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  1. #21

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    Here is some information on plastics used for bottles. Of particular interest is the permeability values.

    HDPE Semi-rigid, translucent, very tough, very good chemical resistant
    to dilute acids, dilute alkalis and alcohols, moderate resistance to
    oils and greases, low water absorption, easily processed by most methods,
    low cost.
    LDPE Flexible, translucent/waxy, weatherproof, good low temperature
    toughness (to -60? C), easy to process by most methods, low cost, very
    good chemical resistance to dilute acids, dilute alkalis and alcohols,
    moderate resistance to oils and greases.
    PC Rigid, transparent, outstanding impact resistance (to -150? C) good
    weather resistance, dimensional stability, resistant to flame, good
    resistance to dilute acids and alcohols, very good resistance to oils
    and greases
    PC Rigid, transparent, outstanding impact resistance (to -150? C) good
    weather resistance, dimensional stability, resistant to flame, good
    resistance to dilute acids and alcohols, very good resistance to oils
    and greases
    PET Rigid, clear, extremely tough, good creep and fatigue resistance,
    wide range temperature resistance (-40 to 200? C), does not flow on
    heating, very good resistance to dilute acids, dilute alkalis, alcohols,
    oils and greases
    PVC Rigid or flexible, clear, durable, weatherproof, flame resistant,
    good impact strength, good electrical insulation properties, limited
    low temperature performance, very good resistance to dilute acids,
    dilute alkalis, good resistance to alcohols, oils and greases


    .................................................. .......O2 CO2
    ---------------------------------------------------------
    |EVOH |Ethylene vinyl alcohol copolymer | 2 | - |
    |HDPE |High density polyethylene | 2900 | 9100 |
    |LDPE |Low density polyethylene | 7900 | 42500 |
    |PC |Polycarbonate | 4700 | 17000 |
    |PET |Polyethylene terphthalate | 95 | 240 |
    |PVC |Polyvinyl chloride | 120 | 500 |
    ---------------------------------------------------------
    values are for 1 mil thickness, units cm3/m2.24h.atm
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  2. #22

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    OK, but what do they mean in practical sense? If HDPE has a value of 2900 for O2, it passes 2900 cm^2/m^2.... Does that mean death to developers or is that an acceptable value? I have been storing mine in HDPE bottles and it is fine for all practical sense for over 6 months period. (so for my purpose, it's perfectly fine....)

    For comparison purpose, do you have such data for Polypropylene which I did notice some color change.
    Develop, stop, fix.... wait.... where's my film?

  3. #23
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    Just to clarify -- most of the bottles I see that start with PET end with an "E" -- so they are PETE bottles. May I assume that the general characteristics attributed to PET apply to the subset of PETE bottles?

  4. #24
    AgX
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    PET and PETE mean the same.

  5. #25
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    Glass is the best. Started with glass, used plastic, now back to glass.
    Items for sale or trade at www.Camera35.com

  6. #26

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    Quote Originally Posted by tkamiya View Post
    OK, but what do they mean in practical sense? If HDPE has a value of 2900 for O2, it passes 2900 cm^2/m^2.... Does that mean death to developers or is that an acceptable value? I have been storing mine in HDPE bottles and it is fine for all practical sense for over 6 months period. (so for my purpose, it's perfectly fine....)

    For comparison purpose, do you have such data for Polypropylene which I did notice some color change.
    For our purposes what is important is the ratio of any two values in the above table not their absolute values. Thus PET is approximately 30 times more efficient at blocking oxygen as is HDPE.

    Polypropylene should be similar to polyethylene, maybe a bit better.
    Last edited by Gerald C Koch; 03-20-2013 at 08:45 AM. Click to view previous post history.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  7. #27
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    It's true that we might be splitting hairs here. Better is the enemy of good enough. If manufacturers anticipate that their products will be consumed relatively quickly, the difference in permeability between HDPE and PETE is probably not as important as other production factors.

    I'm still interested in what you folks have to say about light sensitivity of developers, though. All of the liquid concentrate developers I've used came in non-brown bottles. I think Kodak did use silver plastic bottles years ago, but now they seem to use ordinary (natural) translucent HDPE. So, I'm still curious as to whether there is really any substance behind the recommendation to keep developers in brown bottles.

  8. #28

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    Quote Originally Posted by Ian Grant View Post
    Packaging regulations as some chemistry is hazardous. If you look at household bleaches etc they aren't in PET either nor are any otherhazardous liquids.

    PET bottles aren't safe and I've had them break down in about 18 months maybe 2 years, in an accident they are far more likely to split/break.

    Ian
    Then why Rollei chemistry is packed in PET bottles?

  9. #29
    AgX
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    Quote Originally Posted by AgX View Post
    I have a lot of usage of 2L PET single-use bottles filled with water whilst hiking. They often fell about a 1.5m in various states of filling and never broke. There were kinks in the worst case.
    What I repeatedly encountered though has been the caps breaking. Just so, not by falling.

    The caps are from PE or PP and tear at the corner between the top and the threaded part where the rim of the bottle hits the top of the cap. Most probably due to excessive force.
    I have found caps with varying thicknesses at this part.
    Last edited by AgX; 03-20-2013 at 01:33 PM. Click to view previous post history.

  10. #30
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    Also, for some developers, it simply doesn't matter. Rodinal is packed in HDPE and it gets plenty brown in the container...likely oxidizing yet it works great. I'm sure when chemical manufacturers are looking at their bottle choice they consider compatibility (O2 ingress, chemical compatibility) vs shelf life. If HDPE works and they are looking for a 2 year shelf life, they'll use the HDPE and save a dime a bottle.
    Your first 10,000 pictures are the worst - HCB

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