PLA, PBS, PHB and starch-based plastics are not interchangeable “green plastics.” PLA is often screened for rigid parts with established supply; PBS for flexible or tough compounds where its grade data fit; PHB is one member of the PHA family with a narrow processing window; and thermoplastic-starch products are normally compounds whose behavior depends heavily on the other polymers, plasticizers and fillers. Choose an exact grade from product duty, molding behavior and a verified end-of-life route.
This four-family article is a shortlist for product developers. For a focused two-family decision, see PLA vs PHA: Application, Processing and End-of-Life Guide.
Compare the material identity before properties
| Label used in sourcing | What must be confirmed | Typical screening strength | Main qualification risk |
|---|---|---|---|
| PLA | Exact stereochemistry, crystallization behavior, impact/heat modifiers and color | Rigid products, appearance and an established processing/supply base | Heat, impact, hydrolysis and dimensional change can vary widely by grade and conditioning |
| PBS | Whether the product is neat PBS or a blend; supplier grade and additives | Flexible/tough compounds and blend modification where grade data support the duty | Do not confuse PBS with PBAT or infer properties from a family name |
| PHB / PHA | Which PHA chemistry, copolymer content, nucleation and processing aid package | A grade-specific combination of barrier, stiffness or biodegradation evidence | Thermal stability, crystallization, brittleness and supply must be proven for the exact grade |
| Starch-based compound | Starch percentage, carrier polymer, plasticizer, moisture sensitivity and claim basis | Cost or renewable-content objectives in applications suited to the compound | Water sensitivity, aging, odor, variability and end-of-life behavior depend on the complete formulation |
Set product requirements before asking which one is “best”
Define stiffness, impact, creep, heat, moisture, chemicals, optical appearance, barrier function, wall section and intended life. Add the manufacturing constraints: annual quantity, gate and flow length, drying equipment, residence-time control, allowable cycle range and whether the existing mold can tolerate a different shrinkage or venting demand.
A biodegradable or compostable claim is a separate requirement. Feedstock origin does not establish end-of-life behavior. The European Commission distinguishes bio-based, biodegradable and compostable plastics and warns that biodegradation depends on the receiving environment and conditions. Record the intended collection route and the exact test/certification evidence before making a claim.
Validate molding behavior with the supplier’s current data
- Drying: use the grade supplier’s moisture limit and drying procedure. A family-level instruction is not enough.
- Melt history: minimize unnecessary residence time and record actual melt condition; some biopolymer grades lose molecular weight or color when moisture and heat combine.
- Crystallization and cooling: mold temperature, nucleation, wall thickness and cooling can change dimensions and heat response.
- Venting and shear: check gas, odor, burn marks and fill balance in the intended cavity layout.
- Post-mold conditioning: compare dimensions and properties after the humidity, temperature and aging conditions that the product will see.
Use an evidence package, not a material nickname
Request the manufacturer, full grade, production site, technical data sheet, safety data sheet, regulatory declarations, composition/claim limitations, processing guide, change notification and relevant end-of-life test reports. A certificate for one compound cannot be transferred to another blend, color or thickness without a documented basis.
Buyer decision checklist
- What function and service life must the part deliver?
- Which exact grade and color are being quoted?
- What heat, moisture, chemical and mechanical conditions will be tested?
- What equipment and process controls does the grade require?
- Which disposal environment is claimed, and is that route available in the sales market?
- Does the evidence cover the finished product or only a resin test specimen?
Primary references
- European Commission: Bio-based, biodegradable and compostable plastics
- NatureWorks: Ingeo injection molding guide (supplier guidance for its PLA grades, not all PLA)
Prepare a quoteable material brief
Send the CAD, exact candidate grades, service conditions, critical dimensions, expected volume, required documentation and end-of-life claim through CKMOLD’s RFQ page. CKMOLD can review moldability and test planning; final material and environmental-claim approval remains product- and market-specific.