Twaron

Production

Polymer preparation

Twaron is a p-phenylene terephthalamide (PpPTA), the simplest form of the AABB para polyaramide. PpPTA is a product of p-phenylene diamine (PPD) and terephthaloyl dichloride (TDC).

At the time only 30.000 kg p-phenylene diamine (PPD) per year was available world wide. The AKZO Research Laboratory in Hengelo, by Dr. J. de Graaf, created a process to have the yearly needed 30.000.000 kg PPD per year. At first the process created a bit of carcinogens, but this was resolved by adding methyl methacrylaat (MMC) when diazotisating Aminobenzeen.

To dissolve the aromatic polymer Twaron used a co-solvent of N-methyl pyrrolidone (NMP) and an ionic component (calcium chloride CaCl₂) to occupy the hydrogen bonds of the amide groups. The invention of this specific process was done in 1974 at AKZO Research Laboratory in Arnhem by a team consisting of Leo Vollbracht, Teun Veerman (assistant of Leo Vollbracht) and Wim Engelhard (trainee, who actually discovered NMP as the appropriate solvent to keep the growing polymer as long as possible in solution; he also discovered that high speed mixing of PPD and TDC was necessary to obtain a sufficiently long polymer chains). The patent of the newly discovered process route led to a patent war between AKZO (Fibre X) and DuPont (Fibre B) as Dupont initially used the carcinogenic HMPT (hexamethylphosphoramide). Despite heavy research DuPont now also applies the AKZO patent for their Kevlar process and use the less hazardous NMP.

Spinning

After the production of the Twaron polymer in Delfzijl, the polymer is brought to Emmen, where fibres are produced by spinning the dissolved polymer into a solid fibre from a liquid chemical blend. Polymer solvent for spinning PPTA is generally 100% anhydrous (water free) sulfuric acid (H₂SO₄). The polymer is dissolved by mixing frozen sulfuric acid in powder form with the polymer in powder form and gently heating the mixture. This process, which differs from the more difficult DuPont process, was invented by Henri Lammers and patented by AKZO.

Use

Twaron is a para-aramid and has automotive, construction, sports, aerospace, and military applications, e.g., in modern body armor, fabric, and as an asbestos substitute.

Protective gear (heat resistant / ballistics)

flame-resistant clothing, protective clothing and helmets, cut-fast or heat-hardy gloves, sporting goods, textiles, ballistic vests

Composites

composite materials, technical paper, asbestos replacement, hot air filtration, sailcloth, speaker woofers, boat hull material, fiber reinforced concrete, drumheads

Automotive

brake pads, turbo hoses, V-belts and Timing belts, tires that incorporate Sulfron (sulfur modified Twaron), mechanical rubber goods reinforcement

Linear tension

optical fiber cables (OFC), ropes, wire ropes, electrical cables, umbilical cables, electrical mechanical cable (EMC), reinforced thermoplastic pipes

Yacht construction

on monohulls and catamarans (such as the Catana 581), the glass fibre hull may have an inner skin of Twaron aramid fabric laminated over the core to increase stiffness and impact resistance.