Selecting Carbon Black for Paints, Coatings and Inks

Adding carbon black (CB) particles to elastomeric polymers is essential to the successful industrial use of rubber in many applications, and the mechanical reinforcing effect of CB in rubber has been studied for nearly 100 years. Despite these many decades of investigations, the origin of stiffness enhancement of elastomers from incorporating nanometer-scale CB particles is still debated. It is not universally accepted whether the interactions between polymer chains and CB surfaces are purely physical adsorption or whether some polymer–particle chemical bonds are also introduced in the process of mixing and curing the CB-filled rubber compounds. We review key experimental observations of rubber reinforced with CB, including the finding that heat treatment of CB can greatly reduce the filler reinforcement effect in rubber. The details of the particle morphology and surface chemistry are described to give insights into the nature of the CB–elastomer interfaces. This is followed by a discussion of rubber processing effects, the influence of CB on crosslinking, and various chemical modification approaches that have been employed to improve polymer–filler interactions and reinforcement. Finally, we contrast various models that have been proposed for rationalizing the CB reinforcement of elastomers. 

Natural rubber composite has been continuously developed due to its advantages such as a good combination of strength and damping property. Most of carbon black (CB)/Natural Rubber (NR) composite were used as material in tyre industry. The addition of CB in natural rubber is very important to enhance the strength of natural rubber. The particle loading and different structure of CB can affect the composite strength. The effects of CB particle loading of 20, 25 and 30 wt% and the effects of CB structures of N220, N330, N550 and N660 series on tensile property of composite were investigated. The result shows that the tensile strength and elastic modulus of natural rubber/CB composite was higher than pure natural rubber. From SEM observation the agglomeration of CB aggregate increases with particle loading. It leads to decrease of tensile strength of composite as more particle was added. High structure of CB particle i.e. N220 resulted in highest tensile stress. In fact, composite reinforced by N660 CB particle shown a comparable tensile strength and elastic modulus with N220 CB particle. SEM observation shows that agglomeration of CB aggregates of N330 and N550 results in lower stress of associate NR/CB composite.

Carbon black is a highly engineered form of carbon widely used in paints as paint carbon black, coatings and inks to achieve a spectrum ranging from gray to deep black. Over the time, the properties of carbon black pigment have been modified to achieve required properties in the final product, such as increased tinting strength, improved the level of jetness or blue undertone and conductivity.

Explore the different carbon black production processes and the properties to consider while selecting the right carbon black for your formulations.

Properties and End-uses of Carbon Black
Carbon black is used in many products and articles we use and see around us on a daily basis, such as: rubbers, plastics, coatings, tires, ink carbon clack.

Thus, the requirements for the carbon black are different for each application and influence the specific properties in the final application.

For the coating carbon blacks market, there is a wide range of carbon black grades available. This can make it difficult to choose the most suitable carbon black for your final application. For example, when aiming for automotive paint with a blue undertone, the carbon black of choice will have a high jetness. However, normally these types of carbon black grades are the most difficult to disperse correctly into the desired particle size.

The carbon black producers are addressing these issues by developing specialty carbon black grades that have been surface-modified and/or are pre-treated to overcome these difficulties.

How Carbon Black is Produced?
The properties of the carbon black are influenced by the method of preparation. The different processes used for channel carbon black production are discussed below.

Furnace Black Process: It is the most common method which uses (aromatic) hydrocarbon oil as the raw material. Due to its high yield and possibility to control the particle size and structure, it is most suitable for mass production of carbon black.

In the reactor the conditions (e.g. pressure and temperature) are controlled to provide a number of reactions. The most important reactions include: particle nucleation, particle growth, aggregate formation. Water injection rapidly reduces the temperature and ends the reaction. The primary particle size and structure of the carbon black is controlled by tuning the conditions in the reactor and the time allowed before the reaction is quenched.

Thermal Black Process: It is the most common method used for carbon black production after the furnace black process. It is a discontinuous or cyclical process.

This process uses natural methane gas as raw material. When the natural gas is injected into the furnace at an inert atmosphere, the gas decomposes into carbon black and hydrogen. The carbon black produced using this method has the largest particle size and the lowest degree of aggregates or structure. Due to the nature of the raw material, this carbon black is the purest form available on the industrial scale.

Channel Process: This process uses partially combusted fuel which is brought into contact with H-shaped channel steel. It is not the most used method anymore because of its:

The benefit of this process is that it provides carbon black with a lot of functional groups.

Acetylene Black Process: This process uses acetylene gas as raw material. It produces mainly high structure and higher crystallinity, making this type of carbon black suitable for electric conductive applications.

Lampblack Process: It is the oldest industrial process for making carbon black. It uses mineral/vegetable oils as its raw material.

Recovered Carbon Black from End-of-life Tires

Recovered carbon black or ®CB is a fast-expanding market. Recovered high purity carbon black is obtained through the pyrolysis process of end-of-life tires. The importance of companies in the production and use of recovered carbon black is three-fold:

The growing global problems arising with end-of-life tires (ELT)
Companies shifting strategy to fulfill the targets ensuring a green economy
Price changes of regular carbon black due to fluctuations in oil pricing

Depending on the composition, the content of carbon black in tires can be up to 30%. Next to carbon black, the tires consists:

Rubber
Rubber processing additives
Metal
Textile
Fillers such as silica

The amount of silica depends on the type of tire, for example winter or summer tire, racing tire, or tire for agricultural vehicles, and will not be separated from the carbon black during the pyrolysis process, which will result in higher ash content.

In a typical car tire, up to 15 different types of conductive carbon blacks can be used, each attributing to the different properties required. This blend of environmental carbon blacks will then also be the make-up of the final ®CB composition. Besides tires, other sources that can be used are rubber conveyor belts or other technical rubber products.

The main differences in the properties of recovered carbon black are:

The ash content is higher for ®CB caused by the fillers being used in tire production.
A blend of rubber carbon black properties as a result of the carbon black used in the tire.
Residual hydrocarbons on the carbon black surface, depending on the quality of the pyrolysis process.

To understand how the properties of ®CB influence the final applications and to know which plastic carbon black is used in which category, we need to understand the fundamental differences between the available carbon blacks.

How Liquid Filling Machines Benefit the Paint and Coatings Industry

How Liquid Filling Machines Benefit the Paint and Coatings Industry
Using Filling Machines to Increase Efficiency and Profitability
Liquid fillers are integral to liquid packaging lines, with automated models capable of maximizing efficiency. Without this equipment, the filling process wouldn’t be reliable enough to ensure that no product loss occurs because of inaccurate fill levels.
Technological developments that are creating more automation and computerizing many of the components in filling machines have made them more dependable than ever before, with many of the best models designed to allow for full customization and user friendliness.
One type of liquid filler that can meet the needs of the paint and coatings industry is the net weigh filling machine. Designed to handle products of low to high viscosity, net weigh fillers are ideal for filling liquids in bulk quantities, such as 5-gallon pails, with consistent weight levels for each container.
Net weigh fillers work by using independently timed valves with custom programming through the filler’s computer. They can then fill precise amounts of liquid by gravity into containers, stopping once the liquid reaches the specified weight.
These fillers can fill many different types and sizes of containers, with many of the top models capable of lasting for many years.
What is a Piston Filling Machine?
At Liquid Packaging Solutions, there are a number of different types of filling machines manufactured to handle different product viscosities, different fill sizes and other variations in packaging projects. The piston filling machine can solve many issues for products with particulates or high viscosity liquids, though it can also handle thin and medium viscosity products as well.
As product sits in the hopper, the valve, which sits between the hopper and the nozzle, will be open from the hopper to the cylinder. The piston will begin to withdraw from the cylinder, typically after an operator activates the fill by stepping on a foot switch. As the piston withdraws, product from the hopper will fill the empty cylinder. Once the piston has withdrawn to the desired point, the valve will rotate to allow product to move through the nozzle. At this point the piston push back in to the cylinder and move product through the nozzle and in to the waiting bottles or other containers. This process creates a highly accurate volumetric fill as the interior volume of the cylinder will never change, meaning the volume of product released to the bottles will never change.
The hopper sizes can vary from project to project based on the size of the containers or fills. Not all piston filling machines, and in particular, the automatic piston fillers, will use a hopper from which to pull product. Automatic lines will likely include a tank or pull from a bulk source. The cylinder and piston combination are also available in different sizes to accommodate different projects. The speed with which the piston moves can be adjusted, different piston sizes can be used to meet volume requirements and even multi-piston, automatic filling machines can be designed for use with inline packaging systems. LPS piston fillers allow the operator to adjust the length of the piston stroke, which in turn adjusts the volume of product that is pulled in to the cylider with each fill cycle. This way a single piston size can handle a range of container sizes. While multiple strokes of the piston can also be used for larger fills, at some point the efficiency of using multiple strokes will become low enough that simply changing out the piston for large containers will be the better solution.
The nozzle used on any piston filler will be chosen to meet the needs of the particular project at hand. For instance, a product with large chunks of fruit or vegetables will not work well if a narrow nozzle is used to move product in to the bottles. On the other hand, a very large nozzle will be cumbersome with a small mouthed bottle. There is virtually no limit to the type of nozzles that can be used, including custom manufactured nozzles where special projects are concerned.
Though a simple concept, the piston filler can be an ideal solution for many projects and for liquids thick and thin. Though these machines are known for handling viscous products, in the right circumstances they will handle free-flowing liquids as well. For assistance finding the best type of filling machine for your own packaging project, contact Liquid Packaging Solutions today.
Overflow fillers, gravity fillers, automatic piston filling machine and other liquid fillers all vary in the way that they move product into a bottle or container. However, the automatic versions of these machines almost always have certain features in common. These features are intended to add efficiency, consistency and reliability to the packaging equipment. Below are a few of the most common features of found on Liquid Packaging Solutions’ bottle fillers.
Heavy Duty and Portable Stainless Steel Frame
For consistent and reliable fills, the machine must be stabile throughout the process. The heavy duty stainless steel frame protects against shifting, vibrating and other movement that might effect the volume or the level of the fill, while also avoiding splashes and spills. The stainless steel material is compatible with a vast majority of products, though there are exceptions. When corrosive liquids are run on the machinery, other construction materials may be used for the frame, including HDPE. Ultimately, the material used will be that material which will better extend the useful life of the equipment.
Easy Adjustments From Height to Heads
Many packagers fill more than a single product, or at the very least fill into bottles of multiple sizes and shapes. Changing over from one product or bottle to another means stopping production on the liquid filler. These machines include simple adjustments to minimize downtime and maximize production. Fill heads can typically be moved using simple fingertip adjustment knobs, while power height comes standard on automatic equipment, allowing up and down movement with the flip of a switch. Even auxillary equipment such as power conveyors include knob adjustments or other simple components for railing and other changes. Other adjustments, such as time and delay settings, can easily be made from the operator control panel, discussed in more detail below.

Gravity filling is the simplest filling method. The uncomplicated construction and operation of gravity filling machines permits them to run with a minimum of maintenance. The supply tank (more properly called the filler bowl) is the upper, central part of the machine. Filling stems are attached to the bottom surface of the bowl at each container filling point. A vent tube extends upward into the filler bowl to a point above the liquid level. To begin the filling operation, the container is raised by the platform until it contacts the filling stem. The platform then continues to raise the container against the stem, opening the filling valve. With the filling valve open, the liquid drains into the container. The air in the container flows out trough the vent tube into the space above the liquid in the filler bowl. Although the container becomes filled, the liquid continues to flow in. The excess fluid rises in the vent tube until it reaches the same height as the liquid level in the bowl. Because the vent tube extends above the bowl liquid level, there is no overflow of liquid from the container into the bowl. If the product is foamy, the foam will rise in the vent tube above the liquid level in the bowl. If it is stable foam and will not break down, it will ultimately overflow into the bowl. For this reason, gravity fillers are not often used for foamy products. At the predetermined time after the container is filled, it is lowered from its filling position, closing the filling valve. Liquid left in the filling stem is removed from the vent tube in several ways. For most applications the liquid will fill drain into the next container. For high viscosity (thick) liquids, the vent tube is usually brought out beyond the side or top of the bowl. Here its outer end can be connected to a device that applies pressure or vacuum to the liquid in the tube to assist in the liquid removal. The total differential pressure that allows the fluid to flow is caused by the gravity head pressure in the bowl. This is usually no more than two or three feet of head, or about one psi. On this basis, it can be seen that these fillers will not permit rapid filling of viscous liquids unless they have larger diameter filling stems. To accommodate the stem, the container must also have a large neck opening; otherwise machine modifications have to be made. ElGravity 150×150 Gravity Filling Machine PrinciplesAnother type of gravity filler uses electronics. It consists of a fixed liquid reservoir or bowl with open-end filling stems. The containers are conveyed on the filling line with an intermittent motion, stopping beneath the filling stems. Inside each filling stem is a ball check connected to a long rod. A pencil shaped magnetic block is attached to the top of the rod and passes through a magnetic coil. As the container moves under the stem, it is detected by a sensing device such as a limit switch or electric eye. This device stops the conveyor, and energizes the magnetic coil. The magnetic field causes the magnetic blocks to lift, raising the rod and the ball check from its seat inside the stem. The rate and amount of fill is controlled by the size of the stem orifice and time delay relay connected to the magnetic coil. Because a direct insertion filling tube is not used on this type of gravity filler the filling stem orifice must be smaller than the inside diameter of the container being filled. On small size containers a more positive means for positioning the bottle beneath the filling stem is used. Fill Height Control In addition to controlling fluid flow, control of the filling height is also important. In general filling machines that elevate the container control the fill height from the bottom of the bottle to the liquid level. The rise of the container is positive, and variations in overall container height are compensated for by greater or lesser seal compression. On rising container machines, a compression spring is often built into the tray elevating mechanism. In this case, container height variations are compensated for by the spring, and the fill height is then controlled from the top of the bottle to the liquid level. Controlling the fluid level from the top can be important if the bottle to be filled has square shoulders, because even a slight under fill is noticeable. In rising stem fillers, variation in container height is taken up by the stem itself. It is usually lowered by gravity or light spring pressure, so the fill height is controlled from the top of the bottle to the liquid level. If the product contains a volatile liquid, such as alcohol, control of the fill height is especially important. In this instance, excessive headspace could allow dangerous vapors to form and the bottle would possibly burst if it were stored in a hot warehouse. Therefore, controlling the fill height is an important function of the filling machine. Normally, a fill height tolerance of 1/32″ is acceptable. Container Control There are several devices used to control the containers coming into the filling area. Included are star wheels, worm or screw sorters, and lug chains. They can be used independently or in combination, depending on the type of container, the filling machine, and the product being placed in the container. The majority of all liquid filling machines operate as continuous filling devices. In most applications the machine has a large rotating filling head, which must be constantly supplied with containers. This is accomplished by a continuously running flat top chain conveyor feeding a star wheel or lead screw device. From here the containers are fed into the filling section. Star wheels when used alone separate the containers so they will be properly located beneath the filling stem. They can be made to handle a variety of container designs, although in some cases, the containers may have to be guided into the star wheel to ensure proper separation. Worm sorters are often used to guide containers into a star wheel. They can be short in length and only located near the machine in feed, or they may be full length of the machine’s main conveyor. The amount of container control determines the worm length. In most cases, worm sorters are very much like a wood screw; starting out small in diameter and then increasing to full diameter. A continuous pocket is formed at the root between the raised portion or crest of the thread. This pocket carries the container into its position on the filling machine by a rotating action. Because each container is different in design, worm sorters are usually made for individual applications and are not an “off-the-shelf” item. Lugged chains are normally used with inclined conveyors and semiautomatic filling machines. These machines can be either continuous or intermittent motion devices. The chain lugs are spaced to match the filling nozzles or stems. For example, if the filling stems are on four-inch centers. The chain is adjustable at the drive sprocket for timing purpose only. Position adjustments are usually made by moving the filling heads. Whatever method is used for container control, it is an important part of proper machine operation.