The hottest design custom fluororubber mixture

2022-07-29
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Design customized fluororubber mixture

customized mixture requires that the physical properties of the developed materials must meet the standards required by customers and products during use. Due to the competitive relationship between different physical properties, the standard is usually difficult to balance, making it difficult to determine an optimized formula that can meet all requirements. In addition, people often need a solution in a very short time

experimental design (DOE) is a way for blenders to meet customer needs. A predictive model can be obtained by using the designed experiment, which can help the mixer better understand how the input variables (such as the composition of the mixture) will affect the output quantities (such as physical properties). Sometimes we may introduce mathematical techniques into designed experiments to deepen our understanding of observed phenomena

many types of experimental designs have been developed. It is worth emphasizing that these designs have their own characteristics when overcoming experimental difficulties. They have a common feature, that is, they need experimenters to design a test plan calmly, then implement the test plan, and finally analyze the experimental results they get. These test plans may be very complex, requiring many test measurements and a lot of man hours in design, implementation and analysis. In addition, if a technical research team led by the factory director, composed of work area technicians and grass-roots managers is established, and the experiment is suspended before the designed matrix is completed, then we may not get a useful model from these data

mixers can use their experience to narrow the scope of experimental design. For example, when the customer needs maximum compression deformation and minimum elongation, the batcher can use his knowledge of the mixture to develop an optimal solution by limiting the input variables to a few known components that can affect the crosslinking density. In this way, we can quickly get a simplified experimental design that can meet a variety of physical performance requirements in a limited time

a method that can be used to replace the experimental design is to do a series of experiments, changing one of the factors each time while keeping the other factors unchanged. 1. The manufacturer is responsible for the installation, commissioning and personnel training of the equipment (referred to as ofaat for short). Although such alternative experiments are reliable, they often give misleading results, especially when there are interactions in the system. Nevertheless, they can help people deepen their understanding and screen some ideas

the blender can also use a "silver bullet" (a synonym for lethal weapons) method to establish a set of experimental methods using previous knowledge. Although this method is easy and fast, the accuracy of the mechanical model is verified by experiments. This technique can only tell us whether a specific mixture can meet the needs, and can only provide very limited guidance to the experimenter

experiment

in each instance, we determine whether we can design an optimized formula that can meet a variety of physical performance requirements by conducting one or a series of well-designed experiments. In most cases, we use a simple 2 x 2 block design

the test mixture was obtained by mixing the commercialized ingredients in a 6 "x 13" laboratory mortar. This standard was first issued in 1989. The tested samples were vulcanized for 10 minutes under laboratory pressure (atmospheric pressure) and 177 ℃, and then re vulcanized under the conditions shown in the table. The physical test is similar to the test process shown below:

astm d-, rubber properties - compression deformation

astm D-A, vulcanized rubber and thermoplastic elastomer - tension

astm d-, measure the vulcanization effect with a vibrating disc vulcanizer

astm d-, tear strength of general purpose vulcanized rubber and thermoplastic elastomer

astm d-, rubber properties - Hardness of durometer

astm d-, the rheological properties of unvulcanized rubber were measured with a Rotorless Shear Rheometer

in each example, the test program is debugged according to the actual situation to meet the needs of different experiments. In most cases, each experiment was completed within a week

results and discussion

◆ case 1

in this example, the customer requested to obtain a "GF" mixture with a hardness of 85 (ASTM D-2000 classification), with good rubber metal adhesion and appropriate tear strength. It is known that metal oxides can affect the rubber metal adhesion of fluoroelastomer mixtures, while carbon black can affect their tear strength. Here we designed a 2 x 2 block experiment to demonstrate the effects of these two factors - metal oxide and carbon black on the properties of the materials

3 mixture shows the best tear strength and comprehensive performance. We take samples from it to the customer for product evaluation. The customer said that the mixture showed good adhesion during their processing

◆ case 2

in this example, the customer provided a formula and a set of physical properties to be achieved. In the initial test, the mixture did not meet the physical performance standards required by the customer. Therefore, we conducted a design experiment using their formula to study the influence of the time and temperature of secondary vulcanization on the physical properties of the final product

this design is a 2 x 2 block design with a central point. The time (6 and 24 hours) and temperature (177 and 232 ℃) selected here include the range of reported secondary vulcanization conditions similar to fluororubber mixture system. According to the customer's requirements, we added the sixth point (secondary vulcanization at 121 ℃ for 12 hours). The primary purpose of this study is to increase the constant tensile strength (100% modulus) value, while the secondary purpose is to meet the physical performance requirements mentioned above

since the purpose of this study is to maximize the modulus, we use graphical method instead of strict mathematical analysis. Some general tendencies are listed below:

☆ the influence of temperature is greater than that of time

☆ in all test conditions, the tensile strength and elongation exceed the target value

☆ elongation decreases with the increase of secondary vulcanization temperature

☆ the compression deformation is larger than the target value, and we are surprised to find that its value is not affected by the secondary vulcanization conditions

☆ in all tested samples, the modulus of the mixture did not reach the target value

☆ the modulus seems to increase with the increase of secondary vulcanization temperature

adjusting the secondary vulcanization conditions can not make the mixture meet the customer's requirements for its physical properties. Therefore, it is obvious that we must study other factors to meet customers' requirements for material properties

◆ case 3

in this case, the customer requested to obtain a mixture with a set of specific physical properties, including constant tensile strength (100% modulus) and elongation at break. The target value proposed by the customer is relatively high for fluororubber. In addition, the customer also specified the material of the mixture, which must contain at least 60% of the polymer, even though the composition is limited to 166.67 parts (pphr) of the mixture per 100 parts of rubber. The customer didn't specify the vulcanization conditions. We tested the samples after pressure vulcanization and secondary vulcanization in order to meet the customer's requirements. A variety of experimental techniques have been applied to this case to meet customers' requirements for product performance

the first design experiment in this project is a two factor and two-level factorial design, in which two factors refer to polymers and vulcanization types

adding the terpolymer fluororubber (viton-b rubber) to the formula can improve the durometer hardness and specific gravity of the mixture, and reduce the tensile strength. The type of replacement vulcanizing agent has little effect on the physical properties of the product. The hardness of all the tested mixtures did not reach the target value, so we had to carry out another study

the design experiment shows that changing the polymer and vulcanization type does not greatly improve the physical properties of the product, so we adjusted the filler based on the original polymer and vulcanization type, and established a "silver bullet" test, in order to quickly get a satisfactory solution. The modulus and elongation of the two mixtures are closer to the customer's requirements, but the two mixtures still can not meet all the physical performance standards

since no satisfactory solution has been obtained, we have conducted a single factor (mineral filler) screening experiment to determine which mineral filler can comprehensively improve the physical properties of the mixture to meet the needs of customers. The common mineral fillers used in fluororubber mixtures were compared under the same loading amount, and the silica with high specific surface area was compared under the lower loading amount. The results of the filler study are summarized in Table 5

some fillers will block the cross-linking reaction in the mixture. In order to complete the cross-linking of the mixture within 10 minutes at 177 ℃, we added another vulcanizing agent. As expected, none of the mixtures achieved all the target values. However, this experiment shows us which filler will increase the modulus of the product and how it affects other properties of the product

through a three factor, two-level factorial design experiment, we further tested the effect of fillers on the performance of the mixture. The three factors are: the surface area of silica filler, the amount of vulcanizing agent, the silylation of primary mineral filler and calcium silicate. The experimental design, the formula of the mixture and the test results of the physical properties of the product are listed in Table 6. Although no mixture can meet all physical performance requirements under given vulcanization conditions, we can still see that the results of some schemes are very close, and the influence of each input variable can be quantified from these data. The mixture E7 meets the requirements of modulus and tensile strength and exhibits good elongation properties

mixture F2 is an improved product based on mixture E7. It uses another source of high specific surface area silica to replace the original corresponding components, and adjusts the composition of calcium silicate to make the mixture meet the target value of hardness of durometer. In addition to elongation at break, the mixture meets all other physical property requirements. The customer also accepted the mixture for molding test and product evaluation

◆ case 4

after blending, the hardness of most fluororubber polymers will be more than 50. The mixture formula with a hardness target value of 45 will contain a small amount of fillers, and most of these fillers are acid receptors required for vulcanization reaction. The two acid receptors commonly used in fluororubber mixtures are calcium hydride and highly active magnesium oxide. We conducted a two factor and two level factorial experiment to prove the effect of these two metal oxides on the physical properties of 45 hardness fluororubber mixture

mixture B was reacted at 177 ℃ for 10 minutes, but was not completely vulcanized. In mixtures D and E, the higher filler content increases the durometer hardness of the mixture to the target value range of 45 hardness level (45 ±

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