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9 comments
Participant

Join Date: Oct 2007
Posts: 4

Technical Information to Brazil

10/25/2007 6:51 PM

Dear Sirs,

I would like to know de critical point (temperature and pressure) of 2,4 -
toluene diisocyanate. This information will be possible ?
Thanks for all.

Best Regards,

RS Barradas
(e-mail: rsbarradas@superig.com.br)
(Rio de Janeiro / Brazil)

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Pathfinder Tags: isocyanates critical point
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Power-User

Join Date: Sep 2006
Posts: 128
Good Answers: 1
#1

Re: Technical Information to Brazil

10/27/2007 9:47 AM

I'm not sure what you mean by "critical point" for TDI. Can you explain what you are looking for? Also, are you looking for info re 65/35, 80/20 or 100 % 2,4-TDI?

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Participant

Join Date: Oct 2007
Posts: 4
#8
In reply to #1

Re: Technical Information to Brazil

10/28/2007 5:54 PM

Dear Sir,

I need the critical pressure and the critical temperatura of 2.4 toluene diisocyanate. The 80/20 is ok for me. Do you have a phase diagram of this susbstance ? I believe the answers will be there. Ok ?

Thanks a lot,

RS Barradas

(rsbarradas@superig.com.br)

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Anonymous Poster
#2

Re: Technical Information to Brazil

10/27/2007 10:08 AM

please discribe in brief your topic of discussion is different "technical information to brazil"

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Anonymous Poster
#3

Re: Technical Information to Brazil

10/27/2007 12:25 PM

Hi Everybody

Do you need thermodynamic information about this 2,4 -
toluene diisocyanate. ?

If you need critical point is 'cause the data are Pc and TC both are dimensionless

ibarron@sfmex.com

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Anonymous Poster
#4
In reply to #3

Re: Technical Information to Brazil

10/27/2007 8:28 PM

Why are the critical pressure and critical temperature dimensionless? They should be measureable properties of the pure material.

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Anonymous Poster
#5

Re: Technical Information to Brazil

10/28/2007 3:13 PM

you must know , what is critical temp/ pressure?

.The critical temperature, Tc, of a material is the temperature above which distinct liquid and gas phases do not exist. As the critical temperature is approached, the properties of the gas and liquid phases become the same resulting in only one phase: the supercritical fluid. Above the critical temperature a liquid cannot be formed by an increase in pressure, but with enough pressure a solid may be formed. The critical pressure is the vapor pressure at the critical temperature. On the diagram showing the thermodynamic properties for a given substance, the point at critical temperature and critical pressure is called the critical point of the substance. The critical molar volume is the volume of one mole of material at the critical temperature and pressure.

Critical properties vary from material to material, just as is the case for the melting point and boiling point. Critical properties for many pure substances are readily available in the literature. Obtaining critical properties for mixtures is somewhat more problematic.

Two immiscible liquids, such as oil and water, will also have a critical temperature and pressure at which the two phases will become consolute.

For pure substances, there is an inflection point in the critical isotherm on a pV diagram. This means that at the critical point:

This relation can be used to evaluate two parameters for an equation of state in terms of the critical properties.

Sometimes a set of reduced properties are defined in terms of the critical properties, ie.:

Tr = T / Tc pr = p / pc Vr = V / Vc

The principle of corresponding states indicates that substances at equal reduced pressures and temperatures have equal reduced volumes. This relationship is approximately true for many substances, but becomes increasingly inaccurate for large values of pr

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Anonymous Poster
#6

Re: Technical Information to Brazil

10/28/2007 3:33 PM

The critical temperature, Tc, of a material is the temperature above which distinct liquid and gas phases do not exist. As the critical temperature is approached, the properties of the gas and liquid phases become the same resulting in only one phase: the supercritical fluid. Above the critical temperature a liquid cannot be formed by an increase in pressure, but with enough pressure a solid may be formed. The critical pressure is the vapor pressure at the critical temperature. On the diagram showing the thermodynamic properties for a given substance, the point at critical temperature and critical pressure is called the critical point of the substance. The critical molar volume is the volume of one mole of material at the critical temperature and pressure.

Critical properties vary from material to material, just as is the case for the melting point and boiling point. Critical properties for many pure substances are readily available in the literature. Obtaining critical properties for mixtures is somewhat more problematic.

Two immiscible liquids, such as oil and water, will also have a critical temperature and pressure at which the two phases will become consolute.

Superconductivity

In superconductivity applications, critical temperature refers to the temperature below which a given material becomes superconductive.

[edit] Construction

In construction, critical temperature refers to the temperature above which structural steel loses its strength and is no longer fully capable of loadbearing support. Maintaining structural and important process steel building components below this critical temperature, which varies from country to country but is generally between 500 and 560°C, is an important function of passive fire protection.

[edit] Mathematical definition

For pure substances, there is an inflection point in the critical isotherm on a pV diagram. This means that at the critical point:

This relation can be used to evaluate two parameters for an equation of state in terms of the critical properties.

Sometimes a set of reduced properties are defined in terms of the critical properties, ie.:

Tr = T / Tc pr = p / pc Vr = V / Vc

The principle of corresponding states indicates that substances at equal reduced pressures and temperatures have equal reduced volumes. This relationship is approximately true for many substances, but becomes increasingly inaccurate for large values of pr

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Participant

Join Date: Oct 2007
Posts: 4
#7
In reply to #6

Re: Technical Information to Brazil

10/28/2007 5:49 PM

Dear Sirs,

I need the critical pressure and the critical temperatura of 2.4 toluene diisocyanate (pure substance). Do you have a phase diagram of this susbstance ? I believe the answers will be there. Ok ?

Thanks a lot,

RS Barradas

(rsbarradas@superig.com.br)

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Participant

Join Date: Oct 2007
Posts: 4
#9

Re: Technical Information to Brazil

11/14/2007 7:01 PM

Dear Sirs,

Is possible an answer about my question (my second e-mail) ?

Thanks,

RS Barradas

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