New trials for floating materials
On the 13th of February, Volterra´s team carried out some floating trials on two different materials: Expanded polyethylene and polypropylene. The prototypes had A4 dimensions and 30mm thickness for the polyethylene and 10mm for the propylene, both including one hole. The relation between seedlings per area was kept the same as used in the 2018 plantations in order to maintain the same floatability independent of the prototype size. Prototypes specifications can be seen below:
Figure 1 – Expanded Polyethylene (left) and Polypropylene (right)
Next step was simulate the weight each seedling would have. According to data provided by COMRA and CERTH based on the 2018 plantations, each seedling is estimated to weight around 200g. Therefore, a glass with some soil and water was filled until reach the desired 200g.
The trial consisted on floating both prototypes supporting the glasses filled with soil and water. It was observed that the expanded polyethylene easily floated and presented a good stiffness. Additionally, most of its thickness was still above water meaning the prototype could support much more weight and still floats (this represents a good safety margin).
On the other hand, despite the fact that the polypropylene board floats by itself, when the 200g weight is placed it slowly starts to sink. Some weight was taken from the glass in order to evaluate the maximum weight the board could support. In the end, it was observed that the PP board could support until 130g. However, this material is eliminated from the options for the floating boards; its floatability is too low and is not suitable for the project use.
The next step now is to evaluate how the expanded polyethylene degrades with time in the water and if the material keeps its floatability over time. To serve as reference we placed an EPS board from previous trials, and then we can see the difference on the degradation of both materials.
