Starting from 1937 with the invention of glass fiber, new and daring polymeric solutions of considerable technical-commercial interest have been developed

The evolution of plastics in the period following the end of the Second World War has led the sector to continuous scientific innovation in competition with itself.

The discovery of new polymeric bonds and new commercial applications has revolutionized the industrial field by giving birth to new products, replacing others made of traditional materials and improving the quality ratio price of the artifacts.

In addition to discovering new polymers, technical solutions were discovered that led to an enhancement of the performance of the base polymer, managing to create new fields of application until then unknown.

In fact, the resistance capacity achieved through polymers and polymer-matrix composites was, until a few years ago, unthinkable.

In particular, the HP Fibers sector, designed to provide performances that traditional textile fibers were not able to achieve, especially as regards mechanical capabilities , thermal and chemical, have created a real technological revolution.

Materials which, in addition to being able to meet particular requirements, must show a good aptitude to be included in textile cycles, even if modified.

Born about 30 years ago on the thrust of some strategic sectors - especially military and aeronautics, they are now exploited in the most diverse fields, from the environmental to the clothing sector protective:

• geotextiles for soil containment able to withstand very strong pressures

• fabrics for ballistic protection capable of absorbing the energy of the bullets

• yarns for protective clothing resistant to the energy generated by lightning

• textile reinforcements to be used in composite materials for structural use in the building field.

The first fiber with high performance both tensile and thermal was the glass fiber (1937) produced by Owens and Corning Glass, consisting mainly of silica, oxide of calcium, aluminum oxide, boron oxide.

Belonging to the family of inorganic fibers, it had an annual growth of 15-25% until the 60s - 70s, when the fibers appeared on the market carbon and aramidic fibers, even if to date glass fiber holds the first place in terms of volumes used as a reinforcing fiber.

Carbon fibers, discovered in 1879 by Edison, have only been commercialized since 1960, according to a process developed by William Watt for Royal Aircraft in the UK .

But the real revolution in the world of high-performance fibers began with the appearance on the market (1965) of the aramid fibers developed by DuPont, initially as meta-aramids (Nomex), fibers with a very high melting and decomposition temperature (600 ° - 800 ° C) and excellent electrical insulation characteristics.

These properties make them particularly suitable for the production of fabrics or felts with which to make protective clothing (most of the Formula 1 driver suits are made of Nomex , precisely because of its fireproof properties, as well as those of oil platform operators) and for the filtration of hot gases.

In the form of paper or cardboard, they are used for electrical insulation and, in a honeycomb shape, for the production of composite materials.

A few years later (1972) again DuPont introduced pararamidic fibers (Kevlar) on the market, thus opening the new era of yarns with high tension and thermal performance:

• excellent mechanical resistance

• stiffness

• high radiation absorption

• impact resistance

• to heat

• to the flame.

With Kevlar fiber-reinforced composites, five times stronger than steel for the same weight, the airbags were created that allowed the probes on Mars and the parachute of the Galileo probe, sent to Jupiter.

A cover made with Kevlar-reinforced composites covers the walls of the International Space Station, in orbit around the earth, to protect them from damage caused by micrometeorites.

Kevlar fiber - marketed in the form of filament, staple and pulp, replaces asbestos in the lining of clutches and brakes in all cars coming from the lines European production.

Alongside aramid fibers, aromatic polyester fibers have appeared on the market, those produced with aromatic heterocyclic polymers, or made with the use of flexible molecules (such as high molecular weight polyethylene), for the production of fibers with high molecular orientation along their axis, using a new spinning process, called gel spinning.

In the production of industrial products where resistance must be combined with lightness and flexibility, HP textile fibers are a valid solution, the one that still holds back a their most extensive use is the high cost, mainly a consequence of some technical problems related to their workability.

Generally the higher the performance of the material, the higher the difficulties associated with its transformation.

This is more evident for fibers with very high mechanical resistance, in fact to give them this performance the production method normally followed is to submit the material, after the supply chain, with very high ironing.

With this technique the desired high tenacity is obtained but at the expense of the elongation, consequently the fibers have a low deformability and are rigid, this involves spinning difficulties .

Conversely, an exceptional increase in elongation, therefore in elasticity, is obtained at the expense of toughness and moisture absorption capacity, as well as a high resistance to chemical agents makes the absorption of moisture almost zero and creates difficulties in dyeing the fibers.

Automatic translation. We apologize for any inaccuracies. Original article in Italian.

Info Cecilia Cecchini