Silver coated tent fabric and UV decay
Silver coated tent fabric greatly reduces the UV decay of polyester tent fabric when the silver coating is on the side that is exposed to the sun.
Introduction to silver coated tent fabric ageing
I was not satisfied with the condensation and wet stretching performance of my DIY backpacking tents made of silnylon. Consequently, I switched to using a silver coated polyester umbrella fabric. To my delight, it addressed both problems and is reported in my post; DIY breathing polyester tent for backpacking. How it would survive harsh outdoor conditions was an unknown. “I did have a hunch that the silver coating would be UV protective and put the silver side on the outside of my tents.”
Subsequently, I started a fabric ageing tests by hanging various samples of DIY tent-making fabrics and cords on my washing line in a sunny location. Most fabric samples were prepared as sewn tubes (30mm wide when laid out flat). Load-bearing hems were sewn on the ends of each tube so that the samples could be load tested to determine their relative strength after exposure.
I made the samples tubular so that polyester fabric with the silver coating could have only its reflective side exposed to the sun. One inside-out sample of silver coated polyester was included to see if it would degrade more quickly with no silver coating for protection.
After 500 days of exposure to the elements all samples that were not shielded by a silver coating on the outside had significant signs of sun-bleaching decay of the original colour. Interestingly, a silver coated tube, when opened up after 500 days (after being broken during load testing), had its colour largely preserved as shown in the photo below. “I was so busy that I forgot to test the inside out silver coated sample.”
Load testing of the samples after exposure was my main interest in order to compare the silver coated polyester fabric with some traditional silnylon that had previously been my go-to DIY tent fabric. The exposed silver coated polyester broke with a ~9kg load while the exposed silnylon broke with only a ~3kg load. This finding triggered further testing of the loading capacity of the fabrics when unexposed. For more details please see; Polyester strength for backpacking tents.
Load testing inside-out silver coated test sample
In the previous post, the polyester fabric was much stronger than the silnylon sample after 500 days of exposure. I speculated that the reflective silver coating on the polyester probably accounted for the good UV performance, rather than the type of polymer per se. This runs contrary to the popular belief that polyester is innately more resistant to UV than nylon Examples of this are; Jason Mills, Novapro Sports, National Webbing Products. However, empirical testing of many weathered backpacking tent fabrics by Slingfin is more equivocal on this issue.
So, being a bit slow, I remembered that I had my original faded inside-out sample of silver-coated polyester hanging on my washing line. I was certain that load testing this rather pathetic-looking sample would shed light on my speculation about the reflective protection of the silver coating.
Rather belatedly at 540 days, I prepared to load test the sample. While it was supporting the ~1kg water bucket I clumsily adjusted the testing rig (as a normally do) settling all the fiddly links into their ‘right’ places and this little extra load caused it to start to break. I estimated that I applied an extra one or possibly two kg load to the bucket, making the total load only 3kg or less.
Conclusion
To me, the ~9kg and the ~3kg breaking load for the silver outside and silver inside is a clear indication of likely the protective nature of a reflective coating when on the outside of tent fabric.
I don’t know if silver coating could be applied to silnylon, but if it could it may improve its longevity. However, the silver coated polyester has become my favourite DIY tent fabric because it causes minimal condensation, has negligible wet stretching, dries more quickly than silnylon and is more resistant to sun damage.
Tim
Addendum 1
A summary of my fabric and cord testing in the table below might provide a better context for my testing of these materials for use in backpacking tents.
Nylon and polyester strength after extended sun exposure
| Table 1. Breaking loads of various tent fabric samples and cords before and after extended sun exposure. Also subjective assessment of the performance of the materials for backpacking pyramid tent. The fabric test samples were sewn tubes of fabric that were 30mm wide. The samples were supporting a suspended bucket/s to which 2L jug loads of water was added. The weights shown (~kg) included the tare weight of the bucket/s and were based on the equivalence of one litre of water=one kg | |||||
|---|---|---|---|---|---|
| Sample type | Polyester umbrella fabric silver coated | Silylon ripstop fabric 1 (grey) | Silylon ripstop fabric 2 (orange) | Polyester cord (brickies line, yellow) | Nylon cord (brickies line, yellow) |
| Material property | |||||
| Estimated material weight | ~57gsm | ~37gsm | ~37gsm | xx/m | xxg/m |
| Fabric strength in as-new condition (breaking load kg) Post link | >40kg | ~38kg | ~16kg | 38kg | 38kg |
| Fabric strength after 500 days of weather exposure (breaking load kg) Post link | ~9kg | ~3kg | NA | NA | NA |
| Fabric strength after 540 days of inside-out exposure Post link | ~3kg | NA | NA | NA | NA |
| Cord strength in as new condition before weather exposure (breaking load kg) Post link | NA | NA | NA | 38kg | 38kg |
| Cord strength after 540 days of exposure Post link | NA | NA | NA | 19kg | 29kg |
| Other performance characteristics | |||||
| Fabric permeability to prevent tent condensation | Good | Poor | Poor | NA | NA |
| Fabric resistance to wet stretching | Excellent | Poor | Poor | not yet tested | not yet tested |
| Speed of drying for cold morning pack ups Post link | Excellent | Poor | Poor | NA | NA |
| Bond strength when glued with silicone rubber. [Add post link when available] | Very poor | Good | Excellent | ||
| Fraying/unraveling [Add post link when available] | NA | NA | NA | Poor | Good |
| Simple knot holding [Add link when available] | NA | NA | NA | Poor | Good |
| The meaning of life [Add post link when available] | NA | NA | NA | NA | NA |
