Monomers
The individual parts of a polymer.
Functional Groups
In order to create a monomer to form a polymer to become a plastic, a functional group must be added to give the possible plastic its characteristics. Functional groups are distinctive arrangements of groups of atoms that impart characteristic chemical properties to the molecules that contain them.
Hydroxyl
Hydroxyl groups make up alcohols. When a hydroxyl group is attached to a carbon backbone, the entire molecule turns into alcohol. They are a polar, hydrophillic group that can dissovle in water.
Nomenclature of alcohols can be found in Food Colorings & Additives.
-OH
Carboxylic acid
Carboxylic acid groups are single units that naturally occur in vinegar and cheese. Carboxylic groups are hydrophilic or water-loving. This carboxyl group ionizes to release hydrogen ions (H+) from the COOH group resulting in the negatively charged COO– group. This contributes to the hydrophilic nature of whatever molecule on which it is found.
A carboxylic acid is a functional group found in amino acids. Amino acids are the monomers that the body uses to build proteins. The combination of a carboxylic acid and an amine will create the structure of amino acid.
-COOH
Amine
Amines are a part of an amino acid molecule. Amino acids are the monomers that our bodies build proteins.
-NH2
Amino Acids
Amino acids are the monomers that our bodies build proteins. Each amino acid molecule contains an amine functional group and a carboxylic acid functional group. Twenty different amino acids occur naturally and each differing with one of the groups bound to the central carbon atom, represented by R.
Amide
Amides are…
-CONH2
Ester
Esters are…
-COOC-
Monomers
Monomers are individual, small molecules used to synthesize polymers. Each monomer is analogous to a link in a chain. Monomers add together to form a long chain of polymer units.
Polymers
Chemically bonded monomers that create plastics.
Polymers
A polymer is a molecule of very high molecular weight that is composed of many, much smaller parts joined together through chemical bonding. Polymers help to create materials with ideal properties. Polymers can be formed from one monomer or from a combination of two or more different monomers.
Condensation Polymerization
Polymerization is the linking of monomers through covalent bonds. In a condensation polymer reaction, condensation polymers are formed with the release of small molecules.
Addition Polymerization
In addition polymers, such as nylon, form as their individual, unconnected monomers join together to form a polymeric chain. This chain is similar to the linking of people standing next to each other to form a human chain by holding hands. The monomers in this polymerization add to the growing chain in such a way that the polymer contains all atoms of the monomer.
Plastics
A synthetic material made for everyday use.
Plastics
Polymers have varying strengths based on the arrangements of molecules. Polymers contain crystalline and amorphous regions. Crystalline regions are regions in a polymer where molecules may have an orderly, repeating pattern. The long molecules are arranged neatly and tightly in a regular pattern. Amorphous regions are regions where long molecules are found in a random, disordered arrangement and are packed loosely. The crystalline regions impart strength and abrasion resistance, while amorphous regions impart flexibility. This range of properties allows for a range of applications.
Plasticizers
Plasticizers are compounds that are added in small amounts to polymers to make them softer and more pliable. They function by fitting in between the large polymer molecules and disrupting the regular packing of the molecules.
Polyethylene
Polyethylene is a polymer of ethylene. Below is the structural formula for polyethylene. The ethylene monomer represented on the right displays the ability for monomers to add to one another to form long chains of n units. n specifies the number of molecules reacted.
As each ethylene monomer adds, a new C—C bond forms, and there is chain growth. This process repeats multiple times. Towards the end of this process, the ends of two polymer chains may join and stop growth, or the supply of monomers is exhausted and growth is stopped.
Long chains can have differences causing different properties. Differences in the physical properties of polymers can be because of the extent of the branching within the polymer chain.
Polyethylene is formed by condensation polymerization. The molecules form by releasing a small water molecule.
Low Density
Low-density polyethylene (LDPE), such as plastic grocery bags, are long, irregular, and tangled polyethylene chains. The properties of low-density polyethylene can be varied but most LDPE has soft/wax-like properties found in food wrap and soft coatings.
High Density
High-density polyethylene is polyethylene that is a highly ordered molecular structure with slightly greater density, rigidity, strength, and higher melting point. HDPE is commonly used and seen in plastic bottles, toys, stiff bags, and heavy-duty pipes.
Vinyl
Vinyl is a tough, flexible, smooth, shiny, and inexpensive plastic. Through additional polymerization, vinyl can be turned into polyvinyl chloride (PVC). The properties of vinyl can be varied. If not softened with a plasticizer, the plastic will be rigid. Without pigment, the plastic is clear and shiny and is resistant to most chemicals, including oils, acids, and bases. Due to this plastic’s rigidness, vinyl is used in materials such as plumbing pipes, house siding, and charge cards (ex. credit cards). When softened with plasticizers, vinyl can be used in garden hoses, waterproof boots, shower curtains, and IV tubing.
Polystyrene
Polystyrene is hard plastic with little flexibility. This plastic has two forms, “crystal” and “expandable.” Polystyrene in its “crystal” form is transparent, sparkling, and somewhat brittle. “Crystal” polystyrene is used in the creation of food wrap, CD cases, and transparent cups. In its “expandable” form it is lightweight and foamy. “Expandable” polystyrene is used in foam cups, insulated containers, food packaging trays, egg cartons, and packaging peanuts. Both forms are rigid and will degrade into many organic solvents.
Polypropylene
Polypropylene is an opaque, very tough plastic with good weatherability. This plastic has a high melting point and is resistant to oils. The use of polypropylene varies from bottle caps and food containers to carpeting, casual furniture, and luggage.
Polyethylene Terephthalate
Polyethylene terephthalate, also known as a form of polyester, is a transparent, strong, shatter-resistant plastic. It is impervious to acids and atmospheric gases but is the most costly plastic listed. Polyethylene terephthalate is used for soft-drink bottles, clear food containers, beverage glasses, fleece fabrics, carpet yarns, and fiber-fill insulation.
Ethylene glycol
Terephthalic acid
Similarities of Plastics
Polyethylene (high & low Density), polyvinyl chloride, polystyrene, polypropylene, and polypropylene terephthalate are the big common polymers. All of these plastics are solids that can be mixed with color, and are insoluble in water, though some degrade or soften in the presence of hydrocarbons, fats, and oils. Alongside this, all of these plastics are thermoplastic polymers, with heat they can be melted and reshaped.
Thermoplastics
Thermoplastics are plastics that respond to heating and cooling well. These plastics mimic fats. Thermoplastics include plastics called thermosets. These plastics are soft enough to be molded when they are first prepared, but permanently solidify upon heating. Reheating thermosets causes the decomposition of the plastic. Common products that are considered thermosets are Bakelite, found in cooking handles and electrical molding, and epoxy resin, used for fiberboard and plywood.
Elastomers
Elastomers are substances that stretch easily and return readily to their original shape and size.
