Where Liquid Silicone Rubber is Finding Its Place in Medical Applications

Jim Miller

General Manager

Qure Medical Twinsburg Facility

Qure Medical Background

• Medical Division

–Medical Elastomer Development, Limtech Inc., and Lexington Precision combined to form Qure Medical in 2012

• Automotive and Industrial Division

–Quality Synthetic Rubber and Lexington Precision merged into QSR in 2012

• Tooling and Automation Centers rebranded as Quadra in 2012

• All three divisions operate under “Q Holdings” with headquarters in Twinsburg, OH

Qure Medical Background

• Facilities in Twinsburg OH (Automotive and Medical); Sturtevant WI (Medical and Tooling); Rock Hill SC (Medical); Jasper GA (Automotive); Dongguan China (Automotive and Medical); North Canton OH (Tooling)

• Sales of more than $150,000,000 per year

•More than 70 Liquid Silicone Rubber machines currently running (mostly in medical)

Qure Medical Customers

• Sampling of medical device manufacturers that we sell to

Liquid Silicone Rubber

•Very low viscosity

• Initially introduced decades ago, were known for higher costs and reduced physical properties compared to synthetic gum silicone

• Two part system similar to epoxy (part A and part B)

• Static mixer divides and blends raw silicone

• Pumped directly into injection molding machine specifically designed for LSR molding

•A number of high pressure hoses are required, and they are difficult to clean and maintain during material changes

Liquid Silicone Rubber Molds

•Cool liquid silicone from a water chilled barrel are injected into a hot mold (typically over 300 degrees Fahrenheit)

• Tighter tolerance cutting and grinding necessary to avoid flash

•Valve gates can be used but are water cooled (rather than how thermoplastics are heated valve gates)

• Typically more expensive and harder to maintain than plastic molds

Liquid Silicone Rubber Materials

• Typically available in 15 to 80 Shore A Hardness

• Platinum cure system

–Prone to breakdown if contaminated

–Sulfur borne compounds should be segregated from this process

–For this reason Qure operates a separate facility for Thermoset Elastomers (organic rubber) in Rock Hill, South Carolina

•Good physical properties with great chemical and heat resistance

• Typically very transparent and can be easily sterilized

Application of Silicone in Medical Devices

• Silicone biocompatibility is easy to attain

• Typical sterilization cycles do not have much effect on physical properties

–Eto, gamma/electron beam irradiation, steam autoclaving, dry heat

• Materials are similar to the feel of skin, can be used in devices that contact the body

• Components are soft and conform to shapes, so seals are frequently made from silicone

Fluid Management

Drug Delivery

Medical Surgical

Consumer Healthcare

Safety & General

Application: O-Ring Seals

•Various seals

–Material selected for excellent compression set properties

–Competitive pricing due to fast cycle times

Application: Duckbill Valves

• Excellent ‘bounce back’ properties

• Biocompatibility for fluid delivery into IV

Application: Feminine Hygiene

• Silicone is soft

•Can be cleaned easily for reuse

Application: Internal Wound Drain

• Process is overmolded onto silicone tubing

• Provides superior care to wound because it is soft

•Holes can be punched into part to increase flow from wound

Application: External Wound Drain

•Another overmolded component (onto silicone tubing)

• Low pressure vacuum used with part to suck fluid from wound

Application: Feeding Tubes

• Silicone can be loaded with barium to aid in proper placement with x-ray

• Silicone resistant to stomach acids and feeding solutions

Application: Feeding Tube Bolster

• Silicone is soft and comfortable

• Silicone can be cleaned easily and maintained

• Less likely to have allergic reaction

Application: Pull Style Valve

• Flexibility of material aids in finished valve use

• Soft silicone stem can be grabbed easily by physician during surgery

•Undercuts in steel can be added without compromising demolding

Application: Optical Surgery Component

• Silicone can be molded onto plastic substrate

• Soft silicone protects cornea during procedure

Application: Flexible Strap and Peristaltic Pump Tube

• Long thin molding features can easily be filled with small gates

–Long thin parts are difficult to produce in gum silicone

Application: Balloon

• Silicone undercut core (part flexed to remove from core pin)

• Silicone can be inflated up to 10x molded size

Application: Suction Bulb

• Silicone stretches over one piece core

•Bounce-back ability of material creates suction

Application: Trocar Seal

• Silicone wipes blood and other fluids when device is removed from body cavity

•Biocompatible material

Review

• Silicone is a difficult material to mold

• Equipment maintenance and auxiliary pumps can take time to set up

•Materials are available with biocompatibility and can be sterilized

• Process is similar to plastic injection molding, but mainly ‘the opposite’ when it comes to heat

• Liquid Silicone Rubber is popular for many medical applications

– many uses were covered in this presentation

– many other uses exist

Special Thanks

• Special thanks to Qure Medical Executive General Manager Bernie Stritzke

•Bernie’s book “Custom Molding of Thermoset Elastomers” Liquid Silicone Rubber chapter provided structure for this presentation

Questions and Resources

•More information available at www.qure-med.com

•Contact me to schedule a presentation or workshop at your facility