Recycled plastic melted to form hulls?

Discussion in 'Materials' started by chowdan, Jan 16, 2015.

  1. gonzo
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    gonzo Senior Member

    Spain does not regulate CE.
     
  2. SukiSolo
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    SukiSolo Senior Member

    Correct, there are layer systems. I was part of a small team that designed some speaker cabinets using this technology circa 1996 which used a solid outer and foamed inner layer. The larger roto moulded hulls like say the Bahia are a 3 layer system, solid outer, foamed inner, thin inside skin sealing the foamed layer. Effectively it gives a lighter and stiffer structure. Big problem is shrink tolerances so you need a cooling jig to hold the hull(s) to maintain reasonable size match.

    Note that both PP and PE are lighter than water and the foaming creates air cavities so this construction has permanent buoyancy inherently. You will also note the hulls tend to be pale grey as they would become very soft in the sun if black.....;)
     
  3. gonzo
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    gonzo Senior Member

    I've seen them light beige too. Some early boats where white, but look grimy really fast.
     
  4. TANSL
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    TANSL Senior Member

    You're right, I have no objection to admit.
    No country "regulates CE" (do not know what you really mean). There are a number of international conventions and regulations and the country that wants adheres to them. No countries that create international standards. But if a boat wants to get the CE mark in Europe, must meet a certain standards, such as ISO. These standards define a number of materials and recycled plastics are not among them. I guess, to use, you have to prove that the mechanical properties obtained with them are suitable for the intended use.
    The Spanish government, through some companies concerted for such work, check that boat comply with all applicable standards. Even for workboats, it is unlikely that the Spanish government approved a hull made by the mat projection method. That's what you get.
     
  5. Skyak
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    Skyak Senior Member

    My previous employer did a substantial amount of recycling of plastics into usable engineering products. They didn't bother with post consumer because of contamination issues. The vast majority was nylon 66 from carpet scrap and most output was grey or black.

    The big problem with recycling plastics is keeping out contamination. Even the right plastic bottle becomes contaminant if it sat in the suns UV for too long. Most packaging going to landfills is low molecular weight dirt cheap plastic. The alternative feedstock natural gas liquids is so cheap they don't even bother separating it from natural gas if they can avoid it -and that's not saying much with natural gas well under 3$. Note all market info based on US prices, likely the lowest in the industrial economies.

    So it's a nice idea to recycle but not economically attractive.
     
  6. chowdan
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    chowdan 1980 PAC41 Liveaboard

    Wow thank you everyone for the responses!

    I have learned a great deal just from this alone!

    The primary thing is that we are a in a "garbage" filled world that does not take into account long term things.

    I'm surprised plastic becomes contaminated after sitting in the sun due to UV exposure....Would have never guessed this.
     
  7. JRD
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    JRD Senior Member

    I think its more that the UV destroys the mechanical properties of the individual item. So when it is used it is effectively a contaminant that reduces the quality of the batch if the % is high enough.
     
  8. Skyak
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    Skyak Senior Member

    UV breaks the molecule chains down. The smaller the molecule, the lower the mechanical strength. Plastic is like spaghetti microscopically. Melt properties also depend on molecule size so some small ones can mess up molding processes.

    The UV comment was more of a fun fact, the economics are the deciding factor. I agree that a more sustainable cycle is desirable, the question is who will pay and for what? I have seen some development of 'green' composites based on plants not petrochemicals -not cheap and not impressive mechanically. In the big picture recycled post consumer material is better for the environment but it does not seem to have the market appeal. It's hard to get to 'premium' from trash. On the other hand there may be an opportunity today with crowd funding. Not everything needs to make a profit. Some things are done just because they should be done. Producing high quality material from recycling for 3D printing would be a big hit.

    repeat -all economics based on US prices - the lowest of the major manufacturing nations.

    On a related note, did you know they used to make canoes out of paper? Another recycling opportunity.
     

  9. Zedwardson
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    Zedwardson Junior Member

    The real source of income for recycling is not in the products it makes, but the fact that people pay you take the plastic away for less then it takes to put into a landfill.
     
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