Polycarbonate lenses problems cracking

Some of the lenses lasted only 23 days before large cracks appeared one from below and one from above. A lens affected by crazing may have cracking or dimpling. Additionally, trivex and polycarbonate naturally block most uv light 385 nanometers and below and do not need the application of a uv coating. And finally, as is the case with so many properties, molecular weight is. The higher molecular weight materials will resist stress cracking for much longer and at higher critical stress levels. Due to the light weight and flexibility of polycarbonate, these lenses are easier to remove and install. As little as 10 percent glass fiber can reduce problems with stress cracking in materials like polycarbonate and polysulfone.

It is available in clear and opaque forms, making it the ideal choice for construction and securityrelated purposes. Also, at the optical i work at, ive seen quite a few lnses cracking due to the polycarbonate material itself. The first polycarbonate lenses were made in the 1970s for safety glasses. Prescription safety glasses with polycarbonate lenses.

The sinter apx lens has been developed to overcome the well known problems polycarbonate lenses encounter in mounting stress cracking in metal frames, migration crazing from acetate frames and electrostatic stickers limiting their use in high quality sophisticated frame designs. Thinner and lighter than plastic, polycarbonate lenses are used in most. For this reason, clear surfaces such as a polycarbonate lenses in a pair of glasses will typically be coated with a scratchresistant layer for protection. Our polycarbonate lenses are manufactured with proprietary. Has anyone had problems with high minus poly lenses that crack. I dont think cheap polycarbonate is out of the question here. This polycarbonate is not highly solvent resistent, and should show greater stress cracking tendency to develop conservative cleaning solvents. The take away is that the plastic lenses andor coatings are very heat sensitive. Unlike most other plastics, polycarbonate is capable of undergoing large hot moulding deformations without.

The polycarbonate used was a colorless, transparent makrolon 2600 from mobay corporation. Antireflective coatings can be applied to the back of sunglass lenses 2. Cracks in lenses cannot be repaired and must be replaced immediately to prevent. Plano and prescription polycarbonate lenses offer the best impact protection and should be used whenever possible. Your professional optician can discuss the pros and cons. These lenses are fashionable, light weight, and thin. Trivex lenses are designed to match or exceed the toughness and clarity of optical polycarbonate lenses hellem, 2019. Polycarbonate lenses are less likely to shatter in the fashion that silica glass does.

Many sunglasses manufacturers choose polycarbonate because it can be easily shaped without problems like cracking or splitting, resulting in. Our polycarbonate lenses are manufactured with proprietary, fourthgeneration waterwhite polycarbonate resins, are up to 50% lighter and thinner than plastic alternatives and 10 times more impactresistant. Feb 08, 2011 many sunglasses manufacturers choose polycarbonate because it can be easily shaped without problems like cracking or splitting, resulting in extremely lightweight, distortionfree, fashionable glasses that feature all of the health benefits doctors recommend. It was developed in 2001 by ppg industries as an alternative to polycarbonate.

If, for any reason, you are unable to follow the recommendations you should ask yourself why and correct the problem at its roots. A lens with high impact resistance is less prone to cracking or shattering. Theyre made out of polycarbonate rather than the plastic of my older ones. Why do my daughters polycarbonate lenses keep on cracking. High minus lenses for nearsightedness can cause some cosmetic problems and visual distortion.

Most antireflective coating manufacturers offer a one or twoyear warranty on their products, according to certified optician renee bentley, aboc. Would plastic be a better choice for amateur astronomy. Cr39 or a traditional plastic lens is the most widely available material and has. These microthin layers consist of zirconiumdioxide, titaniumdioxide, aluminumoxide or silica dioxide. To remove eyeglass lens crazing, the surface of the lens must be resurfaced with nonreflective coating by an eye care professional. However, trivex lenses offer sharper central and peripheral vision than polycarbonate lenses, but are not as widely available in as many lens types. Safety glass lenses must be able to withstand such strikes without shattering or cracking. Many eye care practitioners insist on polycarbonate. Although polycarbonate rates high for impact strength when compared to abs, polyvinyl. Processing polycarbonate at the manufacturers recommendations is the key to stressfree and crackresistant parts.

Do you need single vision, progressive noline lenses, lined bifocals or trifocals. Because they are less likely to fracture than regular plastic lenses, polycarbonate lenses also are a good choice for rimless eyewear designs where the lenses are attached to the frame components with drill mountings. Im not cracking up, but my glasses are fracture lense. Your guide to eyeglass lens materials vsp vision care. A common plastic comes under scrutiny health encyclopedia. They are also lab favorites for use in rimless frames, because. Lens materials such as trivex are far less likely to fall prey to stress fractures. Aug 28, 2017 do polycarbonate lenses have uv protection. Polycarbonate material exhibits aromatic sensitivity or is prone to absorb odors, according to the plastics web. Impact resistance is a measure of a lens materials ability to hold up under pressure, and in this regard polycarbonate is much stronger than plastic. An exorcism to get rid of glassescracking poltergeist. Polycarbonate cracking polymer engineering engtips.

Because people have different problems with their vision or require certain characteristics from their glasses lenses, eyeglass companies manufacture specific. Possibilities of why a polycarbonate pc part is cracking. Does wearing glasses with a broken lens harm your eye sight. Trivex lenses are made from a urethanebased monomer. After discovering this i was immediately convinced that this was my problem, and i was very angry with lenscrafters for pushing the polycarbonate lenses on me, and making plastic lenses seeming like. Polycarbonate is a thermoplastic that is exceedingly tough, resistant to ultraviolet rays, and provides an attractive look. This polycarbonate is not highly solvent resistent, and should show greater stress cracking tendency to. Trivex lenses are made from a lightweight, impactresistant material. Three of my trivex glasses lenses have cracked, what is going on.

Lenscrafters calls their poly lenses featherweights. Plastic lenses may be thinner than polycarbonate lenses, but polycarbonate is lighter in weight and that makes them. Jul 27, 2017 although nonreflective coating effectively reduces headlight glare and helps to reduce eyestrain for computer users, it also causes the lenses to smudge and craze easily. Common glasses problems and solutions davidson eye. Analysis of polycarbonate stress cracking and cleaning. Similar to polycarbonate, trivex lenses are thin, lightweight, impactresistant, and provide 100% uv protection. While all glasses are susceptible to heat damage, plastic frames are more. The engineers at crescent plastics can help you select the best lighting lenses that meet the demands of your application. If the lens material has been damaged, the coating process must begin anew with another lens. Crazing can be induced at moderate to high stress levels by low molecular weight hydrocarbons. Problems with the antireflective coating on glasses.

They are also lab favorites for use in rimless frames, because polycarbonate lenses can be easily drilled and resist cracking around the drill holes. It will not harm your eye sight, but it creates problem for your eyes, it is difficult for you to. In fact, less than six percent of glasses sold today are made of actual glass. Although polycarbonate is known for its high impact resistance, it is very susceptible to scratching. At that point, i can also request that they switch to plastic. A corrective lens is a lens typically worn in front of the eye to improve vision. The tiny cracks should not be a problem, but the optical shop that made the lenses should do. We observe cracks in proximity of possible welding lines areas and near the snap fit opening, they usually appear after few days since the snapfit assembly. However, it is also extremely sensitive to liquids that come in contact with it and will become weakened and crack. Most polycarbonate eyeglass lenses come with a factoryapplied, scratchresistant coating to keep the lenses clear for as long as possible, even when worn by children.

Eye glasses south jordan eye doctor optometrist glasses and. Its cylindrical and sometimes in the thinner areas some cracks appears. Polycarbonate is more impact resistant than plastic and has shatterproof properties that make them really good for kids eyewear, sports or safety wear. Unlike most other plastics, polycarbonate is capable of undergoing large hot moulding deformations without cracking or breaking. Feb 05, 2018 trivex vs polycarbonate lenses english soham bera.

Poly cracking and crazing is often caused by high drill speed. Pc is commonly used for plastic lenses in eyewear, in medical devices, automotive components, protective gear, greenhouses, digital disks cds, dvds, and bluray, and exterior lighting fixtures. They are safety lenses in that they wont outright break, but the lens material is actually quite soft, it pits and cracks fairly easily. The engineers at crescent plastics can help you select the.

I know sometimes if the lens is inserted to tight it can happen but shes. Your professional optician can discuss the pros and cons of polycarbonate and trivex lenses so you can decide which lens material is the best choice for your needs and budget. In fact, less than six percent of glasses sold today are made of actual. My lab just redid 4 of the same lens within the last 2 months. Polycarbonate lenses have an abbe value of 30, and standard cr39 lenses have an abbe value of 59. Polycarbonate is commonly used in eye protection, as well as in other projectileresistant viewing and lighting applications that would normally indicate the use of glass, but require much higher impactresistance. Its the reason you cant put stickers on your motorbike helmet. However, it can be difficult to choose between acrylic and polycarbonate lenses.

Problems with the antireflective coating on glasses healthfully. For example, standard plastic is most prone to cracking, polycarbonate is one of the biggest culprits when it comes to stress fracturing but the crack spreads slowly. In freezing temperatures it can happen as well as when the drill holes have been drilled with a dull drill or too fast with a new one, that heated up and microscopically damaged the drilled hole. A guide to chemical resistance of polycarbonate sheet.

It is also found in eyeglass lenses, compact discs, dental sealants, and plastic dinnerware. Typically a bad drill job, crap quality polycarbonate or bad fitment into frame, where the frame is applying way too much pressure is the culprit of this kind of cracking. Due to the light weight and flexibility of polycarbonate, these lenses are easier to remove and install than glass lenses, and are available in more styles of sunglasses that cannot accommodate heavy glass lenses. Certain lens coatings may reduce the impact effectiveness of polycarbonate and. Some of the main pros and cons of polycarbonate panels are listed below. Impact resistance is a measure of a lens materials ability to hold up under pressure, and in this regard.

This can lead to distortion, eyestrain, and headaches. Polycarbonate inherently blocks 100 percent uv rays without needing a special coating. This makes it a perfect material for baby bottles, refillable water bottles, sippy cups, and many other food and beverage containers. The surface of the polycarbonate lenses have a protective film but the edges and any drilled holes are untreated. The cost of polycarbonate and trivex lenses can vary considerably, but many optical stores charge more for trivex lenses than polycarbonate lenses. Polycarbonate is more impact resistant than plastic and has shatterproof properties that make them really good for kids eyewear. Use smaller lenses made out of high index plastic such as polycarbonate. Crackingcrazing may exhibit right away, but can also show up days later. Next select single vision, noline progressive, lined bifocals or trifocals. Several things however can be done to greatly alleviate the problem.

Polycarbonate is commonly used in eye protection, as well as in other projectileresistant viewing and lighting applications that would normally indicate the use of glass, but require much higher impact. Common glasses problems and solutions davidson eye associates. Eyeglass owners should understand the differences between cracks and scratches. Originally developed for the aerospace industry, polycarbonate is a large part of vision ease innovation. In freezing temperatures it can happen as well as when the drill holes. Products such as acetone and xylene may cause stress cracking even at very low stress levels and should therefore be avoided. Lighting fixtures provide bulb protection and light diffusion. Although nonreflective coating effectively reduces headlight glare and helps to reduce eyestrain for computer users, it also causes the lenses to smudge and craze easily. The plastic was received as injectionmolded plaques, 18inch thick. This is especially the case in rimless glasses where it will certainly crack at the drill mounting or when the eyeglass lens was cut too large for the frame. Many sunglasses manufacturers choose this material because it can be easily shaped without problems like cracking or splitting, resulting in extremely lightweight, distortionfree. This problem is well known and is called environmental stress cracking.

Though polycarbonate is an extremely impactresistant material, polycarbonate eyeglass lenses can be easily scratched without a protective scratchresistant coating. The heat from the drill can compromise polycarbonate, which is a heatsensitive lens material. Oct 01, 2006 when i drill polycarbonate lensesespecially ar polysometimes the lenses crack or craze. How to prevent polycarbonate rimless lenses from cracking. Mar 25, 2011 polycarbonate lenses do have a tendency to crack.

We observe cracks in proximity of possible welding lines areas. The correction for distance viewing is off, so im going to have to return them for a new pair. Im not cracking up, but my glasses are fracture lense eyeglasses. Graphical representation of ductile tearing i, hairline cracking ii, and multiple cracking iii 4. When the screw is tightened, it puts stress on the edge, therefore causing cracks. Polycarbonate is a highly durable industrial plastic, with exceptional transparency to visible light. Dec 19, 2009 the main cause of lenses cracking at the edges is the lenses were edged a hair too large. The main cause of lenses cracking at the edges is the lenses were edged a hair too large. Certain lens materials are more prone to stress fracturing than others. Dont bake your glasses in your car cary optometric. Polycarbonate lenses help protect your childs vision by holding up to roughandtumble play or sports without cracking or shattering. This kind of uv protection is an inherent part of the material theyre made out of, which glass and plastic lenses lack.

In fact, polycarbonate has ten times the impact resistance of any standard plastic material. Creators use a mold to construct the lenses in much the same way regular plastic lenses for glasses are made. Many sunglasses manufacturers choose polycarbonate because it can be easily shaped without running into problems. However, trivex lenses offer sharper central and peripheral vision than. And finally, as is the case with so many properties, molecular weight is critical. When i drill polycarbonate lensesespecially ar polysometimes the lenses crack or craze. Polycarbonate plastic is longlasting, impactresistant, and clear.

The tensile strength of trivex makes it highly resistant to cracking around drill. Besides any brokencracked lens is hazard due to sharp edges. Progressive addition or varifocal lenses provide a smooth transition from distance correction to near correction. Polycarbonate also has very good heat resistance and can be combined with flame retardant materials without significant material degradation. Im not cracking up, but my glasses are december, 2010 11. Years ago, glass was the only option available for lenses, but today a wide range of lens materials are available to match all lifestyles. Jul 27, 2017 the antireflective coating consists of layers of metal oxides applied to the front and back of glass, plastic or polycarbonate lenses. Before we get into it, lets address the clickbait title. Many sunglasses manufacturers choose polycarbonate because it can be easily shaped without problems like cracking or splitting, resulting in extremely lightweight, distortionfree.