Glossary

INDEX
? Asker C

? Coefficient of thermal conductivity
? Complex shear rate
? Compression Set
? Conductivity=a/a0
? Conductivity (dB)
? Cone penetration
? Convective Heat Transfer
? Crosslinking

? Dielectric breakdown strength
? Dielectric constant
? Dielectric dissipation factor
? Dilatancy

? Electromagnetic Waves
? Electromagnetic Waves in Everyday Life
? Ethylene Propylene Rubber
? Evaluation Method for Actual Vibration Damping Ability

? Frequency Ratio (f/f0)

? G
? Gel
? Glass Transition Point / Melting Point
? Hydrolysis

? Impulse Force
? Internal damping

? Loss factor (tanδ)
? Low-molecular-weight siloxane

? Magnetic permeability
? Methods of Electromagnetic Shielding
? Modulus of resilience

? Natural Frequency
? Natural Frequency and Vibration Damping
? Needle Penetration

? Oil Bleed, Silicone Oil

? Polymers

? Resonance/
  resonance amplification
? Selecting the Best Material for Electromagnetic Shielding
? Silicon and Silicone
? Specific Heat
? Shock and Shock Absorption
? Styrene-butadiene Rubber

? Tensile Strength
? Thermal resistance

? Vibration Decoupling
? Vibration Damping
? Volume Resistance

? What makes a good heat dissipation sheet?

? Young's modulus
  (Modulus of elasticity in tension)

Asker C

Asker C is a measuring device to measure hardness with a durometer (a spring hardness scale) as stipulated in SRIS0101 (SRIS: Society of Rubber Industry [Japan] Standards) .

When a 20 is listed for Asker C in a physical properties chart, this indicates that the value measured with the Asker C hardness scale is 20. In contrast to a needle penetration test or cone penetration test, larger numbers indicate a harder material.

Similar hardness measurement devices include the JIS K6253 durometer (JIS A durometer) and Asker F.

A JIS A durometer is used to measure the hardness of rubber and is the same as a Shore A durometer. Asker C is a hardness scale used to measure materials that are harder than those measured in a needle penetration test and softer than those for a JIS A durometer.

Coefficient of thermal conductivity

If a temperature difference is present in a substance, then the movement of heat will occur from portions with higher temperatures to those with lower temperatures. Coefficient of thermal conductivity is a coefficient that indicates how easily this movement of heat occurs, so when a temperature difference of 1℃ per unit length (thickness) exists, this is the amount of heat that moves a unit area in a unit time. In other words, when the difference in temperatures for surface A (TA) and surface B (TB) in a 1m³ cube with a volume as indicated in Figure A is 1℃ (TA > TB) , the amount of heat to move 1 m (Aright arrowB) in 1 second is the coefficient of thermal conductivity. Units are indicated in J · m/s · m2 · ℃, W/m · K, or W/m · ℃. The larger the value for coefficient of thermal conductivity, the greater the amount of heat that moves, which means that heat will be easily transferred. Thus, a substance with a large thermal conductivity is preferred as a heat conductor. However, thermal conductivity is given in values for unit length, so even if a substance has a large thermal conductivity, heat-conducting action will decrease if the length (thickness) actually used is greater.
For example, heat-conducting action will be the same for a heat conductor where the thickness is 10 mm with a coefficient of thermal conductivity of 10 W/m · K and a heat conductor where the thickness is 1 mm with a coefficient of thermal conductivity of 1 W/m · K. In addition, coefficient of thermal conductivity is a specific value (physical property) for a substance, and it generally varies according to the temperature. For example, the coefficient of thermal conductivity of air increases with temperature, while the coefficient of thermal conductivity of a metal tends to decrease with a rise in temperature.

Complex shear rate

The complex shear ratio indicates the hardness of a material. It is the elasticity determined when applying (dynamically) sinusoid ally varying force and is a value that will serve as the basis of a vibration insulator design or shock-absorber design.Dynamic elasticity in the direction of compression is indicated by E* (complex compressive elasticity modulus) ; dynamic elasticity in the direction of shearing is indicated by G* (complex shear rate) .

3G*=E*

G* can be broken down into G' (storage shear rate) and G" (loss shear rate) . G' indicates the spring component that a material has (elastic body) ; G" indicates the liquid component (viscous body) .

These values are determined by a dynamic viscosity measurement equipment and will be:

Compression Set

Compression set is the permanent set due to heated compression of a rubber material. A small value indicates that material has a strong ability to recover when compressed for a long period of time. This can be evaluated by tests based on JIS K 6262 standards. A cylinder-shaped test piece is subjected to compressive strain corresponding to 25% of the thickness; after the test piece is kept for a fixed time at high temperatures, it is removed and the thickness is measured after 30 minutes. The compression set rate Cs (%) is indicated by the following equation:

t0: Prior thickness of a test piece (mm)
t1: Spacer thickness (mm)
t2: Thickness (mm) of a test piece 30 min. after removing it from compression equipment

Generally, higher compressibility and test temperatures will mean a greater compression set.At our firm, a given material is compressed at an atmospheric temperature of 100℃ and compression is released after retention for 70 hours; compression set is then calculated after 30 minutes at normal temperatures.

Conductivity=a/a0

a0: Forced displacement of the foundation, or velocity, acceleration
a: Displacement of the machine or speed, acceleration

Conductivity (dB)

When precision machinery is supported by vibration insulators, the proportion of the base frequency transferred to machinery is called the vibration conductivitytau. A dB value is often used to indicate conductivity.

tau  :  Vibration conductivity
a0  :  Forced displacement of the base (or speed and acceleration)
a  :  Mechanical displacement (or speed and acceleration)

When, for example, the vibration conductivity (tau) is 2, it is noted in dB as 6 dB.Every time the conductivity is increased 10-fold, the dB value increases by 20; when it is 1/10, the dB value decreases by 20.

(tau-dB conversion chart)

dB value tau dB value
1 0 dB 0.5 -6 dB
2 6 dB 0.1 -20 dB
10 20 dB 0.01 -40 dB
100 40 dB    

Cone penetration

The complex shear ratio indicates the hardness of a material. It is the elasticity determined when applying (dynamically) sinusoid ally varying force and is a value that will serve as the basis of a vibration insulator design or shock-absorber design.Dynamic elasticity in the direction of compression is indicated by E* (complex compressive elasticity modulus) ; dynamic elasticity in the direction of shearing is indicated by G* (complex shear rate) .

A cone penetration test is a method of measuring the hardness of a material.
Measurement is standardized in JIS K2220; a fixed cone is entered into a test piece to indicate the hardness of a material determined from the length it entered. The cone penetration value is given where 1/10 mm is a cone penetration of 1.
Larger numbers mean that a material is more pliable; this method is used to measure materials that are softer than those subject to a needle penetration test.

Convective Heat Transfer

A method of heat transfer using the molecular movement of fluids such as air and water. An example of this method is a fan cooling a heat sink.

Crosslinking

Crosslinking generally refers to the creation of a network among polymers. Reactions that result in crosslinking include additive reactions with double bonds and condensation reactions in which water or alcohol groups split off. As crosslinking progresses, polymers normally harden, and the substance becomes less soluble. In 1839, Charles Goodyear laid the foundation of modern rubber, when he discovered that soft, hard to use natural rubber could be hardened by adding sulfur, which achieves crosslinking within the material. Crosslinking in rubber caused by sulfur is called vulcanization.

Dielectric breakdown strength

Dielectric breakdown is the name of the phenomenon occurring when the voltage applied to an insulator exceeds certain limits; the insulator breaks down electrically and insulating properties are lost so that voltage flows. The voltage at this point is called the dielectric breakdown voltage; the value given by dividing the dielectric breakdown voltage by the material thickness is called the dielectric breakdown strength. Units are indicated in kV/mm; this is a specific value for a substance, but the value can decrease when air bubbles are introduced in the material and when the material absorbs moisture. A substance with a large dielectric breakdown strength is preferred as an insulator.

Dielectric constant

The dielectric constant is the ease of polarization (indicating the size of the quantity of electricity stored) and is a standard used to evaluate its performance as an insulator.

Using an example of a condenser, an insulator is placed between pole plates and voltage is applied, electricity will not flow, though a phenomenon called polarization where positive and negative charges in molecules separate will occur, so electricity will be stored. At this point, the quantity of electricity stored is proportional to the intensity of the magnetic field and area of the pole plates, so it will increase; the rate of change in this event is called the dielectric constant. If the dielectric constant increases, the quantity of electricity stored will increase.

Generally, specific inductive capacity (ratio of the dielectric constant of an insulator and the dielectric constant of a vacuum) is used rather than the dielectric constant. Having a small specific inductive capacity is preferred for an insulator.

In addition, this value is dependent on the frequency and temperature, so care must be taken upon usage.

Dielectric dissipation factor

The dielectric dissipation factor is the degree of electrical energy loss in an insulator and is a standard used to evaluate its performance as an insulator.

Applying alternating voltage to an insulator causes a phenomenon called dielectric loss where a portion of the electrical energy in an insulator is changed to heat energy because particles are vibrating (a type of resistance) , and heat is produced. The dielectric loss tangent (ratio of the charged current and current lost) is used as a standard for the degree of electrical energy loss in this event. With an ideal insulator, the electrical energy loss would be 0, so having a small dielectric dissipation factor is preferred for an insulator.

In addition, this value is dependent on the applied frequency and temperature, so the individual dielectric dissipation factor is given in a test by changing the frequency.

Dilatancy

Water mixed with cornstarch at a ratio of 1:1 hardens when gripped strongly, but when placed on a desk, flows like a liquid. This property is called dilatancy, which is a property of a non-Newtonian fluid. In other words, an object with dilatancy responds like a solid to a fast, external force and responds like a liquid to a slow, external force.
Since these fluids harden in response to high-speed external forces, it is expected that they also be resistant against sudden shock. There have been attempts to utilize this property to make bulletproof vests.
Originally, dilatant meant “expanding,” which was chosen to describe the strange expansion which occurs when pressure is applied to a liquid in which powder is dispersed. When walking on a wet sandy beach, it appears as though the area around your foot dries out when stepped on. Actually, the sand is expanding due to the applied pressure; the gap between the sand grains increases, causing the water to drop below the surface of the sand.

Electromagnetic Waves

Invisible waves consisting of an oscillating electric and magnetic field.
These two fields interact with each other, with changes in the electric field creating a new magnetic field, and changes in the magnetic field creating a new electric field.
Electromagnetic waves are generated when an electric field and a magnetic field interact with each other.
Electromagnetic waves are periodic, and the number of oscillations per second is called frequency, which is measured in hertz (Hz).
High frequency waves have short periods and are strongly rectilinear. The properties of an electromagnetic wave depend on its frequency.
The following are types of electromagnetic waves in descending order of frequency: gamma rays, X-rays, ultraviolet light, visible light, infrared light, microwaves, and radio waves.

Electromagnetic Waves in Everyday Life

The most widely used electromagnetic waves in everyday life (other than visible light) are radio waves, which have frequencies of 3,000 GHz or less.
They are widely used in various industries such as broadcasting, telecommunications, weather forecasting, radar on aircrafts and marine vessels, home, medical, and industrial electronics, and construction.
Because of their many applications, concerns have been raised about the influence of radio waves on the human body.
High frequency electromagnetic waves such as gamma rays and X-rays affect the human body, but there is no proof that radio waves have any effect on the human body.
Unlike the human body, advanced medical devices and precision electronics include many electronic circuits, which can be affected even by weak radio waves.

Ethylene Propylene Rubber

Ethylene propylene rubber (EPDM) is a synthetic rubber, which is synthesized through the copolymerization of general use plastics ethylene and propylene. The American Society for Testing Materials (ASTM) code is EMP.

Ethylene and propylene are both plastics on their own. However, when copolymerized, the resulting material has a heterogeneous structure, which has rubber-like characteristic.
Radical cross-linking can be achieved with peroxides, however there are also types of ethylene propylene rubber which achieve cross-linking by copolymerizing with a third component which includes a double bond; these are called ethylene propylene diene monomer rubbers (EPDM or EPT). This process is called coordinated ionic polymerization.

Evaluation Method for Actual Vibration Damping Ability

The vibration ability of a material can be evaluated by measuring vibration in a certain piece of equipment before and after installing the vibration damping material.
For the prediction of the vibration damping effect of a particular material after installation in a compact device and also, as a reference during vibration damper design, a vibration generator is used to measure the vibration damping properties of the material.
Taica offers consultation on measurement methods for vibration damping.

Frequency Ratio (f/f0)

f: base vibration frequency
f0: natural frequency

G

G is a way to express the magnitude of acceleration. 1 G is equal to the acceleration due to gravity on the earth (9.8 m/s²). Therefore XG represents multiples of the acceleration due to gravity.
For example:
An acceleration of 200 m/s² is therefore equal to 200(m/s²) ÷9.8(m/s²)= approximately 20G.
When speaking of shock, G represents the maximum impact acceleration experienced by a body upon impact. Note that G is not an SI unit.

Gel

A network of polymer chains created by crosslinking is generally called a gel. Gels are non-fluids, which swell, but do not dissolve, upon contact with solvents. There are different types of crosslinking, including covalent bonds, coordinate bonds, and hydrogen bonds.
Network structured gels that contain water or organic solvents are called hydrogels and organogels, respectively. Aerogels (also called xerogels) are highly porous and light materials, in which the dispersion medium, such as water, has been dried off.
Examples of foods which are also water containing gels are agar-agar, tofu, konnyaku and jelly. The word "gel" derives from the Latin verb "gelare (to freeze)." In contrast to hardened gels, a fluid colloidal solution is called a sol. One example of this is the sol-gel process, which synthesizes ceramic out of a colloidal solution of a precursor, such as metal alkoxide. When superabsorbent polymers were invented in the 1970s and products such as paper diapers entered the market, hydrogels received a lot of attention. Furthermore, polymer gel research advanced greatly in 1978, when Toyoichi Tanaka discovered the phase transition phenomenon.
Silicone polymers where crosslinking has occurred within silicone oil are called elastomers. Soft elastomers which contain silicone oil where crosslinking has only partially occurred are sometimes called silicone gels.
Silicone gels display exceptional shock absorption and vibration damping properties.

Glass Transition Point / Melting Point

The melting point describes the temperature at which a material changes from a solid to a liquid. For most materials, the melting point is the same as the freezing point, at which liquids change into solids.
However, there is another phenomenon seen in inorganic glass, plastic, rubber, and other polymers, called the glass transition point.
For these substances, the temperature below the melting point at which regular crystalline structures do not form, liquid motion stops, is called the glass transition point (Tg).
The glass transition point of polymers is defined as the temperature at which free volume increases and Brownian motion commences. At temperatures below their glass transition points, plastics and glass become brittle. Their physical properties, including elasticity and dielectric permittivity, drastically differ above and below this point.

Hydrolysis

Hydrolysis is a reaction where a product can be obtained by the reaction of a starting material and water. Here are some examples of hydrolysis:
ester + water → alcohol + carboxylic acid
amide + water → amine + carboxylic acid
The breakdown of proteins into amino acids in organisms is a type of hydrolysis facilitated by enzymes.
Organic polymers are prone to hydrolytic degradation. For example, polyurethane readily succumbs to hydrolysis, whereas silicone polymers show quite high hydrolytic resistance.

Impulse Force

Impulse force is equal to the maximum acceleration an object experiences in G multiplied by the object’s energy. The unit is Newton (N).

Internal damping

Loss factor (tangent) is used to indicate the size of internal damping (refer to "Loss factor" in Vocabulary)

 : Conductivity during resonance (resonace amplification)

A larger loss factor means that the internal damping of a vibration insulator will be greater. The conductivity (resonance amplification) of a vibration insulator during resonance will decrease.

Loss factor

G"/G'- the ratio of the storage shear rate (G') and loss shear rate (G") is called the loss tangent (loss factor) and is expressed as tangent. It indicates how much energy is absorbed (changed into heat) by a material when it deforms.

G"/G'- the ratio of the storage shear rate (G') and loss shear rate (G") is called the loss tangent (loss factor) and is expressed as tangent. It indicates how much energy is absorbed (changed into heat) by a material when it deforms.

Larger values for tangent mean that more energy is absorbed. In a shock absorption test, the modulus of resilience will decrease; in an agitation test, resonance amplification will decrease.

Low-molecular-weight siloxane

A dimethyl polysiloxane, which is a main component of silicone products, with a low molecular weight and where both ends form a ring is called cyclic polysiloxane. This low-molecular-weight siloxane (cyclic polysiloxane) is, depending on the number of Si atoms, called D3, D4, D5 ・ ・ ・ (the figure is D3) . With a lower D, low-molecular-weight siloxane has smaller molecular weight and therefore more volatile. However, D3 is extremely volatile, so it is not included in silicon products.

Cyclic polysiloxane(D3)

Magnetic permeability

Magnetic permeability is the ease of passing through a material's magnetic flux (the ease of magnetization) . This is one of the standards of evaluating magnetic absorption in applications for electromagnetic wave absorption.

When a substance is placed in space where magnetism is acting (a magnetic field) , it more or less takes on magnetism and becomes a magnet. At this point, increasing the intensity of the magnetic field means that magnetic flux density in a substance (indicating intensity as a magnet) will increase since it is also proportional, though the rate of change in this event is called the magnetic permeability. When magnetic permeability is greater, magnetic flux density will increase. In other words, when the magnetic flux passing though a substance, increases, its intensity as a magnet increase.

Generally, specific magnetic permeability (ratio of the magnetic permeability of a substance and magnetic permeability of a vacuum) is used rather than magnetic permeability. Magnetic flux does not readily pass through a substance with a low specific magnetic permeability like aluminum and, since it penetrates through, magnetic absorption will decrease. In contrast, magnetic flux readily passes through a substance with a high specific magnetic permeability like ferrite, so magnetic absorption will increase.

Methods of Electromagnetic Shielding

Along with the Digital Revolution came the problem of malfunctioning electronic equipment caused by electromagnetic noise (unnecessary electromagnetic waves) and other electromagnetic interference.
There are two ways to protect electronics from electromagnetic interference: reflection and absorption. Shielding electronics with highly conductive metal is the most popular method.
However, reflected electromagnetic waves might adversely affect other equipment, or, if the reflected electromagnetic waves are not allowed to escape the device, they may be reflected back into device, which could adversely affect the electronics within.
Therefore, considering the negative influence of reflected waves on other equipment or the devices themselves, it is more advisable to absorb electromagnetic waves rather than to reflect them.

Modulus of resilience

The modulus of resilience is an indicator of the energy a material absorbs during the impact of an object. It is the ratio of energy an object has during impact and rebound when a test piece is struck by a falling object with a given mass from a given height.

Measurement of the modulus of resilience is standardized in JIS K 6255 and can be a Lupke impact resilience test using a pendulum to calculate the value from the drop and rebound height and a tripso-impact resilience test using a solid disk to calculate the value from drop and rebound angles.

A load W is dropped from a height h1 and strikes a test piece, bouncing to height h2, the energy E absorbed by the rubber material and the modulus of resilience R (%) are indicated in the following equations:

The modulus of resilience can be calculated from these equations if the drop and rebound heights are measured.

At R=0 (%) , a dropped object will stop without bouncing back; at R=100 (%) , it will bounce back to the same position as that from where it was dropped. In addition, (100-R) % will be converted to heat energy by the friction in the rubber. The modulus of resilience for a common rubber material will be markedly affected by the temperature, though our firm's gel is slightly affected by temperature as well as having a higher level of damping.

Natural Frequency

The natural frequency f0 of a vibrating system (where a weight is mounted on two vibration aborbers) is a fixed value, which is determined by the spring constant k of the vibration absorber and the mass m of the applied load.

Natural Frequency and Vibration Damping

The ratio of vibration frequency f and the natural frequency f0 f/f0 is called the frequency ratio. To achieve effective vibration damping, the frequency ratio needs to exceed 1. The higher than 1 the frequency ratio is, the lower the transmitted vibration, and therefore the higher the vibration damping capacity of the material.
Hence it is important to keep the value of the natural frequency as low as possible. In this case, the natural frequency is the ratio of the spring constant of the vibration absorber to the load weight.
It is important to choose a vibration absorber with a spring constant appropriate to the load applied.

Needle Penetration

A needle penetration test is a method of measuring the hardness of a material.
Measurement is standardized in JIS K2207; a needle of fixed weight is entered vertically into a test piece to indicate the hardness of a material determined from the length it entered. The needle penetration value is given where 1/10 mm is a needle penetration of 1.
Larger numbers mean that a material is more pliable.

Oil Bleed, Silicone Oil

Certain plastics and rubbers are softened by the addition of oils (plasticizers) to their base mixture. When used, plasticizers can separate and bleed out of the material surface. This is called bleeding or oil bleed. There is a similar phenomenon called blooming, when solid additives appear as a powder on the material surface.
Bleeding and blooming are usually avoided due to their negative effect on the appearance and texture of materials. However, there are also silicone products which use these phenomena to their advantage. For example, self-lubrication can be achieved by mixing incompatible silicone oils, which produces continuous oil bleeding in the product.

Polymers

Long molecular chains connected by covalent bonds are called polymers.
Carbon forms covalent bonds with other carbon atoms creating chains (catenation: bonding of atoms of the same element) which results in polyethylene and many other polymers. Most polymers derive from carbon or hydrogen atoms, but other elements, such as oxygen, nitrogen, and silicon are also capable of building polymeric frameworks.
Polymers in organisms, such as proteins, nucleic acids, and cellulose, have important functions as structural materials, DNA carriers, and catalysts. Polymers have been used by humans since time immemorial, but the scientific concept was first elucidated by Hermann Staudinger in the 1920s.
The linking of individual molecules to form polymers is called a polymerization reaction. There are several kinds of polymerization, including addition polymerization, condensation polymerization, and ring-opening polymerization. Synthetic polymers are subject to molecular weight distribution, and their viscosity and thermal characteristics differ greatly from those of low-molecular-weight compounds.

Resonance/resonance amplification

Resonance is the name of a phenomenon occurring when amplitudes in the vicinity of a Specific Heat (refer to "Specific Heat" in Vocabulary) of a vibrating system (a system formed by a vibration insulator and weight resting on the vibration insulator) are amplified when the size of vibrations forcibly applied from the outside is uniform and frequency varies. Conductivity during resonance for a vibration insulator is called the resonance tau.

tau  :  Vibration conductivity
a0  :  Forced displacement of the base (or speed and acceleration)
a  :  Mechanical displacement (or speed and acceleration)

Selecting the Best Material for Electromagnetic Shielding

1. Shielding from external electromagnetic waves
Electromagnetic waves can spread into a wide range of frequencies, so protective materials which can reflect or absorb frequencies near the center of the frequency band are selected.
2. Protecting the external environment from electromagnetic waves generated inside the device
When using only reflective protection, interference between internal circuits is likely to occur. Therefore, it is necessary also to use absorbers to absorb the reflected waves.

Silicon and Silicone

Silicon refers to the element Si, atomic number 14. In a highly pure form, silicon is used as a semiconductive material. Silicon is an extremely abundant element in the earth's crust and it can mainly be found in the compound silicon dioxide (SiO2).
Silicone (with an "e" at the end), however is a polymer with a structure as seen in Diagram 3 and is completely different from the elemental silicon.
The term “silicone” was coined by Frederic Stanley Kipping (1863-1949), who laid the foundations of silicon chemistry in England from the late 19th century to the early 20th century. Kipping aimed to create a silicon-based compound that corresponded to the ketone benzophenone. He called the result silicoketone, which was eventually abbreviated to “silicone”.

However, unable to form the desired chemical structure (Diagram 2), it is said that, in disappointment, he threw out the resultant oil-like material (Diagram 3) which kept forming in his trials.
After that, a method for mass producing organic silicon compounds was established in the U.S. During World War 2, demand for high quality rubber and resin increased, and silicone polymers with outstanding properties and structures (Diagram 3) were developed quickly to meet that need.
Silicone comes in many shapes and forms, such as oil, gel, rubber, or resin, each of which have different properties. It is used in numerous applications as a lubricant, sealant, and even as tableware. Silicone polymers have excellent cold, heat, weather and electrical resistance, act as absorbers and are non-toxic.

Specific Heat

Specific heat is the amount of heat required to raise the temperature of 1 kg of a substance by 1 ℃. Units are indicated in J/kg ・ ℃ or J/kg ・ K. In other words, having a larger specific heat means that the amount of heat to raise the temperature will be greater, so a substance with a larger specific heat will be harder to heat or cool.

Shock and Shock Absorption

Shock is an impulse force created by sudden acceleration caused by an object at rest suddenly moving, or a moving object suddenly stopping. Shock absorption is the poperty of decreasing the impulse force to as low a value as possible.

Styrene-butadiene Rubber

Styrene-butadiene rubber (SBR) is a rubber with styrene and butadiene as its main components and which represents 80% of all synthetic rubber produced in the world. First developed in Germany in 1930 as “Buna S”, it became widely used as automobiles became popular.
Manufacturing methods include emulsion polymerization and solution polymerization. SBR derived from the standard emulsion polymerization method generally has a styrene content of 23.5%. When using emulsion polymerization, the proportion of butadiene bonds varies depending on the reaction temperature. When synthesized at low temperature (cold rubber), which has become the mainstream method, the number of trans linkages increases.
Solution polymerized SBR is also known as a raw material for low fuel consumption tires.
During solution polymerization, a random copolymer and a block copolymer, in this case a thermoplastic elastomer react. SEBS with improved weather resistance with a hydrogenated double bond between the block copolymers thermoplastic elastomer is also widely used.
SBR has excellent heat and abrasion resistance, mechanical strength, and stable product quality. It is also inexpensive and easy to process.
On the other hand, its tear strength and cold, organic solvents and ozone resistance are somewhat inferior to other products.
Although it is mainly used in car tires, SBR is also used in large quantities in industrial products such as belts and hoses.

Tensile Strength

Tensile strength is the mechanical strength as determined with force needed prior to breaking when a rubber material is stretched. Test methods conform to JIS K 6251 and a test piece is stretched by a load at a fixed speed. The force required for it to break is divided by the cross-sectional area, which yields the breaking stress. Test methods are with a dumbbell-shaped test piece or a ring-shaped test piece; our firm uses a test with a dumbbell-shaped test piece. The tensile strength is indicated by the following equation:

TB: (MPa)
FB: Maximum tensile force (N)
A Cross-sectional area of a test piece (mm²)

Thermal resistance

There are various types of thermal resistance, such as heat transfer resistance, thermal resistance due to convection, thermal resistance due to radiation, and contact thermal resistance, though heat transfer resistance is often used for evaluation of a heat conductor and heat conductive tests. This is simply called thermal resistance.

Thermal resistance is the coefficient that indicates the difficulty of heat flowing as part of the movement of heat that occurs when an object is subjected to heat. Units are indicated in K/W or ℃/W. When a heat conductor as in Thermal resistance is the coefficient that indicates the difficulty of heat flowing as part of the movement of heat that occurs when an object is subjected to heat. Units are indicated in K/W or ℃/W. When a heat conductor as in Figure B is sandwiched between a heat-generating object such as a CPU and a heat-dissipating object such as a heat sink, supplying electric power (W) to a heat-generating object, i.e., an amount of heat, means that a temperature difference will be produced at both ends of the heat conductor (the heat-generating object and heat-dissipating object) . The value where this temperature difference is divided by the electric power will be the thermal resistance.Figure B is sandwiched between a heat-generating object such as a CPU and a heat-dissipating object such as a heat sink, supplying electric power (W) to a heat-generating object, i.e., an amount of heat, means that a temperature difference will be produced at both ends of the heat conductor (the heat-generating object and heat-dissipating object) . The value where this temperature difference is divided by the electric power will be the thermal resistance.

In other words, the relationship will be

thermal resistance (℃/W) =temperature difference (℃) ÷ sign amount of heat for a heat source (W)

A smaller temperature difference at both ends of a heat conductor means that heat is more readily transferred, so the level of heat-conducting action is quite high. In other words, a substance with a small thermal resistance is preferred as a heat conductor.

Thermal resistance is not a specific value (physical property) for a substance, so values will differ even with the same material depending on the environment and conditions of usage. In other words, saying thermal resistance means a value indicating heat-conducting characteristics incorporating various conditions such as the state in which a heat-conducting material is placed, the thermal conductivity of the material, material thickness, and the material dimensions.

Vibration Decoupling

When the frequency ratio is √2 (about 1.4) or more, the vibration transmission rate becomes 1 or less. This is a state of vibration isolation, where vibration transmitted from the outside is reflected by the vibration damping material, resulting in a low vibration transmission rate.

Vibration Damping

Vibration damping is the process of converting vibration energy into heat, which in turn reduces vibration. When the vibration of a piece equipment reaches the natural frequency, the vibration amplifies (resonance). This frequency is called the resonance frequency (resonance frequency ≈ natural frequency). Without vibration damping, the vibration transmission rate will increase infinitely.
The more effective the vibration damping, the lower the vibration transmission rate (resonance magnification) at the resonance point will be. However, vibration insulation will decrease at higher frequencies.

Volume Resistance

Volume resistance is the name of the electrical resistance value per unit volume. In other words, it is the resistance value between 2 facing surfaces of a 1m³ cube as indicated in Figure C. Units are indicated in Ohm ・ m. In addition, Ohm ・ cm is also used, though this will indicate the resistance value for a 1cm³ cube and not a 1m³ one, so 1 Ohm ・ m =100 Ohm ・ cm.

The resistance value for material as a whole is determined by multiplying the length by the volume resistance and dividing by the cross-sectional area. The volume resistance is a specific value (physical property) for a substance, so when comparing with the same dimensions, a substance with a large volume resistance will also have a large resistance value. In other words, a substance with a large volume resistance is preferred as an insulating material.

Insulators, semiconductors, and conductors can be classified based on the size of resistance. In terms of materials with larger numerical values,

insulators > semiconductors > conductors

Volume resistance is not a specific value for a substance and varies according to temperature. The volume resistance of metal, which is a conductor, increases with a rise in temperature, though it conversely tends to decrease for a semiconductor or insulator with an increase in temperature.

What makes a good heat dissipation sheet?

1. A good heat dissipation sheet has high thermal conductivity.
2. A soft surface that can adapt to an uneven surface on the heat source and/or heat sink surface to eliminate all air gaps between the two components.
3. As thin as possible and does not interfere with the conduction of heat.

Young's modulus

Young's modulus is an index to indicate hardness. This value indicates how much force can be exerted per unit area when a certain substance is compressed and its thickness is 0 (this is not actually possible). It is also called the compressive elasticity modulus; if this value is large, the substance can be said to be hard

In general, Young's modulus indicates elasticity in a static state (a state where force that changes with time is not exerted) ; the dynamic value is called the complex compressive elasticity modulus (refer to Complex shear rate).

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