A while back we did a forensic study on the deterioration and degradation of polyurethane coating in garments. It’s summer, so let's look at the deterioration of the elastic thread in a bikini top.
The study focuses on two identical bikinis by Jaked, a brand founded in 2008 in Italy, that also makes technical and high-performance swimwear for athletes and often uses thermo-welding to eliminate seams and offer maximum comfort.
We will call the bikinis Exhibit A and B and consider the degree of deterioration they went through in a few years' time.
Exhibit A
Description: Exhibit A refers to a fuchsia bikini by Jaked.
Fit: Basic low-rise bikini with a triangular top that offers minimum coverage and bottoms that fit large to size. The bikini does not feature any metal/sequined/beaded elements, the only decoration is a ruffled trim. The ruffle is made with the same fabric of the bikini and it is applied on a thin silicone strip stitched onto the bikini.
Feel: The fabric is pleasant to the touch; the bra strings are soft and elastic.
Material: 80% Polyamide - 20% Elastane, the white lining (the bikini is fully lined) is 100% elastane.
Labels/Warnings/Washing instructions: The washing instructions explain the bikini should be handwashed at 30°.
Storage: After every summer, the bikini was handwashed and stored back in its original clear plastic pressure pouch.
History: The bikini was bought 4-5 years ago; it was worn regularly at least 4 days a week (for 2 hours a day) for three months a year (between June and August). "Worn regularly" in this case means the bikini was worn at the beach and in the sea. After a day at the beach, the bikini was immediately handwashed according to the instructions.
Deterioration: The bottoms became slightly looser, but that often happens with swimwear, so it is not surprising. The top showed signs of deterioration mainly where the strings were knotted around the neck and the back. The strings are around 8 mm thick, but deterioration reduced them to roughly 4-5mm.
More recently something unusual happened to the strings: after wearing the bikini top in extreme temperatures (over 33°C) and walking under the sun and along the beach for several kilometers (roughly 4 km), the elastic thread inside the strings melted adhering to the body and sticking to the neck and the back.
Adhesive traces on the skin had to be removed with after waxing wipes. Even after handwashing the bra, the strings remained sticky and unpleasant to the touch.
Exhibit B (Identical to Exhibit A, but in black)
Description: Exhibit B refers to a black bikini by Jaked.
Fit: Basic low-rise bikini with a triangular top that offers minimum coverage and bottoms that fit large to size. The bikini does not feature any metal/sequined/beaded elements, the only decoration is a ruffled trim. The ruffle is made with the same fabric of the bikini and it is applied on a thin silicone strip stitched onto the bikini.
Feel: The fabric is pleasant to the touch; the bra strings are soft and elastic.
Material: 80% Polyamide - 20% Elastane, the black lining (the bikini is fully lined) is 100% elastane.
Labels/Warnings/Washing instructions: The washing instructions explain the bikini should be handwashed at 30°.
Storage: After every summer, the bikini was handwashed and stored back in its original clear plastic pressure pouch.
History: The bikini was bought 4-5 years ago; it was worn regularly at least 3 days a week (for 2 hours a day) for three months a year (between June and August). "Worn regularly" in this case means the bikini was worn at the beach and in the sea. After a day at the beach, the bikini was immediately handwashed according to the instructions.
Deterioration: The bottoms became slightly looser, but that often happens with swimwear, so it is not surprising. The top showed signs of deterioration mainly where the strings were knotted around the neck and the back, but nothing as bad as the other top happened.
Yet, you can see there are already signs of the elastic deterioration happening: little filaments of elastic thread are indeed coming out of the bikini top strings. The bottoms also show deterioration of the elastic thread around the edges of the ruffles. The deterioration is more evident in this bikini than in the fuchsia one.
Conclusions
Swimsuits go under extreme deterioration when you wear them often and for a few years consecutively, that's perfectly understandable, but it is curious to see an elastic that should be used in a garment exposed to high temperatures melting. I previously saw a children's swimsuit melting when exposed to a jet of hot air from a hair-dryer in the changing room of a swimming pool, but, in this case, the bikini was not exposed to the direct jet of hot air, only to extreme temperatures.
Was it the extreme temperature that caused it? Was it the fact that it was already showing signs of deterioration? Probably both. It remains curious that this happened to a product by a brand that boasts about its products, such as its engineered competition swimsuits, being tested in swimming pools and in laboratories (well, they may have forgotten to test bikinis, though, as they are not for competitions...). Usually their swimsuits are also resistant to UV light (UPF 50+), but ,well, maybe their elastics aren't.
The final point of this quick forensic analysis is not showing the deterioration per se, but wonder if garments such as swimsuits may release micro filaments of elastics or microplastics (tiny plastic fragments from bigger plastic items such as bottles, but also synthetic T-shirts) in the sea, materials that may be harmful to the environment and to animal and human health. Researchers are currently working on systems that may manage one day to clean the sea from such polluting micro materials, but we haven't got anything definite yet.
The good news, though, is that scientists from the Polymer Research Institute of Sichuan University recently unveiled on the Nano Letters journal a bionic self-propelled 13 mm long robo-fish capable of removing microplastics from seas and oceans. The small yet resistant robo-fish can pull up to 5kg in weight, and adsorbs bits of microplastics on its soft, flexible body because the organic dyes, antibiotics, and heavy metals in the microplastics have strong chemical bonds and electrostatic interactions with the material the mini-robot is made of.
Let's hope we will find a solution for microplastics. But, returning to the bikini, there is another question about it: how should we dispose of such garments. A worn out bikini top like the fuchsia one in this post may not be recycled and would probably end up in a landfill. How can we avoid this?
There are brands that have developed collections of swimsuits from recycled plastic, but will we manage one day to create a bioelastic thread (maybe from algae or from food waste?) that could be used in swimsuits and avoid in this way to harm human and marine life? Let's all try and find the answer to these questions, in the meantime, I'll go and find a new swimsuit.
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