Plastics and composites can exhibit a wide range of mechanical properties, and changes between most components will be unavoidable during the manufacturing process, thus causing some deviations and manufacturing defects. These manufacturing defects can be attributed to various factors such as fluctuating heat treatment temperatures, molding defects, or inconsistent quality of plastic materials.
However, how to ensure the quality of the original plastic or the integrity of the plastic requires a specific set of evaluation and plastic inspection methods. The accuracy of manufacturing or evaluating a plastic product data can be determined by inspection of the chemical and physical properties of the original plastic resin or fiber. Raw plastics usually undergo a series of tests and screens to form vitality, and post-production quality inspections usually rely on various testing methods.
Testing of raw materials
Quality inspection of most plastic materials involves both resin or fiber formation. Resins, the main indicators include viscosity, moisture content, and color, while continuous fibers are often checked for tensile strength. Infrared and nuclear magnetic resonance spectroscopy are commonly used to identify basic chemical structures and levels of contamination. Other standard methods include chemical analysis, revealing the main acid or epoxy groups in a plastic compound, and liquid or gel chromatography to determine the average molecular weight and molecular weight distribution in the resin molecule.
The detection accuracy of chromatographic techniques is particularly demanding because the molecular weight and its distribution will affect the viscosity and mechanical properties of the plastic material. In polyesters, low molecular weight generally yields higher levels of viscosity, resulting in a slower rate of thickening. This can make the plastic more difficult to handle or extremely thicker to the appropriate extent. The level of moisture also affects the rate of thickening.
Ultrasound uses high frequency sound waves to track internal defects in a plastic material. The electric transducer produces sound waves that are then applied to the plastic, such as water, through a separate medium. Seismic waves pass through materials and their own energy levels, depending on how they encounter defects. The receiving transducer converts into sound waves and reflects them into electrical signals for display on the screen. The results can then be combined with predetermined design features to identify any internal defects.
Photography involves emitting a beam of radiation through a plastic part, then exiting and passing through each other while recording and measuring its power. The material helps to determine the difference between the initial strength and strength of the beam after the defect inside the object. The standard method uses X-rays and then records them on photographic film images, while gamma rays are more effective for thicker materials because they provide a higher degree of penetration. Defects in plastic appear in the tones or spots of the movie image. Photography is commonly used to detect the following defects
Like ultrasound technology, acoustic emission detection methods use sound waves to determine defects in materials. However, instead of transmitting acoustic reflections, acoustics rely on the discharge of elastic stresses that are released from the microscopic damage zone. In reinforced plastic composites, a small degree of stress can cause emissions at the damaged site, allowing the acoustic emission to detect defects in the location of the molded product within the map.
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