The radiation curing components are applied to scratch-resistant hard coatings

Hard scratch-resistant acrylic components are used in a wide range of plastic coatings, from electronics, communications, semiconductors and data storage to optics, automotive, aerospace and medical devices. Due to its versatility and variety, consumption of various plastics has been increasing over time and now includes materials such as ethylene glycol phenylphate (PET), methyl acrylates (PMMA) and polycarbonate (PC).
This article describes a range of ultraviolet curing products with high-level energy, including 100% solid low-polymer and water-based polyurethane dispersions, which can be formulated with excellent scratch, wear and weather resistance to support their application in outdoor coatings.
Materials Assessment
Senior Officer Energy Polyurethane
investigated adipose polyurethane acrylic (UA) with a polyester main chain structure. We have long believed that lysants of these chemical structures exhibit excellent durability when exposed to harsh environments, whether under naturally occurring conditions or artificially accelerated aging. Higher crosslink density usually increases the hardness and scratch resistance of the coating. Therefore, each molecule selected by the Institute has 6 to 9 acrylic ernogenic groups in each molecule, for this study, these dispersions are identified as CN9006, CN9026, CN9025 and CN9013.
water-based low-
data are given for series of UV-cured polyurethane dispersions, comparing their physical properties because their properties are related to wear resistance. These dispersions are identified as PRO12874, CN9500, and CN9501.
first part of the study focused on
a range of high-level energy adipose polyurethanes to evaluate the performance of protective coatings on various substrates. Table 1 provides a brief description of the lymer and its properties.
, the performance of pure lysates was quantified by the tabered shadow test, using the Tyber grinding wheel, which assessed the effect of surface wear resistance on changes in transparent coating shadows. Figure 1 provides a description of the application conditions and performance results.
because these lymers vary greatly in viscosity, acetone is added to each lysogene to control the film thickness well. Add a light trigger (PI) to allow UV curing. Each mixture is coated to a transparent substrate, the solvent is removed and the UV curing is carried out, resulting in a dry film thickness of 75 microns. Epoxy acrylates (CN120)
low-level polypolymers for comparison.
to test light transmission before and after the Tebel test. The decrease in the percentage of light transmission is reported as the fog shadow difference. It turns out that epoxy acrylates (CN120) are significantly less resistant to wear than low-polypolymers in the acrylic polyurethane (UA) series. This result is due in part to the higher official energy of acrylic polyurethane, which leads to an improvement in surface curing. However, better flexibility of acrylic polyurethane materials is also a factor.
other experiments to quantify the hardness characteristics of various lymers, as seen in Table 2. The glass transition temperature (Tg) of the curing film is a fairly good indicator of hardness. In general, the higher the glassing temperature, the higher the surface hardness of the paint film. However, high hardness does not always mean good wear resistance. Data resistant to wire cotton prove this effect. Lymers with lower Tg values passed the wire cotton test, while those with higher Tg values failed the test.
The Taber test, expressed in terms of mass loss
Given that the Tabered fog test quantifies scratch and wear resistance to the surface of the coating or lacquer film, the Teber wear test measures overall performance. This test is usually carried out on a thicker coating using a more abrasive Taber grinding wheel (replacing CS10 with CS17). Lymers are tested in formulations that contain low-level monomers to better control paint film thickness and improve extension performance. Figure 2 summarizes the basic formula, the Teuber test conditions for each lymer formula, and the results of the Tyber mass loss. These tests were carried out on a 50 micron thick curing film applied to the aluminum plate.
found that epoxy acrylic low-polypolymers were less wear-resistant, with a mass loss of 140 mg after 500 Tebel cycles. In contrast, acrylic polyurethane low-polymers actually show a fairly low mass loss. It is also worth noting that the highest official energy lyside (CN9013) has poor results compared to those with a high official energy of 6. This means that high hardness and high crosslink density are not always good for wear resistance, as the elasticity and extension of the curing film can also affect wear resistance. In other words, wear resistance is controlled by both hardness and non-brittleness. This concept is also supported by the excellent performance of the CN9026, which is chemically designed to enhance flexibility.
weather resistance test
In order for the coating to function effectively as a protective barrier, the coating must be extremely scratch- and wear-resistant and non-degradable when exposed to harsh environmental conditions. When low-level energy is used to enhance scratch resistance, the coating may crack, especially in the thicker part of the paint film. The UA lysate is applied to the substrate with film thickness of 5, 10 and 15 microns, respectively, and the cured model is tested for laboratory accelerated aging in the QUV® test box. QuV test conditions vary, including a period of 8 hours of ultraviolet light exposure at 60 degrees C, followed by condensation for 4 hours under dark conditions of 40 degrees C. The test case contains UVA 340 lamps. The spectral output of the UVA 340 lamp ranges from 300 to 400 nanometers, with a center of 340 nanometers. This lamp can most closely replicate the emission spectrum of sunlight. Measure the degree of yellowing and gloss hold of the paint film as a function of time and record the results.
because the tested UA lysum had a fat family structure, no color changes or yellowing increases were detected over time. The gloss of each coating was also measured to record the differences between the lymers. In each case, a decrease in gloss was observed due to a slight crack in the hard coating. The severity of cracking is related to acrylic energy and paint film thickness. The degree of cracking increases when the property's energy level and the thickness of the coating increase. The exception is that the lysum has been modified to have improved flexibility and high acrylic functionality, especially CN9026 and CN9025.
no cracking was observed after the CN9025 property was exposed to 5000h at 5 microns of paint film thickness. Cracking was detected after 1500 hours of exposure at a thickness of 10 microns, and cracking was detected at a thickness of 15 microns at just 700 hours. The CN9026 lysum performed well regardless of the paint film thickness, and no cracking was observed after 5000 hours of exposure to any paint film thickness throughout the test. These results are found in table 3.
acrylic polyurethane hard coating overview
The curing film obtained by adipose polyurethanes with high acrylic properties has excellent wear resistance. Higher official energy results in a higher crosslink density, which is ideal in general. However, the disadvantage of increased cross-link density is reduced wear resistance and increased fine cracking during aging exposure tests, especially when the coating film thickness exceeds 5 microns. These limitations can be controlled by changing the main chain structure to increase its flexibility, or by adding low-performance acrylics to the formulation to reduce crosslink density. These adjustments improve the flexibility of the paint film and make it more stretchable, resulting in better wear resistance to the curing film and reducing the possibility of fine cracking during weather-resistant experiments.
important feature of the
shielding coating of the
substrate is its ability to prevent degradation of the end product on the coating coating. To test this function, a scratch-resistant hard coating is applied to a polyester (PET) film and exposed to QUV for 2000 hours. As noted, the light stabilizer is added to the hard coating formulation. The difference between the test and the previous aging test data is quV exposure, not the degree of yellowing (YI). This is a measure of the total color change. The readings are taken from a 250 micron thick PET film coated and uncoated hard coating. In this way, PET degradation can be monitored and compared with painted PET films to prove the effectiveness of the coating in protecting pet substrates. The basic formulation, curing and construction parameters are described in detail in Table 4.
test results
in this test, painted PET samples performed better, regardless of how much or what type of light stabilizer was added. The maximum value of the QUV of all painted PET samples is approximately 2.0 after 2000 hours of exposure. In contrast, the exposure of the unpainted PET sample was 4.5 hours after 1300 hours and 8.5 hours after exposure 2000 hours, which meant significant color change. Detailed results can be found in Figure 3.
also monitored the gloss hold rate on the same PET film (painted and unpainted) as a function of QUV exposure time. The effect of light stabilizers can be observed from Figure 4.
THE PET film, which was not painted with a photostabilizer, maintained 70% of the original gloss value, while the PET film, coated with a formulation containing a photostabilizer, retained 86% of its initial gloss value after exposure. Finally, the unpainted PET film performs very poorly, maintaining only 3% of the initial gloss value.
Substrate Protection
During QUV exposure for 2000 hours, the light transmission performance of unpainted PET and painted-added and unobstructed amine-like photostabilizer (HALS) PET was tested with a UV/visible spectrometer as a function of time. The test results (Figure 5) show that UV-cured coating formulations have the ability to prevent degradation of PET substrates. Protection is enhanced by the addition of light stabilizers.
results of substrate
certain grades of PET degrade when exposed to heat, light, and moisture for long periods of time. Properly made coatings reduce degradation and provide a wear-resistant protective layer for PET. The addition of HALS and light absorbents further enhances protection.
Ultraviolet-cured polyurethane dispersion hard coating
water-based low-polyester testing
in a series of construction-related tests, a series of UV-PUD-cured polyurethane dispersions (UV-PUD) resistance and wear resistance were evaluated. Table 5 lists the ncom of the water-like UV-PUD to be measured and its corresponding liquid properties. Many UV-PUD materials on the market typically have a solid content of 35% or less, and a typical viscosity greater than 20cps. It should be noted that the tested lysum has an average solid content of 40% and a viscosity range of 8 to 15cps. Higher solid content and lower viscosity provide more formulation flexibility for the formulation of industrial coatings.
Application performance of water-based UV-cured polyurethane dispersions
each UV-cured polyurethane dispersion low-polymer is made with standard industrial additives for good film-forming properties, and various application parameters are tested, including flexibility, hardness, wear resistance, contamination resistance, water resistance and weather resistance. Adjust the solid content of each lysant to 35% to provide a consistent baseline.
each of the UV-cured polyurethane dispersions is applied to the substrate with a wet film thickness of 150 microns, resulting in a dry film thickness of about 50 microns. Use a laboratory drying procedure (30 minutes at room temperature, then 30 minutes at 60 degrees C) to ensure that all water is removed before UV curing. Drying conditions may vary in production conditions, depending on the equipment used, but it is usually sufficient for 10 minutes in a temperature range of 50 to 60 degrees C.
6 shows the experimental method for each UV-cured polyurethane dispersion. Each performance tested, the relative level of terminal usage performance, is also shown. All lymers have good properties in contamination, water and solvent resistance tests. We found that the controlled UV-cured polyurethane dispersion samples (a widely used commercially available UV-cured polyurethane dispersion product) were not flexible and QUV-resistant, but the performance was still within acceptable ranges in terms of hardness and wear resistance.
excellent water resistance with ultraviolet cured polyurethane dispersions. For example, when exposed directly to hot water, no curing paint film will turn white. It is also worth noting that quLV accelerated aging test results are comparable to those of adipose polyurethanes.
surface scratch test
Given that CN9501 (PUD3) shows good wear resistance, contamination resistance and excellent moisture resistance, it was selected to compare surface scratch resistance with competitive control samples.
7 describes the surface scratch test method used. Measure the gloss hold and increase the load from 100g to 500g at each increment of 100g. At each load, the sample is worn 50 cycles with a white friction pad (3M Scully brand). The wear resistance of the control material is very poor, and its gloss decrease is more significant than that of the CN9501 sample. The luster of this polyurethane dispersion remained at a relatively high level throughout the test.
wear resistance
The Tebel wear test assesses the overall wear resistance of the coating, given that the surface scratch test provides information about the surface performance of the curing film. The CN9501 and the controlled UV-cured polyurethane dispersions were tested for Thabo wear resistance using the CS17 Tyber grinding wheel, measuring mass loss every 200 cycles (up to 1000 cycles). The grinding medium used in the test is more aggressive than the friction pads used in the surface scratch test, which makes the test more rigorous. Based on the results of the mass loss shown in Figure 8, the CN9501 is indeed more resistant to wear than the control material.
Overview
Scratch and Wear Resistance
- Adipose polyurethane curing film with high-level acrylic energy has excellent wear resistance.
high-level energy of the high-ranking officials will get a high crosslink density, thus increasing the hardness. However, depending on the flexibility of the coating, high-level energy may cause a fine crack in the curing film during weather resistance testing, especially if the coating film thickness exceeds 5 microns.
two ways to improve the flexibility and extension of the coating film