How to improve the UV resistance of automotive parts through injection molds?

1, Optimize mold design
Designed in line with the filling quality and molding effect of the plastic melt, the pouring system is a conduit in the injection mold guiding the plastic melt into the mold cavity. The design of the pouring system should aim to evenly and rapidly fill the mold cavity with plastic melt, so avoiding faults such as weld lines and bubbles, so improving the UV resistance of automobile components. Using a multi-point feeding technique, for instance, can let plastic melt enter the mold cavity from several angles at once, therefore lowering the creation of weld marks and increasing the component density and UV resistance. Simultaneously, the gate's position and size should be set properly to sustain a steady flow condition of the plastic melt during the filling process, so preventing local overheating or undercooling generated by unstable flow, which could compromise the UV resistance of the components.
When the plastic melt fills the cavity during the injection molding process, the air within the cavity must be evacuated quickly; else, bubbles or cavities will develop inside the component, therefore lowering its strength and UV resistance. Thus, in order to guarantee that the air inside the mold cavity may be smoothly released, an acceptable exhaust system should be mounted in injection molds. One can create the exhaust system using exhaust slots, exhaust holes, etc. To guarantee good exhaust effect, the width and depth of the exhaust slots should be rather planned in line with the fluidity of the plastic melt and the form of the cavity.
The injection molding process as well as component quality depend much on the cooling system. A decent cooling system may rapidly and evenly cool and solidify plastic melt in the mold cavity, lower the formation of internal stress, and increase the dimensional accuracy and UV resistance of components. The cooling water channels should be placed reasonably in line with the form and size of the components to guarantee that the cooling water may flow uniformly through all of the components when constructing a cooling system. Simultaneously, regulate the temperature and flow rate of the cooling water to prevent issues such component deformation or cracking brought on by either too quick or too slow cooling.
2, Select UV resistant materials
Common approach to increase the UV resistance of automobile components is adding UV resistant chemicals to plastic raw materials. Anti-UV additives can either reflect or absorb UV light, therefore lessening the damaging impact of UV radiation on polymers. UV absorbers and light stabilizers are common anti-UV additives; UV absorbers may absorb UV radiation and translate it into benign heat energy, therefore shielding plastics from UV damage. Under UV light, light stabilizers can stop plastics from oxidizing, hence extending their service life. Practical applications need for suitable anti-UV additives depending on the type of plastic and the use environment. Their dosage should be chosen accordingly.
Apart from including anti-UV additives, plastic materials having anti-UV characteristics can also be directly employed in manufacturing of vehicle components. For instance, further modification treatment can help to enhance the UV resistance already present in plastic materials including polycarbonate (PC) and polymethyl methacrylate (PMMA). Manufacturing car windows, lampshades, instrument panels, and other components calls for these plastic materials since they have good transparency, weather resistance, and mechanical strength.
3, Improve the molding process
Important parameters in the injection molding process, molding temperature and pressure affect the quality and performance of automobile components greatly. Good flowability and filling performance of plastic melt depend on an appropriate molding temperature, therefore guaranteeing the whole molding of components. Simultaneously, acceptable molding pressure can completely condense the plastic melt in the mold cavity, shrink the pores and flaws inside the components, and raise their density and UV resistance. Based on the type of plastic and the form and size of the components, the ideal molding temperature and pressure settings should be found in actual production by means of trial molding.
Furthermore influencing the UV resistance of automotive components are the injection speed and holding duration. Appropriate injection speed may rapidly and uniformly fill the mold cavity with plastic melt, thereby preventing flaws such weld lines and bubbles. Reasonable holding times help to increase dimensional accuracy and surface quality of the components, shrinkage and distortion can be minimized, and the plastic melt in the mold cavity can be compacted. Automobile component UV resistance and general quality can be raised by adjusting injection speed and holding duration.
4, Post processing technology
Automobile component surfaces can be successfully UV resistant by coating them with UV resistant layer. Among common surface coating materials include polyurethane, acrylic resin, etc. Good UV and weather resistance of these coating materials helps to block UV rays and so lessen the harmful impact on plastics. Surface coating treatment can be done by spraying, immersion coating and other techniques; however, the thickness and homogeneity of the coating should be regulated depending on real demand.
By irradiating materials with UV radiation, a new kind of encapsulation injection molding technique called UV surface activation raises their surface tension and improves the bonding strength between several components. UV surface activation technique can be used in the production of automobile components to bond soft and hard materials, such the bonding between silicone rubber and thermoplastic materials. Strong bindings between several materials can be generated by UV surface activation treatment, therefore enhancing the general performance and UV resistance of automotive components.