Abstract
Despite several excellent properties including low shrinkage, good chemical resistance, curable at low temperatures and the absence of byproducts or volatiles, epoxy resins are susceptible to ultra violet (UV) damage and their durability is reduced substantially when exposed to outdoor environments. To overcome this drawback, UV absorbers have been usually used to decrease the rate of UV degradation. In this present study, the effects of UV light on the chemical, mechanical and physical properties of cured epoxy structure, as well as the effect of an organic UV absorber, Tinuvin 1130, on the epoxy properties were investigated. Chemical changes in a cured epoxy system as a result of the presence and absence of Tinuvin 1130 were determined using Fourier transform infrared spectroscopy (FT-IR) analyses. The effect of Tinuvin 1130 on the surface morphology of the epoxy systems was also investigated by scanning electron microscopy (SEM) imaging. Additionally, the glass transition temperatures (Tg) before and during UV radiation were measured. After an 800 h UV radiation, mechanical test results revealed that the lack of the UV absorber can lead to a ~30% reduction in tensile strength. However, in the presence of Tinuvin 1130, the tensile strength was reduced only by ~11%. It was hypothesized that the use of Tinuvin 1130, as an organic UV absorber in the epoxy-amine system, could decrease the undesirable effects, arising from exposure to UV light.
Highlights
Nowadays, various polymeric materials are commercially available and used in many applications such as protective coatings, civil engineering materials, aerospace composites, automotive fields, and marine industries [1,2,3,4]
The ultra violet (UV) radiations are harmful to polymers, a phenomenon known as photodegradation is initiated which affects the physical, mechanical and chemical properties of polymers [7,8,9,10,11]
The amine hydrogen molar mass (AHMM) of Epikure F205, which was employed as a curing agent, was reported to be 105 g/eq each amine hydrogen reacts with one epoxy group and the was reported to be 105 g/eq each amine hydrogen reacts with one epoxy group and the stoichiometric ratio of the curing agent to epoxy resin for curing reaction can be determined stoichiometric ratio of the curing agent to epoxy resin for curing reaction can be determined according according to AHMM/epoxy molar mass (EMM) = 0.56
Summary
Various polymeric materials are commercially available and used in many applications such as protective coatings, civil engineering materials, aerospace composites, automotive fields, and marine industries [1,2,3,4]. The durability of materials is a key factor for many applications which affects the performance of polymer-based materials. Ozone layer filters emit UV wavelengths from 100 to 315 nm. UV light of sunlight forms free radicals on the surface of polymer-based materials [12]. These radicals are extremely active in attacking the polymeric structures. The energy of UV light is usually higher than the chemical bonds strength e.g., C–C, O–O, H–O, and C–N in polymers. These chemical bonds are prone to break and photodegradation occurs [13]. Other environmental factors including humidity, oxygen, temperature, and pollutants can intensify the rate of photodegradation significantly [14,15,16]
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