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Re-using plastics.
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Mistress Rose



Joined: 21 Jul 2011
Posts: 8829

PostPosted: Mon Nov 17, 14 8:11 am    Post subject:  Reply with quote    

It's not just the sap Ty Gwyn. The current tantalising is pretty well just copper; in the past it had arsenic and chrome in it too, and worked a lot better but of course those are more toxic. We have had some fence posts that fail in about 3 years. We now try to use sweet chestnut when we can. Luckily a lot of that is grown round our way. That has a life of up to 25 years with no preservative.

Still not sure about the plastic posts. Would be interested to hear from anyone that has used them about their long term reliability.

Hairyloon



Joined: 20 Nov 2008
Posts: 14817
Location: Today I are mostly being in Yorkshire.
PostPosted: Mon Nov 17, 14 10:52 am    Post subject: Reply with quote    

Mistress Rose wrote:
It's not just the sap Ty Gwyn. The current tantalising is pretty well just copper; in the past it had arsenic and chrome in it too, and worked a lot better but of course those are more toxic.

True, but the toxins are pretty well contained in the wood, so that is only a problem if you are going to eat it.

gregotyn



Joined: 24 Jun 2010
Posts: 1423
Location: Llanfyllin area
PostPosted: Mon Nov 17, 14 3:42 pm    Post subject: Reply with quote    

There are snags with the fence posts; if the extruding machine is not operating at sufficient temp. to get some sort of physical bonding before they leave the machine they fall apart-spotted one at a road corner where the roadsign had broken, but suspect that is rare with good operators.

Mistress Rose



Joined: 21 Jul 2011
Posts: 8829

PostPosted: Tue Nov 18, 14 8:50 am    Post subject: Reply with quote    

Hairyloon, the sap stops the treatment penetrating, so can lead to poor preservation, not that the treatment comes out. Some must of course, and it was always recommended to wear gloves while handling tanallised wood, but it is dangerous for the operators treating the wood unless very strict precautions are taken.

gregotyn



Joined: 24 Jun 2010
Posts: 1423
Location: Llanfyllin area
PostPosted: Thu Nov 20, 14 3:22 pm    Post subject: Reply with quote    

I am not sure where the treatment harms the operator as one is supposed only to use tanalith in a pressure treatment plant and it should not be applied by hand and treated timber should only be handled with gloves. The treatment goes into the timber almost by default as the first part of the treament process in the cylinder is to vacumm the wood to remove as much sap as possible. There is a problem with spruce as its cell structure is different to other timbers.
After the vacumn process and evacuation of liquid, the plant fills with tanalith treatment solution at the correct dilution and is forced into the timber by pressure. You should only handle pressure treated timber when it has dried, indeed it should not be moved from the plant until it has dried. After I went on the course for treatment by tanilith at Rentokil, I realised that this was not for me as I worked for people who would not want to wait for the treatment to cure and the timber to dry first, I ran the sawmill instead and pleased to do so as what I suspected proved to be right. As I understand the situation it may have been possible to obtain tanilising chemicals 'under the counter' and subsequently do a bad job of treatment and with potential health risk.

Ty Gwyn



Joined: 22 Sep 2010
Posts: 3977
Location: Lampeter
PostPosted: Thu Nov 20, 14 7:02 pm    Post subject: Reply with quote    

As someone who has worked with timber David,you will know,

Spruce has a much more open structure compared to Larch,and tends to take in the Tanalising much better,Larch is more dense in structure and takes in less Tanalinth,

And by poor results in a lot of posts having a short lifespan,i`m sure Larch is the preferred timber for use by the treatment companies.

Hairyloon



Joined: 20 Nov 2008
Posts: 14817
Location: Today I are mostly being in Yorkshire.
PostPosted: Thu Nov 20, 14 7:36 pm    Post subject: Reply with quote    

Is larch not naturally durable?

Ty Gwyn



Joined: 22 Sep 2010
Posts: 3977
Location: Lampeter
PostPosted: Thu Nov 20, 14 8:15 pm    Post subject: Reply with quote    

Hairyloon wrote:
Is larch not naturally durable?


Only European Larch as far as i know,its rough bark stands out from the commercially grown more commonly Japanese Larch.

Mistress Rose



Joined: 21 Jul 2011
Posts: 8829

PostPosted: Fri Nov 21, 14 7:53 am    Post subject: Reply with quote    

I think larch has reasonable natural durability if it is really well seasoned by air drying, but otherwise, not much better than most softwoods.

David, I don't think your sawmills was the only one to try to rush the process. Chromium can give some very nasty ulcers, and of course arsenic is a known poison. We are being sold 'special' treated softwood posts now that are supposed to have a 10 year life with only copper treatment, but it sounds as if this 'special' treatment is what the tanallising was supposed to be in the first place. This leads me to suspect that most posts were just duncked in the treatment bath, seasoned or not, and didn't get fully impregnated, just coated.

As I said, we try to use chestnut now as it is naturally durable, and being in the south, there are plenty of them cut quite close to us.

Ty Gwyn



Joined: 22 Sep 2010
Posts: 3977
Location: Lampeter
PostPosted: Fri Nov 21, 14 11:06 am    Post subject: Reply with quote    

Chris,
What are the prices for these Chestnut stakes down your end?

As i noticed the other day there is somewhere fairly local to here now selling them.

gregotyn



Joined: 24 Jun 2010
Posts: 1423
Location: Llanfyllin area
PostPosted: Fri Nov 21, 14 4:37 pm    Post subject: Reply with quote    

It is true the spruce is more open than larch but the cell structure of the timber itself is less permeable than the cell structure of larch or douglas fir. The treatment will go into the spruce but a lot of it comes out and according to the "experts" at Rentokill thats why it rots sooner than larch. Tanilising is a mechanical process and dunking timber into a bath of chemical and water is not true tanilising, it relies on pressure and vacumn, for specific times, I would be surprised if you could buy a set up for less than 100k, but I'm not up on prices now been out of it for about 30 years. I am not so sure how just copper will kill all in timber, but is better I think than creosote from a health point of view! Presumably the copper is in the form of copper sulphate.
I would buy Larch posts over Spruce any day, John, for the above reason, but I'll make enquiries to make sure!

VM



Joined: 23 Nov 2007
Posts: 1745
Location: Lincolnshire
PostPosted: Fri Nov 21, 14 10:29 pm    Post subject: Reply with quote    

Just going back to plastics for a moment - and I know this is a company rather than home recycling, but nevertheless thought they are interesting:

http://www.solwayrecycling.co.uk/about-solway-recycling

Mistress Rose



Joined: 21 Jul 2011
Posts: 8829

PostPosted: Sat Nov 22, 14 7:19 am    Post subject: Reply with quote    

The prices one of our coppice group members gave in the spring are'
Round post 1 per ft.
Fencing stake 1/4 cleft 1.80

Haven't tried prices from our normal supplier recently, as we haven't been using many fencing stakes.

VM, Solway really have the recycled plastic market covered don't they. Don't know how long lasting the products are, and if they tend to warp or bend with age, but a good use for recycled plastic.

I was reading an article in Chemistry World yesterday about breaking down plastic and reusing the monomers. Not the sort of thing even you would do at home though Hairyloon.


Hairyloon



Joined: 20 Nov 2008
Posts: 14817
Location: Today I are mostly being in Yorkshire.
PostPosted: Sat Nov 22, 14 9:57 am    Post subject: Reply with quote    

Because it sounds daft, not because I cannot...

Mistress Rose



Joined: 21 Jul 2011
Posts: 8829

PostPosted: Sun Nov 23, 14 9:36 am    Post subject: Reply with quote    

It involves equipment that you couldn't have at home, hydrogen, and lots of specialist expertise. It is only financially viable if you are using the broken down chemicals as feedstock for higher value material. Definitely a future industrial process, not for Hairyloons back yards.

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