Originally Published MPMN January 2006

PRODUCT UPDATE

Finding New Ways to Bond

Corinne Litchfield

When choosing an adhesive, manufacturers have many options. The chemical properties of materials to be bonded, as well as the chemical qualities of the adhesive itself, need to be considered. Surface energy, a thermodynamic effect of how a liquid will “wet out” on a surface, is one of these properties. Some plastics may be difficult to adhere to because of low surface energy. In some cases, primers may be required to help with bonding parts. However, thick, overly primed surfaces can cause adhesives to fail. Pretreating surfaces using flame or plasma treatments may improve bonding on some substrates, including polyimide and polycarbonate.

A selection of adhesive products is featured below.

Partnership Leads to Custom Adhesive for Wound Closures

An adhesives manufacturer has partnered with a developer of wound-closure products to create adhesive-coated substrate materials. Adhesives Research Inc. (Glen Rock, PA) and Clozex Medical LLC have teamed up to custom develop two adhesives for use in ClozeX wound closures, a needleless approach to the closure and healing of surgical incisions, excisions, and traumatic lacerations.

In June 2003, Clozex Medical approached Adhesives Research to discuss developing a custom bonding solution for a wound-closure device that would provide an alternative to sutures, staples, and liquid skin adhesives. The tape components in the device would require a noncytotoxic, skin-friendly adhesive. The adhesive had to securely bond to the skin, immobilize the wound-closure device during approximation of the wound margins, and keep the wound closed during the healing process.

To address these needs, Adhesives Research created two custom tape products, each coated on one side with one of the company’s proprietary ARcare adhesives. After developing several constructions and conducting trials with different raw material substrates and coat weights, the ideal coat weight was found for the first adhesive tape system to adhere to the skin for the application. The second tape system was developed with another proprietary adhesive that aggressively adheres to the top of the initial substrate in order to secure the adjustment tabs in place.

ClozeX’s patented device design uses two interlaced, multilayered, transparent films coated with Adhesives Research’s noncytotoxic, hypoallergenic, nonlatex adhesives. The adhesive tapes are designed to affix transparent pads securely to the skin adjacent to the wound and to lock the device in its final closed position. ClozeX wound closures are typically worn for 10–14 days. During wear time, the adhesive must remain in place with no peeling on the edges when rubbed against bedding and clothing.

ClozeX wound closures received the silver Medical Design Excellence Award (MDEA) at the MD&M East trade show in June 2005.

Silicone Adhesives Cure Rapidly

A manufacturer of silicone products supplies two fast-cure silicone adhesives that are suitable for use in medical devices. The MED1-4213 and MED2-4213 adhesives from NuSil Technology (Carpinteria, CA) can be used for bonding and sealing silicones together, as well as with other substrates, such as metals and plastics. The adhesives are two-part, translucent, pourable, self-leveling, high-tear-strength silicone systems. MED1-4213 cures at room temperature, and both products cure rapidly with the application of heat, whether in an oven, or by a heat gun or lamp.

“NuSil applied its expertise in silicone chemistry and adhesives technology to develop these products,” says Stephen Bruner, marketing director. “The MED1-4213 and MED2-4213 adhesives offer the medical device industry a fast-curing solution that removes the bottleneck caused by long curing times.”

Atmospheric moisture is not required for curing, and there are no curing byproducts. Product consistency allows for the adhesives to be supplied in airless, side-by-side kits that eliminate mixing and deairing difficulties. The adhesives can be used in rapid production or prototyping tasks.

Diagnostic Adhesive Turns 15

Even with advances in adhesive technology, some products continue to stand the test of time. A converting company recently celebrated the 15th anniversary of its proprietary diagnostic adhesive. The GL-187 adhesive from G&L Precision Die Cutting (San Jose, CA) was specifically designed for use in medical diagnostic equipment. “We developed GL-187 for the in vitro diagnostics (IVD) industry at a time when most adhesives available were industrial adhesives. The use of industrial adhesives often caused false readings, leading to unreliable tests and a high rejection rate by IVD manufacturers,” says Jennifer Ponti, director of sales. “The sensitivity of GL-187 gave manufacturers the ability to develop more accurate and reliable tests.”

Since introducing GL-187, the company estimates it has produced components used in more than 6 billion test strips for dipstick, lateral-flow, and vertical-flow applications worldwide. From the beginning, the adhesive has been compatible with backed and unbacked nitrocellulous and most other membranes. It works with a number of substrates, including white PVC, white polystyrene, white and clear polyester, and custom materials.

The firm specializes in converting services for the IVD industry, including printing, slitting, and laminating of active membranes, absorbents, and other materials, and laminating multilayer films. Additional services include subassembly of finished devices, dry-room manufacturing, and custom making rotary test strip cutters.

Release Liner Films Are Included in DMF Filing

A manufacturer of precision-coated films offers polyester-based release liners suitable for medical applications. CPFilms Inc. (Fieldale, VA) has developed several liner films, including UV5A, UV10, UV12, UV30, UV50, and UV100 UV-cured. Also available is the S10 fluorosilicone release liner, which can be used with silicone-based, pressure-sensitive adhesives and other materials.

All of these liners are included in a Drug Master File (DMF) that was submitted to FDA late in 2004. “The DMF filing enables us to provide confidential information to FDA, which can then review the liner’s acceptability for use as a component in coated medical substrates,” says Doug Goldstein, new business development manager. “Once approved, FDA can report this information to prospective users of our products,” he adds. This reduces the product development cycle for potential OEMs desiring to test these release films. While awaiting review, an independent laboratory performed toxicity testing and all the liners included in the FDA submission clearly passed, according to the company. Medical applications that often require the use of release films include transdermal drug-delivery systems, disposable diagnostic-test products, wound-closure materials, adhesive bandages, and medical tapes.

Permanent Mounting Adhesive Is Also Removable

A manufacturer of pressure-sensitive adhesive tape systems has developed a permanent and removable mounting adhesive on double-coated polyester film. Adchem Corp. (Riverhead, NY) offers its 8311M-76G mounting adhesive for clean, permanent, and removable bonds to the medical device industry for temporarily mounting foams, polycarbonates, and plastics to glass and other hard surfaces. Even after extended exposure to direct sunlight, the adhesive delivers a strong yet removable bond, according to the company.

With a 76 gloss-gloss liner polycoated to ensure flatness and resist wrinkling, 8311M-76G is moisture resistant. The adhesive features repositioning and removability of less than 1 lb for many surfaces.

The exposed side of the 1¼2-mil polyester film is coated with 1 mil of a high-gloss, high-tack, moderate-peel, high-shear acrylic adhesive. The liner side is coated with 1 mil of a low-peel, high-shear, removable, acrylic-based adhesive. With availability up to 54 in. wide, the tape has a one-year shelf life when stored under cool, dry conditions.

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