Material selection of soft rubber products

—— silicone, TPE, TPU, PVC, rubber

In daily life, there are all kinds of soft glue products, mobile phone protection cover, gloves, waterproof ring, toothbrush handle, various wheels and so on. These products are all soft rubber products, but the materials used are different. What is the difference between them, and how should product design and development choose reasonable materials for soft rubber products (parts)?

Reasonable selection of materials needs to be considered from the use of the product environment combined with the performance of the material, the main properties of soft rubber products are: hardness, elasticity, corrosion resistance, weather resistance, friction coefficient, easy to crack, coloring performance, high (low) temperature performance, cost, processing technology, etc.

If used with daily supplies, baby supplies and other factors also need to pay attention to whether the material is harmful to the human body, whether there is a bad smell, feel comfortable and other factors. In special cases, the conductivity (such as silicone buttons that can be made when adding conductive carbon black), thermal conductivity, radiation resistance, light transmittance, etc.

Silicone

Silicone is a kind of thermosetting elastomer, has the advantages of safe and non-toxic, insoluble in water and any solvent, non-toxic, stable chemical properties, in addition to strong alkali, hydrofluoric acid does not react with any material, high adsorption performance, good thermal stability, stable chemical properties, the earliest widely used in adult products, food products.

The processing process of silicone products is more complex, which needs to go through a series of functions such as refining, molding and vulcanization to make products. Silicone products belong to thermosetting rubber, vulcanization after reheating will not melt, can not be directly recycled again processing. Silicone products are usually more expensive than the TPE.

Donguan Xinhongfa custom made various of silicone parts

In terms of hardness, the general hardness of silicone is between 0A and 70A, while the hardness of TPE is generally between 0A-100A, and the softest can reach 000 degrees or 00000 degrees, so TPE is soft, and the shape of silicone is stronger.

Silicone has advantages over TPE in high temperature resistance. Silicone temperature resistance is generally between 200 degrees~300 degrees, and TPE theoretically TPE general TPE high temperature resistance between 130-150 degrees Celsius, and then high aging cracking. The price of silicone is generally more than the general TPE price. TPE is more advantageous in the price, in addition to special TPE materials, such as halogen-free flame retardant, food grade and other characteristics.

TPE

TPE, Thermoplastic Elastomer, is a thermoplastic elastomer material. Thermoplasticity means that it can be recycled and processed by injection. TPE products have excellent colorability, environmental protection and non-toxic. It can be secondary injection molding, with PP, PE, PC, PS, ABS and other matrix materials coated with adhesion, and can also be formed separately.

TPE injection molding handle

The heat resistance of TPE is not as good as that of rubber, with the rise of temperature and the physical decline is large, so the scope of application is limited. At the same time, compression deformation, elastic recovery, durability and equivalent rubber compared with poor, the price is often higher than that of similar rubber.

Wide range of hardness, excellent transparency, gloss, and comfortable feel, widely used in adult products. With good ultraviolet light resistance, weather resistance, high temperature resistance, long-term use for outdoor.

TPU 

TPU (Thermoplastic polyurethanes) name is thermoplastic polyurethane elastomer rubber, its hardness range is usually in S Shaw hardness 60A~70D (currently foreign hardness in about 45A soft TPU, but the price is quite expensive), and TPE hardness range can be changed in Shaw hardness A Scale 0~100 range. Therefore, it can be said that the hardness interval of TPE is medium and low hardness, while the TPU hardness is medium and high hardness.

The elastic and elastic recovery properties of TPU (resistance to flexion and creep resistance) are better than those of TPE. The material structure of TPU is mainly a homogeneous polymer structure, which belongs to the polymer resin class. However, TPE is an alloy material of heterogeneous structure composed with multiple components. TPE processing with high hardness is prone to product deformation, and in all hardness range, TPU shows excellent elasticity, and the product is not easy to deform.

TPU spring wire material

Some coated products, such as handles, wheels, may be TPE or TPU. TPU products have rough feel and strong friction resistance; TPE products have a delicate and soft feel with weak friction performance.

PVC flexible glue

PVC For polyvinyl chloride, was the world’s largest production of universal plastic, is very widely used. It should be noted that on October 27,2017, the World Health Organization published the list of carcinogens by the International Agency of Research on Cancer for preliminary reference, polyvinyl chloride is in the list of class 3 carcinogens.

PVC itself is a hard material, after the addition of plasticizer, can make the plastic products with soft, easy to bend, folding, elastic soft glue. The hardness of soft rubber products is usually expressed as Shaw hardness A internationally, for PVC is often expressed according to the percentage of the added plasticizer and PVC raw material P% (P). For example: 50kg of PVC material, 40kg of plasticizer is 80P (40 / 50=80%).

PVC Soft glue accessories

From the outside, PVC products are rough compared to silicone products, while the surface is smooth and has color.

Judging by the hand feel, the silicone product is soft, flexible and elastic, pvc soft glue is relatively hard, and the hardness of both can be adjusted, but PVC has no toughness.

 PVC Common materials and environmental protection materials are also called ATBC-PVC, and silicone can be passed through the ROHS certification, is environmentally friendly.

Silicone products are generally made more transparent, the burning smell is relatively small, the product into a powder, and PVC products after the fire product will be black, the smell is bad when burning.

Silicone products in PVC products are more resistant to heat and cold. Silicone products can be heated in the microwave oven, but PVC can not.

Rubber

There are many kinds of rubber, such as natural rubber, butadiene rubber, propylene rubber, of course, silicone rubber; and silicone is one of the specific varieties of rubber, is short for silicone rubber.

Silicone and rubber two materials, we use the same environment, silicone and rubber materials can be used, but with the change of the physical environment and requirements, the performance of the two materials will appear a significant gap, but it takes time to present.

For example, the most commonly used condensing tube in the laboratory, which has rubber and silicone, but the silicone property is better, and the aging resistance effect is significant. In structure, the rubber main chain is mainly carbon, which comes from organic matter, while the silicone main chain is mainly based on Si-O bond, which is the main difference between them.

Silicone is rich in color, can be made into a variety of different colors, rubber products are mostly black, occasionally can also see other colors. For example, bicycle tires occasionally have other colors, while car tires are all black. The reason is that the rubber mixing with carbon black raw materials, the process of high temperature condensation of carbon elements and hydrocarbons, can make the rubber become very strong, wear resistance and aging resistance is greatly improved.

Rubber products

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