Nylon and polyester cord strength
Nylon and polyester cord strength (cheap bricklayer lines, used for backpacking tent guy lines) was tested in unexposed condition and after 540 days of exposure to the elements on my washing line.
Introduction to nylon and polyester cord strength testing
Nylon and polyester cords make excellent light and cheap guy cords for DIY ultralight backpacking tents when new, as discussed in my post; Is nylon or polyester cord best for DIY backpacking tents? Both are abundantly available. Now, I have tested the strength of the cords after long exposure (540 days) to the elements. Unexposed samples were also tested for comparison.The exposure was done concurrently with samples of DIY tent fabrics. There are separate posts; Polyester ageing test for tent fabric and Polyester strength for backpacking tents on this testing. There is also a related post on; Polyester silnylon relative hydrostatic head test.
Nylon and polyester cord strength testing
I have persisted with my passion for primitive but fair backyard bucket testing even at the risk of raising the ire of some armchair experts. I suspended a bucket on the test sample and progressively added two-litre jug loads of water until the sample broke or the bucket was full. I think that recording the testing with video provides good evidence of the impartial nature of the testing, however primitive it might be.
The nylon cord reached a breaking point of 29kg as shown in this little video. The polyester cord reached 19kg as shown in this little video. To provide a context for these breaking loads I tested the unexposed cords with a testing rig with three buckets. Both the nylon and the polyester could support 36kg and broke with a load of 38 kg.
Conclusion and discussion
Both nylon and polyester cords had similar strength (38kg) when in unexposed condition. After exposure to the elements for 540 days, the nylon lost 9kg of strength, while the polyester lost 19kg. The results do not concur with the popular belief that polyester is more resistant to UV degradation than nylon and that polyester is weaker than nylon.
Tim
ADDENDUM 1
The summary table below may help to better summarise the tangled mess of my tent fabric and cord testing for 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 |
