Page 32 - Plastcs News August 2017

FEATurES
FEATurES

INTRODUCTION

Waterborne clear coatings have been developed to meet without SB1 pretreatment. Furthermore, data also
those requirements and address the concerns of high VoC suggested that by increasing the coating thickness, the
that are normally associated to conventional solvent- light fastness of Southern Pine can also be improved to
based coatings [1]. Most customer use waterborne clear some degrees but not as effective as other methods such as
wood coatings to protect wood materials. However, increasing the use level of light stabilizers in the clear coat
sunlight and UV radiation can penetrate coating into or having the pre-treatment of Southern Pine prior to the
wood surface to cause yellowing. The yellowness is application of clear coat [9]. Lignin is a complex organic
included coating and lignin. Wood is composed of lignin, polymers. The functional group contains hydroxyl groups
cellulose and hemicelluloses. Lignin, when exposed to (-oH). The different solubility parameter of co-solvents
the sunlight, can easily be degraded [2-6]. The routed mixed with SB-1 and then pretreated on wood surface.
of photodegradation of lignin [7-8] is shown in Figure 1. How performance with different solubility parameter?
Eversorb AQ-1 is waterborne light stabilizer. Eversorb SB1, The softwoods contain 25–35% lignin and hardwoods
designed for wood pretreatments. Test data confirmed contain 18–25% lignin [10]. Theory, SB-1 pre-treatment is
that by increasing the concentration of AQ-1 in the clear significant to protect softwoods.
top coat can effectively protect Southern Pine from UV
light degradation. However, when Southern Pine was is The subject of this paper is to demonstrate the use of 5
pre-treated with SB-1 prior to the application of the same types of wood. Softwoods (Southern Pine and Douglas fir)
clear top coat, the weatherability is better than the one and hardwoods (Cedar, Southern beech and African Teak)
are test in this model.

Fig. 1. Route d of photodegradation of lignin

EXPERIMENT
The three model formulations used in this study were an acrylic based waterborne clear coating, wood pretreatments
and co-solvents. Their detail compositions are shown in Table 1, Table 2 and Table 3. The 5 varied Woods were chosen
in the region are shown in Figure 2. Design of Experiment (DoE) was used to design test runs as well as to analyze test
data. DoE technique allows us to validate the data.

Plastics News | August 2017 32
March 2017 | Plastics News
23 43 April 2015 Plastics News
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