Plastic production has increased at an incredible rate since its introduction in the 1950s, with over 380 million tons of polymer resin and fiber produced globally, with numbers still rising. This is because plastic is a fantastic material in so many ways.
Plastic is inert, versatile, forms a hermitic seal, is inexpensive to produce, is derived from an abundant source, is lightweight, and is easy to shape into complex shapes. It reduces production and shipping costs while keeping perishable items fresher for longer. Human lives would be a lot less convenient if plastics did not exist.
However, it is important to remember that the characteristics of plastic that make it such a useful material, such as its longevity, stability, and low cost of production, are also what cause it to have a very negative impact on the environment.
Only 16% of plastics produced are currently being recycled and as companies look to increasingly work with recycled and recyclable polymers, thermal analysis will start to play an important role in ensuring that these new materials meet the high standards required.
Thermal analysis is an effective technique for assisting in polymer manufacturing and the development of new materials. Thermal analyzers help guarantee that the product always meets the standards that the customers expect and that the brand is associated with a high quality.
The article provides a quick overview of polymers and polymer analysis.
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Main Uses of Polymers
Packaging
Packaging is the most common application for polymers, with 146 million tons produced each year. This accounts for more than 35% of total polymer production. Plastic is an ideal packaging material. As it is lightweight, it can be formed into purpose shapes to safeguard delicate goods and forms a hermetical seal, which helps keep food fresh as it is shipped worldwide.
Building and Construction
Around 65 million tons of plastic are produced solely for the construction industry. Plastic is ideal for window and door profiles and seals due to its low cost and easy formability. Due to its durability, it is ideal for pipes and floor coverings, and its low thermal conductivity makes it an excellent insulator. It is also non-flammable when compared to more conventional construction materials like wood.
Textiles
Textiles are in third place. Every year, 59 million tons of plastic are produced for the textile industry. Most of this is clothing, with polyester and nylon being less expensive and thinner than cotton, making clothes lighter and less expensive to manufacture. These synthetic fibers are also used in soft furnishings such as rugs and carpets because they are lightweight, inexpensive, durable, and simple to clean.
Consumer and Institutional Products
Polymers can be found in a wide variety of products ranging from toothbrushes to furniture, as well as fast-moving consumer goods (FMCGs) such as toiletries. It is a broad category where plastic is used because of its low cost and, in many cases, is the only suitable material for the application, such as contact lenses. Every year, 42 million tons of plastic are produced for this sector.
Transportation
The increased use of plastics in cars and commercial vehicles has been motivated by the need to make cars more effective in order to decrease damaging greenhouse emissions. Plastic is a great lightweight alternative to conventional automotive materials, and complex polymer blends and architected plastics like acrylonitrile butadiene styrene (ABS) are becoming more common. Every year, the transportation sector alone requires 27 million tons of plastic.
Electrical/Electronics
Around 18 million tons of plastic are produced per annum to generate electrical and electronic items. As most plastic is electrically insulating, it is ideal for making electrical mounts, circuit board level packaging, insulating material like cable sheaths, and non-electrical parts of mechanical-electrical components. Conductive plastics, on the other hand, are now available and used when the component's conductive part must be flexible or have a very complex shape.
Industrial Machinery
With a remarkably low annual production of 3 million tons of primary-use plastic, the industrial machinery sector uses plastic in a variety of ways to reduce the weight and cost of plant equipment.
Every year, an additional 47 million metric tons of plastic are produced for a variety of smaller sectors.
Types of Plastic and their Uses
Polystyrene (PS)
Polystyrene, which accounts for 6.1% of all virgin resin demand in Europe, is used for protection and heat insulation in plastic cups, food trays, building insulation, and bicycle helmets. It is also an important component in packaging large, delicate items; however, it has a low recycling rate.
Polyurethane (PUR)
PUR, which accounted for 7.8% of European resin demand in 2020, is used for a wide range of applications due to its ability to be shaped into various materials. Flexible PUR is ideal for seats and handles, while foamed PUR is used for insulation products. PUR solids have high strength and are used in protective applications.
Polyethylene Terephthalate (PET)
PET is used in a large portion of food and beverage packaging, including plastic water bottles. It is especially useful for this because it provides a barrier to gases like oxygen and carbon dioxide. This keeps food fresh and carbonated beverages fizzy. PET resin accounted for 8.4% of all virgin resin demand in Europe in 2020.
Polyvinyl Chloride (PVC)
Over the last decade, the use of PVC, or vinyl, has decreased. PVC was once the second most used plastic resin, but it now accounts for only 9.6% of global demand. Due to its flexibility and high impact strength, it is still the preferred material for cable insulation and pipes, floor and wall coverings, window frames, and inflatable pools.
High Density Polyethylene (HDPE)
HDPE, as the name implies, is a strong material with very dense polymer chains. It is used in the manufacture of toys, shampoo bottles, milk bottles, and pipework. It accounts for 12.9% of resin demand and is easy to recycle.
Low Density Polyethylene (LDPE)
LDPE has a simple structure, making it simple and inexpensive to process into products. It is the material used to make grocery bags, plastic wraps, food storage containers, and wire covers. Despite some recycling challenges, LDPE accounted for 17.4% of plastic resin demand in 2020.
Polypropylene (PP)
As a result of its high heat resistance, PP is ideal for microwave-proof containers. It is stronger than LDPE but not as dense as HDPE. It is also found in currency, thermal vests, and diapers. PP is the highest demanded plastic type, accounting for nearly 20% of total plastic use. Unfortunately, it is not completely recyclable.
Others
Other types account for 18.1% of total virgin plastic resin demand. PMMA for touch screens, PTFE for telecommunication cable coatings, and ABS for automotive parts are examples of important plastic types.
What are the Main Purposes of Polymer Analysis?
1. Quality Control
The primary reason for polymer analysis in a manufacturing environment is quality control. Will the final product look and function as it should over the part’s lifetime? Will it be scrapped before it departs the facility? Will the customer dismiss it, or must the company conduct a product recall? With such stringent specifications for polymer-based products, it is obvious that strict quality control is required.
There are two main options for production quality control: inline/online analysis or offline/atline analysis. The benefits and drawbacks of each are examined below.
Inline or Online Quality Control
Here, a system that is an integral part of the manufacturing line monitors the products in real-time during manufacturing. It provides immediate feedback, allowing users to halt production if there is a problem. Users can save money and time as a result of this. However, it does not work for all types of samples, and these instruments may have lower detection limits than offline instruments.
Offline or Atline Quality Control
Here, the analysis equipment is housed in a lab or off to the side of production, and samples or raw materials are removed from the line for analysis. It is the most common type of analysis in the polymer industry. Measurements are not performed in real-time, but with fast analytical techniques, users can still get relatively fast feedback on production runs, and they have the advantage of selecting equipment with the best detection limits.
Offline quality control consists of the following:
- Visual Inspection: This is the simplest and least expensive method of determining whether something is correct. It is also adequate for basic checks, such as determining whether the product is the correct color or whether it has any cracks or other visible defects. It is, however, subjective to the operator and must frequently be supported by other methods.
- Chemical Analysis: This is ideal for determining the composition and determining which elemental components are present and which are missing. Chromatography and XRF analysis are two examples of techniques. Chromatography takes time and requires complex sample preparation, whereas XRF is simpler and faster.
- Physical Property Analysis: Thermal and mechanical property analysis provides direct insight into how the component will function in the field. It includes tests such as tensile strength analysis and impact testing. There are numerous options for physical property analysis, but thermal analysis is one of the most versatile because it also tells what the polymer is made of. It can be used to check the composition of raw materials as well as finished goods to ensure that in-house processing has not changed the physical properties in an undesirable way.
2. Research and Development
Creating new materials for specific applications requires testing to ensure they look and perform as expected. When developing a new product, techniques like thermal analysis are used to ensure that the product has the appropriate physical properties. It is important to ensure that the additives used to control the final color do not interfere with crystallization or strength when testing new formulations in the lab.
The analysis will also be used to evaluate potential new materials for use in existing production lines, for instance, ensuring that the recycled materials have the same appearance and performance as virgin polymers.
Another application of polymer analysis is determining the compositional makeup and physical specifications of a competitor's product. When customers require a backup supplier, this is useful for reverse engineering parts.
Predicting the Performance of New Materials
Predicting component performance over its lifetime is one useful application of thermal analysis, especially for new materials. It is possible to predict product lifetime using STA (simultaneous thermal analysis) equipment and then use sophisticated software techniques to estimate how long it takes for the material to degrade under normal conditions. This type of analysis can save years of development time.
3. Troubleshooting and Tackling Customer Complaints
This could be for internal troubleshooting as well as customer returns or complaints. Challenges with polymer-based products include the following:
- Parts that are misshapen or cloudy
- Too stiff or insufficiently stiff, resulting in poor damping
- The raw material is not pure.
Thermal analysis provides data on crystallization, material additives, strength, and rigidity, among other things. This family of techniques can be used to conduct root cause analysis of production issues or address customer complaints by demonstrating that the material is performing as it should.
Thermal Analysis for Polymer Analysis
Thermal analysis (TA) refers to a group of analytical techniques that evaluate how a material’s behavior changes as a function of time and/or temperature, whether heated, cooled, or kept at a constant temperature. Sample sizes are typically in the mg range, and the material changes identified can be small.
Changes in sample weight, viscosity, temperature, and sample dimensions are examples of material behaviors that are observed. These quantifiable changes are plotted on an output graph, and the properties of these graphs provide accurate data on fundamental material properties such as melting point, glass transition temperature, and crystallization temperature.
From this, you can determine a material’s fundamental characteristics and composition and predict how the material will behave in each application.
A simple example is whether the plastic used in a high-temperature application (like a car engine) has a high enough melting point to remain solid when in use.
Advantages of Thermal Analysis
Thermal analysis has the primary advantage of accurately analyzing fundamental bulk material properties. Even for complex materials, the behavior of the constituent polymers can often be teased out to determine what is in the mix. It is applicable to a wide range of materials and does not require material-specific calibration curves, allowing users to explore novel materials with ease.
There is very little sample preparation, no harmful chemicals to contend with, and the analyses can be run by anyone with little training, particularly with an instrument with a high degree of automation.
The analysis procedures are comparatively short, with many completed in less than an hour. The equipment is inexpensive to operate and does not need to be left on standby when not in use, reducing electricity and gas consumption.
X-Ray Fluorescence for Polymer Analysis
X-Ray fluorescence (XRF) analyzers are used for elemental and compositional measurements within a polymer matrix, whereas TA provides better baseline performance and sensitivity for materials verification and thermal behavior characterization.
XRF analysis is used for a variety of purposes, including testing raw polymers and finished products for chlorine content, which indicates the presence of PVC (and potentially phthalates) in the materials being used. It can also be used to determine the bromine content of polystyrene waste. Sample preparation is required to separate HBCD from other brominated compounds. Metal content in plastics can also be easily measured using XRF.
Advantages of XRF
XRF is a quick and non-destructive technique that can analyze polymers in solid, powder, liquid and pellet forms with little sample preparation. It can be used on finished components for an ultimate elemental compositional check because it is completely non-destructive. It can also determine the thickness and composition of metal coatings on plastic components, like metal plating.
This information has been sourced, reviewed and adapted from materials provided by Hitachi High-Tech Analytical Science.
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