Opacity Switching Smart Plastic

Problem

A Fortune 100 appliance OEM contacted me looking for an opacity switching smart plastic material. They had spent three years developing a dishwasher with a transparent plastic door only to find customers didn’t like it and complained that they could see their dirty dishes through the door.

The OEM asked me if I knew of a plastic that is opaque at room temperature to hide the dirty dishes, but then becomes transparent when the hot water hits it so you can see the cleaning action. I checked and there was no such material on the market so I set out to create one from scratch.

Action

The requirements for dishwashers are demanding because such a material has to withstand hot water, high pH and detergent exposure for thousands of hours. I decided to start with a styrenic thermoplastic with high chemical resistance and modify it with additives to give the reversible opacity switching behavior. I took three guesses at formulations and one of them had exactly the right transparency temperature for a dishwasher door, 60°C. In just eight days from the customer request I had a cost-effective, injection moldable material with full mechanical and optical data ready for the customer. Trial amounts were produced for a full evaluation of the new smart plastic.

Video of the new smart plastic in action

This video shows two injection molded jugs made of the new patented material. The one on the right has a hair drier above it (out of shot) and as the hot air heats the plastic, it becomes transparent! Then, as it cools, it becomes opaque again. This has generated enormous interest from major companies around the world.

Result

This new, patented smart thermoplastic material has since attracted attention from a multitude of global companies. The transparency temperature can be tuned from -20°C to +80°C making it suitable in a wide variety of applications. Even the BBC had an article about smart windows that change from transparent to opaque to block heat from heating your house (see link below). That material was made using solvents (flammable and toxic) and nanoparticles (expensive). The smart plastic shown here does the exact same thing but at low cost and is completely safe.

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EP 1 985 663 Moulded Article with Temperature Dependent Transparency
Chris DeArmitt, Graham Edmund McKee

New thermo-opaque thermoplastics offer novel visual effects
C. DeArmitt Plastics Additives & Compounding (Elsevier), 9, 6, 30-31 (2007).

Thermochromic and Thermotropic Materials
Arno Seeboth (Editor), Detlef Lötzsch (Editor), Pan Stanford CRC Press, 2013.

BBC Article: ‘Smart’ window switches to dark mode to save energy