Optically Clear Epoxy
Encapsulating & Potting Compound
8321C Technical Data Sheet
8321C
Description
The 8321C Optically Clear Epoxy, Encapsulating and Potting Compound, is an electronic grade, optically
clear epoxy. It cures at room temperature or by heat curing.
It provides very strong electrical insulation and protects against static discharges, shocks, vibrations,
mechanical impacts, environmental humidity, salt water, and many harsh chemicals.
Applications & Usages
The 8321C epoxy is used predominantly to pot or encapsulate, optical devices, light emitting diodes
(LED), and other light emitters or sensors that require maximum light transmissions. As well, it is often
used to allow easy visual inspection of components in potted electronic assemblies. The cured epoxy
improves reliability, operational range, and lengthens the life of electrical and electronic parts.
Its primary applications are in the automobile; marine; aerospace and aviation; communication,
instrumentation; medical equipment and devices; and industrial control equipment industries.
Benefits
Water clear transparency
Strong water and chemical resistance
to brine, acids, bases, and aliphatic hydrocarbons
3A:1B mix ratio
Long 2 to 3 hour working time
suitable for large production runs
Good protection of electronics against
corrosion, fungus, thermal shock, physical impact, and
static
Curing & Work Schedule
a
Properties
Working Life
b
Shelf Life
Full Cure (at 25 °C [77 °F])
Full Cure (at 80 °C [176 °F])
Storage Temperature
of Unmixed Parts
Value
2 to 3 hour
≥3 year
4 day
2 hour
16 to 27 °C
[60 to 80 °F]
Temperature Service Range
Properties
Constant Service Temp.
Maximum Withstand
Temperature
c
Value
-30 °C to 140 °C
[-22 to 284 °F]
200 °C [392 °F]
a) Cure and life values 100 g and room
temperature unless stated otherwise.
b) A 10 °C increase can decreases the pot
life by half.
c) The maximum withstand or service
temperature can be maintained for short
periods of time only.
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Rev. Date: 02 April 2012 / Ver. 1.01
Optically Clear Epoxy
Encapsulating & Potting Compound
8321C Technical Data Sheet
8321C
Principal Components
Name
Part A: Bis-A Epoxide Resin
Dibutyl Phthalate
Oxirane, [(2-methylphenoxy)methyl]-
Part B: Curing Polyamide
CAS Number
25068-38-6
84-74-2
2210-79-9
9046-10-0
Properties of Cured 8321C
Physical Properties
Color
Density (at 26 °C)
Hardness
Lap Shear Strength
Compression Strength
Flexural Strength
Outgasing (Total Mass Loss)
Total Reflectance for
350–700 nm & 0.25” thick sample
Electric Properties
Breakdown Voltage @ 3.53 mm
Dielectric Strength
Breakdown Voltage @3.175 mm [1/8”]
Dielectric Strength
Volume Resistivity
Surface Resistivity
b
Dielectric Dissipation & Constant
Dissipation & Constant@60
Hz
Dissipation & Constant@1
kHz
Dissipation & Constant@10
kHz
Dissipation & Constant@100
kHz
Dissipation & Constant@1
MHz
Thermal Properties
CTE
c
prior T
g
CTE
c
after T
g
Glass Transition Temperature (T
g
)
Method
Visual
(Shore D durometer)
ASTM D 1002
ASTM D 695
ASTM D 790
ASTM E 595
ASTM E 595
Value
a
Optically Clear
1.153 g/cm
3
76D to 78D
4.1 N/mm
2
91.6 N/mm
2
85.3 N/mm
2
7.62%
10%
[590 lb/in
2
]
[13,300 lb/in
2
]
[871 lb/in
2
]
Method
ASTM D 149
"
Reference fit
c
"
ASTM D 257
"
ASTM
ASTM
ASTM
ASTM
ASTM
D
D
D
D
D
150-98
150-98
150-98
150-98
150-98
Value
60.6 kV
436 V/mil [17.2
57.5 kV
460 V/mil [18.1
2 x 10
16
Ωcm
>1 x 10
17
Ω
dissipation, D
0.012
0.011
0.014
0.017
0.019
Value
83.0 ppm/°C
236 ppm/°C
41 °C [106 °F]
kV/mm]
kV/mm]
constant, k’
3.37
3.33
3.27
3.19
3.13
Method
ASTM E 831
ASTM E 831
ASTM D 3418
Note:
Specifications are for epoxy samples cured at 80 °C for 2 hours, with additional curing time at room
temperature for optimal results. For most tests, samples were conditioned at 23 °C and 50% RH.
a) N/mm
2
= mPa; lb/in
2
= psi;
c) To allow comparison between products, the Tautschter equation was fitted to 5 experimental dielectric
strengths and extrapolated to a standard reference thickness of 1/8” (3.175 mm).
b) The surface (sheet) resistivity unit is commonly referred to as “Ohm per square”
c) Coefficient of Thermal Expansion (CTE) units are in ppm/°C = in/in/°C × 10
-6
= unit/unit/°C × 10
-6
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Optically Clear Epoxy
Encapsulating & Potting Compound
8321C Technical Data Sheet
8321C
Properties of Uncured 8321C
Physical Property
Color
Viscosity at 25 °C [77 °F]
a
Density
Mix Ratio by volume (A:B)
Mix Ratio by weight (A:B)
Solids Content (w/w)
Mixture (3A:1B)
Optically Clear
260 cP [0.260 Pa·s]
1.09 g/mL
3.0:1.0
3.6:1.0
~92%
Physical Property
Color
Viscosity at 25°C [77 °F]
a
Density
Flash Point
Odor
Part A
Optically Clear
900 cP [0.900 Pa·s]
1.140 g/mL
95 °C [203 °F]
Mild
Part B
Optically Clear
10 cP [0.010 Pa·s]
0.946 g/mL
124 °C [255 °F]
Amine like
a) Brookfield viscometer at 30 RPM with spindle LV4 for Part A and LV1 for Part B
Compatibility
Adhesion—As
seen in the substrate adhesion table, the 8321C epoxy adheres to most materials found on
printed circuit assemblies; however, it is not compatible with contaminants like water, oil, and greasy flux
residues that may affect adhesion. If contamination is present, clean the printed circuit assembly with
electronic cleaner such as MG Chemicals 4050 Safety Wash, 406B Superwash, or 824 Isopropyl Alcohol.
Substrate Adhesion in Decreasing Order
Physical Properties
Aluminum
Steel
Fiberglass
Wood
Glass
Polycarbonate
Acrylic
Polypropylene
a
a) Does not bond to polypropylene
Adhesion
Stronger
Weaker
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Optically Clear Epoxy
Encapsulating & Potting Compound
8321C Technical Data Sheet
8321C
Storage
Store between 16 and 27 °C [60 and 80 °F] in dry area away from sunlight. Prolonged storage or storage
at or near freezing temperatures can result in crystallization. If crystallization occurs, reconstitute the
component to its original state by temporarily warming it to 50 to 60 °C [122 to 140 °F]. To ensure full
homogeneity, stir thoroughly the warm component, reincorporating all settled material. Re-secure
container lid and let cool down before use.
Health and Safety
Please see the 8321C
Material Safety Data Sheet
(MSDS) parts A and B for more details on
transportation, storage, handling and other security guidelines.
Part A
HMIS RATING
HEALTH:
FLAMMABILITY:
PHYSICAL HAZARD:
PERSONAL PROTECTION:
2
1
0
NFPA CODES
1
2
0
Part B
HMIS RATING
HEALTH:
FLAMMABILITY:
PHYSICAL HAZARD:
PERSONAL PROTECTION:
Health and Safety:
The 8321C parts can ignite if the liquid is heated and exposed to flames or sparks.
Wear safety glasses or goggles and disposable polyvinyl chloride, neoprene, or nitrile gloves while
handling liquids. Part B in particular causes skin burns and may cause sensitization if exposed over a long
period of time. The epoxy is black and will not wash off once cured: wear protective work clothing. Wash
hands thoroughly after use or if skin contact occurs. Do not ingest.
While the product has low volatility and moderate odor, use in well-ventilated area.
The cured epoxy resin presents no known hazard.
3
1
0
NFPA CODES
1
3
0
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Rev. Date: 02 April 2012 / Ver. 1.01
Optically Clear Epoxy
Encapsulating & Potting Compound
8321C Technical Data Sheet
8321C
Application Instructions
Follow the procedure below for best results. If you have little or no experience with the 8321C epoxy,
please follow the long instructions instead. The short instructions provided here are not suitable for first
time users.
To prepare 3:1 (A:B) epoxy mixture
1. Carefully scrape any settled material in the
Part A
container; and stir and fold material until
homogenous.
2. Carefully crape any settled material in the
Part B
container; and stir and fold material until
homogenous.
3. Measure
three
parts by volume of the pre-stirred
A,
and pour in the mixing container.
4. Measure
one
part by volume of the pre-stirred
B,
and slowly pour in the mixing container while
stirring.
5. Put in a vacuum chamber, bring to 25 Hg/in pressure, and wait for 2 minutes to de-air.
—OR—
Let sit for 30 minutes to de-air.
6. If bubbles are present at top, use the mixing paddle to gently break them.
7. Pour mixture into the mold or container containing the components to be encapsulated.
To room temperature cure the 8321C epoxy
Let stand for 4 days.
To heat cure the 8321C epoxy
Put in oven at 80 °C [176 °F] for 2 hours.
A
TTENTION
!
Due to exothermic reaction, heat cure temperatures should be at least 25% below the maximum
temperature tolerated by the most fragile PCB component. For larger potting blocks, reduce heat cure
temperature by greater margins.
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