For ski sports, ski goggles are one of their essential equipment. Ski goggles can not only protect the eyes, but also provide additional functions such as UV protection, anti-glare, and anti-fog. The realization of these functions is inseparable from the help of modern polymer materials.

ski goggle structure

Ski goggles mainly include frames, lenses and foam sponges, and different parts have different manufacturing methods. Compared with traditional metal materials (such as stainless steel) or non-metallic materials (such as glass), polymer materials have the characteristics of lighter weight and still have good strength. Therefore, polymer materials in modern ski goggles are becoming more and more popular. More and more appear.

Polymer materials in ski goggles

1. Polymer material in frame and foam sponge

The frame of ski goggles is generally made of high-hardness thermoplastic polyurethanes (TPU), which is synthesized through the polymerization reaction of diisocyanate and diol, as shown in Figure c below. Since the amino group and carbonyl group in front of the molecular chain can form hydrogen bonds, the interaction force between polyurethane molecules is very strong, and it is not easy to change the molecular arrangement state by external force. The reaction to the macroscopic is that the material has high strength and rarely irreversible. Therefore, polyurethane is used as the frame of ski goggles, which can provide better protection for skiers.

Polyurethane materials with different properties can also be synthesized by selecting isocyanates and diols with different molecular structures. In today's life, as hard as artificial leather, as soft as mobile phone casings, different polyurethanes can be used to make them. By the way, why is the word "thermoplastic" added to the name of this polyurethane? Because the molecules of this polyurethane are linear, they can move freely after being heated to a sufficient temperature. Macroscopically, they can be melted into a liquid, so that they can be shaped while they are hot. In order to be compatible with another type of network structure, The difference between heating and non-melting polyurethane adds the word "thermoplastic" to the name.

Another type of reticulated polyurethane is used in foam sponges. Its synthesis is to replace part of the diols in the previous scheme with triols or even tetraols, so that all small molecules will be connected into a large network-like structure in the end. In order to ensure comfort, some foaming agents are also added in the process of making sponges, just like adding some yeast when making dough. Provides better cushioning when necessary. In addition, the porous structure is also conducive to the circulation of air inside and outside, and has a certain effect on preventing fogging.

2. Polymer materials in lenses

In order to chemically provide adequate protection for athletes, the lenses of ski goggles also need to be made of high-strength materials. Fragile glass is definitely not suitable, and opaque polyurethane cannot be used. Finally, another polymer material called polycarbonate (PC) is widely used. Its molecular structure is shown in Figure d below. Polycarbonate is very transparent and has the highest strength among transparent materials, so it is used as the main material of lenses. Not only the lenses of ski goggles, but also the canopy of modern fighter jets can use polycarbonate, which is enough to prove the high strength of this material.

Lenses generally require further processing in addition to polycarbonate to achieve better performance. For example, in order to prevent annoying fogging during the game from affecting vision, the inside of the lens will be coated with a cellulose acetate coating. We should all be familiar with cellulose. It is the main component of plant fiber in nature, and we consume it every day. There are also a lot of hydroxyl groups on the side chain of cellulose that can form hydrogen bonds, resulting in super-strong intermolecular interactions, which basically cannot be dissolved or melted. The cellulose acetate is obtained by reacting a part of the hydroxyl groups in the cellulose with acetic acid. Since the hydroxyl groups are less, it can be dissolved and processed at last. At the same time, the remaining hydroxyl groups can interact with water to a certain extent, so that the water on the surface can Spread out without gathering into small water droplets drop by drop, which has the effect of anti-fog.