The Doll Forum

Hi all,

I recently become a doll owner. Since I have professional background in the material science, I looked around the material of the dolls. Here are some questions I'd like to ask the manufacturer. (I decided to ask here because I'm interested in this brand, and I do want to see it improve. )

First, I noticed that most of the dolls have stainless steel as the main material for their frames (skeletons). My best guess is that the stainless steel has the strength and corrosion resistance for being durable in the doll. But from what I know, most of the real-size dolls have relatively heavy weight (e.g. a doll with a height about 160 cm is weighted around 30-35 kg/ 66-77 lbs), and can be a problem when it comes to handling the doll. I wonder what's the portion of the skeleton weight in the total weight of a doll. If it is high, I wonder if replacing the stainless steel with high strength aluminum alloy will help in terms of reducing the weight. 7075 and 7068 Aluminum alloy might be good choices for this situation.

Second, I heard that the TPE will leak oil out of it gradually, resulting in a sticky skin and degradation of TPE. Regular care can minimize its effect, but it takes a lot of patience for the doll owner. I'm not a specialist in polymer, but I wonder if you can do surface treatment on the doll to reduce the oil leakage and improve the touch feeling. A coating or surface chemical treatment can improve the surface stability without altering the bulk properties of an alloy, and I think it might still be true in the case of a TPE (or silicone) doll.

I actually has an idea for the heating system, but I have to think it more thoroughly before I present it. Just want to hear some opinions from the manufacturer about these issues. Thx in advance!

the skeleton is around 5kg or less for most TPE dolls. In general, TPE is the biggest portion for the doll weight.

Thanks for your suggestion. Surface treatment is possible, we need to check with R&D Institution for the further study. I'd PM you for more info

6YeDoll wrote:Thanks for your suggestion. Surface treatment is possible, we need to check with R&D Institution for the further study. I'd PM you for more info

I saw your PM. However, since I'm still a newbie on the forum, I can't reply the message. I'll just reply here for now.

To be honest, the surface treatment stuff is just a concept for me. Like I said, I'm not a specialist on polymer, so I can't tell you the exact composition of the desirable coating material. But I would say that this coating can be a polymer that is wear- and dye- resistant, and contains no oil, nor would it be permeable to oil. If it has a silky touch, it would be the ideal case (but the silky touch can also be done by applying a second coating on the first protective coating). The coating can be applied by creating a chemical reaction on the surface (bond coating), or spraying the coating material on the doll surface (but the adhesion between the coating and your TPE formula must be good in this case). The depth of the coating is usually withing 100 um in the case for alloy, and I think this should be sufficient for the case here.

Sorry I can't help you directly, but I believe your R&D team would have the proper knowledge and instruments to do such kind of research.

BTW it's amazing to see the manufacturer is really willing to hear from the potential customers. I'm really impressed.

Sexy Sex Doll wrote:the skeleton is around 5kg or less for most TPE dolls. In general, TPE is the biggest portion for the doll weight.

Damn, looks like even if the material of the skeleton is changed to high strength aluminum alloy, the doll would only lost about 2 kg. Well...

DrMetal wrote:

Sexy Sex Doll wrote:the skeleton is around 5kg or less for most TPE dolls. In general, TPE is the biggest portion for the doll weight.

Damn, looks like even if the material of the skeleton is changed to high strength aluminum alloy, the doll would only lost about 2 kg. Well...

Yeah, we were just talking about the negligible weight contribution of the skeleton here:
IdeaTpeDoll: tall and lightweight (poll)

ZZZZ wrote:

DrMetal wrote:

Sexy Sex Doll wrote:the skeleton is around 5kg or less for most TPE dolls. In general, TPE is the biggest portion for the doll weight.

Damn, looks like even if the material of the skeleton is changed to high strength aluminum alloy, the doll would only lost about 2 kg. Well...

Yeah, we were just talking about the negligible weight contribution of the skeleton here:
IdeaTpeDoll: tall and lightweight (poll)

I saw the discussion in your thread. That's interesting actually, and the discussion is constructive in my opinion. If there is some information about the condition of the TPE/silicone casting process, as well as the structure of the doll, we might be able to come up with some critical ideas for weight reduction. Wonder if you happen to know someone or somewhere to look for such kind of info?

DrMetal wrote:I saw the discussion in your thread. That's interesting actually, and the discussion is constructive in my opinion. If there is some information about the condition of the TPE/silicone casting process, as well as the structure of the doll, we might be able to come up with some critical ideas for weight reduction. Wonder if you happen to know someone or somewhere to look for such kind of info?

Information about processes and doll structure is scattered in a thousand different threads. Are you looking for something in specific?

ZZZZ wrote:

DrMetal wrote:I saw the discussion in your thread. That's interesting actually, and the discussion is constructive in my opinion. If there is some information about the condition of the TPE/silicone casting process, as well as the structure of the doll, we might be able to come up with some critical ideas for weight reduction. Wonder if you happen to know someone or somewhere to look for such kind of info?

Information about processes and doll structure is scattered in a thousand different threads. Are you looking for something in specific?

The parts I'm interested in are the temperature for TPE/silicone casting and the internal structure of doll torso and head. Did you see any of them? Thx!

DrMetal wrote:The parts I'm interested in are the temperature for TPE/silicone casting and the internal structure of doll torso and head. Did you see any of them? Thx!

I don't have the exact numbers on hand, but I think TPE casting is around 400 degrees Fahrenheit, and silicone is less than half that.

TPE dolls have no "internal structure" other than the skeleton.

Because of the lower casting temperature, silicone dolls may have a more varied internal structure. I've read that many silicone dolls have foam on the inside.

Well, a good next step would be a strong polymer metal-binding lattice with a high air content for the initial pour. Then molecularly bound TPE, or similar skin-like material as an external layer. This would greatly reduce the bulk weight, but also be initially challenging and expensive.

ZZZZ wrote:

DrMetal wrote:The parts I'm interested in are the temperature for TPE/silicone casting and the internal structure of doll torso and head. Did you see any of them? Thx!

I don't have the exact numbers on hand, but I think TPE casting is around 400 degrees Fahrenheit, and silicone is less than half that.

TPE dolls have no "internal structure" other than the skeleton.

Because of the lower casting temperature, silicone dolls may have a more varied internal structure. I've read that many silicone dolls have foam on the inside.

Good to know about this info.

It looks like we do have some space for reducing the weight. If your info is correct, the torso and head look like good places to have some space in it, so we don't need to introduce unnecessary weight on the doll. Material- wise, If the casting temperature of TPE is around 400 degree F, Teflon might be utilized as part of the frame (or the shell for internal spacing) since it can stand up to 500 degree F without degradation. Aluminum alloy sheet might also be a good choice.

But I guess we might just all missed the possible difficulty the manufacturers would face when it comes to actual processing. Hope we can see the opinions from them soon.

QL57812 wrote:Well, a good next step would be a strong polymer metal-binding lattice with a high air content for the initial pour. Then molecularly bound TPE, or similar skin-like material as an external layer. This would greatly reduce the bulk weight, but also be initially challenging and expensive.

Indeed. I guess the internal material can be even more porous than TPE, which could have less density in the major volume for the doll. I wonder if the density or degree of porosity of TPE can be controlled?

The skin is important. I actually strongly believe that the surface treatment will be the key to keep the TPE dolls from heavy maintenance, if the nature of TPE cannot be avoid or new material is not introduced. Even the human body is composed of multi- layer structure. So my best guess for making a realistic doll is also using the multi- layer building technique. But I'll say that if I'm the manufacturer, I would have a strong headache on this part.

In regard to the skin, here's another topic you might be interested in:
IdeaTpeBody: Smooth Skin WITHOUT Baby Powder

ZZZZ wrote:In regard to the skin, here's another topic you might be interested in:
IdeaTpeBody: Smooth Skin WITHOUT Baby Powder

Thx for the info.

Didn't see much of constructive ideas in that thread, but we do know that lots of ppl want a maintenance- free TPE skin.

I think if we know why TPE is porous and whether the porosity of TPE can be controlled, we would be closer to make such kind of skin. Someone in the thread you showed me mentioned the self-cleaning function (Lotus effect). It's definitely ideal for the top surface layer, but if the oil leakage from the TPE can't be stopped, it would be totally useless.

My thought is, if the property of TPE is tunable toward non-oil-permeable, we can make such a layer to cover the surface of the doll first. Then, we can apply nano particles on the layer surface via CVD method to create a self-cleaning/smooth skin. But since I don't know the exact composition and structure of TPE used on the doll, I can't make some more accurate hypotheses myself.