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Technical guide

Glass-Fiber-Reinforced PA6 and PA66 Selection Guide

Glass fiber percentage is only one input in selecting a reinforced PA6 or PA66 compound. Polymer matrix, fiber length and retention, interface, heat stabilization, impact or flame modification, moisture state, flow orientation, weld lines, wall thickness, gate design, surface requirements, and processing history all influence the finished part. This guide explains how to use Taiyi Polymer's 15%, 30%, and 50% glass-fiber catalogue directions as a screening ladder while keeping the final decision tied to molded-part performance.

Choose the matrix at a matched fiber level

Compare PA6 and PA66 with the same reinforcement level, test basis, and defined dry or conditioned state before changing the glass-fiber percentage.

Raise reinforcement only against a measured gap

Balance the required load response with flow, orientation, weld lines, warpage, surface, toughness, equipment risk, and molded-part validation.

Define the Load Case and Failure Limit

Map every static, cyclic, impact, assembly and fastener load, including direction, duration, temperature and frequency. Define allowable deflection, creep, permanent set, fatigue life, impact condition and failure location. Also record humidity, chemicals, electrical or flame requirements, appearance, weight, wall thickness, critical dimensions and the intended validation method.

A request for higher stiffness is incomplete unless the part-level target is measurable. Increasing reinforcement may improve one load direction while creating a new weld-line, warpage, surface, toughness, flow or equipment risk. Start with the lowest-complexity grade direction that can plausibly meet the full acceptance criteria.

Understand What the Glass Fiber Level Does and Does Not Define

Within a related grade series, increasing glass fiber commonly raises stiffness and load response. The actual result also depends on fiber length distribution after compounding and molding, fiber-matrix adhesion, polymer viscosity, modifiers, specimen orientation, moisture state and test temperature. Two compounds with the same nominal fiber percentage are therefore not automatically equivalent.

Higher reinforcement can change melt flow, surface texture, fiber visibility, weld-line response, notched sensitivity, ejection, dimensional directionality and wear on screws, barrels, hot runners and tools. It can also change contact behavior against mating parts. Use the percentage to narrow the catalogue, then compare complete grade data and the intended production system.

  • Fiber content and test method, not only the grade name
  • Dry and conditioned mechanical values at relevant temperatures
  • Flow family, heat stabilization, impact or flame modification and color
  • Surface, wear, weld-line, equipment and document requirements

Choose PA6 or PA66 Before Finalizing the Fiber Level

PA6 and PA66 create different moisture, thermal and processing directions. Define the service and inspection conditioning states before comparing stiffness, strength or dimensions. A PA66 glass-fiber grade may provide a higher melting and heat-performance direction than a comparable PA6 grade, while exact toughness, flow, appearance and process feasibility remain grade-specific.

Use matched reinforcement levels for the first comparison, then adjust the percentage only when the part requirement justifies it. For example, compare PA6 GF30 with PA66 GF30 before comparing PA6 GF15 with PA66 GF50. This separates polymer-matrix effects from reinforcement-level effects and produces a clearer trial plan.

Design Around Fiber Orientation and Weld Lines

Short glass fibers align through the injection-molding flow field. Stiffness, strength and shrinkage can therefore differ along and across local flow directions. The relationship between gate, flow, weld lines and the load path is part of the material decision, not a detail to address after the grade is chosen.

Review gate position and size, wall transitions, ribs, bosses, inserts, fasteners, corners, end-of-fill zones and critical dimensions. Avoid placing a governing load across an uncontrolled weld line. Use molding simulation or a short-shot study where useful, then confirm orientation-sensitive behavior through molded specimens or the finished part.

  • Primary load direction compared with expected local fiber orientation
  • Weld lines, notches, inserts, screw bosses and sharp section changes
  • Longitudinal and transverse shrinkage, flatness and cavity variation
  • Surface acceptance zones, exposed fiber and mating-part contact

Use the Catalogue Ladder as a Screening Tool

Taiyi Polymer lists PA6 and PA66 glass-fiber directions at multiple reinforcement levels. The examples below show how published tensile, flexural, water-absorption and HDT values change within selected catalogue grades. They provide a structured shortlist, not an instruction to select the highest value.

All figures are grade-specific typical data. Fiber content is reported to ISO 1172, tensile stress to ISO 527, flexural modulus to ISO 178, water absorption at 23°C and 50% RH to ISO 62, and HDT at 1.8 MPa to ISO 75 in the current catalogue. Confirm the latest TDS and conditioning basis before specification.

Selected Taiyi glass-fiber grade ladder

Grade directionMechanical catalogue valuesConditioning and heat references
EAG115 · PA6 GF15Tensile 120 MPa · Flexural modulus 5,500 MPaWater absorption 1.3-1.7% · HDT 205°C
EAG130 · PA6 GF30Tensile 185 MPa · Flexural modulus 8,800 MPaWater absorption 1.1-1.5% · HDT 210°C
EAG150U · PA6 GF50Tensile 230 MPa · Flexural modulus 14,500 MPaWater absorption 0.8-1.2% · HDT 210°C
EAG215 · PA66 GF15Tensile 130 MPa · Flexural modulus 5,400 MPaWater absorption 0.8-1.2% · HDT 240°C
EAG230 · PA66 GF30Tensile 200 MPa · Flexural modulus 9,000 MPaWater absorption 0.5-0.9% · HDT 250°C
EAG250 · PA66 GF50Tensile 240 MPa · Flexural modulus 14,800 MPaWater absorption 0.3-0.7% · HDT 250°C

Confirm Molding Feasibility and Equipment Readiness

Review drying and material transfer, machine capacity, screw and barrel condition, residence control, runner and gate restrictions, venting, fill balance, packing, cooling, ejection and surface requirements for the exact grade. Higher-fiber compounds may require a different feasibility review from the lower-fiber baseline and can increase wear on material-contact and tooling surfaces.

During trials, record material condition, lot, fill time, transfer, pressure, cushion, part weight, mold-surface temperatures, cavity balance, cycle, appearance and visible fiber or weld-line effects. Establish a stable process window for each candidate instead of forcing all grades through one inherited setting sheet.

Release the Molded Part at the Required Conditioning State

Measure cavity-marked parts after agreed conditioning intervals using fixed datums and methods. Check dimensions, warpage, surface, assembly, fastener retention, weld-line performance and any load-direction dependence. Compare dry, conditioned and service-relevant results where the application requires them.

Complete sustained-load, fatigue, impact, temperature, humidity, chemical, electrical, flame or other project tests on the intended geometry. Release the exact grade, color and process only after the original failure limit, production capability and document requirements are closed.