Analysis of several adhesive characteristics of TPE/TPR materials

　　Thermoplastic Elastomer (Thermoplastic Elastomer) is an environmentally friendly low-carbon composite material with the characteristics of rubber (high elasticity, compression permanent deformation, etc.) and the processing characteristics of plastic (simple process). (Popularly spoken: thermoplastic elastomer is a rubber with high elasticity, high resilience, but also has the characteristics of injection molding processing, with environmental protection, non-toxic safety, a wide range of hardness, excellent coloring, soft to the touch, weather resistance, fatigue resistance and temperature resistance, superior processing performance, no vulcanization, can be recycled to reduce costs, both secondary injection molding, and PP, PE, PC, PS, ABS (ABS and other substrate materials wrapped bonding, but also can be formed alone. 　　1.TPE material self-adhesive; refers to the TPE material surface has a strong adhesive, similar to the surface coated with glue. This has a strong self-adhesive TPE material can be used to paste everyday items to prevent touching fall or overturn. Similar TPE material, a foreign TPE manufacturer has a special research and development, and applied for a patent. In fact, in the conventional TPE blending system, adding a good compatibility with the main blending system of viscosity enhances the adhesion of the TPE material surface. This kind of adhesion is positive, which is what the user demands and hopes for. 　　2. Adhesion on the surface of soft TPE materials. Some low hardness TPE materials, due to the oil component content in the mix, resulting in a sticky feeling on the surface of soft TPE materials. This sticky feeling is caused by the oil in the formulation. Usually TPE (TPR) based on SBS base is more prone to surface sticky hand problem, this kind of stickiness is negative and is what users want to eliminate. 　　3. Stickiness during overmolding. Adhesion here, refers to the TPE and the wrapped substrate (plastic) due to the close solubility sp or good compatibility, injection molding at high temperatures, the bonding of the two materials in the bonding surface of the fusion bonding effect. The good or bad adhesion mainly depends on the surface affinity of TPE and the covered plastic (similar melting point, close polarity and surface tension, etc.)

2021-10-22

TPE/TPR material surface whitening, scratching phenomenon analysis

　　Why does the surface of TPE/TPR material appear white, easy to scratch white phenomenon? 　　Phenomenon one, TPE/TPR materials are not scratch-resistant, easy to scratch white 　　Analysis of the reasons: TPE / TPR production formula filled with white powder material on the side of more, rubber material components to reduce. As the white filler is only physically mixed with the rubber phase, there is no chemical reaction, so it is easy to scrape the white material by hand. For some black and colored products, products scraped white, the phenomenon of non-scraping will affect the appearance of the product. 　　Solution: Use TPE, TPR grades containing relatively little white filler. 　　Phenomenon two, TPE / TPR material surface whitening, a layer of white material, can be wiped away by hand. 　　Analysis of the reasons: TPE / TPR material added additives ①, after a period of time in the TPR products, will gradually migrate to the surface of the product, the formation of a layer of white material. 　　Solution: Reduce the amount of additives added in the TPR formula ②. 　　Remark. 　　①, this kind of additives such as internal lubricant, whitening agent, etc. 　　②, it is recommended to control the addition amount below 3‰. 　　P.S. At present, there is a new enhanced TPE, TPR scratch-resistant formula program, which is to use coupling agent modified heavy calcium instead of ordinary heavy calcium, improve the compatibility of the filler and the substrate, thereby enhancing the white scratch resistance of TPE materials.

2021-10-22

Santoprene TPV for solar applications

　　Santoprene TPV is a material that combines the easy processing properties of thermoplastic with the durability of thermoset rubber, and has been commercially available for thirty years. It is used in a wide variety of industries, including automotive, construction, home appliances, sanitary ware, and power tools. With the booming of the solar industry, its excellent performance has been successfully applied in this industry as well. 　　Typical successful applications in solar energy are: photovoltaic connectors and solar street light seals. 　　As we all know: the photovoltaic industry for the connector material requirements are very demanding: 1: weather resistance - the requirements of the resistance to weathering. 　　1: weather resistance - require good ozone resistance or even reach f1 outdoor use grade 　　2: flame retardant - required to achieve V-1 grade or higher 5VA grade 　　3: Temperature resistance - -40 ℃ to 80 ℃ cycle test 　　4: Environmental protection - in line with ROHS and REACH regulations; recyclable 　　5: Flexibility - requires good resilience and excellent sealing performance 　　6: low temperature - in minus 40 ℃ to maintain good flexural and impact resistance 　　7: Voltage resistance - can withstand certain voltage breakdown, excellent insulation performance 　　For this particular application of PV, ExxonMobil recommends two material-specific specifications: black: 151-70W256 and natural: 251-80W232, which have been used successfully.

2021-10-22

5 practical points of TPE/TPR injection molding process

　I. If the surface of the product is strict, it must be dried before injection. Generally, the hopper drying is 70~80℃/2h or pallet drying is 80~100℃/1h. For pallet drying, it should be noted that the thickness of material layer is generally not more than 50mm. It is recommended to use tray drying. If there is blistering on the surface of the injection molded strip, or cut open the strip and find that there is a hole inside, or find that the surface of the product and scattered silver wire, it can be determined that the TPE/TPR raw materials contain too much moisture. 　　Second. Try to use low-temperature injection molding. Under the premise of ensuring the quality of plasticization, try to reduce the extrusion temperature, and the use of increased injection pressure and screw speed to reduce the viscosity of the melt, to improve the purpose of fluidity. When the surface of the strip injected from the nozzle is smooth and shiny, the plasticization quality is good. If the strip injected from the nozzle is very bright, it can be determined that the barrel temperature can be reduced. If you try to use low temperature injection, you can reduce the cooling time and improve the production efficiency of customers. 　　III. Upper parabolic temperature setting. The temperature is highest in the middle zone of the screw, slightly lower in the charging section and slightly lower in the nozzle. Typical temperature settings are 150~170℃ (feeding), 170~180℃ (middle), 190~200℃ (front), 180℃ (nozzle). This temperature setting is only for reference, the specific temperature can be adjusted according to the specific physical properties of different TPE and TPR materials. If you find that the content of the product bulges (gas is wrapped inside) and the gate is easy to break when demoulding, you can refer to trick two to make adjustments. 　　IV. Keep the pressure as small as possible. Generally speaking, the holding pressure should be lower than the injection pressure, and the holding time can be determined by weighing the product, and the weight of the product should not increase, or the shrinkage mark accepted by the customer should be used. If it is found that the gate is easy to break during demoulding and the trick 2 does not work, then it should be feasible to reduce the holding pressure. 　　V. In case of several stages of injection, the speed should be from slow to fast. Because of this, the gas inside the mold can be discharged easily. If there is gas inside the product (bulging inside) or there is a dent, this method can be used to adjust the product if trick 2 does not work.

2021-10-22

【Injection molding knowledge】TPE material common shrinkage water marks and other phenomena processing methods

　TPE product shrinkage refers to the phenomenon that the surface raw materials at the wall thickness are pulled in due to volume shrinkage during the cooling and hardening process of the product, which results in the appearance of depression marks on the product surface. 　　TPE shrinkage phenomenon usually has the following reasons. 　　1 injection molding process problems (such as low injection pressure, insufficient holding time, high mold temperature, insufficient cooling time, etc.) 　　2 structural design problems (uneven thickness of the glue bit, improper ratio of rib width to glue bit thickness, too thick glue bit thickness of the product, etc.) 　　3 mold processing problems (feed opening too small or runner cross-section too small, etc.) 　　4. Material aspect (shrinkage difference). 　　TPE shrinkage solutions: 　　1, increase the injection pressure, holding pressure, and extend the injection time. For tpe plastic with high fluidity, high pressure will produce flying edge and cause collapse pit, it should be adapted to reduce the material temperature, lower the barrel front section and nozzle temperature, so that the change of melt volume into the cavity is reduced and easy to cold solidify; for high viscosity plastic, the barrel temperature should be increased to make the mold filling easy. When shrinkage occurs in the gate area, the holding time should be extended. 　　2, Increase the injection speed to make the part filled and eliminate most of the shrinkage. 　　3, Thin-walled parts should increase the mold temperature to ensure smooth material flow; thick-walled parts should reduce the mold to speed up the curing of the skin to set. 　　4, appropriately increase the cooling time to reduce thermal shrinkage. Extend the cooling residence time of the parts in the mold, maintain a uniform production cycle, increase the back pressure, the front section of the screw to retain a certain buffer pad, etc. are conducive to reducing shrinkage phenomenon. 　　5, low precision products should be released from the mold early to let it cool slowly in the air or hot water, which can make the shrinkage depression smooth and does not affect the use. 　　6, the temperature is too high or too low, will not be able to achieve the effect of pressure-holding. 　　7, the amount of rubber injection is not enough, increase the amount of injection glue.  

2021-10-22

【Case Share】TPE high-grade cell phone protective case overmolding

　　Cell phone cases are an important branch of injection molding production. There are 2 major series of cell phone cases, hard rubber and soft rubber. Hard rubber materials generally have PC, PC/ABS, etc. Soft rubber materials generally have TPE (TPR, TPU, etc.), hard rubber materials are injection molding, soft rubber materials are also injection molding. 　　Soft rubber has many advantages, mainly resistance to stretching, not deformed, soft, good toughness, non-slip, impact resistance, good fall resistance. Disadvantages are easy to stick to dust, poor heat dissipation, hair "sticky", easy to lose color, the product is thicker. Soft plastic cell phone cover injection molding production later generally have to post-processing, such as screen printing, color printing, transfer printing, drip processing and other more complex. But the injection molding itself does not seem to be complicated but it is quite difficult. The defects that are easy to appear in the production of soft plastic cell phone cover injection molding: sticky mold, shrinkage, batch front, bubble, long cycle time. The solution of the above problems depends on good mold design, material selection, parameters and machine selection. 　　The case is a high-grade soft plastic cell phone case injection molding production. One of the high grade is reflected in the thickness, the thickness of common soft rubber is more than 1mm, but this product is only 0.55mm, the second is the material, high-grade TPE material. The size of the product is about 125*60*8mm, the single weight of the product is about 8g, and the total weight of the product with water outlet is about 30g. 　　First is the material, the customer has specified TPE. second mold design. This product is characterized by thin, too weak strength, easy to stick film, in order to increase the effect of release, double-sided with a local fine skin pattern design. Four sides of the power hole opening key and other structures with side core. In order to improve the production efficiency and consider the stability of the production, the mold cavity one out of one. Considering the beauty of the product, the mold parting line is designed at the bottom edge. Considering the low temperature of the mold, which is also a common practice for soft plastic injection molds, a three-plate design is used. 　　The runner is manufactured with direct fire pattern. The gate design is critical. There are generally 2 kinds of entry points for this type of mold in the industry. 　　1) It is the edge of the bottom edge. 2) At the part of the camera hole. Considering the beauty of our high-grade products, we adopt the camera hole water entry design, and at the same time, considering the exhaust, the camera hole water outlet part of the wall is empty. At the same time this split water outlet in the subsequent processing of punching and cutting to remove. 　　The third is the machine selection. Because the product is very thin, just the product body flow length ratio of about 120 / 0.55 = 220, and then take into account the water mouth, flow length ratio of about 250, such a large flow length ratio for the general machine is very long to eat, to use high-speed machine. 　　The fourth is the parameters. Parameter test process is more complex, mainly sticky mold problems, shrinkage and batch front problems. After several tests, the following parameters were determined. Low mold temperature, high material temperature, short injection time, precise switching position, and precise holding pressure. On this basis, the cycle time is gradually shortened.

2021-10-22

【Case Share】TPE elastomer material applied to high-end sealing strip

　　Seal, is a product that seals something so that it cannot be easily opened, and plays the role of shock absorption, waterproof, sound insulation, heat insulation, dustproof, and fixing. Seals are made of rubber, paper, metal, plastic and other materials. Since the 80s, the seals have been applied to various industries such as automobile, doors and windows, cabinets, refrigerators, containers, etc. According to the requirements of different industries, we have developed unique products such as automobile seals, mechanical seals, door and window seals, etc. 　　Recently, the customer needs to make a TV inner casing sealing strip, the requirements, the material dimensional stability, the material does not deformation shrinkage after assembly. Engineering reference customers to provide OK material samples to make samples, preliminary analysis: material is PP plus TPV modified material, physical analysis: hardness: 94-95A, the focus is to open the mold when the shrinkage rate of the material to be true. The product is 1.1 long and is injection molded by more than 800T machine. 　　Through comparison and analysis, the engineering first recommended one of our company: ENB95A2-03, to the customer test molding out of the mold OK, but compared with OK board, the surface is too bright, the size of the length is greater than the design length NG. test material back and engineering communication, analysis of the reasons, the material surface bright, TPV composition is low. The dimensional stability of the material is not enough and the shrinkage rate is not right. Engineering into the improvement program: 1. Add more TPV content, improve the material elegance.  2. Canna rice calcium carbonate to improve the temperature stability of the material 3. Use high temperature resistant PP modified again to provide sample material to the customer test material: ENB95A3-01, the results NG, material size stability, the effect is not good, the reason is: the use of high molecular weight SEBS 533 in the material, polymer material shrinkage is larger, so need to be modified with medium molecular materials, again a sample: ENB95A -SL, after the customer trial material forming OK, 5 days size test is stable state OK, this project mass production success. 　　Summary: Through this project trial material comparison, from the material shrinkage and dimensional stability, ENB95A-SL is better than ENB95A3-01. The dimensional stability of medium molecular SEBS material is better, and the product is not easy to produce stress deformation or shrinkage in the injection process. Such seal products, if the product size requirements are high, all can use this solution.

2021-10-22

[TPE injection molding tips] A few simple steps to solve the problem of TPE products bubbles

　　TPE material will not decompose under the general injection temperature, so its bubble generation only comes from water gas.　Influencing factors are: mold temperature, being pressure, melt speed, injection time all have influence 　　In the process of punching the mold is disturbed by gas, often in the product surface appear silver filigree, or tiny bubbles, or in the thick wall of the product to form bubbles. The source of these gases mainly involves raw materials containing moisture or volatile substances or melting agent in excess, but also may be too high material temperature, tpe plastic subjected to heat for a long time, degradation occurs and the production of degradation gas, the causes of these many, involving factors oh may have injection molding machine and mold and many other aspects. 　　Solution. 　　1, drying. First dry the material, if not, you need to adjust the process. 　　2, adjust the injection speed, it may be that the material flow is very fast, the injection speed is very fast, resulting in the mold internal air is not eliminated in a timely manner, in the joint line position is easy to line into a bubble. 　　3, the injection mold to increase the exhaust bad (a simple solution is to add a small piece of paper in the middle of the mold to see if the bubble is less, such as less then the mold exhaust is a problem. 　　4, adjust the mold temperature, the temperature is too high, the TPE material inside the low molecular composition will escape to form bubbles. 　　5, appropriate to increase the back pressure of the screw, the barrel inside the air out

2021-10-22

TPE injection molded products are insufficiently filled, how to improve the process?

(1) Improper feed adjustment, lack of material or excessive material. Inaccurate feeding measurement or abnormal feeding control system operation, abnormal injection cycle caused by injection molding machine or mold or operating conditions, low pre-plastic back pressure, or low particle density in the barrel may cause material shortage. For large particles, For granular materials with many voids, plastics with large changes in specific volume of crystallinity, and plastics with higher viscosity, the amount of material should be adjusted higher, and the amount of material should be adjusted larger when the material temperature is high. When there is too much material at the end of the barrel, the screw will consume extra injection pressure to compress and push the excess stock in the barrel during injection, which greatly reduces the effective injection pressure of the plastic entering the mold cavity. The product is difficult to fill. 　　 (2) The injection pressure is too low, the injection time is short, and the plunger or screw returns too early. 　　Molten plastic has higher viscosity and poor fluidity at lower working temperature, so it should be injected at higher pressure and speed. For example, in the production of ABS color parts, the high temperature resistance of the colorant limits the heating temperature of the barrel, which has to be compensated by higher injection pressure and longer injection time than usual. 　　 (3) The injection speed is slow. 　　Injection speed is of great significance for some products with complex shapes, large thickness changes, and long processes, as well as plastics with higher viscosity, such as toughened ABS. When the product cannot be filled with high pressure, high-speed injection should be considered to overcome the problem of dissatisfaction. 　　 (4) The material temperature is too low. The temperature of the front end of the barrel is low, and the viscosity of the molten material entering the cavity rises to the point where it is difficult to flow prematurely due to the cooling effect of the mold, which hinders the filling of the far end; the rear section of the barrel is a plastic with low temperature and high viscosity Difficult flow hinders the forward movement of the screw. As a result, it seems that the pressure indicated by the pressure gauge is sufficient, but the melt actually enters the cavity at low pressure and low speed; If the nozzle temperature is low, it may be that the nozzle is in contact with the cold mold for a long time during the fixed feeding and loses heat, or the nozzle heating ring is insufficiently heated or has poor contact, resulting in low material temperature, which may block the mold's feeding channel; if the mold does not have cold material Well, with self-locking nozzles and post-feeding procedures, the nozzles can maintain the necessary temperature; the nozzle is too cold when it is just turned on, and sometimes a flame gun can be used for external heating to accelerate the temperature of the nozzle.

2021-09-10