| HS Code | 182241 |
| Product Name | PURASORB PD 24 Medical Device Poly(D-lactide) |
| Chemical Name | Poly(D-lactide) |
| Cas Number | 26023-30-3 |
| Material Type | Resorbable semicrystalline polyester |
| Grade | Medical Device |
| Appearance | White to off-white granules |
| Inherent Viscosity | 2.4 dL/g |
| Glass Transition Temperature | 55-60 °C |
| Melting Temperature | 170-180 °C |
| Density | 1.24-1.30 g/cm³ |
| Solubility | Soluble in chloroform, dichloromethane, and dioxane; insoluble in water and ethanol |
| Residual Monomer | <0.5% |
| Water Content | <0.5% |
| Heavy Metals | <10 ppm |
| Degradation Mechanism | Hydrolytic degradation to D-lactic acid |
| Resorption Time | Greater than 24 months |
| Storage | Cool, dry place protected from moisture and heat |
As an accredited PURASORB PD 24 Medical Device Poly(D-lactide) factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | PURASORB PD 24 is packaged in 1 kg sealed, moisture-barrier foil pouches with desiccant, inside labeled outer fiberboard containers. |
| Container Loading (20′ FCL) | Medical-device grade PURASORB PD 24 is palletized in sealed, labeled packaging and loaded into a clean, dry 20′ FCL, secured for transport. |
| Shipping | PURASORB PD 24 Medical Device Poly(D-lactide) is shipped as a solid polymer in sealed, moisture-barrier foil bags or drums. It is transported under ambient conditions, protected from moisture, heat, and contamination. It is not classified as dangerous goods. Shipping documents include SDS, CoA, and lot traceability. |
| Storage | Store PURASORB PD 24 in a cool, dry, well-ventilated area away from direct sunlight, heat, and ignition sources. Keep the container tightly closed and protect from moisture; the polymer is hydrolytically sensitive. Recommended storage is typically 2–8°C in original unopened packaging. Allow to reach room temperature before opening to prevent condensation. |
| Shelf Life | Shelf life is 24 months from date of manufacture when stored sealed in original packaging under recommended dry, cool conditions. |
Medical-grade PURASORB PD 24 is a poly(D-lactide) homopolymer supplied for implantable applications; the supplier certificate of analysis identifies the midpoint inherent viscosity as 2.4 dL/g measured in chloroform at 25 °C and 0.1 g/dL. In trauma fixation, the polymer is not processed as a neat resin but as a stereocomplex-forming constituent with poly(L-lactide). When an equimolar PLLA/PDLA blend is compounded, the two enantiomeric chains pack into a 3₁ helical stereocomplex with a melting endotherm between 220 °C and 230 °C, approximately 50 °C above the PLLA homopolymer melting range. Pre-drying at 80 °C under vacuum below -0.09 MPa for 8 h reduces moisture to below 200 ppm before compounding. The blend is processed in a co-rotating twin-screw extruder with 44:1 L/D ratio, zone temperatures 210–225 °C, die temperature 230 °C, screw speed 250 rpm, and vacuum degassing at -0.08 MPa. Residence time is kept below 2 min; barrel zones above 240 °C trigger lactide reformation and molecular weight loss. The strand is cooled in a water bath at 20 °C, dried, and pelletised. Injection moulding of stereocomplex fixation plates uses a clamp force of 1,500 kN, injection pressure 80–100 MPa, holding pressure 60–80 MPa, back pressure 5–10 MPa, barrel temperatures 200–230 °C, and a mould temperature of 30–50 °C. A hot runner should be avoided unless thermal isolation from the manifold is confirmed; dead spots above 240 °C produce yellowing and shear-induced molecular weight loss. Moulded specimens conditioned at 23 °C and 50 % RH for 48 h are tested per ASTM D638-14 Type IV; reported values for stereocomplex PLA fall approximately at 50–65 MPa tensile strength and 3.5–4.5 GPa flexural modulus, with elongation at break of 2–5 %. Final devices include craniofacial fixation plates, interference screws, and suture anchors.
| Standard | Test or clause | Application-specific boundary |
|---|---|---|
| ISO 13781:2017 | In vitro degradation of polylactide implant resins | Phosphate-buffered saline at 37 °C, pH 7.4, 26-week mass loss and molar mass retention |
| ASTM F2902-16 | Assessment of absorbable polymeric implants | Documented molecular weight, crystallinity, and degradation profile before clinical use |
| ASTM F1635-16 | In vitro hydrolytic degradation test | Specimens conditioned to constant mass before 37 °C immersion |
| ISO 10993-1:2018 | Biological evaluation of medical devices | Cytotoxicity, irritation, sensitisation, and implantation endpoints for bone-contact devices |
| ISO 13485:2016 | Quality management for medical device manufacturing | Batch traceability from polymer lot to finished sterile device |
In long-acting injectable depot formulations, PURASORB PD 24 is used as a slowly degrading poly(D-lactide) matrix or as a release-rate modifier blended with medical PLGA. A representative solvent extraction process begins by dissolving the polymer in dichloromethane at 15 % w/w; the active pharmaceutical ingredient is either dissolved or dispersed at a drug-to-polymer ratio between 1:5 and 1:10 for small molecules and 10–25 % w/w for peptides. Because the inherent viscosity of 2.4 dL/g produces high organic-phase viscosity at room temperature, the polymer solution may require dilution to 10–12 % w/w or pre-warming to 30 °C before emulsification. The organic phase is emulsified into a continuous phase of 1.0 % w/v polyvinyl alcohol (88 % hydrolysed) at 25 °C using a rotor-stator mixer at 10,000 rpm for 2 min. The resulting oil-in-water emulsion is transferred to a 2 % aqueous isopropanol quenching bath and hardened for 4 h under paddle stirring. Microspheres are collected by sieving, washed with water for injection, and lyophilised at -40 °C shelf temperature for 24 h. Residual dichloromethane is determined by headspace gas chromatography; the acceptance criterion is ≤600 ppm according to USP <467> Option 1, with any chloroform retained from the process held to ≤60 ppm. Particle size is measured by laser diffraction with a Dv90 target of 90–120 µm for subcutaneous or intramuscular injection; syringeability is evaluated per USP <788> particulate matter. Terminal gamma sterilisation at 25 kGy is used only after stability studies confirm that the resulting molecular weight reduction does not accelerate release beyond the design of the depot. The homopolymer degrades by bulk hydrolysis, and the crystalline domains of PDLA slow water ingress relative to amorphous PLGA, extending the lag phase before mass loss. The final microsphere presentation is intended for 12-week to 6-month release of peptides or small molecules from biodegradable depots.
Filament-grade blends prepared from PLLA and PURASORB PD 24 at a 90:10 weight ratio are extruded through a single-screw extruder with a 15 mm screw diameter and 20:1 L/D ratio, fitted with a gear melt pump and a 1.75 mm circular die. The polymer is pre-dried at 70 °C for 12 h to a moisture content below 250 ppm; barrel temperatures are set from 180 °C to 205 °C, the melt pump pressure is held at 4–6 MPa, and the filament is drawn through a 40 °C water bath with an air gap of 10 mm. A laser diameter gauge provides closed-loop control of the haul-off speed to maintain roundness within ±0.05 mm and diameter within 1.75 ±0.05 mm. During fused filament fabrication, the dried filament is fed to a direct-drive print head with a 0.4 mm nozzle, 0.15 mm layer height, nozzle setpoint 205 °C, bed temperature 60 °C, print speed 40 mm/s, extrusion multiplier 0.98, and part-cooling fan at 30 %. The presence of PDLA nucleates stereocomplex crystallites during the deposition cooldown, reducing warpage in large parts and improving interlayer adhesion at the corresponding bed temperature. Printed tensile bars are tested per ASTM D638-14 Type IV after conditioning at 23 °C and 50 % RH for 48 h; users should verify the exact strength values because infill density and raster angle dominate mechanical performance. Cytotoxicity of printed scaffolds is assessed according to ISO 10993-5:2009, and dimensional accuracy is documented with reference to ISO/ASTM 52900. The terminal product is a patient-specific resorbable bone scaffold or maxillofacial reconstruction model, with the final pore architecture determined by the raster pattern and infill density rather than by the polymer feed alone.
Electrospun tubular scaffolds fabricated from a 95:5 PLLA/PDLA solution are produced for vascular graft and nerve guide research. The two polymers are dissolved at 8–12 % w/v in a solvent system of chloroform and dimethylformamide at an 80:20 volume ratio and stirred for 12 h at 25 °C to obtain a homogeneous solution. The solution is loaded into a syringe pump and delivered at 1.0 mL/h through a 22 G blunt needle charged to 18–22 kV; the tip-to-collector distance is 15 cm. Fibres are collected on a rotating mandrel at 500 rpm under controlled relative humidity of 30–40 %. The resulting fibre diameter ranges from 400 nm to 800 nm, measured by scanning electron microscopy at 5 kV accelerating voltage after gold sputtering. The PDLA fraction creates stereocomplex nuclei that remain after solvent evaporation and reduce fibre shrinkage during post-processing annealing at 100 °C for 1 h. Compliance testing for tubular scaffolds intended as vascular prostheses follows ISO 7198:2016 for porosity, burst strength, and suture retention; if the device is intended for chronic implantation, the full biological evaluation plan is structured under ISO 10993-1:2018. The terminal configuration is a nanofibrous tube with an internal diameter defined by the mandrel, typically 4–6 mm for small-caliber vascular graft feasibility studies.
Addition of 5–10 wt% PURASORB PD 24 to a PLLA melt stream raises the attainable drawing temperature during monofilament suture production and reduces diameter fluctuation through stereocomplex nucleation, but published data for this specific configuration is limited and line qualification under ISO 13485:2016 is required before use in absorbable suture manufacturing.
Ultrasonic spray coating of PDLA-containing formulations onto L605 cobalt-chromium stent platforms uses a 60 kHz atomising nozzle, a solution flow rate of 0.5 mL/min, and a drying air temperature of 50 °C. The coating formulation consists of a PLLA-based drug matrix containing 10–20 wt% PURASORB PD 24 dissolved in chloroform or a chloroform/tetrahydrofuran blend at 1–2 % w/v solids. The PDLA fraction increases the resistance of the dry film to cracking during balloon expansion and crimping by forming stereocomplex domains that act as physical crosslinks; without this modification, pure amorphous PLLA coatings can develop radial cracks at crimping diameters below 1.2 mm. Coated stents are crimped onto 3.0–4.0 mm balloon catheters and visually inspected at 30× magnification for delamination or bridging. Drug release is evaluated in phosphate-buffered saline at 37 °C and pH 7.4 with a target release period of 90 days; the coating thickness is measured by optical coherence tomography on a rotating fixture with a target dry thickness of 5–15 µm. Compliance for vascular stents is structured under ISO 25539-2:2020, and the biological evaluation follows ISO 10993-1:2018 with additional haemocompatibility testing per ISO 10993-4:2017. The terminal product is a balloon-expandable coronary stent with a bioresorbable PDLA-modified PLLA coating that protects the underlying metallic strut during deployment and then degrades by bulk hydrolysis.
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PURASORB PD 24 is a medical-grade poly(D-lactide) homopolymer supplied as white to pale-yellow granules. The grade designation carries the midpoint of the inherent viscosity specification, 0.24 dL/g, determined by solution viscometry in chloroform at a concentration of 0.1 g/dL and a bath temperature of 25 °C. The material is synthesized from D-lactide monomer, and its repeat-unit stereochemistry is the defining chemical attribute that separates it from poly(L-lactide) and from poly(D,L-lactide) copolymers. As a semicrystalline aliphatic polyester, PURASORB PD 24 undergoes hydrolytic chain scission in aqueous media, with degradation products that include D-lactic acid, oligomers, and ultimately carbon dioxide and water after biological clearance. The grade is produced under an ISO 13485:2016 quality management system, but final medical device compliance requires evaluation of the processed article under ISO 10993-1:2018 and the relevant endpoint parts of the ISO 10993 series. Lot-specific certificates of analysis report residual monomer, residual tin, and solvent extractables; fixed values cannot be assumed across production campaigns.
The relatively low inherent viscosity of 0.24 dL/g places this grade in the low-melt-viscosity segment of the polylactide family. In melt processing, the material can be processed at lower barrel temperatures than high-IV poly(L-lactide) grades with inherent viscosity above 1.0 dL/g. However, thermal stability in the melt is limited by the same ester backbone that governs degradation; residence time at temperatures above the melting transition should be minimized. Pre-drying under vacuum or dry-air conditions at 80 °C to 100 °C to a moisture content below 250 ppm is recommended before melt processing. When residual moisture exceeds 250 ppm, the melt undergoes hydrolytic degradation during compounding, producing a measurable drop in die pressure and broadening of the molecular weight distribution. On a small-scale twin-screw micro-compounder with screw diameter of 11 mm and 40:1 L/D, compounding can be started at a flat temperature profile near the lower end of the polylactide melt-processing range; exact barrel temperatures must be adjusted to the specific equipment because published data for this particular grade is limited. The low melt viscosity also reduces melt strength, so film blowing and large-part injection molding with deep draw are less suitable than thin-wall injection molding, solvent casting, electrospinning, or microparticle fabrication. For solvent-based processes, the polymer dissolves in chlorinated and selected non-chlorinated solvents; dichloromethane, chloroform, acetone, and ethyl acetate are commonly referenced for polylactide processing. Selection of solvent affects the viscosity of the polymer solution, the drying profile, and the residual solvent burden. Residual solvent levels in the final device must comply with ICH Q3C limits for the chosen solvent class. Processors requiring a high-solids coating solution can exploit the lower solution viscosity of this grade, but film toughness may be lower than films made from higher-IV poly(L-lactide) because of reduced chain entanglement. In electrospinning, the same reduction in chain entanglement shifts the operable concentration window. The exact solvent ratio, feed rate, collector distance, and applied voltage require design of experiments against fiber diameter targets measured by scanning electron microscopy.
Hydrolytic degradation of poly(D-lactide) proceeds by random chain scission in the amorphous phase first, followed by the crystalline regions. The semicrystalline morphology of PURASORB PD 24 results in a degradation profile that differs from amorphous poly(D,L-lactide) grades, which lose mass more uniformly and do not show autocatalytic retention effects from spherulitic crystallites. Because the 0.24 dL/g inherent viscosity is lower than that of typical suture or orthopedic homopolymers, the period before the onset of measurable mass loss is shortened under otherwise identical conditions. In vitro degradation testing per ASTM F1635-16 or ISO 13781 should report media, buffer capacity, specimen geometry, temperature, pH, and mass or inherent viscosity change. The use of unbuffered media can accelerate chain scission and produce a transient pH drop, whereas strongly buffered media may mask local acid accumulation; the comparison of degradation studies across laboratories requires this variable to be controlled. This grade is therefore positioned for short-to-intermediate degradation applications such as microparticle-based drug delivery, coatings, and temporary tissue fixation where rapid mass loss and low melt viscosity are more useful than high load-bearing strength. Published data for this specific low-IV D-lactide grade in large load-bearing orthopedic devices is limited; conversion of this polymer into load-bearing components without supporting mechanical and degradation data would be technically unsound.
Compared with poly(L-lactide), PURASORB PD 24 can form stereocomplex crystals when blended with poly(L-lactide). The equimolar blend of D-lactide and L-lactide homopolymers is reported to produce a stereocomplex melting transition roughly 50 °C above the homopolymer melting point; this increase is used where thermal resistance must be raised without changing the aliphatic polyester chemistry. The low inherent viscosity of PD 24 means the stereocomplex formed with high-IV PLLA will have a chain-length mismatch; the magnitude of the stereocomplex melting endotherm must be confirmed by differential scanning calorimetry at 10 °C/min under nitrogen.
The selection of poly(D-lactide) rather than poly(L-lactide) is driven by chirality, not by commercial availability. The human body metabolizes L-lactate more readily than D-lactate; the D-lactate released during degradation is cleared by different pathways and at lower rates. While small quantities are metabolized, devices with large polymer mass or highly concentrated microparticle depots require assessment of systemic D-lactate load and local acidosis. The material is not approved as a standalone implant by virtue of its grade designation; biocompatibility is a property of the finished device, sterilization method, packaging, and leachables profile. For devices that combine PD 24 with PLLA in a stereocomplex, phase separation and solvent selection become critical. The stereocomplex is generally less soluble than the parent homopolymers, which can alter electrospinning or casting conditions. The stereocomplex also has different hydrolytic stability and thermal stability, so data generated on the homopolymer alone cannot be transferred to the blend. Polarimetry or chiral gas chromatography can be used to confirm enantiomeric purity of the resin before specification transfer to a contract manufacturer.
Sterilization of aliphatic polyesters must account for glass transition, melting temperature, and hydrolytic sensitivity. Ethylene oxide and gamma irradiation are the two most commonly evaluated methods. Gamma irradiation can cause chain scission and reduce molecular weight; the effect is dose-dependent and is influenced by irradiation atmosphere, temperature, and antioxidant content. For a low-IV grade, the additional viscosity loss from irradiation may be proportionally more significant than for a high-IV resin. Ethylene oxide can plasticize the amorphous phase and leave residues; ethylene oxide and ethylene chlorohydrin levels must meet ISO 10993-7:2008 limits. Steam sterilization is generally incompatible because the process temperature may exceed the glass transition and cause deformation, while the moisture load accelerates hydrolysis. Dry heat sterilization is similarly constrained by the thermal stability window. Packaging for a degradable polyester should control headspace moisture; an aluminium foil laminate or equivalent barrier pouch with a desiccant is used to maintain moisture below 250 ppm after opening. Storage below 25 °C and protection from direct UV light are typical; exposure to ambient humidity above 60% RH during transfer operations increases the risk of pre-processing hydrolysis. The glass transition of polylactide homopolymers is reported near 55 °C to 60 °C; storage above this range risks cold crystallization or particle caking in amorphous regions.
Comparisons to other polylactide-based materials should be made on the basis of chiral composition, inherent viscosity, crystallinity, and degradation profile. The table below summarizes the principal distinctions. These entries are drawn from standard polylactide polymer science and are not a substitute for lot-specific mechanical testing.
| Attribute | PURASORB PD 24 | Poly(L-lactide) homopolymer | Poly(D,L-lactide) copolymer | PLGA 50:50 |
|---|---|---|---|---|
| Repeat-unit chirality | D | L | D,L racemic/mixed | L-lactide/glycolide |
| Solid-state morphology | Semicrystalline | Semicrystalline | Amorphous | Amorphous |
| Inherent viscosity midpoint | 0.24 dL/g | Often 0.6–4.0 dL/g | Variable | Variable |
| Water uptake rate | Moderate | Moderate | Higher | High |
| Degradation product acid | D-lactic acid | L-lactic acid | D,L-lactic acid | L-lactic acid and glycolic acid |
| Melt strength | Low | Higher | Low | Low |
| Stereocomplex formation with opposite PLA | Yes with PLLA | Yes with PDLA | No | No |
| Typical processing route | Solvent casting, electrospinning, microparticles, thin-wall melt processing | Sutures, screws, plates, thicker melt parts | Drug delivery, coatings | Drug delivery, microspheres |
Lot-specific certificate of analysis values govern final processing conditions. Processors evaluating PURASORB PD 24 against other polylactide grades should compare inherent viscosity under identical solvent and temperature conditions; otherwise viscosity values are not transferable. The final device manufacturer retains responsibility for validation of residual solvents, degradation products, and mechanical performance under relevant standards.
