Which is more suitable for making phone cases, TPU or silicone? Which is better for keyboard covers, TPU or silicone? Whether you are a purchaser or an engineer, if you want to know whether your product is more suitable for TPU or silicone, I hope you can find the answer in this article. I will introduce you to the differences between the two materials from all aspects. I hope it will be helpful to you.
TPU(Thermoplastic Polyurethane)
TPU, the full name of which is thermoplastic polyurethane, is a thermoplastic elastomer. It is produced by the polymerization of diisocyanate and polyol. This thermoplastic elastomer combines the flexibility of rubber with the ease of processing of thermoplastics.
- Mechanical strength: Good. It is not easy to break when stretched or bent.
- Elasticity: Close to rubber. You can make phone cases with TPU, which can resist drops and provide cushioning. Medical catheters also mostly use TPU, which can withstand bending and is not easy to break.
- Durability: It is reflected in wear resistance. To reduce the consumption of cables, a TPU protective coating is often applied to the outside of the cables, which can extend their service life. If you want to make shoe soles, TPU wear-resistant is also a good choice.
- Chemical resistance: It is not prone to swelling or corrosion when in contact with oils, greases, or common solvents.
- Transparency: The adjustable formula can be modified to make semi-transparent or fully transparent watch straps and decorative parts.
Silicone
Silicone is a commonly used polymer material. The raw materials are mostly granular and can be processed into basic forms such as silicone sheets and silicone rods.
- Heat resistance: The outstanding feature of silicone lies in its heat resistance, which enables it to maintain structural stability within a wide temperature range
- Flexibility: Flexibility is silicone’s another advantage. Silicone has moderate resilience and is suitable for making kitchenware that needs to be bent repeatedly. It can also meet the pleasant touch requirements of baby products
- Chemically inert: Silica gel is not prone to reacting with other substances
- Waterproof performance: Silicone has a dense surface that is not easy to penetrate, and is often used as a sealant or gasket base material in waterproof parts of outdoor equipment or industrial equipment.
Silicone vs TPU: Physical Properties Comparison
Hardness
The hardness range of TPU is wider, from Shore A60 to D85. Due to its high hardness, TPU can meet the demands of many heavy-duty scenarios. Silicone‘s conventional hardness is between A20 and A80. However, high-hardness silicone requires special formula adjustment, and the process is complex. The common type on the market is still soft silicone. It can be said that the overall hardness of silicone is lower than that of TPU.
There is no distinction between good and bad in terms of hardness, which just determines the different application scenarios they are suitable for.
The TPU has high hardness, and you can make industrial pulleys, tool handles, and other components that need to bear weight.
Silicone soft can be used in products such as baby pacifiers and sealing rings.
If your product needs to balance hardness and elasticity, then the range of TPU options is wider.
Impact Resistance Performance
The elasticity of silicone comes from the flexibility of its molecular chains. When subjected to external forces, it can absorb energy through deformation and return to its original state after being impacted. If you use silicone to make products that require cushioning, such as sports protective gear or children’s toys, they may not break easily when dropped. There may be marks on the surface, but it will not affect the functionality.
The impact resistance of TPU focuses more on toughness. Its molecular chain contains hard segments and soft segments. The hard segments provide support, while the soft segments absorb energy and can disperse stress when impacted, making TPU less likely to crack. TPU is more suitable for some industrial impact-resistant scenarios, such as electronic mechanical casings and electronic wheels.
In conclusion, if you want to make a batch of household products with low frequency and low impact, silicone is sufficient, and the appearance of silicone is more aesthetically pleasing. If your product type needs to withstand high frequency and high impact in the industry, then TPU is more durable.
Tear Resistance Performance
The tear strength of silicone is mainly due to the three-dimensional network structure of the rubber. Its tear resistance is not very high, and it is prone to tearing under high pressure. The molecular crystalline part of TPU is high, and its mechanical strength is better than that of silica gel.
In addition, in the process of production of TPU, we will also add some reinforcing agent, which makes TPU’s tear strength higher than that of silicone.
Wear Resistance
The wear resistance of TPU is better. If your product needs to handle high-friction scenarios, such as the soles of sports shoes and industrial pulleys, then TPU can meet your requirements.
The wear resistance of silicone is moderate. Excessive friction may cause scratches on its surface.
Silicone vs TPU: Chemical Resistance Comparison
- Silica gel has resistance to acids, alkalis, and common solvents and is not easily corroded by these substances. Silicone tableware can be seen everywhere in the kitchen, such as silicone baking molds, silicone spatulas, and high borosilicate glass lunch boxes. You don’t need to worry at all that silicone tableware will be corroded and decomposed by daily food. It is very safe for the human body. Silicone is also widely used in sealing gaskets or infusion tube accessories in medical equipment, which can ensure that no harmful substances are released when in contact with liquid medicine or disinfectant reagents. Silicone also has waterproof properties and can be used in bathrooms or outdoors without losing its effectiveness due to water vapor penetration.
- The chemical resistance of TPU is more prominent in its resistance to oil and grease. TPU has strong resistance to substances such as lubricating oil, hydraulic oil, and mineral oil. You can use TPU to make oil seals for car engines. TPU can also be waterproof. However, TPU has a slightly weaker tolerance to strong acids and alkalis. Contact with concentrated sulfuric acid or strong alkaline solutions may slowly erode the surface.
Silicone vs TPU: Temperature Resistance Comparison
- The silicone’s heat resistance is better. Silicone is a thermosetting elastomer. The final curing process in the production process forms a three-dimensional cross-linked structure for the silicone rubber. Once this structure is formed, it cannot be melted any longer. This also endows silicone rubber with excellent heat resistance. Within the temperature range of -60℃ to 250℃, you don’t need to worry that the performance of the silicone will change. The specially treated silicone baking molds can even withstand a high temperature of 350℃. Silicone gaskets used in industry are not prone to shrinkage or cracking even when exposed to hot air for a long time. Silicone can still maintain its elasticity in an environment as low as several dozen degrees below zero. For the sealing rings in the refrigerator or products used outdoors in the north, you can also consider using silicone.
- The temperature resistance range of TPU is slightly narrow. TPU can maintain its own performance stability within the temperature range of -40℃ to 120℃. With moderate low-temperature resistance and the outstanding oil-resistant property of TPU, you can consider using TPU for automotive seals, which can operate well even in winter. If it is for making household products that can stand low temperatures, TPU is sufficient. However, in high-temperature environments, TPU is prone to softening. If the temperature exceeds 100 degrees for a long time, it may experience a decline in mechanical properties. If you are considering making products that rely on heat sources in industry, silicone is a better choice than TPU.
What are the Processing Methods for TPU and Silicone?
TPU Processing Methods
Injection Molding
Heat and melt the TPU, then inject it into the mold. After cooling and setting, open the mold to obtain the product. Injection molding is suitable for mass production, and injection molds are sufficient for slightly complex products.
Extrusion Molding
After heating and melting the TPU raw materials, they can be injected into the screw extruder for production. Extrusion molding is generally used for naturally continuous pipes or plates. The TPU conveyor belts and sealing strips used in industry are obtained through extrusion molding processing.
Calendering Forming
Calendering is suitable for the production of films or thin sheets, such as waterproof rolls.
3D Printing
3d printing can produce more complex TPU parts, such as industrial fixtures. The advantages of 3D printing lie in its high speed, low cost, and no need for mold opening.
- There is another advantage in the processing performance of TPU.TPU is a thermoplastic elastomer. After being made into products, it can be reheated and softened, and then re-granulated for processing. If you need to make small-batch customized products and adjust a certain part, you just need to heat and reshape it. This will greatly reduce the loss of waste materials and save costs.
- Due to the moderate temperature resistance range of TPU, the processing of TPU has very high requirements for temperature control. The melting temperature can be set at 180-220℃. If the temperature is too low, the surface may be rough. However, if the temperature is too high, TPU is prone to decomposition and failure.
Silicone Processing Methods
Molding
Molding involves mixing silicone rubber particles and curing agents in a certain proportion, filling them into a preheated mold, heating, and pressurizing to trigger a cross-linking reaction. This method is suitable for manufacturing complex-structured products such as baby pacifiers or silicone adapters.
Extrusion Forming
Extrusion molding is mainly aimed at long strip-shaped products such as sealing strips, silicone tubes, or silicone gaskets. The silicone mixture is heated and melted through an extruder, then extruded into a mold with a specific cross-section. After cooling and solidifying, it is cut into sections. The extrusion process is highly efficient and suitable for mass production, but it has high requirements for die precision. Even a slight deviation in the mold can lead to uneven thickness of the finished product.
Injection Molding
The third is injection molding. It is used for small precision parts such as silicone buttons and keyboard pads. The silicone material is injected into the micro-mold, heated and vulcanized, then the mold is opened and the parts are taken out. Injection molding can achieve rapid and large-scale production. Production requires strict control of vulcanization time. If the time is insufficient, the vulcanization will not be thorough, and the colloid will not take shape. If the vulcanization time is too long, the colloid will turn yellow and burn again.
- It should be noted that once silicone products have been cured and set, they cannot be reheated and reshaped. If your budget is sufficient, the cost is controllable. If your budget is limited, you can start with a small-scale trial production to reduce the generation of silicone waste.
Are silicone and TPU Suitable for Outdoor Products？
- Silicone has better weather resistance. Silicone will not turn yellow significantly under long-term exposure to ultraviolet rays. Even after being exposed to wind and sun for several years, the sealing rings for outdoor lamps or the rubber strips for car sunroofs can still maintain their elasticity and sealing performance.
- TPU is greatly affected by ultraviolet rays. When TPU is exposed to outdoor ultraviolet rays for a long time, its molecular chains will undergo photo-oxidation reactions, and its surface will gradually turn yellow and even develop fine cracks. This is because the aromatic structure of TPU is prone to absorbing ultraviolet energy, leading to the breaking of chemical bonds. However, aliphatic TPU can improve its resistance to yellowing through modification, but its UV resistance is still weaker than that of silicone.
Silicone vs TPU: Application Area
Electronic Appliances And Cables
TPU has high elasticity and can be made into phone cases or computer cases, which can act as a buffer when dropped. In the field of cables, TPU is also often used to make the outer protective layer of a charging cable.
Silicone is mainly used for insulation and sealing in electronic and electrical appliances. Silicone has excellent waterproof performance. You can use silicone to make sealing silicone gaskets for electronic sensors. This insulating gasket can prevent short circuits in internal components.
The Medical And Health Field
Silicone has obvious advantages in the medical field due to its excellent biocompatibility. Silicone can be used to make infusion tubes, blood bags, and breathing masks in medical devices. Silicone braces for dental use are also widely applied in dentistry. Silicone is not easy to yellow. This kind of brace keeps its appearance, and at the same time, can take into account the softness and comfort.
TPU is mostly used in non-contact structural components in the medical field. For instance, the wheel guard plates of medical trolleys and the shells of infusion pumps.
Industrial Pipelines And Seals
TPU is suitable for high-pressure oil-resistant pipelines. The TPU oil transfer pipe can withstand the impact of high-pressure oil without expanding or deforming. It can also resist corrosion after long-term immersion in mineral oil. The air guide pipe can also be made of TPU. TPU has high mechanical strength and can withstand impact without cracking.
Silicone rubber seals mainly focus on extreme environments. For instance, high-temperature gaskets for car engines, corrosion-resistant sealing rings for chemical equipment, and steam pipe seals for food processing lines can all be made of silicone
Daily Consumer Goods
TPU can be used to make the soles of sports shoes, shoulder straps of backpacks, connecting parts of toys, phone cases, handles of sports water bottles, etc.
Silicone can be used to make children’s teething rings, silicone wristbands, baking molds, mobile phone cases, household sealing rings, etc.
Are TPU And Silicone Safe?
Silica gel has A stable molecular structure and does not contain harmful substances such as bisphenol A and phthalates. It is biocompatible and non-toxic. Both the EU LFGB and the US FDA have certified its food-grade safety. This is also the core reason why silicone can be widely applied in the food and medical fields.
TPU itself has no definite toxicity, but its safety depends more on the formula and processing technology. If plasticizers, flame retardants, and other additives are added during the processing, TPU will become toxic. Silicone is a more reliable choice for products that come into direct contact with the human body or food.
Can Both TPU And Silicone Be Recycled? Are They Environmentally Friendly?
Both TPU and silicone are environmentally friendly.
- The environmental friendliness of TPU is mainly reflected in its recyclability. The recycling process is also relatively simple. It can be directly crushed into granules by a crusher and then remade into TPU recycled material through a granulator. There are also many downstream markets for this recycled material. Shoe soles and the outer sheaths of cables can all be made of this recycled material. This reduces the amount of TPU waste incinerated.
- The environmental friendliness of silicone is reflected in its own safety. Silicone is a thermosetting elastomer and is difficult to recycle. However, silicone itself is non-toxic, and discarding or burning it will not have any impact on the environment.
Summary
Silicone and TPU each have their own advantages, which determine their roles in different fields. We hope that after reading this article, you will have some understanding of which material to choose for your product. If you still have any other questions, you can contact us for free. Legensilico is a silicone product manufacturer with rich experience in production. I sincerely hope to provide you with more customized services.
FAQ
What Types of TPU are There?
- Polyester-based TPU: Good mechanical properties. It is used in the automotive and aerospace fields.
- Polyether-based TPU: Its outstanding advantage lies in its resistance to hydrolysis, making it suitable for the production of products in damp outdoor environments.
What are The Types of Silica Gel?
- Methyl silicone: Methyl silicone is the most fundamental type of silica gel. The overall performance is relatively balanced.
- Vinyl silicon: Vinyl silicon is obtained by introducing vinyl into methyl silicon. The introduction of vinyl increases the crosslinking density of silicone rubber, enhancing the tensile strength and compressive strength of silicon. Vinyl silicone is suitable for scenarios requiring high-strength sealing.
- Fluorosilicone: It has outstanding chemical resistance and can be used to make corrosion-resistant products. This type of silicone can resist the corrosion of acids, alkalis, salts, and oils, but it is very expensive.
- Phenyl silicon: It can withstand high temperatures and be applied in high-temperature environments.
TPU Case vs Silicone
TPU protective cases and silicone protective cases each have their advantages. If you need high drop resistance, choose a TPU protective case. If it is for children or medical use, choose a silicone protective case. If you want to balance aesthetics and shock resistance, then choose silicone. Of course, silicone protective cases are a bit more expensive. If your budget is limited, choose TPU.
TPU vs Silicone Keyboard Cover
If your product is positioned in high-end office, educational, or medical scenarios. And your target customers have requirements for touch softness, color design, and a higher budget, you can choose a TPU keyboard cover.
If your product is targeted at gamers, industrial users, or outdoor scenarios. And your target customers place more emphasis on practicality, such as oil resistance, stain resistance, and wear resistance, or if your budget is not high, you can choose TPU to make keyboard covers.
