EcoVid 43TFH High Heat General Purpose Wood Filled Polylactic Acid is a pelletized compounded thermoplastic based on semicrystalline polylactic acid, a cellulosic wood flour fraction near 43 wt%, and a high-temperature nucleation/chain-extension package. The grade is supplied as cylindrical pellets with a nominal diameter of 3.0 mm, length of 3.2 mm, and settled bulk density of 0.72 g/cm³ measured under ISO 60. Renewable carbon content is reported above 92 % by ASTM D6866-21. The material is intended for injection moulding, compression moulding, sheet extrusion, and profile extrusion where the melt temperature is held at or below 210 °C. Unlike a dry blend of wood and PLA, 43TFH is pre-compounded on a co-rotating twin-screw line with a melt filtration step, then pelletised. The designation 43TFH identifies the high-heat general-purpose configuration; standard wood-filled PLA grades in the same product family typically lack the nucleating system and exhibit lower heat deflection at 1.8 MPa.

At 23 °C and 50 % RH, the compound is specified with a density of 1.28 g/cm³ by ISO 1183-1, a melt flow rate of 7.5 g/10 min at 210 °C and 2.16 kg by ISO 1133-1:2022, and an ash content of 43 % after ignition at 600 °C by ISO 3451-1. The filler fraction raises flexural modulus to 5.6 GPa under ISO 178:2019, compared with 3.4 GPa for unfilled PLA of similar molecular weight. The trade-off is a reduction in notched Charpy impact strength to 3.8 kJ/m² under ISO 179-1:2023. Mould shrinkage is anisotropic: typical flow-direction shrinkage is 0.4 % and transverse-direction shrinkage is 0.7 % after injection into a 60 °C mould.

Compared with standard wood-filled PLA, the high-heat package in 43TFH moves the heat deflection temperature under 1.8 MPa from the 55–65 °C range to 88–96 °C when the mould is held at 90–110 °C and cooling is sufficiently slow to develop crystallinity. This difference is not obtained at cold mould temperatures; a mould at 30–50 °C leaves the PLA largely amorphous and HDT remains near 58–64 °C. Thus the grade is specified as high-heat only when thermal processing conditions are matched to the crystallisation window.

What Published Thermal and Rheological Boundaries Govern 43TFH Processing?

Supplier rheology data for 43TFH cover the shear-rate interval from 100 s⁻¹ to 1,000 s⁻¹ at 190 °C and 210 °C using capillary rheometry under ISO 11443:2021. The melt exhibits a power-law index near 0.65 over this range, indicating pronounced shear thinning. Melt flow rate at 210 °C with 2.16 kg load is 7.5 g/10 min under ISO 1133-1:2022. These values permit filling of wall sections down to 1.8 mm on a 900 kN clamp injection moulding machine when the injection speed is set above 120 mm/s. For thick sections above 6 mm, flow length is limited by the high filler surface area; published spiral-flow data for this specific configuration is limited.

Thermal processing boundaries are narrower than those of PP-based wood compounds because PLA is thermally and hydrolytically sensitive. Barrel zone settings from feed to nozzle are normally 165 °C, 175 °C, 190 °C, and 195 °C, with nozzle temperature not exceeding 210 °C. Residence time at melt temperature above 200 °C should not exceed 8 min. Hold-up beyond this boundary causes a drop in melt viscosity through chain scission, visible yellowing of the wood phase, and vent odour. General-purpose injection screws with 20:1 L/D, compression ratio 2.2:1, and a ring non-return valve are specified. Extended screw clearances with worn check rings reduce melt quality and increase moisture sensitivity.

Because PLA-based compounds undergo hydrolytic chain scission at melt temperatures, pellet moisture must be below 0.025 % before melt processing. As-received moisture after storage at 50 % RH is typically 0.3–0.6 %. A desiccant dryer with dew point below -40 °C, air temperature 80 °C, and residence time of 4 h is required to reach the specified limit. Verification is by Karl Fischer titration under ISO 15512:2019 or a calibrated moisture analyser with a temperature of 160 °C. In production areas above 60 % RH, moisture regain from open containers occurs within 60 min; therefore closed hoppers with dry-air purge at 0.5 m³/h are recommended. Wet pellets produce splay at the gate, reduced melt strength, and a 15–25 % loss in tensile strength when moisture exceeds 0.1 % at point of melt.

Regrind levels above 20 wt% increase moisture uptake and variability in particle size. Drying time for 20 % regrind should be extended to 6 h because reclaimed wood fibres hold moisture in surface pores. Drying temperatures above 90 °C are not recommended because pellets can soften and bridge in the hopper.

When Mould Temperature Is Held Within the PLA Cold Crystallisation Window

Heat deflection in 43TFH is process-dependent. If the mould surface temperature is kept at 30–50 °C, the PLA phase solidifies with limited crystallinity and the HDT at 1.8 MPa remains 58–64 °C under ISO 75-2:2013. When the tool is heated to 90–110 °C and cooling time is extended to 20–35 s, the nucleating package develops crystallinity above 30 % as measured by differential scanning calorimetry at 10 K/min under ISO 11357-3. The resulting HDT reaches 88–96 °C. This window is narrow: above 110 °C, wood particle smearing and ejection sticking appear; below 85 °C, the high-heat response is not fully expressed.

Annealing after ejection at 105 °C for 30 min raises HDT by 4–8 °C but can introduce additional shrinkage of 0.3 % and warpage in long-flow geometries. Tool temperature control should be verified with surface probes; infrared pyrometers can under-report the mould surface temperature by 8–12 °C on textured wood-filled surfaces. For tool heating, pressurised water at 110 °C or oil circulating at 120 °C is used. Silicone rubber heater mats are not sufficient for thin-wall production because heat transfer is uneven and can create localised crystallinity.

Production-scale compounding of 43TFH is performed on a 40:1 L/D co-rotating twin-screw extruder with 45 mm diameter screws, screw speed 350 rpm, and throughput 85 kg/h. Zone temperatures are set from 165 °C at the feed barrel to 195 °C in the mixing zone, with die temperature 185 °C and a vacuum vent at -0.08 MPa. The wood fraction is introduced by side feeding after the PLA melt is formed, which reduces fibre breakage and prevents premature degradation at high specific energy input. A gear pump after the extruder maintains strand die pressure fluctuation at ±2 bar. Pellet quality is controlled by moisture below 0.2 % and a pellet-to-pellet melt flow variation below ±0.5 g/10 min.

For injection moulding of the compounded pellets, a melt filter with 60/100 mesh screens is recommended to prevent nozzle clogging from agglomerated wood fines. In direct extrusion of sheet or profile, a screen changer with 80 mesh media is used before the die. When regrind is introduced above 20 wt%, melt pressure variability rises and tensile strength falls by 4–6 %; therefore regrind content should be limited to 20 % for load-bearing mouldings.

Comparative Property Profile Against Unfilled PLA and Standard Wood-Filled PLA

The table lists representative quality-control values at 23 °C and 50 % RH under the cited standards. The standard wood-filled PLA comparison does not contain the high-temperature nucleating package; filler loading is similar but heat deflection at 1.8 MPa is lower.

Under tensile creep at 60 °C and 10 MPa load, ISO 899-1:2023 gives a creep modulus after 1,000 h of approximately 1.8 GPa for 43TFH, whereas standard wood-filled PLA falls below 1.2 GPa. Compared with a general-purpose ABS, 43TFH exhibits higher flexural modulus and renewable carbon content but lower impact strength and greater sensitivity to moisture. Drying, tool shrinkage, and purge procedures therefore differ from those used for ABS runs.

In thin-wall electrical enclosure applications, 43TFH has been injection moulded on a 1,200 kN clamp machine with a hot runner manifold at 195 °C, gate diameter 1.2 mm, and cooling time 25 s. The wood-filled compound yields a matt surface with visible fibre orientation. Post-mould painting requires flame or plasma treatment because the surface wetting tension under ISO 8296 is typically below 38 mN/m. For high-gloss coating, an adhesion promoter based on chlorinated polyolefin is required. The surface is not electroplatable without an electroless copper strike and pore sealing.

Injection parameters include melt temperature 195 °C, mould temperature 100 °C, injection speed 140 mm/s, hold pressure 60 MPa, and back pressure 4 bar. Screw back pressure above 8 bar causes excessive shear heating and darkens the wood phase. Screw recovery time should be kept below 10 s on a general-purpose screw to avoid unnecessary residence at high temperature.

For profile extrusion, a 45 mm single-screw extruder with 24:1 L/D, barrier screw, and die temperature 185 °C is recommended. Calibration tooling at 40–60 °C maintains profile tolerance within ±0.15 mm. Melt breaking strength is lower than unfilled PLA; supports and short draw-down lengths are required during start-up. Continuous service for load-bearing parts is recommended below 80 °C because creep and hydrolytic degradation accelerate above that temperature. Exposure to steam or immersion in water above 60 °C is not recommended for long-term use.

Difference from polyolefin wood composites is most evident in hardness and scratch resistance. 43TFH has a Shore D hardness near 82 under ISO 48-4, higher than many PP-based wood composites, but the material is more brittle at sub-zero temperatures. The heat deflection temperature is higher than a standard wood PLA grade, but lower than a glass-filled high-heat PLA grade. Product selection should therefore be driven by part geometry, loading condition, and post-mould coating requirements.

The compliance matrix identifies the principal regulatory and quality-control documents for the raw compound. End-use suitability for food-contact, medical, or toy applications must be confirmed with the compound supplier against the relevant positive lists.