Abstract
AbstractThis work proposes an approach to fabricate flexible transparent ultraviolet (UV)-shielding membrane by casting method, which uniformly disperses pristine zinc oxide nanoparticles (NPs) in low-density polyethylene (LDPE). The critical conditions for film fabrication, such as casting temperature, LDPE concentration in the solution, dissolution time, NP concentration, and post hot press cooling processes, are systematically studied. It is found that the casting temperature needs to be close to the melting temperature of LDPE, namely, 115°C, so that transparent film formation without cracks can be guaranteed. NP agglomerates are suppressed if the polymer concentration is controlled below 6%. For good dispersion of NPs, LDPE has to be swelled or unentangled enough in the solution (close to 200 h dissolution time), and then the NP agglomerates can be diminished due to the diffusion of the NPs into the polymer gel (322 h dissolution time). When the NPs are well-dispersed in the LDPE film, the film can completely shield UV light while allowing high transmissivity for the visible light. As the concentration of NPs in the film increases from 4 to 6%, the transmissivity of the film decreases, the tensile strength increases, and the tensile failure strain decreases.
Highlights
Nanoparticles (NPs) are popularly utilized for the property promotion and functionalization of polymeric materials for advantageous electrical, optical, or mechanical properties [1,2,3] in more than past two decades
PE is a semicrystalline polymer with long molecular chains [30]
When the low-density polyethylene (LDPE) concentration increases, the enthalpy ΔHm of the polymer solution will be increased as shown in Table 2 (ΔHm increases almost five times for polymer concentration increasing from 2 to 10 wt%), which means a higher temperature and longer time will be required for the same degree of solubility of LDPE in the solution according to equation (1)
Summary
Nanoparticles (NPs) are popularly utilized for the property promotion and functionalization of polymeric materials for advantageous electrical, optical, or mechanical properties [1,2,3] in more than past two decades. Solution methods relatively achieve an even dispersion of NPs in polymers, especially those without a melting temperature or with a high molten viscosity as reported by Zarrinkhameh et al [27]. A systematic study was conducted to determine the optimal casting temperature, LDPE concentration, and dissolution time for uniform dispersion of inorganic NPs in LDPE using the solution-casting method. This ZnO NP/LDPE composite film exhibits spectrum selective properties for shielding UV and diminishing transmittance of visible light and could be potentially used as a passive cooling material for the purpose of energy conservation. The transmissivities of the films with different NP concentrations were evaluated
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