1.TPE raw material concept
TPE raw materials, refers to the thermoplastic styrene-butadiene rubber SEBS, SBS as the base material, add other necessary inorganic, organic and polymer components blended, after mixing equipment, screw extrusion, cutting granular cooling granular raw materials with rubber elastic properties, TPE raw materials actually belong to the polymer composite materials, its initial shape for the granular. PlasticRubber, meaning thermoplastic rubber.
2. TPE raw materials basic characteristics
Gloss: TPE of SBS base material has the appearance of high gloss particles, while TPE of SEBS base material (TPE) is sub-surface particles.
Transparency and color: the appearance of transparent or opaque particles. The opaque solid color particles have a white base color, and the color varies slightly for different blending systems.
Particle shape: Initially, the TPE particles made by the production plant are cut granular (cylindrical strip), currently, for the consideration of product appearance quality, manufacturers optimize the production of cutting equipment, the particles made mainly round particles, which looks more high-grade products.
TPE raw material is a soft polymer material with rubber characteristics, hardness is an important physical property parameter. And by adjusting the component content ratio of the blending system with SEBS, SBS as the base material, the hardness (and physical properties) of TPE raw materials can be changed, so that the material can be widely used in different industries.
2.2.1 TPE raw materials hardness range.
The most common hardness range is 0 ~ 95A (Shore), hardness higher than 95A, generally expressed in D. Shore D TPE raw materials, its hardness range is about 40 ~ 60D. On the conversion of Shore hardness A and D, there are three approximate conversion relationships as follows.
(1), D = A - 50;.
(2), D=A/2; (3), A=0.173D+86.58.
The second algorithm is considered relatively simple and is more commonly used in practical cases. If the user requires more accurate hardness, it is recommended to use the corresponding hardness tester to measure the actual hardness of the sample.
In addition, SEBS-based TPEs (TPEs) can provide super-soft TPEs with hardnesses below 0A, usually expressed in C or OO. This kind of super soft TPE (TPE) has wide application in some erotic goods, solid dolls, medical teaching models, shock absorbing seat cushion products.
2.2.2 TPE raw material hardness measurement
As above, different hardness range of TPE material, should use the corresponding Shore hardness tester (ShoreA, D, C) to measure. But in fact, in most cases, the hardness of TPE raw materials, mainly Shore A hardness tester to measure. Shore hardness A table to test the hardness of TPE raw materials samples, the thickness of the sample plate is generally in the 6.5mm or so, Shore hardness tester A needle into the sample plate limit depth of 2.5mm. sample plate thin, the measured material hardness may be hard, sample plate thick, the measured material hardness is soft.
At the beginning of the hardness measurement, the TPE material can withstand high pressure, but over time, it will yield due to creep and relaxation. When reading the value of the hardness tester, it can be read instantly or after a specific delay time, usually after 5 to 10 seconds. In addition, when reading hardness data, the values are generally higher when using prompt readings than delayed readings.
2.3 Other basic physical parameters
In addition to hardness, the more important physical properties parameters regarding TPE raw materials are
Specific gravity, the approximate range of 0.84 ~ 1.3 g / cm3; tensile strength: the approximate range of 3 ~ 10MPa; elongation at break: 200 ~ 1500%; shrinkage: 1.5 ~ 3%; melt index: 1 ~ 20g / 10min (2.16kg, 190 ℃)
2.4 TPE raw materials physical functional properties
Friends familiar with TPE raw materials are relatively well known, TPE raw materials have a wide range of applications market. This is due to its wide range of adjustable hardness, but also attributed to TPE raw materials have a lot of functional characteristics, is shared as follows.
2.4.1 Soft touch and wrapability
TPE raw material is soft to the touch, and at the same time has a good covering, covering refers to the TPE raw material can be compounded with most hard plastics injection molding as a whole, giving the product a soft touch. Toothbrushes, sports equipment, beauty equipment, power tools, luggage accessories, various casters, electronic products, smart wear, etc., all use TPE overmolding. In addition, such as cable wire, erotic products, etc., are excellent to show the soft touch of TPE.
2.4.2 Shock-absorbing and anti-slip characteristics
TPE has rubber elasticity, with shock absorption and anti-slip function. Many foot mats, seat mats, anti-slip mats, shoe soles, etc., all use TPE as raw materials.
2.4.3 Sealing and elasticity
TPE raw materials have excellent resilience. Can be used as a seal, such as seals, seals, etc., its high elasticity can also be used for fitness equipment, medical equipment, such as medical tourniquets, traction machine tension belt, yoga fitness belt.
2.5 TPE raw material other characteristics
Temperature resistance: high temperature 70~90℃, low temperature -50℃.
Chemical resistance: solvent resistance in general, with strong resistance to hydrolysis and alcohol solvent; not resistant to acids and alkalis and organic solvents, as well as engine oil lubricants.
Weather resistance: SEBS-based modified TPE (TPE) has good weather resistance and aging resistance, UV resistance can reach 3.5 to 4 levels.
2.6 TPE raw materials environmental characteristics
TPE raw materials are excellent grade polymer materials, in line with environmental standards, does not contain PAHS, NP, BPA, phthalates and salts.
3.TPE raw materials selection skills
3.1 The most effective way is to provide OK samples to the supplier. Suppliers according to the sample, analysis of its performance requirements, to provide the corresponding TPE raw material grades to the user to try to confirm.
3.2 Some (foreign) users, may not be convenient or no OK samples. This time the user should provide material physical requirements, as well as what products to do, there is no special application requirements. Only after understanding the user's requirements in detail, the supplier can provide suitable samples to the user.
3.3 If the customer does not have a sample, and the requirements are not clear. Then we can't provide sample material to customers for trial run.
4. TPE raw material molding matters
4.1 Single material injection molding
Adopt common injection molding machine. Barrel section 130~140℃; metering section 150~170℃; plasticizing section 180~200℃; injection section, 180~190℃. Adjust the injection temperature, injection speed and pressure according to the physical properties of TPE raw material, equipment, mold and product structure.
According to the variety of hard material and material application requirements, choose the appropriate cover material grade. Two-color injection molding machine can be used for rapid molding as well as ordinary injection molding machine with two sets of molds and two injection molding. Overmolding temperature 160~250℃. Overmolded PP 170~190℃; Overmolded ABS,180~200℃; Overmolded PC,200~220℃; Overmolded nylon 220~250℃.
Overmolded PC,PP,ABS are easy, overmolded nylon PA, if it is with overmold, it is recommended to preheat the nylon parts first, and then immediately preheat the parts for TPE material overmolding. For larger area and longer flow channel of overmolding structure, try to open more glue inlet points in a reasonable die position.
4.3 Extrusion molding
TPE raw material extrusion molding, extrusion temperature is slightly lower than injection molding, generally 170 ~ 190 ℃; SBS base material TPE extrusion temperature than the SEBS base material TPE (TPE) extrusion temperature to be slightly lower than 10 ~ 20 ℃. In addition, extrusion molding, should try to choose a lower melt finger, melt strength higher TPE material grades.