[hypervalent_iodine]

ben1793, on 18 February 2012 - 06:37 PM, said:

Ahhh, thank you, never realised that
I will use the link you sent me for the images of the alpha, beta crystal stuctures.
After looking at what you said about the crystal structure being related to atomic structure, would this mean just like crystal structures change at different tempratures the atomic structure would also change?

The atomic structure would not change, it would still be SiO₄, but the way they arrange them selves (i.e. the crystal structure) might.

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I am also wondering, how would the sturcture effect the strength of the material for example I mean like the alpha and beta crystal structures for quartz, how would the different structures effect the strength and other properties of the material?

It can change it quite a lot. The best example of this is carbon. In one arrangement you get graphite, which consists of layers of carbon sheets and which is flakey and easy to break. In another arrangement, you get diamond. As for the quartz, I don't really know. I would say not very much. The only difference between the two is that one part of the crystal structure is twisted; they way they are linked is exactly the same. In diamond vs. graphite, they way they are linked/bonded together is very different, giving rise to the huge differences in their physical properties.

[ben1793]

I just had a look at the diamond and graphite structures and it amazes me that they both are made of carbon atoms and just because the structure is different one is the hardest material known to man and the other is the weak material used in pencils...WOW

Thank you for the help

So would it be possible to draw polyethylene as an atomic structure:

I mean I could draw two carbon atoms with four hydrogen atoms but how would I draw the ( )n

[hypervalent_iodine]

Yes, but be aware that the structure actually looks like this:



Image drawn myself.


Drawing conventions in organic chemistry are designed so we don't have to spend our lives writing out the letters C and H over and over again (also to reduce clutter). You'll often see images that are literally just a bunch of zig-zag lines. They might not look like much, but believe it or not, these do actually hold quite a lot of chemical information in them. In you above image, the ends of the lines coming out of the parentheses represent CH₃ groups.

[ben1793]

I was looking at the trigonal structure for the quartz crystal, do you know of any advantages or disadvantages of the structure?

Also you said the atomic structure never changes only the crystal structure will change, would this be the same for fibre glass? Is there no way to get pure fibre glass without any added atoms? What would be the most common structure for fibre glass?

Thank you

[hypervalent_iodine]

ben1793, on 19 February 2012 - 04:49 PM, said:

I was looking at the trigonal structure for the quartz crystal, do you know of any advantages or disadvantages of the structure?

This is where it starts to get to the limit of my knowledge. I don't know of any advantages, per say. They are chiral, which means that their mirror images are non-superimposable onto on another the same way that your hands are (i.e. your hands are mirror images of each other and if you try to place one hand on top of the other, it won't be superimposable). This means that they can rotate the plane of polarised light to some degree and are in that sense, optically active. That's my best guess, though it doesn't answer your question very well.

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Also you said the atomic structure never changes only the crystal structure will change, would this be the same for fibre glass? Is there no way to get pure fibre glass without any added atoms? What would be the most common structure for fibre glass?

Thank you

Nope. Fibre glass consists polymer reinforced glass fibres; usually they use co-polymers like the epoxy one I linked you.

[ben1793]

//upload.wikimedia.org/wikipedia/commons/thumb/0/07/Epoxy_prepolymer_chemical_structure.png/798px-Epoxy_prepolymer_chemical_structure.png

I went on the epoxy link and found this, how would I draw it, what are the hexagons, what is the OH, does the O stand for oxygen or somethin else?
Is there any crystal structures for the fibre glass epoxy?

Also, would you not know of any advantages for the trigonal strucure such as the structure would make the material brittle, like you said in the past graphite is a layered crystal structure so it is very brittle and breaks easy.

This post has been edited by ben1793: 19 February 2012 - 10:34 PM

[hypervalent_iodine]

ben1793, on 19 February 2012 - 10:31 PM, said:

//upload.wikimedia.org/wikipedia/commons/thumb/0/07/Epoxy_prepolymer_chemical_structure.png/798px-Epoxy_prepolymer_chemical_structure.png

I went on the epoxy link and found this, how would I draw it, what are the hexagons, what is the OH, does the O stand for oxygen or somethin else?
Is there any crystal structures for the fibre glass epoxy?

Each point is a carbon with a certain number of hydrogens attached to them (each carbon will have four bonds, so you should be able to work out how many hydrogens are attached to each carbon). The hexagons with the double bonds are called phenyl rings and yes, the O is for oxygen. The OH group is called a hydroxyl group (a hydrogen bound to an oxygen). How to read the above structure properly is a lot for me to write up. Lucky for us, other people have already taken the liberty to writing it. Have a read of this website.

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Also, would you not know of any advantages for the trigonal strucure such as the structure would make the material brittle, like you said in the past graphite is a layered crystal structure so it is very brittle and breaks easy.

I'm sorry, I don't really know. As I said, I'm an organic chemist and this is all very much outside of my area. I suppose a prudent question would be, compared to what?

[ben1793]

Thank you for your help.

Does the Epoxy Fibre glass have any crystal structures or is it amorphous?

Also what is a commonly used polymer for shape memory polymers that would be suitable for my research?

This post has been edited by ben1793: 20 February 2012 - 06:21 PM

[hypervalent_iodine]

ben1793, on 20 February 2012 - 06:16 PM, said:

Thank you for your help.

Does the Epoxy Fibre glass have any crystal structures or is it amorphous?

You won't find a crystal structure for it.

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Also what is a commonly used polymer for shape memory polymers that would be suitable for my research?

I already gave you a list. Please read back on the thread.

[hypervalent_iodine]

ben1793, on 22 February 2012 - 02:44 PM, said:

I have read the wikipedia you sent me on shape memory polymers and found this:
http://upload.wikime..._norbornene.jpg

From what I read that is polynorbornene, and it says it is amorphous, this means like you said in the past it has no constant crystal structure but what I was wondering is would this have no structure at all because I mean is it not possible to take the structure at certian points like at when the material is at its ordionary form, also would using the example on the left hand side be ok for a atomic structure image for shape memory polymer?

Thank you.

Definitely amorphous. If it were crystalline, the material would be a lot more brittle and rigid, which is probably not so good for something marketed as foam. The picture you linked there looks a little odd and might be a bit confusing for you. You'll notice that there are diagonal lines that cut through the structure in between each monomer unit (i.e. between each repeat of the basic chemical unit). If you have a look at the first image, it cuts between two monomer units and each of them is slightly different - the double bond geometry has changed circled in my picture below).



What this means is that the polymer consists of repeating units of either the first or second type and they occur at random intervals throughout the polymer structure. To illustrate this better, if we say the first type of unit is called A and the second one is B, the polymer might look like this:





You can draw it how they have in the image if you'd like (avoid the second one, those silsesquioxane things are a pain to draw) or you could simply draw this:

This post has been edited by hypervalent_iodine: 22 February 2012 - 03:46 PM

[ben1793]

Thank you so much for your help, I would have never understood this without learning from you, thank you.

I just ran into something and really wanted to know about it, I enjoy working on cars as a hobby and they have something called a lambda sensor, this tells the car computer system how much oxygen is in the exhaust system, now I was researching smart materials and ran into something called peizoelectric materials, the lambda sensors on the cars used ziconium dioxide, this material reacts to the oxygen creating a voltage, would this also be classified as a peizoelectricl material?

Sorry I would have asked this question on yahoo but I have reached my daily limit and was wondering if you would know about this.

Thank you.

[hypervalent_iodine]

I'm not really familiar with piezoelectrics. Feel free to make a thread on it in the Engineering forum though and I'm sure someone else will be able to help.

[ben1793]

Its ok, it was just a question I have been wondering about since I have seen peizo materials, I will make a thread on the engineering forum, thank you for your help.