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Polymer capable of steel/aluminum strength with same thickness ?

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bones21

bones21

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Feb 7, 2006
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I am working on a project with very specific dimensions, therefore I am limited to a certain thickness where steel & aluminum have been used successfully in the past.

My project is a rectangular box of sorts that will be injection molded and I need to know what polymer will give me the equivalent properties of 1mm of steel or aluminum.

I know that in most cases a "thicker" polymer is used to make up for the loss of strength. This is not an option for me.

I have a 1:1 ratio to work with.

I want to be cost effective, yet I need the strength of metal and the impact resistance of polycarbonate. I also need a high temp. polymer.

My first choice was Nylon 6/6 glass filled, but the data I have read suggests that it is not very good in the Impact area.

Ok, so basically I need a Poylmer ( additives can be entertained ) that has the strength of 1mm steel, the impact resistance close to Polycarbonate and the strength of carbon fiber ( or fiber glass / kevlar ). With very low mold shrinkage !

My real big question is this... Is there a Polymer out there that can give me the best of all of these properties packed into a 1mm thick package ?

Any and all help are greatly appreciated. If you need more information from me in order to help, then please ask me questions.

Thank you.
 
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The short answer is no.

Only steel has all the properties of steel.

Only aluminium has all the properties of aluminium.

I don't intend to ask 50 questions just to find the information I need to know in order to help you for free.

Please tell us what you want to make, with data such as load, conditions of load application, temperature and exposure to environmental effects, and any special requirements, like food contact, flame retardant, transparent, etc.

Regards

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As mentioned by Pat, each material has its own particular balance of properties. The good news is that several glass fibre filled polymers will provide the strength you need. The problem comes with the impact resistance for a glass fibre filled material. Also, as mentioned chemical resistance and HDT etc need to be considered. You mention the impact strength of PC as being the target but you must bear in mind that PC has about the best impact resistance there is so in effect you want the best strength there is from a filled system plus the best impact resistance known from an unfilled polymer. That is probably not possible and a compromise will be needed. The only chance may be something like carbon fibre filled epoxies where you lay down sheets of carbon fibre matt in layers. I read that such materials have an excellent balance of strength and impact resistance but they are expensive and made by hand lay-up so they can't be injection molded.
 
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The strength of steel varies from 100 MPa to > 2000 MPa. What do you need?

Since you state the need for "impact resistance", I will assume thermosets won't work. The highest strength thermoplastics are liquid crystal polymers.

You can try Ticona's Vectra:


or DuPont's Zenite:


or Solvay's Xydar:


Regards,

Cory

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Sounds like metal works so why change? If you hope to save money I hate to disappoint but unless you have very high production volumes in mind, this isn't a good path to cost savings. Plastics that can match steel or aluminum at 1mm thickness are very expensive and not easy to mold. If you need impact of unfilled PC then you're out of luck.

The previous posts have good suggestions about reviewing your requirements and materials that approach metal for properties. Maybe you can see where your critical requirements can be met with plastics enough to give a good substitution.

Mike
 
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My project is a rectangular box of sorts that will be injection molded and I need to know what polymer will give me the equivalent properties of 1mm of steel or aluminum.

I know that in most cases a "thicker" polymer is used to make up for the loss of strength. This is not an option for me.

I have a 1:1 ratio to work with.

Hmm. Try 4 layers of 1:1 warp and weft woven kevlar and carbon fiber 200 gsm. Lay them so for each layerthe weaves are at 45 degrees to each other layer. Resin? Dow's Derakane 470 will remain mechanically strong with a continuous operating temp of 180 deg. Centigrade. The carbon fiber will provide great stiffness while the Kevlar has remarkable tensile strength. The combination will provide a strong, impact and temperature resistant material.
Downside? very expensive and difficult to form.

Fortune favours the bold and avoids the unprepared.
 
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Thanks for all of the quick responses.

I am aware that I cannot get all of the properties of steel/aluminum in a Polymer, I was just wanted as many as possible with cost in mind.

A standard carbon/kevlar wrap is not what I had in mind. I mentioned those materials as "fillers" for a base thermoplastic resin; like nylon or PC.

I need the polymer to have an operating temp. of around 4-500 degress fahrenheit.

Nylon is cheap and gives me the temp. rating that I need, but I was wanting to add something to it to give it some PC attributes.

As far as I know there isn't a polymer that combines nylon&PC, is there ? I think the difference in melting points would be the reason for this.

For my needs and the money I am allowed, I think that a glass filled nylon with an impact modifier may be the best answer ?

I am basically trying to get the best of all worlds, strength, impact resistance and a high operating temp. ( all with cost and injection molding in mind )

I am completely new to the world of polymers and reinforcing materials, so please take it easy on me. I have done a lot of research on the subject, but I thought that a nice place such as this would give me some more idea. Or at least give me ideas that I have not though of before.

As far as my project goes... I have the design finished and I know what it will look like, but I am trying to figure out exactly what I want the finished product to be made out of. While I was set on glass filled nylon... I started to think that maybe I could make it even stronger and more durable if I did my homework. I am trying to get my ducks in a row before I have the expensive molds made. So I am rechecking every aspect of my project. I don't think anyone here can blame me. The product may be inexpensive, relatively speaking, but the molds are a different story.

I want to bring a common product to market, but I want it to stand alone in quality. While a carbon fiber additive will probably cost way too much, I am just looking for any, and all, alternatives.

Again, thanks for all of your responses. I am taking notes.

 
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You are right. You don't want to make tools only to discover the material that you sized the tools for won't work. Thus consider some prototypes to start. You will then find if 1mm 30% glass-filled nylon will work for your application. Some plastic sheet suppliers will carry glass filled nylon though 1mm is pretty thin.

Plus you need to consider your heat requirement. If you are talking 400 - 500 F of continuous temperature exposure, nylon isn't going to cut it. Short term exposure is possible and can be viewed by the datasheets HDT (Heat Deflection Temp) or DTUL(Deflection Temp Under Load) values. Impact modifiers will adversely affect heat resistance. There are datasheet values for Continuous Use Temperature though suppliers are less apt to provide.

I think you will find that as you increase your requirements for heat and strength the cost will also rise.

Mike
 
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I guess (I still know very little of your real requirements) exotic materials like Polysulphone. Polyether Sulphone Liquid Crystal Polymers and Polyetherimide should have a better balance of properties for your application.

Material selection is all about selecting the best overall compromise in required properties.

Glass filled nylon 6.6 will have the heat deflection temperature (HDT) you require, but will fall well short of the continuous temperature use (CUT) you require.

Data sheet figures for impact strength of glass filled nylon does not correlate well with real world failures.

Glass filled materials have very different properties in different directions due to the glass fibres lining up in direction of flow in the moulding. This give a wood grain type effect to the properties.

From the very limited information, it sounds like you need an exotic, or a high temp nylon like an aromatic nylon or nylon 4.6

I can't remember all the properties of all these materials, but I have access to data. As I said earlier, I am not prepared to do extensive data research without sufficient info to ensure I am not on a wild goose chase.

Data sheets fall well short of the full story. As your application sounds quite difficult, you need good unbiased professional advice in this regard.

Regards

eng-tips, by professional engineers for professional engineers
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The properties of glass filled polymers are not nearly as good as what is represented on data sheets. The reason is that the properties (modulus and strength) are only enhanced in the direction the long axis of the fibres are aligned in. These optimal properties are what you find on a datasheet because the measurements are made on test bars with near perfect alignment on the fibres. At right angles to that there is no reinforcement at all. On top of that there is the weld line problem that Pat mentioned, where the flow lines meet there is an area with strength below that of the unfilled polymer! If you are looking into material properties you can do a search and find good information at for free.
 
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One alternative you may wish to consider is to make your part from bulk molding compound (BMC)or sheet molding compound (SMC). These are made into parts using a compression molding process rather than injection molding. Thermoset resins are used so you can get the high service temperature and long fiber at 60% fiber volume will give much higher strength than anything you can get with injection molding. The cost is far lower than hand-layup.
 
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I suggest contacting the poster of the following re a suitable polymer:

Have new polymer that is not glass filled, need conductive coating [California]
"We are a manufacturer looking for a process to plate a polymer that has a Rockwell B 80. It is very hard, very dense, no filler, acids don't touch it, and it's non-conductive. We need to find a coating process, or combination of processes to end up with .001 per side of conductive material, preferably nickel. Various types of PVD have been tried, in order to get a plate-able surface. This new material machines like metal, we have to use diamond-tipped tools to machine it. The CTE is closer to metals or aluminum, than it is to plastics, so if we can successfully plate it, the "Fat Lady" will sing."
 
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I suggest not contacting the poster of that information because it describes a hard polymer. Hard means high modulus and the requirements you asked for are high strength and impact resistance therefore the material seems unsuitable.
 
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Thanks, rnd2.
At first, I didn't think so, as he gave an Oxnard (not Chatsworth) address. But, only a sales rep. would ask about plating a material based upon its hardness, not chemical composition, and use the phrase the "Fat Lady" will sing!
Ken
 
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My point is that hardness and impact resistance don't go together. If you make a plot of all thermoplastics (which I have done) you will find that having very high modulus (hardness) have poor impact resistance and vice verse. Plus, as mentioned it sounds very much like a sales pitch and I would take it with more than a grain of salt. So, if he claims a hardness close to metal I assume, based on experience that the impact resistance will not be any good.
 
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Get the salt shaker out.
Anyone familar with KL9C, a plastic stronger than steel, used for encapsulation of Gork by the US military back in 1951?
Limited adhesion to foreign substances, but maybe that's advantageous for some applications.

"Klaatu barada nicto"
 
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