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Need to repair an acrylic water phantom — Parallax Forums

Need to repair an acrylic water phantom

frank freedmanfrank freedman Posts: 1,983
edited 2012-10-23 18:50 in General Discussion
Maybe someone out there has run across something similar (Erco maybe?).

I have a 20CM water phantom that is about 20 years old and it now leaks at a seam. I have separated it the rest of the way, and would like to know if anyone knows of a bonding material that can reseal and bond the pieces back together. Do the surfaces need to be perfectly smooth, .. etc.

Thanks,
Frank

Comments

  • CircuitsoftCircuitsoft Posts: 1,166
    edited 2012-10-17 18:32
    I imagine Model Airplane Glue is what you want. No idea what surface prep is needed, though.
  • W9GFOW9GFO Posts: 4,010
    edited 2012-10-17 18:53
    Model airplane glue is designed for styrene. You want an acrylic solvent cement such as Weld-On 16.

    If it needs to be really strong like a fish aquarium then a specialty acrylic epoxy might be needed.
  • NWCCTVNWCCTV Posts: 3,629
    edited 2012-10-17 18:55
    Contact cement works on bonding pretty much ANYTHING!!!! I have some plastic pieces that I was told by the manufacturer it could not be glued together. I ignored him and tried contact cement and it worked like a charm and was water tight to over 40 feet. In case you have never used it, make sure you arein a well ventilated area. Appy with a small brush to BOTH pieces. Let it dry and press together. Make sure you get it right the first time because if it works the way it is suppose to you will not get it apart for a second try.
  • LeonLeon Posts: 7,620
    edited 2012-10-17 19:09
    I vaguely remember that chloroform was the stuff for bonding Perspex, which is what we call acrylic here.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-10-17 19:23
    Okay, I give up. I googled "water phantom" to see what it is and ended up at a website that sells them, with this description:
    "3D water phantom for automatic dose distribution measurement at TomoTherapy® treatment units
    High precision 3D water tank
    Size, moving range and motor positions optimized for TomoTherapy® Hi·Art® Systems
    3D stainless steel moving mechanism with high speed stepper motors

    The MP3-T water tank is optimized for the use with TomoTherapy Hi·Art treatment units with dynamic arc techniques. Once adjusted to the therapy unit, the water tank has not to be moved to cover all measuring tasks. The 20 mm thick acrylic walls do not bulge during prolonged period of use and feature etched lines for precise tank alignment. Precision stepper motors are mounted on a position for the use in the TomoTherapy Hi-Art gantry. They provide for high detector moving speed of 50 mm/s and high positioning accuracy of ± 0.1 mm. In contrast to analog drives, stepper motor drives do not require regular recalibrations. To operate the tank, MEPHYSTO mc2 software and TBA electronics are required. "

    I still have no idea what a water phantom is, except that it looks like an aquarium with "attachments." (But thank goodness it's a "3D water tank." Heaven knows what a 2D or 4D water tank would look like!)

    -Phil
  • xanaduxanadu Posts: 3,347
    edited 2012-10-17 20:24
    It is a calibration device?

    I looked up some waterproof glues this one seemed like it might work.
  • jonesjones Posts: 281
    edited 2012-10-17 21:44
    How was it originally bonded? I just repaired an acrylic water phantom that was put together with silicone. One side had come off and the rest of the bonds looked iffy so I pulled the whole thing apart and started over. Aquarium sealant is probably the safest to use, but a good silicone sealant from the hardware store will probably work too. Not difficult but just do one side at a time and let it cure before moving on. Silicone will obviously fill gaps.

    If it was solvent-welded, you need some Weld-On #4 acrylic solvent. Ethylene dichloride works well too if you're in a lab environment and have it around. The solvent just flows in via capillary action and it has no gap-filling capability at all. The solvent literally dissolves the two surfaces and they flow together, with the solvent slowly diffusing away. Weld-On 16 is basically the same as #4 except it has acrylic dissolved in it to make it thick. It works, but it can be hard to get into a joint unless the whole side came off and it's horribly messy. If you can get a decent looking joint with it you're doing better than I am.

    If the tank was originally solvent welded you can probably still use silicone, but not the other way around. If they used silicone before, use it for the repair. If you do a solvent weld that doesn't look trustworthy, you can add a bead of silicone to provide a seal. I'd fill it and let it sit for a day or two to make sure it will hold before using it.

    Incidentally, "phantom" is a generic term for something that takes the place of tissue in a scanner (e.g. CT or MRI) or radiation treatment system (gamma, proton, etc). They're used for calibration, testing, research, etc. They often use water because tissue is mostly water. Sometimes acrylic blocks or shapes or a special cross-linked polystyrene called Rexolite are also used. There are fancy ones that can hold sensors or pieces of radiographic film for special purposes.

    [edit]: I've also heard chloroform works well, but I've never tried it. Adequate ventilation is obviously in order with any solvent.
  • jonesjones Posts: 281
    edited 2012-10-17 22:03
    Phil Pilgrim (PhiPi) wrote: »
    Okay, I give up. I googled "water phantom" to see what it is and ended up at a website that sells them, with this description:
    "3D water phantom for automatic dose distribution measurement at TomoTherapy® treatment units
    High precision 3D water tank
    Size, moving range and motor positions optimized for TomoTherapy® Hi·Art® Systems
    3D stainless steel moving mechanism with high speed stepper motors

    The MP3-T water tank is optimized for the use with TomoTherapy Hi·Art treatment units with dynamic arc techniques. Once adjusted to the therapy unit, the water tank has not to be moved to cover all measuring tasks. The 20 mm thick acrylic walls do not bulge during prolonged period of use and feature etched lines for precise tank alignment. Precision stepper motors are mounted on a position for the use in the TomoTherapy Hi-Art gantry. They provide for high detector moving speed of 50 mm/s and high positioning accuracy of ± 0.1 mm. In contrast to analog drives, stepper motor drives do not require regular recalibrations. To operate the tank, MEPHYSTO mc2 software and TBA electronics are required. "

    I still have no idea what a water phantom is, except that it looks like an aquarium with "attachments." (But thank goodness it's a "3D water tank." Heaven knows what a 2D or 4D water tank would look like!)

    -Phil

    That's an accurate, if overly commercial description. The tank has "attachments" to hold probes, which are then moved by the stepper motors from the entrance window (where the radiation enters the tank) towards the opposite side so measurements are taken with increasing water thickness, simulating increasing tissue thickness. The idea is to get the relationship between radiation dose and tissue thickness so that when a specific organ or region in the body needs to be treated, the clinician or physicist can adjust the dose accordingly. The etched lines and such are just because in radiation treatment systems, phantoms (or patients) are typically positioned using laser cross-hair references.

    Great comment re the 2D/4D water tank. I spilled my tea laughing at that.
  • frank freedmanfrank freedman Posts: 1,983
    edited 2012-10-18 01:02
    I would save my money on a 2 D tank as it will likely not have the capacity needed to do much of anything. A bit of warning is in order though regarding the 4D tank: avoid becoming entrapped in the direction of (time) travel.

    As tl the 20 cm water phantom, it is used for testing CT systems.
  • RDL2004RDL2004 Posts: 2,554
    edited 2012-10-18 05:16
    You guys need to be aware of the difference between gluing and solvent welding. Most thermoplastics are "glued" by solvent welding. I sent a sample of what is probably the biggest selling "plastic cement" (model airplane glue - the liquid stuff, not the kind in a tube) in America to an analytical lab about 8 years ago, it was over 95% methyl ethyl ketone. The rest was just some higher boiling (slower evaporating) solvents. There were no solids to speak of and the solvents "don't know" what they're melting dissolving.





    edit: Technically speaking, I probably should have said adhesives instead of "gluing"
  • frank freedmanfrank freedman Posts: 1,983
    edited 2012-10-23 18:50
    I found a local supplier called Desert Star Plastics here in Phoenix. They had a material called Weld-on #4 (label actually was methyl chloride) on hand in small quantities. After reading all the suggestions, I would have liked to have used Weld-on #16 but they did not have it. The difference being that the #16 had acrylic dissolved in it and could have acted as a filler. The Weld-on #4 was applied liberally enough to the surfaces and after mating, I stood on them for a bit. The repair looked good all the way around with a couple of potential thin areas. Monday it was filled and sealed and as it had not leaked, the bubbles from the (tap) water were bled out and then resealed. No leaks so far, if it makes a couple more days, it will be used for cal and performance testing.

    Thanks for all the great info,

    Frank
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