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Durable materials, recycled materials

Home Forums Archive Structure Designs Durable materials, recycled materials

This topic contains 6 replies, has 5 voices, and was last updated by Profile photo of hombre hombre 4 years ago.

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    One of the key criteria for seasteads is durability. Ideally they should be able to last for several decades on the open ocean without visiting a drydock. Concrete is one material proposed for reasons of durability and cost. Metal structures eventually corrode, though modern ship steels and aluminums like 5086 have improved corrosion resistance, so they may last longer than older alloys.






    Although initially dubious, the durability of fiberglass ships has been proven. When the first fiberglass sailboats were built in the 60s and 70s no one was sure how long they would last, but some of the original ones may still be in use, so the durablity may be multiple decades.

    Technically these are are plastic composites, like the carbon fiber or kevlar racing car chassis. They have fibers held in a matrix by the plastic, typically polyester or epoxy resin in thermoset plastic composite, which is the most common type. The resins start as liquid but are cured by a chemical hardener or UV light. Thermoset means once cured, the plastics can’t be readily softened again. The strength of plastic composites comes from the fibers and their orientation. The plastic keeps the fibers properly organized and also binds them together, but the plastic does not contribute significantly to the composite’s strength. Plastic is relatively weak and fibers are relatively strong, but if the plastic bond along the fiber is long enough, the composite takes on the strength properties of the fiber, not the plastic. In other words, the length of the plastic bond along the fiber largely determines the strength of the composite.


    However it’s also possible to make plastic composites using thermoplastics, that is, plastics that can be repeatedly melted and re-formed using heat. Commonly recyclable plastics like polyethylene, polypropylene, polystyrene, etc., are thermoplastics, which is why they can be shredded, melted down and made back into plastic bottles, etc., over and over again. Automobile makers are keenly interested in using thermoplastic composites since they can be made much more efficiently than thermoset plastics. With thermoplastics they can inject or stamp the heated thermoplastics with fiberglass in a mold and viola, they get a new door or engine cover. The plasic can be colored so that painting is not needed. (In contrast, thermoset plastic composites are time-consumingly laminated from multiple layers of fibers at the high end or sprayed from a chopper gun at the low end.)


    The durablity of plastic composites seems pretty well established, and the world has a problem with plastic waste which seems to last for decades thus proving its durability. Perhaps one way to solve the problem of a durable seastead and plastic waste would be to build them from thermoplastic composites. Especially for the portions of a seasted in contact with water most of the time, corrosion resistance seems excellent. (Portions out of the water could perhaps be built with a metal space frame which is weight- and material-efficient.)


    The largest cost of using recycled thermoplastics may be the energy needed to shred and reheat them, but the same is largely true of refining or recycling steel or aluminum. The energy used to make concrete is probably also substantial.

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    I’ve often wondered about composits made from natural fibers like hemp canvas injected with thermoplastics…fairly light, strong, durable, and cheap.

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    With a good, working method for reclaiming plastics from the garbage-patches, that could be divied-up to make the fuel necessary and the plastics reformed into this plastic-saturated fabric laminate. More heat could be used to bond the separate layers into a multi-layered composite. This could be done with positive and negative patterns/molds…



    If you can’t swim with the big fish, stick to the reef

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    Hemp will rot over time. Use smoked bamboo. Bamboo, even if it’s just harvested and dried, will lighten and greatly toughen concrete structures.

    You’re right, metals should be avoided altogether. Magnesium is fairly corrosion resistent though, and its abundance in sea water is over a kg per m3.

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    They say the plastic sargasoo can’t be recycled, but that just means it’s not commercially feasable. All that plastic can be recovered somehow, or at least used for filler.

    I have started a forum on renewable materials and communes: http://www.hombreranch.com/commune/

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    hombre wrote:

    Hemp will rot over time. Use smoked bamboo. Bamboo, even if it’s just harvested and dried, will lighten and greatly toughen concrete structures.

    bamboo and hemp would both rot over time, can smoke hemp just as easily as bamboo.

    though yes, eventually there will be voids where there used to be woody reinforcement.

    You’re right, metals should be avoided altogether.

    ?!!! most of the periodic table is metals…

    Magnesium is fairly corrosion resistent though, and its abundance in sea water is over a kg per m3.

    Yes, that’s quite interesting, however since magnesium has high electronegativity it’s usually used in sacrificial anodes, it being the first metal to corrode/oxidize.

    We’re better off simply using a low-carbon iron, such as wrought iron. On the short term, could use marine grade epoxy, perhaps with sacrifical shavings mixed in.

    Though it’s great that we can get materials for sacrificial anodes from the water.

    It’s reportedly also used by chloroplasts for making fuel, so perhaps we could also.

    We could also make interior furniture or tools out of magnesium. Though due to the highly flammable nature, we’d have to have some very effective fire-retardents available also.

    We with You are a Network, our goal to become technologically-enabled reproducible family communities. http://weyounet.info

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    Elspru, I’m not going to argue with you. I’m pretty sure you could make good cases against your own arguemnts perfectly well. I have better things to do than bandy words.

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