental Values ◽  
Regime Map ◽  
Shape Characteristics

The shape characteristics and direct contact condensation (DCC) heat transfer of submerged supersonic steam jet were investigated. One of the shape identification methods is the DCC shape regime map as a function of nozzle exit pressure, mass flux and pool water temperature, another one is the Look Up Table. Then based on the theoretical analysis, the new basic expressions of supersonic steam jet dimensionless penetration length, maximum expansion ratio, and heat transfer correlations were given, which were in terms of Ma number and Ja number. The correlations were nonlinearly fitted and validated well against the experimental data form open literatures. The discrepancies of penetration length and maximum expansion ratio between predicted and experimental values were within ±25% and ±12% respectively. Supersonic steam jet DCC heat transfer is feasible to be calculated via the identification of steam jet shape and selection of the corresponding shape and heat transfer correlations.

Bi-cellular Foam Structure of Polystyrene from Extrusion Foaming Process

2009 ◽  
Vol 45 (6) ◽  
pp. 539-553 ◽  
Author(s):  
Kyung-Min Lee ◽  
Eung K. Lee ◽  
Seong G. Kim ◽  
Chul B. Park ◽  
H.E. Naguib
Keyword(s):  
Foam Structure ◽  
Foaming Process ◽  
Extrusion Foaming

Effect of Die Temperature on Tensile Property of Rheocast Phosphor Bronze

2012 ◽  
Vol 706-709 ◽  
pp. 931-936 ◽  
Author(s):  
Takahisa Kose ◽  
Yasuhiro Uetani ◽  
Katsuyuki Nakajima ◽  
Kenji Matsuda ◽  
Susumu Ikeno
Keyword(s):  
Rotational Speed ◽  
Tensile Ductility ◽  
Casting Machine ◽  
Cylindrical Shape ◽  
Pressure Casting ◽  
Different Temperatures ◽  
Mean Size ◽  
Die Temperature ◽  
Semi Solid ◽  
Small Ingot

Semi-solid slurry of phosphor bronze with fine solid granules for rheocasting was tried to make by passing the low-superheat melt through an opening between a rotating regular octagonal rotor and a circumscribed chill block. The effect of rotational speed on the structure of a solidified small ingot was mainly investigated. The ingot structures were changed from the dendrite of rotor-free condition to the rosette at the rotational speed of 50rpm, and the granular with a mean size of about 50μm at higher than150rpm. The slurries made at 150rpm were rheocast to a cylindrical shape cavity within a die kept at different temperatures from 573 to 1173K by the use of a high pressure casting machine. Microstructures of rheocast cylindrical shape products were granular at the die temperatures lower than 773K and changed to grained one as like recrystallized at higher than 973K. Together with the microstructure change, poor tensile ductility less than 3% at the lowest die temperature was improved up to about 60% at 973K.

scholarly journals Analysis of Bubble Growth in Supercritical CO2 Extrusion Foaming Polyethylene Terephthalate Process Based on Dynamic Flow Simulation

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2799
Author(s):  
Shun Yao ◽  
Yichong Chen ◽  
Yijie Ling ◽  
Dongdong Hu ◽  
Zhenhao Xi ◽  
...  
Keyword(s):  
Polyethylene Terephthalate ◽  
Bubble Growth ◽  
Supercritical Co2 ◽  
Flow Simulation ◽  
The Finite Element Method ◽  
Melt Flow ◽  
Dynamic Flow ◽  
Foaming Process ◽  
Dynamic Rheological Properties ◽  
Extrusion Foaming

Bubble growth in the polymer extrusion foaming process occurs under a dynamic melt flow. For non-Newtonian fluids, this work successfully coupled the dynamic melt flow simulation with the bubble growth model to realize bubble growth predictions in an extrusion flow. The initial thermophysical properties and dynamic rheological property distribution at the cross section of the die exit were calculated based on the finite element method. It was found that dynamic rheological properties provided a necessary solution for predicting bubble growth during the supercritical CO2 polyethylene terephthalate (PET) extrusion foaming process. The introduction of initial melt stress could effectively inhibit the rapid growth of bubbles and reduce the stable size of bubbles. However, the initial melt stress was ignored in previous work involving bubble growth predictions because it was not available. The simulation results based on the above theoretical model were consistent with the evolution trends of cell morphology and agreed well with the actual experimental results.

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