Microcellular plastic foams

Figure 2.18. A. scanning electron micrograph of a typical microcellular plastic foam (from ref. (9)), reproduced with permis.sion...

Young A T, Polymer-Solvetn Phase Separation as a Route to Low Density, Microcellular Plastic Foams , J. Cell. Plast., 1987, 23, 55. 

The objective of this study is to introduce new acoustical materials for sound insulation panels that offer significant mass and cost reduction over the current passive noise control treatments with same or better vibro-acoustic performance, compared to the conventional sound insulation panels. Recently, new solutions consisting in the use of microcellular plastic foams have been proposed by the authors [8]. They were anticipated to provide convenient acoustical energy dissipation at the... 

Shimbo M. Foam Injection Technology and Influence Factors of Microcellular Plastics , FOAMS 2000, 162 (2000). 

Journal of Cellular Plastics 36, No.2, March/April 2000, p.148-57 MICROCELLULAR PVC FOAM FOR THIN WALL PROFILE... 

The concept of microcellular thermoplastic foam was developed in the 1980s by researchers at the Massachusetts Institute of Technology and was based on the idea that the creation of a very large number of microbubbles, smaller than the preexisting natural flaws in a polymer, can reduce the material cost and consumption in mass produced plastic parts without compromising mechanical properties [15, 16]. 

Figure 1 Three-Stage constrained foaming process for microcellular plastics panels.

The short-term objectives of the proposed research includes the design and development of a extrusion-assisted rotational foam molding experimental setup that will be utilized to facilitate the understanding of the process and the experimental work intended to determine the feasibility of successfully developing an extrusion-assisted plastic foam fabrication technology for lightweight integral-skin fine-celled as well as microcellular rotationally molded foams. 

Plasticization of glassy polymers induced by CO2 plays an important role in the process of foaming of glassy polymers. The preparation of polymeric foams is aimed at the production of microcellular polymers that have closed cells about 10 pm or less in diameter and cell density of about 10 cells/cm. Such foamed polymeric materials have applications in many areas including biomedical devices. Pioneering work by Skripov and coworkers (54,55) stimulated the original interest in this field. 

Supercritical C02-assisted extrusion applications mainly involve polymer blending, microcellular foaming, particle production, and reactive extrusion. Of course, supercritical CO2 can also be used as an interfacial agent, foaming agent, or plasticizer in other appUcations. 

The use of NMP and/or plasticizers as well as varying foaming conditions was incorporated in a high-throughput experimental methodology during the downselec-tion for the polymer. For the premade VDC-based copolymer from the polymerization track, an RBl-201 VDC-based copolymer product described in Section 4.3.2 resulted in microcellular structures (Fig. 4.5.2). 

Table 5. Mechanical Properties of Microcellular Pure Plastic and WPC Foams...

Microcellular foams can be produced by noncontinuous processes such as a batch process [2, 12, 15, 16, 31, 32, 34, 35], continuous processes such as extrusion and injection molding [24,33,36,37], orby asemicontinuousprocess [38]. Since the semicontinuous process is not extensively used in the scientific community or in the industry, it will not be described in this chapter. Readers are encouraged to refer Ref. 38 for detailed information on this process. To date, microcellular foams have been produced in amorphous polymers [12, 31, 32, 34], semicrystalline polymers [35], and in elastomers [16]. Recently, MCF structures have also been produced in plastics filled with inorganic nanoparticles (montmorillonite) [39-43], as well as organic cellulosic fiber filled plastic composites [12, 31, 32, 34]. 

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