At present, the issue of brittle profiles has been a major challenge for many profile companies in China, affecting their normal operations and product quality. The brittleness of aluminum profiles not only impacts the visual appearance but also influences the recognition and satisfaction of door and window assembly manufacturers, ultimately affecting market share and brand reputation.
The brittleness of the profiles is typically reflected in the physical and mechanical properties of the material. One of the main characteristics is that the material tends to crack or break suddenly under stress, often without visible deformation. There are several reasons behind poor mechanical performance in fabricated products, which can be summarized as follows:
First, the formulation and mixing process may not be optimized. This includes excessive filler content, improper selection or quantity of impact modifiers, incorrect amounts of stabilizers, overuse of external lubricants, and issues with the hot mixing sequence, temperature settings, and aging time. All these factors play a crucial role in determining the final performance of the profile.
Second, the extrusion process may be improperly controlled. For example, an incorrect amount of plastic material being used, insufficient head pressure, failure to remove low-molecular components, low screw torque, or mismatched traction speed relative to the extrusion speed can all lead to subpar results.
Third, the mold design might not be ideal. Poor die section design, especially the distribution of internal ribs and the handling of corner interfaces, can cause stress concentration. To address this, designers should avoid sharp angles and ensure smoother transitions. Additionally, inadequate die pressure—often due to a low compression ratio or short straight section—can result in less dense products, negatively impacting mechanical properties. Adjusting the die's straight section length or selecting different compression ratios can help improve this. It’s also important to consider the compatibility between the extruder screw’s compression ratio and the die head design.
Moreover, poor convergence of branching ribs can lead to structural weaknesses. Increasing the length of the ribs, improving the confluence area, or adjusting the compression ratio can help resolve this issue. Uneven die discharge can cause inconsistencies in wall thickness or density, leading to differences in mechanical properties on either side of the profile. In some cases, this might result in failure during cold impact tests. Thin-walled or non-standard profiles can further complicate the issue, but they are beyond the scope of this discussion.
Finally, the cooling rate of the fixed mold is another critical factor. The temperature of the cooling water is often overlooked, yet it plays a vital role in shaping and solidifying the stretched macromolecules in the profile. Proper cooling ensures the material maintains its desired structure and performance characteristics for long-term use.
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