b**m
发帖数: 18 | 1 NYLON在300C的时候可以通过INJECTION MODING加工，有没有什么POLYMER在室温甚至0C的
时候就可以被这么加工？
一般来说Molecular Weight下降Tg减小。如果NYLON的MW减小Tg是否会降到室温？
多谢。 | w********h
发帖数: 12367 | 2
MODING加工，有没有什么POLYMER在室温甚至0C的
low Tg..
PIP, -60
PBD, -100
then that molecular weight is still useful?
【在 b**m 的大作中提到】
: NYLON在300C的时候可以通过INJECTION MODING加工，有没有什么POLYMER在室温甚至0C的
: 时候就可以被这么加工？
: 一般来说Molecular Weight下降Tg减小。如果NYLON的MW减小Tg是否会降到室温？
: 多谢。
| b**m
发帖数: 18 | 3
Thanks a lot.
Are these polymers still solid at room temp? (For example, at the temperature
higher than Tg by 100C nylon is actually a liquid)
What will happen if we try to intrude nylon at room temp. using very high
pressure? Will it flow plastically?
【在 w********h 的大作中提到】
:
: MODING加工，有没有什么POLYMER在室温甚至0C的
: low Tg..
: PIP, -60
: PBD, -100
: then that molecular weight is still useful?
| w********h
发帖数: 12367 | 4
temperature
PIP and PBD surely are solid at room temperature..
I think the answer is yes. But I don't know this part in detail.
【在 b**m 的大作中提到】
:
: Thanks a lot.
: Are these polymers still solid at room temp? (For example, at the temperature
: higher than Tg by 100C nylon is actually a liquid)
: What will happen if we try to intrude nylon at room temp. using very high
: pressure? Will it flow plastically?
| b**m
发帖数: 18 | 5
Is PBD polybutadiene? Is it the official name of rubber? How come rubber (not
thermoplastics) can be extruded...? Thanks a lot.
【在 w********h 的大作中提到】
:
: temperature
: PIP and PBD surely are solid at room temperature..
: I think the answer is yes. But I don't know this part in detail.
| w********h
发帖数: 12367 | 6
(not
yes. majorly 1,4-polybutadiene.
because they have low Tg and rubberlike at room temperature.
if the room temperature is 200C, plastics also becomes rubber, ;-)
【在 b**m 的大作中提到】
:
: Is PBD polybutadiene? Is it the official name of rubber? How come rubber (not
: thermoplastics) can be extruded...? Thanks a lot.
| b**m
发帖数: 18 | 7
Correct me if I am wrong. Rubber is rubber-like because of the low crosslink
density. If the crosslink density is 0, it becomes a thermoplastic, and if the
crosslink density is high, it is a thermoset. Based on this understanding, why
a thermoplastic turns to a rubber when Tg is reached?
【在 w********h 的大作中提到】
:
: (not
: yes. majorly 1,4-polybutadiene.
: because they have low Tg and rubberlike at room temperature.
: if the room temperature is 200C, plastics also becomes rubber, ;-)
| w********h
发帖数: 12367 | 8 hehe, you must be in polymer engineering.
our languages are quite different.
my understanding is this:
your crosslink density is my entanglement molecular weight Me,
the lower Me, the higher crosslink density.
when Me=M0 (monomer molecular weight), it is crosslinked (also called
thermoset). is that right?
PS Tg=100C Me=18000g/mol
PBD Tg=-100C Me=1543g/mol
PS is normally glass-like (or thermoplastic) at room temperature because of
its high Tg.
When you increase your temperature to 130 to 150C,
yo
【在 b**m 的大作中提到】
:
: Correct me if I am wrong. Rubber is rubber-like because of the low crosslink
: density. If the crosslink density is 0, it becomes a thermoplastic, and if the
: crosslink density is high, it is a thermoset. Based on this understanding, why
: a thermoplastic turns to a rubber when Tg is reached?
| d****g
发帖数: 164 | 9 Good job! Wonderlich tongxue gave a clear explanation from the standpoint of
polymer dynamics. But I feel that you are still talking with different
languages. I have seen some rubber processing because my graduate lab in china
mainly worked on rubber, hope I can bridge your gap somehow.
Virgin PBD Rubber itself is thermoplastic before adding crosslinking agent
such as S. But PBD chains is crosslinked after the thermal processing with the
reaction of crosslink agent, thereafter it is thermoset. B
【在 w********h 的大作中提到】
: hehe, you must be in polymer engineering.
: our languages are quite different.
: my understanding is this:
: your crosslink density is my entanglement molecular weight Me,
: the lower Me, the higher crosslink density.
: when Me=M0 (monomer molecular weight), it is crosslinked (also called
: thermoset). is that right?
: PS Tg=100C Me=18000g/mol
: PBD Tg=-100C Me=1543g/mol
: PS is normally glass-like (or thermoplastic) at room temperature because of
| w********h
发帖数: 12367 | 10
china
the
yes. I am not talking about crosslinked (even slightly crosslinked) PBD.
yes, viscoelasticity.
of
【在 d****g 的大作中提到】
: Good job! Wonderlich tongxue gave a clear explanation from the standpoint of
: polymer dynamics. But I feel that you are still talking with different
: languages. I have seen some rubber processing because my graduate lab in china
: mainly worked on rubber, hope I can bridge your gap somehow.
: Virgin PBD Rubber itself is thermoplastic before adding crosslinking agent
: such as S. But PBD chains is crosslinked after the thermal processing with the
: reaction of crosslink agent, thereafter it is thermoset. B
| b**m
发帖数: 18 | 11
of
Thank you so much, wonderlich and dafeng. You two debugged a long-time
misunderstanding in my mind. :-)
BTW, sometimes we classify polymers into three catagories: thermoplastics,
rubber, and thermosets. In this case, "rubber" is refered to the cross-linked
rubber. Is this correct? The difference between the three is mainly the
cross-link density.
polymer
this
【在 w********h 的大作中提到】
:
: china
: the
: yes. I am not talking about crosslinked (even slightly crosslinked) PBD.
: yes, viscoelasticity.
: of
| d****g
发帖数: 164 | 12 Not exactly, I think this is the origin of your confusion. thermoplastic and
thermoset are talking about the repeating processability of plastics. I think
crosslink density is usually specific for rubbers.
It might be a convenient to manage the knowledge with familiar concepts, but
it is not necessary to be accurate. I encourage you to check a polymer physics
text for the accurate answer.
standpoint
agent
with
still
is
cross-linked
crosslinking).
【在 b**m 的大作中提到】
:
: of
: Thank you so much, wonderlich and dafeng. You two debugged a long-time
: misunderstanding in my mind. :-)
: BTW, sometimes we classify polymers into three catagories: thermoplastics,
: rubber, and thermosets. In this case, "rubber" is refered to the cross-linked
: rubber. Is this correct? The difference between the three is mainly the
: cross-link density.
: polymer
: this
| c*******n
发帖数: 1648 | 13 comments, just because I was a polymer engineer before. Nylon can be
extruded just above its melting temp, not necessary at as high as 300C. Think
about their molecular weight and rheological curves. Not much relate to Tg.
Most of properties relate to crystallizations and h-bonds. Of course polymers
can be processed at room temp. Check rubber injection molding work or anybody
you know in Isayev's group. Even nylon solid can be processed at room
temperatures by pulverniztion using a specific extr
【在 b**m 的大作中提到】
:
: of
: Thank you so much, wonderlich and dafeng. You two debugged a long-time
: misunderstanding in my mind. :-)
: BTW, sometimes we classify polymers into three catagories: thermoplastics,
: rubber, and thermosets. In this case, "rubber" is refered to the cross-linked
: rubber. Is this correct? The difference between the three is mainly the
: cross-link density.
: polymer
: this
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