FREQUENTLY ASKED EPOXY AND URETHANE
RELATED QUESTIONS
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www.crosslinktech.com
Formulated Epoxy and Polyurethane
compounds for all applications. Custom cast Transformer Bushings, Insulators and mechanical
components.
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Epoxy and Polyurethane compounds can be packaged to suit the
handling requirements. Generally speaking, the following are the widely
available standard packaging methods:
- Bulk packages in 55gal (200litre), 5gal (20litre), 1gal
(4litre), 1quart (1Litre) containers. Depending on the product, these
containers hold standard weights regardless of the mix ratio.
- Pre-weighed units. The container sizes and the weight per
container are selected based on the mix ratio of the epoxy or urethane system. This type of
packaging allows the user to empty the contents of one container, usually the
hardener, into the other and obtain the correct mix ratio without weighing.
This type of packaging tends to be slightly more expensive but are highly
suitable for field applications where it is inconvenient to weigh each
component separately.
- Cartridges are limited to epoxy or urethane materials with convenient exact
mix ratios. They are typically 1:1, 2:1 and 4:1. Cartridges require a suitable
dispense gun and static mix heads that thoroughly mix the products during the
dispense cycle. This is a highly desirable method of packaging for convenient
field applications such as repair.
- Plastic bags equipped with a barrier between epoxy resin and
hardener are also utilized in field applications. They are also limited to
products with convenient mix ratios. The resin and hardener are mixed by
removing the barrier and kneading until thoroughly mixed.
Quantity:
Crosslink Technology Inc. has very few off-the-shelf products for immediate
delivery. Everything is made to order to provide fresh epoxy and urethane materials to our
customers. Although we can accommodate lower volume purchases, at times we are
limited by the minimum batch sizes allowed for our mixing equipment. Our
minimum order size for epoxy and urethane products is 3 gallons (14 liters) of resin plus the required amount of
hardener for 2 component systems and 5 gallons (20 liters) of material for
single component products.
Minimum Invoice
Amount ($):
The minimum amount is
$ 200.00 per invoice. Different products may be combined (subject to the minimum
batch sizes stated above) to achieve the minimum invoice amount.
Pre-pay and
Charge Shipments ($50.00):
Unless agreed
otherwise, shipments are made FOB our plant and we ask our
customers to specify the carrier of their choice. In some cases we are asked to
ship the "best way" and invoice the charges incurred for the shipment. There is
a $ 50.00 service charge applicable to make the necessary
arrangements and process the additional paperwork.
Rush shipments
by Courier ($50.00):
One must keep in mind
that some epoxy and urethane products are considered "Dangerous Goods" for
transportation purposes. This being the case, only certain couriers are licensed
to transport dangerous goods thereby limiting the choices available.
In addition, most
couriers have the policy to invoice the shipper if the customer's account with
the selected courier is delinquent. This requires Crosslink Technology Inc. to
confirm the account status of the client before making the shipment. There is a
$ 50.00 service charge to cover the costs associated with this
service.
Credit Card
Purchases:
Customers requesting
payment by credit card will receive an authorization form from us with a request
to provide the necessary information and a signature for our files. This form
can be faxed or e-mailed back to us. The signed form authorizes Crosslink
Technology Inc. to debit all charges (including shipping charges) associated
with the particular shipment to the credit card provided.
There are no extra charges associated with this service.
In order to provide fresh materials to our customers, epoxy
and urethane products
are manufactured to order. Except for emergencies, our standard lead time is
2 weeks from receipt of order. In the case of regular repeat orders, our
production is planned to accommodate early releases and emergencies that arise
from time to time.
As a customer service, whenever possible, we trace long
distance shipments to solve any problems that may arise during transit, insuring
the timely delivery of our products.
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There are certain single component epoxy and urethane products that can be cured
at room temperature. These products depend on one of the following to cure:
- The evaporation of a volatile component within the
formulation.
- The application on Ultra Violet energy (UV cure).
- The presence of moisture in the surrounding air (Relative
Humidity).
These materials are usually limited to a maximum thickness in
their application.
Depending on the chemistry employed, some epoxy and urethane products are more
tolerant to slight variations in mix ratio than others. Generally speaking, ± 2%
by weight accuracy should yield satisfactory results in most cases. Since the
mix ratio is determined by product chemistry, based on the number of desired
reactive sights contained in each component, it is best to be as close as
possible to the stated ratio in order to obtain the optimum cured properties.
A component that is partially or totally exposed to the
elements during its service life must contain epoxy or urethane products that are suitable for
outdoor use. On the other hand, components that operate outdoors but are covered
from direct exposure to the elements need not be manufactured using outdoor
materials.
In epoxy and polyurethane formulations Cycloaliphatic resins
are considered most suited to continuous outdoor operation.
All Epoxy and Polyurethane compounds are good
general purpose adhesives. Since the overall bond strength is dependent on the
type of substrates to be bonded, the surface preparation and the thickness of
the bond line, it is best to use products that have been formulated specifically
for adhesive applications.
It is very difficult to remove cured epoxy or polyurethane
without damaging the encapsulated components. In certain cases however there are
ways to remove at least part of the encapsulant.
Click here to read more...
There are ways to reduce the viscosity of a mix but all the
methods involve some trade-off either in the handling or the cured properties of
the epoxy or urethane material. Click here to read
more...
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How to extend the pot life
There are 3 basic methods to extend the pot life
of mixed material. Since most Epoxy and Polyurethane compounds generate heat (exotherm)
during the reaction controlling the heat will have an effect on pot life.....
Click here to read more....
How to prevent changes due to encapsulation in the output of electronic
circuits.
Epoxy and Polyurethane compounds are widely used to
encapsulate electronic circuits. Depending on the type of components contained
in the circuit and the performance requirements for the finished components, it
is critical to select the appropriate formulation. The type of fillers,
pigments, thermal conductivity, the electrical properties, the amount of
shrinkage during cure and adhesion to containers can all effect the output of an
encapsulated circuit......
Click here to read more....
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What are the
advantages of Epoxies vs. Polyurethanes?
Epoxy advantages
are physical strength, high temperature resistance and excellent adhesion to
most substrates. Urethane advantages are low temperature performance, low
exotherm and faster cure speeds.
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How do I speed up or slow
down the reaction?
The cure
reaction can be made quicker by introducing mild warming to the mixed epoxy or
urethane system
prior to pouring, or pouring the mixture into a preheated unit or mould. The
reaction can be slowed down by reducing the temperature of the mixed product or
by mixing up a smaller batch size.
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How can I reduce the
trapped air in my casting?
A mould or part
should first be designed to allow air to escape easily when mixed epoxy or
urethane is poured into the part. If this is not feasible, mixed product may be
brushed or vacuumed into intricate areas prior to topping up with the remaining
mixture. If vacuum or brushing is not possible, warming the mixed product or
preheating the part will help reduce the viscosity of the mixed liquid, making
it easier for the trapped air to escape.
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How can I shorten the gel time or development of green strength time?
Introducing
mild warming to the mixed system prior to pouring, or pouring the mixture into a
preheated unit or mould will shorten both gel time and development of green
strength time.
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How important is mix ratio
accuracy?
Epoxy and
Urethane chemistry is a crosslinking reaction between resin molecules and
hardener molecules. The stated mix ratio produces enough reactive sites in both
the resin and hardener to crosslink the system for optimum performance. Adding
less or more hardener will compromise the performance of the cured product. Two
mixes, one low in hardener, and the other high in hardener, will produce a cured
product with excess un-reacted resin or excess un-reacted hardener
respectively. The physical performance of these two castings would be
compromised due to incomplete crosslinking.
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How to incorporate fillers
to reduce cost?
Fillers need to be
incorporated by mixing under high shear with vacuum applied. This is required
to remove trapped air and break up agglomerations to properly wet out filler
with the resin. If filler is not properly wet out and air is trapped in the
mix, physical performance of the cured system will be compromised. If fillers
are to be incorporated on the shop floor, it is best to add them to the resin
that is already mixed with the hardener in the correct ratio. Using this method
will eliminate the necessity of having to re-calculate the mix ratio based on
the extra fillers.
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Will adding more
hardener speed up the reaction?
In some cases
adding more hardener will speed up the reaction because more reactive hardener
sites are available for the resin to react with. This may result in a shorter
time to achieve gel but the excess un-reacted hardener remaining after gel
point, will reduce the integrity of the final cured product. Mild warming is
recommended to speed up the reaction, not altering the mix ratio.
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How can I eliminate
sticky/tacky surfaces?
Sticky/tacky
surfaces also known as blush on a cured epoxy is due to moisture in the
atmosphere reacting with uncured hardener at the surface. The blush is cosmetic
and does not affect the performance of the cured epoxy below the surface. Some
epoxy hardeners are more prone to blush than others. Castings that are thin and
require a long time to gel at room temperature are more prone to blush. This
blush may not be apparent when the same system is cast thicker. The thicker
casting cures faster and as a result, less time is available for surface blush
to develop. The best way to eliminate blush when casting thin sections is to
warm the substrate or warm the mixed epoxy prior to application.
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What are the
advantages of Polyurethanes over Epoxies?
Polyurethanes have a much wider hardness range from 5 Shore A
up to 85 Shore D, whereas the useful hardness range for epoxies would be from
40D to 90D. Urethanes tend to be less brittle and have higher tensile elongation
than other materials with similar hardness.
Polyurethanes also posses "elastomeric memory" which means
that they can withstand considerable deflection (in tension or compression)
without permanent deformation. The abrasion resistance of Urethanes is far
superior to Epoxies.
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What
colours are available in Epoxy and Polyurethane compounds?
Most primary colours are available as well as
most standard or traditional pigments. Specialty colours or requests for colour
matching would have to be considered on an individual basis.
The batch to batch shade consistency can be
problematic with certain light colours such as light blue. This is especially
true with products that contain fillers. The reason for this is that the minor
amount of impurities, inherent in the ingredients of a given formulation, will
have a major impact on the pigments. A slight shade difference in the colour of
the fillers will necessitate an adjustment to the pigment in order to achieve
the required colour. This is not the case with most primary colours.
Elevated post cure temperatures will have less
impact on solid primary colours. All systems that require post cure at elevated
temperatures will develop a yellow tinge due to the applied heat. This slight
yellow tinge is not as visible with primary pigments.
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How to stage
(step) cure Epoxy and Polyurethane compounds
When post-curing Epoxy and Polyurethane
compounds, the post-cure temperature should be a minimum of 100C ( 180F)
higher than the intended service temperature of the finished component. For
large castings or products designed for high service temperatures, a stepped or
staged post-cure (gradual increase in temperature) may be necessary. For best
results, the part should remain in the mould until all the curing steps are
completed. Smaller components can be removed from the mould and stage cured
separately in a suitable oven. It is usual to increase the post-cure oven
temperature in increments of 200C, allowing the part to stabilize at
each temperature, until 100C above the intended service temperature
is reached. Stage curing allows the material to fully crosslink and, at the same
time, will minimize any residual stresses that are conducive to crack formation.
If the finished component contains embedded metal
inserts, such as in the case of transformer bushings, the final post cure
temperature should be above the HDT (heat deflection temperature) of the
encapsulating material. This will minimize any residual stresses that are
conducive to cracking.
The parts should not be allowed to cool
between the post-cure steps since any cooling would be equivalent to thermal
cycling an uncured material.
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Can I improve
the cured properties of an off-ratio mix?
With Epoxy and Polyurethane compounds, the mix
ratio is perhaps the single most important processing parameter in terms of
obtaining the desired performance parameters. Since the mix ratio is based on
material chemistry, any deviation will result in degraded or different cured
properties. There are "variable ratio" Epoxy systems available but each
variation will result in different cured properties.
Parts made to stringent performance criteria,
inadvertently encapsulated with off-ratio product, should be discarded. In
cases where there is less of an importance placed on the encapsulant in the
service environment, post-curing for an extended period of time may improve the
properties of an off-ratio mix sufficiently to save the finished components. It
must be realized however, that post-curing an off-ratio mix will not restore the
desired properties and will only work if the mix ratio variation is relatively
minor. Please contact our technical staff for information regarding the
possibilities.
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What are the main material considerations when purchasing automatic dispense
equipment?
Automated mix, dispense equipment is highly desirable
especially in high volume production environments. There are some very important
basic items to be considered, both from the material and the equipment
reliability stand point before purchasing such equipment. There are many
prominent manufacturers who are able to supply high quality reliable equipment
to dispense all types of compounds. Some of the manufacturers are listed on this
web site on our
Useful Links page.
Click to read more....
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How do I
compare the dielectric strength of different materials?
The two major considerations when comparing the published
dielectric strength of different materials are a) the thickness of the test
specimen and b) the test temperature. The test results can be
drastically different if these two conditions are not identical for the products
being compared.
Click here to read more...
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What are the
major considerations for casting resins?
There are a number of considerations for selecting the best
material to provide a solid, bubble free, crack free, functional and
cosmetically pleasing casting. The key material properties are:
-
Mixed viscosity
-
Reactivity
-
Exotherm
-
Shrinkage
-
Thermal stability
-
Thermal conductivity
-
Thermal shock
capabilities
-
Thermal expansion
properties
The above properties are especially important when casting
electrical and electronic components.
Click to read more....
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Significant amounts of time can be saved by prior
preparation, not to mention the possible incomplete or erroneous test results
that can cause having to repeat the whole process over again to assure product
suitability. The object of the exercise is to approve the product in the
current or planned processing environment. This will ensure that the final
transition will be smooth and trouble free.
Click here to read more.....
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What is the typical shelf life of Epoxy and Polyurethane compounds?
The shelf
life of Epoxy and Polyurethane compounds depend on the type of formulation
involved. In general, products may be classified into the following main
categories:
- Unfilled 2 component products.
- Filled 2 component products.
- Unfilled single component materials.
- Filled single component materials.
-
Unfilled 2 component materials
The shelf life of these products is
typically 1 year from the date of manufacture provided that they are stored in
sealed containers. It is advisable that any containers which have been opened
are purged with Nitrogen and re-sealed for further storage. The usually
recommended storage temperature is 220C (720F).
-
Filled 2 Component products
The shelf life is typically six
months to 1 year from the date of manufacture. The main concern is filler
settling that can only be corrected by re-mixing in the appropriate equipment
which is normally unavailable at the customer's premises. The shelf life can be
maximized by periodically inverting the containers (typically once per week) to
keep settle to a minimum. The usually recommended storage temperature is 220C
(720F).
-
Unfilled Single Component
materials There are no general
rules that can be applied to these type of formulations. These products must
be stored according to the manufacturer's instructions. Many of these
materials begin the curing process as soon as they are made and must be
shipped and stored under refrigeration. Some will crystallize if frozen while
others can be stored for a reasonable time at room temperature.
-
Filled Single Component products
Same as the conditions stated above for the unfilled versions. Filler settling
is usually not a problem under refrigerated storage conditions since the
amount of settling will be less due to the higher viscosity induced by the
lower temperatures. Containers stored at room temperature should be inverted
once per week to minimize filler settling.
Some products are moisture sensitive and should be purged with
Nitrogen before re-sealing the containers for further storage.
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The short answer is yes. We provide prototype services, to a
reasonable extent, free of charge. In fact, we prefer to be part of the
prototype work because it allows us to make suggestions in material selection
and processing improvements.
Confidentiality/Non-disclosure Agreements
We re
willing to take part in and accept any reasonable confidentiality or
non-disclosure agreements with our customers. Although it is a matter of
integrity in conducting our business, we realize that certain projects require
formal agreements to identify precisely what is considered confidential and how
the information is to be protected.
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Shipping and delivery conditions
All materials supplied by Crosslink Technology Inc. are made
fresh to order.
In general, most products do not need any special
precautions for shipping. There are however some formulations, such as single
component epoxies which should not be over heated or frozen. Certain low
viscosity, two component materials may begin to settle when subjected to
excessive heat during transportation.
We track all longer distance shipments to detect
and solve problems that may cause transportation delays. This is a normal part
of our service to insure on time delivery of our products and at the same time,
minimize transit time.
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Why do I have
surface bubbles in the cured material?
Urethanes:
As a general rule,
Polyurethane compounds are moisture sensitive and will react with moisture in
the air or with moisture in the substrate they come in contact with during cure.
Depending on the chemistry, some products actually require the presence of
moisture in the air to cure while others require the evaporation of a solvent
carrier to solidify. Urethanes may be formulated as 2 component or single
component systems.
Surface bubbles are
most likely caused by one or more of the following:
- High ambient
temperature causing the product to skin over and preventing proper solvent
evaporation below.
- Material reacting
with moisture introduced during mixing component A with component B (2 component
systems)
- Excessive moisture
present in either the substrate or in the air during application.
Fix:
- Do not mix
violently. De-air the mix under vacuum before use.
- Apply at the
recommended relative humidity.
- Do not apply on very
humid days.
- Apply at the
recommended temperature.
- Once the
bubbles have appeared, let the material fully cure as recommended, sand the
surface and re-apply.
Epoxies
Epoxies are less prone
to moisture pick up during cure. Some hardener components however are moisture
sensitive and require care in storage and handling. Storage is recommended in
containers purged with Nitrogen and all epoxies should be de-aired under vacuum
for best results.
Surface bubbles are
most likely caused by one or more of the following:
- Excessive air
introduced during mixing.
- Improper surface
tension preventing bubbles from self-releasing.
- Index of thixotrophy
too high.
Fix:
- Mix slowly to
avoid air entrapment.
- Warm the mix if
possible to reduce the viscosity.
- Spray surface with
mould release (usually works)
- Pour slowly in one
corner and let the material rise pushing the air ahead of it.
- Select a different
product for the application.
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What do I do if my
shipment arrives damaged?
The carrier, by
accepting the shipment, agrees and certifies that the goods are in order at the
time they are picked up. The carrier assumes responsibility and is insured to
deliver the shipment intact to its destination. Depending on who is paying the
freight (who hired the carrier), claims for damaged goods must be made based on
the following:
-
Reject the damaged
shipment or at least make a note on the shipping documents that the goods were
delivered damaged.
-
If the freight
was pre-paid by the supplier:
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The goods belong to
the shipper until delivered to the final destination. Only the shipper may make
a claim for damages.
-
Determine what, if anything, is
rendered unusable.
-
Contact the shipper
(supplier) with the particulars.
-
Provide copies of
documentation - including that the shipment was damaged.
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Provide a list of the
components to be replaced to the supplier.
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If the freight
was paid for by the company receiving the goods:
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The goods
belong to the destination customer as soon as they are loaded on the truck. Only
the destination customer can make a claim for damages. (the shipper can't)
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Determine what, if anything, is
rendered unusable.
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Make a claim with the carrier for the
cost of the unusable goods.
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Always contact the supplier before
using any material from a damaged shipment since the product may be contaminated
and may not perform as expected.
The basic
rule is that only the person paying for the freight can claim for damaged
shipments.
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What is the
standard lead time for Bushings and Insulators?
Crosslink Technology
Inc. maintains stock of components that meet the most common electrical
requirements. The lead time to ship these components ranges form one day
to 3 days. Specialty components, or if the parts are not in stock, the lead time
to ship is 3 - 4 weeks from receipt of order.
Specialty components
that require tooling alterations will take longer depending on complexity. Since
we are also formulators of Epoxy and Polyurethane compounds, we often are able
to produce epoxy tooling to accommodate shorter production runs.
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Minimum order requirements
Our
minimum is $ 200.00 per order. The price per component, however, will vary based
on the quantity. The higher the quantity the lower the price per part.
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Custom
components
Crosslink
Technology Inc. manufactures many different types of components to customer
design. Most of these components are considered "Proprietary" and are not
referenced on our web site.
Custom
components involve specialty tooling and can be electrical or mechanical
devices. Our formulating capabilities and knowledge of various applications
allows us to select the correct compounds to meet specific performance criteria.
Depending on the component being considered, our ability to develop Epoxy and
Polyurethane tooling can also provide cost savings.
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Standard Quality Control
All
components manufactured by Crosslink Technology Inc. are subject to quality
control. Components from all production batches are sampled and thoroughly
tested for the accuracy of dimensions and critical physical properties. Incoming
raw materials are subject to approval prior to use in production.
The
quality control system is certified under the latest ISO 9001:2000
requirements and incorporates all customer specified critical criteria in
addition to our standard quality procedures.
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UL®
and CSA® Recognized Products
Crosslink Technology
Inc. has several products that are recognized by the Underwriters Laboratories
Inc. as well as the Canadian Standards Association (CSA). A summary of these
products are found at
UL Rated Products
on this web site.
Products are approved
under certain specific categories and the details can be viewed by clicking the
following links:
Crosslink UL Listed Plastic Components
Crosslink UL Listed Insulation Systems
In addition to the
formally recognized products, Crosslink Technology Inc. has a number of
formulations that meet specific UL® and CSA® requirements
but to date have not been formally approved. Depending on the application at
hand, these products are likely to pass if formal approval is necessary. Please
contact us for details.
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It is
extremely important to carefully consider the test conditions under which
the data was generated. Due to the lack of uniform standards in the formulating
industry, there is no guarantee that the materials being compared were
tested under identical conditions to obtain the published properties.
Furthermore, some test results are totally meaningless unless the test
conditions are also stated. For example; the dielectric strength is expressed in
volts/mil over a specified specimen thickness. This figure is meaningless unless
the thickness of the specimen is known because various thicknesses will yield
different figures for the same product.
The following are the most common published properties where
care must be exercised when comparing different materials:
| Property |
Should also indicate: |
| Mixed Viscosity |
Temperature |
| Pot Life |
Temperature |
| Elongation % |
Temperature or ASTM D 638 |
| Hardness |
Temperature or ASTM D 2240 |
| Linear Shrinkage % |
in/in or ASTM D 2566 |
| Flammability |
Specimen Thickness |
| Dielectric Strength |
Specimen Thickness or ASTM D 149 |
| Dielectric Constant |
Frequency, Temperature, Test method ( ASTM D 150) |
| Dissipation Factor |
Frequency, Temperature, Test method ( ASTM D 150) |
| Volume Resistivity |
Test Specimen, Temperature, Test Method ( ASTM D 257) |
The above properties will be different under alternate
test conditions. It is best to contact the material supplier and obtain test
data under the desired conditions to compare different products.
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Information required to successfully recommend a material for a project.
The more thorough and complete the information provided the
more likely it is that the correct material will be recommended for the process
at hand. First and foremost, it is important to provide a general description of
what is to be done, how it is to be done and the desired end result sought.
Beyond this, it is wise to provide as many known details as possible in order to
assist in narrowing the search. The following are some of the more important
details to speed material selection:
|
Item: |
Note: |
| Desired material type |
Epoxy or Polyurethane - Single Component or 2 Component. |
| Processing conditions |
Manual or Automated (i.e. dispense equipment). |
| Processing temperature |
The maximum temperature available or allowed. |
| Amount of material used at a time |
The desired amount of product to be mixed or used at a time. |
| Desired working time |
How long the mixed material has to stay pourable. |
| Desired cure conditions |
Cure time and maximum cure temperature available. |
| Performance requirements |
The desired performance requirements for the final part. |
| Final test parameters |
The testing to determine the part suitability (i.e. thermal
cycling etc.) |
| Embedded components if any |
The type of components embedded in the casting, if any. |
| Special requirements if known |
Hardness, flammability, electrical properties etc. |
| Part operating conditions |
i.e. indoor, outdoor, temperature, humidity, solvent
resistance etc.) |
| Potential volume |
Total volume or volume per part and the number of planned
parts. |
| |
Influences the type of product, reaction speed and cost
factors. |
Our aim is to recommend the correct material in the very
first instance. Based on our experience, we will also provide suggestions and
recommendations toward improving the planned process and how to avoid possible
complications that could arise.
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Why is Crosslink Technology Inc. different from all other formulators and
Manufacturers?
Crosslink Technology Inc. prides itself in providing the best
products to increase customer profit. We do not always have the lowest cost
materials but we believe that our products along with our expertise in
processing Epoxy and Polyurethane compounds will result in maximum profit for
our customers. Our products, services and knowledge base are all designed to
yield our customers the highest quality components at the lowest costs possible.
Our services include:
- A complete review of the intended process and component
performance parameters.
- Recommendations regarding possible processing equipment.
- Suggestions on component design.
- Developing new or modifying existing products to provide
the best of all worlds in the production environment.
- Focused development effort and assistance with trial for
fast completion of projects.
- Quick response with samples.
- Confidential prototype services within our capabilities.
- Customer specific quality control in manufacturing.
- On time delivery of orders.
- Ongoing and continued customer support.
We believe that we are better than our competition in all the
above listed categories and our track record proves it.
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Geographical areas covered.
Crosslink Technology Inc. is located in Toronto,
Ontario, Canada. This is our head office and main manufacturing plant. We are
actively looking for "technically competent" sales agents and distributors in
various countries in the world. For the present time, all our off-shore sales
are handled from head office and are successfully exporting our products to the
following countries:
- USA
- Mexico
- Australia
- Germany
- Hungary
- Peru
- India
Despite the distances involved, through careful
planning and selection of freight forwarders, we have been able to retain our
100% delivery ratings with our remote customers. The "Order Status" section of
our web site allows our customers to conveniently track their orders and place
repeat orders with ease.
We believe that, with careful planning, we can
ship our product just about anywhere in the world and our area of coverage will
continually increase as we locate and develop "technically competent" local
distributors.
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Other components cast
with epoxy or urethane
We are able to cast just about any type of component utilizing
our own formulations. We have, at any given time, several non-electrical
components being manufactured in our plant. Since we are also epoxy and
polyurethane formulators, we are able to develop the correct material for the
application at hand. We can easily make prototype tooling utilizing one of our
epoxy or polyurethane tooling products. We often manufacture prototype castings
and subsequently supply our customers with the correct formulation and
instructions on how best to manufacture their component in their facilities.
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Corona
(Partial Discharge) in encapsulated components
Other than the usual mechanical causes, such as sharp edges or
insufficient distances between the components, partial discharge may be the
result of improper handling during the encapsulation process. The vapor pressure
of the epoxy or urethane components could also play a role in causing corona.
By definition, corona occurs when a gaseous substance is
ionized and becomes conductive. This occurs frequently if there are air bubbles
or vapors are trapped in the casting. It can also occur immediately at the
interface between insulating layers with drastically different dielectric
properties.
It is very important to remove as much air from the epoxy or
urethane mixture before the encapsulation process. At the same time, it is also
important to control the vacuum level while de-airing the mix so as not to
"strip" vapors that could be trapped in the form of bubbles in the casting as
the material solidifies. It is best to first thoroughly de-air the mix on its
own, pour the material into the mould and de-air again all the wile controlling
the amount of vacuum to minimize vaporizing.
Further to this, since the location of any trapped bubbles in
relation to energized components will have a major impact on partial discharge
levels, the part design is critical. Smooth, rounded surfaces instead of sharp
undercuts are preferable to aid with the de-airing process. The application of
air pressure to the surface of the casting during the gellation process will
compress the trapped gases and significantly raise the voltage required to
ionize them thereby reducing the amount of corona in the casting.
Some processes, where the products are encapsulated under
vacuum, employ a dielectric gas which is allowed to enter the vacuum chamber
instead of air as the vacuum level is adjusted. In this way, any remaining air
is mixed with the dielectric gas raising its ionization potential.
For best results:
-
Eliminate sharp corners, undercuts and cavities.
-
Select a product with the correct vapor pressure.
-
De-air the mix
before pouring.
-
Do not use excessive
vacuum to severely strip the ingredients.
-
Pour and de-air again.
-
Apply pressure during
gellation.
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Non-sag epoxy systems are said to be thixotropic. Certain
applications require the epoxy or urethane compound not to run off the surfaces
being coated. An extreme example of a thixotropic compound would be shaving
cream. No matter where it is applied, it will not run off the surface.
Thixotropic materials are greatly effected by shearing forces.
High shear, such as high speed mixing or high pressure dispensing, will usually
destroy thixotropic properties.
The degree of thixotrophy is indicated by the thixotropic
index, usually shown on technical data sheets for materials developed for this
purpose. The higher the index the better the material will cling to a given
surface.
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How to prevent filler settling
Filler settling in epoxy and urethane products is one of the major causes of off ratio
cure problems and insufficient or inconsistent cured properties. Filler settling
in epoxy and urethane compounds will depend on the following:
-
The filler content in the
material.
- The chemistry employed.
- Viscosity.
- The storage temperature.
- The storage container size.
- Transportation conditions.
Settling can be defined as
"hard" or "soft". Hard settle occurs when the fillers compact at the bottom of
the container, forming a hard crust. Soft settle is when some of the fillers
drop to the bottom but the fillers are easily mixed back into the resin without
too much effort. Hard settle can only be eliminated by re-mixing with commercial
equipment.
The
following simple precautions will help to reduce or eliminate settling during
storage:
- Order product in smaller containers.
- Order more frequently to reduce storage time.
- Store products at room temperature or slightly below room temperature.
- Periodically invert the containers in storage. (once per week for 5gal (20
Liter) pails).
- Store heated material
under slow continuous agitation.
- Use a drum roller to keep the fillers moving within the product.
- Ask the supplier to
incorporate anti-settling agents.
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Minimum
order quantity for cast Epoxy and Urethane components.
The minimum order quantity for off the shelf
standard components is only limited by our minimum invoice amount of $ 250.00
per invoice.
Custom cast specialty components usually involve
development work, mould design, mould construction etc. Although these tasks can
be accomplished rather quickly, at times using epoxy tooling, there is usually a
fair amount of effort required to manufacture the custom components. The minimum
order size will depend on the complexity of the part, the processing time
involved and the delivery requirements. Each custom project is quoted
separately.
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Why does the dielectric strength (volts/mil) drop as the thickness of the Epoxy
or urethane is increased?
The dielectric strength, which is the measure of the ability
of a cured epoxy or polyurethane to withstand voltage, is directly related to
the amount of impurities contained within the specimen being tested. As a rule,
the thicker the specimen under test, the lower the volts/mil results will be
because the thicker sample will contain more impurities per unit volume.
Epoxy and urethane products containing fillers will exhibit
lower volts/mil values because additional impurities are contained in the
fillers. Similarly, unfilled epoxies contain less impurities and will yield
higher volts/mil figures.
The typical values for epoxies range from 425 volts per mil
(0.125 in. thickness) to 1800 volts per mil (0.001 in. thickness).
It must be considered that the volume and the amount of
impurities within do not follow a direct relationship. For example, doubling the
volume of the epoxy will not double the amount of impurities contained within
the specimen. Although the volts per mil will slightly decrease over thicker
specimens of cured epoxy, the overall withstand voltage will increase
considerably. Overall, increasing the material thickness will allow for higher
operating voltages.
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How do
Epoxy and Urethane compounds compare in cured properties?
Although in many applications Epoxy and Urethane compounds can
be used interchangeably, they each have specific unique characteristics which
make each type of product more suitable in certain applications.
The following table provides comparative cured properties for
each type of chemistry;
|
PROPERTY |
EPOXY |
URETHANE |
| Adhesion |
Excellent |
Very Good |
| Abrasion Resistance |
Good |
Excellent |
| Chemical Resistance |
Excellent |
Average |
| Component Stress |
Poor |
Good |
| Cost |
Variable |
Variable |
| CTE (Coefficient of thermal expansion) |
Low |
Medium |
| Elongation |
Low |
High |
| Exotherm (heat generated during cure) |
Higher |
Medium |
| Handling |
Good |
Good |
| High Temperature Operation |
Good |
Poor |
| Impact Resistance |
Good |
Excellent |
| Low Temperature Operation |
Average |
Good |
| Moisture Sensitivity (Prior to cure) |
Low |
High |
| Thin Film Cure |
Slow |
Variable |
| Tensile Strength |
High |
Medium |
| Tear Strength |
N/A |
Good |
| Thermal Cycling ability |
Very Good |
Very Good |
| |
|
|
The above general comparisons are based on materials with
similar filler contents. As always, material selection must be based on the
requirements of the application under consideration. For example; a roller used
in the printing industry would probably be better cast with polyurethane and a
component required to operate under high temperature/humidity conditions would
fare better cast in epoxy.
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Which is better to use,
an Epoxy or a Urethane?
It depends on the application. Epoxies excel in certain
applications while urethanes are better in others. Epoxies tend to be better
performers outdoors while urethanes have much better abrasion resistance and
elongation properties. In terms of processing and safety precautions, there are
some slight differences. The general hygiene recommendations are basically the
same for both product types but urethanes are significantly more moisture
sensitive and therefore require extra precautions in storage and dispensing,
especially in high humidity environments. All containers, components to be
embedded and substrates to be adhered to must be free of moisture for best
performance.
With the exception of a few specific types of hardeners, epoxy
systems are relatively impervious to moisture. As a rule epoxy system are better
for outdoor use and are more widely acceptable in electrical and high voltage
electronic applications.
Because each application is unique, the type of chemistry
recommended will be dependent on the properties required by the end use. In some
cases either a urethane or an epoxy might be suitable.
Please contact us for specific recommendations.
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Hand mixing 2 component Epoxy
systems..
Equipment Required:
-
A pair of
disposable Nitrile gloves.
-
Safety glasses.
-
A clean plastic
or glass container sufficiently large enough to hold the total amount of
desired mix. (Waxed paper cups are not recommended.)
-
Steel or plastic
stir stick. (Wooden stir stick are not recommended because the moisture
contained in the wood may contaminate some products and interfere with the
curing process)
-
An accurate
weigh scale. (Gram scales are best.)
-
Technical data
sheet for the product being used.
-
Safety data
sheet for the product being used.
Caution:
Do not use postage scales or cooking scales as
they may not have the required accuracy to obtain the correct weights. Use epoxy
products in a well ventilated area and wear gloves while working to prevent skin
contact.
Recommended Procedure
-
Read and
observe all safety instructions indicated on the safety data sheet for the
product.
-
Look up the “pot
life” specification of the mixed material on the Technical Data Sheet to
estimate the maximum amount of epoxy that should be mixed at a time. The
shorter the “pot life” the smaller the amount that may be mixed at a time.
Mixing excessive amounts of material can result in dangerous heat generated by
the reaction between the resin and hardener.
-
Prepare all work
surfaces and/or tooling for the application. (Do not forget to apply mould
release if the finished part is to be removed from a tool after casting)
-
Place the
container on the scale and tare.
-
Thoroughly mix
the epoxy resin and epoxy hardener in their original containers to eliminate
any separation and disperse any settled fillers.(1) (2 – 3 minutes
of mixing, while scraping the sides and bottom of the container is
recommended.)
-
Accurately weigh the required amount of epoxy resin, according to
the mix ratio, into the container.(3)
-
Tare the scale again.
-
Add the required amount of epoxy hardener, according to the mix
ratio, on top of the resin.(3)
-
Thoroughly
mix the resin/hardener together; scraping the sides of the container to make
certain that all the hardener is thoroughly and evenly dispersed in the resin.
Mix carefully to minimize air entrapment due to turbulence in the material.
Try to angle the edge of the stir stick rather than using the flat surface
which creates the most turbulence.
-
If possible,
let the mix stand for a few minutes to release the surface bubbles.
-
Pour or use
the material as intended.
-
Follow the
curing instructions on the Technical Data Sheet.(2)
Notes:
1.
Some
highly filled materials may have to be slightly warmed to allow for thorough
mixing. Do not heat excessively and allow both resin and hardener to cool to the
recommended processing temperature before mixing the components together.
2.
Do
not subject the epoxy to mechanical stress until it is fully cured. Do not
subject the epoxy to significant temperature changes prior to full cure. (This
would be like thermal cycling the uncured epoxy and could cause cracking).
3.
Be
careful when using percentages in calculating mix ratios. It is easy to make a
mistake as shown in the following example:
Assume that you are using an epoxy system with a mix ratio of
100:25 on the technical data sheet and you need 125 grams or oz of mixed
material for you part. One of the most common mistakes made is to assume that
the total mix will contain 25% hardener (25/100=0.25). In fact the total mix
will be 125 grams and the % hardener required is 25/125=0.20 or 20% of the mix.
Always base % calculations on the total mix required.
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How to dispose of unused epoxy or urethane
products
Just about every State in the United States and every Province in
Canada regulate the disposal of chemicals including epoxy and urethane
compounds. In liquid form, disposal must be carried out by properly licensed
companies.
Some major cities in North America have designated
environmental days during which they accept spent batteries, unused paint and
similar products for disposal. This would be a suitable way to dispose of small
amounts liquid epoxy and urethane materials.
An alternate method of disposal would be to solidify the
materials and dispose of them as solid waste. This requires some work but by far
is the safest method. Solidified epoxy and urethane products are inert if the
reaction between the resin and hardener is completed according to the
manufacturer's instructions. This process must include completing any post cure
instructions if specified by the manufacturer.
Exercise caution when reacting pure resins and hardeners.
Some epoxy and urethane compounds can generate excessive amounts of heat when
reacted in large volumes. Single component epoxies, requiring heat to solidify,
can also generate dangerously high temperatures. Some products can self ignite
if not handled properly.
Take all recommended safety precautions and contact the
supplier of the product for instructions before proceeding.
It is best to react small amounts of product at a time in
heat resistant, steel containers, taking care not to be near any combustible
materials.
Do not dispose liquids epoxy or urethane materials in
household or industrial garbage. Liquids will seep out of regular containers no
matter how well sealed.
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How important is accurate post cure temperature for Epoxy and Urethane products?
Some Epoxy and Urethane products require post cure in order to
develop full strength. There is usually a temperature and a specific length of
time specified by the manufacturer for the post cure. These compounds are
usually in a "brittle state" just prior to the post cure process and will crack
if subjected to mechanical shock or extreme temperature differences.
The post cure temperatures are usually specified on the technical
data sheet covering the epoxy or urethane compound. The parts must reach this
temperature to complete the chemical reaction and develop full properties.
Some ovens are not uniform in temperature due to "zoning".
This means that some epoxy or urethane parts, in one area of the post cure oven,
will be subjected to lower temperatures while in other areas of the oven, the
temperature will be higher than specified or what is indicated on the
controller. These temperature differences could account for various problems in
the cured properties of an epoxy or urethane component.
It is advisable to periodically check the actual temperature
of the components being post cured to insure that every part in the oven reaches
the required temperature. Temperature controllers are only accurate near the
location of the thermocouple so do not assume that the whole oven is at a
given temperature just because the controller is set to that temperature.
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Why does Epoxy or Urethane separate from the walls of the container?
This is a problem frequently encountered potting or encapsulating
various components into containers. Most often the problem is caused by one of
the following:
Surface contaminants left on the container walls. Frequently there is mould
release or greasy residue left on the surfaces from the container manufacturing
process causing the epoxy or urethane to adhere to the contaminant covering the
walls of the container.
The container has oxidized and the epoxy or urethane has adhered to the oxide
layer which is loosely attached to the sides.
Excessively high cure temperature. Epoxy and urethane products shrink during
cure. As a rule, the faster the cure the higher the shrinkage and the product
pulls away from the walls of the container.
Improper mix ratio causing improper cure.
Insufficient elongation. Elongation is obtained by properly formulating the
epoxy or urethane compound to meet the application requirements.
A large difference in the coefficient of thermal expansion between the epoxy and
the container. The greater the difference the more likely that separation will
occur with changes in temperature such as thermal cycling.
the container is manufactured using materials which are difficult to adhere to.
High gloss surfaces an some stainless steel materials are examples of this.
The above represent some of the more common causes of separation.
In some cases, the container is manufactured from materials that are very hard
to bond to. In certain cases annealing or abrading the bond surfaces may help
while in others the application of a suitable primer or a layer of softer
material may solve the problem.
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What is the difference between a Thermoset and a Thermoplastic Polymer?
To describe the difference, one can use the simple analogy of
reshaping wax and cooking an egg.
Wax melts with the application of heat and can be poured into
moulds and allowed to harden into various shapes. To change the shape of the
wax, all one has to do is re-melt it an | 
