I do not need specifics about oxygen or water vapor, these are just examples I picked arbitrary. I am located in Florida. I am looking to an alternative to fluorination. What other process may achieve similar results (creates a barrier in a polyolefin such as PE or PP)? Is there an additive that would produce a barrier effect?
There are several oprions depending on the level of protection you are looking for and the manufacturing process. Will be happy to sort it out with you if you provide me with more info. DWeissmann@aol.com
Thank you, patprimmer and telaviv for your input. We produce mainly injection molded plastic containers, some of these are use to store foods. We use different plastics including PC, PE and PP. We do not have major problems with PC, but due to cost reasons, we can not use this material for all markets or product lines. PP is our most common material, but some substances will permeate through it. If the substance has pigments or colorants, it could even permanently stain the container. I am researching three possible alternatives to decrease the permeability of PP. One is an additive, that way we only need to compound it in our plastics. No major increase in cost, except material cost. No luck yet for this alternative. The second alternative would be an in line process after (injection) molding the product. So far, what we have tested, is not effective or to expensive. The third alternative would be a batch process, like fluorination. Fluorination is effective, but our cost estimates are some what on the high side right now. I am open to any suggestions on how to decrease the permeability of a polyolefin.
To answer telaviv questions, regarding the level of protection, at this point I am interested in what I can get. The process is injection molding.
PET might offer better barrier properties at a reasonable raw material cost.
Barrier and cost ballance is the main reason it is used for beverage bottles. You mightneed a post moulding crystalisation process to get optimum barrier.
It will never be quite as impermiable as stretch blow moulded PET as the stretching process lines up the molecules and crystals to an extent that cannot be achieved by heat treatments alone.
Beverage bottles are obviously approved for food contact.
Despite this being an exceptionally large market (I guess quite a few billion $ US per year world wide), no one has come up with a better alternative to date. You can bet many have tried.
Regards
pat
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
There are many possible ways of improving the barrier properties of polyolefins, but it is a cost/performance issue. Judging from your being pushed out of PC due to cost, most "solutions" would also be too expensive; based on the feed materials, equipment and/or operations (labor) costs. If you have successfully tried fluorination, perhaps then you might want to address the cost of fluorination issues directly.
There are many ways that you might be able to lower the fluorination treatment costs. The cost will depend on container size and shape, number (peak load and baseline), and application (barrier to what, or protection from what, and for how long). It will also depend on whether you do the treatments on-site yourself or have to pay for treatments performed by a third party.
As you may guess from my handle, this is an area that I work in a lot.
DuPont sell a Nylon type of material called SELAR that is used as an additive to PE to give it barrier properties.
This is used to lower the permeation in blow moulded bottles and drums.
The principle is mechanical in that the Nylon forms platelets and like overlapping armour this produces a tortuous path for the escaping molecules.
I don't know if it will work with injection moulding because the mechanical shearing effect is different.
Regards,
Robin Enderby
Am interested in whether flourination would be helpful in my situation outlined below.
From: Philip Anthony, President
VertiGONE, Inc
Regarding: Plastic Permeability Problem
Dear Sir:
My company is involved in a multiyear bet-the-company development activity. We are developing a consumer medical product. This product is a goggle device, which gives the user a visual pathway to follow for a recognized therapeutic head movement. The device involves a plastic gyroscope-like device. This device has a buoyancy neutral inner sphere floating in a fluid in a clear plastic outer sphere. We have encountered significant problem when we used water for the fluid to be contained in the outer sphere. We have found that the water permeated through the outer sphere material. The outer sphere has been produced in CYRO Technologies Acrylite Plus ZKM and GE Plastic Lexan 143.
We found the attached information, which explained the water permeability of both of these materials. By using silicone oil 20 cst with the higher molecular weight we anticipated that we should get containment of the outer sphere fluid as well as a specific gravity close to that of water such that previously produced inner spheres of SG =1 could be used. We have found that mineral oil is well contained within outer spheres made of both of the above materials, but the specific gravity is not close enough to allow use of previously produced inner spheres.
The questions: 1) Will silicone oil with a higher viscosity be contained within the outer spheres of either of the above materials? 2) Do you have other materials that you would suggest for this activity? Bear in mind that the material used needs to be nontoxic to the user. If this question is not in your area of expertise could you refer me to a knowledgeable source?
I think that quite high percentages of DuPont's Selar are required to give the desired effect.
I guess that the barrier gets better with the amount used. I think 10% is the starting point, but I suggest you contact your local DuPont dealer.
Good Luck,
Robin Enderby
BMC Ltd. UK
ps sorry for the delay in responding - I don't visit this forum often.
