Here's an advantage to gas-assist molding that most plastics engineers probably never considered: It stands up better to high school boys.
By switching its educational chair line Intellect Wave to polypropylene and using gas-assist molding along the base, furniture company KI can eliminate external structural ribs previously needed on its student chairs.
No external ribs means that chairs are easier for school janitors to clean. Also using PP, rather than the previous ABS blend KI used for its student chairs, provides some built-in flexibility that helps the chairs stand up to years of use and abuse by everyone from high school students to preschoolers, said Brian Anundsen, an engineer with Green Bay Wis.-based KI. Anundsen spoke during an interview at the furniture industry's NeoCon World's Trade Fair, held June 9-11 in Chicago.
Designer Shawn Barrett wanted to create a one-piece injection molded seat that would combine flexibility and durability, and eliminate the nooks and crannies in structural ribs where dirt can hide, which forces maintenance workers to spend more time cleaning the seats, Anundsen said.
School seating makes up about a third of KI's annual sales, and the company makes the chairs in a variety of sizes and styles.
Polypropylene also is a key to KI's new Strive side chairs, which typically are used anywhere from lobbies, waiting rooms and offices.
Designer Giancarlo Piretti wanted to create a chair with an articulating back, but without the need for an external mechanism or hinge that would add to the cost of manufacturing it, and make it harder to recycle at the end of its life.
Piretti hit on PP for its ability to provide a living hinge, then added two thin steel rods inserted into a specially molded sleeve on the seat back to boost structural support, said Leo Welter, product manager for the Strive.
``He's using the common properties of both polypropylene and steel,'' Welter said.
The steel rods can be easily removed for recycling, making the chair more environmentally friendly, he said.
KI will work with molders in the United States to produce the major elements of the Strive, including the visible plastics making up the seat and back, Welter said. Molders in China will make other parts.