Nylon 6/66 (24993-04-2) Physical and Chemical Properties
Nylon 6/66
Engineering polyamide copolymer supplied as pellets for extrusion and molding, offering a balance of mechanical strength, thermal performance and chemical resistance for industrial manufacturing and compound formulation.
| CAS Number | 24993-04-2 |
| Family | Polyamide copolymers (Nylon) |
| Typical Form | Pellets or granules for molding/extrusion |
| Common Grades | EP |
Nylon 6/66 is a copolymeric polyamide produced by the condensation of caprolactam-derived nylon-6 units with hexamethylenediamine/adipic-acid-derived nylon-66 units. Structurally it is a segmented polyamide containing repeating amide (–CONH–) linkages derived from azepan-2-one (caprolactam), hexane-1,6-diamine (hexamethylenediamine) and hexanedioic acid (adipic acid). The copolymer architecture produces a semicrystalline thermoplastic in which amide groups form interchain hydrogen bonds that govern mechanical strength, melting behavior and moisture uptake.
Electronically, the polymer chain presents multiple hydrogen-bond donors and acceptors concentrated at the amide moieties; these polar sites give the material moderate polarity and affinity for water and polar solvents. The polymer is not ionizable in the typical pH range; hydrolytic cleavage of amide bonds requires prolonged exposure to strong acid or base and/or elevated temperature. Thermal processing produces typical polyamide degradation pathways (chain scission, release of monomeric amines and acids) rather than rapid oxidation; UV and strong oxidants accelerate surface degradation.
Functionally, Nylon 6/66 is an engineering thermoplastic widely used for fibers, molded components, films and food-contact articles where a balance of tensile strength, chemical resistance and thermal performance is required. It is also processed as pellets or granules for extrusion and injection molding. Common commercial grades reported for this substance include: EP.
Overview and Composition
Qualitative Composition
Nylon 6/66 is a copolymer comprised of three component repeat units: azepan-2-one (caprolactam, nylon-6 unit), hexane-1,6-diamine (hexamethylenediamine) and hexanedioic acid (adipic acid, nylon-66 unit). The provided computed molecular formula for a representative covalently-bonded unit is C18H37N3O5 with a computed molecular weight of \(375.5\,\mathrm{g}\,\mathrm{mol}^{-1}\). The record lists the components explicitly as azepan-2-one; hexane-1,6-diamine; hexanedioic acid and indicates a covalently-bonded unit count of 3, consistent with a multicomponent polymeric repeat.
Computed molecular descriptors relevant to the polymer repeat (as supplied) include hydrogen-bond donor count 5, hydrogen-bond acceptor count 7, rotatable bond count 10, topological polar surface area \(156\,\text{Å}^2\), exact/monoisotopic mass 375.27332129 and complexity 236. The formal charge is 0 and the heavy atom count is 26. These descriptors reflect the polar, hydrogen-bonding-rich nature of the repeat unit and are useful for predicting intermolecular interactions, moisture uptake and solvation behavior of small oligomeric fragments and monomers.
Appearance and Typical Form
Nylon 6/66 is commercially supplied in pellet or granule form for melt-processing and as staple or filament fiber for textile applications. Typical finished materials are semicrystalline, white to off‑white in appearance. In industrial practice the material is encountered as molded parts, extruded profiles, films, monofilaments and spun fibers; "Nylon 6/66, pellets" is a commonly used commercial descriptor. Pellets and dried granules are the usual feedstock for injection molding and extrusion operations.
Chemical Properties
Reactivity and Corrosive Behavior
The polymer backbone consists of amide bonds that confer relative chemical stability under neutral conditions but susceptibility to hydrolytic cleavage under prolonged exposure to strong acids or bases, especially at elevated temperature. Hydrolysis yields low-molecular-weight amines and carboxylic acids (e.g., release of caprolactam, adipic acid, hexamethylenediamine under severe conditions). Computed hydrogen-bonding descriptors (donor count 5 and acceptor count 7) and a topological polar surface area of \(156\,\text{Å}^2\) indicate strong interchain hydrogen bonding, which governs melting behavior and moisture absorption.
The material is not strongly corrosive; intact polymer is chemically robust toward hydrocarbons and many nonpolar organics. Thermal degradation above typical processing temperatures produces decomposition products (amines, ammonia, carboxylic fragments, and low-molecular-weight volatiles) that can be corrosive or irritating in confined equipment if not properly controlled. Oxidative and photochemical attack (UV) can cause surface embrittlement and loss of mechanical properties over time.
Compatibility and Incompatibilities
Nylon 6/66 is broadly compatible with many engineering materials and resists swelling in aliphatic hydrocarbons and most dilute aqueous media. It is, however, incompatible with strong acids, strong bases and concentrated oxidizing agents which promote hydrolysis, chain scission or oxidative degradation. Certain polar solvents (e.g., concentrated phenols, strong acids such as concentrated sulfuric acid, or concentrated formic acid) can cause swelling, dissolution or chemical attack and should be avoided. Prolonged contact with hot water or steam can accelerate hydrolytic degradation and reduce molecular weight. For material selection, consider the service environment (temperature, chemical exposure, UV, mechanical stress) because these factors control long-term compatibility.
Usage and Safety
Industrial and Commercial Use Contexts
Nylon 6/66 is an engineering thermoplastic used extensively in textile fibers, molded components, films, monofilaments and technical parts requiring high tensile strength and abrasion resistance. It is supplied as pellets for extrusion and injection molding and as fibers for textiles and industrial yarns. The polymer is also listed for use in food-contact applications under applicable food-contact regulatory provisions; applicable regulatory document numbers are 177.1200, 177.1395, 177.1500 and 177.2470 (U.S. food-contact polymer provisions). Typical selection criteria in industry include mechanical performance, thermal resistance, chemical resistance and processability (drying requirements prior to melt processing).
Hazards and Handling Considerations
As a bulk polymer, Nylon 6/66 generally presents low acute toxicity, but specific hazards arise during processing and end‑of‑life handling. Key considerations: - Dust control: machining, grinding or pellet handling can generate respirable dust; use dust control and respiratory protection where appropriate. - Thermal decomposition: molding or overheating can produce volatile amines and acidic species; provide adequate ventilation and fume control during processing and in the event of fire. - Moisture sensitivity: the polymer absorbs moisture which can affect melt viscosity and final part properties; drying prior to melt processing is commonly required to avoid hydrolytic degradation and surface defects. - Skin and eye contact: molten polymer can cause thermal burns; standard PPE (gloves, eye protection) is recommended in processing operations. - Static and handling: pellets can produce dust and static charge; grounding, antistatic measures and appropriate material handling protocols reduce risk.
For storage, keep material dry, protected from prolonged UV exposure and segregated from strong oxidizers and corrosive chemicals. For detailed hazard, transport and regulatory information, users should refer to the product-specific Safety Data Sheet (SDS) and local legislation.
