A dirty job for plastics
Plastics clean up
The market of sponges for individuals is a large one. Sponges are a cheap item that can be found in all bathrooms and kitchens and that are replaced at the first signs of wear. As a result, Europeans consume many million sponges each year. In short, there are three categories of sponges: natural sponges, which are found in the sea, plant-based sponges made from wood cellulose and cotton, and synthetic sponges which are most often made from polyester foam. In addition, there is also microfibre cloth (often with a diameter below 9 micrometres) made from polyamide or polyester. Synthetic sponges are the norm in Europe, except in France where consumers prefer plant-based sponges. The reason for this is simple: synthetic sponges absorb liquids as well as any other at lesser costs. And for such a common object, the price is of major importance.
They are kept at an affordable price thanks to the material used: polyester, a common and very easy to manufacture polymer. Like plant-based sponges, synthetic sponges have a rough side made up of a mixture of polyester and nylon.
Keeping babies dry with polymers
In the late 1960s, a revolution occurred among young parents thanks to the arrival of disposable diapers! In the past, diapers had to be washed, which was a real chore for many mothers - sharing responsibility for chores was still just a vague concept at the time. 1The beginnings of this invention appeared in the 1950s, when British firm Robinson and Sons developed a semi-disposable diaper whose cellulose-based absorbent pad could be replaced. The envelope, made from easily-washable nylon, could be reused. The company would be the undisputed leader in the industry well into the 1960s, when competitors were already looking for a way in. The recently-founded Pampers company made significant resources available to its researchers with the aim of improving the disposable diaper. This would be achieved in the early 1970s, not through marketing, but well and truly thanks to the quality of its products.
Competition remains fierce to this day. Price remains an important factor, but parents generally still want what's best for their babies. Today, diapers are a perfect showcase of the ingenuity of polymers.And with good reason, because they are not made of a single part but are in fact comprised of many components. The surface veil (the non-absorbent part in contact with the skin) is most often made from polypropylene, as is the envelope, although the latter is generally microaerated to let the skin breathe. The most extraordinary part of the diaper remains the composition of the absorbent pad. It must absorb liquids, not release them once absorbed like a sponge might, because babies move a lot! And be comfortable.
The most advanced models are made using sodium polyacrylate, a "super-absorbent" polymer. Various sheets of polyester and polypropylene encapsulate it and are designed to trap the liquid and channel it to the centre of this pad made from "super absorbent" polymer. The elastic bands and fastening systems are made from a mix of elastomers and polypropylene.
Polymers bring out the best in burgers
A small revolution benefiting lovers of pizza, hamburgers and frozen fries took place around a decade ago. The susceptor is not a material in the strictest sense of the word, it is made from stacking various materials which absorb microwaves and convert them into heat. In other words, we owe the possibility of re-heating a hamburger in the microwave and having a crisp bun to the susceptor. It is difficult to attribute paternity of the idea to any one person as the process has been continuously improved upon over the past years. Nevertheless, it seems like Nasa may have come up with the idea first, not to improve meals for its astronauts, but rather as part of their search for a material able to absorb the microwaves naturally present in space which are harmful to space travellers.
It would only be in the late 2000s that the agri-food industry would find a use for it. Its exact composition remains a closely-guarded secret; all we know is that it is made up of metallised polyester films and a moisture absorber. Finally, the latest generations have micro-perforations which absorb excess fat and water for an even crisper result.
Plastics to promote healing
Fortunately, for many people, a bandage is simply a self-adhesive elastomer-type polymer with a small cellulose pad. Those are used for small cuts and they are generally more than sufficient. Unfortunately, some wounds require considerably more treatment which has to be entrusted to a nurse. The commercial and sanitary stakes in the field of technical bandages are so high that innovations are commonplace. The challenge lies in finding a formula that absorbs exudates, fluid leaks, from the wounds while conforming to the shape of the body and letting the skin breathe. The latter requirement led to the selection of silicon, a flexible, non-aggressive polymer which, when microperforated, becomes breathable. Many bandages use polyurethane foam for absorption, as it is an inert polymer able to be painlessly inserted into deep cavity wounds.
Manufacturers are increasingly looking at spray-on bandages for future developments. Much research is being carried out, and the most promising prospects involve combining microspheres of bioactive glass, known for its haemostatic properties, with a gel polymer. There is not much information available about the polymer at this time.
Polymers full of energy
It can be useful to absorb an impact to avoid trauma. In this area, plastics reign supreme! Their flexibility and robustness are such that they are champions at absorbing energy and diffusing it to make it disappear gradually. The fenders used on boats are one of the best examples of this. They have a simple purpose: protecting a boat's hull against impacts against a dock, for instance. They are in fact composed of a polyurethane envelope inflated at low pressure. In the event of an impact, it compresses and completely absorbs the energy with no rebound effect. The system is so effective that French manufacturer Citroën used it on the doors of one of its vehicles. Christened Airbump, the protective devices give the car in question an inimitable appearance.
Another example is bulletproof vests made from Kevlar, another polymer. Their purpose is to stop the projectile in its tracks. But that is not all, they must also dampen the shockwave by diffusing throughout all of the fibres composing the vest. In the same vein of saving people's lives, polyamide airbag vests which can be worn under a jacket have also appeared on the market. The principle is the same as that used for the airbags found in all vehicles: in the event of an impact, the vest inflates and protects the skier's, biker's or even horse rider's neck and chest.