The new version of GB/T 1741-2020, "Determination of Fungus Resistance of Paint Films", is stricter than the 2007 version in approximately 14 aspects, mainly in terms of sample aging treatment, test fungi, and nutrient culture medium. This article compares and analyzes the new and old standards and introduces a mildew-proof solution that meets the new standard and green label requirements.

GB/T 1741-2020 Improving the mildew resistance of paint films

The new version of the standard, "Determination Method for Mildew Resistance of Paint Films", GB/T 1741-2020, will be officially implemented on October 1, 2021. It puts forward higher requirements for the mildew resistance performance of products. Mildew prevention measures that met the original standard may fail to pass the new standard's testing. Upgrading and replacing paint products and using highly efficient and environmentally friendly mildew-proofing agents are imperative.

I. Key Differences Between the Old and New Versions

The key differences between the old and new versions of the standard that affect the mildew resistance results are listed in Table 1 below.

Table 1. Key Differences Between the Old and New Versions of GB/T 1741

Key Differences	2020 Version	2007 Version
Substrate	Mainly aluminum plates	Mostly mineral building materials
Test Panel Aging Method	According to GB/T 23987-2009 8.2.1 Requirements Aged for 100h, Irradiance: 0.83w.m -2 .nm -1	24h flushing with running tap water
Test Fungi	Alternaria alternata	Aureobasidium pullulans
Nutrient Culture Medium	Containing sucrose	Without sucrose

II. Comparison of Mildew Resistance Test Results of the Old and New Standards

Paint products with a mildew resistance level of 0 according to GB/T 1741-2007 for 28/56 days showed a level 3 after 28 days and level 4 after 56 days according to the 2020 version. Test data is shown in Table 2, and sample images are shown in Figures 1-4.

This shows that products with a very high mildew resistance level according to the original standard have a much lower mildew resistance level according to the new standard.

Table 2. Different Results of 28/56-Day Tests Using the Old and New Standards

Number of Mildew Growth According to 2007 Version Data

28-Day Area (%)			56-Day Area (%)
Ⅰ	Ⅱ	Ⅲ	Ⅰ	Ⅱ	Ⅲ
0	0	0	0	0	0

Number of Mildew Growth According to 2020 Version Data

28-Day Area (%)			56-Day Area (%)
Ⅰ	Ⅱ	Ⅲ	Ⅰ	Ⅱ	Ⅲ
50	55	30	60	65	35

 

Figure 1. GB/T 1741-2007, Mildew Resistance Test 28 Days

 

Figure 2. GB/T 1741-2020, Mildew Resistance Test 28 Days

 

Figure 3. GB/T 1741-2007, Mildew Resistance Test 56 Days

 

Figure 4. GB/T 1741-2020, Mildew Resistance Test 56 Days

 

III. Mildew Prevention Solution Upgrade

3.1 Mildew-proofing agents for the new standard should have:

• UV stability, high temperature and humidity stability

• High efficiency and cost-effectiveness

• Compliance with GB/T 35602-2017 "Green Product Evaluation Paints" regarding the types and limits of biocides, such as the prohibition of BCM, and the limitation of OIT and DCOIT to ≤500mg/kg, and IPBC and ZnP to ≤1500mg/kg.

3.2 Recommended High-Efficiency and Environmentally Friendly Mildew-Proofing Agents ：

• ACTICIDE® LPC11: A combination product of ZnP and OIT, with very broad-spectrum antibacterial and mildew-proofing properties.

• ACTICIDE® IOG: A combination product of IPBC and OIT, especially suitable for interior and exterior wall coatings, wood protection products, adhesives, fillers, and sealants.

• ACTICIDE® ZPD 1: An aqueous dispersion with ZnP as the active ingredient, effectively preventing the growth of mold and algae on indoor and outdoor coatings.

3.3 Thor New generation AMME ™ Technology dry film mildew-proofing agent:

AMME ™ Advanced Microcarrier Embedding Technology, which can prolong the effective period of mildew-resistant active substances and better resist high temperatures, high alkalinity, rain, and ultraviolet radiation.

Figures 5 and 6 compare the active substance loss curves of traditional dry film mildew-proofing agents and AMME™ mildew-proofing agents. The curve using AMME™ technology is gentler, more UV-resistant, and provides better mildew-proofing effects.

 

Figure 5. Comparison of Mildew-Proofing Agent Active Ingredient Loss Over Time

   

Figure 6. AMME™ products have higher UV stability in coating applications

 

IV. Test data of the recommended mildew-proofing solution under the new standard

Table 3 and Figure 7 show the mold growth resistance data and corresponding sample images of two mildewproof agents tested according to the GB/T 1741-2020 standard. Even at low concentrations, they effectively inhibit mold growth.

Table 3: New Standard Test Results for Different Mildewproof Schemes

Number	Sample Name	28 Mold Growth Area (%)	28 Mildew Resistance Grade
1	Blank	50	3
2	0.5% LPC 11	0	0
3	0.3% ZPD 1	0	0

Figure 7, GB/T 1741-2020, 28-day test

V. Conclusion:

With the implementation of GB/T 1741-2020, selecting environmentally friendly and efficient mildewproof solutions is crucial to meet the increasingly stringent market demands for coating mildew resistance performance and to rapidly achieve updates and iterations of coating products.