Poly(butylene succinate) (PBS)
Poly(butylene succinate) (PBS) is a fully biodegradable and bio-based aliphatic polyester known for its excellent flexibility, impact strength, and processability. It is synthesized from renewable monomers—succinic acid and 1,4-butanediol—and offers mechanical performance comparable to conventional polyolefins like polypropylene (PP) and low-density polyethylene (LDPE).
PBS is a linear, semi-crystalline polymer with a repeating unit of [–O–(CH2)4–O–CO–(CH2)2–CO–]n. Its balanced crystallinity and low glass transition temperature make it ideal for flexible films and durable molded products.
Synthesis of PBS
PBS is synthesized via melt polycondensation of bio-based succinic acid and 1,4-butanediol. The process involves two stages: esterification followed by transesterification under vacuum.
- Esterification: Succinic acid reacts with excess 1,4-butanediol at 180–220 °C to form oligomeric esters and water.
- Polycondensation: Oligomers undergo chain extension at 230–250 °C under high vacuum (<0.3 mbar) using titanium or tin catalysts.
1. Monomer Production
Succinic Acid: Produced via bacterial fermentation of glucose:
C6H12O6 → HOOC–CH2–CH2–COOH + byproducts
(Glucose → Succinic Acid)
2. Esterification
HOOC–CH2–CH2–COOH + HO–(CH2)4–OH → Oligomer + 2 H2O
(Succinic Acid + 1,4-Butanediol → PBS Prepolymer)
3. Polycondensation
n [Prepolymer] → [–O–(CH2)4–O–CO–CH2–CH2–CO–]n
(Oligomers → High MW PBS, Mn = 40,000–100,000 g/mol)
Catalyst: Ti(OBu)4 or Sn(Oct)2 (100–300 ppm)
Poly(butylene succinate) – From Biomass to Biodegradable Plastic
PBS – From Biomass to Biodegradable Plastic: Sugarcane → Succinic Acid → PBS → Soil-Degradable Mulch Film
Properties of PBS
- Fully biodegradable and partially bio-based thermoplastic polyester
- Excellent flexibility and impact resistance
- Processable by injection molding, extrusion, blow molding, and film blowing
- High elongation and toughness, comparable to PP
- Moderate heat resistance and good chemical resistance
| Property | Value | Comparison |
|---|---|---|
| Density | 1.26 g/cm³ | Higher than PP (0.91 g/cm³) |
| Glass Transition Temperature (Tg) | −32 °C | Much lower than PLA (+60 °C) |
| Melting Temperature (Tm) | 114–116 °C | Lower than PP (165 °C) |
| Tensile Strength | 30–40 MPa | Similar to PP |
| Elongation at Break | 300–500% | Comparable to LDPE |
| Impact Strength (Izod) | 13.5 kJ/m² | Higher than PP (7 kJ/m²) |
| Biodegradability | EN 13432 certified | Degrades in soil, compost, and marine environments |
Applications of PBS
1. Packaging
- Flexible films and shrink wraps
- Compostable shopping bags
- Food trays and clamshells
2. Agriculture
- Mulch films (fully biodegradable in soil)
- Plant pots and seedling trays
- Agricultural twine and clips
3. Consumer Goods
- Disposable cutlery and plates
- 3D printing filaments (flexible grades)
- Hygiene products (diaper backsheets)
4. Biomedical & Industrial
- Drug delivery carriers
- Adhesives and coatings
- Foamed packaging (with PLA blends)
Environmental Impact & Sustainability
PBS delivers strong sustainability credentials, especially when produced from bio-based monomers:
- Bio-based content: Up to 100% (succinic acid + bio-BDO)
- Carbon footprint: ~1.5 kg CO₂/kg (bio-PBS) vs. 4.3 kg CO₂/kg (fossil PBS)
- Biodegradation: 90% in soil within 6 months; 70% in marine water in 12 months
- Certifications: OK Biodegradable SOIL, OK Biodegradable MARINE, EN 13432
Challenges
- Higher cost than PP/PE (\$3.8–4.2/kg vs. \$1.2/kg)
- Lower heat distortion temperature than PP
- Limited high-volume bio-BDO supply
- Slower crystallization rate than PET
Related Topics
Polyhydroxyalkanoates (PHA) - Synthesis, Properties & Applications
Poly(lactic acid) – PLA: Synthesis, Properties & Applications