Polyram PlusTek PD305G6 is designated as a 30% glass-fiber-reinforced polyamide 12 injection molding compound. The continuous phase is polyamide 12, while the discontinuous reinforcement is typically E-glass chopped strand with a silane-based coupling system; the exact fiber diameter and sizing are controlled by the supplier’s formulation. The glass weight fraction is 30%, which corresponds to a glass volume fraction of approximately 0.15–0.20 depending on component densities and void content. The grade is supplied as cylindrical or granular pellets for conventional reciprocating-screw injection molding machines. Relative to unfilled PA12, this filled system moves from ductile yielding to a stiff, low-elongation failure mode. Relative to a 30% glass-filled PA66, the compound normally provides lower saturated water uptake and lower density but also a lower heat deflection temperature because the PA12 crystalline melting point is lower than that of PA66. These differences are the key selection variables for connectors, clamps, housings, and fluid-contact components. The performance ranges in this document reflect the engineering envelope for 30% glass-filled PA12 compounds; they are not certified lot values, and the supplier’s certificate of analysis should govern design and incoming inspection.

How does 30% glass fiber loading shift the failure envelope relative to unfilled PA12?

The dominant effect of glass fiber reinforcement is an increase in tensile modulus and a reduction in plastic elongation. In a dry-as-molded state, 30% glass-filled PA12 typically exhibits a tensile modulus of 7,500–9,500 MPa under ISO 527-1/-2, compared with 1,400–1,800 MPa for unfilled PA12. Tensile strength at break is generally 120–145 MPa, but elongation at break is reduced to 2–4%. Unfilled PA12 can reach 150–300% elongation at break. The collapse of post-yield deformation eliminates living hinges and high-retention snap-fit arms unless the part is designed specifically for stiffness-driven loading and low strain. Flexural modulus under ISO 178 is commonly 7,000–9,000 MPa, and flexural strength is at or slightly above tensile strength. Notched Charpy impact strength at 23°C according to ISO 179-1/1eA is commonly 8–15 kJ/m². At -30°C, filled polyamide becomes notch-sensitive, and impact values can decline by 30–50%; low-temperature clips, cable ties, and fuel-line retainers therefore require molded-bar impact testing before release.

Thermal performance remains constrained by the PA12 matrix. Heat deflection temperature at 1.80 MPa measured under ISO 75-1/-2 is typically 160–175°C, while the PA12 melting peak measured by ISO 11357-3 is approximately 175–180°C. A 30% glass-filled PA66 compound, by comparison, commonly exhibits HDT values of 240–255°C. The lower HDT does not mean immediate failure at 160°C; it indicates that load-bearing stiffness will creep near the crystalline melting region. Continuous-use temperature should be supported by ISO 899-1 creep modulus data rather than by HDT alone.

The table is a comparative rank-order matrix rather than a product datasheet. It shows that PD305G6 is positioned for stiffness requirements near 30% glass-filled PA66 but with water absorption below that of PA66. The grade cannot substitute for PA66 GF30 in high-temperature load-bearing structures because of lower tensile strength and lower HDT. Conversely, it is selected when moisture-related dimensional movement and chloride stress cracking control field failure. Glass-reinforced PA12 also has lower density than glass-reinforced PA66, which reduces part mass in the same wall thickness. When comparing with glass-reinforced PBT, PA12 GF30 typically has better low-temperature ductility but lower continuous-use temperature; comparisons against PPA show a similar trade-off: PA12 GF30 has lower HDT and tensile strength, but often better zinc chloride resistance and lower saturated moisture uptake. These comparative claims require identical specimen geometry, conditioning, and test speed when used for material substitution.

Desiccant drying is a process failure boundary, not a recommendation. At ambient relative humidity above 60%, pellets should be dried at 80–90°C for 4–8 h in a desiccant dryer with a dew point no higher than -30°C. Residual moisture should be below 0.10% by mass, measured by ISO 15512. The hopper loader and feed throat should be dry or blanketed with dried air. Moisture produces splay, silver streaks, and weak weld lines. Although PA12 is less hydrolysis-sensitive than PA66, glass sizing can retain surface moisture, making visual dryness of pellets an unreliable control.

Melt temperature should be maintained between 240°C and 270°C. The lower limit is set by melt viscosity and thin-wall filling; the upper limit by PA12 matrix degradation and silane-sizing breakdown. If the cycle is interrupted above 270°C, the barrel should be purged and the temperature reduced. Mold temperature is normally 40–80°C. A mold below 40°C produces a thick frozen skin, low gloss, and reduced crystallinity; a mold near 80°C improves glass wetting and dimensional stability but increases cooling time by an estimated 10–20% depending on wall thickness and mold alloy. Hot runner systems can be used with glass-filled PA12, but dead spots and long residence times in heated manifolds must be avoided because glass-filled melts degrade preferentially at stagnation points.

Screw and barrel wear are production-scale constraints. The screw should have an L/D of at least 20:1 and a compression ratio of 2.0:1–2.5:1. The barrel, screw, check ring, and nozzle should be hardened or bimetallic. Shot weight drift above 0.3% may indicate check-ring leakage caused by glass-fiber abrasion. Fiber attrition is measurable: glass fiber length in molded parts is often 30–50% lower than in the compounded pellet because of screw shear, back pressure, gate shear, and cavity flow. Higher back pressure improves melt homogeneity but increases fiber breakage; lower back pressure preserves fiber length but may yield poor dispersion. Molded tensile strength under ISO 527-1/-2 should be used to lock back pressure, screw speed, and injection speed for a given tool. A tensile strength at the low end of the expected range can indicate excessive fiber attrition or poor fiber dispersion.

Injection speed should be medium to fast for thin-wall sections, but high shear at the gate can fracture glass fibers and reduce local tensile strength. The shear rate at the gate is a function of flow rate and gate radius; for a 2 mm circular gate, filling times below 0.5 s can push shear rates above 10,000 s^-1, increasing fiber breakage. If the part has thin walls, fast injection is needed to avoid premature freeze-off; this conflict should be resolved by using multiple gates or larger gate thickness rather than by excessive injection pressure. Packing pressure should be applied until the gate freezes, but overpacking raises molded-in stress and increases warpage. Cavity pressure sensors can monitor gate freeze-off and allow transfer at a consistent viscosity; for glass-filled PA12, transfer from filling to packing should occur before the flow front slows enough to allow fiber agglomeration at the melt front. Short shots are not a reliable indication of melt temperature, because glass-filled PA12 can fill but pack poorly when mold temperature is too low.

Shrinkage is anisotropic and must be addressed before steel cutting. On an edge-gated plaque molded according to ISO 294-4, flow-direction shrinkage for 30% glass-filled PA12 is commonly 0.1–0.3%, while transverse shrinkage is 0.6–0.9%. This difference generates warpage in flat housings, ribbed plates, and long clips. Gate placement should create symmetric fiber orientation and avoid a single flow front across a large flat section. Weld lines are structurally weak because glass fibers do not bridge the weld plane; double-gated ISO 527-2 tensile specimens may retain only 40–60% of the bulk tensile strength. Weld lines should be placed away from tensile or impact load paths. Where a weld line is unavoidable, overflow wells, higher melt and mold temperature within the specified window, and adequate venting can improve weld-line integrity, but they do not restore bulk properties.

Incoming material control should include melt viscosity or MVR, glass content verification by ash content per ISO 3451-1, and moisture content. Glass content below specification reduces tensile modulus and HDT; glass content above specification increases viscosity and screw wear. The ash content for a 30% glass-filled PA12 should be checked against the supplier’s certificate, but the method must be calibrated for glass sizing and mineral additives. Moisture content at incoming should be recorded before drying; a high initial moisture level may require longer drying or a second dryer pass. Lot-to-lot viscosity variation can alter filling and packing; molders with tight dimensional tolerances should record melt pressure integral or transfer position for each lot and adjust transfer point accordingly. Regrind use is limited by fiber attrition and thermal history. A common production limit for glass-filled PA12 is 20–30% regrind when impact and weld-line properties are monitored; each melt pass reduces fiber length further and can shift tensile strength downward. Regrind must be dry and free of foreign polymer contamination. Mixing with PA66, PA6, or acetal regrind is not acceptable because incompatible phases delaminate and reduce weld-line strength.

When chloride-induced stress cracking and moisture-driven dimension change dominate rejection rates

Polyram PlusTek PD305G6 is typically specified for quick-connect fuel line fittings, pneumatic valve bodies, cable ties, sensor housings, and mounting clips where PA66 GF30 parts fail by excessive water uptake or chloride stress cracking. PA12 has a lower density of amide groups than PA66, which limits the equilibrium water absorption of the polymer fraction. Saturated water uptake for 30% glass-filled PA12 at 23°C under ISO 62 is commonly 0.8–1.3%, whereas 30% glass-filled PA66 typically absorbs 5.5–6.5%. The glass fiber is non-hygroscopic and further reduces the total mass-percentage uptake. Lower water absorption means less thickness swelling, less tensile modulus loss in humid air, and more stable interference fits in operational service. In cyclic humidity, the part dimensions vary less than with PA66, but the fiber orientation still creates direction-dependent expansion and shrinkage.

Chloride stress-cracking resistance is another selection driver. PA12 performs better than PA66 in many zinc chloride and road-salt stress-cracking tests because its longer aliphatic segments reduce amide-plane interactions that enable cracking in short-chain polyamides. However, performance cannot be inferred from base-resin class alone. Molded test bars should be loaded under the expected service stress and immersed in the actual chloride solution or road-salt mixture; ISO 22088 and ISO 16770 provide standard frameworks for stress-cracking evaluation. In fuel-contact service, PA12 is used for clips and connectors because it resists diesel and gasoline swelling better than many short-chain polyamides. The introduction of aggressive oxygenated or bio-derived fuel blends can alter that behavior. Published data for PD305G6 in specific biofuel blends is limited; qualification should therefore include immersion in the actual service fluid at the upper operating temperature, followed by tensile property retention testing under ISO 527-1/-2 and dimensional measurement under ISO 62 or ISO 1817. Swelling of even a few percent can reduce modulus and loosen press fits, and the glass fiber reduces but does not eliminate solvent-induced dimensional shift.

Regulatory and safety status depends on the final colorant and additive package. The grade can be reviewed under REACH and RoHS 2 (2011/65/EU) obligations, but compliance declarations are substance-management tasks for the seller and end application; they are not intrinsic properties of the base compound. UL 94 classification for non-flame-retardant glass-reinforced polyamides is typically HB at the tested thickness. If a V-2 or V-0 rating is required, a flame-retardant grade or alternative polymer is necessary. Food-contact and drinking-water approvals are not automatically granted by the base resin and must be confirmed for the specific formulation, color, and article. The main design restrictions are the low elongation at break, the anisotropic shrinkage, the weld-line weakness, and the lower continuous-use temperature relative to glass-filled PA66 and PPA. These restrictions are acceptable only when the selection is driven by moisture stability, chloride resistance, and lower density.