{"id":4222,"date":"2026-04-24T01:03:14","date_gmt":"2026-04-24T01:03:14","guid":{"rendered":"https:\/\/nylonplastic.com\/?p=4222"},"modified":"2026-06-10T06:01:35","modified_gmt":"2026-06-10T06:01:35","slug":"nylon-moisture-absorption-properties-overview","status":"publish","type":"post","link":"https:\/\/nylonplastic.com\/fr\/nylon-moisture-absorption-properties-overview\/","title":{"rendered":"Moisture Absorption in Nylon: Effects, Measurement, and Control"},"content":{"rendered":"
\"Moisture
Moisture Absorption in Nylon: Effects, Measurement, and Control \u2014 Nylon Plastic<\/figcaption><\/figure>\n

Why Moisture Absorption is the Defining Characteristic of Nylon<\/h2>\n

No other engineering thermoplastic absorbs moisture as dramatically as nylon. PA6 can absorb up to 9.5% by weight<\/strong> at saturation \u2014 more than any other common engineering plastic. Even PA66, with its tighter molecular packing, reaches 8.5%<\/strong>. PA12 reaches only 1.5%<\/strong>, making it the nylon of choice for wet environments.<\/p>\n

This moisture absorption is not a defect \u2014 it is a fundamental property arising from the hydrogen-bonding amide groups in the polyamide chain. Water molecules penetrate the amorphous regions of the polymer and plasticize it, fundamentally altering mechanical, thermal, and dimensional properties.<\/p>\n

For buyers and engineers specifying nylon, understanding moisture effects is not optional. Every nylon datasheet value \u2014 tensile strength, modulus, impact resistance \u2014 is measured on conditioned specimens. The same part, tested dry-as-molded, can show tensile strength 40% higher but impact resistance 70% lower than conditioned values.<\/p>\n

How Nylon Absorbs Moisture: The Science<\/h2>\n

Moisture absorption in nylon follows a classic Fickian diffusion process with two phases:<\/p>\n

\"How
How Nylon Absorbs Moisture: The Science \u2014 Nylon Plastic<\/figcaption><\/figure>\n
    \n
  • Phase 1 (rapid)<\/strong>: Surface saturation within hours \u2014 parts appear “wet” but interior is still dry. This is the most dangerous phase for dimensional instability and surface blistering.<\/li>\n
  • Phase 2 (slow)<\/strong>: True equilibrium through bulk diffusion \u2014 can take weeks or months for thick sections (>10mm wall thickness)<\/li>\n<\/ul>\n

    At 50% relative humidity (23\u00b0C), PA6 reaches approximately 2.5% moisture content within 24 hours. Full saturation at 95% RH can take 2-4 weeks. The actual equilibrium moisture content depends on:<\/p>\n

    \n\n\n\n\n\n\n\n\n\n\n
    Nylon Grade<\/th>\nMax Moisture Absorption (%)<\/th>\nEquilibrium at 50% RH<\/th>\nEquilibrium at 95% RH<\/th>\n<\/tr>\n<\/thead>\n
    PA6<\/td>\n9.0-9.5%<\/td>\n2.5-3.0%<\/td>\n8.5-9.0%<\/td>\n<\/tr>\n
    PA66<\/td>\n8.0-8.5%<\/td>\n2.0-2.5%<\/td>\n7.5-8.0%<\/td>\n<\/tr>\n
    PA12<\/td>\n1.4-1.6%<\/td>\n0.7-0.9%<\/td>\n1.3-1.5%<\/td>\n<\/tr>\n
    PA6-GF30<\/td>\n6.0-7.0%<\/td>\n1.5-2.0%<\/td>\n5.5-6.5%<\/td>\n<\/tr>\n
    PA66-GF30<\/td>\n5.0-6.0%<\/td>\n1.3-1.8%<\/td>\n4.5-5.5%<\/td>\n<\/tr>\n
    PA46<\/td>\n7.0-7.5%<\/td>\n2.0-2.3%<\/td>\n6.5-7.0%<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

    Effects on Mechanical Properties<\/h2>\n

    Moisture absorption simultaneously improves some properties while degrading others \u2014 a trade-off that must be understood for accurate part design.<\/p>\n

    \"Effects
    Effects on Mechanical Properties \u2014 Nylon Plastic<\/figcaption><\/figure>\n
    \n\n\n\n\n\n\n\n\n\n\n
    Propri\u00e9t\u00e9<\/th>\nDry As Molded<\/th>\nConditioned (50% RH)<\/th>\nChange<\/th>\n<\/tr>\n<\/thead>\n
    R\u00e9sistance \u00e0 la traction (MPa)<\/td>\n80-90<\/td>\n55-65<\/td>\n-28%<\/td>\n<\/tr>\n
    Tensile Modulus (MPa)<\/td>\n3000-3300<\/td>\n1800-2100<\/td>\n-35%<\/td>\n<\/tr>\n
    Allongement \u00e0 la rupture<\/td>\n40-60%<\/td>\n150-250%<\/td>\n+250%<\/td>\n<\/tr>\n
    Izod Impact (kJ\/m\u00b2)<\/td>\n3-5<\/td>\n6-10<\/td>\n+100%<\/td>\n<\/tr>\n
    Module de flexion (MPa)<\/td>\n2800-3100<\/td>\n1500-1800<\/td>\n-40%<\/td>\n<\/tr>\n
    HDT (1.82 MPa, \u00b0C)<\/td>\n65-75<\/td>\n55-65<\/td>\n-15\u00b0C<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

    Effects on Dimensional Stability<\/h2>\n

    Moisture absorption causes dimensional changes that can be significant for precision parts. The dimensional change is not linear \u2014 it follows a differential swelling pattern between skin (which equilibrates first) and core (which remains dry).<\/p>\n

    \"Effects
    Effects on Dimensional Stability \u2014 Nylon Plastic<\/figcaption><\/figure>\n
      \n
    • Linear expansion<\/strong>: PA6 expands approximately 0.15-0.20% per 1% moisture absorbed in the flow direction, and 0.40-0.50% in the transverse direction<\/li>\n
    • Anisotropic swelling<\/strong>: Similar to shrinkage anisotropy, moisture swelling is greater perpendicular to the mold flow direction<\/li>\n
    • Warpage from differential drying<\/strong>: Parts dried unevenly after conditioning can warp as surface and core dry at different rates<\/li>\n
    • Threaded inserts<\/strong>: Metal inserts in nylon do not change dimension with humidity \u2014 dimensional changes occur only in the nylon surrounding the insert, creating stress on the interface<\/li>\n<\/ul>\n

      Measurement Methods: How to Measure Nylon Moisture Content<\/h2>\n

      Accurate moisture measurement is essential for quality control in nylon processing and for verifying material condition before use.<\/p>\n

      \"Measurement
      Measurement Methods: How to Measure Nylon Moisture Content \u2014 Nylon Plastic<\/figcaption><\/figure>\n
      \n\n\n\n\n\n\n\n\n\n
      M\u00e9thode<\/th>\nPrinciple<\/th>\nAccuracy<\/th>\nTime<\/th>\nBest Use<\/th>\n<\/tr>\n<\/thead>\n
      Loss on Drying (LOD)<\/td>\nWeigh before\/after oven drying at 103\u00b0C<\/td>\n\u00b10.1%<\/td>\n2-4 hours<\/td>\nQuick production QC<\/td>\n<\/tr>\n
      Karl Fischer Titration<\/td>\nChemical reaction with water molecules<\/td>\n\u00b10.01%<\/td>\n10-20 min<\/td>\nPrecision verification<\/td>\n<\/tr>\n
      Coulometric KF<\/td>\nElectrolytic Karl Fischer<\/td>\n\u00b10.001%<\/td>\n15-30 min<\/td>\nR&D, spec testing<\/td>\n<\/tr>\n
      Moisture Analyzer<\/td>\nAutomated LOD with integrated balance<\/td>\n\u00b10.05%<\/td>\n20-40 min<\/td>\nInline production QC<\/td>\n<\/tr>\n
      Dew Point Hygrometer<\/td>\nEquilibrium with desiccant<\/td>\n\u00b10.3%<\/td>\n30-60 min<\/td>\nDryer monitoring<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

      Control Strategies: Drying and Storage Best Practices<\/h2>\n

      Effective moisture control requires a systematic approach from material storage through processing:<\/p>\n

      \"Control
      Control Strategies: Drying and Storage Best Practices \u2014 Nylon Plastic<\/figcaption><\/figure>\n
        \n
      • Desiccant dryer<\/strong>: The standard for nylon drying. Use desiccant with dew point below -40\u00b0C (ideally -70\u00b0C). Maintain air dew point of -40\u00b0C throughout the drying cycle. Target 0.1-0.2% residual moisture for PA66, 0.2% for PA6.<\/li>\n
      • Drying temperatures<\/strong>: 80\u00b0C for PA6 and PA66 (higher temperatures risk oxidative degradation), 70-75\u00b0C for PA12<\/li>\n
      • Drying time<\/strong>: 4-6 hours minimum for properly sealed material; 8-12 hours for material exposed to humid air or with wall thickness >15mm<\/li>\n
      • Hopper design<\/strong>: Use sealed hoppers with nitrogen purge to prevent re-absorption during production runs<\/li>\n
      • Material shelf life after drying<\/strong>: Once dried, nylon re-absorbs moisture at approximately 0.1% per hour at 23\u00b0C\/50% RH \u2014 dried material must be used within 2-4 hours or re-dried<\/li>\n<\/ul>\n
        \n

        FAQ<\/h2>\n
        \nHow do you know whether Moisture Absorption in Nylon: Effects, Measurement, and Control fits a part?<\/summary>\n
        \n

        Moisture Absorption in Nylon: Effects, Measurement, and Control fits a part when its load capacity, temperature range, moisture exposure, wear behavior, and processing method match the real service conditions.<\/p>\n<\/div>\n<\/details>\n

        \nWhat properties should be checked for Moisture Absorption in Nylon: Effects, Measurement, and Control?<\/summary>\n
        \n

        V\u00e9rifier la r\u00e9sistance, la rigidit\u00e9, la r\u00e9sistance aux chocs, la r\u00e9sistance \u00e0 la chaleur, l'absorption d'humidit\u00e9, la stabilit\u00e9 dimensionnelle, le frottement, l'usure et la compatibilit\u00e9 chimique.<\/p>\n<\/div>\n<\/details>\n

        \nWhat is the biggest selection risk for Moisture Absorption in Nylon: Effects, Measurement, and Control?<\/summary>\n
        \n

        Le plus grand risque est de choisir \u00e0 partir d'une fiche technique sans tenir compte de l'environnement r\u00e9el, de la m\u00e9thode de traitement, de la g\u00e9om\u00e9trie de la pi\u00e8ce et de l'utilisation \u00e0 long terme.<\/p>\n<\/div>\n<\/details>\n

        \nWhen should Moisture Absorption in Nylon: Effects, Measurement, and Control be tested before production?<\/summary>\n
        \n

        Les essais sont recommand\u00e9s lorsque la pi\u00e8ce est soumise \u00e0 une charge, \u00e0 la chaleur, \u00e0 des produits chimiques, \u00e0 l'humidit\u00e9, \u00e0 des tol\u00e9rances serr\u00e9es, \u00e0 des exigences r\u00e9glementaires ou \u00e0 un nouvel environnement de travail.<\/p>\n<\/div>\n<\/details>\n<\/div>\n\t\t\t

        \n\t\t\t