Grantee Research Project Results

Final Report: Replacements for PVC and PE Water Pipes

EPA Contract Number: 68HE0D18C0016
Title: Replacements for PVC and PE Water Pipes
Investigators: Chamsaz, Dr. Elaheh Anna
Small Business: METSS Corporation
EPA Contact: Packard, Benjamin H
Phase: I
Project Period: October 1, 2018 through March 31, 2019
Project Amount: $98,524
RFA: Small Business Innovation Research (SBIR) - Phase I (2018) RFA Text |  Recipients Lists
Research Category: SBIR - Water , Small Business Innovation Research (SBIR)

Description:

The objective of EPA topic 1C program was to develop and demonstrate a novel approach for producing a new type of plastic that can be used to support the production of waterpipes for drinking water applications. In the Phase I program, METSS covalently bonded derivatives of the antioxidant BHT to a polypropylene backbone. This modified polypropylene masterbatch material can be compounded into a final product that meets the regulatory requirements for waterpipe materials, without the disadvantages associated with current pipe materials. The proposed solution will readily integrate into the existing manufacturing base and commercial supply chain for plastic waterpipes.

METSS approached the replacement of the water pipes made from PVC and PE by addressing the polymer permeability and chemical migration issues while providing and maintaining the following benefits: (1) source materials and intermediate products will not be toxic; (2) chemical additives will not leach into the drinking water; (3) the materials will not cause issues related to odor or taste; (4) the material will be stable under exposure to environmental factors (including UV, oxidation, and hydrolysis) and temperature extremes; and (5) the materials will be recyclable.

Summary/Accomplishments (Outputs/Outcomes):

Polypropylene (PP) was selected as the base resin for the novel pipe material because it is a versatile thermoplastic material with inherently good physical properties and chemical resistance, including (1) low relative density, (2) innate chemical, hydrolytic, and thermal resistance, and (3) low permeation to moisture and oxygen. As a relatively inexpensive polymer, PP is widely used in many commercial applications and is compatible with many processing techniques, including injection molding, blow molding, extrusion, cast film, and thermoforming. It is also compatible with water pipe installation methods and joining techniques, and it is easily recycled. Importantly, PP is commonly used in the food industry, and prior research and published literature support the use of polypropylene for water piping.

METSS evaluated multiple methods to prepare BHT derivatives with an active site that enables physical bonding to the PP backbone as a pendant group. Since BHT modification did not involve changes to the functional groups that provide antioxidant activity or integration into polymer main chains, the ability of the BHT to act as a stabilizing agent was preserved. Importantly, since the modified antioxidant with a reactive group adheres covalently to the polymer's backbone, the additive's ability to diffuse/desorb from the polymer into the drinking water was eliminated.

Conclusions:

The Phase I program successfully demonstrated a novel approach for producing a new type of plastic material that can be used to support the production of waterpipes for drinking water applications. METSS created a chemically stable masterbatch material that can be compounded into a final product to reduce permeability and impart antioxidant functionality without leaching. The source materials and masterbatch materials were not toxic. After challenging the masterbatch materials with chemical and thermal stresses, no sign of chemical leaching was observed. The material showed increased resistance to thermal oxidation and degradation when exposed to high heat and oxygen. Like polyethylene, polypropylene is easy to recycle as thermoplastic materials, and there are substantial markets for its recycled materials.

While the SBIR effort was focused on developing a modified PP for waterpipe applications, the proposed approach has broad applicability for incorporating antioxidants and other additives into polymer systems. The proposed technology can be utilized in virtually any plastic product that requires an elevated degree of resistance to degradation, whether due to aging or environmental exposure, especially for polymers used in sensitive applications. Development of a practical solution to improve water pipes will result in significant commercial benefits, including better water quality, cold and hot water operational capability, and recyclability. Real-world applications include plastic tubes and pipes, food packaging, and beverage containers.