Study on the preparation and performance of fluorocarbon powder coatings for building aluminum profiles

Abstract:
In order to develop FEVE (Fluoroolefin-Vinyl Ether Co-polymer) fluorocarbon powder coatings for building aluminum profiles with good suitability and cost-effectiveness, the effects of fluorine resins, different types of isocyanates and pigment content on THE performance of FEVE-type fluorocarbon coatings were analyzed. Comparing the aging resistance of different types of weather-resistant powder coatings, it is considered that acrylic and ultra-weather-resistant hydroxy resins are more suitable for modified fluorine resins, and the performance of these two types of resin-modified fluorine resins is further compared. The results showed that FEVE fluorocarbon powder coating was prepared with acrylic modified fluorine resin and self-enclosed isocyanate BF-1540, and the coating performance was excellent and cost-effective
China
when the pigment amount was 22.5%.
aluminum alloy is widely used in construction, transportation, aerospace and other fields because of its smooth surface beauty, good mechanical strength, easy processing and molding, easy recycling and so on. According to its use can be divided into aluminum single board, aluminum plastic plate, aluminum ceiling and aluminum alloy profiles. Aluminum alloy as a building material is mainly used in outdoor aluminum doors and windows, building exterior decorative materials, glass curtain wall support system. In recent years, with the progress of surface treatment technology and people's living beautification requirements, in the all-aluminum home, all-aluminum sun room and other aspects of a variety of imitation wood, imitation stone aluminum profiles have been rapid development and application.
in order to improve the corrosion resistance and aging resistance of aluminum profiles, and improve the surface decoration effect of aluminum alloy building materials, it is usually necessary to process its surface. Reference to the national standard GB/T5237-2008, China's current construction aluminum profile surface treatment methods are: anode oxidation, electrophoresis spraying, powder spraying, fluorocarbon coating spraying. Fluorocarbon coatings have been widely used in various landmark buildings, high-end residential buildings and office buildings because of their excellent weather resistance and salt spray corrosion resistance. However, with the government and society pay more and more attention to environmental improvement, some local governments began to levy VOC sewage charges, and even some places began to do not allow the use of coatings containing high VOC, fluorocarbon powder coatings compared with fluorocarbon coatings, its production, coating process can avoid VOC emissions, so it is necessary to develop fluorocarbon powder coatings suitable for the construction aluminum industry to gradually replace solvent-based fluorocarbon coatings.
At present, there are two main categories of fluorocarbon powder coatings for building aluminum profiles, one is the thermoplastic fluorocarbon powder coatings based on PVDF (polyfluoroethylene) resins, and the other is the thermocarbon powder coatings based on FFEVE (fluoroolefin-vinyl ether co-polymer) resins and their curing agents. PVDF fluorocarbon powder coating currently has three main shortcomings: First, the industry has not yet found a simple process, environmental protection, low cost, easy to industrial production methods; Therefore, PVDF fluorocarbon powder coatings in the aluminum profile industry to promote the application of a certain degree of restrictions. And thermoocurilive FEVE fluorocarbon powder coating not only has similar chemical resistance and weather resistance to PVDF, but also its production preparation and coating process mature, similar to ordinary powder coating, coating gloss can also be designed as needed, because of its good wetting of pigments, color selection is relatively easy, easy to promote the application in the field of architectural aluminum profiles. Therefore, this paper has developed a good applicability, cost-effective architectural aluminum profile with FEVE-type fluorocarbon powder coating, and studied its coating properties.
1 Experimental part
1.1 Main raw materials
fluorine resin A: domestic; fluorine resin B: import; ultra-weather-resistant hydroxy resin C: otema; acrylic resin D: Guangzhou Co-ed resin (commercially available); ultra-weather-resistant pyrethroid e:DSM; isocyanate triglycerides (TGIC): industrial grade Niutang Chemical; Leveling agent, degassing agent: South China Sea flattery; Brightener: Huahui; Closed isocyanate B-1530, self-enclosed isocyanate BF-1540: Degusai; Other additives: commercially available; DDDA: Import; Titanium White Powder: DuPont Chemical; Black430, Yellow10c272: Schott Pigments, USA; PVDF Fluorocarbon Coatings: AkzoNobel Coatings.
1.2 The main equipment for the experiment
GSJ-30E extruder, ACM-05F grinder: Yantai City Sanli Machinery and Equipment Co., Ltd. CQ-SJ5 electrostectrectrectrectrative spraying equipment: Shenzhen Chengcheng Xin Technology Co., Ltd.
1.3 FEVE fluorocarbon powder coatings are
The basic formulation of FEVE fluorocarbon powder coatings is shown in Table 1.
the formula designed according to Table 1, the raw materials are evenly mixed, and then by the extruder melting out and cooling the broken into pieces of material, and then the sheet material through the ACM grinder crushed, to produce powder coating.
1.4 coating preparation
using standard aluminum plate, surface non-chromium passivation treatment, electrostitive spray conditions for static voltage 60 to 80kV, powder delivery 1kg/cm2, sprayed model in a 200 degrees C oven baking 20min, remove cooling to room temperature, one-time spray coating thickness control at 50 to 70 m.
1.5 performance test and the instrument used
test standards and instruments used can be found in Table 2.
2 Results and Discussion
2.1 Pure FEVE Fluorocarbon Powder Coating System
2.1.1 Effect of THE type of FEVE Fluorine Resin on coating performance
According to table 1 basic formula prepared powder coating, compared with the paint film performance prepared with different manufacturers of fluorine resin, the experimental setting of fluorine resin content of 60%, the specific paint and coating performance of Table 3.
analysis table 3 shows that the mechanical properties of the two fluorine resin coating membranes are better, can meet the European building aluminum profile standards Qualicoat III. The chemical corrosion resistance of the two fluorine resins is not very different, but there is a difference in the weather resistance of the two, when the preservation rate drops to 90%, the test time of fluorine resin B is 1000h longer than A. Through the DSC test, 2 kinds of resin made of powder coating glass transformation temperature difference of about 6 degrees C, powder coating glass temperature is lower, powder coating is easier to group, affecting the use, so fluorocarbon A resin preparation powder coating storage stability is relatively poor. Therefore, considering the combination, choose fluorocarbon resin B as the resin used in FEED fluorocarbon powder.
2.1.2 Effect of curing agent type on coating film performance
Due to the characteristics of fluorine resin molecular structure, fluorocarbon coating film mainly depends on the cross-curing of hydroxyl and isocyanate in fluorine resin, different isocyanate curing agent - NCO active group content and molecular structure will be different, so different curing agents will inevitably affect the performance of the coating film. This experiment compared the effects of 2 commonly used different types of curing agents on fluorocarbon coating film, of which B-1530 belongs to hexylamide-closed isocyanate and BF-1540 belongs to self-enclosed isocyanate. According to Table 1 reference formula for the preparation of fluorocarbon powder coatings, wherein, the amount of fluorine resin B is 60%, the dosage of isocyanate curing agent is 15%, the dosage of other ingredients is 35%, the experimental results are seen in Table 4.
As can be known from Table 4, the surface of the coating with curing agent B-1530 is slightly lower than that of the coating surface, but there is no significant difference between weather resistance, impact resistance and salt atom resistance, indicating that different curing agents also have an effect on the final performance of the coating, BF-1540 curing agent is more suitable for curing fluorine resin B.
2.1.3 Effect of pigment dosing on coating film performance
The amount of pigment does not affect the performance of the coating, considering that the current GB/T5237.4-2017 standard stipulates that the total quality score of resin and curing agent in powder should not be less than 60%.
Thus, this study began experimental exploration from 31% of pigment dosing, analyzing and comparing the effects of pigment dosing on the coating performance of FEVE fluorocarbon powder coatings, the formula is shown in Table 5, and the coating performance is shown in Table 6.
can be known from Table 6, when the amount of paint filler gradually increased, the coating film gloss gradually decreased, the surface flatness became worse, impact resistance, adhesion did not differ significantly. Mainly because the fluorine resin on the pigment wetting difference, increase the amount of pigment filler, the dispersion effect of the various components of the system becomes worse, resulting in the coating baking melt level is worse, the surface of the coating film is uneven, the gloss is reduced. Therefore, in the design of pure FEVE fluorocarbon powder formulation, the amount of pigment filling is best not more than 24%, otherwise the appearance and gloss of the coating film has a greater impact.
above, the experimental preparation of pure FEVE powder coating weather resistance is good, can fully meet the European building aluminum profile standards Qualicoat III. class powder coating requirements, weather resistance is much better than the current construction aluminum profile with ultra-weather-resistant polyester powder. However, in the process of practical application promotion, because the raw material cost of pure FEVE fluorocarbon powder is very high, the price is basically 300 to 400 yuan / kg, greatly limiting the large-scale application of fluorocarbon powder. Therefore, in order to control the cost of FEVF powder coating, this study uses other types of good weather-resistant resins to modifie FEVE, in order to obtain cost-effective fluorocarbon powder coating.
2.2 Modified FEVE fluorocarbon powder coating system
2.2.1 Comparison of coating aging performance with different weather-resistant building aluminum profiles
Among them, epoxy resin weather resistance is the worst, do not compare. And the domestic market weather-resistant powder coatings are mainly ultra-weather-resistant polyester powder coatings, ultra-weather-resistant polyurethane powder coatings, acrylic powder coatings 3 types. Therefore, the experiment selected ultra-weather-resistant pyride resin E, ultra-weather-resistant hydroxy resin C, acrylic resin D and the corresponding curing agent TGIC, B1530, DDDA, and then added powder coating general aid (leveling agent, degassing agent, brightener) and pigment filler mix uniformly, through extrusion, crushing, abrasion preparation of the above three types of powder coatings. Compared with pure FEVE fluorocarbon powder coating, PVDF fluorocarbon paint, ultra-weather-resistant polyester powder coating, ultra-weather-resistant polyurethane powder coating and acrylic powder coating QUV-B accelerated aging performance, this test mainly compared the photon preservation results, the results are shown in Figure 1.
figure 1 shows that after aging, ultra-weather-resistant polyester powder coatings, ultra-weather-resistant polyurethane powder coatings, acrylic powder coatings in 600h, 900h, 1500h, respectively, after the preservation rate dropped to 50%. FeVE fluorocarbon powder coating, PVDF fluorocarbon paint after 4000h aging test, the preservation rate is still more than 90%.
according to the above different types of powder coating weather resistance test data know: in addition to fluorocarbon resin, weather resistance is better acrylic resin and ultra-weather-resistant polyurethane resin. The advantages of using polyurethane composite fluorocarbon resin are: (1) the de-enclosed temperature of the closed polyocyanate curing agent is high, its curing temperature is the same as fluorocarbon, there is sufficient time leveling before cross-curing, so the coating film leveling is good, so it can improve the surface leveling of fluorocarbon powder; The advantages of choosing acrylic composite fluorocarbon resin are: (1) acrylic adhesion is good, and FEVE composite can directly improve the adhesion of the coating film to the substrate; However, acrylic resin rigidity, direct compounding will lead to poor impact resistance of the coating film, but can be solved by other methods, the resulting powder coating performance is excellent. In this study, ultra-weather-resistant polyurethane and acrylic resins were selected to prepare modified FEVE fluorocarbon powder coatings.
2.2.2 Comparison of the performance of polyurethane and acrylic modified FEED fluorocarbon powder coatings
This study used ultra-weather-resistant hydroxy resins C and acrylic resins D and fluorine resins to change by quality ratio of 1:1, comparing the properties of polyurethane modified and acrylic modified 2 modified fluorocarbon powder coatings. The basic formulation and coating performance test results of polyurethane and acrylic modified FEVE fluorocarbon powder coatings are shown in Tables 7 and 8, respectively.
From Table 8, it can be known that the mechanical properties, appearance and cost-effectiveness of polyurethane modified FEVE or acrylic modified FEVE fluorocarbon powder are better than pure FEVE, and the weather resistance of acrylic modified FEVE fluorocarbon powder is significantly better than that of polyurethane modified FEVE fluorocarbon powder, slightly worse than pure FEVE fluorocarbon powder coating, far better than ultra-resistant urethane powder.
3 Conclusion
In summary, the fluorine resin B and self-enclosed isocyanate BF-1540 were selected by experimental comparison to prepare FEVE fluorocarbon powder, and the pigment content was proved to have a great influence on the appearance performance of the coating, and the pure FEVE fluorocarbon powder with excellent performance was obtained when the pigment content was about 24%. At the same time, through the introduction of acrylic resin and fluorine resin in accordance with the quality ratio of 1:1 compound has obtained a modified FEVE fluorocarbon powder coating, its mechanical performance is significantly better than pure FEVE fluorocarbon powder, aging performance is close to pure FEVE fluorocarbon powder, raw material cost is significantly lower than pure FEVE fluorocarbon powder coating. Therefore, the modified FEVE fluorocarbon powder can meet the requirements of fluorocarbon powder in the field of aluminum construction, and can greatly accelerate the application of fluorocarbon powder in the field of aluminum profiles in construction.
Wen/Wei Yufu, Liu Fei,
Guangdong Huajiang Powder Technology Co.,