On the present market, the colorization methods of window profiles have full base color, color co-extrusion, surface lamination and paint-spraying technics. Each technique is briefly introduced as follows:
Full base color of UPVC windoor profiles
The method is the main method for colorization of plastic profiles in the early stage. It mixes coloring pigments into PVC profile powder for co-extrusion to get full-colored plastic profiles.
Compared to the other methods, it has several advantages: small equipment investment, low technical content and fast production. However, it is not suitable for the small batch and variable production orders of small plastic profile processing factories. Because the deformation temperature of PVC profiles is usually lower and the full base color profiles, especially dark -colored profiles will absorb more solar radiation, the overall surface temperature of the profile is high, and even close to the maximum service temperature of the profile, which is easy to cause aging and deformation of the profile, thus shortening the service life of the colored profiles. In addition, if it uses general dye coloring, because the UV resistance of the dye is very poor, the profile outside will seriously fade in 2 years and there will be quality defects, so the full base color method will gradually withdraw from the market.
Color co-extrusion of PVC window profiles
It is one of the most popular methods of colorization technology applied in the world. It extrudes a layer of color film in the process of extruding PVC profiles. A co-extruder is necessary and the mold design and fabricating is also more complex. Different profiles need different moulds, and different colors of PVC profiles need different color master batch. The investment is huge, and substandard products are harder to recycle. Currently, the composites co-extruded with PVC can be PVC, colored methyl methacrylate (PM MA) or ASA. Using homogenous PVC, durability can not be solved. Using PMMA, the durability is improved, but the durability is still not ideal. It’s easy to delaminate with PVC, and low temperature impact resistance is not good. Using ASA, its durability is improved and generally can meet the requirements of outdoor use for 10 years. However, the coating is soft, and the colored surface is easy to scratch during storage and processing.
Lamination of UPVC window profiles
It is more applied in European plastic profiles and especially German technology is quite mature. The method is to put premade color plastic laminating into a special laminating machine, after gluing, heating mechanical laminating, and then to paste the color film on the surface of the PVC profile. Generally available laminating materials are PVC and PVDF materials. Pasting PVC film, the durability of profiles can not be fundamentally solved. Pasting PVDF film, the durability can meet the requirements but due to the complex construction technology and equipment, the rate of finished products is not high. The higher cost of the main raw materials and the complexity of the laminating machine equipment result in higher costs. When the laminated plastic profiles are processed, once the surface lamination is damaged, it need to complement color, so it’s quite troublesome.
Paint-spraying of UPVC profiles
It is developed in China in recent years. It can be sprayed on line in the process of profile production, or sprayed on the surface or the white base plastic steel profile in a special spraying factory. At present, the latter method is more adopted at home and abroad. At present, there are high-performance single-component acrylic coating, two-component polyurethane coating, water-based polyurethane coating and fluorocarbon coating solidified at room temperature.
Single component acrylic coating is easy to apply, and has good adhesion, but the outdoor weather resistance is not up to 10 years. Among them, acrylic polyurethane coating has better weather resistance, and automobile topcoat is sprayed with it. Waterborne polyurethane plastic steel coating has the advantage of convenient construction, but it is not suitable for humid climate conditions. In contrast, the normal temperature curing fluorocarbon coating has good performances as well as convenient construction, and so it is most potential.
From the above introduction, we can obviously feel that the processing methods (except spraying) of color plastic profiles on the market have the disadvantages of large investment, inconvenient color change, high technical requirements and poor weather resistance. To adapt to the requirements of personalized color plastic profiles, further research and improvement are needed. A good colorization method of colored plastic profiles should have the following characteristics:
(1) Economy - It can be accepted by most customers
(2) Excellent performance - the performance after colorization shall meet the requirements for long-term use
(3) High decorativeness - color decorative effect shall be able to withstand the competition of similar substitutes (to reach the decoration level of aluminum alloy profiles)
(4) Production - It can meet the timely and stable production capacity under various batch requirements.
The following focuses on the characteristics of color co-extruded profiles that is popular on the current market:
1. Co-extrusion materials:
(1) ASA—PVC co-extrusion
(2) Modified PMMA—PVC co-extrusion
(3) PVC—PVC co-extrusion
2. Material characteristics:
(1) ASA-PVC co-extrusion:ASA and PVC have good compatibility, and ASA has good flow performance, flexibility, outdoor weather resistance, good impact resistance, rich color, and stable process. ASA: Acrylonitrile-styrene-acrylate copolymer.
(2) Modified PMMA-PVC co-extrusion: the flexibility of the modified PMMA material is greatly improved compared with that before. The flow performance is good. The color is rich. The process is stable. The outdoor weather resistance is good. The surface brittleness is reduced. It is easy to obtain a better surface finish, and it is not easy to scratch.
(3) PVC-PVC co-extrusion:the flow performance of PVC is obviously inferior to that of ASA and PMMA, so the surface PVC formula shall consider both good flow performance and weather resistance. If color co-extrusion is adopted, it is suitable for light color system. The darker the color, the worse the weather resistance.