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Many modern plastics are formulated specifically
to be anti-corrosive in specific chemical and environmental
conditions.Asaresult,thesepolymersalsotendtobedifficult
to chemically bond because of their low surface energies,
low porosity, and non-polar or non-functional surfaces.
They feature no functional site or surface roughness onto
which an adhesive can secure itself. In other words, they
are extremely smooth and slippery, so there’s nothing for
the glue to grab onto.
Being able to effectively bond two surfaces together can
be useful in many situations. Yet, few adhesives offer consistently
high bond strengths. In order to steer you towards the best adhesives
on the market, we’ve expanded our list of glues (and plastics!) since
our last blog post on the subject.
We tested the bonding capabilities of various glues that purport to
be compatible with some of the most difficult-to-bond polymers. We
tried sticking each sample of plastics (listed right) to itself and after a
24-hour curing time we attempted to break the pieces apart to
determine which glues worked best. Read on for our results!
Teflon (PTFE) »
A synthetic fluoropolymer characterized by its
excellent dielectric properties, high melting
temperature, and non-reactivity. Teflon has
one of the lowest coefficients of friction in the
world of plastics
Polyethylene »
A thermoplastic with high impact resistance,
low density, and good toughness. This plastic is
especially useful where moisture resistance
and low cost are required.
Polypropylene »
A thermoplastic polymer that is rugged and
unusually resistant to many chemical solvents,
bases and acids, making it useful in a wide
variety of applications.
Polyurethane »
An elastomeric material of exceptional physical
properties including toughness, flexibility, and
resistance to abrasion and temperature. It
combines the toughness of metal with the
elasticity of rubber.
Nylon »
A commonly used synthetic polymer because of
good mechanical properties, wear resistance
and high melting point. Nylon is frequently
used when a low cost, high mechanical strength,
rigid and stable material is required.
Lexan »
An amorphous polycarbonate polymer that
offers a unique combination of stiffness,
hardness and toughness. It exhibits excellent
weathering, creep, impact, optical, electrical
and thermal properties.
What makes these plastics so difficult to bond?
Objective
Materials
DISCLAIMER: The information listed here is intended as a guide
only. Companies should do their own testing when using the above
materials. Craftech Industries cannot be held responsible for any of the
information listed here.
*
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LOCTITE®
Plastics Bonding System »
Our Results
The Loctite Plastics Bonding System was the easiest
glue to use. After priming and gluing the samples
together, we let them cure for 24 hours then attempted
to break the bond created. The plastic sounded like it
splintered as we broke the bonds, however we were not
able to break apart the Lexan or Polyurethane samples.
NB: This adhesive caused clouding and discoloration
on our Lexan sample, indicating a chemical reaction. If
appearance is a concern, make sure to always test any
glue on a piece of scrap material.
A two-part cyanoacrylate adhesive that sets in seconds and doesn’t require clamping.
It’s quick, easy, and Loctite boasts its effectiveness on hard to bond plastics such as
Plexiglass™, polycarbonate, polystyrene, PVC, polyethylene and polypropylene.[ ]
TECHBOND
BP Blue »
What is cyanoacrylate
and how does it work?Our Results
We were excited to try out this adhesive because the
manufacturers boasted that their product was the solution to
bonding hard-to-bond plastics. For our first attempt, we left
the plastics untreated and didn’t roughen the surface with any
kind of wire scrub or sandpaper. After twenty-four hours of
curing, all of the plastics broke apart with ease. However, after
sanding, this adhesive bonded all of our samples perfectly.
Even wedging a screwdriver into slight gaps between the
pieces didn’t work!
Cyanoacrylate is more commonly
referred to as superglue and hardens
very quickly when trapped between
two surfaces. The reaction is caused
by the condensed water vapor on
the surfaces, so humidity is a factor
that may affect bonding capabilities.
Cyanoacrylate is ideal for a tight join
between two stationary parts and the
bond seems to weaken if exposed
repeatedly to temperature changes,
so it is not ideal for outdoor or
mechanical use.
A one-step cyanoacrylate solution engineered to bond with polymer
strings, quickly, easily and permanently. It creates a molecular
bond which provides a stronger, more durable result.[ ]
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LOCTITE®J-BWELD
Epoxy Plastic Bonder »
PlasticWeld »
What is epoxy and
how does it work?Our Results
Our first try with this adhesive proved a failure because we missed
the crucial step of sanding the plastic with 220 grit sandpaper to
roughen the surface. However, after sanding and re-gluing the
pieces, it became quite a challenge to break them apart. We only
managed to break apart the polyurethane sample after wedging
a screwdriver into a small space between the layered pieces and
even then it was quite a bit of work to manage to break the bond.
The other samples held together well, even though the epoxy
wasn’t recommended for polyethylene, polypropylene, Teflon™
or other non-stick surfaces.
Our Results
This adhesrive also called for roughening the surface
with sandpaper to give the glue some added grip. The
PlasticWeld worked well on our samples. It spread
to create a gap-free bond, filling in all the available
space for strong adhesion that just wouldn’t quit,
even after we tried desperately to separate the parts.
NB: We recommend wearing a face mask when
using the PlasticWeld as the chemical smell was
quite powerful.
Epoxy is also known as polyepoxide. It
is basically a thermosetting polymer
created by a manual reaction of a
resin and a hardener; where the resin
is an epoxide and the hardener is a
polyamine. Epoxy resin and epoxy
hardener are mixed together to
different ratios depending upon
the needs of the user. The more the
hardener is added, the more time
it takes to set. Hardener makes the
whole compound stronger. Epoxy is
resistant to water and can even cure
underwater.
An acrylic formula that is specially formulated to bond and repair plastic surfaces. The
double syringe dispenses equal amounts of each component which produces a tough, rigid,
high strength bond in 20 to 25 minutes with a full cure in twenty-four hours.
]
A hand-mixable, fast-setting epoxy putty that forms a durable bond to most major
plastic types. It has a 20-25 minute work life with a functional cure in 2-3 hours. It is not
recommended for polyethylene, polypropylene or some other plastics.[ ]
[
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PLEXUS®3M™
MA310 Adhesive »
Scotch-Weld™ DP8010 »
What is methacrylate
and how does it work?Our Results
The MA310 is not for someone on a strict budget.
This adhesive required the purchase of an applicator
gun, mixing nozzles, and the correct ratio plunger.
If you have all these materials, then applying the
MA310 is a breeze. For this adhesive, we sanded and
clamped the samples and, after the 24 hours, trying
to break the bond created proved to be extremely
difficult. We were not able to break the samples of
any of our plastics apart.
Our Results
This structural adhesive also requires the use of an
applicator gun, mixing nozzles, and the correct ratio
plunger. Even though the directions said we did not have
to roughen the surface, we did anyway just to improve
the chances of a strong bond. Again, we obtained perfect
results. Even Teflon, a notoriously slippery material,
bonded tightly to itself. The soft plastic even chipped
when we tried to break the bond.
Methacrylate adhesives, also referred to
as acrylic adhesives, are incredibly strong
and easy to use. Once the curing agent
and resin are mixed, they chemically react
to form chemical chains that bind with each
other and certain surfaces, particularly
plastics and metals. Unlike epoxies,
thorough mixing is not as crucial and, once
the chemical reaction initiates, the rate of
reaction increases to provide more rapid
strength build-up.
A two-part methacrylate adhesive designed for structural bonding of thermoplastic,
metal and composite assemblies. Combined at a 1:1 ratio, it has a working time of 15 to 18
minutes and achieves a rapid fixture in 30 to 35 minutes at room temperature. Particularly
well suited for bonding thermoplastic materials, the MA310 combines high strength and
stiffness with the ability to adhere difficult-to-bond materials. Supplied in ready-to-use
cartridges.
Two-part acrylic based adhesive with a 10:1 ratio that provides high quality bonding
performance on most low surface energy plastics including polypropylene, polyethylene
and thermoplastic olefins without surface treatment.[ ]
[ ]
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STANLEYAMAZINGGOOP
Hot Glue Gun »
All Purpose Adhesive »
What is hot melt adhesive
and how does it work?
Our Results
We used two different types of hot melt adhesives, all-purpose glue
sticks and Formula II super strength glue sticks. Both sticks had a
hit or miss success rate. After 24 hours, Teflon and polyethylene split
pretty easily. Polyurethane didn’t create a bond at all. Polypropylene
was a bit more successful. While we were still able to break the bond, it
was very difficult. The hot melt adhesive was most effective on nylon,
which we were able to break after a lot of effort and maneuvering with
a screwdriver wedged between the two pieces, and Lexan, which we
were not able to break at all. There didn’t seem to be any difference
between the all-purpose and the Formula II super strength glues, as
each yielded the same results on the samples.
Our Results
This adhesive created a bond that worked like elastic.
As we attempted to break the pieces apart, the glue
snapped them back into place until the bond was
completely severed. It was very difficult, but in the
end we were able to separate all the pieces.
Additionally, the Amazing Goop lived up to its name:
it is extremely goopy, making it less than ideal for
small, delicate projects.
Hot melt adhesives contain a wide range of
elements, including ethylene-vinyl acetate, wax,
resin and any assortment of polyamide, poly-
ethylene, polyester or polypropylene. In
industrial use, hot melt adhesives provide several
advantagesoversolvent-basedadhesives.Volatile
organic compounds are reduced or eliminated
and the drying or curing step is eliminated. Hot
melt adhesives have a long shelf life and usually
can be disposed of without special precautions.
Some of the disadvantages involve thermal
load of the polymer, limiting use to polymers
not sensitive to higher temperatures, and loss
of bond strength at higher temperatures, up to
complete melting of the adhesive.
A form of thermoplastic adhesive that is commonly supplied in solid cylindrical sticks of
various diameters. The glue squeezed out of the heated nozzle is initially hot enough to
burn and blister skin, so use with caution. The glue is tacky when hot, and solidifies in a
few seconds to one minute. It does not lose thickness during solidifying.[ ]
Scientifically formulated to repair, seal and stick to a wide variety of
materials with superior strength to any other brand. Does not become
brittle in cold weather. Good for bonding items subject to vibration.
Safe for applications exposed to dilute acids and dilute caustics.[ ]
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After sticking everything togehter (even our fingers) we’ve found the best adhesives
to use on those pesky plastics and the winners seem to be J-B Weld, Plexus, and 3M!*
What is the best adhesive for hard-to-bond plastics?
Lexan Teflon Nylon Polypropylene Polyurethane Polyethylene
Tech Bond BP Blue very strong very strong very strong very strong very strong very strong
Loctite Bonding System strong weak weak weak strong weak
Loctite Epoxy strong strong strong strong decent strong
J-B Weld Plasticweld very strong very strong very strong very strong very strong very strong
Plexus MA310 very strong very strong very strong very strong very strong very strong
3M Scotch-Weld DP8010 very strong very strong very strong very strong very strong very strong
Hot Glue Gun very strong weak strong relatively strong no bond created weak
Amazing Goop decent decent decent decent decent decent
Adhesive Base Curing Time Tensile Strength Temp Guidelines
Tech Bond BP Blue Modified Ethyl 24 hours 13053 to 18854 psi -65° F to 220° F
Loctite Bonding System Ethyl Cyanoacrylate 24 hours 290 to 2900 psi up to 180° F
Loctite Epoxy Methyl Methacrylate 24 hours 2903 to 3477 psi -40° F to 180° F
J-B Weld Plasticweld Epichlorohydrin & Bisphenol A 1 hour 3200 psi -67° F to 500°F
Plexus MA310 Methacrylate 30 - 35 minutes 3988 to 4496 psi -67° F to 249° F
3M Scotch-Weld DP8010 Acrylic 8 - 24 hours 2400 psi -20°F to 180°F
Hot Glue Gun Ethylene Vinyl Acetate 60 seconds 391 psi 0° F to 359° F
Amazing Goop Silicone 24 to 72 hours 3800 psi -40°F to 150°F
TechnicaldataBondstrength
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HOTMELTEPOXYCYANOACRYLATEMETHACRYLATE
Adhesive Comparison Chart »
THIS CHART WAS TAKEN FROM
PLEXUS® GUIDE TO BONDING.*
Advantages Limitations
»» Moderately priced
»» Good gap-filling capabilities
»» Rigid to flexible bonds available
»» Versatile formulations
»» Fast setting
»» Usually low strength
»» Poor gap cure
»» Poor creep resistance
»» Many must be applied to both surfaces
»» Poor temperature, moisture, and solvent resistance
»» Attack many plastics
»» Flammable
»» Environmentally unfriendly
»» Usually low priced
»» Good gap filling capabilities
»» High strength: can be filled with metals
»» Wide range of formulations
»» Versatile
»» Good temperature and solvent resistance
»» Adhesives thin during curing cycles
»» Two component mixing and measuring required
»» Exact proportions needed for optimal strength
»» Slow fixturing
»» Short pot life creates waste
»» Special equipment needed to weigh, mix and dispense
»» Rapid cure at room temperature
»» Single component adhesive
»» Excellent adhesion to rubber
»» Good adhesion to metal
»» High Tensile strength
»» No mixing required
»» Indefinite pot life
»» Dispense easily from package
»» Higher priced
»» Limited gap cure
»» Low solvent resistance
»» Low temperature resistance
»» Bonds skin
»» Poor impact and peel resistance
»» No water, chemical or environmental resitance
»» Moderately priced
»» Good gap fill
»» Excellent impact resistance and flexibility
»» Excellent peel and shear strengths
»» Substrate versatility
»» Medium/fast cure
»» Tolerant of dirty surfaces
»» Can be dispensed from most packages
»» Good flexibility at low temperatures
»» Some odor problems
»» Flammable
