Week 16 - Wildcard week
Assignment
Produce test coupons for your composite fabrication process(es) and test the characteristics of different composites.
We are going to make sample pieces of composites of epoxy. You can vary with combining different textiles, the number of layers, the amount of epoxy you use, etc. After they are finished we will describe the difference between the different example pieces: Are they flexible, hard, nice to look at, etc. We have divided the work between the two groups: Hyejin and Harm do several, same for Nathan and Tessel. We also each have to read the datasheet and safety sheet of Tarbender: the epoxy we will use. It's mean stuff so you have to prepare by reading the manual.
Cotton:
In vacuum bag
In molds
Jute:
In vacuum bag
In molds
Glass fibre:
In vacuum bag
In molds
Plain epoxy
The epoxy we use is Tarbinder.
Instructions
Pot Life: 45 Minutes
Cure time :16 hours
Mix: 2A:1B By VOLUME
Pre-Mixing
Shake Part A and Part B thoroughly
Get your workplace ready
Put protective sheets on the table
Get extra gloves ready
Mixing
Mix for 2 minutes with a stick. (gently, to prevent bubbles)
Pour into a new, clean mixing container and mix again for 2 minutes.
Greater masses of epoxy will reduce pot life
For the group assignment we are going to make example pieces of making composites of epoxy. You can vary with combining different textiles, the number of layers, the amount of epoxy you use, etc. After they are finished we will describe the difference between the different example pieces: Are they flexible, hard, nice to look at, etc. We have divided the work between the two groups: Hyejin and Harm do several, same for Nathan and I. We also each have to read the datasheet and safety sheet of Tarbender: the epoxy we will use. It's mean stuff so you have to prepare by reading the manual.
Preparing the workspace
The Idea is to think ahead. When the epoxy is mixed you have no time to do this. If you keep in mind that you will not be able to touch anything when you are with the epoxy. This will be on your gloves!
Tarbender
Here is the online safety sheet. And here is the product page of of Tarbender by Smooth-On, the company that sells it.
Technical:
Tarbender is a liquid epoxy. It can be poured or brushed over material and provides a strong, high gloss coating.
Curing:
It cures at room temperature and takes about 16 hours.Application:
It can be used on wood, plaster, concrete, foam, fabrics, paper, etc. You can add colorants to the epoxy. You can use 90% Isopropyl alcohol to remove Tarbender from surfaces. Tarbender consists of two parts. Tarbender Part A (SDS No. 1050A) and Part B (SDS No. 1050B). Pot life is 45 minutes. Cure time is 16 hours. Shore hardness is 75D.Safety:
Avoid breathing the fumes. Wearing a NIOSH approved respirator is recommended. Use only in a well ventilated area. We will use gloves, lab coat, safety glasses and respirator.Warnings from the safety sheet:
this product may cause skin irritation and eye irritation. If you need to see a doctor, bring the container with the label. Don't breath it in. Don't eat, drink or smoke while handling the product. Wash your hands thoroughly with soap after use. If on fire use water fog, dry chemical or carbon dioxide to put it out.Environmental advise:
don't let Tarbender enter the sewer or open waterways.User instructions:
Mixing ratio: 2A:1B. No scale is needed. Shake both the parts in their container. Stir for two minutes. Pour over in a new cup and stir for two minutes again. The mixing cups should consist of plastic, metal or wax coated paper. If you mix a lot of Tarbender at the same time, pot life may reduce and it may become too hot to handle. Wash hands thoroughly after use. Store at room termperature. Table of how much volume you need per square centimer (source)Cutting cloth and pouring
Nathan and I each made a couple of test pieces. I used jute because that is what I want to use in my individual assignment. I cut out four layers of jute. The second sample is part of an old blue blouse. Two external layers of the blue cloth and in the middle two pieces of jute to give it some volume. Third piece is two layers of black sturdy linen from an old trouser. Lastly, I filled my mold from last week with Tarbender because I am curious what an object of pure epoxy looks like. Harm also wanted to know what pure Tarbender looked like but he had forgot to make a test poor himself. So he asked us to fill one for him. He had taped a piece of 1mm plastic on the workbench of which he had cut out a square. He asked us to fill that with tarbender. This turned out to not be not the smartest of setups. Throughout the day I kept touch the square accidently, dropping stuff on it, etc. A workbench is not a good place for an open mold. After preparing the cloth we mixed the Tarbender as per the instructions. Two minutes of stirring, pour into another cup and stir two minutes again.
We made 150ml of mixed solution. Each having 75ml to work with. I started out with the jute but it soaked up a lot of epoxy so I ended up having to make another 75ml. With a pot life of 45 minutes this was not a problem. I had prepared two planks and a bunch of glue clamps to serve as pressure mechanisms. I attached cling foil to the planks with tape and then smeared vaseline on the cling foil. The purpose of the cling foil is to keep the epoxy from attaching to the mold. The purpose of the vaseline is to keep the epoxy from sticking to the cling foil. One mistake I made is that I had wanted to place all the epoxied cloth samples between just two planks even though the samples have different thickness. The four layers of jute are much thicker than two layers of linnen. I only figured this out when I was laying the epoxied mess on the planks. Having my gloved hands full of epoxy I did not want to go search for extra planks and glue clamps and mess with the cling foil and vaseline again, so I just placed all samples in the same pressing mechanism. How that will come out we will see after the curing. I also poured pure epoxy in my mold from last week. This time I did not forget to add release agent. In one half of the mold I added to strings of jute to see how that comes out. Lastly, I poured Harm's ridiculous square.
Now wait 16 hours.
Flexibility test
Starting left and then going down each row: 2 layer jute, 2 layers heavy black linnen, white linnen two layers, glass fiber two layers, pure epoxy, 4 layer jute, 2 layer blue cloth.
Taking out the samples:
We did a crude flexibility test
Two layers of thin white linnen is pretty flexible.
Two layers of glass fiber is pretty flexible.
Two layers of thin blue cloth is very flexible.
Four layers of jute is very strong and will only bend minimally.
Two layers of thick linen ... breaks!
No it doesn't. Something has gone wrong with the pouring. Apparently there was not enough epoxy in the middle of the piece. The two halves can not be broken any further. Pretty flexible.
Pure epoxy bends a little.