UNT polymer engineers partner with industry leader to develop advanced coatings technology

Building contractors across the country may owe certain thanks to UNT plastics engineers over the next few years.  Regents Professor of materials science and engineering Dr. Witold Brostow and his team at the Laboratory of Advanced Polymers and Optimized Materials(LAPOM) just completed their first contract with McKinney, TX based Encore Wire Corporation.

The LAPOM team is working to develop wire coating materials with better adhesion, scratch-resistance, and reduced friction during installation — major goals for the Encore project.

“In our lab we pride ourselves on solving problems for industry,” Dr. Brostow said.  “It is the company that seeks out innovation that comes out ahead in the end.  This is a nationwide company, a strong one, and they want to improve their technology.  That is where we come in.”

LAPOM is a UNT lab that specializes in developing polymer-based materials, components and coatings.  The lab also performs characterization tests, consultancy, and trouble-shooting in the areas of manufacturing, processing, and analysis of materials and processes using computer modeling. LAPOM’s complement of services is well suited to answer Encore’s inquiries.

Polymer sample immediately after mixing;the sample is quite ductile.  It will be cooled and pressed to make testable samples.                                                     -Photo courtesy of LAPOM

“We thought it would be advantageous for us to work with some local universities and do some collaborative research,” Encore Director of Research Ray Pahler said.  “I approached different schools, and quite frankly UNT was very responsive.  Dr. Brostow was instrumental in helping us develop a program.  We’ve been working on it this year, and now we’re seeing results.”

Encore Wire’s website boasts “success as big as Texas and a future as bright as Times Square,” and a 192-acre campus that includes management offices, manufacturing facilities, and the Encore Techlab, a $13 million LEED Platinum Certified research and development lab featuring six different labs with state-of-the-art equipment used to compound materials and perform rigorous tests.

Brostow has taken about 50 students on tours of the Encore facility this Fall and the response was so positive that he is planning similar tours in the future.  It is key to the success of students as future engineers to actually see the industry side of operations, he said.  The recent collaboration of LAPOM with Encore Wire offers a great deal more than a tour of the business.

Wire Coating Technology

Encore manufactures copper and aluminum wires with a two-layer coating that provides safety for handlers and weather resistance for the metal wires inside.  LAPOM is an ideal place to develop the coating technology because both the internal PVC and external nylon-based coating layers are polymers. The current project involves replacing the external nylon layer with a low-friction polymer that would allow the wires to slide more easily through the steel conduits that carry the wires throughout buildings.

Recent work by LAPOM included thorough characterization of coatings currently used by Encore and the development of several dozen new materials.  The samples were extensively tested for adhesion, scratch-resistance, friction performance, and heat degradation, among other parameters, using advanced instruments at LAPOM and the UNT Center for Advanced Research Technology (CART).

Samples are wear-tested for up to 5000 cycles in the CART Tribometer.      – photo by Amelia Jaycen

The collaboration that began in March has involved Texas Academy of Math and Science (TAMS), undergraduates, graduate students, some of whom are international students on internship in the College of Engineering, and physicists, chemists, mechanical engineers, and materials engineers — a typical range of expertise for a LAPOM project.

Austin Richards, materials science and engineering senior and President of the UNT chapter of the Society of Plastics Engineers is the Project Manager for the Encore collaboration.  Richards does the majority of his work at the UNT lab but also visits Encore’s Techlab every few weeks.

“We do the preliminary small-scale testing here, and Encore applies what we do on a much larger scale,” Richards said.  “For example, they perform tests actually pulling the wires through conduits with 90 degree bends.”

Electron microscopic images of material tested for heat degradation.     -Photo courtesy of LAPOM

Extensive series of testing are performed at the Encore Wire Techlab in order for wires to receiveUnderwriters Laboratory (UL) rating, including crush tests, flame tests, resistance to sunlight, exposure to water, heat shock, oil and gas immersion, and tens more.  The most successful materials developed by Brostow’s LAPOM team will be subjected to a number of such further tests at Encore Wire over the course of the next year.

“One thing that has come out of the work we’ve been doing with LAPOM is that they’ve been able to measure the adhesion between the outer jacket and the inner insulation layer on the wire,” Ray Pahler of Encore said.  “We really haven’t been able to measure that before.”

Dr. Joshua Wahrmund, LAPOM lab manager, explains scratch-testing.                    – Photo by Julie West

For these critical adhesion tests, LAPOM is assisted by a Swiss machine that performs microscratch and microindentation.  LAPOM is one of a handful of labs in the U.S. to own the Micro-Combi Tester, which is able to apply as many as 15 scratches in the same groove of the material and take careful measurements noting when the inner layer of coating is reached.  Scratches in the material made by a diamond indenter tip can be applied at steady loads or linearly increasing loads, and photographs of the tests are compiled into a panoramic image.

Microscopic image of groove created by linearly increasing load. 
– Image courtesy of LAPOM

Future testing of coating material candidates at LAPOM will include samples that are rolled into a thin film similar to the thickness of the actual wire coatings and sample sets containing different percentages of carbon black to see how the coloring additive affects the performance of materials.

“This is the first time in my life I’ve been excited to come to work,” Richards said.  “I’m fully involved in these projects and find myself wanting to be at LAPOM.  A semester ago I would have said that I am not going to graduate school.  But now, getting an advanced degree is definitely part of my future.”

Polymer samples with carbon black pieces in different concentrations photo by Julie West

An Industry Seeking Green

As a member of the Renewable Bioproducts research cluster at UNT, Brostow explores green solutions for industry products.  Sustainable investigations made on behalf of Encore Wire are no exception.  Encore’s recycling of metal wire, PVC insulation, and wire jackets is one means to this goal. Reducing reliance on petroleum is another.

“Polymeric materials are primarily made from petroleum, which means we significantly depend on imports from other countries,” Brostow said.  “We are researching a variety of ceramic based mineral fillers that could potentially replace part of the petroleum-based polymers.  These environmentally benign materials offer the advantage of developing cheap yet effective products that are less dependent on petroleum.”

Other anticipated objectives include further testing of coloring additives, development of coatings with increased hydrophobicity (water deterrence), and replacement of the inner PVC coating layer in response to recent findings by the EPA that show PVC to be an un-safe building material that releases toxic chlorine gas in the event of fire.

LAPOM’s work with Encore Wire is a partnership that has advantages for both players, and the company is also seeking collaborations with the UNT College of Business in the area of logistical assessments.

—  Amelia Jaycen, Publications Assistant, Office of Research and Economic Development

Originally published at

Encore wire under the MicroCombi scratch-test microscope at LAPOM.                – photo by Amelia Jaycen

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