Non-Isocyanate Polymer Design and Coating Development

WP-2315

Objective

The objective of this project is to develop a high performing exterior topcoat without the use of diisocyanate compounds. Our team has chosen to mitigate technical risks by investigating alternative reaction chemistries that produce polyurethanes without using diisocyanates and coating formulations that utilize resin systems other than polyurethanes. The technical plan addresses performance requirements contained in military topcoat specifications such as MIL‐DTL‐53039D, MILDTL‐64159B and MIL‐PRF‐85285D. Upon successful completion of the effort, results of performance and chemical agent resistance testing will have driven the down‐selection of a single coating chemistry and the development of a prototype formulation which meets one or more of the relevant specifications.

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Technical Approach

The development effort will leverage the team’s experience and capabilities to synthesize polymers, formulate coatings, and characterize performance of three basic coating chemistries which have the promise to replace traditional urethane coatings used in Army, Navy and Air Force fleet maintenance activities. Development efforts for these three coating chemistries will be centered on novel polymer design capabilities such as PPG’s high‐throughput synthesis tools, statistical design principles during formulation, and testing against relevant controls. Partner organizations will validate preliminary findings and provide guidance on coating characteristics most important to the final users. A brief description of these candidate coating system chemistries follows:

Polysiloxane Based Systems: Polysiloxane coatings result from the hydrolysis and condensation of alkoxy silane‐functional polymers. PPG has developed semi‐gloss coatings based on this chemistry and researchers at the U.S. Army Research Laboratory (ARL) are formulating camouflage chemical agent resistant coatings based on two component siloxane systems, also called hybrid epoxy‐siloxane coatings. Initial hybrid epoxy‐silane formulations have demonstrated exceptional protective properties due to their chemical structure which combines the durability and hardness of epoxy coatings and notably improves on the gloss and color retention of urethane type coatings.  

Polyuretdione‐Based Systems: The polyuretdione/hydroxyl reaction results in a urethane linkage although no free isocyanates are used. Accordingly, coating performance properties are similar to conventional urethanes. Recent catalyst studies conducted by PPG have identified options which provide cure at room temperature but improvements are needed in polymer design to reduce volatile organic compound (VOC) levels.

Cyclic Carbonate‐Amine Based Systems: Cyclic carbonates are another example of non‐isocyanate coatings producing a polyurethane linkage during crosslinking. Cyclic carbonates can be formed from the reaction of epoxides with carbon dioxide (CO2) using a catalyst under slight pressure and temperature. Feasibility of room‐temperature cure has been demonstrated by PPG through appropriate catalyst selection or the addition of co‐reactants.

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Benefits

Free isocyanates are known sensitizers. Handlers of isocyanates can become sensitized at any time, displaying various degrees of reaction to the chemical. The U.S. Army Public Health Command published Technical Guide 144 entitled “Guidelines for Controlling Health Hazards in Painting Operations” which identifies hexamethylene diisocyanate (HDI) as the most common isocyanate monomer found in aliphatic polyurethane paint and the ingredient which has generated the majority of concern. It is estimated that the US military consumes over 2,000,000 gallons of urethane coatings each year. Assuming only 0.1% HDI by weight, this amounts to over 20,000 pounds of HDI. Topcoats formulated without diisocyanates would protect human health and the environment by reducing exposure of painters to these hazardous materials. Productivity of coating operations will be maintained or improved through the use of the alternative coating solutions. (Anticipated Project Completion - 2016)

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Points of Contact

Principal Investigator

Dr. Ljiljana Maksimovic

PPG Industries, Inc.

Phone: 412-492-5622

Fax: 412-492-5696

Program Manager

Weapons Systems and Platforms

SERDP and ESTCP

Document Types

  • Project Overview - Brief project summary with links to related documents and points of contact.
  • Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
  • Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
  • Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
  • Guidance - Instructional information on technical topics such as protocols and user’s guides.
  • Workshop Report - Summary of workshop discussion and findings.
  • Multimedia - On demand videos, animations, and webcasts highlighting featured initiatives or technologies.
  • Model/Software - Computer programs and applications available for download.
  • Database - Digitally organized collection of data available to search and access.