Patrick,
I think that most of the Titebond II is made of aliphatic resin which is a waterproof version of what we think of a white glue. I wouldn't expect that to have a great adhesive property to a plastic substrate unlike the wood it is intended to bond. I think that the Jute and Hemp fibers are very similar in properties. One source for hemp fiber used to be burlap bags but that also could be mostly jute at this point. I think they are again producing hemp fiber up in Canada, but it is still illegal to grow it in the US. Most of the resins you are using like the Gorilla glue are made of single component polyurethane and are cured by moisture in the air for the reaction to take place. It will react faster on a high humidity day than a very dry day as it does need water to complete the reaction. I have done work with hemp and jute composites with two part reaction injection molded polyurethane but never found a great application for the material. It has a lower stiffness than glass and had no real weight advantage as the fibers actually absorb the resin while glass does not so the weight was fairly comparable with lower physical properties. This material is used or was for the inner wheel wells on many cars in the past. It was cheaper than a comparable glass fiber part at the volumes that a GM would use. You have to look at whether you are trying to increase the stiffness of the plastic parts you are reinforcing or just trying to add damping properties to the plastic material. The funny thing about carbon fiber epoxy composites is that if you have very high consolidation of the composite it will ring like a bell! You can easily fool someone into thinking it is a metallic part by the sound of the material.
You'll have to tell me what the word Glare is and abbreviation for. I don't have my sound card working right now so couldn't listen to the U-tube video.
ps. I just remembered where we got the hemp fiber. I bought that by the bail, it looked like a bail of hay but was loose hemp fiber. We used that in plaster pattern making as a reinforcement. I think if you contact US Gypsum they can tell you where to get the hemp fiber at a low cost.
I think that most of the Titebond II is made of aliphatic resin which is a waterproof version of what we think of a white glue. I wouldn't expect that to have a great adhesive property to a plastic substrate unlike the wood it is intended to bond. I think that the Jute and Hemp fibers are very similar in properties. One source for hemp fiber used to be burlap bags but that also could be mostly jute at this point. I think they are again producing hemp fiber up in Canada, but it is still illegal to grow it in the US. Most of the resins you are using like the Gorilla glue are made of single component polyurethane and are cured by moisture in the air for the reaction to take place. It will react faster on a high humidity day than a very dry day as it does need water to complete the reaction. I have done work with hemp and jute composites with two part reaction injection molded polyurethane but never found a great application for the material. It has a lower stiffness than glass and had no real weight advantage as the fibers actually absorb the resin while glass does not so the weight was fairly comparable with lower physical properties. This material is used or was for the inner wheel wells on many cars in the past. It was cheaper than a comparable glass fiber part at the volumes that a GM would use. You have to look at whether you are trying to increase the stiffness of the plastic parts you are reinforcing or just trying to add damping properties to the plastic material. The funny thing about carbon fiber epoxy composites is that if you have very high consolidation of the composite it will ring like a bell! You can easily fool someone into thinking it is a metallic part by the sound of the material.
You'll have to tell me what the word Glare is and abbreviation for. I don't have my sound card working right now so couldn't listen to the U-tube video.
ps. I just remembered where we got the hemp fiber. I bought that by the bail, it looked like a bail of hay but was loose hemp fiber. We used that in plaster pattern making as a reinforcement. I think if you contact US Gypsum they can tell you where to get the hemp fiber at a low cost.
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I'm not one of you materials experts, but when you're not dealing with composites, jute fabric is basically ruined when it gets wet, and hemp isn't, so that's different. edit: p.s. just talking about stains, as far as "ruined", if that wasn't clear. It does get kind of easily shred-able when wet, too.
I have used 100% hemp twine for lots of projects of a more aesthetic nature. I saturate it with shellac, or white glue, or wheatpaste. In all cases, it seems almost like rock after, but so does thick paper mache when you do it right...
I have used 100% hemp twine for lots of projects of a more aesthetic nature. I saturate it with shellac, or white glue, or wheatpaste. In all cases, it seems almost like rock after, but so does thick paper mache when you do it right...
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First, I was referring strictly to polyurethane liquid glue (like Gorilla Glue)which is a one part air cured. This glue always expands, sometimes more than others depending on the moisture content of the substrate and the air.
In two part cast poly the expansion depends on several factors: age of the material, humidity, and speed of casting. The resin is hydroscopic and absorbs moisture as it ages, so shelf life is the biggest factor. The older the material, the more moisture it has absorbed and the more the expansion. It will absorb some moisture while it cures and of course the longer it hangs around before being mixed and poured the more moisture it will absorb. In thousands of castings I have seen a wide variety of expansions - never a contraction (that I could tell.) Moisture content of any substrate materials is also a huge factor which is why you cannot use just any substrate or mold material. They cannot contain moisture. Expanding foam has moisture in it, that's why it expands.
As to the autoclave, my point was that carbon fiber does not reach its full strength unless it is autoclaved. I do not know the precise strength difference between natural cured and autoclave cured but from what I have read it is substantial. No commercial application that I know of would not use an autoclave if the part is for usage in a strength critical application. I have seen it dispensed with for parts that were for cosmetic usage however. I was never referring to the fibers themselves, but the composite materials that result.
ummm..don't quit your day job
Question of the week: What's the difference between "hydroscopic" and "Hygroscopic"? - The Four Ages Of Sand
Question of the week: What's the difference between "hydroscopic" and "Hygroscopic"? - The Four Ages Of Sand
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Earl,
Yes water and polyurethane are not exactly compatible when you are molding, the water combines with the Isocyanate side of the two components to create CO2 gas and is many times a component of foamed urethane at least now that we can't use CFC's any longer.
As far as the autoclave which I have written plenty of cure schedules for the main reasons for that are two fold. The consolidation of the composite is best when done in the autoclave as the pressures you can generate per square inch of surface is higher than a process such as resin transfer molding which will definitely have a higher void content. The other part of the process is the ramped temperature rate used for cure. You want to slowly raise the temperature to start the polymerization and allow any out-gassing to occur while the resin is still in a fairly low viscosity state. There is actually vacuum on the part before we switch over to pressurizing the autoclave to pull out the gasses. The autoclave is also filled with nitrogen which does not burn and also creates an inert situation between the gas and the resin system. What most people don't understand and what you are referring to with the hardness of the epoxy is actually the properties are not at maximum until the resin reaches a critical temperature during the cure. Any epoxy that is not cured at elevated temperature will soften the minute it reaches a temperature above the cured temperature, the glass transition point of the resin is set by the maximum cure temperature.
As far as urethane or any other polymer expanding in a closed mold that just doesn't happen if the material is properly processed with correct ratios of the components. Now if it is an open molded part then it most assuredly will expand while curing but once cured I guarantee that it will shrink back at least a portion when the cure is finished. If the material would truly expand in a closed mold you would have one hell of a time getting the part out of the mold. I'll qualify that statement by saying that yes while reacting and filling the mold the material does expand until it fills the cavity, but then it will shrink back a small percentage while polymerization completes. Typical shrinkage for a two part rigid high density foam is about 0.005" of and inch per inch.
All of the single component urethane's require a moisture cure which is usually provided by the moisture in ambient air. Add a couple of drops of water to let's say Gorilla glue and you will get a small amount of foaming happening at the same time lowering the density and properties of the material that is for sure. The only thing about the single component urethane's is that most that I can think of would be considered an elastomeric type material and not really considered a rigid type of material. The exception I can think of is single component low density foam material such as you see in spray cans of insulation foams but they are typically very low density perhaps 1 or 2 lbs per cubic foot.
Yes water and polyurethane are not exactly compatible when you are molding, the water combines with the Isocyanate side of the two components to create CO2 gas and is many times a component of foamed urethane at least now that we can't use CFC's any longer.
As far as the autoclave which I have written plenty of cure schedules for the main reasons for that are two fold. The consolidation of the composite is best when done in the autoclave as the pressures you can generate per square inch of surface is higher than a process such as resin transfer molding which will definitely have a higher void content. The other part of the process is the ramped temperature rate used for cure. You want to slowly raise the temperature to start the polymerization and allow any out-gassing to occur while the resin is still in a fairly low viscosity state. There is actually vacuum on the part before we switch over to pressurizing the autoclave to pull out the gasses. The autoclave is also filled with nitrogen which does not burn and also creates an inert situation between the gas and the resin system. What most people don't understand and what you are referring to with the hardness of the epoxy is actually the properties are not at maximum until the resin reaches a critical temperature during the cure. Any epoxy that is not cured at elevated temperature will soften the minute it reaches a temperature above the cured temperature, the glass transition point of the resin is set by the maximum cure temperature.
As far as urethane or any other polymer expanding in a closed mold that just doesn't happen if the material is properly processed with correct ratios of the components. Now if it is an open molded part then it most assuredly will expand while curing but once cured I guarantee that it will shrink back at least a portion when the cure is finished. If the material would truly expand in a closed mold you would have one hell of a time getting the part out of the mold. I'll qualify that statement by saying that yes while reacting and filling the mold the material does expand until it fills the cavity, but then it will shrink back a small percentage while polymerization completes. Typical shrinkage for a two part rigid high density foam is about 0.005" of and inch per inch.
All of the single component urethane's require a moisture cure which is usually provided by the moisture in ambient air. Add a couple of drops of water to let's say Gorilla glue and you will get a small amount of foaming happening at the same time lowering the density and properties of the material that is for sure. The only thing about the single component urethane's is that most that I can think of would be considered an elastomeric type material and not really considered a rigid type of material. The exception I can think of is single component low density foam material such as you see in spray cans of insulation foams but they are typically very low density perhaps 1 or 2 lbs per cubic foot.
I stand corrected. Never knew that.
Kindhornman - thanks for the refresher on autoclaves.
I do see evidence of the poly expanding and then shrinking just a bit on final cure. Since I can't afford industrial injection equipment my mixing and pouring are all done out in the open. But the supplier warns me that the poly needs to be kept in an air free space or it will absorb moisture (hygroscopic!!) and create more expansion on polymerization just like the foam or Gorilla glue.
I do see evidence of the poly expanding and then shrinking just a bit on final cure. Since I can't afford industrial injection equipment my mixing and pouring are all done out in the open. But the supplier warns me that the poly needs to be kept in an air free space or it will absorb moisture (hygroscopic!!) and create more expansion on polymerization just like the foam or Gorilla glue.
Earl,
We should have meet years ago, I could have molded your parts for you. Glad I could clear up the autoclave situation and try my best to help where I can.
ps. Large quantity polyurethane materials are always shipped with a nitrogen blanket over the material to keep out any water that would affect the resin side of the system. In use we use extremely dry air that has been conditioned with automatic regenerating desiccant dryers. The dryer alone cost about $2,500 dollars just for that one function.
We should have meet years ago, I could have molded your parts for you. Glad I could clear up the autoclave situation and try my best to help where I can.
ps. Large quantity polyurethane materials are always shipped with a nitrogen blanket over the material to keep out any water that would affect the resin side of the system. In use we use extremely dry air that has been conditioned with automatic regenerating desiccant dryers. The dryer alone cost about $2,500 dollars just for that one function.
What moving parts can be made of carbon fiber? Driveshafts? Wheels? Steering shaft? You don't get much weight reduction vs value with those.
Carbon fiber is a weight savings only, its good at that. But its savings are not huge. It can add up in something like an airplane however. In loudspeakers, its not that useful because there are lighter materials, they just cost even more - like beryllium. But the actual material usage is so small that its not a big factor. I can imagine that a beryllium wheel could get pricey.
Speed of sound in material is also consideration.
Some of these considerations must come into play as wavelength become comparable and shorter to dimensions of radiating surface; leading to potential standing wave and diffraction effects. Swapping beryllium for aluminum or titanium or carbon base diaphragms of equal mass in compression drivers leads to different performance.
Some of these considerations must come into play as wavelength become comparable and shorter to dimensions of radiating surface; leading to potential standing wave and diffraction effects. Swapping beryllium for aluminum or titanium or carbon base diaphragms of equal mass in compression drivers leads to different performance.
A major contribution is fiber orientation, and performance characteristic within binding matrix.
Barleywater,
You are very correct that the configuration of the weave make a fairly large change in the physical properties of a composite material. Ultimately a uni-directional fiber has the highest flexural strength but there are not any standard weaves that would work that way in a round application. A special woven preform could be made with all the fibers placed radially but that would be an expensive proposition for a speaker cone application. Even in an epoxy matrix the fiber configuration is the dominant factor in flexural modulus and not the epoxy matrix. These are some of the choices that have to be made when any composite is designed the actual type of weave the final fabric obtains is one of the first things to look at.
Earl,
I understand that in a composite horn that whether you are using glass or carbon that you could achieve similar final physical strength by just changing the thickness of the two different materials, glass would just have to be thicker, but the internal damping properties would be different, though with proper design you could damp either material.
You are very correct that the configuration of the weave make a fairly large change in the physical properties of a composite material. Ultimately a uni-directional fiber has the highest flexural strength but there are not any standard weaves that would work that way in a round application. A special woven preform could be made with all the fibers placed radially but that would be an expensive proposition for a speaker cone application. Even in an epoxy matrix the fiber configuration is the dominant factor in flexural modulus and not the epoxy matrix. These are some of the choices that have to be made when any composite is designed the actual type of weave the final fabric obtains is one of the first things to look at.
Earl,
I understand that in a composite horn that whether you are using glass or carbon that you could achieve similar final physical strength by just changing the thickness of the two different materials, glass would just have to be thicker, but the internal damping properties would be different, though with proper design you could damp either material.