The friction coefficient is the ratio of the force of friction between two surfaces to the force acting vertically on one surface. It has nothing to do with the size of the contact area and everything to do with how rough the surface is. Sliding friction is caused when two things that are touching each other slide against each other. It can be split into two groups based on how things move: dynamic friction coefficient and static friction coefficient.

If the two surfaces don’t move, there will be a strong binding force, called a “static friction force,” at the point where the two surfaces touch. Unless the force that holds them together is broken, one surface can move to the other. The static friction coefficient (s) is the ratio of the breaking binding force (the force before movement) to the vertical force on one surface.

A dynamic friction coefficient is the ratio between friction and positive pressure when two things that are touching move relative to each other. When something is moving horizontally, positive pressure is the same as gravity. The coefficient of dynamic friction is different for things made of different materials. The dynamic friction coefficient goes up as the object gets rougher.

When looking into plastic packaging films, the coefficient of friction is an important measure. Because friction in the packaging process is often both power and resistance, its size should be kept within a certain range. Most of the time, the internal and external friction coefficients of the film must be between 0.2 and 0.4, and the external/external friction coefficient must be higher than the internal/internal friction coefficient. When a film or sheet slides on itself or on something else, this can also be used to measure how well it resists friction.

The friction coefficient tester can be used to measure both the static and dynamic friction coefficients. It can measure the static friction coefficient and the dynamic friction coefficient when plastic film and sheet, rubber, paper, paperboard, woven bags, fabric styles, metal composite belts for communication cable and optical cable, conveyor belts, wood, coating, wiper, shoe material, tire, and other materials slide.

Classification of friction coefficient tester

According to different ways of measuring friction coefficient, friction coefficient testers can be broken down into three types:

Pendulum friction coefficient instrument

The pendulum friction coefficient meter is based on the fact that the potential energy lost by the pendulum is equal to the work done by the rubber sheet at the end of the swing arm to overcome the friction of the road when it slides over the road. It is mostly used to find out the coefficient of friction of asphalt pavements, plastic sites, and marking. The goal of the experiment is to find out how well pavement and pavement materials don’t slip when they are wet. This will be done by measuring the anti-slip value of the pavement.

Test the friction coefficient with the testing machine

The way it works is the same as the way the plane friction coefficient instrument works. There are many different ways to use this technology. It can be made into glass, rubber, paper, film, metal, coatings, and urinary catheters. A vertical testing machine and a platform testing device make up the experimental device. A nylon wire connects the slider to the sensor of the tensile testing machine. The cost of this tool is low. Adding more tools to a normal tensile testing machine is one way to do it, but the error is large.

Plane friction coefficient meter

The instrument is designed according to the test standard for the friction coefficient of film or sheet, but it is not limited to film or sheet. It has been widely used to test the friction coefficient and smoothness of glass, film, rubber, paper, metal materials, coatings, urinary catheters, and so on.

Main factors affecting the friction coefficient of plastics

Effect of additives on friction coefficient

A common way to change the friction coefficient of plastic surfaces is to add additives like smoothing agents and anti-adhesion agents during the making process. For example, adding a smoothing agent to a film can make the surface smoother and lower the friction coefficient of the surface. Also, an antistatic agent is often added because the electrostatic adsorption force changes not only the friction coefficient between films but also a number of other physical properties of materials.

The film surface structure also affects the friction coefficient

If the surface is smoother, the film surfaces will be too close to each other, making it harder to slide. If the surface of the film is a little rough and there is a little space between them, it will be easier for them to slide past each other. Because of this, a rough surface on a film has a low friction coefficient.

Effect of anti-adhesion agent on friction coefficient

Most of the time, the anti-adhesion agent is a solid powder with particles that are between 2 and 4 um in size. When you add it to the surface of the film, it can make a lot of bumps. This makes the contact area between the film layers smaller, which makes the bonding force weaker. They will also slide more easily against each other, which helps to lower the friction coefficient.

Effect of high temperature service conditions on friction coefficient

When the film is actually used, the temperature conditions may be different. Most of the time, the friction coefficient of the film goes up sharply above 30°C because the most common lubricant is close to its melting point and bonds. During the test, the amount of force used changes a lot, which shows that there is either a sliding or a bonding effect.

Application of the friction coefficient tester

On the production line, plastic film and composite film are automatically packaged. This makes the work much more efficient and saves a lot of labor for society. But as efficiency goes up, quality problems like film breaking and slipping get worse. This can cause packaging lines to stop working, which costs printing and packaging companies a lot of money. The main reason is that it is hard to control how much friction plastic film has. Because of this, it’s important to test and process the friction coefficient of plastic film ahead of time so that flow problems on the next production line don’t happen.

The film friction coefficient instrument can be used to measure the static friction coefficient and dynamic friction coefficient of plastic film and sheet (or other similar materials) and can give you a good idea of how smooth and open the film is. It is also called a film friction coefficient tester. The manufacturer can use the detailed record of the test process, the test results, and other data as a guide.

Measurement of the friction coefficient of cloth

People decide whether or not to buy clothes, shoes, and hats based on how they look, how well they are made, how much they cost, how comfortable they are, and other factors. If a fabric’s friction coefficient is high, it will cause more friction on the skin and make clothes feel very uncomfortable. But the friction coefficient of the fabric used to make shoes has a bigger effect on how they feel. The coefficient of friction is way too high. People know that walking for a long time hurts the heels, soles, and other parts of the feet very much. Even if your feet are blistered from grinding, the coefficient of friction is too low, and it’s easy to slip when you walk.

There are many things that affect the friction coefficient of a fabric, such as the shape of the fiber, the twist and shape of the yarn, the way the fabric is put together, as well as how it is treated, dyed, printed, finished, and so on. So, through process optimization of the design and making of the cloth, the cloth has the right friction performance, and a friction coefficient instrument can be used to test the friction coefficient of samples of the cloth.

Measurement of the friction coefficient of BOPP smoke film at high temperatures

In the process of packaging cigarettes, the friction between the cigarette film and the equipment is both powerful and resistant. The friction coefficient of cigarette film is directly linked to how smooth it is. There are two types of friction coefficient: static friction coefficient and dynamic friction coefficient. The static friction coefficient is the amount of friction between two things that are not moving relative to each other. A dynamic friction coefficient is the amount of friction between two things that are moving relative to each other.

To meet the needs of high-speed packaging equipment, it is very important for cigarette packaging to have the right friction coefficient. Based on how cigarettes are packaged, the inside and outside sliding properties of the cigarette film must meet different standards. During the process of packaging cigarettes, the inner layer of the cigarette film touches the box. The inner surface of the cigarette package needs to have a relatively high static friction coefficient so that the cigarette bag and the cigarette film can be placed correctly and the package stays small.

Due to the close contact with metal parts like the lower film channel, the forming wheel groove, the folding plate, the soldering iron, and the guide rail, it is important to have a low friction coefficient for smooth sliding. Also, during the manufacturing process, most of these metal parts work at high temperatures (usually above 50°C), while the polymer materials used in the smoke film start to move on a molecular level, which changes their viscoelastic properties. As the temperature goes up, the commonly used lubricants start to stick together, causing slip adhesion that doesn’t happen all the time. This makes the smoke film operation less smooth, which affects the efficiency and quality of production.

The friction coefficient test can be used to measure the film’s friction coefficient before it goes into production. This is the best way to reduce the risk of the production process as much as possible.

How to use the film friction coefficient tester?

Steps:

1. Fix the test surface of a sample upward and flat on the horizontal test bench. The sample’s and the test bench’s length directions must be parallel.
2. Put the test surface of another sample downward, wrap the slider, and fix the pattern on the front and upper surface of the slider with adhesive tape.
3. It’s common to need two 8 cm samples to measure a 20 cm sample with a friction coefficient If the sample is thick or rigid and must be fixed to the slider with double-sided tape, the size of one sample shall be the same as the bottom size of the slider.
4. Sample cutting: the sample should be cut evenly over the whole width or circumference of the sample (when the pipe film is used.
5. As a kind of precision testing equipment, the friction coefficient testerhas certain requirements for its installation, adjustment, and working environment so as to ensure the accuracy of test results and the normal operation of the testing machine.
• Before unpacking, the user should first check whether the packing box is intact. After opening the packing box, check whether the testing machine and accessories are complete and intact according to the packing list, and then take out the testing machine.
• Place the testing machine on a solid platform and adjust the adjusting nut under the frame to make a horizontal bubble on the frame in the middle.
• Turn on the power switch to start testing. Plug the power cord of the testing machine into the three-core socket of the indoor electricity system and turn it on to start.
1. Test: Turn on the power switch on the rack control board, press the “test” key to enter the display interface. Press the “test” key again, which can be used for the test. The test will stop automatically in 38 seconds. During the test, the testing machine will automatically display the force value curve, calculate the results, and press the “return” key to return to the original position. To print, press the “print” key. If the test piece is tested for the second time, the steps are the same as above.
2. Shutdown: After the test, turn off the power supply.