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Engineering Plastics


WILMINGTON, Delaware, April 11, 2007

Mixer Relies on DuPont™ Delrin® to Help Improve Orthopedic Cement Injection

A patented new mixing dispenser for orthopedic bone cement works smoothly and reliably thanks to five key parts molded from DuPont™ Delrin® acetal. Called the Bocemix, the mixer allows faster, easier and more consistent injection of acrylic bone cement, according to the manufacturer, Bidoia S.a.s. of Peraga di Vigonza near Padua, Italy.

Bocemix acrylic bone cement injector

The good elongation at yield of Delrin® makes it possible to mold a leaf spring as an integral part of the trigger lever (see photo), thus eliminating the need for a metal return spring and related assembly operations. The device also uses a C-shaped anti-screw pull tab held in place with a snap-fit, made possible by the acetal’s combination of toughness and stiffness. The ribbed driving shaft relies on the inherent lubricity of Delrin® together with its high modulus and strength, which the ribbing requires; the mixing blades perform their task, thanks to the material’s flex modulus. The rotary piston is also made of Delrin®.

“The parts in Delrin® would not have been feasible, or would have been more costly, if designed in metals or other materials,” said Dr. Roberta Bidoia, a key executive at Bidoia S.a.s..

The Bocemix offers many attractive features, according to Dr. Bidoia. These include:

  • faster cement preparation time
  • improved mixing quality
  • almost complete elimination of air and gas bubbles from the mixed cement
  • and operation under permanent vacuum.

The mixer is a self-contained system, so there is no need for a separate injector. It is suitable for all types of cement, with some limitations for zirconium dioxide cement, according to Dr. Bidoia. Mixing can be done manually or with an electric power source. The transparent barrel allows visual inspection of the consistency of the cement.

The combination of characteristics of Delrin® acetal that made this design possible include a blend of toughness and stiffness, high tensile strength, dimensional stability and a low-friction surface.

Bidoia S.a.s., established in 1946, is a supplier of medical devices and instruments. The company's products also include osteosynthesis and laparoscopy equipment. For more information, please visit, send an email to or call +39-049-893 0259.

In addition to Delrin® acetal resin, DuPont Engineering Polymers supplies a wide range of engineering thermoplastics for a broad range of uses. To meet needs in the healthcare products industry, the company offers a portfolio that includes grades produced using special manufacturing controls and test protocols.

DuPont is a science-based products and services company. Founded in 1802, DuPont puts science to work by creating sustainable solutions essential to a better, safer, healthier life for people everywhere. Operating in more than 70 countries, DuPont offers a wide range of innovative products and services for markets including agriculture and food; building and construction; communications; and transportation.

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Photo: DuPont
Five injection-moulded parts of unreinforced DuPont™ Delrin® acetal contribute to the smooth, efficient operation of the bone cement mixer from Bidoia: (1) a leaf-spring as an integral part of the trigger lever, (2) the C-shaped antiscrew pull tab, (3) the ribbed driving shaft, (4) the mixing blades and (5) the rotary piston.

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