Polyamide (PA) covers a family of various PA types and offers an excellent cost to performance ratio. Virgin PA is commonly used in automotive, electronics, packaging, and textile applications, while recycled PA is mostly used in automotive parts, flooring materials, composite lumbers, and house textiles.
PA has high strength, toughness, and stiffness, good abrasion resistance and chemical resistance as well as a high barrier to oxygen, fats, and oils. On the other hand, PA is a hydrophilic plastic that absorbs water. How pronounced this property is depends on the type of PA used and must be taken into account during processing and application.
Overall, PA offers an excellent price-performance ratio and is usually processed by injection molding, laser sintering, or used for the production of films and fibers. Depending on the type, PA is used as an unfilled resin or with fillers or reinforcing materials (minerals, glass beads, glass fibers) to produce plastic parts for the automotive, electrical, and electronics or general industry.
Typical applications are motor covers, drive trains, switches, industrial CEE connectors, power tools, railway pads, ski fasteners, castors, connectors, housings, fasteners, screw anchors, air duct systems, oil sensors, fastening systems, casings, composite wood, technical or apparel textiles, insulating panels, etc. Besides non-food grades, in some cases, PA can also be used in food-grade packaging.
Virgin PA is available in different types, which differ in their structure, due to the monomers used, and the length of the polymer chain. The most commonly used types are PA6 and PA6.6, which are known for their high durability and strength. Other types available are PA4.6, PA6.10, PA6.12, PA10.10, PA12, or a bio-based PA11. All PA types are technically recyclable.
The currently commercially available PA recyclates can be produced by mechanical, physical (solvent-based), or chemical recycling. Most of the commercially available PA recyclates are based on post-industrial waste or post-consumer waste from the packaging industry. The post-industrial PA recyclates have a very high degree of purity and their properties can often match those of the virgin PA. Therefore, these recyclates have good quality and stability. This enables their use for high-value applications.
In addition to the unfilled PA recyclates, there are recyclates with various proportions of fillers like glass fibers, glass beads, or minerals. The processing and material properties of PA recyclates depend on the PA type as well as the recycling process and can be further improved by additives such as heat, light or processing stabilizers, fillers, and reinforcing materials, nucleating agents, flow improvers, chain extenders, and cutters, etc.
The PA raw materials are usually non-food grade waste. The post-industrial feedstock for various PA types mostly comprises pre-sorted waste produced during the manufacture of PA-based plastic articles by injection molding. This feedstock often contains PA with varying levels of fillers and reinforcing materials in the range of 15 to 50 wt%. Other sources include fiber waste, chips from cast polyamides (PA6, PA12), and unfilled materials from extrusion processing (e.g. packaging films).
Normally, unfilled or filled/reinforced PA recyclates are available as regrind, regranulate, or recompound.