Durability of Biodegradable Polymers for the Conservation of Cultural Heritage

Abstract

The use of polymers for conservation of cultural heritage is related to the possibility to slow down or stop natural deterioration which, in many cases, corresponds to stopping the entrance of liquid water and to favor spontaneous water vapor removal. Unfortunately, hydrophobicity is generally favored by surface roughness and thus competitive with transparency. It is therefore important to find an optimal balance hydrophobicity, transparency and durability (especially to photooxidation). However, polymers typically used for applications in this field come from non-renewable resources and are not biodegradable. In this work, the mechanical, structural, and optical properties of PLA, PBAT, and a PBAT/PLA blends, as well as surface properties and water vapor permeability, were investigated before and after exposure to UV irradiation, in order to evaluate their durability and suitability for conservation of cultural heritage.

Recycling of a Biodegradable Polymer Blend

“…The increase of the viscosity must be, then, correlated with an increase of the molecular weight or with a formation of some cross-links or some branching during the reprocessing. PBAT is, indeed, prone to form crosslinks during degradation [ 19 , 20 , 21 , 33 ], and the branching is the first step in forming cross-linked structures. No cross-links were revealed for the PLA.…”

“…The mechanical properties, namely elastic modulus (E), tensile strength (TS) and elongation at break (EB), of unprocessed Ecovio are reported in Table 2 [ 20 ].…”

“…Of course, the degradation undergone during processing and the environmental degradation during the lifetime are the main hindrances to the recycling of these polymers. It is, indeed, well known that these biodegradable polymers are quite labile with respect to both thermomechanical degradation [ 15 , 16 , 17 , 18 ] and photo-oxidation [ 19 , 20 , 21 , 22 , 23 , 24 ].…”

The Effect of Calcium Carbonate on the Photo‐Oxidative Behavior of Poly(butylene adipate‐co‐terephthalate)

“…It has been shown that nanocomposites prepared with clays, when exposed to UV irradiation, degrade much faster than polymers as such [ 21–26 ] and this behavior has been attributed mainly to the pro‐oxidant effect of the impurities of the transition metals present in the clays. On the other hand, PBAT shows a poor photo‐oxidation behavior [ 27,28 ] and a complex photo‐oxidation mechanism. Indeed, the photo‐oxidation induces both decrease of the molecular weight and formation of branching.…”

Effect of ultraviolet and moisture action on biodegradable polymers and their blend

“…The use of polymers for outdoor applications is strongly dependent on their durability, which is their capability to withstand the degradation phenomena. One of the main degradation phenomena is obviously represented by photooxidation, however it is not usually enough to provide polymer systems with good resistance to photooxidation, but it is also important to link this with the functional needs related to the specific application; furthermore, in some cases (such as, for instance, in cultural heritage conservation) features such as hydrophobicity and transparency should be granted 1 .…”