Foamed polyolefins are commonly used in a variety of applications including packaging, transportation, building and construction where lightweight material is required. For some applications, crosslinking is used to improve mechanical properties, however, this adds cost, can impact bubble formation and can make the material difficult to recycle. MSU researchers have developed a technology that allows foaming of linear polyolefins such as polypropylene without the need for adding branched polymer. The technology improves the stiffness of the foamed polymer and allows re-melting and reforming of the material.
Description of Technology
The technology is a non crosslinked polyolefin foam composition that incorporates organoclay (nanoclay) a coupling agent and a polymeric modifier and method of making. The resulting thermoplastic foam can be re-melted and reformed, unlike thermoset foams and the bubble size can be optimized. The "nanoclay surface treatment" enables dispersion and compatibility of nanoclay. Furthermore, the addition of organoclay increases stiffness and eliminates the need for cross-linking and adding a long chain branched polymer to achieve the appropriate melt strength for foaming. The technology also includes a thermoplastic seal made from the above material. A considerable amount of experimental work has been done using linear polypropylene.
- Improved melt strength and foamability of linear polypropylene: No cross-linking or long chain branched polymer addition needed to allow proper foaming of the material
- Smaller, more consistent bubble sizes - nanoclay nucleates the foam to reduce density but maintains stiffness
- Up to 25% lower density for foamed linear polypropylene compared to products using branched polypropylene additives
- Environmentally friendly: Adding small amounts of nanoclay maintains the recyclability of the material.
- Less complex and improved processing: The invention uses a pre-blended formulation (master batch) to add to bulk linear polypropylene. Thus, there is no need for processors to deal with adding and dispersing the organoclay.
- Foam applications where lower density is desired but stiffness must be maintained
- Automotive seals (primary and secondary seals in automobiles, weather seals, and instrument panels
- Building insulation (thermal insulation, floor coverings)
- Packaging (protective)
- Medical/Healthcare (protective packaging)
Granted US Patent 9,279,046
SPE Polymer Engineering and Science, 2011 article "Extrusion of Linear Polypropylene–Clay Nanocomposite Foams"
SPE Plastics Research Online, 2011 article "Entangling additives enhance polypropylene foam quality"
Dr. Krishnamurthy Jayaraman, Dr. Tanmay Pathak, Dr. Amit Chaudhary
For Information, Contact:
Michigan State University