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Two problems that are easily overlooked in TPE injection molding

Thermoplastic Rubber (TPR), also known as Thermoplastic Elastomer-TPE, is a material that combines the characteristics of rubber and thermoplastic. Thermoplastic elastomers have a variety of possible structures. The most fundamental one is that at least two mutually dispersed polymer phases are required. Under normal use temperature, one phase is fluid (make the temperature higher than its Tg-glass transition temperature) , The other phase is solid (make the temperature lower than its Tg or equal to Tg), and there is an interaction between the two phases. That is, a polymer material that shows rubber elasticity at room temperature and can be plasticized at high temperature has mechanical properties and use properties similar to rubber, and can be processed and recycled as thermoplastics. It is built up between plastic and rubber. A bridge. Therefore, thermoplastic elastomers can process rubber products as quickly, efficiently and economically as thermoplastics. In terms of processing, it is a kind of plastic; in terms of properties, it is also a kind of rubber. Thermoplastic elastomer has many advantages over thermosetting rubber. 　　一.TPR dyeing / color matching 　　 SBC-based TPE is superior in color to most other TPR materials. Therefore, they only need a small amount of color masterbatch to achieve a certain color effect, and the color produced is purer than other TPR. Generally speaking, the viscosity of the color masterbatch should be lower than that of TPR. This is because the melt index of TPR is higher than that of the color masterbatch, which will facilitate the dispersion process and make the color distribution more uniform. 　　 For SBS-based TPE, polystyrene-based vehicle is recommended. For TPR based on harder SEBS, polypropylene (PP) vehicle is recommended. For TPR based on softer SEBS, low-density polyethylene or ethylene vinyl acetate copolymer can be used. For softer varieties, PP vehicle is not recommended because the hardness of the composite material will be affected. For some overmolding applications, the use of polyethylene (PE) vehicle may adversely affect the adhesion to the substrate. 　　二.TPR drying / drying 　　According to the characteristics of the material and the supply situation, the appearance and process performance of the material should be tested before molding. The supplied pellets often contain varying degrees of moisture, flux and other volatile low-molecular-weight substances, especially the moisture content of TPR, which has a tendency to absorb moisture, always exceeds the allowable limit for processing. Therefore, it must be dried before processing and the water content must be measured. At high temperatures, the moisture content of TPR is required to be below 5%, even 2%-3%, so a vacuum drying oven is commonly used for drying at 75°C-90°C for 2-3 hours. The dried material must be properly sealed and stored to prevent the material from absorbing moisture from the air and losing the drying effect. For this reason, the drying chamber hopper can be used to continuously provide dry hot materials for the injection molding machine, which is useful for simplifying operations, maintaining cleanliness, and improving quality. It is advantageous to increase the injection rate. The filling amount of the drying hopper is generally 2.5 times the hourly consumption of the injection molding machine

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Discussion on the selection of injection molding machine for TPE/TPR product molding

The so-called adjustment of the machine refers to the constant adjustment of various parameters of the beer machine for the specific mold, until the qualified plastic parts are produced. The various parameters of the plastic beer machine can be roughly classified as follows: 　　 1. Preliminary comprehensive parameters: 　　For a set of specific molds, the following three parameters need to be considered before the mold is made: 　　1.1 Die size: 　　 is Moho×Move× (Mothmi~Mothma) of injection molding machine. Its items must be greater than the corresponding items of the mold: Mwid×Mlen×Mthi (width×height×thickness) 　　1.2 Maximum injection volume: 　　 is the maximum plastic weight SHWT(g) that can be injected by the injection molding machine. The total weight per beer of the plastic must be less than (or equal to) 85% SHWT and greater than (or equal to) 15% SHWT. (When the total weight of each beer>85%SHWT will reduce the efficiency of injection molding). 　　1.3 Clamping force: 　　 is the maximum separation force that the mold can withstand after the mold is closed. Its size is approximately proportional to the projected area of the plastic part. The rough calculation formula is as follows: 　　 clamping force (tons) = projection surface of cavity (inch 2) × material pressure coefficient 　　The material pressure coefficient of PS, PE, PP is 1.7; ABS, AS, PMMA is 2; PC, POM, NYLON is 3. For specific molds, the actual clamping force is ≤ rated clamping force of the beer machine × 90%. Excessive clamping force is not beneficial to the beer machine and will cause mold deformation. 　　 2. Temperature parameter (T): The temperature in the production process of 　　 beer is set according to different rubber materials. It can be divided into the following types: 　　2.1 Material temperature: 　　 Beer production requires the water content in the raw materials to be dried to below a certain percentage, which is called the raw material. Because the water content is higher than a certain proportion of the raw materials will cause defects such as air blooming and peeling. 　　2.2 Barrel temperature: 　　The barrel from the hopper to the nozzle can be divided into: conveying section, compression section, metering section, the heating temperature of each section is collectively called barrel temperature Spend. The barrel temperature is from low to high. In addition, the nozzle temperature is usually slightly lower than the temperature at the metering end. 　　2.3 Mold temperature: 　　 refers to the surface temperature of the mold cavity. The set temperature is different according to the shape of each part of the mold cavity. Generally, the mold temperature of the part where the glue is difficult to remove is required to be higher, and the temperature of the front mold is slightly higher than that of the rear mold. 　　 When the temperature of each part is set, the temperature fluctuation is required to be small, so it is often necessary to use auxiliary equipment such as thermostats and chillers to adjust the mold temperature. 　　 3. Position parameters: 　　3.1 Screw position (S): 　　The segmental switching position of the injection speed and pressure of the screw is called the screw position. 　　The specific segments are as follows: S0 S1, S2, S3, SS. Among them, S0, SS are equal to the amount of melt required for one beer, and SS cannot be less than 10mm (usually between 15-20mm); S0, S1, S2, S3, and SS are the screw position segments, according to the flow of melt The position of the mold cavity is specifically set, S0, S1, S2, S3, SS are injection sections. Among them, S3 and SS are the pressure holding section. 　　3.2 SUCK BACK: 　　 When the screw stops rotating after returning the material, the screw has a backward evacuating action, which is called rubber pumping, and the distance of the pumping is the rubber pumping distance. Generally, it is below 5mm. The purpose of evacuation is to prevent the melt glue from flowing in the nozzle; the evacuation should be appropriate, and too much evacuation will cause defects such as air blooms and bubbles in the finished product. 　　3.3 Mold opening position: 　　The distance between the back mold surface and the front mold surface is called the mold opening distance. Its size is so that the plastic parts can be taken out smoothly. 　　It is advisable to extend the cycle time after the conference. 　　3.4 Position of thimble: 　　 is the distance from the mold surface after the ejector pin of the mold is ejected. Push the product away from the back mold surface 　　 It is better to be able to win smoothly. Be careful not to make the thimble to the end, and there must be enough margin to avoid breaking the slingshot of the mold thimble plate. 　　Four, pressure parameters: 　　4.1 Injection pressure (IP): 　　 The driving force given by the screw to the melt is called the injection pressure. According to the various segments of the screw position, different propulsive forces of the screw

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[Experience Sharing] A must-see for injection molding of TPE transparent/high transparent material products

Due to the high light transmittance of TPE transparent materials, strict requirements on the surface quality of the material products must be required, and there should be no defects such as markings, pores, whitening, haze, black spots, discoloration, and poor gloss. The design of raw materials, equipment, molds, and even products must pay great attention to and put forward strict and even special requirements. Next, the author analyzes the key points of TPE transparent material molding from raw material preparation, equipment requirements, injection molding process and product raw material processing. 　　 1. Preparation and drying of TPE raw materials 　　Because any impurity in the TPE material may affect the transparency of the product, it is necessary to pay attention to sealing during storage, transportation, and feeding to ensure that the TPE material is clean. Especially TPE raw materials contain water, which will cause the raw materials to deteriorate after heating, so they must be dried. During injection molding, a dry hopper must be used for feeding. It should also be noted that during the drying process, the input air should preferably be filtered and dehumidified to ensure that the raw materials will not be polluted. 　　 2. Cleaning the barrel, screw and accessories In order to prevent the contamination of TPE raw materials and the presence of old materials or impurities in the recesses of the screw and accessories, especially the existence of materials with poor thermal stability, screw cleaning agents should be used to clean all parts before use and after shutdown to prevent impurities from sticking. . 　　 Three, the problems that should be paid attention to in the injection molding process (including the requirements of the injection molding machine) 　　In order to reduce internal stress and surface quality defects, the following issues should be paid attention to in the injection molding process. 　　 1. Special screw and injection molding machine with separate temperature control nozzle should be used; 　　 2. The injection temperature should be higher if the material does not decompose; 　　3. Injection pressure: generally higher, to overcome the defect of high melt viscosity, but too high pressure will cause internal stress and cause difficult demoulding and deformation; 　　4. Injection speed: In the case of satisfying mold filling, generally it should be low, and it is best to use slow-fast-slow multi-stage injection; 　　5. Holding pressure time and molding cycle: Under the condition of satisfying product filling without dents and bubbles; it should be as short as possible to minimize the residence time of the molten material in the barrel; 　　6. Screw speed and back pressure: on the premise of meeting the plasticization quality, it should be as low as possible to prevent the possibility of degrading; 　　7. Mold temperature: The cooling of the product has a great impact on the quality, so the mold temperature must be able to accurately control the process. If possible, the mold temperature should be higher. 　　 Four, other issues 　　 In order to prevent the deterioration of the upper surface effect, generally use less release agent when injection molding; when using TPE regrind, generally 5%-10%, not more than 20%.

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Cause analysis and countermeasures of cracking of TPE suction cup material

Customers used TPE and TPR materials before, but the products they made recently are prone to cracks. The composite sucker uses two kinds of soft and hard TPE materials to bond together. The higher hardness part is no problem, and the lower hardness (about 10A) part has many small cracks (cracks) on the surface. 　　Analyze the samples, one is the weather, and the other is the product cracks caused by insufficient material strength. The detailed analysis is as follows: one. weather reason 　　 When the temperature is low, the molecular arrangement of the microstructure of the TPE material (rubber phase) will change, and the relative slippage of the molecules will become difficult, or the tensile properties will become poor. During the use of the suction cup, the TPE parts with lower hardness will be stretched under the action of external force. However, due to the low temperature, the stretchability will become worse and exceed the limit of the material, which will cause the product to break (crack). 　　二. Material strength 　　 The problem of tensile performance mentioned above is that the product cracks due to the decrease of the material's low temperature resistance to tensile deformation. If a matrix material that can maintain tensile properties at low temperatures can be used, this problem will be solved. 　　 To sum up, the sucker product appears to be cracked, the external cause is the cold weather, and the internal cause is the change in the molecular arrangement of the material, and the stretchability is deteriorated. The combined effect of external and internal factors caused cracks in the TPE suction cup. 　　 The above is just a case of cracks in sucker products to analyze the causes of cracks in TPE/TPR products. In fact, there are other reasons for cracks in TPE/TPR products, which should be analyzed in detail according to the material characteristics and actual processing conditions: 　　 1. The TPR of the SBS substrate has poor aging resistance and is prone to aging cracks; 　　 Solution: It is recommended to change to SEBS substrate TPE. 　　2. TPR shoe material with SBS base material, if there are cracks (cracks) during the glue brushing process, it may be caused by glue corrosion; 　　Solution: It should be noted that the glue should not be brushed too much and should not be condensed together. 　　 3. Some TPE products with low hardness and thicker dimensions may suffer from stress shrinkage due to insufficient pressure holding during the injection molding process, and cracks may occur in severe cases. 　　Solution: Strengthen the molding pressure to eliminate stress shrinkage.

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Application advantages of TPE materials in VR virtual equipment

In order to improve the comfort of VR equipment, people in the plastics industry will think of TPE elastomers, which can make VR equipment lightweight and comfortable. VR (Virtual Reality) is actually a computer system that can create and experience a virtual world. If you use a VR device to play a game, then you will feel like you are actually in the game scene, and all the scenes you see in the game will look like reality. Of existence by your side. 　　Why should TPE elastomer, lightweight and VR be linked together? 　　In the current VR equipment, optical equipment similar to the picture below is indispensable, and it is tied to the eyes of people when using it. From the information I have learned, the current optical devices are relatively large in size, and after a long wearing time, they are prone to fatigue, and some users are even dizzy and uncomfortable (it is also related to the experience scene). 　　 This kind of VR device may have a bigger problem for children to wear for a long time. In the development of VR, it will first enter into industries such as games, film and television, and education. A considerable part of the users of this part are young people. They have higher requirements for product wearing comfort. For the elderly in need, long-term It is also unacceptable to wear bulky VR equipment for time. 　　 Therefore, improving the wearing comfort of VR will become an important part of VR technology. There are two current ideas. One is to improve the technology of optical electronic system and change the current design to make VR equipment smaller. The other is to lighten the VR equipment, use lighter and more comfortable materials to make the equipment, and find a better solution combining the above two points. 　　 So from a material point of view, what will VR lightweight look like? 1. The lightweight of VR mainly depends on the marketization speed of VR. In the early concept stage, technicians are more to solve the functional problems of VR, but it is indeed very important in the later stage. At present, the housing of VR equipment has already adopted a large number of plastic materials. Because plastics are generally lighter than metals, and plastics are strong, abrasion-resistant, waterproof, and flexible. From the perspective of raw material cost and processing difficulty, plastics are already the first choice, and the equipment will also use elastomer materials. Engineers will make more optimizations in material selection and design to make them more comfortable to wear. Although some technologies can also produce ultra-light metal materials, they cannot be used in VR devices in the short term due to cost and technical barriers. According to the author's understanding, KRAIBURG TPE also has corresponding grades applied to VR products. Subo TPE is also being developed to replace foreign TPE grades. 2. In optoelectronic systems, such as lenses, the use of optical plastic materials is also a trend. Compared with inorganic glass, there are many types of optical plastics, a wide range of optical parameters, more flexible in optical design, and the current optical plastic processing technology is relatively high. Therefore, plastic lenses will also be widely used in VR equipment. 3. By comparing the development of lightweight cars and wearable devices, plastics and TPE elastomers have always played an important role in these two fields, and according to related industry research reports, the amount of plastics and elastomers used in cars and wearable devices It is increasing year by year. Through similar research, the same trend will be shown in VR equipment, and the development speed mainly depends on the VR technology itself. It is understood that the next 5 years are expected to be the stage of the big development window of VR technology, so for plastics and other industries Perhaps usher in a new outlet. 　　4. The following points should be considered for suitable VR materials: light and strong, comfortable in contact with the skin, environment resistance, thermal safety, electrical safety and biological safety. Among them, biological safety is particularly important. First, the device is wearable and comes into direct contact with the human body. Second, there is no research report that points out the impact of wearing VR for a long time on the human eye and body. This aspect is worthy of attention. VR (virtual reality) technology can be widely used in urban planning, interior design, industrial simulation, restoration of historical sites, bridge and road design, real estate sales, tourism teaching, water conservancy and electricity, geological disasters, education and training, and many other fields, providing it with practicality The solution will become a trillion-level market in the future, and now many giants such as Facebook and Google have invested heavily in the research and development of VR technology. 　　 In short, the current situation of VR is already clear before t

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China's first local standard for children's smart watches released

The "Shenzhen Children's Smart Watch Standardization Technical Document", the first local standard for children's smart watches in the Mainland, compiled by the Shenzhen Consumer Council, was released and implemented. 　　 The Shenzhen Consumer Council stated that this is the country's first local standard led by consumer organizations. From the consumer's point of view, it regulates all aspects of children's smart watches. From the perspective of consumers, the Consumer Council of Shenzhen has fully listened to the voices of consumers, based on the test data of children's smartwatch comparison tests, and compiled this standard in combination with the opinions of industry experts. At the same time, children's smart watch companies such as Xiaotiancai Technology, HKUST Xunfei, Xiaomi, Huawei, and Qihoo participated in the preparation of the standard. 　　 Before this standard, there was no national standard, industry standard, local standard or group standard specifically for children's smart watches at home and abroad. This standard fills the gap in the field of children's smart watches. This standard solves the problems that parents care about, such as whether the watch material is carcinogenic, whether there is personal information leakage, whether the radiation exceeds the standard, whether the battery will explode, how the quality of the call is, whether the positioning is accurate, and the waterproof performance. 　　The standard has clearly stipulated in appearance structure, material safety, electromagnetic radiation, battery safety, temperature, standby time, etc. For example, when testing outdoors, the average distance error should be less than 40 meters, and the standby time should be more than 72 hours. The requirements of some indicators of the standard have reached the international first-class standards. For example, the polycyclic aromatic hydrocarbon indicator of the watchband material has reached the most stringent German certification GS standard in the world: AFPS GS2014:01PAK. The Shenzhen Consumer Council stated that the implementation of this standard will rely on the power of consumers, and will refer to the standard to carry out children's smartwatch comparison test projects and consumer experience and other activities to ensure the smooth implementation of the standard, promote enterprises to improve product quality, and promote the industry. Healthy development.

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Can TPE plastic materials encapsulate metal?

Aluminum alloy and stainless steel metals cannot be directly coated with TPE. This is different from TPE|TPR encapsulated plastic. However, as the application of TPE continues to deepen, more and more products need to use TPE to encapsulate metal.

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