ArcBiox™ BGF40-B1 Impact Modified Long Glass Fiber Injection Polylactic Acid is a reinforced thermoplastic based on a polylactide matrix, formulated with a nominal 40% by weight discontinuous long glass fibre phase and an impact-modification package. The material is supplied as pultruded long-fibre pellets; in this product class, pellet length is commonly 10–12 mm, though the exact pellet length and impact-modifier chemistry for BGF40-B1 are not disclosed in the public documentation consulted. It is intended for injection moulding of semi-structural components that require higher modulus and heat deflection than unfilled PLA while maintaining some measure of toughness.

Published data for impact-modified PLA compounds filled with 40% long glass fibre place the tensile modulus between 10.5 GPa and 13.5 GPa when tested to ISO 527-2. Flexural modulus under ISO 178 is typically 9.5–12.5 GPa, and density under ISO 1183-1 falls between 1.45 g/cm³ and 1.60 g/cm³. Charpy notched impact strength under ISO 179-1/1eA is generally 15–25 kJ/m², while unnotched values may exceed 30 kJ/m² in the same class. These values are representative of the material class and should not be read as the supplier’s certified product limits. The B1 impact-modified variant is expected to trade a small portion of tensile modulus for increased notch resistance compared with an unmodified 40% long-glass PLA.

Material Constitution and the Role of Fibre Length Retention

Long glass fibre PLA differs from short glass fibre PLA primarily in the residual length of the reinforcement after injection. In the pellet, fibre length is fixed by pellet cut length, typically 10–12 mm. During screw recovery and injection, fibre attrition reduces the length distribution. Published mechanical data for this class show that retained number-average fibre lengths above 1.0 mm maintain a clear long-fibre response: higher notched impact strength, higher modulus retention at elevated temperature and reduced notch sensitivity. If the retained length drops below 0.5 mm, the property set begins to converge toward that of short-glass PLA. Therefore the moulding process is a first-order determinant of product performance, not a secondary handling consideration.

Product-specific published data for ArcBiox BGF40-B1 are limited in the open literature. Until a certificate of analysis is available, the above ranges should be treated as screening values only, and finite-element design allowables should not be built from them without validation on actual moulding trials.

How Does Moisture Uptake Reshape the Moulding Envelope?

Hydrolysis of the PLA ester backbone is the principal process risk. Residual moisture in the feed stream is not only a surface-defect variable; it reacts with the polymer chain during plastication, reducing number-average molecular weight, increasing melt flow rate and lowering notched impact strength. For PLA-based long-glass compounds of this class, pre-drying to below 0.025% (250 ppm) moisture is required before melt processing. This is normally accomplished in a desiccant dryer with supply air at 80 °C for 4–6 h and a dew point of −40 °C or lower. Moisture should be verified by Karl Fischer titration or ISO 15512; loss-on-drying at 105 °C is not a substitute for Karl Fischer in PLA compounds because the glass fibre mass fraction can distort weight-loss interpretation.

Once dried, the pellets should remain in sealed aluminium-lined packaging or be transferred directly to a closed hopper. At ambient relative humidity above 60%, open hold time should be minimized; the exact allowable hold time depends on pellet surface area and ambient temperature, and should be established by moisture-uptake trials rather than by analog to unfilled PLA. A hot-air hopper without desiccant cannot achieve the required moisture level in most production environments.

The melt processing window is narrow. For comparable 40% long-glass PLA, barrel settings between 190 °C and 210 °C are typical. Prolonged melt residence time above 5 min or melt temperatures above 220 °C can cause measurable chain scission, observed as an increase in melt volume-flow rate under ISO 1133-1 and a drop in Charpy notched impact under ISO 179-1/1eA. Mould temperature should be controlled in the range 25–60 °C. Temperatures below 25 °C may freeze the melt surface before the cavity fills, reducing weld-line strength and increasing gate stress. Temperatures above 60 °C can lengthen cycle time without a proportional gain in crystallinity unless the material contains an effective nucleating package.

Screw geometry matters. A low-compression, general-purpose screw with an L/D between 18:1 and 24:1 is preferable for long-glass materials. Back pressure should be held in the range 0.3–0.5 MPa, and screw surface speed should be limited to approximately 0.2–0.3 m/s. High shear and restrictive check valves can reduce retained fibre length before the melt reaches the gate. For this reason, process setup should include a short-shot series and fibre-length measurement, not merely a melt cushion check.

Mould shrinkage in this class is anisotropic. Published values for long-glass PLA composites show parallel-to-flow shrinkage of 0.1–0.3% and transverse-to-flow shrinkage of 0.4–0.8%. Gate design should therefore be placed to orient the major fibre direction along the primary load path. Edge gates and fan gates with a minimum thickness of 1.5–2.0 mm are preferred for wall thicknesses of 3 mm or more. Pin gates below 1.0 mm can cause severe fibre breakage and surface bloom. Hot runner drops should be open-pipe style with no dead spots, and gate diameter should not be reduced below 2.0 mm without mould-flow validation.

When Discontinuous Long Glass Fibre Slips Below the Critical Transfer Length

In short-glass PLA compounds, average fibre length after injection is often below 0.3 mm, which is below the critical load-transfer length for many PLA–glass interfaces. The result is lower notched impact strength and lower modulus retention at elevated temperature, but better thin-wall flow and smoother surfaces. BGF40-B1 is not a direct substitute for short-glass PLA when the part wall is below 1.0 mm or when surface aesthetics dominate. Its advantage appears in load-bearing ribs, bosses and attachment points where fibre length above 1.0 mm suppresses crack propagation through the fibre bundle.

Compared with unfilled impact-modified PLA, BGF40-B1 approximately triples tensile modulus. Unfilled impact-modified PLA typically exhibits tensile modulus below 3.0 GPa under ISO 527-2, while the 40% long-glass class exceeds 10 GPa. The trade-off is a loss in ultimate elongation and a shift in failure mode from ductile yielding to matrix microcracking with fibre pull-out. Snap-fit designs based on unfilled PLA strain tolerances should not be transferred without re-evaluating notch stresses; the glass reinforcement limits local strain capacity even when the impact modifier increases energy absorption.

Compared with long-glass polypropylene, BGF40-B1 offers higher stiffness in published class data and a bio-based carbon fraction, but it has a narrower processing window and greater sensitivity to hydrolytic degradation. PP-LGF40 tensile modulus is generally 8–11 GPa, below the PLA class range of 10.5–13.5 GPa. Polypropylene also has lower density and better resistance to hot-water and humid environments. BGF40-B1 should not be specified in direct hot-water contact or in underhood parts exposed to glycol-water mixtures at elevated temperature unless the supplier provides hydrolysis-resistance data or a stabilised variant.

Weld-line integrity is a further differentiator. In fibre-reinforced compounds, weld lines represent a region of fibre reorientation parallel to the weld plane. Published data for long-glass PLA and long-glass polypropylene show that tensile strength at a weld line can fall to 30–50% of the parent material value. The use of multiple gates should therefore be restricted to parts where the weld line is placed outside the primary load path. If multiple gates are unavoidable, melt front temperature should be kept near the upper end of the processing window, and a vent or overflow well should be positioned at the weld to reduce entrapped air and improve fibre interdigitation.

Regulatory compliance must be evaluated for the finished article. The PLA base and glass fibre sizing are subject to REACH registration in the EU. RoHS status is determined under Directive 2011/65/EU at the article level. Food-contact status must not be assumed from PLA alone; fully formulated BGF40-B1 would require migration testing under EU 10/2011 or a specific FDA 21 CFR clearance if direct food contact is intended. Biodegradability under industrial composting standards such as EN 13432 applies only to defined article thickness and disintegration conditions; the 40% glass fibre phase may leave a solid residue and therefore may not meet all compostability criteria. Strong alkalis, free amine additives and prolonged contact with hot water or steam are process and service incompatibilities that can accelerate hydrolysis and stress-cracking in PLA-based materials.

In a specific structural mounting bracket application, BGF40-B1 would be moulded with a barrel profile of 190–210 °C, mould temperature of 40 °C, injection fill time of 1.5–2.5 s, and hold pressure of 40–70 MPa. Cavity pressure sensors in the range 0–100 MPa monitor gate and end-of-fill pressures. Fibre-length distribution is measured by solvent burn-off or micro-CT at gate, mid-flow and end-of-fill sections; retained length below 0.5 mm at end of fill triggers a gate or screw-speed adjustment. Only after fibre retention exceeds the target is the batch released for ISO 527-2 tensile and ISO 179-1/1eA impact testing. This ensures that part qualification is tied to moulded microstructure rather than supplier pellet data alone.