|
Conference on Medical Grade Polymers : Report
The recent AMI conference on Medical Grade Polymers (September 12-13,
Philadelphia) attracted a cross-section of the medical device industry. There
were a lot of mechanical engineers visiting to try to understand the materials
that they have to work with and the materials suppliers were happy to provide
the information.
The global medical device/equipment market was valued at $165 billion in 2006
with a further $600 billion in pharma. 54% of devices are used in the US, 25% in
Western Europe and 17% in Asia-Pacific. With the ageing population this market
is set to grow with patients requiring more user-friendly products. Clare
Frissora (SABIC Innovative Materials) described the gamma irradiation stable
polycarbonate and compounds with enhanced lubricity, allowing for ease of
movement of parts. The Ultem range offers biocompatibility, autoclavability and
chemical resistance.
Jim Hicks (Solvay Advanced Polymers) covered the issues in plastic to metal
conversion. This is being done to reduce weight and to save costs (metals such
as titanium are high price). Computer aided engineering is used to predict
material behaviour. Generally the designs have to be adapted to the properties
of the plastic. They have helped to develop a range of products including
surgical instruments such as retractors.
Dr Mattamal (FDA) gave an overview of approvals and in particular adhesives.
The Medical Device User Fee and Modernization Act (MDUFMA) includes user fees
for premarket reviews of new products, from $4,000 for Class I and II to
$200,000 for Class III devices. He commented that it had taken 34 years for the
FDA to approve the higher level cyanoacrylate adhesives. George Cramer
(Adhesives Research) has worked with pressure sensitive adhesives used in device
assembly and applications such as electrodes, drug delivery, wound care,
diagnostic devices and capillary flow devices. Ken Morton (Dymax) described the
capabilities of light cure adhesives, currently used in cardiac catheters,
balloon catheters, needle hubs, laryngeal masks, endotracheal tubes, etc. New
colour technology indicates if the adhesive is fully cured - a form of quality
control.
Mark Yeager (Bayer Material Science) looked at molding efficiency including
factors such as wall thickness, cooling time and ease of assembly. High quality
materials such as polycarbonate can reduce failure rates. The material supplier
is used to working with manufacturers in the whole material selection and
manufacturing process.
Sterilization is a big issue in the device industry with the aggressive
techniques being used to try to prevent the spread of Mad Cow Disease. Josh
Blackmore (RTP) reported on the effects of gamma sterilization on TPEs. It can
cause discoloration and property changes and needs to be tested for each
product. Bob Wells (Saint-Gobain Performance Plastics) looked at the compounding
of SEBS thermoplastic elastomers, which can give a broad range of properties.
Around 2% of the SBC market is medical compounds. TPEs are used in gaskets,
seals, closures, tubing and overmolding.
Brent Hindman of JOA described the link between surface defects and
particulate contaminants in manufacturing and innovative clean room technology.
Donald Dodge gave an overview of the implantable wires from Calmont Wire and
Cable. The three principal polymer insulation materials are Teflon (tough, high
dielectric strength, colourable), polyurethane (tough, flexible, colourable and
impermeable) and silicones (flexible, colourable, and permeable).
Rakesh Kumar (Specialty Coating Systems) looked at the use of parylene (a
vapor deposited fluoropolymer coating) to protect implanted devices such as
electronics, cochlear implants and pacemakers.
André Colas of Dow Corning has extensive experience in silicones - there are
358 registered products in pharma compendia alone. The elastomers reduce
encrustation in urinary catheters reducing patient pain on removal. They have a
wide range of device applications from electrical insulation to skin prostheses
and dressings. The permeability to oxygen allows the skin to breathe.
Michael Hansen of Mack Molding gave the molders view. The material
specification is increasingly moving to the molder who has to work closely with
the designers to meet all the requirements and figure out how to manufacture the
device. It is not uncommon to work with a range of materials and a series of
moulding sequences to produce a product. For example, one battery case had a
clear polycarbonate window insert molded with a rigid case and insert overmolded
with an elastomeric seal material. In another case a surgical instrument was
overmolded with a soft touch handle material - this required a hard PP base and
a TPE-O for softness. He has also worked on metal to plastic conversions.
Christian Bonten of BASF described MABS - a clear ABS with good impact
strength, sterilizability and chemical resistance that has been tested and has a
drug master file number. The company has an expensive policy of keeping all
parts of the production process consistent to support medical device
manufacturers and give 36 months notice of changes.
Peter Colburn (Cyro Industries) looked at diagnostic devices from acrylic
materials with high clarity. As many tests are performed using light
transmittance from samples contained in the acrylic, the optical requirements
are high. These can be affected by factors such as lubricants and the processing
temperature.
Claudia Vaz (DSM Dyneema) has worked on the biocompatibility of UHMWPE
fibers, which are difficult to produce but offer excellent strength for sutures
and fixation devices as they combine strength with 'the softness of silk'.
Tony Walder (Lubrizol Advanced Materials) looked at the uses of thermoplastic
polyurethanes in medical devices - the variable chemistry means that they can be
adapted. They offer flexibility, strength, biocompatibility, softening and ease
of processing. Polycarbonate based polyurethanes are being used in long-term
implants.
Medical Grade Polymers 2007 provided a place for mechanical engineers to meet
chemists and work together on the challenges of producing safe medical devices.
(Ref:
http://www.plastemart.com/plasticnews_desc.asp?news_id=10894&P=P) |
