ナイロン材料の特性：完全な技術リファレンス

Comprehensive technical data on nylon/PA material properties — thermal, mechanical, chemical resistance, electrical, and comparison tables across grades.

Overview of Nylon Material Properties

Nylon (polyamide) materials occupy a unique position in engineering thermoplastics: they offer the highest combination of strength, toughness, and wear resistance among non-reinforced plastics, while remaining processable on standard injection molding and extrusion equipment. This technical reference compiles the key properties that engineers, designers, and procurement specialists need when evaluating nylon for specific applications.

All data in this reference applies to conditioned material (23°C, 50% RH) unless otherwise noted. Moisture content significantly affects mechanical properties — dry-as-molded values can be 20-40% higher than conditioned values for unfilled nylon.

Mechanical Properties by Nylon Grade

Tensile Properties:

Key Observations: – PA6 has higher elongation (more ductile) but PA66 has higher strength – Glass fiber reinforcement (GF30 = 30% glass fiber) increases strength 2-2.5× but dramatically reduces ductility – PA46 outperforms all standard nylons in both strength and thermal resistance, at higher cost – PA12 is the softest and most flexible — lowest strength but best impact resistance at low temperatures

Thermal Properties

Thermal performance is often the deciding factor in grade selection:

HDT Notes: – Heat Deflection Temperature (HDT) measures temperature at which a specimen deflects 0.25mm under specified load – Glass fiber reinforcement dramatically improves HDT — GF30 grades achieve 2-3× the HDT of unfilled grades at 1.82 MPa – PA66-GF30 at 1.82 MPa: 250°C — suitable for under-hood automotive applications – PA12’s low HDT limits use to room-temperature applications

Moisture Absorption and Environmental Effects

Nylon’s moisture absorption is a critical consideration — more so than almost any other engineering plastic:

Impact of Moisture on Properties: – Tensile strength decreases 15-25% at saturated condition vs. dry-as-molded – Impact resistance INCREASES with moisture absorption (nylon becomes tougher when conditioned) – Dimensional change: PA6 swells approximately 0.4% per 1% moisture absorbed — must be accounted for in precision parts – Electrical insulation properties degrade significantly with moisture (dielectric constant increases 2×)

Design Recommendations: – PA12 for parts exposed to humid environments or water immersion – Dry-as-molded properties for designing dimensional tolerances in molds – Condition parts to equilibrium before measuring critical dimensions

Chemical Resistance of Nylon

Nylon’s chemical resistance profile determines suitability for industrial environments:

Good Resistance (no significant attack at 23°C): – Aliphatic hydrocarbons (gasoline, mineral oils, diesel) – Alcohols (methanol, ethanol, isopropanol) – Esters and ketones (acetone, MEK — limited exposure) – Weak acids (acetic acid, citric acid — verify case-by-case) – Dilute alkalis and salts

Poor Resistance (attack or degradation): – Concentrated mineral acids (HCl, H2SO4, HNO3) — rapid hydrolysis – Strong oxidizing agents (hydrogen peroxide >10%) – Phenol and formic acid — dissolves nylon – Calcium chloride (desiccant) — causes stress cracking – Strong alkalis at elevated temperature

Specialty Grades for Chemical Service: – PA12 for automotive fuel lines — resistant to aromatic fuels and alcohol blends – PA6I/6T (transparent nylon) for chemical contact applications requiring clarity – Glass-filled grades for chemical pump housings and valve components

Electrical and Flammability Properties

Electrical Properties (at 50% RH conditioning):

Flammability Ratings:

グレード	UL94 Rating	Oxygen Index (%)
-	-	PA6
HB	24	PA66
HB	24	PA12
HB	22	PA6-GF30
HB	23	FR grades
V-0	32+

Nylon burns with a self-sustaining flame and drips. For electrical enclosures or components requiring flame retardancy, specify FR (flame retardant) grades — typically PA66 with halogen or phosphorus-based flame retardants.