How It Works
Dip Coating: Maximizing the Push in Wheelchair Pushrims
To a lot of people, it's just a large metal ring attached to a wheelchair wheel.
But if you use an ultralightweight wheelchair, you know that metal ring is a pushrim - a critical part of your chair's propulsion system, and a component you use hundreds or even thousands of times per day for your mobility and independence.
So making the pushrim as effective as possible is important.
Dip coating defines any process in which a component is dipped into a polymer, such as Plastisol. The goal of dip coating is to create nonslip, cushioned gripping surfaces; to protect products against abrasion and corrosion; to provide electrical insulation; and to enhance a product's final appearance.
Spinergy, a maker of high-performance wheels for ultralightweight wheelchairs, also offers pushrims. Henry Mathers, CFO of Spinergy, says there are many pushrim designs within the industry. Most wheels are offered with aluminum pushrims, but for wheelchair users who want a more secure grip, Spinergy offers a Plastisol-coated pushrim.
At Spinergy, the pushrim is constructed using an aluminum ring dip that is sent to Molded Devices Inc. (MDI) and dip coated in Plastisol.
At room temperature, Plastisol is liquid. But when it's exposed to a certain elevated temperature, Plastisol gels and then remains solid. This polymer can range in hardness from 33 (softest) to 96 (hardest) Shore A scale durometer. Plastisol is also available to match color, hardness, finish and various properties, including high and low temperature resistance, static dissipation and UV protection.
Plastisol is the most common dip coating material used, but other materials such as latex, neoprene and urethane can be used instead.
Spinergy chose Plastisol for its dip coating because it provided the proper grip for wheelchair users without interfering with the operation of the wheelchair or irritating the operator's hands. Proper grip is even more critical for wheelchair users who have reduced strength in their hands or have lost some hand function.
Mathers says MDI is "able to hold a consistent level of tackiness and durability of material. They also take great care to ensure proper bonding of the vinyl material to the aluminum substrate and have always been very consistent in that regard."
Mathers adds that this was a key requirement: "If the underlying prep work is not done properly, the overall durability of the wheel would be greatly reduced."