Polyester Technology
polyester-technology: Slides from presentation by Mr. Zainul Abideen, SDM (Product Development), Gatron Industries
Electrospinning
In the electrospinning process a high voltage is used to create an electrically charged jet of polymer solution or melt, which dries or solidifies to leave a polymer fiber. One electrode is placed into the spinning solution/melt and the other attached to a collector. Electric field is subjected to the end of a capillary tube that contains the polymer fluid held by its surface tension. This induces a charge on the surface of the liquid. Mutual charge repulsion causes a force directly opposite to the surface tension. As the intensity of the electric field is increased, the hemispherical surface of the fluid at the tip of the capillary tube elongates to form a conical shape known as the Taylor cone. With increasing field, a critical value is attained when the repulsive electrostatic force overcomes the surface tension and a charged jet of fluid is ejected from the tip of the Taylor cone. The discharged polymer solution jet undergoes a whipping process wherein the solvent evaporates, leaving behind a charged polymer fiber, which lays itself randomly on a grounded collecting metal screen. In the case of the melt the discharged jet solidifies when it travels in the air and is collected on the grounded metal screen. [http://www.che.vt.edu/Wilkes/electrospinning/electrspinning.html]
Note: To avoid confusion ignore the figure on electrospinning from the above source. Instead, here is a link to a better, and more easy to understand diagram.
Spider Silk
Here’s a link to the youtube video we saw and discussed in class showing the spinning of spider silk from the milk of genetically modified goats.
whats dat ??
Comment by Furqan — May 24, 2008 @ 8:06 am
sir plz tell the following:
do we have to study the experimental results of electrospinning? (in link of electrospinning)
do we need to see in depth the compositions of fibers shown in videos like nitinol and thermoink etc?
now some questions regarding slides of mr.zainul abidin;
abt PET it is written:
Its chemical & solvent resistance is good. It has good fibre forming properties, has outstanding crease resistance and work recovery and low moisture absorption. why?
what is biaxial oriented films?
what abt different types of PET like a-pet, c-pet. do we need study these things.
sir any idea abt paper? is it hard or very hard ?
regards.
Comment by Saad bin aslam — May 29, 2008 @ 7:02 pm
No, you don’t need to worry about the experimental results of electro spinning. You need to know what it is, how it works and what sort of materials can be produced with electro spinning and where they can be used. Don’t worry about what would happen to the properties if the variables are changed.
Regarding Nitinol and thermo chromic inks, it’ll only be helpful to you if you know these things. Although I will not question you directly about how these materials work, you might be able to explain your answers better if you understand fundamentals.
Chemical and solvent resistance of polymers primarily defends on the type of chemical groups that exist in the polymer chains. You should first understand that good and bad are relative terms. It’s not that PET is resistant to hydrolysis, in the presence of alkali the ester linkages are broken which will of course lead to degradation of the polymer.
I’m a bit surprised as to why you’ve posed a question regarding the fibre forming properties of PET. Try and recall our initial lectures where we talked about the fundamentals for fibre formation. Long chains, good intermolecular (lateral) forces etc. Have a look at lecture 2 on classification and structure. Similarly outstanding crease recovery depends on the strength of the temporary lateral bonds between the polymer chains. Because the polymer chains are stacked against each other because of the strong attraction between benzene rings and consequently high degree of order, the crease recovery is good because these bonds are tough to deform.
The moisture absorption in PET is low because of the absence of polar groups which can be easily accessed by water. These are things that need to be considered when studying for the final exam. One must also be able to appreciate that the absence of polar groups and inability to access them are two very real possibilities. I have mentioned these things time and again during my lectures and it is now up to you to relate them to the subject matter.
Bi axial films can be sheets which have molecular chains aligned in two axis. This is not something for you to focus on. Most weaves are bi axial although there is a distinct class of triaxial weaves which are produced on special machines.
A-pet, C-pet and other classes are not part my course. Infact any material from Mr Abedin’s presentation that I haven’t included in my lectures will not be asked in the paper.
As far as the difficulty level of the paper is concerned, that’s again relative to understanding of the subject matter. Considering my response to your query regarding the properties of polyester, especially its moisture regain and crease recovery which we discussed in class quite extensively, you should be able to judge where you stand for yourself.
Best of luck!
Comment by Aasim — May 30, 2008 @ 5:51 am
@ saad !! chill
Comment by waqas — May 30, 2008 @ 6:07 am
salam , sir ! i know its strange that i m giving comment on this site after the ending of semster….. paper was very interesting bohat maza aya krnay main, i hope u will have the same feelings after checking the paperzzz InshAllah.. but where is model paper ? jab umair saeed de saktay hain Y cant u?? ok then thanx 4 being such a nice teacher..
Allah Hafiz.
Comment by Zarah Batool — June 1, 2008 @ 10:39 am