Foam gnomes are fun and cool to watch happen... But, there are rules to follow.

Transcription

1 FOAM GNOMES Polyurethane foam was created during WW II to insulate refrigerators and airplanes. It replaced balsa wood and because this polymer is cheaper, easier to shape, man-made and abundant, it has been used in many practical applications. We find it in furniture cushions, shoe soles, insulating materials, adhesives, flotation devices, cellular scaffolding for bone regeneration, and acoustical vibration control. And that is the short list. The objective of this experiment is to create polyurethane foam from the reaction of polyester polyol with an isocyanate. SO... Lets get some information out to you to help you better understand what is happening and why.

2 Foam gnomes are fun and cool to watch happen... But, there are rules to follow.

3 Objectives: 1. The student will know that matter is composed of atoms and has chemical and physical properties. Students are expected to recognize that chemical formulas are used to identify substances and determine the number of atoms of each element in chemical formulas containing subscripts. 2. The student will investigate how evidence of chemical reactions indicate that new substances with different properties are formed when they observe a color change, change of state, evolution of gas, and release of heat as indicators that a chemical reaction occurred. Time line is minutes You are expected to clean-up VERY well.

4 Warnings and advisements to be taken seriously!!! PLEASE follow your directions to avoid accidents or trouble.

5 Safety and Clean up concerns: 1. Solution A contains a *polyether polyol, a **tertiary amine and a ***silicone surfactant *Polyether polyols are water soluble polymers with a molecular weight between 200 and 14,000. Relate it to your GAK with a more serious attitude!! **The easiest way to think of an amine is to look at them as a near relative of ammonia. In a tertiary amine, all of the hydrogens in the ammonia molecule have been replaced by a hydrocarbon group. ***This is a solultion that contains silicone (which does not mix with water) and keeps it in an emulsion (basically mixed with water) for the purpose of achieving a reaction required.

6 So---what is going on in simple terms? Polyol is a long chain of carbon atoms with a hydrogen and oxygen pair at the each end. This hydrogen-oxygen pair, called a hydroxyl group, is always busy looking for other atoms to connect with. It is like a necklace with hooks at both ends.

7 For Solution A ---Do not touch the chemical until the reaction is done! WHY? The chemical can stick to your fingers and does not come off!. You will know when the reaction is done because it will stop growing upwards. After the upward movement stops....wait 30 seconds before touching it. Solution B *polyfunctional isocyanate *These are **electrophiles that act with and towards amines. They can have quite a reaction when put together---as you will see. **These are a positively charged item that is very attracted to electrons (remember electrons have a negative charge).

8 Here is a polyfunctional isocyanate: Many of these are cyclic in nature. That means that the R represents a circle or ring of 6 carbon atoms. So the chemical fingers coming off the rings are looking to hook up. The more fingers on the rings, the more rigid the resulting foam. More connections will make for less flexibility of the material.

9 So What is happening exactly? We mixed the two chemicals together and foam is produced. It comes because it is a cushiony, colloidal suspension that is formed when gas molecules are trapped in a sticky liquid. In this case, your stirring made the gas become trapped in the sticky liquid. When you stir, the fingers off the rings of carbons start linking together to form a liquid web which catches the gas that is being produced. It is like a 3-D web to catch bubbles. The foam then hardens in the air. This type of foam has lots of cross-linking, that is why it is so hard whereas your GAK was squishy and fun to play with.

10 Please remember: We have the air vents going and you are NOT going to touch the solutions. This is for safety reasons. Also, those who will bring the solutions to the table will have a glove on as well as the person stirring the solution will also wear a glove. All gloves should be put back into the box in the center of the table to be used by the next student/s. Thank you ahead of time for taking care of this. Your table area, where the stirring occurs, will be covered in newspapers. If you are careful, you will not have any mess at all. That is your goal. If the wet foam spills on a desk top, it creates a sticky coating that hardens very quickly and then must be scraped off with a knife we DO Not WANT TO DO THAT!!!! Do we?!?!?!?!?!

11 Is this lab fun?!?!?!? Yes and it is a bit entertaining and will allow all you students to easily recognize indicators of a chemical reaction. You will see the following: A change of color A change in state And the evolution of heat as two liquids are mixed in a cup and produce a huge growth of foam Lots of fun and OOOHS! and AAAHSS!

12 What do I do? 1. Read your instruction sheet carefully. Each person reads one number out loud while the rest of the group reads along silently---but! All should be paying complete attention. There is a lab sheet to fill out. Talk and agree and fill out together. You will need some helps for your lab sheet so here is the help... Opacity means can I see through it? If I can, I call it transparent, if I cannot see through the liquid, I call it opaque. Remember that some dark colors can still be seen through. State means solid, liquid, or gas Color what color do you see? Your two colors are basically honey yellow and maple brown.

13 OKEE-DOKIE, Are we ready to begin? 1. Spread out your newspapers on the center of the table. 2. Each person take a turn picking up items according to your job. Do not forget to use your glove on the hand that carries the chemicals. 3. Read all instructions out loud and clear for those listening and reading along. 4. Observe closely. 5. Be sure all is cleaned up 6. Be certain that your paperwork is completely filled out. Hand all group papers in together.