Stephanie Louise Kwolek was born on July 31, 1923 in the pittsburgh suburb of New Kensington, Pennsylvania, to Polish immigrant parents. 1923 was the beginning of the career of an Austrian art student who "ran" the United States in this capacity at this point in time, and it has to be said that the couple was indeed very prescient.
Stephanie's father, to quote a cross-talk, was a "second-hand scientist" who was passionate about the natural sciences and naturalism, a love that was rooted in Stephanie's heart, and her mother was a well-known local costume designer.
But for Stephanie, rather than exploring nature, she wants to be able to make a difference in the fashion industry like her mother. However, with years of hard work, her mother decided that Stephanie was born with an overly perfectionist personality and was not up to the line of relying on party to eat, and her father died of illness when she was 10 years old, stephanie finally decided to become a doctor and save more lives by herself.
Stephanie Louise Kwolek
Studying medicine is never easy, and high tuition fees are the first hurdle. Stephanie showed a talent for being a theorist from an early age, earning a bachelor's degree in chemistry from Carnegie Mellon University in 1946 and hoping to earn enough money from her work in chemistry-related fields to realize her medical dreams. Her mentor, William Hale Charch, offered her a job as a researcher at DuPont's Buffalo plant in New York City, the nation's largest chemical industry company that made a fortune as early as 1939 with the introduction of nylon, a well-known synthetic fiber product.
At a time when the world situation after The frequent turmoil in The world situation after World War II made the demand for ballistic materials increasing day by day, DuPont was trying to find new synthetic fibers to fill the gap in nylon materials in high-strength applications.
▍This unexpected discovery really stems from "building wheels"
Stephanie, who had just joined DuPont, had planned to save enough for tuition and run away, but research on synthetic fibers soon piqued her interest.
In 1950, Stephanie moved to Wilmington, Delaware, where DuPont was headquartered, a move that meant she would remain at DuPont to continue her career. Stephanie began working on aramid polymers in the 1950s, during which time she led the team to develop the high-temperature flame retardant fiber Nomex (Aramid 1313), which is a rare thing that this product is also a very good insulation material in addition to its excellent flame retardant properties.
DuPont logo
In 1964, anticipating an oil shortage, Stephanie's team began looking for a lightweight, high-strength fiber material at DuPont's behest to replace the steel wheels needed to make lightweight cars, while synthetic fibers were manufactured in a way that required several polymer raw materials to be melted at temperatures in excess of 200°C, and eventually a finished product for spinning was made by a spinning process.
Because it is easy to produce impurities such as liquid crystals, the melt polymerization process is the most difficult to control in the manufacturing process of synthetic fibers, so Stephanie proposed the idea of using chemical methods to polymerize in a low temperature environment of 0 °C - 40 °C.
Unexpectedly, the products of the new process exhibit properties between polymer solutions and liquid crystal solutions, and the new polymer molecules acquire a high degree of orientation of liquid crystals while tightly binding, thus exhibiting amazing physical strength. Everyone present understood the significance of the discovery, and in 1971, DuPont began bringing to market a new synthetic fiber material called Kevlar, known to modern people as "Kevlar."
The unexpected discovery also brought Stephanie to the cover of Time magazine
▍ Flying in the sky and running on the ground, there are Kevlars everywhere
As a synthetic fiber, the tensile strength of the general Kevlar spinning is about 3620 MPa, in contrast, the tensile strength of the steel wire on the crane is 1400-2000 MPa, while the density of the Kevra spinning is only 1/5 of the steel wire.
Kevlar's rigidity is attributed to the dense hydrogen bonds formed between molecules and the stacked interactions from adjacent chains, which makes the molecular structure of Kevlar fibers more compact and three-dimensional than other synthetic polymers, and the molecules of Kevlar fibers tend to form cascading planar sheets rather than filamentous structures, which is why the physical properties give them extraordinary strength.
Kevra's molecular structure: thick lines represent individual units, dashed lines represent hydrogen bonds
Kevlar was widely welcomed as soon as it was introduced, first in the manufacture of combat helmets, bulletproof masks and bulletproof vests, which were used to replace traditional steel protective structures along with composite materials such as ceramics. After verifying The Kevlar's practical effect on withstanding gunshots and explosions, the new material was quickly used to create a release liner to protect the vehicle group to absorb the kinetic energy effects generated by the explosion, a design that could effectively reduce the probability of the armor fragments collapsing inside the hull killing the occupants.
In the civilian market, Kevlar is often used to make various types of sports protective gear and labor armor, and in the recent Winter Olympic Games, the inside of the speed skater's sportswear was usually covered with Kevlar fibers to prevent secondary damage caused by being scraped by an ice knife in the event of a fall and a collision. In addition, another DuPont researcher, Jacob Lahijani, invented Kevra K149 in the 1980s as a tough synthetic fiber material used in high-end fields such as aerospace.
At present, the Kevra family has derived a total of nine different types to cope with increasingly complex use scenarios:
Kevlar K29 - for industrial products such as cables, tires and brake pads
Kevlar K49 - for the manufacture of high-strength cables and ropes
Kevlar K100 - Color version of Kevlar K29
Kevlar K119 - version with better ductility and resistance to material fatigue
Kevlar K129 - a version with enhanced toughness, mainly for military purposes
Kevlar K149 - Extremely tough and common in applications such as vehicle protection and aerospace
Kevlar AP - An upgraded version with 15% more tensile strength than kevlar K29
Kevlar KM2 - A version specialized for anti-elasticity
Kevlar XP - Lightweight Kevlar KM2 made of resin composite
Although kevlar's application range is very wide, the areas where this cutting-edge material can be used to the fullest are still quite distant for us - it can be said that kevlar may exist everywhere in life, but few people can directly see the figure of these synthetic fibers.
▍The relationship with smart phones has made many classics
If there's one thing that connects the digital lives of modern people to Kevlar in a tight and visible way, smartphones are a great example.
Looking back at the development of the surface material of smart phones, the vast majority of products are constantly swirling around the ring belt formed by "plastic-metal-glass". Although there are also minorities such as bamboo, leather, carbon fiber and so-called polycarbonate involved, these more niche materials are gradually withdrawing from the public eye due to reliability or cost issues.
In fact, in the era of the dawn of modern smartphones, smartphones made of Kevlar fibers have indeed been elegant and have achieved a series of classic models.
The first smartphone that can be traced back to Kevlar comes from Motorola, the veteran communication manufacturer seems to have a fanatical pursuit of bulletproof materials, the Motorola Droid Razr launched in October 2011 - the domestic common name of the XT910 "thin knife" - is the peak of Motorola's mobile phone commissioned to Google, this phone will be the top Texas Instruments OMAP4460 dual-core processor and other hardware into the body of only 7.1mm thickness, The protective Kevlar back cover is only 0.3mm thick, which is indeed a miracle in the industrial design of smart phones. The design of the back cover of Kevlar can reduce the thickness and weight of the whole machine to the unattainable degree of conventional materials on the basis of ensuring the strength of the fuselage structure, and has extremely strong toughness, as well as anti-wear, scratch-proof, high temperature resistance and other characteristics, but the manufacturing difficulty and cost are also rising, so no manufacturers have launched the same type of competitors.
Unsurprisingly, the XT910 was a resounding success in terms of sales and word-of-mouth, and Motorola, which tasted sweet, began to apply Kevra to the Verzion Droid product line launched with Verizon more and more frequently. Among them, the more representative are the Motorola Droid Ultra released in July 2013 and the Motorola Droid Turbo listed in October 2014, in which the former extends the Kevra fiber from the back plate to the shell manufacturing process of the whole machine, thus forming a Kevra all-inclusive appearance similar to Unibody; while the latter brings the protection performance of The Kevra to the peak of the smartphone, which is also motorola's mobility division Google's last smartphone with a Kevlar liner.
Droid Version
The romance between Motorola and Kevlar ends here, but the story of Kevlar and the smartphone seems to have reached a turning point here.
On July 28, 2015, the then green enough to still be "feel really cool" as the Slogan of the OnePlus company through a virtual reality conference to disclose its annual flagship OnePlus 2 smartphone, a variety of optional back cover materials are a major selling point of this smartphone, of which Kevlar fiber is prominently listed. Unfortunately, the trend of customized smartphones has been said to be over, and OnePlus has gradually reduced the variety of materials available in subsequent models, and Kevra has gradually changed from a component of smartphones to a common material for high-end protective cases, and almost monopolized this market segment before the emergence of liquid silicone.
Whether it's a smartphone or a protective case, the advantages of using Kevlar as the primary material are clear. In addition to the basic characteristics of extreme thinness and reliability, Kevlar can obtain the lightest grip at the same thickness and weight; and the risk of choosing this material is almost the same, poor thermal conductivity, high cost of research and development, doomed to be in the fiercely competitive domestic mobile phone market will not have too many manufacturers willing to consider.
But that doesn't mean no product dares to go against the tide – the iQOO 9 Pro "Track Edition" is such a existence.
On February 12, 2019, Vivo announced the official establishment of its sub-brand iQOO through Weibo, whose brand name comes from I quest on and on - born strong and explored. This emerging brand focusing on top performance and innovative design, while maintaining a family-style design language, each generation of products has its own unique style, and in just three years, it has also brought many surprises to the smartphone market.
As the "Super Cup" of iQOO's flagship at the beginning of this year, and a special gift for iQOO's 3rd anniversary, the iQOO 9 Pro "Track Edition" combines Kevlar and the curved design of the 3D back cover in a near-perfect form, bringing back the smartphone memories belonging to the previous generation. Looking back at the development history of the iQOO digital series, it is not difficult to see that iQOO has a long "up and down" road in the material of the mobile phone - from AG glass to plain leather, and then to today's Kevlar, compared to some manufacturers in the camera arrangement of this kind of novelty, iQOO's thinking in my opinion can be regarded as "the right direction, strong perception, excellent experience".
Of course, the choice of Kevra in 2022, in addition to differentiation, has some different meanings.
The general trend of the world, the long roll must be pendulum, the pendulum must be rolled - but the inner volume of high-end smart phones has never had the meaning of stopping, and the hardware arms race that has been fought for more than ten years is still a bloody storm. Nowadays, under the blessing of the Snapdragon 888 and Snapdragon 8 gen1 generations of electricity-eating households, the major manufacturers are frantically stacking materials inside their flagship machines, and the stacking of components is like Elsa singing "Let it Go" - the tall building is flat, not only is the internal space of the inch of land squeezed to the limit, the tonnage of smart phones is also getting heavier and heavier, and the "so half a pound" that was ridiculed a few years ago has even been lost to everyone.
In such a harsh environment, Kevlar is undoubtedly a major breakthrough in solving the problem of smartphone stacking, compared to traditional materials such as plastic, metal and glass, Kevlar has an overwhelming advantage in thickness, weight and durability. Because of the high hardness and impact resistance of The Kevlar itself, we can even let go of the dependence on the heavy protective case - I would say that the middle frame transition of the iQOO 9 Pro "Track Edition" is quite natural and smooth, the excellent grip of the four-curved design and the warm texture of the Kevra back cover can be said to be addictive for now, if you are willing to spend more money on the official broken screen insurance when purchasing, it is basically said to be "naked" worry-free.
This feeling of "being in the cage, returning to nature" is a rare heartbeat for current smartphone users, right?
Finally, Kevra is almost completely insulated, the weakening effect on mobile phone signals is infinitely close to zero, and it is currently in the period of large-scale laying of 5G networks and frequent changes in signal base stations, thanks to the rapid development of streaming media and mobile games, the user's demand for the network is incomparably high, and Kevra can perfectly avoid the interference and shielding problems of metal materials on mobile phone signals.
▍ Innovation is not easy, and it is equally difficult to make Kevlar into a back cover
The advantages of using Kevlar as the main material on smartphones are numerous, but today there is no other product with a similar design outside of the iQOO 9 Pro "Track Edition". Kevlar's high manufacturing costs are indeed a factor that cannot be ignored, but the deeper reason lies in the difficult manufacturing process of modern smartphones.
Look closely at products such as motorola Droid/Razr listed above, these smartphones either use a single piece of 2D design kevlar straight plate and other material splicing as the back cover, or cover several layers of kevlar fabric on the back cover substrate as a support to achieve so-called "integration". Today's high-end smartphones usually use a 3D back cover, and it is difficult to make a complete Kevlar plate into a curved shape without a substrate to meet the clearance requirements of the precision assembly of the back cover of the mobile phone.
This is also a challenge for iQOO, which is said to have invested millions of dollars in research and development costs.
The Kevlar 3D back cover we finally held in our hands, only the density of the woven fiber reached 600D, according to the dannier number conversion, that is, the weight of the 9000-meter length of this woven fiber is only 600 grams, and its fineness can be seen (in fact, in real life, 600D polyester Oxford cloth already has a good strength, interested friends can go to know about it).
In addition to the manufacturing accuracy required from the basis of the given finished product, the 12.34g rear cover of the iQOO 9 Pro "Track Edition" also needs to be prepreged in a special thermoset resin with good fire resistance, the 3 layers of fiber material are superimposed and then superimposed, and the 3D curved surface shape is further shaped by vacuum high-temperature vulcanization process... A total of sixteen complex processes of "7 coatings, 7 baking and 2 grinding", from the process to the quality of the finished product, can be said to live up to the name of Kevlar.
After the whole process, iQOO's Kevlar processing technology is actually somewhat similar to the above-listed "Kevlar XP - Lightweight Kevlar KM2 composed of resin composites", which is the latest and most important technology type in the Kevlar product line.
Kevlar is essentially a fabric fiber, so the edge treatment after laser cutting material is also a major problem in the manufacturing process of the iQOO 9 Pro "Track Edition" back cover. The solution given by the iQOO design team is to treat the back cover in a "micro-hemming" process, which uses a very small amount of PC resin to cover the edges of the cut-and-formed back cover and further protect the fabric fibers by spraying a matte UV paint to improve overall durability.
In addition to the extremely difficult processing, Kevlar is also a poor conductor of heat, which means that the heat generated by the operation of the smartphone is difficult to transmit to the air through the Kevlar. The design team at iQOO took this feature into account and chose a very flattering solution.
Yes, the camera module called "Panoramic Porthole" added to the back of the iQOO 9 Pro "Track Edition" is positioned above the heated part of the motherboard, and its multi-hierarchy makes the frosted aluminum alloy below act as the heat shield of the motherboard, while the AG mirror aluminum alloy above can be used as a heat shield when the user holds the mobile phone horizontally.
From this point of view, Kevlar materials are not only a repeated honing of technical strength, but also a comprehensive consideration of the design concept, which was true of Motorola in the past and iQOO today.
Innovation is never an easy task, and any progress that seems to be in a nutshell holds the potential to change the world. Time has passed, and the little girl who aspired to study medicine to save her life and the injured has become an ancient, but the Kevra she invented by chance has fulfilled her wish in a completely different way.
"I don't think there's anything more satisfying and happy than saving someone's life." ——Stephanie Louise Kwolek