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Einsatz optimierter Glasfaser-verstärkter PP-Produkte,Ingenieurtechnische Zielstellungen und Anforderungen an
UL-Standards
Thomas Mecklenburg;
Basell Polyolefine GmbH, 65926 Frankfurt
Underwriters Laboratories (UL) ist in den USA die führende Organisation, die die Sicherheit von kommerziellen Elektrogeräten im Haushalt und Büro prüft und zertifiziert. Auch dafür eingesetzte sog. „recognized components“ wie Kunststoffe unterliegen der Überwachung durch UL.
Für Kunststoffmaterialien, die aufgrund der Anwendungen in Langzeitkontakt mit Heisswasser und Detergentien stehen (z.B. bei Waschmaschinen und Geschirrspülern)
wurden von UL Standards mit Langzeit-Detergentienprüfungen entwickelt, wobei die
mechanischen Kennwerte (Zugfestigkeiten, Schlagzähigkeiten) nach der Prüfung noch
mindestens 50% der Ausgangswerteaufweisen müssen.
Bild 1: US washing machine complying with UL 2157
Insbesondere für Glasfaser-verstärkte PP-Produkte ergibt sich aus den UL Standards eineSelektion in für Anwendungen mit Langzeit-Heisswasser- und Detergentien-Kontaktgeeignete (a) und weniger geeignete Produkte (b):a) Dabei zeigen geeignete Produkte, die oft nur mittlere Zugfestigkeiten und Schlag-
Zähigkeiten aufweisen, im Heisswasserkontakt einen relativ geringen prozentualen Abfallder mechanischen Kennwerte. Die UL-Anforderungen (UL 2157) z.B. für den Einsatz von Laugenbottichen von Waschmaschinen werden damit problemlos erfüllt.
b) Durch eine Optimierung des Kopplungs-Systems können die mechanischen Kennwerte von GF-verstärkten PP-Produkten um bis zu 40% gesteigert werden. In Kontakt mitHeisswasser ist jedoch teilweise ein prozentual deutlich stärkerer Abfall zu beobachten,was den Einsatz in UL geprüften Waschmaschinen und Geschirrspülern limitiert.
Diese Situation ist für die Konstruktion entsprechender Bauteile aus GF-verstärkten PP-Produkten unbefriedigend und definiert das Entwicklungsziel, die Heisswasser-Beständigkeitoptimierter, hochsteifer und schlagzäher Glasfaser-verstärkter PP-Produkte zu verbessern, um sicher den UL Anforderungen zu genügen. Nicht eindeutig identifiziert ist u.a. der mikros-kopische Mechanismus, der den steilen Abfalls insbesondere der Zähigkeit in teilweise nur 24h Heisswasserlagerung verursacht.
Dr.Thomas Mecklenburg Basell Polyolefine GmbH / FrankfurtJuni 2003
EEinsatzinsatz optimierteroptimierter
GlasfaserGlasfaser--verstärkter PPverstärkter PP--Produkte,Produkte,
ingenieurtechnische Zielstellungen undingenieurtechnische Zielstellungen und
Anforderungen an Anforderungen an ULUL--StandardsStandards
((UUnderwritersnderwriters LLaboratories)aboratories)
orHow UL affects
product development / optimization and business
Thomas Mecklenburg / 062003
Subject
Glass fiber reinforced PP products for electrical appliances
(for household and similar use) which comply with UL requirements
Example for applications of reinforced PP products:
Different washing machine constructions (tubs )
Thomas Mecklenburg / 062003
Content
• UL background and marks
• Qualifying end products and plastic materials at UL
• UL standards
• Requirements / test program for plastic materials
• Mineral filled PP products (immersion tests)
• Glass fiber reinforced PP products (typical properties / immersion)
• Application and development targets
• Glass fiber sizing and interphase
• Conclusion
Thomas Mecklenburg / 062003
UL’s (Underwriters Laboratories) Background
Independent, not for profit product-safety testing and
certification organization in the USA and a leading provider of
product conformity assessment in the world.
Established in 1894
In 2002:
• UL evaluated 106,942 products and 18,750 typs of products
• There were 64.000+ manufacturers producing UL certified products
• There are 127 UL inspection centers located in 65 countries, and inspecting UL
customers in 96 countries (555,222 follow-up visits at 5,414 registered facilities
on the world in 2002)
There are 886 UL Testing Standards covering a wide range of products
Thomas Mecklenburg / 062003
The UL Marks (for end products and recognized components)
• The UL mark on a product (End product or Components)
means that the complete product has been tested by UL and
meets UL safety requirements and then undergoes periodic
checks (Follow Up Services) to ensure it continues to comply
with UL requirements.
Typical certified products could be electrical appliances such
as white goods, small appliances, power tools etc. for household
and similar use.
• Plastic Materials are Recognized Components
• But the use of Recognized Components in an end product does
not mean the end product will be UL LISTED
Thomas Mecklenburg / 062003
Qualifying a new End Product at UL
For qualifying a new End Product where electrical, fire, or
mechanical hazards could be present UL judges the safety of the
product based on
– Construction: mechanical assembly, internal wiring, electrical and thermal insulation,
over-current protection, thermal cut-off, switches, grounding, etc.
– Performance: strength of enclosure, stability, leakage current, dielectric voltage-
withstand, abnormal operation, exposure to moisture, exposure to chemicals, flammability,
etc.
– Manufacturing and Production Tests
– Use and care and installation / Instruction Manuals.
Thomas Mecklenburg / 062003
Why UL listing of plastic materials ?
The UL listing of plastic materials as recognized
components including compliance with UL standards is
one of the major requirements from global End
Product (electrical appliances) producers.
The use of recognized plastic materials for
End Products helps reduce test work, time and
costs for the producers (customers of Basell).
The UL listing of plastic materials is a competitive
advantage.
Thomas Mecklenburg / 062003
Qualifying a new Plastic Material as
Recognized Component ( UL Standards )
• To qualify Plastic Materials as a Recognized Component the producer /
requestor submits materials to UL for testing under UL Standards
UL 94 Flammability (HB and V rating)
UL 746A Short Term Properties
Electrical and Ignition Properties, Mechanical Properties, Thermal
Properties, Dimensional Changes, Chemical Resistance,
Identification Testing ( IR, DSC, TGA )
UL 746B Long Term Heat Aging
RTI (Temperature / survive 100.000 hours without failure)
UL 746C Use in Electrical Equipment Evaluations
Special UL standards / requirements depending from the
application and use - Immersion testing for example(see list of Household and Similar Electrical Appliances)
Thomas Mecklenburg / 062003
UL Standards / End products must comply with
• UL 45 Portable Power Tools
• UL 82 Electric Gardening Appliances
• UL 197 Commercial Electric Cooking Appliances
• UL 268 Smoke detectors for Fire Protective Signaling Systems
• UL 416 Refrigerated Medical Equipment
• UL 484 Room Air Conditioners
• UL 497 A, B, C Protectors for Communication Circuits
• UL 499 Electrical Heating Appliances
• UL 507 Electric Fans
• UL 563 Ice Makers
• UL 696 Electric Toys
• UL 745-1 thru 37 Portable Electric Tools*@
• UL 826 Household Electric Clocks
• UL 859 Household Electrical Personal Grooming Appliances
• UL 867 Electrostatic Air Cleaners
• UL 875 Electric Dry Bath Heaters
Thomas Mecklenburg / 062003
UL Standards / End products must comply with
• UL 923 Microwave Cooking Appliances
• UL 961 Electric Hobby and Sports Equipment
• UL 985 Household Fire Warning System Units
• UL 998 Humidifiers*
• UL 1017 Vacuum cleaners, Blower Cleaners*
• UL 1026 Electric Household Cooking and Food Appliances
• UL 1082 Household Electric Coffee Makers and Brewing Applic.
• UL 1086 Household Trash Compactors
• UL 1240 Electric Commercial Cloths-Drying Equipment
• UL 1431 Personal Hygiene and Health Care Appliances
• UL 1447 Electric Lawn Mowers
• UL 1448 Electric Hedge Trimmers
• UL 1459 Telephone Equipment
• UL 1647 Motor-Operated Massage and Exercise Machines
• UL 1727 Commercial Electric Personal Grooming Appliances
Thomas Mecklenburg / 062003
UL Standards / End products must comply with
• UL 250/471 Household Commercial Refrigerators and Freezers*
• UL 2158 Electric Clothes Dryer*
• UL 749 Household Dishwashers*
• UL 2157 Electric Cloth Washing Machines and Extractors*
• 60335-1 Safety of Household and Similar Electrical Appliances
* UL/ Canadian Standards Association (CSA) Harmonized Standards
@ UL/International Electrotechnical Commission (IEC) Harmonized Standards
Thomas Mecklenburg / 062003
UL requirements on plastic materials (UL 2157 and 749)
Required test program for plastic materialsexposed to detergent and bleach solutions typically used in wash water tubs
and other fluid containing parts in laundry and dishwashing equipment.
Specimens in natural / unpigmented color are to be tested for
tensile strength
(in accordance with ASTM D 638, using Type I specimens) and
tensile impact energy(in accordance with ASTM D 1822, using Type S specimens).
Upon comparison to unconditioned specimens,
50% retention of properties is required for all
exposures.
Thomas Mecklenburg / 062003
Test program for plastic materials (UL 2157 and 749)
The conditions are as follows:
UL 2157 / Laundry Machine requirements1. for a part subjected to wash water, 30 specimens (10 for each period)
shall be immersed for 30, 60, and 138 days at 82°C in 2.5% (by weight),
aqueous laundry detergent solution
2 for a part subjected to laundry bleach, 10 specimens shall be immersed
for 1000 h at 100°C in 100% bleach; and
3. The laundry detergent and bleach solution shall consist of 50 g of non-concentrated
powdered laundry detergent and 100 ml of bleach per litre of water.
UL 749 / Dishwasher requirements
4. immersion of 10 specimens each for 30, 60, and 138 days at 82°C in 2.5%,
by mass, aqueous dishwasher detergent solution for a part subjected to wash
water; or
5. immersion of 10 specimens for 1000 h at 100°C in 100% rinse agent solution
for a part of a rinse agent dispenser.
Thomas Mecklenburg / 062003
Tensile properties of a mineral filled productover 138 days at 82°C (test conditions: UL 2157 / 749)
20% mineral filled heco product
for washing machine tubs and other white good interior parts
10
15
20
25
30
35
0 10 20 30 40 50 60 70 80 90 100 110 120 130 138
Immersion period (days)
Te
ns
ile
str
en
gth
(M
Pa
)
Thomas Mecklenburg / 062003
Impact strength of a mineral filled productover 138 days at 82°C (test conditions: UL 2157 / 749)
40% mineral filled PP homo product
for different white goods interior parts
0
1
2
3
4
5
6
0 10 20 30 40 50 60 70 80 90 100 110 120 130 138
Immersion period (days)
No
tch
ed
Ch
arp
y i
mp
ac
t(2
3°C
) k
J/m
²
Thomas Mecklenburg / 062003
Mineral filled PP products for dish washer interior parts (UL 749)
Thomas Mecklenburg / 062003
Typical effects / properties for PP productsunder UL immersion conditions
• Mineral filled Hostacom* products based on PP Homopolymers
or Heco‘s comply with the UL standards 2157 and 749.
Mostly there is not a significant change of the tensile and
impact properties over the testing period, usually on a low level of
mechanical properties.
• But Glass fiber reinforced PP products (chemically coupled)
with a much higher level of mechanical performance often exhibit
a typical more or less rapid decrease of the tensile and impact
strength within only few days in aqueous laundry and dishwasher
detergent solutions but also in demineralized hot water.
* Hostacom = Tradename of Basell for compounded PP products
Thomas Mecklenburg / 062003
Notched Charpy impact strength (ISO 179/1eA) of different 30% Glass fiber reinforced Hostacom products over 30 days hot water immersion
Typical decrease of the impact strength
of different commercial Hostacom products
(30% GF reinforced) / hot water (demin. Water at 95°C)
2
4
6
8
10
12
14
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Immersion period (days)
Notc
hed
Char
py
impac
t (2
3°C
) kJ
/m²
UL 2157 approved
Thomas Mecklenburg / 062003
Front loading washing machine tub made of a glass fiber reinforced Hostacom grade (UL 2157)
Thomas Mecklenburg / 062003
US / European washing machine which comply with UL 2157
Thomas Mecklenburg / 062003
GF reinforced PP productsApplication and development targets
Glass fiber reinforced PP products in principle can be
developed / optimized with 2 different targets:
Comply with the UL standards 2157 and 749 with an only
slight relative decrease of the tensile and impact strength over
138 days immersion.Example: 30% glass fiber reinforced homo PP product:
Tensile strength at break (ISO 527-2): initial value in the range of 70 - 80 MPa.
Unnotched Charpy impact strength (ISO 179/1eU at 23°C): < 35 kJ/m².
Product at the lower end of the mechanical performance.
Optimized (high) mechanical properties (tensile strength,
tensile modulus and impact strength) by matching the system
consisting of the glass fiber sizing (chopped strands), coupling
agent, PP matrix and other additives.Example: 30% glass fiber reinforced homo PP product:
Tensile strength at break (ISO 527-2) up to ~ 110 MPa.
Unnotched Charpy impact strength (ISO 179/1eU at 23°C) up to ~ 60
kJ/m². Product with the highest feasible performance.
Thomas Mecklenburg / 062003
GF reinforced PP products / targets
Target 1 products exhibit up to 40% lower (!)
mechanical properties (initial values) vs. target 2
products,
but target 1 products fully comply with the UL
standards 2157 and 749.
and target 2 products not always do comply with the
UL standards 2157 and 749 because of < 50 %
retention especially of the impact strength after
138 days laundry or dishwasher detergent
solution immersion.
(See diagrams for 2 different 20% GF reinforced PP products
with 2 different targets)
Thomas Mecklenburg / 062003
Tensile properties of different 20% Glass fiber reinforced PPmaterials over 40 days hot water immersion
Hot water test ( demin. water at 95°C )
of 2 different 20% GF reinforced Hostacom products
with identical glass fibers
40
45
50
55
60
65
70
75
80
85
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40Immersion period (days)
Te
ns
ile
str
en
gth
at
bre
ak
(MP
a)
HC U HC C (A208571) HC C (1M12AE20)
Tensile strength of mineral filled products < 40 MPa
UL 2157 approved
does also comply with UL 2157
Thomas Mecklenburg / 062003
Charpy impact strength (ISO 179/1eU) of diff. 20% Glass fiberreinforced PP materials over 40 days hot water immersion
Hot water test ( demin. water at 95°C )
of 2 different 20% GF reinforced Hostacom products
with identical glass fibers
15
20
25
30
35
40
45
50
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40Immersion period (days)
Ch
arp
y i
mp
ac
t u
nn
otc
he
d,
23
°C (
kJ
/m²)
HC U HC C (A208571) HC C (1M12AE20)
Range of < 50% retention of the impact strength
for HC U (initial value: 46,3 kJ/m² / 50% value: 23,2 kJ/m²)
UL 2157 approved
at the limit
Thomas Mecklenburg / 062003
Glass fiber - PP matrix interphaseHow to optimize the hot water resistance
Hot water / steam and hot watery detergent solutions impair the
glass fiber - PP matrix interface, but the mechanism of the fast
water migration into the specimens and wetting of the interface is
not well understood and identified.
One key parameter for the formulation of GF reinforced PP
products and the interaction with the coupling agents is the
glass fiber sizing (different from every glass fiber
manufacturer) which is including
silanes, binding resins, lubricants, antistats etc.
(see diagrams for different glass fibers from different suppliers but
identical Hostacom formulations)
Thomas Mecklenburg / 062003
Tensile properties of a 30% Glass fiber reinforced PP material withdiff. commercial glass fibers over 40 days hot water immersion
50
55
60
65
70
75
80
85
90
95
100
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
Immersion period (days)
Tensile
strength
at bre
ak (M
Pa)
Hostacom G3 (identical formulation)
but with different commercial glass fibers
(different manufacturer / different sizings)
Thomas Mecklenburg / 062003
Charpy impact strength (ISO 179/1eU) of a 30% Glass fiber reinforced PPmaterial with diff. commercial glass fibers over 40 days hot water immersion
0
10
20
30
40
50
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 33 35 37 39
Immersion period (days)
Unnotc
hed C
harp
y im
pact str
ength
(kJ/m
²)
Hostacom G3 (identical formulation)
but with different commercial glass fibers
(different manufacturer / different sizings)
Initial value 48,5
final value ~ 24
Initial value 42,6
final value ~ 14
Products don‘t comply with UL 2157 / 749 !
Thomas Mecklenburg / 062003
Glass fiber functionalizing (sizing) and coupling
Sizing
(functional silane)
Coupling
Thomas Mecklenburg / 062003
Glass fiber - PP matrix interphaseHow to optimize the hot water resistance
Other parameters for the formulation of GF reinforced PP products
which affect the efficiency of the coupling and the water resistance
are
the coupling agent (functionalized / grafted PP) with the
degree of grafting, type of grafting, base resin (homo, heco, random), MW
and MFR of the resin etc.
and additives which can interact with the polar groups of the
glass fiber sizing and of the coupling agentsuch as polar release agents.
Thomas Mecklenburg / 062003
Conclusion
But in spite of all improvements of GF reinforced products and
independant from the initial values of the mechanical properties (tensile
strength and impact strength) for a defined glass fiber reinforced grade
(with a defined glass fiber concentration and a defined PP matrix) the
mechanical properties seem approaching asymptotically to a lowest limit
over the long term hot water / deteregent immersion.
Hot water immersion (95°C)
20% GF reinforced Hostacom products
40
60
80
0 30 60 90 120Immersion period (days)
Te
ns
ile
str
en
gth
at
bre
ak
(M
Pa
)
This lowest limit is that
mechanical property of a
not coupled GF reinforced
PP product in practice.
Thomas Mecklenburg / 062003
Target for GF reinforced PP products
In principle the current situation of glass fiber reinforced PP products for
applications exposed to hot water and watery detergent solutions is less
satisfying. For CAE constructions engineers would like to use mechanically
optimized products to reduce the wall thickness of injection moulded parts
(saving of weight, costs, cycle time etc.). But over a longer immersion
period currently the properties could be maintained only for less optimized
products.
0
20
40
60
80
0 30 60 90 120Immersion period hot water 95°C ( days)
Te
ns
ile
str
en
gth
at
bre
ak
(M
Pa
)
20% mineral filled homo PP
20% glass fiber reinforced homo PPs
Thomas Mecklenburg / 062003
US clothes dryer which comply with UL 2158
HotHot airair doesn‘tdoesn‘t affectaffect thethe mechanicalmechanical
propertiesproperties of GF of GF reinforcedreinforced PPPP productsproducts
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