Sometimes we see some woven and knotted fishing nets being used as trellis netting instead of the more popular extruded bi-oriented net. These knotted nets are made out of a twisted multi-filament twine that is more commonly used for fishing and fisheries underwater with low UV direct exposure. On the contrary, a trellis netting is used directly under the sun therefore it must be designed to last high LUX / Kly counts, otherwise the whole crop could collapse half way thru the cycle with enormous damages, not only to the trellising system, but to the plants and fruits ready to be harvested.
Speaking of UV rays, these damage polymers and their physical characteristics progressively as solar exposure advances. Without getting into the detailed chemical and physics of why and how plastic crystallizes (this can be noticed with the bare eye as the natural gloss fades and plastic seems “dried”) we´ll make an easy to follow example. Just like paleontologists or archaeologists can measure the years a rock has been exposed to the sun by the microns of the color change and wear and tear on the surface skin of the stone (even with granites) also with plastics the sun needs X time to damage the polymeric structure of a plastic product (UV inhibitors can only slow down the process). This slow decay is measured in microns / time during the length of the study. In other words, a plastic twine or string looses its physical characteristics faster the thinner this product is, as the UV damage progresses inward a thicker diameter mono-filament will resist longer than a series of thinner multi-filaments.
In other words, a knotted / woven net made out of thinner multifilaments will decay logarithmically faster than a extruded bi-oriented net monofilament because the sun reaches the hearth of each individual twine much faster than a thicker extruded net. The external surface or skin of an extruded bi-oriented net acts as a protection and barrier against the sun, guaranteeing a longer life span and the re-usability for many crop cycles.