Report Young’s Modulus
Report Young’s Modulus [MPa] 2000 500 1900 450 1800 400 1700 350 1600 300 1500 250 1400 200 1300 150 1200 100 1100 50 1000 1 3 7 0 Number of extrusion steps [-] Young’s Modulus (MD) | Young’s Modulus (TD) | Dart drop Fig. 5: Young’s Modulus and dart drop of multiple processed PLA Number of extrusion steps 1 3 7 Degree of crystallinity [%] 1.2 2 2.7 Table 1: Degree of crystallinity for multiple extruded PLA films measured by DSC References: [1] THRONE, J.; BEINE, J.: Thermoformen. Munich, Vienna: Carl Hanser Verlag, 1999 www.ikv-aachen.de Impact failure weight [g] The Young’s Modulus of the film increases with the number of extrusion steps. A growth of 5 % in both directions (TD and MD) is achieved between processing steps 1 and 7. The impact failure weight as a result of the dart drop test is increased, too. This is due to a higher degree of crystallinity of the film. Unlike the results of the recycling with varying recycling quotas the molecular weight loss of the 3 times (10 %) and 7 times (17 %) recycled PLA is higher. A low average chain length (molecular weight) enables the polymer to crystallise more during the solidifying on the calender stack. This is well covered in published literature [1]. The degree of crystallinity is shown in table 1. The higher crystallinity increases the mechanical properties (Young’s Modulus). Since the increase in crystallinity is little, the overall effect on the mechanical properties is marginal. The crystallinity between steps 3 and 7 does not change much. The mechanical properties remain almost constant. Chain scission through degradation compensates for the effect of crystallisation. With regard to further decreasing of the molecular weight the dart drop resistance decreases slightly. Conclusion The investigations into the recycling of PLA show that the industrial recycling of PLA is possible with a low loss of film properties. Because of the hygroscopicity and the hydrolysis of PLA the drying of r-PLA is necessary. The reprocessing with a recycling quota of up to 45 % leads to a marginal degradation of the PLA. The molecular weight drops around 3 % and the mechanical properties decrease by 8 %. Multiple recycling shows the long term behaviour of material which stays in the process over multiple recycling steps during continuous recycling. A low decrease of the molecular weight below 20 % of a 7 times extruded film can be found. This degradation can be ignored. Especially, when taking into account that during the continuous recycling only a small amount stays for 5 or more cycles in the process. The effect of the lower molecular weight affects the degree of crystallinity. This has a bigger effect on the properties than the achieved molecular weight loss. The mechanical properties of multiple recycled films are slightly increased with nearly constant elongation properties. The thermoforming behaviour is slightly decreased due to a higher crystallinity haze and clarity increase. The research project 44 EN of the “Forschungsvereinigung Kunststoffverarbeitung” has been sponsored as part of the “Collective Research Networking“ (Cornet) by the German ministry for technology and commerce (BMWi) following an act of the German parliament through the AiF. We would like to extend our thanks to all organizations mentioned. 24 bioplastics MAGAZINE [01/14] Vol. 9
Applications New bioplastic applications in windows More and more architects and clients are demanding new, ecologically viable products which have maximum potential for reducing CO 2 and conserving natural resources. With its green generation of products, German window and façade expert Schüco from Bielefeld is addressing the issue of finding potential alternative materials for petroleum based plastics. The FW 50 + .SI Green façade system and the AWS 90.SI + Green aluminium window system integrate components such as insulating bars, gaskets and pressure plates with a proportion of renewable materials. This development is possible in part due to the use of partly biobased polyamide (made using sebacic acid generated from castor oil), that forms the basis for the pressure plates of the FW 50 + .SI Green façade system and for the green insulating bars which are integrated into the Schüco AWS 90.SI + Green window system. The castor oil is even used for the foam of these insulating bars. Schüco is also making a marketing contribution for the transfer of biotechnology for gaskets in both of these profile systems, by using EPDM (synthetic rubber) made from sugar cane based bio-ethanol. The same standards apply to all these materials: an initial and then annual inspection by an independent certification process (DIN CERTCO, 14 C analysis) guarantees that the proportion of renewable raw materials strived for is also achieved. With the Schüco AWS 90.SI + Green and Schüco FW 50 + .SI Green system enhancements, the company is combining the approved use of renewable raw materials with thermal insulation to passive house level and above. The FW 50 + .SI Green façade system meets the strict passive house certification criteria set by the Passive House Institute in Darmstadt and has been certified as passive house standard since BAU 2013 (building and construction trade fair in Munich/Germany). Combination of sustainability and energy efficiency Thermal insulation is the primary decisive factor in the energy revolution. Many local authorities have already pledged to implement thermal insulation to passive house level as standard when constructing new public buildings. The Schüco Green window and façade systems fulfil precisely these requirements. Both constructions combine the advantages of durable aluminium with thermal insulation to passive house standard, thereby conserving natural resources and reducing CO 2 emissions. Equipped with plastics containing a significant proportion of renewable raw materials, these windows and façades now make a double contribution to the reduction of greenhouse gases, since they have a lower potential for global warming. This means that using renewable raw materials releases fewer greenhouse gases into the atmosphere during manufacturing and it also conserves natural resources. MT Schüco Window AWS 90.SI+ Green (photo: Schüco International KG) 1: Insulating bars: Bio-Polyamide Bio-content ( 14 C): > 25 % 2: Insulating zone: Biobased PUR-foam Bio-content ( 14 C): > 25 % 3: Glass rebate gasket: Bio-EPDM Bio-content ( 14 C): > 20 % Schüco Façade FW 50+.SI Green (photo: Schüco International KG) 2 1 1: Contact pressure profile: BIO-Polyamide Bio-content ( 14 C): > 25 % 2: Glass rebate gaskets: BIO-EPDM Bio-content ( 14 C): > 20 % System achieves level of „Passivhausniveau“ U cw ≤ 0,80 W/m²K 3 www.schueco.de/aws-90si-plus-green-en 2 2 1 1 2 bioplastics MAGAZINE [01/14] Vol. 9 25
