Waterborne Chlorinated and Non-Chlorinated Modified Polyolefin TPO Roof Coatings Adhesion Promoters.

Abstract

Chlorinated and Non-chlorinated modified polyolefins are traditionally used in applications where adhesion to low surface energy materials like polypropylene and TPO is needed.

They are primarily used in solvent-borne applications to adhere to these difficult to bond to substrates. VOC limitations are getting stricter as the years go by, forcing formulators to switch from solvent borne to waterborne or high solids solutions.

This is especially true for roofing applications. This paper will cover how you can use waterborne chlorinated and waterborne non-chlorinated modified polyolefin adhesion promoters to make waterborne roof coatings adhere to virgin and aged TPO.

Introduction

Chlorinated modified polyolefins (CMPOs) and Non-chlorinated modified polyolefins are primarily used in solvent-based systems as primers or additives for coatings that need to adhere to low surface energy plastic substrates like polypropylene, polyethylene, PET, and many others. In Figure 1, the basic structure of an NCMPO is shown, and in Figure 2, the basic structure of a CMPO is shown. The polyolefin backbone on the polymer allows for better wetting and surface bonding to polyolefin surfaces because of Van der Waals forces. The modification of the chlorine on the polymer allows for potential reactions with reactive groups in resins and for interactions and bonding with inorganic substrates. The structure that the NCMPOs and the CMPOs have allow you to bond to polyolefin and non-polyolefin substrates.

Experimental and Testing

In this study, one NCMPO emulsions and one CMPO emulsion was evaluated. The physical properties of the emulsions are in Table 1. The study consisted of developing a roof coating basecoat that could adhere to virgin and aged TPO, meeting the minimum adhesion requirements of ASTM D6083.

In this application, the formulation of Table 2 was made by using a dental mixer. The formulations were optimized by evaluating different resins, and types of calcium carbonate. The formulation was modified by adding 2.9 and 8.6 percent of NCMPO1 and CMPO1. The formulations were applied to virgin, aged TPO, and UV aged TPO to make 180° peels. The dry and wet adhesion was evaluated following ASTM C794. The peels were evaluated after one week of curing. They were also evaluated after one week of curing and one week of water submersion. The tensile properties of the coatings were also evaluated by measuring the Shore A hardness, elastic modulus, % elongation, and tensile strength. The elastic modulus % elongation, and tensile strength was tested by using a universal tensile tester by following ASTM D2370. The low temperature flexibility following ASTM D522 was also evaluated.

Results and Discussions

In this application, it is necessary to have a peel strength greater than or equal to 2pli (pounds per linear inch). Figure 3 shows how you can achieve and surpass the minimum 2pli with the addition of 2.9% or 8.6% of NCMPO1 or CMPO1 with respect of the dry peels on the different TPO substrates evaluated.

Regarding the wet peels, Figure 4 shows that the only additive that can achieve the minimum 2 pli is 8.6% CMPO1.

The physical properties of the coatings are showcased in Figure 5. The physical properties of the base coat are not greatly affected by the addition of NCMPO1 or CMPO2 at the loading levels used. All coatings evaluated also passed the low temperature flexibility at -10°C.