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Fibers & Textiles

Fibers & Textiles Nextgeneration fibre Terryl, an innovative, cost-competitive, biobased polyamide for textiles Cathay Industrial Biotech (Shanghai, China) has recently introduced Terryl ® , a new biobased polyamide 56. Many recent biobased chemicals projects have unfortunately encountered challenges competing with existing petrochemical routes in the market. Commercialization of Terryl, a costcompetitive fibre with excellent textile performance and a significantly sizeable market, may bring back some investor confidence to the industry. Wallace Carothers invented the world’s first commercial synthetic fibre, polyamide 66 (PA66), in the 1930s. The polyamide structure was a synthetic analogue for the natural amide bonds in silk protein, replacing amino acids in silk with hexamethylenediamine (HMDA) and adipic acid produced by butadiene from naptha cracking. During World War II, PA66 served as a substitute for silk in parachutes and ropes, and its material properties and comfortable feel made it a preferred choice for women’s stockings. Polyamide 6 (PA6) was commercialized shortly after PA66, with a current combined global market over 6 million tons per annum. Industrial biotech companies have attempted to commercialize production of biobased materials such as PLA, PHA, 1,3-PDO, BDO/PBS, and PTT. All of these examples are polyesters. The only commercialized biobased polyamides have involved longer chain monomers for the specialty long chain polyamide markets. Amongst those, Cathay Biotech has taken over half the world’s dodecanedioic acid market within a decade, a rare example of a bioprocess successfully replacing the chemical process for an industrial chemical. To address the much larger shorter chain nylon market, Cathay Biotech has developed proprietary technology to commercially produce biobased pentamethylenediamine (DN5), a novel five carbon platform chemical. The DN5 has been polymerized with adipic acid to make Terryl, a biobased polyamide alternative to PA6 and PA66 (collectively referred to as nylon for the rest of this article). Terryl Molecular Structure PA66 is a high end textile fibre due to its many advantages such as strength, wear resistance, moisture absorbance, comfort, dyeability, and antistatic and flame retardant properties. Nevertheless, there is still room for improvement. For example, PA66 spinning costs are significant on top of the resin cost, mainly due to gel formation during spinning and qualification issues for dyed fibre. Despite the fact that PA66 dyes more readily than polyester, variability in dyeing reduces qualification rate for the highest AA textile grade, which increases costs in the forms of product downgrade, additional processing, or wastage. This variability is due to the structure of PA66, where chains line up with all internal amide hydrogen and oxygen moieties involved in hydrogen bonding (cf. Fig. 2). Because the internal hydrogen bonding sites in PA66 are all occupied, dyeing relies on the terminal ends of the polymer chains. These ends represent a small portion of the polymer and can be either amines or acids, making it a significant challenge to control end ratios for consistent dyeability. PA66 can theoretically be modified on a structural level to improve performance properties while maintaining the advantageous mechanical properties by partially offsetting a portion of the internal hydrogen bonding without completely disrupting the chain alignments. This can be done by changing 12 bioplastics MAGAZINE [05/14] Vol. 9

Fibers & Textiles H N N H O H N N H O H N Nylon 66 O H N N H O O H N N H O O H N O O O O O O N H N H N N N H H H X O O X O O X O N H N H N N N H H H O O Terryl ® PET PTT PA6 PA66 Terryl Fig. 2: PA 66 and Terryl Molecular Structure. Nylon 66 internal H and O sites are all involved in hydrogen bonding, so dyeing relies on amine ends of the polymer. Terryl has unbound intemal H and O sites (represented by green X’s), providing better dyeability, moisture absorbance, and wicking. the even carbon number diamine-even carbon number diacid nylon chemistry to an odd-even chemistry, e.g. replacing HMDA with DN5 (cf. Fig. 2). This would partially offset the internal hydrogen bonds, increasing the number of potential interaction sites for dye or water by over two orders of magnitude. This was predicted to improve dyeability, fluidity, moisture absorbance, wicking and by extension comfort while reducing gel formation and dyeing variability. The mechanical advantages such as strength and wear resistance of PA66 were expected to be preserved. Based on the molecular structure, Terryl was expected to have superior performance properties and reduced fibre spinning costs compared to PA66. Terryl Performance Properties Test data and customer feedback based on Terryl produced from Cathay Biotech’s initial 1000 tonnes per annum continuous production line confirmed the theoretical predictions. Terryl and nylon have comparable physical properties such as strength, density, and wear resistance. Using existing PA6 equipment, Terryl was successfully spun at high speed into common specifications for tricot swimwear fabric (44decitex/12 filaments per centimeter, Fully Drawn Yarn) and knitted pantyhose (33decitex/12filaments per centimeter, Draw Textured Yarn). As expected, Terryl’s fluidity also made direct polymerization melt-spinning possible for significant fibre cost savings. Compared with PA66, Terryl fabric had superior elastic recovery, moisture absorbance and wicking (∆MR), comfort, and dyeability. Terryl carpet fibres dyed as deeply at room temperature as PA66 fibre at high temperature. Under the same dyeing conditions, Terryl carpet, hosiery and seamless underwear dyed deeper and more color fast than nylon. By saving energy, chemical dye, and off-grade wastage, using Terryl improves both environmental footprint and fibre cost. Unexpectedly, Terryl also had significantly improved antistatic and flame retardant properties. In fact, Terryl was found to be self-extinguishing. density 1.40 1.33 1.14 1.14 1.14 Textile fiber strenght (cN/dtex) 3.8 3.0 4.2 4.5 4.3 - 4.4 Melting point (°C) 256 228 222 262 254 Wicking (ΔMR) poor poor 1.5 - 2.0 % 1.5 - 2.0 % > 3.0 % Fig. 3: Terryl Properties Comparison: Terryl is lightweight and strong like nylon, with superior wicking % 9.0 — 8.0 — 7.0 — 6.0 — 5.0 — 4.0 — 3.0 — 2.0 — 1.0 — 0.0 — Fig4: Terryl moisture absorbance closer to cotton than nylon, softer hand 20 — 30 — 40 — 50 — 60 — 70 — 80 — 90 — 100 — Polyester Nylon Terryl Cotton Temp (°C) Terryl PA66 Equilibrium Moisture Absorbance Fig. 5: Side by side dyeing trials for carpet fibre from Terryl’s and PA66. Terryl dyes at room temperature while PA66 requires high temperature bioplastics MAGAZINE [05/14] Vol. 9 13

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