Transcript Document

Medical
Adhesives
and Sealants
7/21/2015
1
Adhesion
Definition: The state at which two surfaces
are held together by interfacial forces, which
may consist of all known chemical attractive
forces, as well as mechanical interlocking
action or both.
7/21/2015
2
Adhesive

A substance capable of holding materials
together in a functional manner by surface
attachment (performance). A general term
that includes cement, glue, mucilage and
paste.
7/21/2015
3
Sealant

A material applied to a joint in paste or liquid
form that hardens or cures in place, forming a
barrier against gas or liquid entry.
7/21/2015
4
Adhesives and SealantsBiomaterials?





Join components of medical devicesMechanical fastening;
Prevent corrosion;
Resist fatigue;
Fill space – smooth contours-joining
prosthesis to bone;
Wound sealing & closure
7/21/2015
5
Adhesive Materials can be
classified in a number of ways:





Natural or synthetic polymer base;
Thermoplastic or thermosets;
Physical form (one or multiple component,
films, etc)
Functional type (structural, hot melt, pressure
sensitive;
Chemical families (epoxy, silicone, etc.)
7/21/2015
6
General Considerations in the
Application of Adhesive Bonding





When applied adhesives have to 'wet' the surface;
They need to be mobile and flow into all the tiny
nooks and crannies of the substrate;
If the adhesive does not wet the substrate well, poor
adhesion is likely to be a result;
Once good wetting takes place, an adhesive needs
to become solid and not flow at all. This is called
setting or curing (polymerization); and,
Positional indication (imaging).
7/21/2015
7
Adhesive Joint
Breaking strength is determined by:
 Mechanical properties of the materials of the
joint;
 The extent of the interfacial contact (number,
extent, type and distribution of voids);
 Presence of internal stresses;
 The joint geometry; and,
 The details of mechanical loading.
7/21/2015
8
Adhesives are Polymers



Thermoplastics
Thermosets
Available as solids, liquids and pastes and
most can be supported by films of various
thickness.
7/21/2015
9
Adhesives




Acrylics
Epoxies
Polyurethanes
Silicones
7/21/2015
10
Bonding Mechanisms




Mechanical Interlocking;
Formation of covalent bonds across the
interface;
Electrostatic Attraction-dominant
Forces are not significant beyond 0.5 nmtherefore contact is necessary
7/21/2015
11
Surface Treatment







No treatment (low cost poor reproducibility);
Solvent wiping;
Vapor degreasing;
Mechanical abrasion;
Plasma treatment;
Etching;
Chemical deposition-primers, organosilanes
7/21/2015
12
Modes of Failure
A uniform stress pattern in an adhesive joint is seldom produced by
the application of external force.

Structural failure

Adhesive failure

Cohesive failure
7/21/2015
13
Urethanes



Urethane polymerization-diisocyanate and a
diol or diamine
Two part system- mix, spread and cure;
Flexible joint and sealing agent.
7/21/2015
14
Poly (methyl methacrylate)
PMMA
R-Group
7/21/2015
Bone Cement
15
Selection of the starting
monomers

C4-C12-alkyl acrylates supply the initial
adhesion owing to the low glass transition
temperature (Tg).
7/21/2015
16
Degree of Cure ----->
Cure Profile of Condensation
versus Addition Polymerization
Addition polymer
Condensation
polymer
Time
7/21/2015
17
Cyanoacrylates
• In 1959, a variety of cyanoacrylate adhesives were developed, some
types of which are now used for surgical purposes in US, Canada,
and Europe. These glues polymerize on contact with basic substances
such as water or blood to form a strong bond.
• The first glue developed was methyl cyanoacrylate, which was
studied extensively for medical applications and was rejected due to
its potential tissue toxicity such as inflammation or local foreign
body reactions. Methyl alcohol has a short molecular chain which
contributes to these complications.
• By changing the type of alcohol in the compound to one with a
longer molecular chain, the tissue toxicity is much reduced. All the
medical grade tissue adhesives currently available for human use
7/21/2015
18
contain
butyl-esters.
• Cyanoacrylate adhesives were first used on wounded soldiers in
Vietnam: a quick spray over the wounds stopped bleeding and bought
time until conventional surgery could be performed.
• Midwives found cyanoacrylate glue and medical cyanoacrylate
glues useful as the tissue adhesives. Some even used Super Glue
successfully in lieu of suture to close the perineum.
• Surgeons have used household cyanoacrylate adhesive to apply
sutureless pericardial patches that stopped bleeding in critically
injured patients with torn or ruptured myocardium. Cyanoacrylates
are also used in repairing corneas and retinas and as synthetic skin in
treating severe burns.
7/21/2015
19
Methyl 2- cyanopropanoate
R-Group
Methyl -cyanoacrylate monomer polymerizes in the presence
of trace amounts of almost any electron-donor compound (the
initiator) by anionic vinyl polymerization, examples include
water, alcohols, amines, carboxylate ions, and electron rich
olefins.
7/21/2015
20
• Medical grade products currently available contain
either butyl, isobutyl or octyl esters. They are
bacteriostatic and painless to apply, break down
harmlessly in tissue by hydrolysis and are essentially
inert once dry.
•Butyl products are rigid when dry, but provide a strong
bond; octyl products are more flexible when dry, but
produce a weaker bond.
•Histoacryl Blue (n-butyl cyanoacrylate) has been used
extensively for a variety of surgical applications
including middle ear surgery, bone and cartilage grafts,
repair of cerebrospinal fluid leaks, and skin closure -adhesives appear are basically safe.
• DMSO (dimethyl sulfoxide) or acetone serve as
7/21/2015
removers.
21
The Market






The global medical and surgical sealant market is $542 million
(2001) and growing rapidly (19% annually), driven particularly in
the U.S.
Adhesives and sealants are a critical component of medical
devices.
Seven and a half million people receive medical device implants
annually.
As medical devices become smaller and more complex, greater
demands are being made on the materials and components used
in them.
Medical devices are being exported from the U.S. to foreign
countries at an increasing rate.
Devices intended for the growing markets of South America and
the Pacific Rim must be engineered to be cheaper and more
rugged than in the US.
7/21/2015
22
Considerations


One mitigating factor when it comes to the
advancement of new technologies in the adhesives
market is the speed with which the adhesive can be
applied on the production line and how long it takes
before the finished product can be placed on the
market.
This is an area where UV-curable adhesives have
made the strongest technological advances of any
of the newer technologies currently on the market.
7/21/2015
23
Light Cure Systems



Designed for high
speed cure on demand
medical product
assembly.
Solvent free
Wide range of
viscosities designed for
automated dispensing
7/21/2015
24
Light Cure Adhesives




consist essentially of low or medium molecular
weight resins (called oligomers), monofunctional or
multifunctional monomers, photoinitiators and/or
photosensitisers;
wavelengths of 365-250nm.
typically 5-15 seconds at 80-100 mW/cm2 is
sufficient for curing adhesive
visible light curing materials (e.g. resins used in
dental restoration or for bonding and sealing photooptic devices) can be cured with blue light
(wavelength = 470nm).
7/21/2015
25
Typical Applications




Bonding latex balloon onto
PVC lumen in catheters.
Bonding high pressure latex
balloons onto urethane
lumens in high pressure
catheters.
Bonding balloon to multilumen tubes in angioplasty,
thermo dilution, foley and
high pressure catheters.
Bond needle to tubing in
winged infusion sets.
7/21/2015
26
Flexible Adhesive Applications




7/21/2015

Bonding/sealing tracheal
tubes made of silicone
rubber.
Bonding/sealing extruded
silicone parts, colostomy,
ileostomy, urostomy bags
and appliances.
Bonding/sealing the
balloon to the tracheal
tube.
Bonding/sealing the cuff
and tube assemblies in
endotracheal,
tracheotomy, gastrostomy
devices, foley catheters
and other fabricated
silicone parts.
Sealing of inflators.
27
Pressure-Sensitive Adhesives





Arcylics on PET
Labels-many medical devices require a label that
can be printed after the adhesive has been applied
and/or can be written on after application to the
device.
Adhesive tapes for attaching equipment drapes in
sterile environment applications.
Lidding-effective protective barrier against
contamination for storage or shipping;
EKG electrode bonding;
7/21/2015
28
Surgical Drapes
7/21/2015
29
Chemistry
Benefits
Limitations
Typical Applications
Thermoplastic resin
when cured
Poor peel strength,
rigid
Refrigeration
required
Catheter components
Tube-set bonding
Polyolefin bonding
Cyanoacrylate
Substrate versatility
Rapid cure
Adhesion to
polyolefins with
primers
Light-Curable
Acrylic
Substrate versatility
Good resistance
properties
Cure on demand
Capital expenditure
for light-cure
equipment
Needle assembly
Anesthesia masks
Heat exchangers
Oxygenators
Tube-set bonding
Epoxy
Substrate versatility
Superior thermal
and chemical
resistance
Low shrinkage
High gap filling
Poor peel strength,
rigid
Exothermic reaction
Two-part systems
require mixing
Needle assembly
Deep section potting
Polyurethane
Substrate versatility
High peel
Good resistance
properties
Moisture sensitivity
Primers required for
some substrates
Two-part systems
require mixing
Deep section potting
Bonding of tips onto
various components
7/21/2015
30
Benefits of Adhesives






Joins dissimilar materials
Even stress distribution
Fills large gaps
Seals and bonds
Easily automated
Aesthetically acceptable
7/21/2015
31
Limitations of Adhesives




Requires cure
Requires fixture time
Can be messy
Requires chemicals in plant
7/21/2015
32