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Issue 01/2017

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  • Bioplastics
  • Biobased
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  • Renewable
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Automotive Materials By:

Automotive Materials By: Erico Spini Marketing and Application Development Director Europe Radici Group Performance Plastics Chignlo d’Isola (BG), Italy New automotive applications for bio-PA Air brake pipes and tank breather hose made of biobased PA 6.10 Fig 1: Extruded air pipe made of Radilon D 40EP25ZW 333 BK for the pneumatic braking system of a truck (photo: RadiciGroup) Fig 2: Extruded heat and media-resistant car tank breather hose (blue) made of partially biobased PA6.10, in assembled state (photo: RadiciGroup) A more comprehensive version of this article was previously published in KUNSTSTOFFE 8/2016 and can be found here In numerous areas of application, materials based on renewable resources can already replace plastics based on fossil raw materials and thus contribute to the more sustainable handling of resources. RadiciGroup Performance Plastics (Chignolo d’Isola, Italy), has commercialized a range of partially biobased PA 6.10 types that are suitable for a wide variety of applications in many areas of industry. The examples selected here are an air brake pipe for trucks (Fig. 1) and a tank breather hose for passenger cars (Fig. 2) from Fiat Chrysler Automobile (FCA), (Orbassano, Italy). Both applications pose particularly high demands on material testing and approval procedures. Polyamide from renewable raw materials PA 6.10 is a partly biobased Polyamide made of petroleum based hexamethylene diamine and around 64 % biobased sebacic acid. Sebacic acid is obtained from the beans of the castor oil plant which is cultivated above all in India and China. Since it grows primarily on dry soil, it does not compete for the production of foodstuffs. Properties PA6.10 is a semi-crystalline polymer, available as both an injection molding grade and an extrusion grade. Furthermore, fillers, stabilizers and additives can be incorporated to finetune specific properties for a particular application. Among its outstanding characteristics are low water absorption, high heat resistance, very good chemical resistance and good mechanical properties. The water absorption of test bars according to ISO 62 on exposure to a standard climate (23 °C, 50 % relative humidity) and on immersion in water is shown in Figure 3. The water absorption on immersion is around a third of the value obtained with PA6 and PA6.6. At 50 % relative humidity, the moisture absorption is somewhere between the values for PA6.6 and PA12. The biobased PA6.10 is thus suitable for most applications that call for good dimensional stability in moist environments. The melt and heat deflection temperature (HDT B) are in the range of PA6, but significantly higher than PA11 and PA12 (Fig.4). This is particularly important if the material is to be used as a substitute for PA11 and PA12, for example for applications in which the temperatures exceed those tolerated by PA12, as is the case with many diesel fuel lines in new cars. Furthermore, the polymer has very good chemical resistance (also in the presence of salts such as zinc chloride and calcium chloride), high hydrolysis resistance and, compared with PA6 and PA6.6, undergoes smaller changes in the mechanical properties after the absorption of moisture. 18 bioplastics MAGAZINE [01/17] Vol. 12

Automotive Pneumatic brake lines For pneumatic brake systems air pipes, RadiciGroup has developed the extrusion grade Radilon D 40EP25ZW 333 BK (Fig. 1). The material has particularly high flexibility in order to facilitate installation of the pipes, which, especially with trucks, can reach a considerable length. Furthermore, it is heat-stabilized, which means that components made from it can be exposed to high temperatures even over a prolonged period. Based on the burst pressure curve up to a temperature of 125 °C, the material is suitable according to ISO 7628 for lines at a nominal pressure of up to 10 bar and up to 12.5 bar. Figure 5 shows the burst pressure after the contact with media that trigger stress cracking, and after aging in artificial light. The corrosive solution is made up of 50 % water, copper chloride, sodium chloride, potassium chloride and zinc chloride. For aging in artificial light, the pipe was irradiated with xenon lamps for 750 h at 65°C. In this case, too, the burst pressure must be at least 80 % of the original value. Tank breather hoses As part of a joint project with FCA, RadiciGroup has developed a material that has similar properties to the material described above. At the request of the customer, the material is colored blue and is used for the production of tank breather hoses for cars (Fig. 2). Such parts are conventionally made of an impactmodified PA12 incorporating a plasticizer. During development of the material, particular attention was placed on the ease of processing via extrusion. Here, low part tolerances are essential. The corrugated tubes must, especially in the corrugated areas, comply with strict measuring tolerances as too thin areas in the wall can lead to failure of the component during operation. The part was subjected to a number of tests to determine its suitability for practical application. The component passed for example a pressure test at 2.5 bar before and after thermal aging at 90 °C for 168 h. The specimen also successfully passed the cold impact strength test using a free falling dart (2 kg weight, diameter of the hemispherical ended portion of the dart:10 mm) when dropped from a height of 400 mm and 500 mm after storage at -40 °C for 4 h. These tests were performed both on fresh new parts and on others that had been aged in hot air at 90 °C for 168 h. Furthermore, a pull-off test was carried out on the hose and/ or connections both when new and after aging in fuel vapors at 60 °C over a period of 168 h. Subsequently, the specimen was bent by 180 °C in a radius corresponding to five times the outer diameter of the hose. After this, there was no visible damage, not even at the fixing points for the connections. Conclusions The example of PA6.10 shows that engineering plastics based to a large extent on renewable raw materials can replace materials of fossil origin even in technical parts. Specific formulations geared to the respective application help to meet or even exceed the requirements for the approval of critical components such as pneumatic brake pipes and tank breather hoses. Potential new applications are currently emerging through the demand for ever higher operating temperatures. Because of its high thermal resistance compared with materials used until now, additional possible applications in vehicle fuel systems could thus emerge for PA6.10. % 10 9 8 7 6 5 4 3 2 1 0 PA6 PA 6.6 PA6.12 PA6.10 PA12 PA11 PPA Moisture Absorption Water Absorption Fig. 3: PA6.10 has, at 50% relative humidity, a much lower water absorption than PA6 and PA6.6 and is approximately the same as PA12 following water immersion (source: RadiciGroup) °C 300 250 200 150 100 50 0 PA6 PA 6.6 PA6.12 PA6.10 PA12 PA11 HDT B value (at 0,45 MPa) Melting temperature Fig. 4: With PA6.10, the heat deflection temperature and melt temperature are in the range of PA6 and significantly higher than PA11 and PA12 (source: RadiciGroup) bar 80 70 60 50 40 30 20 10 0 60 Burst pressure after stress cracking Minimum 40 bar for tubes with nominal pressure of 12.5 bar Minimum 32 bar for tubes with nominal pressure of 10.0 bar 69 Burst pressure after aging in artificial light Fig. 5: Burst pressure after exposure to media that trigger stress cracking, and after aging in artificial light (source: RadiciGroup) bioplastics MAGAZINE [01/17] Vol. 12 19

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