I have worn glasses for over ten years. The first time I wore glasses was in junior high school. When I was a child, I loved watching TV and didn't pay attention to my posture when reading. My vision gradually deteriorated. At that time, there were not many classmates and friends around me who wore glasses, so I started wearing glasses. I was embarrassed to wear glasses at first. Sometimes I can't see the chalk words on the blackboard clearly, so I secretly take them out and wear them. I gradually got used to them and now I wear them all day long. This is also because of the power of glasses. The initial price increased from 300 to 600, and I didn’t dare to go out without wearing it. I've bought a lot of glasses over the years. I didn’t know much about glasses before. Every time I go, I listen to the salesperson talk nonsense and then pay. The quality of eyeglasses tends to degrade over a short period of time. In order not to be taken advantage of anymore, I also started to learn some knowledge about glasses, hoping to be less taken advantage of.
Let’s talk about the framework first. The frames are in direct contact with human skin for a long time, which greatly affects the wearer's image. Therefore, the choice of framework cannot be arbitrary. But the price of frames varies greatly, ranging from tens of dollars. Some cost thousands of dollars. When you go to an optical store, you will be deceived by many theories, you will still be confused and confused, and in the end you will still have to pay the price. We can choose the frames that suit us from these aspects.
Glasses frame material:
Optical stores like to make a fuss about the material of the frames. They promote a frame made of a certain material as being high-tech and having a lot of benefits, but often what you're paying a lot of money for is something else. There are mainly the following materials on the market now:
-
Pure titanium
Titanium is so popular in the eyewear industry that pure titanium frames have become a treasure in ordinary optical stores. Just say you want to buy a better frame and the salesperson will recommend this to you. Titanium has the characteristics of light weight, high specific strength (ratio of strength and density), corrosion resistance, and non-toxicity: its density is 4.5g/cm3, which is slightly heavier than aluminum (2.8g/cm3), while titanium is heavier than iron (7~ 8g/cm3), with strong corrosion resistance. Even aqua regia cannot corrode at room temperature. Titanium can remain on the ocean floor for decades without oxidizing. These properties make titanium widely used in the aerospace industry and medical fields.
In order to avoid being fooled by dealers, we first need to know what kind of titanium is called pure titanium? There are many opinions about pure titanium on the Internet. I specifically found the national standard to explain. The following is the national standard GB/T 3620.1-2007 for titanium and titanium alloy grades and chemical compositions. From this we can see that there are 9 types of pure titanium, among which TA1ELI, the highest purity, has a titanium content of 99.5%, and TA4, the lowest purity, has a titanium content of 98.455%. According to the standard, other elements refer to trace elements inherent in the production process of titanium and titanium alloys, rather than artificially added elements. Therefore, according to national standards, pure titanium can be defined as titanium with a titanium content of 98.455% and above and without artificially added elements.
Titanium is abundant in nature, but due to the difficulty of purification and processing, the price of pure titanium is very high. The price of industrial primary materials alone is about three times more expensive than stainless steel. But pure titanium is also the best among common materials. Pure titanium frames from major brands will be marked Titan-P, Ti-P or PURE TITANIUM (some may also be other) on the temples or lenses. These logos also appear on many cheap and small brands. You know why. Because the strength of pure titanium is not very high, the temples of pure titanium will be thicker and cannot be made as thin as iron wire.
-
Titanium alloy
The performance of pure titanium alloy is not perfect. Pure titanium is rarely used in industry, and titanium alloys are more often used, because impurities in titanium can have a great impact on the performance of titanium. Adding specific substances makes it perform better than pure titanium, so titanium alloys are used in a wider range of applications than pure titanium. Adding different substances will produce titanium alloys with different properties.
Some frames will say beta titanium. Many people are confused about what beta titanium is. In fact, titanium is an allotrope and comes in two forms: alpha titanium and beta titanium. Similar to carbon, it comes in two forms: diamond and graphite. Alpha titanium has a close-packed hexagonal lattice structure, and beta titanium has a body-centered cubic lattice structure.
Titanium and titanium alloys can be divided into alpha titanium, beta titanium and alpha + beta titanium (a combination of alpha titanium and beta titanium) according to their structure. The one on the left is a β body-centered cubic structure, which has high strength and good toughness. The one on the right is an α titanium close-packed hexagonal cubic structure, which is more brittle and has poor plasticity, so β titanium is generally used in glasses. The grade of α titanium is TA, the grade of β titanium is TB, and the grade of α+β titanium is TC. From the above national standards, we can see that pure titanium is α titanium and β titanium is titanium alloy, so generally pure titanium frames refer to α titanium, and β titanium frames refer to β titanium alloy rather than β pure titanium, but Alpha titanium is not necessarily pure titanium.
Generally, the titanium content of titanium alloy is only 5% less than that of pure titanium, but the cost is much lower and the mechanical properties are better, making it a compromise choice. Titanium with different trace elements added has different properties, so titanium alloys have many names depending on the added elements.
-
acetate glasses
In the eyes of ordinary people, they are just "plastic"; however, there is definitely an essential difference between plate and plastic products in the true sense. Generally speaking, acetate glasses are spectacle frames made from a prefabricated plastic plate through one-piece molding (most of them are currently pressed and polished).
Most plastic sheets are made of fiber acetate, and a few high-end frames are made of propionate fiber. As far as the origin of plastic sheets is concerned, French and Italian sheets are better, and many mid-to-high-end sheet glasses are made from these high-quality sheets; For example, the Ray-Ban frames that we are familiar with are representative products of this type of material.
-
Memory alloy
Memory alloy frames are the most recommended frames by optical shops because their features are very obvious and easy to display, so optical shop owners often like to use memory alloy frames to fool you. There are many components of memory alloys, such as nickel-titanium alloy, gold-cadmium alloy, copper-zinc alloy, etc. The better quality is nickel-titanium alloy, which is more expensive and has the characteristics of high strength and corrosion resistance. Titanium alloy. However, nickel is a metal that can cause allergies. If you choose a small brand, the coating quality is not up to standard, and it is easy for the coating to peel off and cause allergies. Other memory alloys are relatively cheap, so it's important to prevent shops from passing them off as NiTi. The temples of this kind of memory alloy are generally made as thin as iron wire, so they are lighter in weight.
-
TR-90
TR-90 is also known as plastic titanium. It is not actually a titanium alloy, but a polymer nylon material invented by the Swiss EMS-GRIVORY (Ames Chemicals) company. Its density is only 1.14-1.15 g/cm3. Only 1/4 of pure titanium and 1/8 of stainless steel. Can float in highly concentrated salt water. It is wear-resistant, impact-resistant and high-temperature resistant. It has good toughness and can automatically recover after large bends. Non-toxic and the first choice in Europe. It is a food-grade material and is currently the most widely used frame material. However, the frame made of TR-90 is lower in strength than titanium alloy, so it will be thicker than the alloy, resulting in an overall quality similar to that of titanium alloy.
-
PC (polycarbonate)
PC (polycarbonate) is a plastic sheet. PC frames have high strength and hardness, and are not prone to deformation. The disadvantage is also obvious that they have low toughness, are difficult to adapt to the curve of the head, and are easy to break. Generally, PC temples are used A metal wire will be added to increase toughness, which is not available in injection molded frames. PC frames are available in rich colors and can also be made translucent, so they are often used in sunglasses or fashionable and decorative glasses.
- Injection molding
Injection-molded frames are frames made of resin injection molding. This material is cheaper than sheet frames. The frames are softer and less elastic. You can see a line mark at the joint of the template, and the mirror legs are not like There is a wire like the plate. Mostly used in sunglasses, optical glasses are generally not recommended.
To sum up: If you want to pursue cost-effectiveness, choose titanium alloy. Its performance is no worse than titanium. Of course, some prices will not be cheaper than pure titanium (such as Z titanium). Others such as TR-90, memory alloy, PC board, etc. are also acceptable because they all have different material functional advantages and can express the wearing style. There are also combination spectacle frames made of the above materials, with different components made of different materials. This is usually done to reduce costs or appearance requirements. As for Monel and injection molding, they are not recommended.