Improving the Transparency of Ultra-Drawn Melt-Crystallized Polyethylenes: Toward High-Modulus/High-Strength Window Application

Abstract

Highly transparent, ultradrawn high-density polyethylene (HDPE) films were successfully prepared using compression molding and solid-state drawing techniques. The low optical transmittance (<50%) of the pure drawn HDPE films can be drastically improved (>90%) by incorporating a small amount (>1 wt %/wt) of specific additives to HDPE materials prior to drawing. It is shown that additives with relatively high refractive index result in an increased optical transmittance in the visible light wavelength which illustrates that the improvement in optical characteristics probably originates from refractive index matching between the crystalline and noncrystalline regions in the drawn films. Moreover, the optically transparent drawn HDPE films containing additives maintain their physical and mechanical properties, especially their high modulus and high strength, which make these films potentially useful in a variety of applications, such as high-impact windows.

Transparent, Lightweight, and High Strength Polyethylene Films by a Scalable Continuous Extrusion and Solid‐State Drawing Process

“…At this mixing temperature, the weight loss of BZT particles is less than 1.0% of the total amount of BZT which means that BZT has a high stability at this temperature. The BZT concentration used was based on a previous study by Shen et al who showed that drawn HDPE films containing 2 wt% BZT could already transmit 90% of visible light. After compounding, the extruded melt was cooled in a water bath and cut into pellets using a Dr. Collin CSG171 (Germany) strand pelletizer.…”

“…Recently, Shen et al added a 2‐(2H‐benzotriazol‐2‐yl)‐4,6‐ditertpentylphenol (BZT) additive to HDPE films which were drawn to high draw ratios (≈20), resulting in highly oriented polymer films with transmittance values of 90% and a tensile strength of 650 MPa . BZT additives are typically used in small amounts (<1%) as UV absorbers for polymers and coatings.…”

“…In the above‐described studies either with or without additives lab‐scale and batch‐wise fabrication procedures were employed to produce the oriented transparent HDPE films. These procedures involved micro‐compounding in the case of additives, compression molding of films followed by solid‐state drawing using a universal tensile tester equipped with a thermostatically controlled environmental chamber.…”

Effective Control of Laser‐Induced Carbonization Using Low‐Density Polyethylene/Polystyrene Multilayered Structure via Nanolayer Coextrusion

“…For the LDPE matrix, n = 1.51; and for the PS matrix, n = 1.59. According to calculations using , R LDPE = 4.12% and R PS = 5.19% . When the number of layer interfaces was small, the light reflection at the layer interfaces had little effect on the light penetration.…”

“…According to calculations using (1), R LDPE = 4.12% and R PS = 5.19%. [35] When the number of layer interfaces was small, the light reflection at the layer interfaces had little effect on the light penetration. However, as the number of layer interfaces increased, that is, the number of layers increased, the reflection of light at the layer interfaces had a significant negative effect on the penetration of light.…”