Plastic usage and importance keep on growing. Plastic comprises a range of synthetic and natural compounds that offer specific mechanical properties for various applications and industries.
Plastics contain a range of reinforcing materials and fillers additives. The combination of these materials and the manufacturing process have a considerable impact on the mechanical properties of the plastics.
The quality of plastic is often synonymous with how well a material meets its performance expectation.
So today, you will get to learn about UV testing on plastics of plastics to achieve quality.
Let’s get started!
Why Subject Plastics to UV Testing?
Ultraviolet exposure (UV testing) is performed to know how a material will withstand the damaging effects of ultraviolet exposure.
Prolonged exposure to UV rays cause a lot of effects among them
- Fatigue and reduction of strength
- Yellowing or discoloration,
- And general deterioration
How is UV Testing Done?
UV tests are used for products, parts, and components under solar radiation conditions. The products are subjected to ultraviolet exposure in a controlled environment.
A simulator is used to create ultraviolet radiation. And simulate the period of exposure.
The tests produce conditions a product is likely to be exposed to during its lifetime.
The testing is performed following EN 61439-1 Resistance to ultra-violet (UV) radiation.
UV Exposure in Your Region
The UV resistance of plastics is expressed in years.
The plastic life depends on the total amount of UV radiation your material is exposed to.
This is changes across geographical areas as solar radiation is not equally distributed throughout the world. The uneven distribution of solar radiation is influenced by altitude, latitude,
season, and atmospheric conditions
Besides, the total solar radiation received at ground level consists also of different components such as direct and indirect radiation.
the isolines of the mean global solar radiation have been developed using data provided by satellites. They are then illustrated in maps.
You can download a radiation map and determine the average radiation level in your region, commonly expressed in kilo Langley per year (kLy/yr). The Langley as a unit of measure for radiation power takes its name from NASA Langley Research Center.
The center studies the impact of solar radiation on Earth.
1 Kilo Langley = 1 kcal/cm2 = 41.8 MJ/m2
1 Kilo Langley per year = 1.3 W/m2
For example, in most Northern Europe the average radiation level ranges between 80-100 kLy/year.
When buying say netting or tarpaulin cover, ask for your product UV resistance factor
EyouAgro provides products where this measure is applicable, a UV resistance factor, expressed as total radiation for the minimum product lifetime.
Let’s say, you have a product with 500 kLy/yr. And you intend to use it outdoor in Northern Europe. If the radiation is at 100 kLy/yr, your product will have a UV life of 5 years.
What does UV Testing Involves
The accelerated aging and UV weathering testing. The weathering tests on polymers, coatings, metals, and small components. Element’s labs are equipped to perform some of the most popular UV testing standards, including ASTM G154, ASTM G155, and ISO 4892,
There are four common methods for producing plastic test samples:
- Machining – Taking a sample of the test material and shape it by grinding or cutting away the undesired material. This is performed on rigid plastics.
- Die-cutting – The samples are easy to produce as many samples can be cut from a single sheet of material.
- Injection molding – This involves heating the plastic material until it is a liquid and injecting it into the mold of the desired shape. It allows for the production of highly specialized shapes.
- Compression molding – The specimens that are compression molded is formed by pushing the material into a mold so that is deformed into the shape of the mold.
How do you choose the process to use? It will depend on the characteristics of the material that the test is performed.
How are Materials Analyzed and Tested?
Materials analysis and testing of UV exposure are conducted through a process known as accelerated weathering. This is the simulation of environmental conditions using special chambers and instruments to speed up the weathering process, measuring their effects on components, products, and materials.
The key factors that form the evaluation of a materials test and analysis include:
- The material change from UV exposure
- To what extent its properties have been altered
- And how the change compares to alternative materials that could be used
This forms a documented basis of comparison and detailed information of materials for manufacturers in the production of plastics.
As you can see the effects of degradation and discoloration must fall within an acceptable range.
You have a choice of testing standards including:
- American Society for Testing and Materials (ASTM)
- Standard practice for fluorescent UV lamp
- International Organization for Standardization (ISO) method specification for exposing specimens to Xenon-arc light in the presence of moisture—to reproduce the weathering effects that occur when materials are exposed in actual end-use environments
What Technology is Used?
The testing, measuring, and analyzing UV degradation involves the following fluorescent, Xenon arc, and Carbon arc UV testing machinery to simulate climatic environments.
Fluorescent testing equipment
- Bulbs are used to emit a controlled amount of light within a specified UV spectrum.
- Simulation of the real world to accelerate UV degradation.
- Cost-effective and many samples can be exposed simultaneously.
- Most economical types of testing and single samples or many samples can be exposed at any one time.
Xenon arc machines
- Test the radiation spectrum of simulated sunlight
- Use the noble gas to create an arc light
- The best type of equipment for testing discoloration in materials and coatings, due to the sensitivity of pigments and dyes to longer UV wavelengths.
- Environmental variables such as temperature and moisture can be controlled to more accurately simulate real-world conditions.
Carbon arc testing
- Simulates natural sunlight accurately and produces a high-intensity of UV
- Result in unreliable analysis
The polymer degradation through UV exposure will be led by the global trends in plastic production. This then requires:
- Stakeholders working closely together to agree on common standards
- Sharing of platforms that will lead to more standardized industry adoption of UV exposure durability
- Reduction of research and development costs, risks, and lead times for production
Furthermore, standardized quality control methods will become more widespread in many countries due to acquisitions as production centralization and economies of scale are applied.
If a product is to be exposed to direct sunlight then the testing standards are to be specified.
Ensure desired formulations to maintain long-term properties include additives to the melting process or if high volume the additives can be compounded resin.
UV testing forms the main part of quality control for the manufacturers to be equipped to adapt to a transforming global market.