deTerra XP698 High Impact White Injection Molding Polylactic Acid is a pelletized polylactic acid compound formulated for injection molding of opaque white components requiring impact resistance above that of unmodified PLA. The model designation XP698 distinguishes the high-impact white grade from natural and transparent PLA grades by the presence of an impact-modifier phase and titanium dioxide pigmentation. Melt volume-flow rate measured under ISO 1133-1:2022 at 210 °C and 2.16 kg is typically 10–20 cm³/10 min. Density measured under ISO 1183-1:2019 is typically 1.23–1.26 g/cm³. Tensile yield stress measured on type 1A specimens under ISO 527-2:2012 is in the range of 45–55 MPa; nominal tensile strain at break is 10–25%. Flexural modulus measured under ISO 178:2019 is typically 2100–2600 MPa. Notched Izod impact strength measured under ISO 180/A:2023 at 23 °C is in the range of 10–18 kJ/m². Heat deflection temperature under ISO 75-2/B:2013 at 0.45 MPa is typically 50–55 °C. These values are class-typical for white high-impact injection-molding PLA; because published data for the exact XP698 formulation are limited to manufacturer technical parameters, release values must be confirmed against the production lot certificate of analysis.

The product is supplied in moisture-barrier packaging. Opened containers should be re-sealed and the machine hopper should be purged with dry air, because PLA pellets absorb atmospheric moisture faster than many polyolefins. The grade is intended for conventional three-zone screw injection molding machines; it is not suitable for extrusion blow molding or continuous profile extrusion unless the screw and downstream equipment are designed specifically for PLA viscosity characteristics.

Storage conditions below 30 °C and 60% relative humidity in original sealed packaging preserve the specified moisture content. Cold storage is not required, but condensation must be avoided when moving pallets from cool to warm environments. If condensation forms on foil bags, the sealed bags should be allowed to equilibrate before opening. Partially used packaging should be resealed with desiccant pillows or kept under dry-air purge. Moisture uptake in open containers can exceed 0.1% within 8 h at 25 °C and 60% relative humidity; this is class-typical for PLA pellet stock and requires confirmation at the production site.

Why Does White Pigmentation Reduce Weld-Line Ductility in Injection-Molded Parts?

White pigmentation changes both melt rheology and solid-state failure behavior of high-impact PLA. Titanium dioxide particles at typical loadings of 2–4 wt% increase melt viscosity by approximately 10–20% compared with an unpigmented high-impact PLA of the same base resin. In multi-gated molds, the pigment particles concentrate at the melt-front boundary and act as stress risers. Weld-line notched Izod impact strength can fall to 55–70% of the bulk value, and the reduction is larger when the melt-front temperature at convergence is below 190 °C. The practical melt-temperature band for balancing weld-line healing against thermal degradation is therefore narrow: 200–210 °C, with deviations exceeding ±5 °C causing either insufficient knit-line strength or measurable viscosity loss.

Tools should be designed to move weld lines away from tensile-loaded ribs and bosses. Sequential valve gating, direct edge gates, or flow-channel modifications are preferred over multiple pin gates. Venting depth should be 0.015–0.025 mm, and cavity air must be evacuated ahead of the converging fronts. Weld-line performance should be validated on color-matched plaques with ISO 527-2 and ISO 180/A before mold commissioning. Published data for this specific grade are limited; processors should generate weld-line performance curves for the intended wall thickness and gate configuration.

Because the grade is pre-colored white, additional color concentrates may shift mechanical properties. Dry blend or masterbatch addition above 2 wt% should be validated for melt flow, impact strength, and surface appearance. Transparent or translucent parts cannot be produced from this grade. Wall thickness beyond 3.5 mm may require longer cooling times and can develop internal voids because of the low thermal conductivity of PLA. Thin walls below 1.2 mm may require higher injection speed and melt temperature up to 215 °C, but residence time must then be reduced accordingly.

Following desiccant drying to a residual moisture content below 0.025% (250 ppm) is mandatory before melt processing. The dryer must be a desiccant unit with a supply air dew point no higher than −40 °C, a bed temperature of 45–60 °C, and a residence time of 4–6 h for sealed containers. Under ambient relative humidity above 60%, drying time should be extended to 6–8 h and the hopper should be blanketed with dry air or nitrogen. Hot-air ovens are not an acceptable substitute because they cannot maintain the required dew point. PLA processing at moisture contents above 0.05% produces hydrolytic chain scission, reduced melt viscosity, silver streaking, splay, and loss of impact performance. Polyvinyl chloride and acetal purging compounds should not be used; their decomposition residues can accelerate hydrolytic degradation of PLA. Amine-containing lubricants, antistatic additives, and certain color masterbatches should also be excluded from the feedstock stream because they may promote transesterification and molecular weight loss.

When the Melt Cushion Is Lost During Screw Recovery

Loss of melt cushion during screw recovery in XP698 indicates non-return valve leakage, insufficient back pressure, or excessive barrel temperature. A cushion of 3–5 mm should be maintained, and screw recovery should be adjusted so that barrel residence time does not exceed 5 minutes at 200 °C or 3 minutes at 215 °C. Check-ring clearance exceeding 0.05 mm may produce shot-weight variation above ±0.8%. On a 25 mm diameter general-purpose screw with 20:1 L/D and compression ratio of 2.0:1–2.5:1, back pressure of 0.5–1.0 MPa and screw speed of 40–100 rpm are typical. Barrel temperature settings from feed to nozzle are approximately 165–180 °C, 185–200 °C, 195–215 °C, and 200–215 °C. Mold temperature should be held at 20–35 °C for rapid cycle times; mold temperatures up to 90 °C can increase crystallinity and heat deflection temperature but extend cycle time and may increase dimensional variation.

Injection velocity should be set to fill the cavity in 0.5–1.5 s for wall thicknesses of 1.5–3.0 mm. Pack and hold pressure is typically 60–90% of peak injection pressure, with hold time maintained until gate freeze. For a 1.0 mm diameter gate and 2.0 mm wall, gate freeze time is approximately 2–3 s; hold time should extend 1–2 s beyond gate freeze. These process settings are class-typical and must be adjusted for multi-cavity tooling and hot-runner configurations.

Hot runner systems must use internally heated or thermally uniform manifolds because PLA is shear-sensitive and heat-sensitive. Valve gating is preferred over open hot tips for white parts because residence time in hot tips can yellow the pigment and generate black specks. Hot runner drops should be sized for shear rates below 50 000 s⁻¹. Cold runner diameters should not be less than 3.0 mm for full-round runners. Clamp force requirements depend on projected area and flow length; at a melt temperature of 205 °C, cavity pressure typically peaks at 40–60 MPa for thin-wall parts. A clamp force of 3–5 kN/cm² of projected area is a practical starting point for unfilled grades, with higher values for long-flow or multi-cavity tools.

Thermal Degradation Pathways in High-Impact PLA Melt Processing

Thermal degradation in PLA proceeds by random chain scission, hydrolysis, and depolymerization to lactide. Below 200 °C, residual moisture is the dominant degradation source; above 230 °C, lactide re-formation and molecular weight loss accelerate. The melt residence time at 200 °C should not exceed 5 minutes, and at 215 °C should not exceed 3 minutes. A drop in melt pressure during screw recovery without a change in barrel setpoint is an early indicator of molecular weight reduction. Maintaining dry feedstock is more effective than lowering melt temperature alone because hydrolytic degradation is kinetically significant at processing-relevant temperatures. Acetaldehyde, propionaldehyde, and lactide volatiles may be generated during prolonged residence; adequate venting and extraction are required to limit operator exposure and part defects.

For component designers replacing general-purpose PLA or ABS in opaque white housings, the selection logic differs by load type, temperature, and dimensional stability. The high-impact PLA grade provides notched Izod impact strength roughly three to five times higher than unmodified PLA, while flexural modulus is reduced by approximately 20–30%. Compared with ABS, the PLA grade has a higher density of approximately 1.24 g/cm³ versus 1.04–1.07 g/cm³, and a lower heat deflection temperature at 0.45 MPa of approximately 50–55 °C versus 90–100 °C. Mold shrinkage under ISO 294-4:2018 is typically 0.3–0.6%. Table 1 summarizes class-typical ranges; the values are not batch guarantees.

Melt flow rate comparisons between PLA and ABS are not valid under identical conditions because PLA is tested at 210 °C with 2.16 kg, whereas ABS is commonly tested at 220 °C with 10 kg. The impact-modified white PLA grade also differs from general-purpose PLA in chemical resistance: it retains susceptibility to alkaline solutions and high-humidity hydrolysis. Regrind from XP698 should not be mixed with PET, polyolefin, or polycarbonate reclaim streams because PLA contamination disrupts those recycling processes.

High-Impact PLA Grades Are Not Drop-In Replacements for ABS in Hot Zones

Parts molded from XP698 should not be specified for continuous use above 55 °C under mechanical load unless annealing is performed. Annealing at 80–100 °C for 1–2 h can raise heat deflection temperature by increasing crystallinity, but it also produces additional shrinkage of 0.3–0.8% and may distort thin walls. Applications involving hot water, dishwasher cycles, or engine-compartment air above 60 °C require a different material. Chemical incompatibility with strong aqueous bases and high-humidity steam should be considered; PLA undergoes hydrolytic degradation above its glass transition temperature in humid conditions. For room-temperature consumer housings, point-of-sale displays, and indoor enclosures, the material can replace ABS where the lower heat deflection temperature is acceptable, but finished-part validation remains mandatory.

Compliance documentation for white high-impact PLA should be obtained from the supplier for each production lot and should include REACH SVHC screening under Regulation (EC) No 1907/2006 and RoHS restricted substance data under Directive 2011/65/EU. Titanium dioxide pigmentation does not automatically confer food-contact approval; components intended for food-contact applications must be tested for overall migration under EU 10/2011 using the food simulant appropriate to the end use, with an overall migration limit of 10 mg/dm². For medical or pharmaceutical applications, cytotoxicity testing under ISO 10993-5:2009 is not implied by this material classification and must be conducted on the finished device. If the molding facility blends color concentrate, regrind, or processing aids, the compliance declaration must cover the final blended composition, not only the neat XP698 pellet. Regrind levels above 30% may reduce impact strength and should be validated with ISO 180/A on production parts.