Studies on structural foam processing II. Bubble dynamics in foam injection molding

1978 ◽  
Vol 18 (9) ◽  
pp. 699-710 ◽  
Author(s):  
C. A. Villamizar ◽  
Chang Dae Han
Keyword(s):  
Injection Molding ◽  
Bubble Dynamics ◽  
Structural Foam ◽  
Foam Injection Molding

Theoretical and visual study of bubble dynamics in foam injection molding

2009 ◽  
Vol 50 (3) ◽  
pp. 561-569 ◽  
Author(s):  
Mehdi Mahmoodi ◽  
Amir Hossein Behravesh ◽  
Seyyed Abdol Mohammad Rezavand ◽  
Mohammad Golzar
Keyword(s):  
Injection Molding ◽  
Bubble Dynamics ◽  
Visual Study ◽  
Foam Injection Molding

Visualization of bubble dynamics in foam injection molding

2010 ◽  
pp. NA-NA
Author(s):  
Mehdi Mahmoodi ◽  
Amir H. Behravesh ◽  
S. A. Mohammad Rezavand ◽  
Amir Pashaei
Keyword(s):  
Injection Molding ◽  
Bubble Dynamics ◽  
Foam Injection Molding

Foam Extrusion

2006 ◽  
Author(s):  
Chang Dae Han
Keyword(s):  
Carbon Dioxide ◽  
Injection Molding ◽  
Cell Structure ◽  
Initial Pressure ◽  
Structural Foam ◽  
Molten Polymer ◽  
Blowing Agents ◽  
Foam Extrusion ◽  
Blowing Agent ◽  
Foam Injection Molding

There are two processes used in the production of thermoplastic foams, namely, foam extrusion and structural foam injection molding (Benning 1969; Frisch and Saunders 1973). Foam extrusion, in which either chemical or physical blowing agents are used, is the focus of this chapter. Investigations of foam extrusion have dealt with the type and choice of process equipment (Collins and Brown 1973; Knau and Collins 1974; Senn and Shenefiel 1971; Wacehter 1970), the effect of die design (Fehn 1967; Han and Ma 1983b), the effect of blowing agents on foaming characteristics (Burt 1978, 1979; Han and Ma 1983b; Hansen 1962; Ma and Han 1983), and relationships between the foam density, cell geometry, and mechanical properties (Croft 1964; Kanakkanatt 1973; Mehta and Colombo 1976; Meinecke and Clark 1973). Chemical blowing agents are generally low-molecular-weight organic compounds, which decompose at and above a critical temperature and thereby release a gas (or gases), for example, nitrogen, carbon dioxide, or carbon monoxide. Examples of physical blowing agents include nitrogen, carbon dioxide, fluorocarbons (e.g., trichlorofluoromethane, dichlorodifluoromethane, and dichlorotetrafluoroethane), pentane, etc. They are introduced as a component of the polymer charge or under pressure into the molten polymer in the barrel of the extruder. It is extremely important to control the formation and growth of gas bubbles in order to produce foams of uniform quality (i.e., uniform cell structure). The fundamental questions one may ask in thermoplastic foam processing are: (1) What is the optimal concentration of blowing agent in order to have the minimum number of open cells and thus the best achievable mechanical property? (2) How many bubbles will be nucleated at the instant of nucleation? (3) What is the critical pressure at which bubbles nucleate in a molten polymer? (4) What are the processing–property relationships in foam extrusion and structural foam injection molding? Understandably, the answers to such questions depend, among many factors, on: (1) the solubility of the blowing agent in a molten polymer, (2) the diffusivity of the blowing agent in a molten polymer, (3) the concentration of the blowing agent in the mixture with a molten polymer, (4) the chemical structure of the polymers, (5) the initial pressure of the system, and (6) the equilibrium (or initial) temperature of the system.

Interaction Between Foam Injection Molding and Welding Process

2020 ◽  
pp. 233-246
Author(s):  
Karoline Hofmann ◽  
Christian Brütting ◽  
Michael Gehde ◽  
Volker Altstädt
Keyword(s):  
Injection Molding ◽  
Welding Process ◽  
Foam Injection Molding

Rheology of Molten Polymers with Solubilized Gaseous Component

2007 ◽  
Author(s):  
Chang Dae Han
Keyword(s):  
Bubble Dynamics ◽  
High Pressures ◽  
Polymer Solutions ◽  
Polymer Melts ◽  
Gas Bubbles ◽  
Structural Foam ◽  
Molten Polymer ◽  
Gaseous Component ◽  
Molten Polymers ◽  
Thermoplastic Foam

Polymer melts (or polymer solutions) with a solubilized gaseous component (which occur under sufficiently high pressures, thus forming homogeneous mixtures), and polymer melts (or polymer solutions) with dispersed gas bubbles (thus forming heterogeneous mixtures of polymeric fluid and gas bubbles) are encountered in thermoplastic foam processing and polymer devolatilization. Thus, a good understanding of the rheological behavior of such mixtures is very important to the design of processing equipment and successful optimization of such polymer processing operations. From the 1950s through the 1970s, the dynamics of a single, spherical gas bubble dispersed in a stationary Newtonian or viscoelastic medium was extensively reported in the literature (Barlow and Langlois 1962; Duda and Vrentas 1969; Epstein and Plesset 1950; Folger and Goddard 1970; Marique and Houghton 1962; Plessst and Zwick 1952; Rosner and Epstein 1972; Ruckenstein and Davis 1970; Scriven 1959; Street 1968; Street et al. 1971; Tanasawa and Yang 1970; Ting 1975; Yang and Yeh 1966; Yoo and Han 1982; Zana and Leal 1975). While such investigations are of fundamental importance in their own right, they are not much help to describe bubble dynamics in thermoplastic foam extrusion or structural foam injection molding, for instance. There is no question that an investigation of bubble dynamics in a flowing molten polymer with dispersed gas bubbles is a very difficult subject by any measure. Thus, understandably, a relatively small number of research publications on bubble dynamics in a flowing molten polymer have been reported (Han and Villamizar 1978; Han et al. 1976; Yoo and Han 1981). The complexity of the problem arises from other related issues, such as the solubility and diffusivity of gaseous component(s) in a flowing molten polymer, which in turn depend on temperature and pressure of the system. Further, a gaseous component solubilized in molten polymer in the upstream side of a die, for instance, may nucleate as the pressure of the fluid stream decreases along the die axis, after which they could grow continuously as the molten polymer with dispersed gas bubbles flows through the rest of the die.

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