National Research Council of Canada

Other

Paul Handa

Zhiyi Zhang

The invention disclosed provides integral multilayered polymers with variable interlayer gaps, and processes for their manufacture. The materials thus produced consist of many layers of a polymeric material, which may be a single polymer or a blend of compatible polymers, separated by discontinuous narrow gaps containing air and/or a blowing agent. The layer density can be controlled within a wide range, typically 10 to 2000 layers/mm, while the gap width between the layers can be controlled either to &lE;100 nanometers (called nanolayered polymers) or &gE;1 micrometer (called microlayered polymers), depending on the process. These layered materials are mechanically strong and have excellent thermal and electrical, and sound insulation properties. Two distinct mechanisms were developed for producing such materials. A first process produces nanolayered polymers and involves first introducing a low degree of entanglement among some of the polymer chains and then breaking apart these entanglements using a blowing agent. The microlayer process involves the use of stress-induced nucleation to uniformly grow cells in the polymer containing dissolved blowing agent and force the cells to grow in a preferential direction.

Multilayered polymers and foams with variable sized interlayer gaps

The invention disclosed provides a method for inducing nucleation in a polymer by subjecting the polymer containing dissolved gas to an external stress generated, for example, by applying hydrostatic or mechanical pressure. The applied stress restricts the bubble growth so that the foamed materials have small cells and high cell density. Such microcellular foams can be produced over a wide low temperature range, i.e. from the temperature at which the polymer is conditioned with the blowing agent up to about the glass transition temperature of the polymer-blowing agent system. Stress induced nucleation can also be conducted at higher temperatures i.e. up to about the T of the neat polymer, leading to foams with larger cells. A variety of homogeneous and heterogeneous foams can be produced by this technique.

Manufacturing foams by stress-induced nucleation

The invention disclosed provides a method for inducing nucleation in a polymer by subjecting the polymer containing dissolved gas to an external stress generated, for example, by applying hydrostatic or mechanical pressure. The applied stress restricts the bubble growth so that the foamed materials have small cells and high cell density. Such microcellular foams can be produced over a wide low temperature range, i.e. from the temperature at which the polymer is conditioned with the blowing agent up to about the glass transition temperature of the polymer-blowing agent system. Stress induced nucleation can also be conducted at higher temperatures i.e. up to about the T.sub.g of the neat polymer, leading to foams with larger cells. A variety of homogeneous and heterogeneous foams can be produced by this technique.

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Orleans, CA, United States of America

Paul Handa