Thank you for creating this video. I am an engineer in support of a mechanical test lab. We test both metals and polymers. When we test metal per ASTM E8, we run the test with strain control through yield; but when we test polymers per ASTM D638 we use a fixed speed and simply measure the strain. We perform the polymer test on the same materials, using different sized dog bones. We test the Type IV at 1 in/min and the type V at 0.5 in/min. Doing so provides statistically different results. My theory is that this is because the two different dog bone sizes are being strained at different rates, and testing with strain control, rather than fixed speed might bring these results closer together, however the guidance documents require the test to be performed at a fixed speed. Does anyone know why poly tensile testing is done at fixed speed rather than by strain control?
Hi Philip, Since metal and polymers are intrinsically different and they go through different microstructure change during deformation, we believe they are tested at different condition. Since, polymer show viscoelastic deformation which means time dependent deformation, testing speed definitely going to affect their modulus and yield point. The probable reason for using different speed for different test is their sample dimension. Therefore, when we report physical properties of a polymer, it is important to mention the test conditions, like test speed, temperature and also humidity. I hope it help to clarify little bite.
Excellent ! thank you but I believe that you avoid confusion when you wrote brittleness ( elongation at break) . looks like you are saying the brittleness = elongation at break, and you shouldn't explain by reverse mode. This is just my opinion. I spent some time with this approach
Yes. Same stress strain curve is obtained for compression test only the values differ. In tensile test material fails at weakest point whereas in compression test material fails at strongest point.
sir, can you explained the brittleness for polymer. as in metal brittle are that which has very less yeilding. and please explain how C graph has more brittleness.
Hi Aakash, definition of brittleness for polymer is also same as metal. For polymer, a general thumb rule is, if it is showing less than 5% deformation before failure/rupture, it is considered as brittle. Pure polymers are usually not brittle but when fillers are mixed with it, its flexibility deteriorates and at very high filler loading, it may break before 5% deformation. And C graph is actually list brittleness since the ranking is based on elongation at break of the material. C plot shows highest elongation at break so it is least brittle or not brittle at all.
Yes, brittle is the opposite of ductile but stiffness and brittleness is different. In casual terms they seems same but stiffness is the measure of resistance to deformation where as brittleness is measure by the amount of deformation (elongation at break). A high molecular weight polymer with high crystallinity can be both stiff and ductile where as a low molecular weight polymer with very high crystallinity can be stiff and brittle. The reason is long chain polymers will have long chains segment in the amorphous region which will be able to deform at higher load.
brittleness means measure of elongation at break ... so if elongation is more it is less brittle or more brittle. Because in example, 'c' has has more brittleness but has more elongation before break?? please clarify.
For polymer, a general thumb rule is, if it is showing less than 5% deformation before failure/rupture, it is considered as brittle. Pure polymers are usually not brittle but when fillers are mixed with it, its flexibility deteriorates and at very high filler loading, it may break before 5% deformation. And C graph is actually list brittleness since the ranking is based on elongation at break of the material. C plot shows highest elongation at break so it is least brittle or not brittle at all.
Thank you so much for this clear and interesting explanation of the mechanical properties of polymers! It's very useful for my education about polymers and I will definitely watch more of your videos.
Hello sir. The video is more effective for learning and for understanding the concept. Still i am not satisfied with the brittleness order. The point at which the curve stops is breaking and the material which breaks without elongation is brittle in nature. Then how come sample C is more brittle.
Hi, you can start with POLYMER SCIENCE, By Vasant R. Gowariker, N. V. Viswanathan. and then move to POLYMER SCIENCE AND TECHNOLOGY by Robert O. Ebewele
I watch it today. Easy and clear explanation of the confusing terms. Thank you!
Glad it was helpful!
This is an excellent, clear and very approachable lecture, thank you very much!
Thank you for your feedback!
Thank you for creating this video. I am an engineer in support of a mechanical test lab. We test both metals and polymers. When we test metal per ASTM E8, we run the test with strain control through yield; but when we test polymers per ASTM D638 we use a fixed speed and simply measure the strain. We perform the polymer test on the same materials, using different sized dog bones. We test the Type IV at 1 in/min and the type V at 0.5 in/min. Doing so provides statistically different results. My theory is that this is because the two different dog bone sizes are being strained at different rates, and testing with strain control, rather than fixed speed might bring these results closer together, however the guidance documents require the test to be performed at a fixed speed. Does anyone know why poly tensile testing is done at fixed speed rather than by strain control?
Hi Philip, Since metal and polymers are intrinsically different and they go through different microstructure change during deformation, we believe they are tested at different condition. Since, polymer show viscoelastic deformation which means time dependent deformation, testing speed definitely going to affect their modulus and yield point. The probable reason for using different speed for different test is their sample dimension. Therefore, when we report physical properties of a polymer, it is important to mention the test conditions, like test speed, temperature and also humidity. I hope it help to clarify little bite.
I can't find the second part Sir, kindly share the link.
Ur explanation is too good ....
Thanks a lot 😊
Good explanation, tq so much.
Welcome 😊
Informative video
Thanks
great explanation sir.
Thanks for the feedback!
Awesome Content.
Thanks for feedback.
good, I like 👍
Sir......for polymer electrolyte....which property plays a vital role
Excellent ! thank you but I believe that you avoid confusion when you wrote brittleness ( elongation at break) . looks like you are saying the brittleness = elongation at break, and you shouldn't explain by reverse mode. This is just my opinion. I spent some time with this approach
Thank you for your comment. In future video, we will try to explain in both ways.
Please upload more vedios on this topic
Like:-
Selection of polymer,recyclong of polymer ,
Sure. Thanks for your suggestion.
sample X has more tensile strength then sample Y what can you say about its growth rate Why?
I didn't find next video, so fom where i can get next video link sir ....
I want videos on biomedical polymers like contact lens, dental,artificial heart,kidney,skin and blood cells polymer
We will try add these polymers. Thanks for the comment.
I m just watching ur vdos u r best in ploymer world
is this the same curve we can obtain after compression test also for polymers
Yes. Same stress strain curve is obtained for compression test only the values differ. In tensile test material fails at weakest point whereas in compression test material fails at strongest point.
sir, can you explained the brittleness for polymer. as in metal brittle are that which has very less yeilding. and please explain how C graph has more brittleness.
Hi Aakash, definition of brittleness for polymer is also same as metal. For polymer, a general thumb rule is, if it is showing less than 5% deformation before failure/rupture, it is considered as brittle. Pure polymers are usually not brittle but when fillers are mixed with it, its flexibility deteriorates and at very high filler loading, it may break before 5% deformation.
And C graph is actually list brittleness since the ranking is based on elongation at break of the material. C plot shows highest elongation at break so it is least brittle or not brittle at all.
Hello, excellent!
I have a question:
How to increase hardness in thermoplastic??
Hardness of thermoplastics can be improved either by mixing inorganic fillers or blending with harder polymers
I don't get how material C is the most brittle. Why isn't B the most brittle?
The order given is for elongation at break so brittleness order will be reverse of that.
Thank you for explanation.
I have some questions. Can we determine yield strength of polymer by using 0.2% offset method (like metal) ?
No
shouldn't the brittleness be the other way around?
The order given is for elongation at break so brittleness order will be reverse of that.
high stiffness polymer = high brittleness. right? brittle is the opposite of ductile material
Yes, brittle is the opposite of ductile but stiffness and brittleness is different. In casual terms they seems same but stiffness is the measure of resistance to deformation where as brittleness is measure by the amount of deformation (elongation at break). A high molecular weight polymer with high crystallinity can be both stiff and ductile where as a low molecular weight polymer with very high crystallinity can be stiff and brittle. The reason is long chain polymers will have long chains segment in the amorphous region which will be able to deform at higher load.
brittleness means measure of elongation at break ... so if elongation is more it is less brittle or more brittle. Because in example, 'c' has has more brittleness but has more elongation before break?? please clarify.
For polymer, a general thumb rule is, if it is showing less than 5% deformation before failure/rupture, it is considered as brittle. Pure polymers are usually not brittle but when fillers are mixed with it, its flexibility deteriorates and at very high filler loading, it may break before 5% deformation.
And C graph is actually list brittleness since the ranking is based on elongation at break of the material. C plot shows highest elongation at break so it is least brittle or not brittle at all.
@@PolymerWorld thankyou
@@PolymerWorld please upload the next part sir
Thank you so much for this clear and interesting explanation of the mechanical properties of polymers! It's very useful for my education about polymers and I will definitely watch more of your videos.
Thanks for feedback. Glad it was helpful!
Hello sir. The video is more effective for learning and for understanding the concept. Still i am not satisfied with the brittleness order. The point at which the curve stops is breaking and the material which breaks without elongation is brittle in nature. Then how come sample C is more brittle.
The order given is for elongation at break so brittleness order will be reverse of that. Hope it clarifies the confusion.
@@PolymerWorld % elongation is a measure of ductility. Sample c is having highest ductility and least brittleness.
my lord = very good =please suggest a book = simple book for first reading =thank u my lord
Hi, you can start with POLYMER SCIENCE, By Vasant R. Gowariker, N. V. Viswanathan. and then move to POLYMER SCIENCE AND TECHNOLOGY by Robert O. Ebewele
I think brittleness order is wrong
The order given is for elongation at break so brittleness order will be reverse of that. Hope it clarifies the confusion.
@@PolymerWorld ok thank you for clearing my doubt
Sirji pp article ( injection moulding crates) ko soft banana ho toh kon sa polymer mix karna hota hai..jaise hd mein ld ta lldp dalte hai
Adding rubber in PP reduces it's rigidity.
Dear Sir/Ma'm your videos are very informative. I am preparing for GATE exam can you also bring videos for material science. It will be very helpful
We believe in providing quality video and materials science is not our field of expertise.
Thanks a lot ❤️
Finally understood the logic
Glad to hear that it was helpful for you.
Excellent explanation.. Please upload 2nd part
Thanks for watching! Will post more videos soon.