Road Marking Paint and Machine Manufacturer
+86-15668659958
The most critical performance indicator of road marking coatings, detailed requirements refer to relevant international standards
The performance of hot-melt road traffic markings is related to the content of organic matter (the total amount of organic matter that can be volatilized at 520 ℃ of muffle furnace), the degradation performance of organic matter (ultraviolet resistance, oxidation resistance and aging resistance), the performance of retroreflective materials (refractive index and quality of glass beads), the performance of retroreflective coatings, and the above impact resistance and bonding strength.
The coating standards are not entirely applicable to global climate applications, and they all specify a unified technical requirement without guaranteeing key performance indicators of materials, such as:
1) No subdivision application has been made for southern regions (mild climate, small temperature difference), northern regions (large temperature difference, distinct winter and summer, extremely low winter temperature), plateau areas, etc. This has resulted in a situation where coatings with the same technical requirements are widely used in the north and south of the world, making it possible for markings to be applicable in the south but not necessarily in the north and high-altitude areas due to climate conditions such as cracking and peeling.
2) Without considering the characteristics of cement pavement and asphalt pavement under different climatic conditions to match the performance of hot melt reflective marking coatings, asphalt pavement belongs to tough pavement. If traffic markings are not adapted to the thermal expansion and contraction of asphalt pavement and the disturbance caused by vehicle driving, it will cause cracking, peeling and other phenomena. (Reference: Asphalt pavement maintenance sealant toughness grade to adapt to different climatic conditions in the north and south of China).
3) There are no corresponding regulations on the technical requirements related to the refractive coating formed by the marking paint and the visibility of the marking during the day. For example, the titanium dioxide content in the coating, currently adding 10 kilograms of titanium dioxide to hot-melt coatings can also achieve a brightness factor of 0.75 or above. With a certain performance of glass beads, the titanium dioxide content directly determines the stability of the inverse reflectance brightness coefficient during the initial and later use of traffic markings.
4) There are no corresponding regulations on the performance of the application on the road, such as impact resistance and coating adhesion strength. The impact resistance and adhesion performance directly reflect the impact force of the coating on the vehicle after forming the marking line, the adhesion of the glass beads (which can be understood as the phenomenon of glass beads not sticking, the marking line being good, and the glass beads falling off), and the adhesion of the coating to the road surface.
5) The application requirements for resin in marking coatings for urban roads and highways have not been refined. For example, some European countries require that highways can use petroleum based resins for coating production, and urban roads need to use rosin resin to improve the anti fouling performance of markings. The United States requires that some renewable resource rosin resin must be used to produce hot-melt coatings. This technical requirement is based on the anti fouling performance of markings in European and American countries, and the detailed working principle can refer to relevant standards and specifications (available for download from the marking coating website).
6) There is no upper limit requirement for the content of calcium carbonate filler in marking paint. Therefore, it also brings opportunities for low-quality marking coatings. A small amount of titanium dioxide can be added to the coating (with a market price of around 23000 yuan/ton). Adding 10 kilograms/ton of coating can achieve the standard brightness factor of 0.75, and the initial reflectivity brightness factor can reach over 150mcd; Adding more calcium titanate powder (market price around 450 yuan/ton), low content titanium dioxide addition cannot cope with color change caused by organic aging in the coating of the marking line and reverse attenuation of the marking line. Compared to European and American standards: European and American standards have detailed requirements for the organic content, titanium dioxide content, glass bead content, and calcium carbonate content of marking coatings.
7) It should belong to the category of GB/T16311: there are no technical requirements for the use level of traffic markings. The use level of markings is directly related to the service life of traffic markings. Different areas and roads with different flow rates can use different levels of traffic reflective markings (refer to the technical requirements of European marking standards, and determine the use level of markings based on the number of wheel presses).
8) The hot melt marking coatings in European and American countries basically do not have the indicator of compressive strength. High compressive strength is suitable for the high temperature climate conditions in the south, but not suitable for the northern climate, as the markings in the north are prone to cracking.
World Application and Quality Control
The United States has national standards for traffic and road marking coatings, and each state has its own local standards based on national standards to adapt to different climate conditions and requirements. Europe has traffic markings and marking paint standards from the European Union, as well as detailed standards from various countries. Most countries in Europe, America, South Korea, and Southeast Asia adopt a quality certification and admission system for traffic markings, as well as a payment model based on the qualified reflectivity coefficient of the markings within the specified service life range in the corresponding bidding documents. Therefore, there is basically no problem of cutting corners in these countries. There is no issue of unqualified reflectance brightness coefficient during use.
Advantages and disadvantages of technical indicators for hot-melt marking coatings on Chinese road surfaces
1) Density: It is similar internationally (with the development of the times, there may be the use of glass beads with medium and high refractive indices for pre mixing coatings in the future (the density of glass beads with medium and high refractive indices is relatively high), and the density of marking coatings may be greater than 2.3).
2) Softening point: 95-125 ℃ (basically equivalent to foreign countries).
3) Appearance: The appearance here is only an evaluation of the coating in the laboratory state. With the advancement of technology, the application of asphalt pavement is diversified (epoxy asphalt pavement, chlorinated rubber asphalt pavement, etc.). The performance of the marking coating varies in different pavement systems, and coating manufacturers need to make corresponding technical formula adjustments. Note: What does a standard board look like!!! The difference is not significant and cannot be defined.
4) Non stick tire time: It does not equal the complete drying time. The non stick tire time here is measured at 23 ℃, so it cannot be completely copied during road marking construction (the road surface temperature determines the drying time, and the drying time will be longer in summer when the road surface temperature is higher). There are two technical requirements for non stick tire time in the United States, and the drying time requirements vary at different temperatures and thicknesses. For 10 ℃ and 32 ℃, please refer to relevant standards for details. The marking paint website can be downloaded.
5) Compressive strength: 280 specifies a unified index, with reflective type ≥ 12Mpa, protruding type 23 ℃ ≥ 12Mpa, and 50 ℃ ≥ 2Mpa. According to the performance of hot-melt marking from 2004 to 2021, this compressive strength is actually not suitable for northern and plateau areas. Traffic markings are prone to cracking or detachment, and high hardness markings can easily cause insufficient adhesion and detachment of surface scattering and pre mixed glass beads. Suggestion: Technical requirements suitable for each region should be developed based on the climate conditions in China, and one indicator cannot dominate the world.
6) Wear resistance: The wear resistance index can indirectly define the wear resistance of the marking coating after it is formed (relative to the service life of the marking), but our coating wear resistance index remains in a state before 2004 (referring to the development of Chinese roads and vehicle ownership in 2004), and only at 200 revolutions per minute, the smooth coating on the coating surface has not worn off (the wear resistance of the smooth coating layer on the coating surface is relatively high). It is no longer applicable to the development of current road conditions. New requirements have been put forward for wear resistance in some areas of the United States, with a lifespan of 8-12 years for hot-melt reflective markings and traffic flow requirements. What is the wear index at 1000 revolutions per minute. Extension: The reference standards for sand abrasion resistance testing of traffic markings are ASTM D 968 and BS 6044 (this experimental method is not referenced in Chinese standards and is generally used to define the wear performance of paint films, such as water-based, solvent based, two-component, etc.)
7) Chromaticity performance: In our country, the testing of chromaticity performance is carried out immediately after the melting of the marking paint forms a coating and is placed at room temperature for measurement. The technical requirement for hot-melt coatings in the United States is to measure the color performance and all other technical indicators of the formed coating after a constant temperature of about 218 ℃ for 4 hours. This difference places high demands on the comprehensive performance of hot melt coatings.
8) Low temperature stability: We require the coating to be applied to a cement board for testing. The thermal expansion and cold plastic reaction of the cement board is very small, which is basically a useless test. The less organic matter in the coating, the easier it is to pass this technical requirement (the worse the coating, the easier it is to pass). Suggestion: Apply the coating onto the asphalt test block for experimental verification.
9) Heating stability: It is only necessary to observe with the eyes that there is no obvious yellowing after 4 hours of high temperature, and this requirement is almost useless. There is no specific quantity for determining the degree of yellowing. Suggestion: Refer to foreign indicators and add the yellow index of white coatings for definition.
7) Chromaticity performance: In our country, the testing of chromaticity performance is carried out immediately after the melting of the marking paint forms a coating and is placed at room temperature for measurement. The technical requirement for hot-melt coatings in the United States is to measure the color performance and all other technical indicators of the formed coating after a constant temperature of about 218 ℃ for 4 hours. This difference places high demands on the comprehensive performance of hot melt coatings.
8) Low temperature stability: We require the coating to be applied to a cement board for testing. The thermal expansion and cold plastic reaction of the cement board is very small, which is basically a useless test. The less organic matter in the coating, the easier it is to pass this technical requirement (the worse the coating, the easier it is to pass). Suggestion: Apply the coating onto the asphalt test block for experimental verification.
9) Heating stability: It is only necessary to observe with the eyes that there is no obvious yellowing after 4 hours of high temperature, and this requirement is almost useless. There is no specific quantity for determining the degree of yellowing. Suggestion: Refer to foreign indicators and add the yellow index of white coatings for definition.
There has always been an unsolvable knot in China’s traffic reflective markings: 1) The paint inspection of the markings is qualified, and the pass rate of highway and national and provincial road supervision spot checks is over 97%.
2) The glass bead testing is qualified, with a pass rate of over 99% for highway and national and provincial road supervision spot checks. Please consider: why does the reflectance brightness coefficient of traffic markings always fail to meet the standards after they are formed?
11) raised doubts about the content of glass beads, and the key points are as follows:
1) The requirements for glass bead content are specified in the coating (the coating standard also mentions that pre mixed beads should meet the technical requirements of GB/T24722), but including inspection, sampling, and supervision spot checks, in addition to testing and measuring the glass bead content, is there any testing of the roundness rate, gradation, and other quality of pre mixed glass beads?
2) At present, all known testing reports for marking coatings only include the glass bead content testing item, and do not include the glass bead roundness rate and glass bead grading. However, the marking coating testing is qualified – that is, the coating is qualified, the surface scattered glass beads are qualified, but the later reversal of the formed marking line is not qualified (because the pre mixed glass beads are not round, the grading is qualified, and the marking coating testing will be qualified, so how can the later reversal of the formed marking line be qualified).
Extended reading: The pattern of standard system revision is gradually breaking down. 1) Glass beads: GB/T24722-2020 “Glass beads for road marking” not only specifies several gradations, but also synchronizes with the EU standard to ensure the anti reflection brightness coefficient of the marking, adding 5.3 technical requirements. The formula method in Appendix B can be used for glass bead gradation control, no longer limiting the size of pre mixed and surface scattered glass beads. This is a considerable standard progress. 2) Speaking of coating performance: Glass beads are refracted in the half moon bay area formed by the settlement of glass beads after the coating is formed by marking lines, so the performance of the coating directly determines the high or low reflectivity brightness coefficient. See the diagram below: Schematic diagram of glass bead retroreflection:
The comprehensive performance of marking coatings also plays a crucial role in determining the anti reflection performance of markings, such as the adhesion of glass beads, the content of titanium dioxide in the coating, the quality of pre mixing and surface scattering of glass beads, and so on. This article aims to conduct a technical analysis and does not evaluate the problem of reverse marking caused by low price bidding.
3) The construction quality of road traffic markings includes the thickness of the markings and the settlement of glass beads. Relevant studies have shown that when RI1.5 glass beads settle by 59% (+5, -0), the reflectance brightness coefficient of the markings is the highest. For other refractive index glass beads, please verify the settlement degree on your own (refer to relevant research report 1978).
The root cause of the non-conforming reverse during the use of the marking line is:
One is the issue of standards: the coating standards leave gaps for cutting corners and the quality of mixed glass beads is not tested. The other is the issue of standards: China’s standard for marking line coatings is relatively simple, resulting in lower comprehensive performance of the coating. The third is the issue of supervision: after the marking line construction is completed, as long as it can be handed over for acceptance, there is no one to track the subsequent quality.
Our company is a professional manufacturer of road hot-melt coatings, road retroreflective measuring instruments, and road marking machines. If you are interested, please feel free to communicate with me via email at any time export@toproadtraffic.com
