24
votes
Why isn't nylon as strong as kevlar?
Kevlar is an A,B co-polymer where the monomers are terephthalic acid and 1,4-diaminobenzene. The amide linkage, together with the aromatic rings in the polymer, makes a very rigid polymeric structure ...
- 1,343
18
votes
Accepted
Is benzene a polymer of ethyne?
The scientist who coined the term polymer, Jöns Jacob Berzelius, used the word to refer to different substances which had the same empirical formula. In this sense, benzene is a polymer of ethyne (...
- 29.1k
18
votes
Accepted
What causes plastic to become brittle and can it be softened again?
Unfortunately, there is not too much to do. The original ABS substance is a copolymer made of acrylonitrile, butadiene and styrene. It is rather hard and brittle. To make it softer, some proportion of ...
- 29.5k
16
votes
Accepted
Why does lavender oil dissolve plastic?
Based on appearance and extent of deformation, your bottle is likely made of PVC plastic which is not compatible with oils. Plastic bottles are made from blow molding. This process leaves residual ...
- 12.7k
15
votes
How can I draw alpha helices in ChemDraw?
I use ChemDraw Professional 19.1.1.32. If you follow File>Open Templates>Advanced BioDraw, you will find the black helix that I have reoriented from horizontal to vertical. The red helix was ...
- 17.3k
14
votes
Can a long polymer chain interact with itself via van der Waals forces?
You have a possible answer to your question in proteins, an example which includes some long polymer chains.
Intramolecular interactions - while not necessarily the driving force for formation of a ...
- 22.7k
13
votes
Why is polyethylene not called polymethylene?
Polyethylene is prepared by polymerizing ethylene. Ethylene has a double bond, thanks to which the polymerization goes on. You could not do that with a methylene group. So the name comes after the ...
- 241
13
votes
How can I draw alpha helices in ChemDraw?
This illustration may be a combination of two images, or simply a program I don't know about. However, there are many (3D) protein visualisation programs that can show alpha-helices such as PyMol, VMD ...
- 918
12
votes
Rubber composition A13 B13 C20 F17 K11 L14
TL;DR I think you might need two more things to interpret this line: the first code part of the standard, and the standard itself - ASTM D2000 (needs to be purchased).
These descriptors are not ...
- 38.4k
11
votes
Accepted
Why is Buna-S called so?
Sodium is included in the name because it was essential in the chain polymerization that forms the rubber.
Sodium served as the initiator for the anionic polymerization.
- 44.1k
10
votes
What substance(s) will prevent superglue from hardening in its tube?
Based on what I gathered from this Wikipedia article on super glue :
Super glue is typically composed of a class of compounds called
cyanoacrylates.
Cyanoacrylates are capable of taking part in ...
- 18.8k
10
votes
Accepted
What is the purpose of the Carothers equation?
It is an equation useful for describing the behaviour of a large system, not predicting the fate of a few monomers.
Polymerization is a stochastic process—if we only have 80 monomers, the resulting ...
- 13.1k
10
votes
Why isn't nylon as strong as kevlar?
First, it's important to define what you mean by "nylon", a term which is often used generically to refer to many different aliphatic polyamides. The most common are "nylon 6" and "nylon 6,6". Nylon 6 ...
- 10.4k
10
votes
What would happen if I combined this polymer and this metal (assuming I can)
You can combine materials in two ways: chemically and mechanically.
On average, if you want to the desired physical properties to add up, you want to go mechanical way, not the chemical one.
Once the ...
- 38.4k
10
votes
Accepted
Why does polymerisation of n glycine molecules give n water molecules?
Because the product as pictured is not the complete polymer; it includes only $n$ units (called "mers") in the middle of the chain and not the complete polymer which has more than $n$ mers. ...
- 61.1k
9
votes
How do I heat my borosilicate reflux column?
That should pose no issue regarding the glass
Without images to see how unevenly you will apply the heat, I have to modify my instinctual reaction "That cannot possibly be an issue" to "Most likely ...
- 2,805
9
votes
How do I heat my borosilicate reflux column?
The first answer is great and the borosilicate glass can indeed survive harsh conditions. Here I'd like to suggest a DIY-project to improve the efficiency of the heater and make the column be warmed ...
- 38.4k
9
votes
How can I draw alpha helices in ChemDraw?
This answer is for ChemDoodle, but I think you can import SVG files into ChemDraw as well.
Just take an SVG image of an alpha helix and copy and paste it into ChemDoodle. Or go to File -> Insert ...
- 2,228
9
votes
Accepted
What do "USP 26" and "USP 42" mean?
I was able to reach the manufacturer and ask her directly. USPXX is the "edition" of the US Pharmacopeia's "exams" that a product must pass in order to be considered pharmaceutical ...
- 604
9
votes
Accepted
Orientation of amide bonds in a simplified polypeptide drawing
In this simplified way to draw the primary structure of a protein, there is no reason to enforce flipping orientation of the peptide bonds with each amino acid.
The image you show in your question was ...
- 997
8
votes
Accepted
What is an effective fabric-friendly solvent for aluminium chlorohydrate?
Bleach and baking soda are no use for removing deposits of aluminum chlorohydrates. These deposits are made of $\ce{Al(OH)_{𝑥}Cl_{(3−𝑥)}}$ and they are only soluble in somewhat concentrated $\ce{HCl}...
- 29.5k
8
votes
If polyethylene glycol (PEG) is hygroscopic, how does it protect wood?
The reason why PEG is suitable for this purpose has many reasons including the wood chemistry and degradation of wood in water.
Degraded wood usually very characteristic chemical losses. The ...
- 1,582
8
votes
Why are regular plastic bags not smell-proof?
Well, you basically answered your own question nicely with your "obvious answer" discussion. On a molecular scale, smallish molecules, like the volatile compounds that evaporate and make way to your ...
- 17.6k
8
votes
Polycyclic nitrogen network?
I searched CCDC for the infinite structures with the following building block:
where where each vertex contains any non-metal atom linked by any type of bond. The only known crystal structure that ...
- 38.4k
8
votes
Accepted
Are there chiral carbons in PVC polymers?
Yes, all polymer chains of the form - (CHR - CH2 -) are in principle chiral, the problem is that in the left and right side of the backbone in BBL - CHCl - BBR is in effect indistinguishable.
Even ...
- 12.2k
8
votes
Orientation of amide bonds in a simplified polypeptide drawing
In a Lewis structure, you are free to draw any bond angles and sketch any conformation, no matter whether it matches real bond angles and common conformations.
In the way the polypeptide is drawn in ...
- 41.3k
8
votes
Accepted
What is 'spray foam' or 'expanding foam'?
Single component spray foams work differently to two-component spray foams
The Wikipedia article on spray foams is somewhat misleading because it mostly talks about the characteristics of industrial ...
- 37.1k
8
votes
Accepted
What role does CaCl2 play in a gelation medium?
Likely, the $\ce{CaCl2}$ induces precipitation, or gelation, in this case. This is called salting out. Another example is using salting out to gel poly(N-isopropylacrylamide) for 3D-printing.
Simply ...
- 34.8k
7
votes
Accepted
for a polydisperse polymer, why is its weight average molecular weight always bigger than its number average molecular weight?
Mathematics has many examples of identities and concepts which are extremely powerful due to their simplicity, such as the pigeonhole principle and the triangle inequality. One such identity will ...
- 29.1k
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