Plastic products can display different mechanical properties and these variations from components are most of the time caused by the production process they have undergone. In other words, these quality plastic products were perfectly designed in such ways. However, deviations are sometimes inevitable which could lead to defects and flaws in plastic product manufacturing. This is where quality in plastic products are tested and why the manufacturing process play a huge role to it.
A good number of plastic manufacturers produce top quality plastic products in the market today. Sad to say, there are also a few who are able to manufacture low quality plastic products despite having the right knowledge and technology. There are a lot of factors which can be attributed to the latter and these include inconsistent heating temperature, molding issues and poor quality control checks for injection molding just to name a few.
Resolving low quality issues among plastic products is not easy and it requires close monitoring of manufacturing parameters which is a vital process in plastic quality control. Each stage of product fabrication has to be monitored meticulously to make sure each plastic product comes out of the production line in the right standards and quality. In this article, we will discover the different factors affecting plastic products’ quality and help you distinguish the following. There are many more very specific plastics tests, but we have to limit this list to the most common ones.
Methods to Verify Quality of Plastic Products
1. Plastic Resin Variety
Assuring the quality of raw plastics and its integrity within a plastic product requires extensive evaluation and inspection methods. The chemical and physical properties of the plastic material should be further examined to identify whether such plastic resin is feasible for manufacturing or passable for the material requirements of a plastic product.
Raw plastics normally undergoes testing to see whether they are capable of viability and post-production quality control in plastic industry ensures the materials used for the plastic product are as good as they were intended to be for the plastic product design. Anything less further means the plastic variety is not viable for such plastic product.
2. Raw Material Inspection
Raw plastic materials are always expected while they are still in the form of a resin or fiber. When it comes to resins, the plastic quality control factors to check has to be its viscosity, shade and moisture levels while fibers are always being examined for its seam strength. Raw material inspection requires advanced technology such as infrared or nuclear magnetic spectroscopy to further identify chemical structures of the components along with its contamination levels.
Some other plastic quality control methods involve liquid chemical analysis which exposes the acid or epoxide groups within a plastic compound. Others also take advantage of gel or liquid chromatography which helps determine the average molecular weight distributed among resin or fiber molecules.
Gel or liquid chromatography is extremely useful in assuring plastic products’ quality because molecular weight and its distribution is instrumental to the material’s viscosity and eventually its mechanical properties. For example, with polyester, low molecular weight results to high viscosity levels which means a slow thickening rate. This will make the plastic material hard to handle and time consuming to thicken for its desired state. Raw materials’ moisture levels are also factor to its thickening rate.
3. Ultrasonic Inspection
Ultrasonic inspection is an advanced technological method to test plastic materials’ quality. It employs the use of ultra-high frequency sound waves to expose internal flaws on a plastic material such as hollow spaces and rifts. An electric transducer is used to release these sound waves through a medium such as water being applied to the plastic material. As the sound waves moves across the plastic material, the consistency of the energy levels change whenever they encounter defects and flaws to the plastic material.
The electric transducer also assesses the sound waves and displays them on a screen monitor to make it easier for the plastic quality control manager to visualize the results. The same results will be used to define the characteristics of the plastic material and the most common flaws exposed through this quality control method are voids, collection of small voids, gaps or rifts and presence of foreign materials or contaminants. Inappropriate industrial design of the product can contribute to internal flaws as well.
4. Radiographic Testing
Radiographic testing is a quality control process which involves exposing a plastic material to a beam of radiation while recording and measuring the radiation’s intensity as it passes the material through the opposite end. The initial and final intensity of the radiation beam will serve as a determinant to flaws and defects within the plastic material. This procedure is a standard quality control injection molding process for big plastic manufacturing companies prior to entering the mass production stage.
The radiographic testing method employs x-rays which are then materialized as visual images on photographic film. When it comes to plastic materials with a certain degree of thickness, gamma rays are used for further intensity. Flaws and defects such as voids, translaminar fractures, inconsistent fibers, presence of foreign materials or contaminants and uneven fiber distribution to the material can be seen as dark spots on the photographic film.
5. Acoustic Inspection
Much like ultrasonic inspection, acoustic inspection also employs the use of sound waves to detect defects and flaws to the plastic material. But instead of exposing the material to intense sound waves, this method relies on sound emissions from areas to the plastic material with defects and flaws. A certain amount of pressure and force applied into the material will result to acoustic emissions exposing the defects and flaws of the plastic material.
Common flaws and defects detected through this plastic quality control method are microscopic cracks, fiber inconsistencies, broken fiber bonds, breakage and local delamination. Acoustic inspection can be pulled off by placing sensitive transducers at certain areas on the plastic material’s surface. Once surface disturbances are detected, the transducers record these as data for the quality control team to assess later on.
The following processes mentioned above are standard plastic quality control methods in determining whether plastic materials are of low or high quality. If they pass these plastic quality control tests, then it can be assured that the plastic product is of top quality based on its material and components. Also check out the ISO publications for testing details.