Offering High Performance and High Functionality of TPE for Airbag Cover Applications

Transcription

1 Offering High Performance and High Functionality of TPE for Airbag Cover Applications Sumitomo Chemical Co., Ltd. Petrochemicals Research Laboratory Kousuke OHTANI Tatsuo SASSA Airbag devices installed to protect passengers in cars are veiled with a part that is called an airbag cover made of TPE. The impact performance at low temperature and durability to maintain performance after many years, are important requirements for TPE used for airbag covers. Recently in line with an increase in the types of vehicles being equipped with airbags and in installation locations, the demand characteristics required from TPE for airbag cover applications have changed due to differences in the construction and shape of airbags. In this paper, we present the approaches on offering high performance and high functionality of TPE for airbag cover applications with examples of the airbag devices for drivers and for passengers. TPE TPE TPE 3 t 1) PP PE EPDM, EPR TPE 2) TPE PP PE TPE TPE TPE TPE 4 1) TPE Fig. 1 TPE 198 Fig. 2, ), 4) ECU Electric Control Unit 2-

2 Front pillar skin Instrument panel skin Airbag cover (Driver/Passenger/ Side/Curtain) Bonnet cushion Cable jacket Air dam skirt Air duct hose Wire coating Kicking plate Fig. 1 Fig. 2 Door trim skin Center pillar skin Assist grip Armrest Weather stripping Seatbelt buckle Trunk room sheet Mud guard Number plate housing Side molding Fuel tank band Reclining cover Console box skin Applications of Olefinic TPEs for automobile For passenger Installation position of airbags For driver 7) TPE TPE TPE TPE PP PE EPR EPDMTPE TPE Fig. 4 PP EPDM TPE TEM Fig. 3 Product s examples of airbag devices 1μm 3), 5), 6) Cross-linked rubber PP Fig. 4 TEM image of crosslinked-type TPE 2-

3 TPE TPO R- TPO TPE Fig. 5 TPE 8) Fig. 6 VOC Volatile Organic Compounds Fig. 7 Fig. 8TPE Table 1 VOC TPE Fig. 7 TPE Fig. 8 Shore A Hardness Vulcanized rubber Vulcanized-type TPE Fig. 5 Shore D Hardness Soft PVC Non vulcanized-type TPE Stiffness property of Olefinic TPE Flexural Modulus(MPa) Commodity thermoplastics (PP, PE) Izod strength at -45 C(KJ/m 2 ) Fig Heat resistance at 1 C 2 3 Time(hr) Example of heat resistance of TPE Normal Part 2 to 5mm Tear line.5mm agnification of cross-section at tear line portion Tear line Tear line Designing side Steering wheel Airbag cover Cross-section of airbag cover Fig. 6 Example of configuration of tear line 2-

4 12 Light resistance UV weather meter Table 2 Impact properties at low temperature of TPEs Izod strength at -45 C(KJ/m 2 ) Izod( 5 C, notched) HRIT ( 5 C, 5m/sec) Average diameter of rubber particle µm TPE-1 Break Brittle 1.4 TPE-2 Non Break Ductile Time(hr) Fig. 8 Table 1 Example of light resistance of TPE Example of VOC property of TPE TPE-1 EPR particle 1μm Ingredient Condition Sample area Formaldehyde Acetaldehyde Toluene Xylene Ethyl benzene Styrene p-dichlorobenzene Tetradecan mm 2 µg/m 3 4 C 2hrs 8 Less than Q.A.L Less than Q.A.L 12 Less than Q.A.L Less than Q.A.L Not detected Not detected Not detected Quantitative Analysis Limit (Q.A.L) 5 5 TPE-2 Fig. 9 TEM image of TPEs μm ) TPE PP Table 2 Fig. 9 PP EPR 2TPE Fig. High Rate Impact 1: Specimen 2: Holder 3: Impacting probe 4: Load Cell Fig. 3 MAX Speed: m/sec 5: Accelerometer 6: Cooling Chamber 7: Screw Outline drawing of High Rate Impact Tester Tester : HRIT 2-

5 TPE Flow direction Unsteady resin flow at extended thickness and Viscosity increase of melting resin Melting resin Designing surface Cavity ) Fig. 11 Defective transcription Fig. 12 Tear Line Non-grain surface Tear line Estimated outbreak mechanism of glossy tear line Grain surface Gate Fig. 13 Overall image of quasi-airbag cover Tear line thickness =.55mm Normal Thickness = 3mm Appearance defect on tear line 5mm Fig. 14 Magnification of tear line portion Fig. 11 Glossy phenomenon on tear line Tear Line Fig. 12 Fig. 13 Fig. 14 Fig. 15 Fig. 15 Magnification Observation of flow front by short-shot molding 2-

6 Temperature at flow front = 23.4[C] 1.2 PP : EPDM = 4 : 6 (wt%) Tear Line [C] Die swell ratio of TPE ( ) 1.15 Appearance of molded part = Fair Appearance of molded part = Poor Calculation condition: Resin temperature = 22 C, Mold temperature = 4 C, Injection time = 3sec. Fig. 16 Scale(mm) Calculation result by flow analysis Y Z X Mw/Mn of PP in TPE <Measurement condition> Temperature = 2 C, Shear rate = 365 sec 1 Fig. 17 Effect of die swell ratio on inhibiting glossy tear line Fig. 16 Fig. 12 TPE TPE TPE TPE Fig. 17 Fig. 18 PP TPE PPTPE TPE - C 3-C 2 TPE Fig. 19 Temperature- Controlled Barrel Crystallization time (sec. at 13 C) Heater Piston Extruded Sample Fig Fig. 19 D D Sample Capillary Laser Radiation Outline of capillary rheometer PP / EPDM / C 3-C 2 elastomer 36 / 54 / (wt%) Non-C 3-C 2 elastomer Appearance of molded part = Fair PP : EPDM = 4 : 6 (wt%) C 2cnt.(wt%) in C 3-C 2 elastomer Die Swell Ratio = D/D Device for the Measurement of Die Swell Ratio Appearance of molded part = Good Effect of addition of C 3-C 2 elastomer on inhibiting glossy tear line 2-

7 DSC C 3-C 2 TPE PP PP C 3- C 2 C 3-C 2 PP TPE TPE Vibration welding Fig. 2 Instrument panel substrate Airbag cover (TPE) Magnification Airbag cover (TPE) with ribs on the surface attached to the instrument panel substrate Rivet joint Cross-section shape of passenger side in instrument panel PP TPE 11), 12) Fig. 2 TPE 2 TPE TPE PP TPE PP TPE PPPP Fig. 21 TPE PPPP TPEPPPP TPEPP PP TPE PP TPEPP PP PP TPE TPE TPE PP 2-

8 Welding Strength (N) PP/ EPR = 5 / 5(wt%) 5 ΔTm = 2 C ΔTm = 19 C TPE TPEPP Fig Welding depth (mm) ΔTm = (Melting temperature of PP substrate) (Melting temperature of PP in TPE) Detachment direction for evaluating welding strength TPE PP substrate 3 mm 3mm Effect of melting temperature on welding strength to PP substrate TPE 1) TPE,, 2 7, 34(2). 2), JETI, 53(12), 51(25). 3),,,,,, 1997-@, 24(1997). 4),, 28 7, 6(28). 5), (27). 6),,, (2). 7), (1975). 8) 29, (29), p.. 9) N. Bokhari, H. Toyoda and K. Ohtani, POLYOLEFIN RESIN FOR AIRBAG APPLICATION -MORPHOL- OGY OF SOFT RESIN AND PARTS PERFORM- ANCE-, TPE 25, Paper 6 (25). ) N. Bokhari, K. Ohtani, T. Hisayama and N. Yamaguchi, Superior Appearance Material in Airbag Cover Applications, SPE Automotive TPO conference, Application Development session (29). 11), (27). 12), (26). PROFILE Kousuke OHTANI Tatsuo SASSA 2-