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 Ausgangswerte aufweisen müssen. Bild 1: US washing machine complying with UL 2157 Insbesondere für Glasfaser-verstärkte PP-Produkte ergibt sich aus den UL Standards eine Selektion in für Anwendungen mit Langzeit-Heisswasser- und Detergentien-Kontakt geeignete (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 Abfall der 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 mit Heisswasser 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-Beständigkeit optimierter, hochsteifer und schlagzäher Glasfaser-verstärkter PP-Produkte zu verbessern, um sicher den UL Anforderungen zu genügen. Nicht eindeutig identifiziert ist u.a. der mikroskopische Mechanismus, der den steilen Abfalls insbesondere der Zähigkeit in teilweise nur 24h Heisswasserlagerung verursacht.
Dr.Thomas Mecklenburg Juni 2003 Basell Polyolefine GmbH / Frankfurt Einsatz optimierter Glasfaser-verstärkter PP-Produkte, Produkte, ingenieurtechnische Zielstellungen und Anforderungen an UL-Standards (Underwriters Laboratories) or How UL affects product development / optimization and business
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 )
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
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
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
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 voltagewithstand, abnormal operation, exposure to moisture, exposure to chemicals, flammability, etc. Manufacturing and Production Tests Use and care and installation / Instruction Manuals.
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.
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)
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
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
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
UL requirements on plastic materials (UL 2157 and 749) Required test program for plastic materials exposed 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.
Test program for plastic materials (UL 2157 and 749) The conditions are as follows: UL 2157 / Laundry Machine requirements 1. 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.
Tensile properties of a mineral filled product over 138 days at 82 C (test conditions: UL 2157 / 749) 35 Tensile strength (MPa) 30 25 20 15 20% mineral filled heco product for washing machine tubs and other white good interior parts 10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 138 Immersion period (days)
Impact strength of a mineral filled product over 138 days at 82 C (test conditions: UL 2157 / 749) 6 Notched Charpy impact (23 C) kj/m² 5 4 3 2 1 40% mineral filled PP homo product for different white goods interior parts 0 0 10 20 30 40 50 60 70 80 90 100 110 120 130 138 Immersion period (days)
Mineral filled PP products for dish washer interior parts (UL 749)
Typical effects / properties for PP products under 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
Notched Charpy impact strength (ISO 179/1eA) of different 30% Glass fiber reinforced Hostacom products over 30 days hot water immersion Notched Charpy impact (23 C) kj/m² 14 12 10 8 6 4 Typical decrease of the impact strength of different commercial Hostacom products (30% GF reinforced) / hot water (demin. Water at 95 C) UL 2157 approved 2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Immersion period (days)
Front loading washing machine tub made of a glass fiber reinforced Hostacom grade (UL 2157)
US / European washing machine which comply with UL 2157
GF reinforced PP products Application 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. kj/m². Unnotched Charpy impact strength (ISO 179/1eU at 23 C) up to ~ 60 Product with the highest feasible performance.
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)
Tensile properties of different 20% Glass fiber reinforced PP materials over 40 days hot water immersion Tensile strength at break (MPa) 85 80 75 70 65 60 55 50 45 40 Hot water test ( demin. water at 95 C ) of 2 different 20% GF reinforced Hostacom products with identical glass fibers UL 2157 approved does also comply with UL 2157 Tensile strength of mineral filled products < 40 MPa 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 Immersion period (days) HC U HC C (A208571) HC C (1M12AE20)
Charpy impact strength (ISO 179/1eU) of diff. 20% Glass fiber reinforced PP materials over 40 days hot water immersion 50 Charpy impact unnotched, 23 C (kj/m²) 45 40 35 30 25 Hot water test ( demin. water at 95 C ) of 2 different 20% GF reinforced Hostacom products with identical glass fibers at the limit UL 2157 approved 20 15 Range of < 50% retention of the impact strength for HC U (initial value: 46,3 kj/m² / 50% value: 23,2 kj/m²) 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 Immersion period (days) HC U HC C (A208571) HC C (1M12AE20)
Glass fiber - PP matrix interphase How 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)
Tensile properties of a 30% Glass fiber reinforced PP material with diff. commercial glass fibers over 40 days hot water immersion 100 95 Tensile strength at break (MPa) 90 85 80 75 70 65 60 55 50 Hostacom G3 (identical formulation) but with different commercial glass fibers (different manufacturer / different sizings) 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 Immersion period (days)
Charpy impact strength (ISO 179/1eU) of a 30% Glass fiber reinforced PP material with diff. commercial glass fibers over 40 days hot water immersion 50 Unnotched Charpy impact strength (kj/m²) 40 30 20 10 0 Initial value 48,5 final value ~ 24 Initial value 42,6 final value ~ 14 Hostacom G3 (identical formulation) but with different commercial glass fibers (different manufacturer / different sizings) Products don t comply with UL 2157 / 749! 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 33 35 37 39 Immersion period (days)
Glass fiber functionalizing (sizing) and coupling Sizing (functional silane) Coupling
Glass fiber - PP matrix interphase How 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 agent such as polar release agents.
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. 80 Tensile strength at break (MPa) 60 Hot water immersion (95 C) 20% GF reinforced Hostacom products This lowest limit is that mechanical property of a not coupled GF reinforced PP product in practice. 40 0 30 60 90 120 Immersion period (days)
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. Tensile strength at break (MPa) 80 60 40 20 20% glass fiber reinforced homo PPs 20% mineral filled homo PP 0 0 30 60 90 120 Immersion period hot water 95 C ( days)
US clothes dryer which comply with UL 2158 Last picture Hot air doesn t affect the mechanical properties of GF reinforced PP products