8.1 Introduction

In the past five years, a broad range of synthetic biodegradable resins based on aliphatic-aromatic co-polyesters have been commercialised by global suppliers. Synthetic biodegradable polyesters are made in modified PET polymerisation facilities from petrochemical feedstocks. Unlike other petrochemical-based polymers that take a very long time to degrade after disposal, these polyesters break down rapidly to CO ₂ and water in appropriate conditions where they are exposed to the combined attack of water and microbes. These products meet US, European, and Japanese composting standards, typically breaking down in twelve weeks under aerobic conditions.

The main types of synthetic biodegradable polymer in commercial use are as follows.

• Polybutylene adipate/terephthalate (PBAT) from BASF and IRe Chemical

• Polybutylene succinate (PBS) from Showa Highpolymers

• Polybutylene succinate/adipate) (PBSA) from Showa Highpolymers and IRe Chemicals

• Polybutylene succinate/carbonate (PBSC) from Mitsubishi Gas Chemical

• Polybutylene succinate terephthalate (PBST) from DuPont

• Polytetramethylene adipate/terephthalate (PTMT) from Novamont

• Polycaprolactone (PCL) from Daicel Chemical and Solvay

Aliphatic polyesters like polycaprolactone (PCL) or polybutylene adipate (PBA) are readily biodegradable, but because of their melting points of 60 C are unsuitable for many applications. On the other hand, aromatic polyesters like polyethylene terephthalate (PET) or polybutylene terephthalate (PBT) have high melting points above 200 C and very good material properties, but are not biodegradable.

The solution is a combination of aliphatic polyesters and aromatic polyesters. This involves modifying the crystalline structure of PBT by incorporating aliphatic monomer (adipic acid) in the polymer chain in such...