Summary

Background

Even though the polymer industry consumes only approximately 5% of the oil extracted from the earth, the products of this industry are long-lived and present a tremendous and worsening problem for their disposal. Tragically some of these materials have a short lifetime as useful products but their subsequent effects on the quality of life of those that dispose of them are only too obvious. The methods of disposal of polymeric materials are principally through landfill, which is becoming increasing expensive as the landfill taxes begin to bite, recycling, which is appropriate in only a few cases for speciality systems, energy recovery, which may produce toxic gases if not controlled, and biodegradation. The role that biodegradation will play in the disposal of polymers will become increasingly important in the next 5-10 years. Problems at start of the project were that firstly, until recently, polymers that would fit the description of biodegradation were few and expensive, polyhydroxybutyrate (PHB) and polyhydroxybutyrate co-valerate (PHBV) were examples of polymers produced by enzymatic processes but more recently polylactic acid (PLA) has become a potential commodity polymer, and secondly many of the polymers, including PLA and PHB/PHBV had physical properties that did not lend themselves to the use of these materials as packaging materials.

Objectives

The objective of the project was to produce a series of modifiers that themselves had to be biodegradable but would enable these expensive polymers to be blended with other cheaper materials such as polycaprolactone (PCL). The specific applications that are envisaged for such materials are in the film manufacture for containment of horticultural products, netting manufacture for protection of young forestry plantations, netting manufacture for containment and protection of silage and in some cases of fruit and vegetables, and bottle manufacture for use in the pharmaceutical industry.

Activities

The research was directed towards the preparation, characterisation and use of modifiers that can be used as third components in the blending of PHB and PHBV with cheaper biodegradable polymers such as PCL. More specifically the research consisted of the following aspects:

• The synthesis of block copolymers of PHB/PHBV and PCL wherein the lengths of the individual blocks will be closely controlled.
• The production of a novel range of ester teased plasticisers in the expectation that these will act as modifiers of the physical properties of the blends of the polymers.
• The preparation of PHB/PHBV blends with LLDPE includes the use of existing photo-activators manufactured by the prime proposer and known to promote the oxidative degradation of polymers such LLDPE to low molecular weight bio-erodible products.
• The analysis and characterisation of the modifiers and then an investigation of their effects upon the physical and mechanical properties of the blends.

Such studies will be used in conjunction with the measurement of biotic, abiotic and hydrolytic degradation of the polymer blends to establish the potential for such systems to be compounded by one of the SMEs to produced polymer chips that are useable in film blowing and bottle manufacturing systems.

Results

The problem of blending incompatible polymers was approached by synthesising block copolymers to act as compatibilising agents. The block lengths of these copolymers can also be controlled very closely. The development means that now these copolymers can be used as modifiers in the blending of the two base copolymers with the expectation that the blends will be compatible. The flexibility of PLA has been improved by these developed polymer modifiers. Initially directed towards the modification of PHB the technology was instead applied to the plastification of PLA.

Conclusions

The project has led to the production of master-batch polymers that can be extruded as sheet film or blown film with simple mixtures of the master-batch and virgin polymer. This work has excited the interest of a major polymer fabricator in the UK.

Follow-up activities

A new consortium has been formed to take advantage of the developed technology through a UK-DTI-Link programme.

Contacts

Coordinator

• A.J. AMASS / Aston University Chemical Engineering / UNITED KINGDOM

Participant

• Urs J HANGGI / BIOMER GERMANY
• Catherine ANSALDI / Exaplast SA FRANCE
• Jean-Pierre NAUDE FILONNIERE / Greensol FRANCE
• Simon Joseph HOLLAND / SmithKline Beecham Pharmaceuticals Ltd Pharmaceutical Technologies Department / UNITED KINGDOM