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To understand crystalline polymers, I suggest you go home (if you're not already there). Now I can already imagine the confused look in your eyes. Home? Why would I need to go home? So you can check your sock drawer!
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Jetzt kostenlos anmeldenTo understand crystalline polymers, I suggest you go home (if you're not already there). Now I can already imagine the confused look in your eyes. Home? Why would I need to go home? So you can check your sock drawer!
You see some people are very clean and tidy. When they put the socks in the drawer they fold them and put them away in an orderly way. Others however aren't. There are people who are not very interested in the cleanliness and order of their sock drawer. These guys are just going to throw their socks in the drawer and leave it messy.
Polymers are like socks. Sometimes they are arranged in an orderly manner, like the socks in the drawer of people who need everything to be ordered. In this case, the polymer is called crystalline. Other times there is no order, and the polymer chains just form a big tangle like the socks of those who are messy. When this happens, the polymer is called amorphous.
In this article, we will discuss what crystalline polymers are all about, their properties, structures, examples and different types!
Fun fact: not a single polymer is completely crystalline because all crystalline polymers contain considerable amounts of amorphous material. Therefore, crystalline polymers are more accurately called semi-crystalline polymers.
How can we define crystalline polymers then?
Crystalline polymers are polymers in which some parts have crystallized in a precise order, allowing the formation of an organized solid unit.
Remember, although it is possible to create a 100% amorphous structure, it is impossible to create a 100% crystalline structure as crystalline polymers always contain a decent number of amorphous polymers.
This can be seen in the figure below, which clearly demonstrates how materials and elements are always characterized by the presence of an amorphous element:
Fig. 1: Crystalline + Amorphous in the presence of an element: https://support.3devo.com/oval-flat-shaped-filament/
Pretty standard so far no? Let's find out about its properties!
Due to their structure and temperature, crystalline polymers have a wide range of mechanical and physical characteristics:
The biggest characteristics of crystalline polymers are: high melting point, rigidity, and resistance to solvent penetration. Although the crystallinity makes polymers robust, it also lowers their resistance to impacts.
Crystalline polymers furthermore exhibit x-ray diffraction patterns due to the existence of specific lattice patterns of molecules in polymer chains and exhibit a crystalline melting temperature. X-ray diffraction, density measurements and heat of fusion are measured to determine the fraction of crystalline substances present in a particular polymer.
X-ray diffraction (XRD - X-ray diffraction) is an analytical technique that provides information on the identification of the structure and phase of crystalline materials.
On a general spectrum though, all of the properties of the semi-crystalline structures mentioned above are conditional to the degree of crystallization, to the structure of the lamellar crystallites (tiny, alternating layers of various materials), and to the size and distribution of these structures.
crystallite means an individual single crystal.
Crystalline polymers are characterized by a three-dimensional order. Now, assuming as a general rule that all molecules have a certain structural regularity, the molecules in the structures of crystalline polymers are for the most part aligned parallel to each other.
As we learned above concerning the properties of crystalline polymers, these structures can crystallize under certain conditions of temperature, pressure, voltage or by the influence of a medium, adopting fully extended forms (such as helical forms for instance).
X-ray diagrams have revealed the existence of two different parts of the structure of a crystalline polymer: an interfacial amorphous one and an ordered crystalline one, giving rise to the existence of a micellar pattern.
Take a look at the image below to have a visual representation of what was explained above (notice how they are all aligned parallel to each other too):
The lamella of a polymer crystal is made up of closely spaced and folded polymer chains (loops) that take on a mostly planar zigzag and helical form.
Fig. 2: Structure of crystalline polymers: crystalline region vs. amorphous region https://www.victrex.com/en/blog/2017/polymer-crystallinity-hpp-explained-part-
Examples of crystalline polymers are, but not limited to:
Now, all of these are just super long words that aren't super important, unless you are working with them daily. However, they are super cool because these types of materials are commonly used in the field of dentistry!
Fig. 3: Polymers used in chipped tooth repair: https://www.drjamescovan.com/treatment/cosmetic-dentistry/chipped-teeth
Semi-Crystalline polymers have mostly been used to build prosthetic items like denture bases. However, they are also employed in endodontic fillings, prosthetic teeth, restorations, cements, elastics, inlay patterns, implants, impression materials, and many more!
Look at the image here: notice the chipped teeth and then how they were fixed after bonding? The material used for bonding has a high quantity of polymers in it!
What about the polyethylene that we mentioned above? Given that it is one of the strongest currently available reinforcing fibers they are great for cosmetic dentistry as they have low density and modulus, are formed of matched polymer chains, and have high impact resistance.
Crystalline polymers are polymers in which some parts have crystallized in a precise order, allowing the formation of an organized solid unit.
Examples of crystalline polymers are, but not limited to:
The difference between crystalline and amorphous polymers is that while amorphous polymers are solids whose molecular chains are arranged in a disordered way in space, crystalline polymers are polymers in which some parts have crystallized in a precise order, allowing the formation of an organized solid unit.
Crystalline polymers
Flashcards in Crystalline Polymer15
Start learningWhat are crystalline polymers?
Crystalline polymers are polymers in which some parts have crystallized in a precise order, allowing the formation of an organized solid unit.
List the properties of crystalline polymers?
What are the biggest characteristics of crystalline polymers?
The biggest characteristics of crystalline polymers are: high melting point, rigidity, and resistance to solvent penetration.
Why are x-ray difractions, density measurements and heat of fusion are measured?
X-ray diffraction, density measurements and heat of fusion are measured to determine the fraction of crystalline substances present in a particular polymer.
The structure of a crystalline polymer is defined by what?
Crystalline polymers are characterized by a three-dimensional order with at least some chains.
How are the molecules in a crystalline structure placed within it? Are they adjacent or parallel?
parallel
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