Effect of Aging on the Mechanical Properties of Highly Transparent Fluoropolymers for the Conservation of Archaeological Sites

Abstract

In recent years, fluoropolymers have found numerous applications in the architectural field because of their combination of mechanical-chemical resistance and high transparency. In the present work, commercial fluorinated polymers, such as perfluoro alkoxy (PFA) and ethylene tetrafluoroethylene copolymer (ETFE), have been evaluated for use as protective and transparent layers on monumental and archaeological sites (to preserve mosaics or frescoes) during the phases of restoration or maintenance outdoors. Considering this specific application, the present study was developed by evaluating the evolution of the mechanical (tensile, tear propagation resistance, and low-velocity impact tests) and chemical (FTIR and DSC analysis) properties of the films after accelerated UV aging. The results that were obtained demonstrated the high resistance capacity of the ETFE, which exhibits considerably higher elastic modulus and critical tear energy values than PFA films (1075.38 MPa and 131.70 N/mm for ETFE; 625.48 MPa and 59.06 N/mm for PFA). After aging, the samples exhibited only a slight reduction of about 5% in the elastic modulus for both polymers and 10% in the critical tear energy values for PFA. Furthermore, the differences in impact resistance after aging were limited for both polymers; however, the ETFE film showed higher peak force than the PFA films (82.95 N and 42.22 N, respectively). The results obtained demonstrated the high resistance capacity of ETFE films, making them the most suitable candidate for the considered application.

Recycling Tetrafluoroethylene–Perfluoroalkyl Vinylether Copolymer (PFA) Using Extrusion Process

“…reorganization of the crystal structure during elastic deformation followed by its fragmentation. [ 34 ] Recycled PFA shows a change in deformation length in which reorganization occurs (not shown here). Also, a reduction of molecular weight occurs during reprocessing because of the required high temperatures of conversion processes which affect chain packaging.…”

“…Despite the cause remaining unclear, several hypotheses can be listed for this change in modulus. The increase in the degree of crystallinity, as discussed in the DSC results, is well documented to increase hardness, decrease elongation at break and improve Young's Modulus for polyolefins [ 33 ] and fluoropolymers, [ 34,35 ] Fluoropolymers have been reported to display the phenomenon of double‐yielding, i.e. reorganization of the crystal structure during elastic deformation followed by its fragmentation.…”

Fluorine-containing nano-objects with the same compositions but different segment distributions: synthesis, characterization and comparison

“…Among all the synthesized polymers, fluoropolymers possess unique properties, such as excellent heat resistance, 1,2 low surface energy [3][4][5] and super oxidation resistance. 2,6 Correspondingly, fluoropolymers are indispensable in modern industry and play an important role in the automotive industry, 7 aerospace, 8,9 construction, 10 high-end equipment manufacturing, electronic information, and new energy strategies. [11][12][13] However, due to the high incompatibility of fluoropolymers with other polymers, the practical application of fluoropolymers is limited.…”

Electrical aging of fluoropolymer cable insulation materials induced by partial discharge

“…Their chemical structure is predominantly made up of carbon-fluorine backbones (C F), which are known for their high bond dissociation energy and low polarity [11], ensuring high chemical stability, which is integral to their electrical insulating capabilities [11], [12]. Their applications extend to various fields due to their outstanding mechanical and chemical resistance, along with their high transparency [5]. Like other polymers, fluoropolymers also age under various environmental and operational conditions.…”