Talk:Polyethylene terephthalate

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[edit] Chemical structure you show is incorrect

sorry, but the chemical structure shown for PET is incorrect. An oxygen is missing, it can be placed at either end of the chain, but as drawn, the structure shown is incorrect.

Thanks for catching that! I'm a little embarrassed I didn't see it myself. It's now been fixed.
Just so you know, the images are open to editing, just as the text is: you can click on the picture to go to its description page, and from there you can download the file, edit it, and use the "upload a new version of this file" link to publish your changes. But I know that some folks are less comfortable with Microsoft Paint than others.--Joel 18:13, 29 July 2005 (UTC)


I heard that reusing water bottle makes from PET would be harmful as cancer causing material from the bottle would desolve into the water it contains eventually cause human health. One report said a 12 year old died because of it. I wonder if it would be possible?

Lee from Toronto

Here in Taiwan (actually even HK), several news media and government health agency are already denied this rumor.

Detail information, please see below link: Report from Swiss Federal Laboratories for Materials Testing and Research

Jesse from Taiwan

A single molecule of PET is an arrangment of Oxygen, Hydrogen and Carbon molecules around what is called a Benzene ring. Benzene is known to cause anemia and leukemia. However, Benzene exists in MUCH higher quantity's in items we handle everyday than it does in PET. PET is a very safe plastic and you have nothing to worry about. The FDA here in the U.S. monitors all of these things very carfully and has deemed the material safe for storing items meant for human consumption.

Brian P Spence

I second these comments. The funky chemical taste that appears after some use comes from polyvinyl alcohol, which is nontoxic. The danger I believe in is from bacteria, because few people wash their water bottles or realize how much food gets into a bottle due to backwash. But this is a mild danger, which can be avoided by treating the bottles like other types of dishware. One thing to note: news outlets, PET manufacturers, bottle manufacturers (both Alcoa-type companies and Nalgene and its imitators), and bottled water companies all benefit if people believe that the reuse of disposable bottles can kill their children. Which shareholders would benefit from debunking this belief?--Joel 05:34, 16 Jun 2005 (UTC)

[edit] Greetings

Greetings... I heard that PET production (i mean mass production) have two diffrent process which are esterification and polimerization. They do have certain characteristics that they monitor and one of them are COOH number (during esterification process) could you explain it in the article as well. Thank you.

Syamshul

[edit] Amorphous PET

Just wanted some idea on amorphous PET and how it is different from PET in terms of applicatoions

Ankit

[edit] Below?

It says "See copolymers, below", but there's nothing below that on copolymers...

I believe that was from before a re-organization of the article. I've changed it to "above"...the link to the section was the intended mode of navigation, and thankfully, it still works. --Joel 21:42, 20 January 2006 (UTC)

[edit] Di(2-ethylhexyl) adipate original research moved to talk

Much of the following discussion sounds like original reasearch to me. Moved here for discussion. ChemGardener 13:35, 27 February 2006 (UTC)

[edit] Potential hazards in food contact applications

According to the "Non-Toxic Times", April 2004 published by Seventh Generation, Inc. PETE has been shown to leach Di(2-Ethylhexyl) adipate (CAS Number: 103-23-1) into water. Di(2-Ethylhexyl) adipate AKA Bis(2-ethylhexyl) adipate has been found to leach from drinking water bottles made from PETE particularly after bottles have been squeezed, scratched or washed with hot water. Deena Lilya was a graduate student at the University of Idaho when she did this research. Di(2-Ethylhexyl) adipate is a suspected human carcinogen. http://www.seventhgeneration.com/site/apps/s/content.asp?c=coIHKTMHF&b=133099&ct=97028#3 http://www.findarticles.com/p/articles/mi_m1041/is_8_81/ai_105163668


[edit] No hazards in food contact applications demonstrated

Di(2-Ethylhexyl)adipate (DEHA) is neither inherent in PET as a raw material, nor a byproduct or decomposition product of PET. DEHA is a common plasticizer that is used in many plastic items but not in PET. Furthermore, the Swiss Federal Laboratories for Materials Testing and Research in their study (June 2003) on "Migration of organic components from polyethylene terephthalate (PET) bottles to water", carried out on new and reused plastic water bottles, did not find DEHA at concentrations significantly above the background levels detected in distilled water, indicating DEHA is unlikely to have migrated from the bottles. The study concluded that the levels of DEHA are distinctly below the World Health Organization guidelines for safe drinking water.


http://www.sodis.ch/files/Report_EMPA.pdf http://www.plasticsinfo.org/beveragebottles/apc_faqs.html

According to the report the bottles tested in the Sodis "Report_EMPA.pdf" above orginated from the countries of Honduras, Nepal and Switzerland. When Deena Lilya investigated PET bottle leachates she was a graduate student at the University of Idaho it may be reasonable to presume the bottles tested were from North America.

According to a google ad for www.specialchem4polymers.com there are 9 500 additives available for polymers. The precise processes and formulas for manufacturing plastic products including food contact PET are often considered trade secrets and as such may be protected from disclosure by US law. <==! Considering this situation it is hard to see how a well grounded claim could be made that DHEA which "is a common plasticizer that is used in many plastic items" is "not in PET".==>

DEHA is unlikely to be intentionally added to PET mineral water bottles and furthermore would not ordinarily be expected to be present. In addition with regard to the toxicity and hazards of DEHA it is not classified as having any health hazards according to European Directives.

Food contact articles made of plastics are regulated in both Europe and the US. In Europe food contact articles are regulated by what is known as the 'plastics directive'. This lists those monomers and additives that are approved for use in any plastic food contact article. If a substance has been placed on this list then substantial toxicological data will have been reviewed by the European Food Safety Authority (EFSA).

Food contact articles must be tested to ensure that no constituents migrate from the article into foodstuff at a level greater than 60mg/kg or 10 mg/dm2. In addition some chemicals have specific migratory limits. These levels are set based on what EFSA deems acceptable levels for Human consumption, and are significantly lower than any levels of toxicological concern. DEHA is listed in the plastics directive with a migratory limit of 18mg/kg. This means that EFSA have reviewed toxicological data and deemed that it is safe to add to food contact articles providing that the level migrating from the article into the food stuff does not exceed this limit.

Those in the food contact packaging industry will regularly test for such migration for any additives and/or monomers used in PET packaging, and ensure all regulatory requirements are met. This applies not just to PET but any plastic article intended to contact food.

In the US, the FDA also regulates food contact articles. DEHA also has listing in the FDA's TITLE 21--FOOD AND DRUGS CHAPTER I--FOOD AND DRUG ADMINISTRATION DEPARTMENT OF HEALTH AND HUMAN SERVICES allowing its use as a plasticizer in polymeric substances that will contact food. Again to achieve such a listing, toxicological and migratory behaviour will have been reviewed.

Given the fact that food contact materials, including PET are regulated in this manner I think that consumers can be reassured that their use is safe


[edit] PET safety

Susten.biz 00:25, 1 March 2006 (UTC) Ken Huck, Asheville NC writing below. It would very be interesting to know more about potential sources of bias of the editors who apparently want to see polymer food contact safety issues excluded from this Wikipedia article. Perhaps they will say more about themselves on their users pages. I wonder how much of their income and family net worth may be derived from the PET industry or its related up and down chain industries. I estimate that less than US$100 of my net worth and US$10 of my annual income is.

I have an undergraduate degree in the history of science & technology. I have taken a college level course in polymer manufacturing engineering technology. I was also exposed to knowledge of the industry as a child and young adult due to my families previous involvement in the related field of injection molding.

I understand very well and value the methods of science and am committed to Wikipedia principals.

This is not an example of me citing my own unverifiable independent research Wikipedia:No_original_research I do not personally know any author cited or have a financial interest in 7th Generation. In the interest of full disclosue my user profile says something about me and it will say (or link to) more as time goes forward.

I will acknowledge being new to wikitext and not knowing how to make a comment that does not appear in the article. So I asked for help to improve a section and it was moved to a talk page. This section has three citations to reputable sources (see Wikipedia:No_original_research#What_counts_as_a_reputable_publication.3F compared with one as far as I could see for the entire rest of the article. In my view the removal of this well cited section is proximate to an act of vandalism that substantially degrades the academic quality of the article that the information was removed from. I invite other editors to restore it (with the comment tags fixed).

Also try to write in E-prime and so some times my prose may read differently I feel E-prime is a voice particulary suited to maintaining a neutral point of view. kwh Susten.biz 00:25, 1 March 2006 (UTC)

It would also be interesting to learn what financial interest Susten.biz might have in scare-mongering against plastics. From his comments on financial interest, it seems that he would like to preclude anyone who actually has KNOWLEDGE about PET from contributing to the article. From his description of himself, he apparently has no expertise in the area of PET or food contact safety whatsoever and is not even a scientist. Perhaps that is why he cannot distinguish between reputable publications and non-reputable ones.—Cynthia Bennett 18:25, 12 March 2006 (UTC)

[edit] Placeholder pointer in article removed -- PET hazards safety continued

I have asked user BenFrantzDale for a reconsideration or explanation of an apparent outside of policy revert at User_talk:BenFrantzDale The entry also includes an explanation of why I believe this is a Public interest and right to know issue.

Regardless of the position you take on this alleged original research on PET safety iniated by ChemGardener in moving the text out of the article please state in detail why or why not making reference to Wikipedia policy. Truth, transparency, trust. Susten.biz 15:53, 1 March 2006 (UTC)

Susten.biz, I don't doubt that there are potential safety issues with food exposed to polymers. I am not trying to cover anything up, and to the best of my knowledge none of my income comes from the polymer industry. Some of your references look plausible. I do question the tone of your section that ChemGardener moved to this talk page. Even if it isn't "original research", it reads like it. While it may be E-prime, it still is implicitly non-neutral point of view. For example, the opening sentence reads:
According to the "Non-Toxic Times", April 2004 published by Seventh Generation, Inc. PETE has been shown to leach Di(2-Ethylhexyl) adipate (CAS Number: 103-23-1) into water.
This wording implies that what "Non-Toxic Times" says is fact, which I would call PoV unless the fact in question is widely accepted (which does not appear to be the case). A NPoV intro to a "Food safety" section might better start "Some groups have raised questions regarding the safety of PET ...". Also, this excessive inline citing (probably a newbie mistake) comes across as an appeal to authority. Furthermore, Seventh Generation, Inc. is a special-interest group, so even if they are doing good for the world, their publications don't count as a "reputable publication". You do have some plausible sources. The American Plastics Council (plastics.org) is an industry group; if they raise safety concerns, I would find it fairly convincing.
In short, from what I've seen there is probably room for a safety section in this article, but if it is, in fact, a contentious issue, it should be treated as such, not as fact. I am not a polymer scientist, chemist, or health expert. Maybe someone else watching this page has more insider insight.
And again, welcome to Wikipedia. —BenFrantzDale 02:59, 7 March 2006 (UTC)
As someone who knows a bit about PET, but is not in the bottle industry, I might offer the following comment. It is highly unlikely that DEHA in bottled water—if indeed the analysis by the student were correct—would be coming from the PET. There is no reason in the world why anyone would want to add a plasticizer (DEHA or any other one) to the PET used in a bottle. It would 1) make it more expensive and 2) make the properties worse. PET is used in bottles primarily because of its excellent barrier properties, i.e. it keeps the fizz in and unwanted aromas out. The use of a plasticizer would counteract that. I am not familiar with the formulations that are commonly used in the caps for PET bottles, but there is the need to have some soft material there to get an adequate seal. So I cannot rule out that there might be some caps on PET bottles that contain a plasticizer. It is also possible that the student was picking up DEHA contamination from other materials in the lab. —Cynthia Bennett 18:23, 12 March 2006 (UTC)

[edit] Di(2-ethylhexyl)adipate Health Safety Concerns

I had moved the section reproduced below because of concerns about Original research. I've bolded the statements that appeared to be of concern. (The <== ==> section is also one I flagged; but, the bold doesn't seem to show up.) I thought moving the discussion here was appropriate to see if more NPOV and Verifiability could be achieved. My thoughts on the topic itself follow the moved section.

Start Moved Section------

[edit] Potential hazards in food contact applications

According to the "Non-Toxic Times", April 2004 published by Seventh Generation, Inc. PETE has been shown to leach Di(2-Ethylhexyl) adipate (CAS Number: 103-23-1) into water. Di(2-Ethylhexyl) adipate AKA Bis(2-ethylhexyl) adipate has been found to leach from drinking water bottles made from PETE particularly after bottles have been squeezed, scratched or washed with hot water. Deena Lilya was a graduate student at the University of Idaho when she did this research. Di(2-Ethylhexyl) adipate is a suspected human carcinogen. http://www.seventhgeneration.com/site/apps/s/content.asp?c=coIHKTMHF&b=133099&ct=97028#3 http://www.findarticles.com/p/articles/mi_m1041/is_8_81/ai_105163668


[edit] No hazards in food contact applications demonstrated

Di(2-Ethylhexyl)adipate (DEHA) is neither inherent in PET as a raw material, nor a byproduct or decomposition product of PET. DEHA is a common plasticizer that is used in many plastic items but not in PET. Furthermore, the Swiss Federal Laboratories for Materials Testing and Research in their study (June 2003) on "Migration of organic components from polyethylene terephthalate (PET) bottles to water", carried out on new and reused plastic water bottles, did not find DEHA at concentrations significantly above the background levels detected in distilled water, indicating DEHA is unlikely to have migrated from the bottles. The study concluded that the levels of DEHA are distinctly below the World Health Organization guidelines for safe drinking water.


http://www.sodis.ch/files/Report_EMPA.pdf http://www.plasticsinfo.org/beveragebottles/apc_faqs.html

According to the report the bottles tested in the Sodis "Report_EMPA.pdf" above orginated from the countries of Honduras, Nepal and Switzerland. When Deena Lilya investigated PET bottle leachates she was a graduate student at the University of Idaho it may be reasonable to presume the bottles tested were from North America.

According to a google ad for www.specialchem4polymers.com there are 9 500 additives available for polymers. The precise processes and formulas for manufacturing plastic products including food contact PET are often considered trade secrets and as such may be protected from disclosure by US law. <==! Considering this situation it is hard to see how a well grounded claim could be made that DHEA which "is a common plasticizer that is used in many plastic items" is "not in PET".==>

End Moved Section------

Verifiability - The only scientific publication appears to be the Swiss Federal Laboratories report. Do we have some direct references to Lilya Masters Thesis? An abstract she presented appears at: Society of Risk Analysis 2001 Meeting. However, it does not list the levels found. Does anyone know what they were? With the Swiss work indicating DEHA levels similar to background distilled water levels, it may be there is not much disagreement in the reports.

Suggested Content - Let me suggest the following as a trial balloon for this section of the article:

[edit] Health Concerns

A Masters Thesis reporting that di(2-ethylhexyl)adipate could be detected in water from PET drinking bottles Society of Risk Analysis 2001 Meeting lead to concerns about the use and reuse of such bottles. Subsequent work by the Swiss Federal Laboratories for Materials Testing and Research did not find levels at concentrations significantly above the background levels in distilled water Migration of organic components from polyethylene terephthalate (PET) bottles to water.


ChemGardener 17:58, 12 March 2006 (UTC)

[edit] Abbreviation

Obviously there are a number of variations of the abbreviation. Where is the proper place to use each? (PET, PETE, PETP,PET-P)

  • "PET" appears to be the industry abbreviation for Polyethlene (PE) Terephthalate (T)
  • "PETE" appears to be the North American Resin identification code for recycling. There must be a historical fact about why PETE was chosen over PET? What countries use PET?
  • "PETP" or "PET-P" appear to abbreviate Polyethylene Terephthalate Polyester, is this the proper abbreviation of the proper name?

When discussing the resin, what is the proper term to use?


I would recommend using the abbreviation "PET", as this term is used worldwide by all professionals dealing with polyethylene terephthalate. It is the official abbreviation according to an international ISO standard. (I don't know why the US uses the abbreviation "PETE" for identification in recycling operations. In the EU and in Japan, the marking for recycling is "PET".)

The abbreviation "PETP" (or its misspelling "PET-P") comes from the old German abbreviation, derived from Polyethylenterephthalat (=polyethylene terephthalate). This abbreviation was officially phased out in the mid 1980's, because it was felt that using a different abbreviation in German was confusing. However, old engineers in Germany still tend to use "PETP". Chemists don't anymore, as they are more familiar with chemical nomenclature. Incidentally, up until the 1970s, the German abbreviation was "PÄTP" because the Germans used to use Ä instead of E for the "ethyl" group. I haven't seen "PÄTP" written in current documents for some while now and I presume that the usage of "PETP" will finally die out in the next decade or so, as the old guard retires. Cynthia Bennett 17:22, 22 October 2006 (UTC)

I added PETG in the copolymers.

[edit] Uses

I realize the uses of something (like Dacron) are too numerous to mention all of them but in case you are looking to list another you could mention bowstrings (for archery.) There are other materials used to make bowstrings but dacron threads is one of them.

[edit] PET Processing

Hi to all. I have been researching on PET for a few days now and read all you wrote as comments as well. I don't know how this website works yet but I feel that if one will make a comment on a subject he or she should also include academical or experience background so that it could be taken as a general comment or technologist comment.

This is the first time I write in Wikipedia so let me first introduce myself. I am a double major in mechannical and electrical engineering with large experience in the sugar industry and thermochemical analysis, plant efficiency and equipment design and maintenance. Right now I am venturing in the plastic industry as Plant Supervisor Engineer in the largest plastic transformation plant in the Central American and Caribbean region.

I am more used to technical forums but I think I should give this a try. What I am looking for is to expand the contributions on the areas listed above and also on plastic processing, recycling, testing and process control, analysis and troubleshooting. Maybe this is not the idea of Wikipedia but at least on the comment section we could expand the content to a more indepth approach for those interested.

I do hope ethical values are also included when discussing a subject. For instance, about the PET resin as being toxic, no research that I have seen so far points on that direction, but I also have to say that as with many other products, PET has to be handled in a safely and "normal" way to keep it's "safe for humans" characteristic. The method for resin process that will be transformed into food & beverages containers meet NSF, ISO and FDA standards as well as ASTM. In our case, we are well certified.

Finally, I'd like to ask if anyone could starta thread on how to improve time cycle on a blow molding, injection or extrussion process. This should also include 2 stage PET transformation. —The preceding unsigned comment was added by Maescami (talk • contribs) .

Hello, Maescami, and welcome to Wikipedia! Please sign your comments with four tildes (~~~~). The place to describe your academic background and experience is your user page, User:Maescami. Go ahead and click that link and you can start writing it.
Please feel free to add whatever you want to this article, as long as you cite your sources. Don't worry too much about making mistakes; they will be quickly corrected. I myself know only the basics about polymer science, and I look forward to your expert contributions. —Keenan Pepper 22:03, 19 November 2006 (UTC)


[edit] Antimony discussion

I am reverting the section titled "antimony" to a previous version, which puts William Shotyk's results in a more realistic perspective. Here is the background:

In various public statements, Shotyk expresses "surprise" and apparent alarm that the very small amounts of antimony he has found in PET bottled water increase to somewhat higher amounts (though still tiny) as time passes. In fact, this is not surprising at all. Indeed, it would be very surprising if the laws of diffusion made a special exception for the case of PET bottles, which is apparently Shotyk's expectation. In his defense, I suppose we might note that he is a geochemist and thus has no expertise or experience in the fields of polymers and food contact safety. I wish he had taken the time to study the pertinant literature before publishing his results in a journal where the reviewers were bound to be similarly unfamiliar with the characteristics of plastics and food. And I find it particularly unfortunate that he is continuing to misrepresent the subject to reporters, who probably do not realize that geochemists such as he are probably not experts on food safety.

The migration of substances into and out of plastics for food packaging has been studied extensively. There are many publications in scientific literature by authors including O. Piringer, R. Franz, T. Begley, A. Feigenbaum, L. Castle and others. In one of the most frequently cited articles (abstract), the authors show that the rate (i.e. speed) of migration of a substance out of a monolayer plastic is proportional to the square root of the time elapsed at a given temperature. (It is slower if the substance has poor solubility in the food or food simulant, i.e. water in this case.)

So let's take Shotyk's example of 0.7 ppb (=700 ppt) antimony found in water bottled in PET 3 months earlier and use the square root time dependence to calculate future concentrations. For the sake of simplicity, let's assume that the initial concentration of antimony in the water was 0.000 ppb and that the migrating antimony species does not have a solubility limit in water. So, if it took 3 months to reach a concentration of 0.7 ppb, we'll reach a concentration of 1.4 ppb after 9 months (32 is 9). Similarly, it will take 6 years and 9 months to reach a concentration of 2.8 ppb. And the next step? We'll reach 5.6 ppb after 547 years. That's still only a little more than ⅛ of the specific migration limit for antimony in the EU, 40 ppb. I don't know about Mr. Shotyk, but I don't expect to be alive 500 years from now. I certainly won't be depending on 500 year-old bottled water! (Note that both of the assumptions we made could be wrong, but if they are, the antimony concentration would rise even more slowly than we calculated. Note also that the specific migration limit for antimony in the EU is based on the toxicological assessment by the World Health Organisation, employing adequate safety factors.)

Those at the Swiss government testing lab who did the first study on antimony in PET bottled waters understand the time dependence of migration. That is why they were checking bottles of various ages, up to the expiration date printed on the bottle. Shotyk's number results are merely an independant verification of their findings that there is no problem. There is simply no reason for concern.

A comprehensive discussion of migration of substances in and out of plastics and foods can be found in this book: O.G. Piringer, A.L. Baner (eds.), "Plastic Food Packaging Materials: Barrier Function, Mass Transport, Quality Assurance, Legislation", Wiley-VCH. (2000) (1st ed.) [1] A list of original scientific literature on the subject of food packaging and substance migration can be found here: list of articles

CindyB 15:21, 4 February 2007 (UTC) Edited for Wikipedia:Naming conventions (people)CindyB 23:17, 8 February 2007 (UTC)

This is not how Wikipedia works. We do not bowdlerize. Wikipedia reports faithfully what Dr Shotyk - not any Mr Shotyk - refers to in his statement. His team did a research; you are speculating and extrapolating. Your employment at a PET plastic company makes you a vested party, so your view is necessarily non-neutral. The fact that Dr Shotyk's research is independent and not industry-funded makes its representation here imperative. Your statement, that 'the Swiss government ...did the first study on antimony in PET bottled waters', is shocking. Doesn't the PET industry conduct tests on a potentially toxic substance?
Wikipedia does not coerce anyone into any beliefs, but people do come in to read about facts, and this is verifiable and a reference is cited. Please do not change or remove the section unless there are errors - and please indicate them - you want to correct. Mandel 12:44, 8 February 2007 (UTC)
Mandel, it is not bowdlerization to remove speculations, which don't belong in Wikipedia. May I point out that I reverted to a version that did cite William Shotyk's paper, and not to the more recent version by Jimbow123, in which the mention of Shotyk's work and antimony's toxicity at much higher concentrations had been removed. What should not be in the article is Shotyk's speculation that the concentration might rise to a harmful level during the normal shelf time of the product. If his speculation is right, then well-established basic principles (Fick's Law of Diffusion) don't hold for antimony in PET. But, since you apparently think I'm untrustworthy or "contaminated" and I think you don't understand pretty straightforward scientific arguments, why don't we let some "uncontaminated" person with a scientific background decide. So I'll leave the Shotyk's unproven speculation in, even though speculation has no place in a Wikipedia article. Somebody else should remove it, if he or she sees fit.
What I find shocking is your misintepretation of the phrase "first study". (I wonder if it might even be evidence of a strong non-NPOV on your part.) The study by the Swiss government lab is clearly the first one mentioned in the Wikipedia article and of the two studies mentioned in the article, it was the first one published. That in no way implies that companies don't check their own products. Why don't companies publish their own quality assurance data? That's because such publications are usually unlikely to be very useful as "advertisements". Imagine reading an ad that says, "We measured many, many things and everything was OK. Our competitors are OK too." What company would waste time and money publishing that?
You are right that it was incorrect to write "Mr. Shotyk". It is equally incorrect to write "Dr. William Shotyk" in a Wikipedia article. According to Wikipedia:Naming conventions (people), we should write "William Shotyk". This I shall indeed correct.
CindyB 23:17, 8 February 2007 (UTC)
Dr Shotyk's so-called speculation shows that antimony is leaching from PT plastic, at a pretty high rate. The toxic level of antimony for humans is arguable, but certainly in the parts-per-billion (ppb) range. Dr Shotyk does not misrepresent anything - his statement is carefully worded to show he might be overcautious, but caution here is a virtue, not vice. Your extrapolation assumes we only take one single bottle of PET water. One bottle might not kill you, many bottles, taken say after a marathon, could built to toxic levels. An exhausted runner could take in 3 or 4, even 5, bottles, bottled say a year ago, at one go. Note that PET is not used just in bottled water, but ubiquitously - for cooking oil containment, sauces, toothbrushes, pillow fillings - which could be used for many years - and bed covers. Have anyone measured how much antimony can leach from all these contacts?
My 'misintepretation' of your phrase is less 'shocking' considering the fact, a. I do not work in or for a PET plastic company; and b. my understanding is based entirely on your term 'first study', not 'first study quoted here'. Any carelessness is as much yours as mine. You cannot assume everyone prescience of mind; unless you word it properly. Mandel 16:32, 9 February 2007 (UTC)
Mandel, may I suggest that you calm down and actually read what I wrote?
What is wrong about William Shotyk's publication is not the measurements he reported—I think the measurements themselves are probably accurate—but his apparent suggestion that the time dependence of the increase might be linear. If one reports concentrations at two different times, laymen like you immediately infer that the concentration will keep increasing at the same speed. In fact, the increase will not be linear, but will slown down. Indeed, the rates of chemical processes are usually not linear.
Since you did not understand my previous attempt to explain this, let me try again without math. For any substance diffusing out of a solid, at first the speed is fast, and then it gets slower and slower as time goes on. In other words, first the molecules that were close to the surface of the solid come out. They are able to do so quickly because they do not have to travel far through the solid. As time goes on, the molecules coming out have had to travel further through the solid and that takes longer. The natural law governing this is Fick's Second Law of Diffusion.
For substances coming out of plastics, Fickian diffusion has been shown to be true for all cases studied (in those journal references I suspect you did not bother to look at; certainly you did not understand them). There is no reason to suspect that antimony might disobey the Fick's Second Law.
The upshot of the slowing of the rate is that we never get anywhere near the allowable concentration in water, not in one year, not in ten years and not in 500 years. I have no doubt that Shotyk will eventually discover how the increase is slowing, so the antimony concentration stays in the safe range, as he keeps measuring his samples over the next 2 or 3 years. I do wonder whether he will bother to publish his results when he gets to that point.
You are apparently also worried that no one is taking the complete exposure toward antimony into consideration. Taking such things into consideration is what public health authorities do when they set standards. Let me explain how toxicoligists and government agencies arrive at "allowable concentrations". First, they take data from all the studies and determine the no observable adverse effect level (NOAEL), which is the amount that you should be able to ingest daily all life long with no ill effect. Then they divide the NOAEL by a large safety factor (100 or 1000, depending on the factors involved with the data quality) and the result of that is called the "tolerable daily intake" (TDI) or sometimes also the "acceptable daily intake" (ADI). Then the toxicologists consider the various kinds of exposure possible (air, food, water, etc.) and set allowable concentration limits for each type of exposure based on that. So, the various kinds of exposure are taken into consideration and in addition there is a large safety factor. Having a large safety factor is important, for as you noted, if we err it should be on the side of caution.
So your marathon runner may keel over from heat exhaustion, but he won't from antimony, even if the bottles are a tad old.
Have a good day. CindyB 17:44, 10 February 2007 (UTC)

[edit] Redirect doesn't work

The word Terylene is linked on this page, but when you click on the link you are sent straight back here. And there's very little information about Terylene to look at. —The preceding unsigned comment was added by 81.19.57.146 (talk) 14:20, 7 March 2007 (UTC).


_____

How sad are you to argue on a chat about PET bottles i mean get a life!!!

[edit] Sombody list the matrials

Subscript text Sm1 list the matrails 4 a pet bottle please


click here aswell

[2]

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