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silicone overmolding

Overmolding refers to a process used to combine at least two materials to create one object part or design.

Today, two technologies can be used to create overmolded objects: Injection molding and 3D printing

Injection molding is the most common process used for over-molding more recently. Some 3d printing technologies are being used to over mold objects of the two, Overmolded parts typically consist of a substrate and the overmolding material, or sometimes more materials. one material is commonly known as the substrate, it is either partially or fully covered by a second material or materials referred to as the overmolded material.

The substrate material can be just about anything, metal, plastic, glass, and so on. The overmolded material is often silicone rubber or thermoplastic material. The over molding process often results in either a chemically bonded part of the materials are mechanically interlocked.

Overmolding offers several benefits. one, in particular, is that it can eliminate secondary operations when building parts thereby reducing manufacturing costs. It is often used to deliver a specific feel to a product such as softening edges or delivering a more pleasant feel or giving users a firm but soft grip. In brief, the injection overmolding process works like this.

With injection molding technology, substrate parts are molded first, the molded parts are either placed into a different mold or placed back into the injection molding machine, where the second material or materials is injected once cooled this object is removed from the mold, then you have an over molded part.

The 3d printing technology is typically jetting where two or more materials are jetted concurrently onto the part during the layer-by-layer build process. The types of products that are over molded include tool hand grips like drills scissors, Screwdrivers, personal care products, cell phones, and anything needing market differentiation. For more information about the silicone overmolding process, please visit Ukong website.

 

Silicone products

The silicone has many excellent characteristics and functions. But silicone belongs to the production of synthetic raw materials, the different proportion of ingredients in the materials will have a different functional effect, and what reasons for the aging in silicone rubber products? Following are some reasons for aging in silicone cases.

Contact medium aging

Exposure to moisture in the air, or other conditions, such as the external insulation of electrical power systems, in salt-contaminated areas, is extremely susceptible to salt spray, therefore, it is necessary to study the aging performance under this condition. In addition, some silicone rubber products which come into contact with oil are tested to improve their oil resistance.

The aging of silicone rubber under different kinds of oil is due to the mechanical damage of aging on one hand, and on the other is the degradation of cross-linking system, which results in low molecular weight materials. The presence of fluid can reduce the coefficient of friction, but it can also accelerate the chemical degradation of the silicone rubber, thus accelerating wear.

 

Thermal oxidative aging

Natural rubber (NR) for capacitor seals, EPM, EPDM, Styrene-butadiene, butyl rubber, silicone rubber (NVQ), and so on, are all of these forms of thermal-oxidative aging during use. NR containing a lot of unsaturated double bonds, under the combined action of heat and oxygen, the VULCANIZATE will degrade, the molecular chain and cross-linking bond will be cracked and broken, resulting in aging.

Thermal oxidative aging is both a radical and an oxidation reaction. Under anaerobic thermal aging conditions, free radical decomposition occurs, and the lower the bond cleavage energy, the faster the decomposition, when molecules break down and form free radicals, then the main chain breaks and forms cross-links, producing all kinds of gases. In ultraviolet aging, molecules absorb ultraviolet light and activate certain functional groups, and decomposition or through the energy transfer in other functional groups, such as decomposition, through the formation of active groups and reaction.

The oxidative decomposition of side-chain organic groups in silicone rubber occurs mainly in the anaerobic high-temperature open environment, which leads to the hardening of silicone rubber, while in an oxygen-free high temperature closed environment, the main chain fracture reaction occurs mainly, the formation of volatile cyclic polysiloxane, resulting in softening of silica gel products. The oxidation of side-chain methyl and the degradation and fracture of the main chain are the main reactions of silicone rubber at high temperatures.

Fatigue Aging

The fatigue aging of silicone rubber case is that the aging phenomenon of silicone rubber products under the action of a certain frequency and periodic stress, which is caused by the change of the molecular structure of silicone rubber material, that is, force and heat effect. (due to the rubber in a number of deformation, hysteresis phenomenon, so that the internal silicone causing heat )

 

Ozone aging

Ozone content in the atmosphere is very low, in the aging process of silica gel, ozone attack silica gel molecules, silica gel expansion and dispersion resulting in surface cracks. Ozone reacts with double bonds in silica molecules to form Ozonide and peroxide, which in turn regenerates ozonide. The Ozonide is broken down into free radicals by the action of heat and light, leading to a chain growth reaction. In addition, the silicone rubber under stress will produce molecular fracture, but not the formation of Ozonide, the phenomenon of cracking and aging.

By studying the effect of ozone on different kinds of tread rubber, including natural rubber, oil-filled methyl-styrene-butadiene rubber, and the blend of isoprene rubber and cis-1,4-polybutadiene rubber, etc., the service life of silicone rubber decreased and decreased rapidly in the short time of ozone action, which proved that silicone rubber had obvious degradation at the beginning of ozone action. Along with the Ozone Action Time extension, the service life drops slowly. This may be due to the degradation process slowing down during the deepening phase of polymer decomposition.

 

For customized products, some choose screen printing, pad printing, or transfer printing which including heat transfer printing and water transfer printing. At present, transfer printing is widely used in plastic, hardware, rubber, silicone rubber, PVC, ceramics, solid wood, and other industries, so for soft silicone rubber products. Heat transfer printing and water transfer printing are similar, but what is the difference between heat transfer print and water transfer print?

Silicone bong

Heat transfer printing

The heat transfer printing process is one-time heating of heat transfer printing film, transfer the decorative pattern onto the surface of the product to form a high-quality decorative mask. In the process of heat transfer, heat and pressure are applied to separate the maintenance layer and pattern layer from the polyester substrate, hot-melt adhesive bonds the decorative layer and product surface.

Water transfer printing

Water transfer printing with a special chemical treatment of the film, after printing the required color lines, flat on the surface of the water, the use of water pressure, the color line pattern evenly transfer to the surface of the product, when the coated film is automatically dissolved in water, after cleaning and drying, and then a layer of transparent maintenance coating, this product has shown a completely different visual effect!

The main difference is:

The heat transfer printing process is complex. step 1, needs a professional operator to Create a high-resolution image. Step 2, According to the picture size made dot-type gravure engraving plate. Step 3, The gravure plate is installed on the printing machine and printed on the PET polyester film, which is printed into thermal transfer printing film. Thousands of meters of finished patterns can be printed in one hour. Step 4, The heat transfer printing film installed on the heat transfer printing hot stamping machine for printing, simple operation, the one-time formation of the pattern, without color register. A heat transfer printing hot stamping machine 8 working hours a day can print out thousands of products.

Water transfer printing greatest technical advantage is no needed for special equipment, not limited by the medium, do not need special supplies, no high-temperature heating is required as long as you have a scanner, computer, inkjet printer plus water transfer ink, water transfer paper, you can print any solid object, any surface at will, the image bright color, absolute photo-quality. Small investment, quick to use, easy to operate, applicable to all areas. But the defect is that its processing efficiency is low, high cost, its effect is not good as the heat transfer printing!

For the above two processes, if you still do not know how to choose, Ukong suggests you choose the heat transfer printing when you do a large number of silica gel products transfer printing. While water transfer printing process for a small number of silicone products. The heat transfer printing process is complex but printing has bright colors, ever-changing, small color differences, good reproducibility. Water transfer printing operation is the simple but slightly lower printing quality.

 

silicone vibrator

Generally, the surface of silicone products is typically quite sticky. Sometimes this can present problems in an end user’s application, especially when buying glossy silicone products, such as silicone tubes, custom silicone molds, silicone sheets, etc. However, there are several ways to reduce this problem.

 

Powder with Talcum

The simplest way is through the addition of talcum powder, wiping this uniformly across the product’s surface. Silicone swim caps with talcum are very effective, it is easier to wear and take off the silicone cap after powder, and talc can be washed off.

 

Spray hand-feeling electrostatic oil on the surface

It is a common method to spray hand-feeling electrostatic oil on the surface. In general, the silicone products we have used for a long time will be sprayed with hand-feeling electrostatic oil, such as silicone phone cases, silicone protective covers, silicone vibrator and silicone facial cleansers, etc., this process will not affect the use efficacy, and will not cause harm to the body skin, so this process in the silicone products industry is more widely used.

This process is mainly to spray a layer of hand-feeling oil on the surface of the product to enhance the surface feel of the product and the isolation layer. Because it has a certain adhesion, there will be no demoulding after baking at high temperature, so it is adopted by many consumers, however, the main problem with this kind of process is that it is a little difficult to go through some strict environmental monitoring and certification. Because the ink materials do not meet the environmental requirements.

 

Produce with anti-static silicone rubber material

anti static silicone rubber

In addition to spray handle oil, silicone rubber manufacturers can also use materials to solve the problem of dust, that is, the selection of anti-static silicone rubber processing, because dust-proof and anti-static silicone rubber is a two-component silicone material, it can be cured at room temperature or at elevated temperature. It is not limited by the shape and thickness of the silicone products which can endure high temperature for a long time. It can be deeply cured, to achieve the effect of non-stick dust.

Anti-static silicone rubber has excellent resistance function, usually after high-temperature vulcanization of the static silicone rubber product surface resistance of 106-109Ω, but also through customer demand modulation to higher performance. Compare with the gas-phase silicone, they are no different. so it is suitable for molding and extrusion and liquid injection molding process and so on, usually, this kind of silicone can be used for silicone suction cup, silicone medical hose, and food-grade silicone products, etc.

 

Made by Matte Surface mold

silicone mold

custom silicone mold

Silicone products made by the matte surface mold are not active dust absorption. Matte surface silicone is relatively rough to touch, its advantage is effectively isolated from the dust absorption.

 

How to do if the silicone products accidentally get a lot of dust?

  1. The slight dust can be wiped with a dust-free cloth, and the dust on the surface of the product can be removed.
  2. The more serious dirt and dust can be wiped with white electric oil, or directly soaked in white electric oil liquid and wiped with a clean dust-free cloth.
fluorosilicone vs silicone

For sealing and protection products, Fluorosilicone is suitable for use in aerospace, automobile, electromechanical, electronic, mechanical, and architectural fields, it can be used in kerosene at-55 °C ~ 220 °C and in steam and open flame at 150 °C, and in the strength of more than 100 kg under the pressure of heat resistance, oil resistance, ozone, and other harsh environment continued to use.

Fluorosilicone is called trifluoro propyl methyl polysiloxane, also known as special silicone rubber, its main material is carbon tetrafluoride and ethylene which combine trimethyl trifluoro propylcyclo trisiloxane, and an amount of tetramethyl tetravinyl ring, tetra-siloxane, and a small amount of blocking agent was cured and mixed under the catalyst. Compared with ordinary silicone rubber, the impact properties are improved effectively.

Compared with ordinary silicone products, the outstanding feature of Fluorosilicone is performance and service life. The normal service life of ordinary silica gel products, such as reaching the bearing capacity of Fluorosilicone rubber, will accelerate the aging capacity, the tensile strength will drop, the deformation will be larger, and so on. Silicone elastomers are also known as silicone rubbers which are composed of silicon, carbon, hydrogen, and oxygen. They are non-reactive, stable, and resistant to extreme environments and temperatures from −55–300°C (−67–572°F). Fluorosilicone also has these characteristics.

Fluorosilicone rubber distinguishes itself from silicone because it also contains additional beneficial properties common to fluorocarbons. The addition of these compounds enhances FVMQ’s capacity to resist solvents, fuel, and oil. Fluorosilicone has a slightly lower maximum service temperature hot air resistance than ordinary silicone.

The important features of Fluorosilicone products are as follows:

  1. Resistance to oil, solvents, and chemicals

Compared with methyl vinyl silicone rubber, Fluorosilicone has excellent oil resistance, solvent resistance, and chemical resistance, and good oil resistance and solvent resistance even compared with fluoro rubber. It can be said that Fluorosilicone rubber is the only elastomer that is resistant to non-polar medium at-68 °C ~ 232 °C. The resistance of Fluorosilicone to gasoline containing methanol is also good. Even in the gasoline/methanol mixed material, the hardness, tensile strength, and volume of the vulcanizate have little change, the physical properties have hardly changed after 500h long time immersion testing.

  1. Heat resistance

The high-temperature decomposition of Fluorosilicone is the same as that of ordinary silicone, i. e. side-chain oxidation, main chain fracture, side-chain thermal decomposition, and various compound reactions. As the decomposition products can also cause the main chain fracture, so the heat resistance, usually worse than ordinary silicone rubber, at 200 °C temperature has begun oxidation aging. However, by adding a small number of heat stabilizers such as iron, titanium, and rare earth oxides, it can be improved remarkably and has enough heat resistance even at 250 °C. The influence of temperature on Fluorosilicone is greater than that of silicone but less than that of fluoro rubber. The service life of Fluorosilicone rubber was also studied at 150 °C × 2000H, 175 °C × 5000H and 200 °C × 4000H, the results were second only to that of methyl vinyl silicone rubber.

  1. Cold tolerance

Fluorosilicone and ordinary silicone products are good low-temperature performance. Because Fluorosilicone rubber is a linear polymer with soft SI-O as the main chain, its low-temperature property is better than that Fluororubber with C-C as the main chain. Among them, Fluorosilicone (LS-2370U) has better low-temperature characteristics, the brittleness temperature reaches -89 °C, and the general Fluororubber is -30 °C.

  1. Electrical properties, radiation resistance

The electrical properties of Fluorosilicone are similar to those of ordinary silicone rubber, but its special value is that it changes little under harsh conditions such as high temperature, low temperature, humidity, oil, solvent, chemicals, ozone, and so on. The radiation resistance of Fluorosilicone is not outstanding, but the radiation aging resistance is better than methyl vinyl silicone rubber.

  1. Physical and mechanical properties

Fluorosilicone rubber and ordinary silicone rubber, vulcanizate mechanical strength (especially tear strength) is relatively low. Therefore, improving the strength of Fluorosilicone rubber is also an important research topic.

  1. Other features

Fluorosilicone rubber weather aging resistance is very good, even after exposure for 5 years, still maintain good performance. Ozone is one of the most common gases produced during the aging of elastomers, but no cracks or cracks are found in Fluorosilicone rubber by dynamic or static tests. In addition, Fluorosilicone rubber mold resistance, physiological inertia, an anticoagulant is also very good.

Ukong uses compression molding, silicone injection molding process to manufacturer all kinds of silicone products including Fluorosilicone rings, ordinary silicone products.

PVC sheet

PVC sheet, PVC panel, PVC wall panel, PVC cable, PVC roll, PVC square tubing, PVC angle trim, etc. Silicone molding resin, silicone shoe cover, custom silicone molds, etc. Silicone and PVC materials are widely used in building materials, industrial products, daily necessities, pipes, wires and cables, packaging films, foaming materials, sealing materials, fibers, etc. From the appearance, it is hard to tell PVC or silicone products, but they are different materials and have different characteristics.

Silicone

Silicone belongs to rubber material. Silicone is mainly composed of organic silicon and silicon atoms, and the main material is siloxane, which is insoluble. The silicone rubber products are mainly made of silicone oil, siloxane, silicone resin, and silane coupling agent. Silicone is the safest material in the rubber industry now, it is a kind of environment-friendly chemical material.

Compared to PVC thermoplastic materials, Silicone is outstanding in environmental adaptability. It can be used at high and low temperatures and under a variety of environments for a long time, but still keep good performance. The outstanding performance is as follows:

Temperature Resistance

Silicone has good temperature resistance, the conventional temperature range of -40 ~ 230 degrees within the long-term use.

Environmental suitability

Silicone is not easy to be ultraviolet and ozone environment oxidation can be used in the natural environment.

Physical inactive

The compound siloxane is one of the most inactive compounds known. They are resistant to biological aging, no rejection reaction with the animal body, and have good anticoagulant properties, which can be used in a variety of environments.

Tensile strength

Silicone products have good surface tension, in which the main silane chain in the silicon molecule is more soft and flexible, so the tensile rebound strength is strong, long-term tensile rebound, no deformation.

Insulation

Silicone products have good electrical insulation properties, dielectric loss, resistance to voltage, resistance to arc, resistance to Corona, volume resistance coefficient, and surface resistance coefficient. Silicone is a good insulating material, therefore, it is one of the more stable electrical materials.

PVC

PVC is polyvinyl chloride. PVC belongs to plastic material. PVC compounds are the polymerization of vinyl chloride monomer, an azo compound, and other chemical aids at high temperatures. PVC materials can be made by polymer synthesis into different kinds of products, such as PVC sheet, PVC panel, PVC wall panel, PVC cable, PVC roll, PVC square tubing, PVC angle trim, etc. PVC material is a mainly white powdery amorphous material, density is 1.3-1.5, material vitrification temperature is within 90 degrees, the highest temperature resistance is 170 degrees. So in high temperature, PVC will be automatically decomposed into hydrogen chloride, beyond the temperature range will automatically catalyze decomposition.

There are two methods to identify PVC products

(1) identification by combustion method

Softening or melting temperature range 75 ~ 90 °C

Burning Flame(yellow upper, on the lower, is green), and has smoke. Self-extinguishing without fire. Has a pungent acid smell. This is the simplest and quick method.

(2) solvent treatment identification

Solvents: oxolane, cyclohexanone, methyl ketone, Dimethylformamide;

Non-solvent: methanol, acetone, heptane.

Put the suspected PVC products into the above solvent, observe the dissolution of the products to determine whether it is PVC. When the solvent is heated, the dissolving effect will be more obvious.

For consumers, it is difficult to identify PVC products or silicone products. But here are some tips for your reference,

  1. Touch

Silicone products have a soft and smooth feeling.

PVC touch is slightly hard and rough.

  1. Color

The newly produced silica gel products are basically indistinguishable from the PVC products in color, but after long-term use, the PVC materials will appear sticky color and color yellowing, especially in the light and heat environment. Most silicone products rarely appear in such a situation.

  1. Shore hardness

The shore hardness of silicone rubber can reach 30-90 degrees, while the conventional hardness of PVC is between 50-95. The hardness of silicone rubber material can be lower and softer, while the softness of PVC can not. Even though silicone in high shore hardness, it still has a good spring back strength, while PVC is relatively poor spring back strength.

  1. Temperature

The processing temperature of silicone rubber is about 180 °C in the production process, and the normal temperature resistance is about-40 to 230 °C. PVC softening or melting temperature range is 75 ~ 90 degrees. In excess of temperature, both materials will have a certain amount of chemical reaction. Silica gel appears to be a white burning phenomenon. PVC will appear to soften, self-extinguishing without fire, and has a pungent acid smell.

  1. Rebound strength

Rebound strength is the most important difference between these two materials. Silicone material has a good silicon molecular connecting strength, the rebound strength will be much better. While the PVC material has poor rebound.

 

Fluorosilicone

Fluorosilicone is a good elastomer. The main chain is Si-O bond in its structure. After adding polar fluorine atoms (such as trifluoropropyl) into the side chain, the structure of fluorosilicone rubber is called CH2CH2CF3. Because of the strong electron-absorbing effect of fluorine atoms, the bond length of the C-F bond is shorter, it can form a good shielding effect to C-C bond, improve oil resistance and solvent-resistance of rubber, and make it a good elastomer with good resistance to non-polar medium at -68°C ~ 232°C. Therefore, fluorosilicone rubber is widely used in the field of the high-end locomotive and military aerospace seals.

As the price is expensive, and the electronic effect of fluorosilicone rubber, has strong adsorption to the surrounding dust, thus affecting the performance, so the production process of fluorosilicone rubber is very strict. Here is some suggestion of the production process.

Transportation and preservation. In the process of preservation and transportation, fluorosilicone rubber must be wrapped with insulating paper and plastic bags to prevent dust and impurities from contact with the rubber and adsorption.

Cutting fluorosilicone rubber. In the process of taking materials, cutting. First of all, using alcohol to scrub the surface of the knife or the tool scissors, after cleaning, can start the cutting. In the cutting process, try to avoid hand, skin, and rubber contact, but can not wear gloves, so as to avoid the pollution of glove fiber or skin oil on the fluorosilicone rubber.

Weighing fluorosilicone rubber. Before weighing, the tray needs to be cleaned with alcohol.

Fluorine silicone rubber mixing. Before mixing, must use alcohol scrub the mixer roller and baffle, to ensure no impurities contamination. When mixing, should pay attention to the roller temperature, when the roller temperature is 18 °C ~ 28 °C mixing process performance is better. If you need to add silica to adjust the hardness, you must first use hydroxyl fluorine silicone oil to pretreat the silica.

Vulcanization of fluorosilicone rubber. The mold used to produce fluoroelastomer products must be treated by surface treatment, chrome plating treatment, if necessary, use the external release agent.

Second vulcanization of fluorosilicone rubber. There is a lot of low molecular weight volatiles after the first vulcanization. Long-term use will affect the properties of the products, so the general products must be vulcanised in two stages. the second stage vulcanization is carried out in the electric heating blower, and the temperature is kept constant after the required temperature is reached by the way of step-by-step heating. For normal fluorosilicone rubber products, the temperature is 200℃ with 4 to 6 hours.

Re-mixing of fluorosilicone rubber. Long-term parking of fluorosilicone rubber easy structuralization, affect the performance, so for the use of long-term parking of rubber materials need to be re-mixing, placed in the mixer roll 25 times, mixing time of about 8 minutes, to ensure that materials mixed evenly.

Fluorosilicone rubber production environment.  Because it has the characteristic of static electricity absorption ash, so the production environment needs to be purified and dust-free workshop, the production tool is the special equipment. Workers are required to wear clean clothes and hats for entry and exit operations.

rubber molding

Silicone is a thermosetting elastomer, with the advantages of safety and non-toxic. TPE meaning a Thermoplastic Elastomer material. It can be recycled and processed by injection molding. TPU is called Thermoplastic polyurethane elastomer. PVC is polyvinyl chloride, is the world’s largest production of common material, applications widely. Rubber there are many types of rubber, such as natural rubber, cis-1, butadiene-styrene rubber, propylene rubber, and of course silicone rubber.

Mobile phone cover, gloves, waterproof rings, toothbrush handles, various wheels, and sexy doll, etc. are made from soft material, but these materials used are different. What is the difference? how to choose the correct material? First of all, we need to consider the performance of the materials and what they used for. The main properties of soft material are hardness, elasticity, corrosion resistance, weather resistance, coefficient of friction, cracking, coloring, high (low) temperature resistance, cost, processing technology, etc. If used in daily necessities, baby products, etc. we need to pay attention to whether harmful to the human body, whether there is a bad smell, feel comfortable and other factors. Special circumstances also need to consider conductive performance (such as silica gel added conductive carbon can be made of silicone keypads), thermal conductivity, radiation resistance, light transmission performance.

TPE

TPE is Thermoplastic Elastomer, which is a Thermoplastic Elastomer material. Thermoplastic means it can be recycled and processed by injection molding. TPE products have excellent coloring, environmental protection, and non-toxic. Can be secondary injection molding, and PP, PE, PC, PS, ABS, and other matrix material coating adhesion, can also be molded alone.

TPE secondary injection molding handle
TPE secondary injection molding handle

The heat resistance of TPE is not as good as that of rubber. With the increase of temperature, the physical properties of TPE decrease greatly, so its application is limited. At the same time, compression deformation, elastic recovery, durability is relatively poor than rubber. The price is also higher than rubber.

TPE material has a wide range of hardness, excellent transparency, gloss, and comfortable feel, widely used in adult products. With good UV resistance, weather resistance, high temperature resistance, long-term use in outdoor.

TPU

TPU (Thermoplastic polyurethanes) is called Thermoplastic polyurethane elastomer, the hardness range of TPE is from 60A to 70D of s shore hardness (now has soft TPU with a hardness of 45A around, but its price is very expensive), while the hardness range of TPE can be chosen from shore hardness scale 0 to 100 of shore hardness. Therefore, the TPE hardness ranges are medium-low hardness, while TPU hardness is medium-high hardness.

TPU is superior to TPE in elasticity and elastic recovery (flexure creep resistance). TPU main material is a polymer homogeneous structure, which belongs to the polymer resin. While TPE is a multi-component blend of multi-phase structure aggregation of alloy materials. TPE with high hardness is easy to deform, and TPU shows good elasticity in all hardness ranges, and the products are not easy to deform.

TPU spring wire
TPU spring wire

Some coated molded products, such as handles, wheels, maybe TPE or TPU. TPU material products, feel more roughly, friction resistance, while TPE material products feel more smooth and soft, friction is weak.

PVC 

PVC is polyvinyl chloride, was the world’s largest production of common material, applications are wide. It should be noted that, on October 27, 2017, The Who’s International Agency for Research on Cancer published a preliminary list of carcinogens, polyvinyl chloride, in the list of 3 carcinogens.

PVC itself is a hard material, but with the addition of a plasticizer, can make the products soft, easy to bend, fold, with elasticity. Such as PVC sheet, PVC panel, etc.

PVC keychain
PVC keychain

From the outside, the PVC product is coarser than the silica gel product, and the surface of the silicone product is smooth and colored. Judging by the hand feeling, the silica gel product quality is soft, toughness and elasticity are good, PVC soft glue is relatively hard. The soft and hardness of PVC and Silicone can be adjusted, but PVC no toughness.

There are common PVC materials and environmental PVC materials also known as ATBC-PVC. While silicone can pass the ROHS test, is environmentally friendly. Silicone products are generally made more transparent, burning smell slightly. After burning, PVC products will be black, smelly. Silicone products are more heat-resistant and cold-resistant, silicone products can be heated in the microwave oven, and PVC not.

Silicone

Silicone is a thermosetting elastomer, with the advantages of safety and non-toxic, insoluble in water and solvent, non-toxic tasteless, chemical property stability, no reaction with any material, high adsorption performance except strong alkali, hydrofluoric acid, good thermal stability, chemical property stability, the first widely used in medical products, food products, baby products, sports products, such as silicone bibs, menstrual cup, silicone caps, baby suction bowl, etc.

silicone baby bowl

The processing of silicone products is complex, which needs a series of processes such as mixing, molding and vulcanized, etc. Silicone products are thermosetting rubber, after vulcanization when reheating silicone products will not melt. But silicone items can not be directly recycled reprocessing. Silicone products are generally more expensive than TPE products.

Silicone general shore hardness is 0A to 80A, and TPE general hardness in 0A-100A, the softest can reach 000 degrees or 0000 degrees, so TPE softer,

Silica gel has advantages over TPE in high-temperature resistance. Silica gel temperature in general between 200 degrees to 300 degrees. While TPE theory generally temperature between 130-150 degrees, and higher temperature, it will be aging cracking.

Silicone prices are higher than TPE prices except for the special TPE materials, such as halogen-free flame retardant, food-grade, and so on.

Rubber

There are many types of rubber, such as natural rubber, cis-1, butadiene-styrene rubber, propylene rubber, and of course silicone rubber; Silicone is one of the specific types of rubber, which is short for silicone rubber.

Silicone and rubber are two materials, we can use both under the same environment, but with the change of physical environment and requirements, the performance of the two materials will have a significant difference, but it takes time to manifest. For example, the most commonly used laboratory condensers, there are rubber and silicone, but silicone properties better, the anti-aging effect is significant. In structure, the main chain of rubber is mainly carbon, it is organic, while the main chain of silicone is mainly a Si-O bond, which is the main difference between them.

The coloring of silica gel is rich, can be made into a variety of different colors, rubber products are mostly black, occasionally can see other colors. For example, bicycle tires occasionally have other colors, and car tires are black. The reason is that the process of mixing rubber with carbon black and high-temperature condensation of carbon and hydrocarbon can make rubber very strong, wear-resistance, and anti-aging greatly improved. Rubber price is cheaper than silicone. Rubber molding is almost the same as the silicone molding process. Rubber is more widely used in industry, such as rubber coupling, rubber stoppers, rubber sleeve, rubber buffer, rubber fender, etc.

custom rubber products
Custom rubber products

Silikon shore hardness

There are two most common Durometer scale, Shore A for flexible elastomers(range in hardness from very soft to medium, and to hard with almost no flexibility at all.) and Shore D for hard elastomers(hard rubbers, hard plastics). Before producing silicone items, It is very important to select the correct shore hardness of liquid silicone for different applications.

Shore A 0-degree application: it can be used for filling mould of super-soft silicone rubber mold, making of imitation prosthesis, such as mask, penis, sex articles, silicone rubber sheet, making of the soft gasket.

Shore A 5-degree application: it can be used for filling mold of super soft silica gel mould, making hand-made soap and candle silica gel mould, making imitation prosthesis products, such as mask, penis, sex articles, and silica gel sheet, making soft gasket products.

Shore A 10-degree application: can be used for soft silica gel mold filling mold production; hand soap, candle silica gel mold production; simulation of the production of prosthetic products, such as silica gel hands, feet, masks, penis, sex products, silica gel sheet, and soft gasket production.

Shore A 15-degree application: can be used for soft silicone mold filling mold production; hand soap, candle silicone mold production; simulation of the production of prosthetic products, such as silicone hand, foot, mask, penis, sex products, silicone skin, and soft gasket production.

Shore A 20-degree application: can be used for food-grade candy chocolate mold or single mold manufacturing; epoxy, polyester resin, polystyrene, vinyl plastic, paraffin wax, and other materials mold; Small cement components, cultural stone, concrete, gypsum, and other products of mold manufacturing; 3d printing mold production, candle manual soap pouring mold production; mechanical properties of waterproof sealing use.

Shore A 25-degree application: can be used for food-grade candy chocolate mold or single mold manufacturing; epoxy, polyester resin, polystyrene, vinyl plastic, paraffin wax, and other materials mold; Small and medium-sized cement components, cultural stone, concrete, gypsum, and other products of mold manufacturing; 3D printing model production, candle manual soap pouring mold production.

Shore A 30-degree application: can be used for metal crafts, alloy car and other precision mold manufacturing; epoxy, polyester resin, polystyrene, vinyl plastic, paraffin, and other materials mold; Large cement components, cultural stone, concrete, gypsum, and other products of mold manufacturing; high-precision hand plate model design, rapid prototyping design; used in vacuum bag multi-mold spraying class production.

Shore A 40-degree application: can be used for metal crafts, alloy car, and other precision mold manufacturing, as well as fixture protection; epoxy, polyester resin, polystyrene, vinyl plastic, paraffin, and other materials mold; Large cement components, cultural stone, concrete, gypsum, and other products of mold manufacturing; high-precision hand plate model design, rapid prototyping design; lost wax casting process of silicone mold production; product measurement reference production.

Shore A 50-60 degree application: can be used for metal crafts, alloy car, and other precision mold manufacturing, as well as fixture protection; epoxy, polyester resin, polystyrene, vinyl plastic, paraffin, and other materials mold; Large cement components, cultural stone, concrete, gypsum, and other products mold manufacturing; high-precision hand plate model design, rapid prototyping design; product measurement reference production.

The hardness described above is only for the most extensive use. For special uses, it is important to know the part or product that you will be molding clearly.

Lfgb Fda silicone

LFGB (Lebensmittel-, Bedarfsgegenstände-und Futtermittelgesetzbuch, or “ “food, tobacco products cosmetics and other commodity management laws”), is the most important basic legal document in German food hygiene management. The specific LFGB standard: German Food, Articles of Daily Use and Feed Code of September 1, 2005 (LFGB), Section 30 & 31 with amendments and Regulation (EC) No 1935/2004 of the European Parliament and of the Council of 27 October 2004.

LFGB test requested, including extractable components, sensorial examination odour and taste test, Lead and Cadmium, Volatile organic matter(VOM) and Polycyclic aromatic hydrocarbons(PAHs) Content.

Test RequestedConclusion
German Food, Articles of Daily Use and Feed Code of September 1,2005(LFGB), Section 30 & 31 with amendments and BfR recommendation -Extractable ComponentsPASS
German Food, Articles of Daily Use and Feed Code of September 1,2005(LFGB), Section 30 & 31 with amendments-Sensorial examination odour and taste testPASS
German Food, Articles of Daily Use and Feed Code of September 1,2005(LFGB), Section 30 & 31 with amendments and BfR recommendation -Lead and CadmiumPASS
German Food, Articles of Daily Use and Feed Code of September 1,2005(LFGB), Section 30 & 31 with amendments and BfR recommendation -Volatile organic matter(VOM)PASS
Polycyclic aromatic hydrocarbons (PAHs) ContentPASS

German Food, Articles of Daily Use and Feed Code of September 1,2005(LFGB), Section 30 & 31 with amendments and BfR recommendation -Extractable Components

Test Method:    With reference to 61. Mitteilung über die Untersuchung von Kunststoffen, Bundesgesundheitsbl 46 (2003) 362.

Simulant UsedTimeTemperatureMax.Permissible LimitResult of 001Comment
Distilled Water4.0hr(s)100℃0.5%(w/w)<0.1%(w/w)PASS
3% Acetic Acid (W/V) Aqueous Solution4.0hr(s)100℃0.5%(w/w)<0.1%(w/w)PASS
10% Ethanol (V/V) Aqueous Solution4.0hr(s)100℃0.5%(w/w)<0.1%(w/w)PASS

Notes: %w/w = percentage of weight by weight

German Food, Articles of Daily Use and Feed Code of September 1, 2005 (LFGB), Section 30 & 31 with amendments-Sensorial examination odour and taste test

Test Method:    With reference to DIN10955:2004, direct contact method.               No.of panelist:6

Test Item(s)Limit001
Test mediaDistilled water
Test Temperature (℃)100
Test time (hr)4
Sensorial examination odour (Point scale)2.51.0
Sensorial examination taste (Point scale)2.51.0
Comments  PASS

Notes: Intensity scale(rounded at 0.5): 0 – no perceptible difference, 1 -just perceptible difference, 2 -slight difference, 3 -marked difference, 4 -strong difference

German Food, Articles of Daily Use and Feed Code of September 1,2005(LFGB), Section 30 & 31 with amendments and BfR recommendation -Lead and Cadmium

Test Method:     Microwave digestion (GZTC CHEM- TOP-004-01), analysis was performed by ICP-OES.

Test Items(s)LimitUnitMDL001
Cadmium (Cd)mg/kg2ND
Comment   PASS
Lead (Pb)mg/kg2ND
Comment   PASS

Notes: 1.mg/kg =milligram per kilogram of sample  2.MDL=Method Detection Limit  3.ND=Not Detected(less than MDL)  4.★=Absent

German Food, Articles of Daily Use and Feed Code of September 1,2005(LFGB), Section 30 & 31 with amendments and BfR recommendation -Volatile organic matter(VOM)

Test Method:    With reference to 61. Mitteilung über die Untersuchung von Kunststoffen, Bundesgesundheitsbl 46 (2003) 362.

Test Items(s)LimitUnitMDL001
Test Temperature200
Test Timehr(s)4.0
Volatile organic matter (VOM)0.5%(w/w)0.1ND
Comment   PASS

Notes: 1. %w/w = percentage of weight by weight  2.MDL=Method Detection Limit 3.ND=Not Detected(less than MDL)

Polycyclic aromatic hydrocarbons (PAHs) Content

Test Method:   With reference to AfPS GS 2014:01 PAK, analysis was performed by GC-MS.

Test Item(s): Sum of 18 PAHs. Sum of 7 PAHs Acenaphthylene, Acenaphthene, Fluorene, Phenanthrene, Pyrene, Anthracene, Fluoranthene. Naphthalene(NAP CAS NO. 91-20-3). Acenaphthylene(ANY, CAS NO.208-96-8). Acenaphthene(ANA, CAS NO.83-32-9). Fluorene(FLU, CAS NO.86-73-7). Phenanthrene(PHE, CAS NO.85-01-8). Anthracene(ANT, CAS NO.120-12-7). Fluoranthene(FLT, CAS NO.206-44-0). Pyrene(PYR, CAS NO.129-00-0). Benzo(a)anthracene(BaA, CAS NO.56-55-3). Chrysene(CHR, CAS NO. 218-01-9). Benzo(b)fluoranthene(BbF, CAS NO.205-99-2). Benzo(j)fluoranthene(BjF, CAS NO.205-82-3). Benzo(k)fluoranthene(BkF, CAS NO.207-08-9). Benzo(a)pyrene(BaP, CAS NO.50-32-8). Benzo(e)pyrene(BeP, CAS NO.192-97-2). Indeno( 1,2,3-c,d)pyrene(IPY, CAS NO.193-39-5). Dibenzo(a,h)anthracene(DBA, CAS NO.53-70-3). Benzo(g,h,i)perylene(BPE, CAS NO.191-24-2)

FDA testing (Food & Drug Administration Standard) is the minimum safety standard for food-contact silicone products in the US & Australia. The specific standards is: United States Federal Code, Part 21, Food and Drugs (21 CFR).

FDA test requested

Test RequestedConclusion
FDA 21 CFR 177.2600-Total extractive residuesPASS

FDA21 CFR 177.2600-Total extractive residues

Test Method:     With reference to US FDA 21 CFR 177.2600.

Simulant UsedTimeTemperatureMax.Permissible LimitResult of 002Comment
Distilled Water7.0hr(s)Reflux temperature20mg/sq.in<0.5mg/sq.inPASS
Succeeding Extraction2.0hr(s)Reflux temperature1mg/sq.in<0.5mg/sq.inPASS
n-Hexane7.0hr(s)Reflux temperature175mg/sq.in9.2mg/sq.inPASS
Succeeding Extraction2.0hr(s)Reflux temperature4mg/sq.in<0.5mg/sq.inPASS

In summary…

LFGB silicone pass more strict testing and is therefore more expensive, while FDA silicone is more widely used, but silicone that has passed LFGB testing is definitely safer.

Different countries have different standards for food-contact silicone products. LFGB is standard mainly for Europe, while FDA (Food and Drug Administration) is standard in America(though different country has their own FDA standard, but US FDA is internationally applied.) 

Our baby suction bowls, Baby self-feeding spoon, Silicone Baby Plate, Silicone teether, and other silicone baby items are produced with LFGB silicone. We also can custom products with FDA approved silicone or silicone with LFGB certification based on customer’s requirement.