The Polymer Explosion: Crash Course Engineering #20
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Date: 2022-04-04
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Comments and reviews: 10
Leehams
To provide more learning, I can add a mini-crash course on some polymers and plastics info.
The big thing with plastics is that they are generally divided into 2 types: Thermoplastic and Thermoset. Thermoplastics can be melted and solidified over and over again, and do not have any cross linking, or bonding between the chains of polymers. Thermosets have lots of cross linking, and cannot be melted once solid. Thermoplastics are characterized by being melt-processable, meaning all manufacturing methods involve melting the plastic into a liquid, then forming it into the shape you want and cooling it there. Common methods of melt processing include injection molding, extrusion, and thermoforming. Thermosets, since they cannot be melted, have to be created on a chemical level in their final form. This means that you start with a liquid uncured polymer and an initiator (a chemical that causes the polymer to cure. You then mix the two parts and pour of flow the liquid mix into position, then let it cure and solidify in place. A store bought 2-part epoxy is an example of this. Carbon Fiber and glass fiber panels are examples of things made with thermosets, the fiber weave is encased in a cured thermoset.
The plastic property mentioned that might aid water flowing higher is a reference to the fact that thermoplastics, when loaded in shear like being forced through a pipe, will reduce in viscosity. Normal liquids increase viscosity and resist flow the more you push, but plastic will flow more. This is a result of the long polymer chains lining up in the direction of flow, but the alignment increases the more you push on them, resulting in lower viscosity the harder you push.
Another fun property of plastics is the glass transition. Most thermoplastics have 2 different phases of being solid. Below the glass transition temperature, they are stiff like glass, and will be brittle. Plastics like Polycarbonate, used for safety glasses and blast shields, is below its glass transition temperature at room temp. Plastics that are soft and can be belt and folded, like a ziplock bag, are above their glass transition temperature at room temp. When a plastic like polycarbonate is brought above its glass transition temperature, which is less than the melt temperature, it will become soft and wobbly.
Speaking of temperatures, thermoplastics do not have a definitive melt temperature. Metals have a temp that they always melt at, but plastics generally have a range, and some have no discernible transition from solid to liquid. Melt for a plastic is defined as the point at which there is enough heat energy for the long chains to slide past each other to allow for flow. This mainly takes the form of breaking crystalline regions of the plastic (polymers can be semi-crystalline on a microscopic scale, with small areas of crystal structures and small areas with no structure, called amorphous. The longer the chains are, the higher the melt temperature as its harder to get them to slide past. So 1 plastic can have a range of melt temps depending on the particular molecular weight, or average chain length, of that sample. Polymers that have no crystal regions are called -Amorphous-, and they have no definitive temp at which they melt. From the glass transition temperature to the point where they start to degrade and burn, they just gradually lose viscosity and stiffness. There is no hard line that says -this plastic is now liquid-. You can just turn the temp up or down a little, and it will just get a little less or more viscous.
Well there is a little deeper into the subject at a very, very brief overview with some fun info. Hopefully someone enjoys reading it!
-Source: Plastics and Composites Engineering student senior.
P. S. don't pronounce the -ph- in Terephthalate. Its to much of a mouthful so everyone in industry just skips those letters.
reply
To provide more learning, I can add a mini-crash course on some polymers and plastics info.
The big thing with plastics is that they are generally divided into 2 types: Thermoplastic and Thermoset. Thermoplastics can be melted and solidified over and over again, and do not have any cross linking, or bonding between the chains of polymers. Thermosets have lots of cross linking, and cannot be melted once solid. Thermoplastics are characterized by being melt-processable, meaning all manufacturing methods involve melting the plastic into a liquid, then forming it into the shape you want and cooling it there. Common methods of melt processing include injection molding, extrusion, and thermoforming. Thermosets, since they cannot be melted, have to be created on a chemical level in their final form. This means that you start with a liquid uncured polymer and an initiator (a chemical that causes the polymer to cure. You then mix the two parts and pour of flow the liquid mix into position, then let it cure and solidify in place. A store bought 2-part epoxy is an example of this. Carbon Fiber and glass fiber panels are examples of things made with thermosets, the fiber weave is encased in a cured thermoset.
The plastic property mentioned that might aid water flowing higher is a reference to the fact that thermoplastics, when loaded in shear like being forced through a pipe, will reduce in viscosity. Normal liquids increase viscosity and resist flow the more you push, but plastic will flow more. This is a result of the long polymer chains lining up in the direction of flow, but the alignment increases the more you push on them, resulting in lower viscosity the harder you push.
Another fun property of plastics is the glass transition. Most thermoplastics have 2 different phases of being solid. Below the glass transition temperature, they are stiff like glass, and will be brittle. Plastics like Polycarbonate, used for safety glasses and blast shields, is below its glass transition temperature at room temp. Plastics that are soft and can be belt and folded, like a ziplock bag, are above their glass transition temperature at room temp. When a plastic like polycarbonate is brought above its glass transition temperature, which is less than the melt temperature, it will become soft and wobbly.
Speaking of temperatures, thermoplastics do not have a definitive melt temperature. Metals have a temp that they always melt at, but plastics generally have a range, and some have no discernible transition from solid to liquid. Melt for a plastic is defined as the point at which there is enough heat energy for the long chains to slide past each other to allow for flow. This mainly takes the form of breaking crystalline regions of the plastic (polymers can be semi-crystalline on a microscopic scale, with small areas of crystal structures and small areas with no structure, called amorphous. The longer the chains are, the higher the melt temperature as its harder to get them to slide past. So 1 plastic can have a range of melt temps depending on the particular molecular weight, or average chain length, of that sample. Polymers that have no crystal regions are called -Amorphous-, and they have no definitive temp at which they melt. From the glass transition temperature to the point where they start to degrade and burn, they just gradually lose viscosity and stiffness. There is no hard line that says -this plastic is now liquid-. You can just turn the temp up or down a little, and it will just get a little less or more viscous.
Well there is a little deeper into the subject at a very, very brief overview with some fun info. Hopefully someone enjoys reading it!
-Source: Plastics and Composites Engineering student senior.
P. S. don't pronounce the -ph- in Terephthalate. Its to much of a mouthful so everyone in industry just skips those letters.
reply
Bry
hey, you guy should do a video on recycling and if doing so is really helping the earth. I want to know if I should start recycling more often and if that will help thefuture people by not using plastic bottles and using reusable containers actually helps. I feel like I am doing a good thing but I don't know if just a small about of people recycling and making an effort will actually help the world in the long run. I know that keeping the oceans clean as helping the sea life live a better life but is it helping humans live a better life by not using straws anymore, and reusing plastics-?
reply
hey, you guy should do a video on recycling and if doing so is really helping the earth. I want to know if I should start recycling more often and if that will help thefuture people by not using plastic bottles and using reusable containers actually helps. I feel like I am doing a good thing but I don't know if just a small about of people recycling and making an effort will actually help the world in the long run. I know that keeping the oceans clean as helping the sea life live a better life but is it helping humans live a better life by not using straws anymore, and reusing plastics-?
reply
Shanmukha
You're talking too fast and with no focus. sorry but this is video is not the standard of crash course. We could just google if we want heaps of info about polymers. Your job is to get people curious and inspired to learn more about polymers, not dumping info.
reply
You're talking too fast and with no focus. sorry but this is video is not the standard of crash course. We could just google if we want heaps of info about polymers. Your job is to get people curious and inspired to learn more about polymers, not dumping info.
reply
Andrew
The -Ghost- Army was the real invasion force to liberate France. It was led by Patton in the landings at Calais. The Normandy landings were only a diversion. Also, eat lots of carrots to improve your night-vision. ;)
reply
The -Ghost- Army was the real invasion force to liberate France. It was led by Patton in the landings at Calais. The Normandy landings were only a diversion. Also, eat lots of carrots to improve your night-vision. ;)
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Engineering
Can't wait to refer to the PVC at work as a -cylindrical tube of polyvinylchloride-. That'll teach those construction contractors to talk down to retail associates at home improvement stores.
reply
Can't wait to refer to the PVC at work as a -cylindrical tube of polyvinylchloride-. That'll teach those construction contractors to talk down to retail associates at home improvement stores.
reply
mohamed
Once around here an ink factory was on fire it took about 10 fire trucks and three refill dosers plus the HVAC system and all the fire extinguishers that can get their hands on to put it out
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Once around here an ink factory was on fire it took about 10 fire trucks and three refill dosers plus the HVAC system and all the fire extinguishers that can get their hands on to put it out
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sirBrouwer
Maybe a interesting fact. Polymers like polyethylene is one of the biggest consumers of raw sugar. I have worked at a factory that makes the raw materials for plastics. (DOW Chemical)
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Maybe a interesting fact. Polymers like polyethylene is one of the biggest consumers of raw sugar. I have worked at a factory that makes the raw materials for plastics. (DOW Chemical)
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Dan
You can work and research polymer materials following the career of Chemical or Mechanical Engineering (first is more the chemistry and production; second is their mechanical properties.
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You can work and research polymer materials following the career of Chemical or Mechanical Engineering (first is more the chemistry and production; second is their mechanical properties.
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Ryan
Firemen use standpipes to fight fires in high rise. Standpipes are usually located on the stairwells. They connect and set up on the floor below the fire and then go
reply
Firemen use standpipes to fight fires in high rise. Standpipes are usually located on the stairwells. They connect and set up on the floor below the fire and then go
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yondaime500
Fun fact: Nylon, Kevlar and Teflon were all created by the same company, DuPont. They also created Nomex (a fire-resistant fabric) and Spandex.
reply
Fun fact: Nylon, Kevlar and Teflon were all created by the same company, DuPont. They also created Nomex (a fire-resistant fabric) and Spandex.
reply
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