Thermoanalytical Characterization of Oxo-Biodegradable Polymers - METTLER TOLEDO

Thermoanalytical Characterization of Oxo-Biodegradable Polymers

One of the major problems of the plastics we use today is their great stability – they impact the environment for years without undergoing decomposition. Recently, a number of research projects have been started to develop plastics that degrade within a short time in the environment.

 

Introduction

Up until now, two different approaches have been followed for making biologically degradable polymers.

The first approach is to produce plastics from biomaterials such as maize (corn) or wheat, which rapidly decompose to smaller, biologically degradable compounds after use.

The other approach is to modify commonly used polymers such as polyethylene so that they degrade more quickly and can then be digested by microorganisms. This article deals with this second category of polymers, also referred to as oxo-biodegradable polymers.

The degradation of such polymers is accelerated by the addition of small amounts of metal salts that act as catalysts and promote oxidization of the polymer chains. Since oxidation can only take place when oxygen is present, this type of decomposition only works when the plastic is exposed to an open-air environment. If the plastic is disposed of in a landfill under anaerobic conditions, decomposition is no faster than with ordinary plastics.

The metal salts added are only present in catalytic amounts and do not have a negative effect on the environment. They are salts of iron, magnesium, manganese, zinc or nickel, which are in any case present in nature, for example in metalloproteins.

 

Experimental Details

The polymers were investigated by performing DSC and TGA/DSC measurements. The polymeric composition of an oxo-biodegradable packaging film was determined from its melting curve. Pure PE-LD in the form of pellets was measured for comparison...



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Conclusions

The oxidation behavior of the oxo-biodegradable film is significantly different compared with that of a normal PE film. The behavior confirms that the films degrade more rapidly in an air atmosphere. Anaerobic decomposition under nitrogen is not accelerated by the added salts; their presence might even be a disadvantage for decomposition.

The TGA curves show that the oxo-biodegradable films more contain inorganic additives and that the amounts can be easily determined.



Thermoanalytical Characterization of Oxo-Biodegradable Polymers | Thermal Analysis Application No. UC375 | Application published in METTLER TOLEDO Thermal Analysis UserCom 37