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    CjhineePrinting  11, Male, China - 4,240 views
11
Oct 2009
11:29 PM EDT
   

Isocyanates

Isocyanates with two or more functional groups are required for the formation of polyurethane polymers. Volume wise, aromatic isocyanates account for the vast majority of global diisocyanate production. Aliphatic and cycloaliphatic isocyanates are also important building blocks for polyurethane materials, but in much smaller volumes. There are a number of reasons for this. First, the aromatically linked isocyanate group is much more reactive than the aliphatic one. Second, aromatic isocyanates are more economical to use. Aliphatic isocyanates are used only if special properties are required for the final product. For example, light stable coatings and elastomers can only be obtained with aliphatic isocyanates. Even within the same class of isocyanates, there is a significant difference in reactivity of the functional groups based on steric hindrance. In the case of 2,4-toluene diisocyanate, the isocyanate group in the para position to the methyl group is much more reactive than the isocyanate group in the ortho position.

Phosgenation of corresponding amines is the main technical process for the manufacture of isocyanates. The amine raw materials are generally manufactured by the hydrogenation of corresponding nitro compounds. For example, toluenediamine (TDA) is manufactured from dinitrotoluene, which then converted to toluene diisocyanate (TDI). Diamino diphenylmethane or methylenedianiline (MDA) is manufactured from nitrobenzene via aniline, which is then converted to diphenylmethane diisocyanate (MDI).

The two most important aromatic isocyanates are toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI). TDI consists of a mixture of the 2,4- and 2,6-diisocyanatotoluene isomers. The most important product is TDI-80 (TD-80), consisting of 80% of the 2,4-isomer and 20% of the 2,6-isomer. This blend is used extensively in the manufacture of polyurethane flexible slabstock and molded foam.12 TDI, and especially crude TDI and TDI/MDI blends can be used in rigid foam applications, but have been supplanted by polymeric MDI. TDI-polyether and TDI-polyester prepolymers are used in high performance coating and elastomer applications. Prepolymers are available that have been vacuum stripped of TDI monomer, which greatly reduces their toxicity. Diphenylmethane diisocyanate (MDI) has three isomers, 4,4'-MDI, 2,4'-MDI, and 2,2'-MDI, and is also polymerized to provide oligomers of functionality three and higher.

Only the 4,4'-MDI monomer is sold commercially as a single isomer. It is provided either as a frozen solid or flake, or in molten form, and is used to manufacture high performance prepolymers. Monomer blends, consisting of approximately 50% of the 4,4'-isomer and 50% of the 2,4'-isomer, are liquid at room temperature and are used to manufacture prepolymers for polyurea spray elastomer applications. 4,4'-MDI blends containing MDI uretonimine, carbodiimide, and allophonate moieties are also liquid at room temperature, and are used in the manufacture of integral skin and microcellular foams. 4,4'-MDI-glycol prepolymers offer increased mechanical properties in the same applications, but are prone to freezing at temperatures below 20C. Polymeric MDI (PMDI) is used in rigid pour-in-place, spray foam, and molded foam applications. Polymeric MDI that contains a very high portion of high-functionality oligomers is used to manufacture polyurethane and polyisocyanurate rigid insulation boardstock. Modified PMDI, which contains high levels of MDI monomer, is used in the production of polyurethane flexible molded and microcellular foam. The relative percentage of the 4,4'- and 2,4'- isomers is adjusted to change the reactivity and storage stability of the isocyanate blend, as well as the firmness and other physical properties of the finished goods. Other aromatic isocyanate include p-phenylene diisocyante (PPDI), naphthalene diisocyanate (NDI), and o-tolidine diisocyanate (TODI).

The most important aliphatic and cycloaliphatic isocyanates are 1,6-hexamethylene diisocyanate (HDI), 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (isophorone diisocyanate, IPDI), and 4,4'-diisocyanato dicyclohexylmethane (H12MDI). They are used to produce light stable, non-yellowing polyurethane coatings and elastomers. Because of their toxicity, aliphatic isocyanate monomers are converted into prepolymers, biurets, dimers, and trimers for commercial use. HDI adducts are used extensively for weather and abrasion resistant coatings and lacquers. IPDI is used in the manufacture of coatings, elastomeric adhesives and sealants. H12MDI prepolymers are used to produce high performance coatings and elastomers with optical clarity and hydrolysis resistance. Other aliphatic isocyanates include cyclohexane diisocyanate (CHDI), tetramethylxylene diisocyanate (TMXDI), and 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI).

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    irene  23, Female, New York, USA - 4,227 views
01
Sep 2007
2:42 AM EDT
   

Now he is mad I warned him that I would hurt hi if he eey hurt yy friend or me again I would hurt him
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    jacychain77  36, Male, United Kingdom - 4,227 views
15
May 2018
11:09 AM IST
   

Modern teaching is a rational and conscious activity

Modern teaching is a rational and conscious activity
The major difference between the modern teaching and the medieval teaching is not only manifested in different purposes, but also reflected in the working principle. Medieval teaching is mainly guided by the individual experience and experience of teachers. Teachers do not specifically study how to teach. No one specifically studies the principles and techniques of teaching. Therefore, medieval teaching is empirical and emotional. Read more
Tags: education
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    Guoxiaosi88888888  23, Female, China - 4,226 views
24
May 2011
6:00 PM EST
   

dream log 11

May 20, 2011 2:23am

Had a dream Phong drove to my house for something (I don't know what for). �Also Stewart was in my dream, like he came from behind me and gave me a hug. �He then says that he misses me. �Now...at the very beginning of the dream, Isaac calls me (I don't know what for, but oh well). �Also when Phong drives away (in a shiny new looking red car) some other people were leaving too (I don't knew who). �During the part where Phong was at my house, Tiffany was there too. �So I'm guessing Tiffany is going to see Phong soon and Stewart is still a butthead. �Oh and when Phong was leaving, I said, "Peac-e" and he did too :3
Tags: dream, log
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    Hals  24, Female, Maryland, USA - 4,215 views
27
Jun 2008
5:29 PM EDT
   

Well no one responded to my other entry, but what ever, I don't really care. It is finally summer and it is so exciting. June and July is filled up but August is completely empty. My dog tore his acl AGAIN, but this time it was the other leg. He has to get another expensive surgery, less money for college!

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    ilovegaarakun  29, Female, Virginia, USA - 4,210 views
27
Nov 2007
9:55 AM EDT
   

"He who trims himself to suit everyone will soon whittle himself away." - Raymond Hull

my thanksgiving was horrible because of the same reason last night was. i'm not even going into thanksgiving, but its pretty much the same fucking shit as last night except i was actually there in the car to witness it. alright, so last night i was supposed to go to a hooka bar with Byron; just the two of us. he texts me in 7th period and asks if it was okay if Shan goes too and i said it was cool. so we were in the car on the way to the bar and they almost immediately started a series of the most immature arguments. it started off as just a quarrel over something trivial, but then led to practically a screaming match. at least he was yelling. i didn't know what to do, like i couldn't get a word in edgewise during the whole thing and not 10 minutes away from my house, Byron demanded that he be let out of the car and slammed the door on the way out like some kind of child. Shan and I decided to go anyway, even though the only thing we did while we were there was talk about how immature and stupid and exhausting the whole thing was. After the two of us were done at the bar, she took me back home and i already knew Byron was going to be there. we talked and i cried (just like thanksgiving) and he left, miserable, to go to Shan's house. i don't know what happened after that, for i haven't talked to him yet since then. i swear, the next time i ever want to do something with either of them, i'll do it with one at a time. never again will i hang out with both of them at the same time. its so miserable and it always ends up like it did last night. ever since Shan broke it off with him, he's really starting to loose his mind over EVERYTHING. it sucks to be around him at all when he's like that because i know its not entirely his fault because of his shitty childhood. he actually didn't have one. and everytime i get caught in the fucking middle of one of these situations, i feel so bad because i know it's not his fault that he's like that! i wish i could do somehting for him, but i know i could never even get him to tell me everything that happened to him. he's so afraid that if he tells me anything that i'll use it against him and throw it back in his face or something. which is understandable. oh well. i gotta go.
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    barnesd66  40, Male, United Kingdom - 4,164 views
15
May 2018
11:17 AM IST
   

Conscious discipline and legal education

Conscious discipline and legal education
Discipline is the order, rules, statutes, systems, etc. that each social member should form under certain social conditions. No matter what activities people engage in, they must have a certain order and rules in order to be consistent. Otherwise, activities cannot be carried out.
Discipline is social, historic and class. Read more
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    ortizdayday76  39, Male, California, USA - 4,139 views
16
Jan 2007
1:32 PM EDT
   

my phone got stollen today and that really sucks because now i cant even look and find it because i know somebody has it at their house or somewhere i dont know.it pretty gay stuff.
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    charleyrojo  22, Female, Pennsylvania, USA - 4,111 views
07
Jul 2007
11:17 AM EDT
   

hi its me charley iwont be writing on here anymore i have a neww blog if u want to see it just go to http://charleyanaveragegirl101.blog.complease look at it and send a comment BY
1 comment(s) - 02:22 PM - 07/07/2007
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    dejack  61, Female, Michigan, USA - 4,107 views
25
Apr 2012
10:03 PM
   

Greatness

For me their are different kinds of greatness, so for me it depends on what you think greatness is, one people might think greatness is learning to read where as some else might think it isn't.
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    4d9rfan4life  52, Female, Arizona, USA - 4,053 views
02
Jul 2012
3:23 AM CST
   

Taking Control

The second date that Shawn and I had went pretty much as it did the first time, unfortunately, for a relationship sense in terms.� However the difference this time was that I went away with a clearer understanding of not only who he is and what I am capable of accepting on a personal level but that we truly can only be friends at this time in his life.

He's very much stuck in place with his personal life, not something worth finding fault in, but he's not ready to move on, that much is very clear and to continue pursuing something with him would only prove to be something that he would be pushed into, and that is not my style.

He was married for 16 years.� They have been apart for only 2.� He has a lot of marriage ghosts that either he doesn't know how to get past, or he is just not willing to move forward.� He also has a young son who seems to understand the divorce issue, but is very adament that neither of his parents can date or even talk to someone of the opposite sex.� That is another issue that Shawn needs to not only work through for himself, but he needs to help his son too.

At this time I have to stick to my guns and insist that any further contact be strictly in a friendship manner.� He is a great person, despite the issue's that we dealt with while I was there, I really enjoy our time together.�

He called me this afternoon while I was out and about stating that he wanted to talk about my decision.� By the time that I was able to actually call him back, he was unable to talk as his son was with him.� So tomorrow he is suppose to be calling me, what he has to say is completely unknown, but I will listen to what he has to say and go from there.
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Current Tags: Date, Friendship, Moving On, Relationship

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    kris89  30, Male, California, USA - 4,049 views
15
Jan 2007
1:38 PM PST
   

Im pisst off right now.... i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing i dont feel like writing
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    cadmanr44  39, Male, United Kingdom - 4,026 views
15
May 2018
11:24 AM IST
   

Art image is different from the image of real things in life

Art image is different from the image of real things in life
First of all. The artist can depict everything in reality that is inherent in its shape. You can also put on the image of the ideological feelings, imagination, fantasy, dreams, subconscious, etc. Give emotional form. The latter is commonly used in music, lyrics, psychological novels, freehand plays, and surrealist paintings. The subjective lens of the movie is when it comes to character delusion. This type of image is also displayed. The former can be called an external image. The latter can be called the inner image. Read more
Tags: education
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    cutieemuffin  29, Female, Ohio, USA - 4,023 views
27
Aug 2007
3:31 PM EDT
   

Well today was the first day of school and i thionk it went ok its just i dont wanna graduate cause i have no idea what i wanna do after and i no if i take a break im prolly not gunna go back.... i just dunno everythings just so confusing... and lately ive just been so stressed..... see we were helping a friend move and i just got paid so i had all this money and this guy stole it but hes like denying it so i just dunno we called the cops but wehat are they gunna do about it ya no... it just bothers me cause i really need the money i have to pay for my school when i decide what i wanna do and i was planing on helping my mom with my school clothes cause she dont have a job anymore and then all this shit happens..... o well i just dunno and im having a really hard time dealing with everything
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    Payton88  45, Male, Ohio, USA - 4,000 views
06
Aug 2008
4:12 AM EDT
   

Better for Now

It's been a little but since the last that I've written. Life is a lot easier right now. I guess that Christy and I are back together for now. I know that it's the wrong thing for me to still be with her, but I am so addicted to her. And yes a little in love too.

She wants to keep sleeping with other people, but be with me. That's going to be hard to get used too. I am always wondering who she is with when I am not around. It's not as bad as not being with her, but it's still pretty hard.

It's only a matter of time before she leaves again, so I had better have fun while I can.

2 comment(s) - 11:22 AM - 08/23/2008
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    Juicy Juice  30, Male, California, USA - 3,984 views
16
Feb 2007
5:38 AM PST
   

Welll i see that lots of people have introduced themselves to the world and i guess its only fair if i do tooo ........
My name is Hugo and i am 18 years old. I like to do many things, like play guitar, play video games, and i like to play baseball. I love to listen to music, my favorite band is Between The Buried and Me, and i listen to Rock... all sorts of rock .... thats about it.... my perferred type of music is Emocore, hardcore, and metalcore. i like to play war games ... or shooting games. i also like to take pictures ... not of myself ..but like a photography kinda thing....ummm i am very racial... not to be confused with racist .. cause im not racist ... but i critize stupid people .... not people who were born mentally challenged .. but people who were born normal and are just plain ignorant. im violent. im also not afraid of telling you how i really feel about you.... im sorry if you got offended by that.....ummm thats about all i have to say
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    LAWMAKER15  27, Female, Texas, USA - 3,964 views
20
Jul 2009
9:57 AM EDT
   

wow its almost been a year since i've even looked at this wondr if i even remember my password. any way i only have this one question. should you forgive your friends if they hurt you really bad by bringing out the really ugly about you???
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    RoXyGuRl2012  25, Female, Texas, USA - 3,946 views
14
Apr 2007
5:22 PM CST
   

hey yall
well yea my g-ma is not doing good &&she got to come home
but that dont mean she is doing
better.......but right now she is on hospice
&& we DO NOT knwo how long we have with her so
i was just wondering if yall could take a few
minutes of ur lyf&&pray for her && my
family!!!! well yea she is goign through tough
times and it is not goigng good so yea i would
just like id yall could pray for her......adn
if u only pray for her once than that is olkay
b/c 1 means alot !!!! well thanks for talking
ut imae and readint this well i hope yall have
a great day
LOVE ME
THANKSFOR YALLS HELP

ROXYGURL2012
1 comment(s) - 07:44 PM - 04/16/2007
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    emma  28, Female, Kansas, USA - 3,940 views
13
Dec 2006
6:08 AM EDT
   

hey bitches. i'm at school. just chillin in the writing lab. i'm high...ish. hella fucking cool going to school "high" you should try it. gotta go write a paper, even though i can barely see the screen.
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    ladybug20  33, Female, Canada - 3,936 views
04
Nov 2006
3:08 AM PST
   

busy, busy busy ... I moved to Richmond last weekend ...very stressful. But I no longer have to commute in rush hour ...THANKGOD! The further away from Chilliwack I get ...the better. But it's lonely out here ...not knowing anyone. Okay well I know a couple people, but im not out with friends every Friday and Saturday. Something im not used to. But I do feel better knowing that Jay has no clue where I live. Life is much better, but very different. Anyways im at work and I have lots to do ...apparently I have taken over Krissy's position as the everything woman so im running around like a chicken with my head cut off, lol!
1 comment(s) - 01:18 PM - 11/04/2006
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