Polymers and Composites

Monomers and Polymers Monomers are small molecules that build up polymers A polymer is a large complex ________ built from monomers joined together in a repeating pattern by a chemical bond. A polymer’s chemical properties depend on the monomers that make them up. Ex. of polymers: protein in meat, plastics, polyester, nylon.

Polymer Arrangements

Carbon Carbon is found in almost everything, living and non-living, and can form large and complex molecules. Most polymers depend on carbon for their structure. __________ is the most common element attached to carbon (hydrocarbons). Carbon has 2 unique properties that allow it to form so many compounds: 1. Carbon can form ___ bonds 2. Carbon can bond in a straight chain, branched chain, or rings.

Natural Polymers Ex: Cellulose is a flexible and strong polymer found in fruits and vegetables. It is also found in the cell walls of plants When in long chains, humans cannot digest it When it is connected in shorter chains, as in starches, humans can digest it Other examples: Silk, wool, proteins in the body

Synthetic Polymers Synthetic polymers are inexpensive to make, strong, and last a long time. They do not break down into simpler substances like ______________ do. As a result, plastics build up in the environment in the form of trash. A way to reduce the amount of trash is through _____________. Recycled plastics can be used to make bottles, clothing and many other substances. Ex: polystyrene, nylon, kevlar

Polymer Shapes

Composites A composite is made of two or more different polymers and has different properties than the polymers it is made of. Chemists combined the useful properties of some polymers to create a material that is better than the individual polymers.

Examples Ex 1: Wood is a natural composite: Long polymers of cellulose held together by a polymer called lignin. Cellulose is flexible and lignin by itself is brittle, but together they create a strong tree trunk Ex 2: Fiberglass is a composite made of glass and plastic (found in boat hulls, and can also be used for insulation and reinforcement).

Metals and Alloys An alloy is a mixture of two or more elements where at least one of them is a metal. Alloys are used much more than pure metals because they are stronger and less likely to react with air or water. Ex: Bronze is an alloy of Cu and Sn. It was the 1st alloy created. Brass – Cu, Zn. Dental amalgam (fillings) - Hg, Ag, Sn, Cu, Zn. Sterling silver - Ag, Cu

Comparing metals and alloys Most metals are reactive. Fe rusts when exposed to air. Stainless steel, which is an alloy of Fe, C, Ni, Cr, doesn’t react with air. Steel with a higher content of C is stiffer and less malleable Alloys are ____________ than metals Making and Using Alloys Many alloys are made by melting metals and mixing them together in specific amounts. Some are made by mixing together metal powders and heating them at high pressures.

Ceramics Ceramics are crystalline solids that resist moisture, do not conduct electricity, and can withstand temperatures that would cause metals to melt. Ceramics are used in many devices as insulators Clay consists of water Si, Al, O. when it is heated, the water dries up and the particles stick together and make a hard solid. When they are glazed they do not absorb water. Even though they break easily, they are very useful (store food; roofing tiles).

Polymer Lab Prep Cross-linking: substances that link together long polymer chains through chemical bonds. http://pslc.ws/macrog/xlink.htm

Glass Glass is an amorphous solid that is clear, can be molded into many shapes and colors, and can’t be penetrated by liquids. It was originally made by heating a mixture of calcium, sodium and _______ to very high temperatures. Modern glass is made from a combination of calcium, sodium and silica ____, Glass can have different materials added to it to make it more useful Replacing sodium with lead oxide can make useful lenses Adding boron oxide can make glass more heat resistant

Optical Fibers Optical fiber is a threadlike piece of glass or plastic that transmits light. When talking on the phone, your voice is converted to light signals that travel through the fiber. It then is converted into electronic signals which are converted to sound at the other end.

6. What is a composite, and how do polymers relate to composites?   7. What is wood made up of, and why is wood considered a composite? 8. What makes synthetic polymers–such as plastic–beneficial? 9. What is a major problem associated with synthetic polymers? 10. What is an approach that can be taken to solve this problem associated with polymers? 11. What is an alloy, and how are alloys made? 12. Why are alloys used more commonly than pure metals?

Section 1 (pages 118-125) 1. What is a monomer? 2. What is a polymer? 3. What element do most polymers depend on for their structure, and what other element is most commonly bonded to this element? 4. Give two reasons why carbon is found in so many different compounds. 5. Using page 121 in your Chemical Building Blocks textbook, list three different types of polymers and explain what these polymers are used for.