Lignin as a UV Light Blocker—A Review

Abstract

Lignin is the by-product of pulp and paper industries and bio-refining operations. It is available as the leading natural phenolic biopolymer in the market. It has chromophore functional groups and can absorb a broad spectrum of UV light in range of 250–400 nm. Using lignin as a natural ingredient in sunscreen cream, transparent film, paints, varnishes and microorganism protection has been actively investigated. Both in non-modified and modified forms, lignin provides enhancing UV protection of commercial products with less than a 10% blend with other material. In mixtures with other synthetic UV blockers, lignin indicated synergic effects and increased final UV blocking potential in compare with using only synthetic UV blocker or lignin. However, using lignin as a UV blocker is also challenging due to its complex structure, polydispersity in molecular weight, brownish color and some impurities that require more research in order to make it an ideal bio-based UV blocker.

UV Protective, Antioxidant, Antibacterial and Compostable Polylactic Acid Composites Containing Pristine and Chemically Modified Lignin Nanoparticles

“…In this context, light barrier or interference properties of polymeric materials that are going to be used as food packaging options become of utmost importance [ 70 ]. In the case of PLA, it presents high transmittance in both the visible (400–700 nm) and the UV region (250–400 nm) of the spectrum, the previous triggering the study of different strategies for improving its blocking ability [ 71 , 72 , 73 , 74 ]. The UV–visible transmittance spectra of neat PLA and the PLA based nanocomposites prepared are shown in Figure 5 .…”

“…All the nanocomposite films showed reduced transmittance compared to neat PLA films, especially in the UV light region ( Figure 5 ). Both nanometric and micrometric lignin particles have been previously recognized for the blocking effect in the UV light region induced when used as fillers of PLA [ 9 , 16 , 43 , 74 ]. UV light is subdivided into three distinct wavelength regions: UV-A (400–315 nm), which accounts for the longest wavelength and lowest energy, UV-B (315–280 nm) being the most energetic component of natural UV light and which may cause photochemical degradation of plastics, and UV-C (280–100 nm), which is generally created from artificial light sources [ 75 ].…”

“…Lignin acetylation has previously proved to produce color and UV absorbance reduction due to the restriction of the electron-donating character of its phenolic hydroxyls [ 79 ]. In fact, modification of lignin through acetylation is one of the strategies proposed to minimize the lignin color issue, which is a challenge for its application in food packaging materials where their aesthetic quality influences the consumer acceptability of food products [ 74 ]. In this context, a noticeable reduction of the dark brown color of the nanocomposites produced was herein achieved through LNP modification at the expense of an acceptable UV absorption blocking reduction capacity of the films.…”

Nano-Structured Lignin as Green Antioxidant and UV Shielding Ingredient for Sunscreen Applications

“…Both UV-A and UV-B are causing agents for DNA damage and cancer [133]. Lignin shows a broad absorption range in the UV region due to the presence of different chromophores and auxochromic groups (Figure 3), the maximum of absorbance being located at 283 nm [134,135]. Auxochromic groups (from ancient Greek In addition to the capacity of sequestering radical species, lignin is promising to in hibit lipid peroxidation and, from a general point of view, the oxidative degradation o other cosmetic ingredients.…”

Recent Catalytic Approaches for the Production of Cycloalkane Intermediates from Lignin‐Based Aromatic Compounds: A Review

“… [7–9] As such, lignin is used as a solid fuel for combustion. More recently, researchers are developing composite polymeric materials from lignin; which can be used as a UV‐blocking agent [10–12] …”