The use of Plastics in electrical products continues to grow. What started with circuit boards and transformer bobbins, now includes most enclosures and component bodies. New applications for plastics appear every day. Yet most engineers know little more than to ask for the UL flame rating. To prevent getting “burned” during your compliance evaluations due to improperly specified plastics, it is important to know how to incorporate plastics into electrical products. We will discuss the core plastics requirements, material verification, differences between North American & International plastics standards, and the plastics tests. Perhaps even more importantly, we will discuss application specific plastics tests, how to avoid them, and how to prepare for them when they cannot be avoided. This is a presentation intended for engineers and technicians who are involved with the design and/or compliance verification of products that incorporate plastics.

1. Don’t Get Burned
By
Plastics
© 2008 Educated Design & Development, Inc.

2. Presented by
Bill Bisenius – President, NCE/NCT
billb@productsafeT.com
Educated Design & Development, Inc.
901 Sheldon Dr., Cary, NC
Tel: 919 -469-9434; Fax: 919 -469-5743
919-469- 919-469-
www.productsafeT.com
Product Safety Consulting, Test Equipment &
Training Services
from
People Who Know Product Safety

3. Part A
Plastics
General Compliance Issues

4. General Compliance Goals
AVOID
Non-compliance problems that
n
require re-design & material
changes,
Additional, unanticipated tests
n
PLASTICS = TERRIBLE SURPRISES

5. Plastics & Compliance
It’s all about the
PREPARATION

6. Plastics & Compliance
Plastics is one part of your
product safety compliance work
that can be done almost entirely
on paper before making a
costly mistake

7. “Polymeric Materials”
Thermoplastics: can be resoftened by
n
heating
Thermosets: cures by chemical reaction
n
and cannot be resoftened
Elastomerics: stretches to 2x+ length @
n
room temp; returns to original length

8. Plastics - Key Issues
“Bar Samples” vs. End Product
n
Plastic Mfg vs. Product Mfg
n
Flammability vs. Other Properties
n
Flammability – using rated plastics
n
Other properties – end product tests
n
are frequent

9. Plastics & Compliance
Properly selected plastics for each
application will help you avoid the
need for “plastics” testing

10. Flame Rating System
HB or HBF = Most Flammable
V-2 =
V-1 =
V-0 =
5VA/VB = Least Flammable

11. Part B
Plastics
The Standards

12. Identifying Standards
In what countries will your product
n
be marketed?
What is your end product standard?
n
• Does it contain plastics requirements?
• Does it reference other plastics standards?

13. U.S. Plastics Standards
UL94: Flammability of Plastic
n
• Target = plastics manufacturers
• Testing bar samples for flame rating
: Horizontal & Vertical flame tests

14. U.S. Plastics Standards
UL746 Series: Polymeric Materials
n
• UL746A: Short Term Property Evaluations
• UL746B: Long Term Property Evaluations
• UL746C: Use in Electrical Equip. Evaluations
• UL746D: Fabricated Parts
• UL746E: Laminates, Fibre, PWB Materials

15. U.S. Plastics Standards
UL746A: Short Term Property Evaluations
n
• Physical Properties: Tensile, Impact, Material
Distortion Under Load
• Electrical Properties: High Voltage Dielectric,
CTI, High Voltage Arc Tracking,
• Resistance to Ignition from Electrical Sources:
Hot Wire Ignition, High Current Arc Ignition,
High Voltage Arc Ignition, Glow Wire Test,
• Tests for Polymer identification

16. U.S. Plastics Standards
UL746B: Long Term Property Evaluations
n
• Long-Term thermal aging programs -
Temperature Index rating
• Target = Plastics manufacturers
• NOT something end product manufacturers
want to mess with

17. U.S. Plastics Standards
UL746C: Use in Electrical Equip. Evaluations
n
• Target = End product manufacturers
• Includes flame and “other” property tests
• Flame: 12 mm, 20 mm, 127 mm
• Electrical: CTI, Dielectric, HAI, HWI, GWEPT
• Mechanical: Impact, Crush Resistance, Mold
Stress, Strain Relief, Conduit Connections

18. Inter. Plastics Standards
IEC60695-11 Series: Flame Tests
n
• IEC60695-11-2: 1 KW Flame Test
• IEC60695-11-3: 500 W Flame Test
• IEC60695-11-4: 50 W Flame Test
• IEC60695-11-5: Needle Flame Test

19. Inter. Plastics Standards
IEC60695 Series: Other Properties
n
• IEC60695-2-10/11/12/13: Glow Wire Test
• IEC60695-10-2: Ball Pressure Test
• IEC60695-10-3: Mold Stress Test
• IEC60695-9-1: Flame Spread Test
IEC60112: Tracking Test: CTI, PTI
n

20. Part C
Plastics Tests
U.S. & International

21. Flame Tests - General
Use the proper equipment = many
1)
burner variations for IEC tests,
Use the proper gas supply = critical for
2)
proper flame temperature,
Flame calibration requirements,
3)
Colors and thickness affect results,
4)
Be Safe – don’t underestimate the
5)
potential for disaster

22. Flame Test Set-Up
Flame hood with gas
1)
controls,
Burners,
2)
Gas supply,
3)
Test stand,
4)
Wire gauze, burner
5)
mounts, cotton,
Flame calibration
6)
equipment,

23. Horizontal Burn Testing
HB/HBF Ratings per UL94
20 mm flame height,
n
45° angle flame angle,
n
One, 30 second flame
n
application,
Permitted to burn for
n
limited rate (100 mm)

24. Vertical Burn Testing
V-0, V-1, V-2 per UL94
20 mm flame height,
n
Vertical flame angle,
n
Two, 10 second flame
n
applications,
Very brief period
n
between flame
applications,
Must not drip burning
n
particles that ignite
cotton 300 mm below

25. Vertical Burn Testing
5VA, 5VB per UL94
125 mm flame height, 40
n
mm inner blue cone,
20° flame angle,
n
Five, 5 second flame
n
applications,
5 seconds between flame
n
applications,
Must not drip burning
n
particles that ignite cotton
or make hole in plastic.

26. 12 mm Flame Test
per UL746C & IEC60695-11-5
Needle Flame Test,
n
12 mm flame height,
n
Butane vs. Methane,
n
End product test,
n
Two, 10 second flame
n
applications,
One minute between flame
n
applications,
Sample must not be
n
consumed.

27. 20 mm Flame Test
per UL746C
20 mm flame height,
n
Vertical flame angle,
n
Two, 30 second flame
n
applications,
One minute between
n
flame applications,
Sample must not be
n
consumed.

28. 127 mm Flame Test
per UL746C
127 mm flame height,
n
End product test, 20° flame
n
angle,
Five, 5 second flame
n
applications,
5 seconds between flame
n
applications,
Must not drip burning
n
particles that ignite cotton
or, burn for more than 1
minute after last flame, or
make hole in plastic.

29. Flame Tests - Tips
Air inlet adjustment changes the color of the
n
flame,
Gas pressure adjustment changes the height
n
of the flame,
Air holes closed
1)
Air holes half open
2)
Air holes nearly fully
3)
open
Air holes fully open
4)

30. Flame Tests - Tips
Some plastics will pass higher ratings in
1)
the end product = oxygen limitations,
especially with small products,
Timing is “everything ” = use a helper to
2)
run the stop watch,
Have a GREAT test stand with enough
3)
sturdy clamps to insure nothing moves,
Don’t light your clothes on fire,
4)

31. Dielectric Test
Plastic used as an
n
insulator must be
tested to insure
overvoltage transients
will not damage the
insulation,
Insulation tested
n
between precision
probe tips at 100 g,
Foil wrap enclosures
n
for hipot testing

32. Ball Pressure Test
Ball Pressure Tester
n
evaluates mold
deformation under
elevated temperature,
Performed in oven,
n
Some standards
n
require the Ball
Pressure Test Stand,
UL indicates equivalent
n
to Vicat Softening Test

33. Mold Stress Release Test
Plastic Enclosures
n
tested to insure no mold
stresses will reflow,
Sample put in oven at
n
10°C over max.
temperature on the
material during
temperature testing,
No openings may form
n
that will allow probes to
enter.

34. Glow Wire Test
Glow wire test is an
n
alternative “flame” test,
550 - 960°C element
n
pressed against sample
with 1N force for 30
seconds,
Flame must extinguish
n
within 30 seconds and,
must not ignite tissue
paper below.

35. Tracking Test
Determines the
n
material’s resistance
to surface tracking,
CTI & PTI ratings,
n
Surface tracking can
n
lead to ignition of the
material
Voltage applied with
n
conductive drops

36. Hot Wire Ignition Test
Resistance to ignition
n
from electrically
heated wire,
Intended for insulating
n
materials in contact
with electrically
heated live parts

37. Part D
Designing For Compliance
Using Plastics

38. KEY Question #1
What does your end product standard
require for plastic enclosures, internal
plastics, & circuit boards?
• Does it contain plastics requirements?
• Does it reference other plastics standards?

39. KEY Question #2
Are each of the plastics used in your
product properly flame rated?
• Enclosure Plastics?
• Internal Plastics?
• Printed Circuit Boards?
• At the thickness & color used?

40. KEY Question #3A
Does your application require any
additional properties in any of your
plastics?
• Plastic close to arcing parts?
• Plastic supporting live parts?
• Live parts near plastic enclosure?
• CTI rating needed for traces?
• Outdoor = UV, cold, weather

41. KEY Question #3B
If your application requires additional
properties in some of your plastics, do
you have certified ratings?
• HWI, CTI, HVTR, HAI
No ratings? Time for Special Testing!

42. Plastics – Product Design
Enclosures
n
Decorative Parts
n
Foam Parts
n
Internal Plastics
n
Printed Circuit Boards
n
Insulated Wiring
n

43. Selecting Plastic Materials
Is the material certified?
n
What is the flammability rating at the
n
thickness & color used?
Within temperature ratings of material?
n
Any conductive coatings? Certified for
n
application to this specific material?
Are other physical properties needed?
n (i.e. HWI,
HAI, CTI, etc.)

44. Flammability of Materials
Decorative Parts min. HB
n
Foam Parts min. HBF
n
PWB’s min. V-1
n
Wiring V W-1
n
Internal Plastics min. V-2
n
Plastic Enclosure
n
: products up to 40 lbs min. V-2
: products over 40 lbs min. 5V

45. Design Comments
UL flame ratings are generally accepted
1)
for CSA, IEC, EN (CE), etc.
End product tests can leave you in the
2)
lurch = what if you fail, do you control the
plastic composition?
BEWARE of components that have
3)
plastic bodies and serve as part of the
enclosure.

46. Don’t Get Burned
By Plastics
CONCLUSION

47. William S. Bisenius (Bill)
24+ years of Product Safety experience
n
NCE/NCT
n
BSEE from SJSU (IEEE student chapter President)
n
President/Co-Founder of E.D.& D.
n
Former Engineering Group Leader for UL
n
= ITE, Lab, Lasers, Appliances, Seminars
Develops Product Safety Test Equipment
n
Consultant/Seminar Leader in ITE, Lab,
n
Medical, Lasers, IP Codes, Appliances