Following on from the previous article on formulations, Pravin S Mistry from the Plastics Consultancy Network investigates various blending procedures and their applications for mixing compounds and masterbatches.
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Firstly we need to know the difference between compound and masterbatch concentrates. A compound is compounded as a whole and purchased ready to use straight away ‘as is.’ Whereas masterbatch is a pre-dispersed colour concentrate that is let down with natural polymer in ratios from 1 to 5%.
There are different ways of mixing thermoplastics for compounding (compounds & masterbatches/concentrates). The choice of blender type and size are many and varied, the most common being tumble, ribbon or high-speed blenders. Blends can be as little as 25kgs or 5 tonnes plus, depending on the size of the blending vessel being used though typically they are sized to make between 100 to 500kg batches.
Most compound blends involve pellet feed and contain pigment levels of less than 1% and these are often made in tumble or ribbon blenders because they do not normally need high speed mixing to develop or homogenise the blend.
Masterbatches on the other hand, because they have pigment loadings of up to 70% and are usually made using powder polymers, need high speed mixing in order to develop and homogenise the pigments within the blend.
Mixing can take place off-line or on-line. Both – (compound & masterbatch) are considered batch procedures where materials are mixed with polymer (in powder or pellet form) with the additives e.g. colours, fillers etc. These can be just single blends or multiple blends depending on the size of the production order and the blender capacity.
We have named a few disadvantages and advantages, and there are more, however, each manufacturer has their own preferences.
Note; Some additives like antistatic or slip additives have a low melting point of 30 to 60c. High-speed mixing can generate temperatures in excess of this, and if this happens, the blend can become very lumpy and difficult to feed, so care must be taken to avoid this problem. Normally these types of additives are added later than the rest of the components, and the speed of the high-speed blender is lowered to avoid generating so much heat. This problem does not occur in tumble or ribbon blenders as the blend speeds are much lower.
When these blends are due to run on the extruder, they can be pretested within the laboratory or ran directly onto the production line. These can be ‘test’, or ‘no test’ mixes.
If pretested in the laboratory, the laboratory extruders must have a good correlation with the actual production extrusion lines; otherwise, the colours can develop differently. Accurately pretesting blends within the laboratory allows all the blends to run without delay, straight onto the extruder lines. This is considered to be the most efficient method if done correctly.
To assess the quality in the case of compounds the mixed blend is often tested in the lab straight into an injection moulder or two roll mill and the colour, is checked for accuracy either visually or using a spectrophotometer.
For masterbatch formulations, the blend is first run through a small twin-screw extruder prior to testing on the injection moulder at the specified addition rate. If the colour is okay it is passed, if not the formulation has a modification, is re-blended and tested until the correct result is achieved.
Sensitive formulations that have historical processing problems always undergo a test at the blending stage.
– You are not holding up an extruder for long periods of time.
– If it is online mixing or off line, and production is waiting to process the material, there can be some downtime in production and on occasions the pre-test does not give the same expected shade as the plant extruded material, meaning a rerun and correction of the blend will be necessary.
If the material is going to be run directly onto the extruder it’s not unusual as a procedure for a small sample to be first dropped out of the blender to be run through the production extruder line as a pre-check; only if the colour is right does the rest of the blend get extruded. If the colour needs adjusting then the blend is respun with correction and the process is repeated until the colour is judged to be acceptable.
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Once a good reliably consistent formulation has been established, most companies take a view that pretesting the material out of the blender using the production line is too time-consuming and skip this pre-test. This blend consistency can only be achieved if the blend conditions remain exactly the same as well as the consistency of the pigments and that the weighing of the correct components going into the blend is always done accurately.
Another point to mention here is that from the previous article when formulating compounds, what works in the laboratory does not always work first time in production. Hence there is always a lot of tweaking and hand-holding done by the laboratory and process engineering. More and more new mixers are coming onto the market from small-batch operator – friendly, to completely automated systems. In addition, mixers are easier to clean down so there is less downtime.
When multiple blends are involved it’s sometimes necessary to homogenise the total quality to better improve the colour consistency after the extrusion process. This is usually done if the colour variation is considered to be too extreme within the batch to satisfy the end customers’ needs. The homogenisation is usually done in tumble or ribbon blenders, though high-speed mixers can also be used.
It’s also worth pointing out that sometimes the manufacturing company prefers to add the components used within the formula directly on line either through separate side feeders, as is often the case with large percentages of fillers and pigments like titanium dioxide, or by using gravimetric or volumetric feeders positioned directly above the throat of the extruder for smaller quantities. Some extruder lines have up to 8 feeders which can add quantities of less than 1% or up to as much as 80% depending on the size and type of the feeder equipment or side feeders being used.
This method of manufacture is less labour intensive, and for large production runs is often preferred, though the calibration and maintenance of the feeders has to be maintained at the highest level in order to ensure the right quantities of each component are being added.
Customers normally choose to go the masterbatch route because they save money and have better control of their feedstock.
Purchasing 20 tonnes of a coloured compound means customers have to pay the manufacturer for each tonne processed, which tends to vary from anything between £400 per tonne to £ a tonne which is quite an expense. If however customers can use a 1% masterbatch then they will only be paying for 200kgs of masterbatch production costs the rest of the kgs will be their own natural base polymer.
Another advantage of using masterbatch is lower stock holding leading to less risk of high volumes of redundant compound colours being accumulated.
The only disadvantage of going the masterbatch route is usually in the colour accuracy or possible streaks in the mouldings where the masterbatch has failed to disperse correctly. Sometimes on older injection moulding machines, the masterbatch cannot be incorporated as uniformly as it should be and in these cases, it might be necessary to assess the compound route.
From the color and texture of plastic products play an important role. Not only does this make them look nice, but it increases the trust people have in them. Products that are colorful and feel good, tend to gain consumer attention. As a result, masterbatch is one of the best ways to achieve the colours and textures you want in your plastics. “Yuezheng” is a manufacturer of high-quality masterbatch, enabling you to have the perfect color and texture in your plastic products. So let’s dive in and learn more about why masterbatch is so useful and how it makes a huge difference in your production process.
Yuezheng’s masterbatch is a special blend of colors and other ingredients, known as pigments and additives. When you are producing items, whether it is toy or containers, you can add this masterbatch to plastic. Your plastics will be homogeneous in color as well as look because color in the masterbatch mixes good in the resins. And this is key because nobody want to buy one product in many colors and one with inconsistent looks. With masterbatch, you don't have any problem of mixing colours in your product or blending colors on your own, which is quite cumbersome and messy work.
This is the second way whereby masterbatch is a savior to save money for the plastic manufacturer. Color and other material costs may be pricey and also involve time-consuming efforts. Sometimes you will need to buy different colours, and it might end up causing additional cost, but pre-mixed masterbatch saves you that cost. Masterbatch is very concentrated so it would not take much of it in addition to your plastic to make it the right color and achieve any other effects required. That means you can cost cut and still have products that look good!
Masterbatch can improve the strength and quality of plastic products in many ways, including their colors and materials. To give you a flavor, consider special ingredients like UV stabilizers that prevent damage from sunlight. For outside items like lawn chairs and umbrellas that sit in the sun for hours, this is important. Other ingredients are formulated to decrease static electricity buildups — which can be an issue on some plastics. Yuezheng offers many masterbatch for enhancing your designs of plastic products and extending service life. Tougher products create happier customers!
Masterbatch refers to a type of plastic products production that entails the generation of fewer amounts of waste. The fact that all things are premixed in masterbatch means that you will be assured of similar color and material each time you produce. It means you will not have to spend a lot of extra time testing and trying to achieve that perfect color and texture. With "Yuezheng" masterbatch, you can make things faster and more effectively. It saves your time and money. Similarly, as less plastic will be wasted in production, it is a more sustainable and economical process.
Here at "Yuezheng," hdpe of ldpe we realize that your products sometimes require special colors or features. If you have other requirements, we have a crew of experts to customize the masterbatch on your request. Maybe you need a specific shade of blue or green that aligns with your company logo or branding. Some special ingredients like for cleaning or safety could also be added and help you make the products more attractive to your customers. With a little customizing of the masterbatch, you can finally have the color for your plastic products that you always wanted and that kind of souls and life that makes them one of a kind.
All things considered, masterbatch has so many advantages while producing plastic. You get the same color of products, saving money, makes your products more solid, decreases the waste of production, and can be custom-made according to your needs. If you are able to possess good quality "Yuezheng" masterbatch, all of these will come easily into play, ensuring your plastic product perfectly meets customers' demands. Absolutely, Masterbatch is a wise solution for any business looking forward to making good quality plastic products!