Formability of paper-based materials: The influence of mechanical properties

Transcription

1 Formability of paper-based materials: The influence of mechanical properties EFPRO-CEPI Early Stage Researchers Workshop 13 November A. Vishtal, 2 M. Hauptmann, 2 R. Zelm, 1 E. Retulainen 1 VTT Technical Research Centre of Finland 2 Technical University of Dresden

2 2 Contents What? & Why? & How? Results: Influence of the temperature and moisture in forming Elongation of paper vs. Depth of the shape Compressive properties vs. Appearance of the shapes Metal-paper friction vs. Appearance of the shapes Summary Acknowledgments

3 3 What? & Why? & How? What? Moldability (syn. Formability) - is the ability of material to deform adequately in the forming process without breaks and defects in appearance This property is also determining how advanced shapes can be formed out of paper (depth, curvature, side wall angle Paper Metals Plastics Formability This work aims to clarify the mechanical properties of the fibre network important for the formability, and link this data with the appearance of the formed shapes

4 4 What? & Why? & How? Why? Fibre webs with high formability can replace certain types of plastic packaging, and can be used for production of novel products Trays, cups Plastic from chocolate box? Paper bottle? Benefits: Reduction of environmental load Adding higher value to paper products Broadening designing possibilities for paper-based packaging Space shuttle?

5 5 What? & Why? & How? In order to improve formability one should know what kind of mechanical properties of paperboard are important for the 3D-forming processes The appearance (depth & wrinkling of the side wall) of the formed shapes VS. with mechanical properties of paper Influence of moisture, temperature and other process parameters was also studied 7 different commercial samples (grammage g/m2) A B C Figure 1. Forming devices used for the for the characterization of the formability; (A)-2D-formability tester, (B)-spherical 3D-forming device, (C)- 3D-deep-drawing forming device Forming in standard conditions (23 C, 50%RH)

6 6 Influence of Moisture and Temperature in Forming Temperature in forming vs. Formability* 3Dspherical forming device* *Values are given as %-change in comparison with the formability measured at 23 C

7 7 Influence of Moisture and Temperature in Forming Elevated Moisture* vs. Formability 3Dspherical forming device *conditioning at 75% RH ( Moisture content was 10-11% instead of 6-7% (50%RH) ** Values are given as %-change in formability in comparison with the 50% RH-conditioned samples

8 8 Maximum depth of the shape vs. Strain at break 3Dspherical forming device No correlation for MD strain at break was found

9 9 Compressive strength & Compressive Strain vs. Appearance of the shapes Compressive strength - Amount of wrinkles - Wrinkles are deep and big - Appearance Compressive strain - Amount of wrinkles - Wrinkles are deep and big - Appearance

10 10 What are the components of the formability-role of paper properties (Friction Coefficient) Friction - Amount of wrinkles - Smooth Surface - Appearance

11 11 Summary Temperature and moisture can be used for the adjustment of the forming results The depth of the shapes is determined by the elongation of material The appearance of the shapes correlates with friction, compressive strain, thickness and density (not shown in this presentation) Process parameters such as blank holding force, temperature in forming, drawing sequence, and forming gap are equally important for maintaining of the appearance of the shapes

12 12 Acknowledgements Following organisation are acknowledged for providing financial support for this work: The International Doctoral Programme in Bioproducts Technology- PaPSaT Future biorefinery programme of FIBIC Ltd. VTT Graduate School The Association of European Fibre and Paper Research Organisation - EFPRO Stora Enso Oyj Finland

13 13 APPENDIX I: Wrinkling of the side wall As lower distance between wrinkles as more wrinkles on the shape, and it means that with the increase in amount of wrinkles its depth and width are decreasing e.g. surface is smoother L Figure I-B. The image of the side wall of the formed shape with the deep and large wrinkles Figure I-A. An Example of microscopic image of the side wall of the formed shape with the indication of the wrinkles and distance between them Figure I-C. The image of the side wall of the formed shape with the shallow and small wrinkles