Tech Talk Blog

Recent headlines tell us that everything from our kitchen cutting boards, Tupperware and soda fountain delivery tubing are infected with everything from fecal matter to salmonella. There are solutions available thanks to new polymer technology using antimicrobial additives and surface treatments. Many polymers are now available with silver ions which help to effectively inhibit the potential growth of bacteria, yeast and fungi on the polymer surface. By using unique zeolite carriers with silver ions, a counter force to the sodium ions present in moisture  interrupt respiration, reproduction and metabolism of destructive microbes. TriStar offers several polymer solutions now in molding and extrusion resins to dramatically reduce the potential of microbial growth in your products. Browse through our Video Learning Center for even more information.

The dynamics of wetting are described below:

Spreading = A – ( B+ C )

Where:

• A = surface energy of solid (given below)
• B = surface tension of liquid
• C = surface energy of solid-liquid interface

If Spreading is:

• Negative. Then, liquid will bead up.
• Zero. Then, liquid will spread.
• Positive. Then, liquid will spread.

If the material surface energy is relatively low, then the coating will not flow well and fisheyes, pinholes, gaps, or air bubbles will form. If the material surface energy is too high, then the paint, ink, or coating may bleed or be difficult to control. Therefore, the surface tension of the liquid and the surface energy of the material must be matched for the application.

Don’t just listen though – take a look! Visit our Video Learning Center for an in-depth look.

The molecular forces and chemical bonding are important to understand the physical properties the bulk polymer exhibits. The covalent bonding in a polymer system is one of the strongest and significant forces and is often referred as primary bonding. A list of common covalent bonds and the energy associated with the bonds are listed below:

This list shows the dissociation (bond breaking) energy to predict which bonds will break first when a polymer is overheated or modified by plasma or UV. For example, the carbon (C) chlorine (Cl) bond will dissociate before a C-H bond in a PVC polymer.

Secondary bonding forces are also important as they can affect the material’s physical properties, such as surface tension, viscosity, friction, volatility, and solubility. The secondary forces are as follows:

Blends are the physical blend of polymers. Unlike a copolymer that is chemically mixed, polymer blends are mixed before or during molding operations. Yet, polymer blends can be just as useful and cost effective as copolymers or terpolymers. The physical property of a blend is determined by the physical properties of each ingredient and miscibility. If the compounds are miscible, the mixture will remain uniformly blended (homogenous). If the compounds are not miscible, the each mixture will separate into its respective phase. It would be here that the physical properties of the material would be compromised if the adhesion between the compounds is poor. Fortunately, if two immiscible polymer need to be blended, an additive can be used or a polymer can be grafted to one of the originals.

If you want to know a little bit more, watch our Plastics Technology 101 Seminar and other videos in our Video Learning Center.

A polymer is a very large molecule (macromolecule) composed of many small repeating molecular units (monomer). Polymers are formed from atoms that are capable of multiple covalent bonds. Such as the carbon atoms in ethylene CH2=CH2 molecule. Molecules with this type of bonding are said to be unsaturated. These compounds tend to keep this structure yet will readily react (under heat and pressure) to form more stable single bond structures; they will form a saturated compound. For example, ethylene will react to form polyethylene [-CH2-CH2-’]n . The [n] signifies the number of repeating units in the polymer backbone. This number can be from 1000 to ~300,000 units. The polyethylene material will have different properties based on the number of repeating ethylene monomer units.

From this simple compound, substitutions can be made to provide different properties. When one substitution is made the compound is a vinyl monomer. When two substitutions are made the compound is a vinylidene monomer. As more substitutions are made other compounds are created.

To recap, polymers are formed through chemical reactions under heat and pressure. Additives, ingredients, and conditions are designed to control how the polymer is formed and desired properties. This process is called polymerization. Polymerizing one kind of monomer will create a homopolymer as in polyethylene or polypropylene.

Visit TriStar to learn even more about polymers – or if you have a specific questions, Ask The Experts right away!