• Blog Stats

    • 77,682 hits
  • Archives

  • Enter your email address to subscribe to this blog and receive notifications of new posts by email.

    Join 157 other followers

  • Copyright notice

    This blog entry and all other text on this blog is copyrighted, you are free to read it, discuss it with friends, co-workers and anyone else who will pay attention.

    If you want to cite this blog article or quote from it in a not for profit website or blog then please feel free to do so as long as you provide a link back to this blog article.

    If as a school teacher or university teacher you wish to use content from my blog for the education of students then you may do so as long as the teaching materials produced from my blogged writings are not distributed for profit to others. Also at University level I ask that you provide a link to my blog to the students.

    If you want to quote from this blog in an academic paper published in an academic journal then please contact me before you submit your paper to enable us to discuss the matter.

    If you wish to reuse my text in a way where you will be making a profit (however small) please contact me before you do so, and we can discuss the licensing of the content.

    If you want to contact me then please do so by e-mailing me at Chalmers University of Technology, I am quite easy to find there as I am the only person with the surname “foreman” working at Chalmers. An alternative method of contacting me is to leave a comment on a blog article. If you do not know which one to comment on then just pick one at random, please include your email in the comment so I can contact you.

First lie wins

Dear Reader,

I want to write to you and tell you about a problem, this is a cognitive problem (thinking problem) which many people have. It is that they have a bias in favor of things which they already believe. As a scientist I battle to be the best I can and part of this battle is against the worst aspects of myself. I have to admit that scientists can and do suffer from cognitive biases, I try to work and think in such a way that these biases are suppressed.

I have seen reports which suggest that a polyethene product may have had a key role in spreading the fire so I think it is a good idea I write something about polyethene and fires.  I accept that the important fuel might have been polyethene rather than polyurethane. Maybe for all I know both were present in the cladding.

In the aftermarth of the Grenfell fire polyurethane was mentioned in news reports,  but it now appears that polyethene played an important part in the event. What I have written about polyurethane will stay on the blog, I do not think it is worthless. It might explain to someone something about how polyurethanes degrade and burn.

Now as we suspect that polyethene was a key fuel I want to discuss some polyethene issues, if we confine ourselves to high density polyethene (HDPE) then it is quite a simple molecule. It is simple strings of CH2 units. Here are five polymer chains.

polyethene chains

if we randomly break the chains by heating the polymer in the intense heat of a fire then we can degrade the chains. Now we will have

degraded polyethene

We have a C4, two C6, a C7, a C8, a C10, a C11, three C13, a C16, a C17, a C19, two C21 and a a C22 chain. All of these chains will be much more able to burn than the polyethene. However if we were to use irradated polyethene which is crosslinked then the situation is more rosy. I added some random crosslinks and now we would get the following

crosslinked degraded polyethene

Now we would get a C4, a C6, a C7, a C11, a C13 chain and a lot of crosslinked materials which is much harder to burn. Thus the fire would not burn with the same ease. The cross linking would tend to reduce the supply of fuel to the fire. The plastics fire is fueled by volatile gases which are formed by the thermal breakdown of the plastic, as the fire creates heat this would make it harder to get a self supporting chemical reaction (fire).

There are several methods of cross linking polythene, one method is to use an electron beam irradiation machine. I hope to get a chance to write something about such machines another day.

The problem with the “first lie wins” bias is that it stops people considering new evidence correctly, it also can make people want to defend their pet idea with great vigor. I hope to also have the chance to write more about this as well.

Advertisements

Social Care after the Grenfell Fire

Dear Reader,

It has come to my attention that a claim has been made that people who survived the Grenfell fire are being forced to live under very difficult conditions, as I like to think I am a good scientist I then looked for other reports (from other news outlets) regarding the treatment of the people who survived the fire. I think found this report in a newspaper which suggests that the state has failed to look after these people. While the two reports are not saying totally the same thing, the content of the two do not contradict each other.

The problem I see is that people who are already poor have had to flee with all their ID papers, keys and wallets left behind in the burning building. Surely something should be done to look after their dietary and other needs in the days after this fire debacle. I also have ask how on earth can anyone cope with only £10 a day in London if they have not been able to prepare to have to dash out of their home and not come back.

Regardless of what you think of the Chef Jamie Oliver has did make a kind offer of food and drink to the people. It is interesting that even the right wing “newspaper” (The Daily Mail) has been critical of the response.

I note that during the Vietnam war that when a US airliner (packed with US military personnel) ended up having to make a landing in the Soviet Union that the Soviets did provide them with food, drink and even cigarettes. I hold the view that if the Soviets would do that for a bunch of capitalists during the height of the cold war then surely the UK goverment can do better for the Grenfell residents.

The issue of the cladding has become even more “interesting”, interesting in a rather bad way, with a claim that the cladding was not legal for use for the purpose which it was used for. I am unable to assign blame here as my blog is not a court of law, but this claim if it is true could set the stage for a rather important court case.

More about polyurethane and the Grenfell Tower

Dear Reader,

Regarding the horrible fire in London at the Grenfell Tower, some questions are being quite rightly asked about the safety of using polyurethane foam in the gap between the building and the weather resistant cladding. My first thought was “why not use fibre glass in the gap” as it is a good thermal insulator and it is impossible to ignite (unless one uses chlorine trifluoride).

I saw an interesting comment that polyisocyanate foam would have been safer. This made me consider what is a “polyisocyanate foam”. Before we start it is important to understand what a polyurethane is, it is normally a great big long chain molecule formed by the reaction of a di-isocyanate with a long molecule which has an alcohol at both ends. It is impossible to draw a single structure for polyurethane as many different combinations of diisocyanates and di alcohols exist.

Here is one example of a polyurethane synthesis, I have used polyethylene glycol and bis(4-isocyanatophenyl)methane.

polyurethane synthesis

It has been known for some time that aryl isocyanates oligomerise when exposed to phosphines. A common method of making a polyisocyanurate resin is to take a typical diisocyanate and react it with its self using a catalyst to form a triisocyanate which has a central isocyanurate core. Sorry is this seems like a series of tongue twisters.

resin synthesis

What happens next is that the 1,3,5-tris(4-(4-isocyanatobenzyl)phenyl)-1,3,5-triazinane-2,4,6-trione is reacted with a diol to form a special type of polyurethane. While it is not perfectly noncombustable the hybrid polyurethane isocyanurates are harder to burn than the polyurethanes.

 

Grenfell Fire

Dear Reader,

It has come to my attention that a serious and rather horrible fire occurred recently in an apartment block in London. One of the important questions which need to be asked is “why did the fire spread so fast through the building ?”. A key part of the fire safety case for high rise apartment buildings is that the building is divided into a series of small fire cells. The idea being that a fire in one flat should not be able to spread to another flat or even worse another floor.

The idea is that if the fire can be contained for a long time within one flat that fire fighters will have time to bring it under control while the other people in the block stay inside their own flats. Here in the Grenfell Tower this fire cell idea clearly failed.

It has been suggested that the cladding added to the outside of the building did contribute to the spread of fire, Mike Penning (MP and former fire fighter) has been reported as having commented that the “cladding and windows (were) clearly burning” and that “I have never seen a tower block fire move so fast in that sort of way”.

The Sun newspaper reported that the tower was fitted with a cladding which includes polyurethane, if this is true then I have to ask the question of “why was polyurethane used instead of a noncombustible substance such as fibre glass ?”. I live in a wooden house in Sweden, I have had some building work done on my house recently. I also have to ask “how flame retardant was that grade of polyurethane ?”.

The new walls of my house have a layer of fibre glass in them for the thermal insulation. In my lab at Chalmers I have sometimes accidentally exposed glass wool (fiberglass) to a butane torch while heating glassware using the flame. When glass wool is exposed to this flame it melts slightly but as expected (being glass) it never ignites.

I hope to be able to write something soon which will explain the chemistry of what happens when polyurethanes and polystyrene are heated up in a fire. The key thing to keep in mind is that plastic does not normally burn. It might be a rather challenging statement, but almost no plastics will burn. What happens is that the heat of a fire normally converts plastics into flammable gases and other volatiles, this is a process known as pyrolysis. The pyrolysis products from the plastic then react with the oxygen from the air to burn thus making heat.

One of the key methods for preventing or slowing a fire fueled by plastic pyrolysis products is to slow the rate at which the plastic can emit combustable gases, one method I have seen in the plastic for electrical cables is to use cross linked polyethene. If polyethene (polyethylene) is crosslinked with radiation or a chemical treatment then it is much harder for it to generate pyrolysis gases. I have exposed polyethene to radiation and it does change the properties of the material. Sadly my trusty copy of A.J. Swallow’s book on organic radiation chemistry is out of my reach right now (I am typing on the train).

Another option is to include flame retardant chemicals such as brominated additives and antimony oxide, these substances do get a rather bad press. The problem is that there are some brominated flame retardants such as polybromobiphenyls which are clearly very harmful to human and animal health. But there are plenty of brominated additives such as polubromophenyl ethane and brominated polystyrene which are less harmful. One of the problems is that some elements within the green movement want to ban these substances, the fact that some bromine compounds are bad is not a good argument that all bromine compounds are harmful.

The problem is that it is possible to find harmful substances made from any elements, this is not a good excuse for banning all compounds containing an element. Lets consider a human analogy, “Jack the Ripper” was a human, “Jack the Ripper” was very evil and should have been arrested and locked up to prevent further serious crimes. But this is not a justification for locking up all humans to prevent crime.

What happens when brominated plastic is heated is that hydrogen bromide is released into the fire, this alters the flame chemistry. The hydrogen bromide reacts with some of the free radicals in the flame in such a way that it terminates the free radical chain reaction which occurs in the flame. By adding the antimony oxide this effect is greatly improved, the antimony oxide reacts in the hot plastic with the hydrogen bromide to form water and antimony tribromide. The antimony(III) bromide then has an even stronger fire inhibiting effect than the hydrogen bromide.

DUP views

Dear Reader,

It has come to my attention that Mrs May has been talking about the DUP and the Tories making an alliance. Like many people who do not live in Northern Ireland I did not know much about the DUP so I took a look online and asked my legal advisor about them. I found out a list of things which senior members of the DUP have been accused of having said. Newspaper reports support these claims which have been made about their statements. When I searched on line for evidence to support some of their claims, I very quickly found newspaper articles supporting the claims made by others.

  1. Abortion should be “ruled out for rape victims”
  2. The Pope is the Anti-Christ
  3. Gay couples “more likely to abuse children
  4. Homosexuality is an abomination
  5. No gay marriage (also see this)
  6. Gays more vile than child abusers
  7. Attempts to reduce CO2 emissions are “Green propaganda
  8. Man-made climate change is a con
  9. Creationism should be “taught in every school”
  10. The 60 million-year-old Giant’s Causeway is only 6,000 years old
  11. Line dancing is “sinful”

As a scientist I can not deal with many of the points, but 7, 8 and 10 are ones which I can deal with. If we consider 10 then we can address this point using radioactivity calculations. If we examine zircon (zirconium silicate) crystals from rocks we can estimate their age.

Zirconium silicate is a mineral which strongly rejects lead when it forms, so it will be lead free when it forms. Before we start we can look at what is in the unit cell of zircon. The unit cell is an important but tiny building block of a solid. I obtained the cif file from here. The unit cell is tetragonal, it is cube which has been compressed in one direction. Thus it is a box which is 6.607 by 6.607 by 5.982 Å. One Å is 0.1 nanometers. Here is a picture of what is in the cell.

zircon cell balls and sticks

The silicon atoms are yellow, the green ones are zirconium while the red-orange ones are oxygens. When the zircon crystals form the lead content is zero as lead does not incorporate into them but thorium and uranium can incorporate into the crystals.

At the start the lead content of the zircon is zero, as the uranium undergoes radioactive decay lead is formed. Using a simple equation it is possible to work out the age of the rocks by comparing the amount of uranium and lead in them.

For uranium we use

NU = NUo e t

and for lead we use

NPb = NUo (1 – e t)

Now armed with these equations we can work out how the uranium to lead ratio will change as a function of time.

While I do not have data for the Gaint’s causeway, I do have data for south east Ireland, I doubt if the rocks there will be very different to the rocks in Northern Ireland. Here the 206Pb:238U ratio was about 0.07:1.00. The 238U decays into 206Pb via 226Ra. Thus 0.935 of the original 238U is left in the zircon crystals. I got the data from “Select Intra-Ordovician deformation in southeast Ireland: evidence from the geological setting, geochemical affinities and U—Pb zircon age of the Croghan Kinshelagh granite. Intra-Ordovician deformation in southeast Ireland: evidence from the geological setting, geochemical affinities and U—Pb zircon age of the Croghan Kinshelagh granite V.” Gallagher, P. J. O’Connor, M. Aftalion. Geologcal Magazine, 1994, volume 131, issue 5, pages 669-684. DOI: https://doi.org/10.1017/S0016756800012450.

The half life of 238U is 4.468×109 years, thus the decay constant for this nuclide is 1.551 x 10-10 years-1. Now we have to rearrange the formula for the fraction of the uranium atoms which are undecayed.

NU = NUo e t

Now

NU / NUo = e t

-ln (NU / NUo) = λt

-ln (NU / NUo) / λ = t

Now

-ln(0.935) / λ = 0,06720874969345005314173683498865 / 1,551 x 10-10 years-1 = 433.325 x 106 years.

So we have a age for a rock formed by a volcano in Ireland which is about 433 million years old. Now while the person from the DUP have made a comment about rocks in Northern Ireland I am sure that rocks from the Republic of Ireland of a similar type will have a similar age. Now I hope that you can understand that the rocks of both the Republic of Ireland and Northern Ireland are much older than 6000 years.

I also have to ask the question of does it matter to a religious person if the earth is older than 6000 years. I know that Bishop James Ussher estimated that creation occurred in 4004 BC, but how much does it matter. I also have to ask “Is an all powerful God any less able to help the humans sort out their lives if they were descended from monkeys and other lifeforms ?”

I know that many people hold the view that “science has replaced religion”. I would strongly disagree with this statement. Science and religion normally deal with different questions.

In the same way that I think that it would be ridiculous and ill advised to attempt to prove (or disprove) the existence of god by means of a science experiment, I think it would be the height of folly to attempt to solve a chemistry, physics or biology problem by reading the bible. I know some chemists who are deeply religious, for their their faith and their science are able to coexist in their minds.

London attacks

Dear Reader,

It has come to my attention that a group of men drove a white van into people last night at 10 pm UK time (11 pm Europe time) and then carried out a knife attack. I will not attempt to try to compete with the news outlets such as the BBC, the reason is that Dr Foreman does not have a large team of people writing and looking around for information.

I am deeply troubled and unhappy that a group of people should choose to commit such an outrage. I have to ask the question of how can a person make the whole world convert to a religion if they murder everyone who does not practice their religion ? I imagine that the world would become a very empty place if this was taken to its perverse conclusion. I know that people differ in their views and opinions, normally I think that a better way to get the world to agree with you is to persuade people using facts and good arguments for why they should agree with you rather than attempting to change opinion by violence and threats.

What I find interesting and disturbing is that Donald Trump has been reported to have called for a travel ban as a response to the event. I have to question the wisdom of such a ban, Trump wants to restrict travel from 6 countries which are mainly muslim for “national security” reasons. I have to ask if such a travel ban would do any good as terrorists often are willing to break the law and travel using false papers.

Equally troubling I have discovered that some people in the UK are calling for the election to be canceled. One Mark Oxley has been reported by the Daily Mail to have started a petition with the words “to call off the general election for the foreseeable future”. I think that it would be wrong to cancel the election for a series of reasons.

  1. While the event in London is deeply offensive and an attack on British society it is not a sufficient threat to require that democracy be suspended. The IRA bombing and shootings in the past did not make the UK give up democracy, so why should we now give up on it !
  2. Aborting the election would give the terrorists a great victory, they would know in future that by means of violence they can make the British give up on democracy.
  3. The police, security services and the military may be needed to prevent or to mitigate terrorism, the operation of these three things will not (and can not) be changed quickly on a day to day basis by the goverment in Whitehall.

I would suggest that the UK should go ahead with the election later this coming week.

Karlstad fire

Dear Reader,

It has come to my attention that a large fire occured this afternoon in Karlstad in Sweden, this fire occured in an industrial site on saturday afternoon. In some ways this is the best time / place to have a fire as fewest people will be close to the blaze.

When I find out more about the fire I will post more about it.

%d bloggers like this: