TPE encapsulated PP materials shared by TPE R&D manufacturers in Guangdong for 10 years.
Time：2021-10-10Hits：1418
TPE refers to thermoplastic elastomer, which is a kind of special engineering plastic with rubber elasticity, but which can be directly injection molded without vulcanization. TPE used for encapsulating PP here generally refers to TPE-S elastomer obtained by blending SEBS and SBS.
Encapsulation: In the injection molding industry, encapsulation refers to a process or processing method of adhering soft glue to the surface of hard glue by injection molding. The encapsulating soft glue can be silica gel, PVC, more commonly TPE-S TPE (or TPR), and the encapsulating hard glue material can be ABS, AS, PP, PE, PC, PS, PC/ABS and PA, among which PP and ABS are common. This paper mainly discusses the encapsulation of TPE and PP.
Equipment used for coating glue.
Encapsulation usually involves injection molding of hard PP and then soft TPE, and the whole process is completed by injection molding twice. Two sets of molds can be used (the mold for injecting soft rubber is called an encapsulation mold), which can be injected twice, and two injection processes can be completed in two sets of dies respectively. There are also advanced two-color injection molding machines, which are still two sets of molds, but through the rotation of the disc, one set of equipment is realized to complete the two-color and multi-color injection molding process.
Properties and hardness of TPE for coating.
The formula of the encapsulated TPE is simple, and the common TPE-S TPE can achieve good encapsulation bonding with PP, and no additional functional additives are needed in the TPE formula.
The appearance of TPE coated with PP is transparent or natural plastic particles with approximate specific gravity ranging from 0.92 to 1.2.
The hardness range of TPE of coated PP is usually Shore Hardness 25-80a. By adjusting the formula of TPE, the hardness of TPE, scratch resistance, wear resistance and tensile strength of materials can be changed.
TPE is an environmentally friendly compound, free of halogen, o-benzene 16P and 6P, nonylphenol NP and polycyclic aromatic hydrocarbons PAHS, and meets the relevant environmental testing standards of ROHS,REACH,EN71 en71.
Main applications of TPE encapsulated PP.
TPE rubber-coated PP is mainly used for rubber-coated handles of daily necessities and sports equipment, such as baby carriage wheels, trolley casters, equipment handles, brushes, comb handles, hairdressing equipment, small household appliances and so on. The rubber property of TPE soft rubber gives the product a comfortable grip feeling of softness and skid resistance.
Main processing parameters of TPE encapsulated PP.
Baking materials: For TPE materials stored for a long time, it is recommended to bake them at 60-80℃ for 2 hours before use, so as to reduce the moisture in the raw materials and facilitate the injection molding process to obtain better glossiness of products.
Injection molding processing temperature: The processing temperature is related to the formula brands of different TPE manufacturers, processing injection equipment, products and mold design, etc. It is recommended that the processing injection molding temperature be 150-180℃. The actual processing temperature can be adjusted according to the production situation of the product.
Problems needing attention in injection molding of TPE encapsulation.
■ The compatibility between ■TPE and hard cemented components needs to be matched, and the molecular solubility is close, so that the molecular compatibility is better;
■ Sharp corners should be avoided as far as possible in the design to ensure excellent contact between TPE and hard rubber parts and improve the bonding effect;
■ Through proper exhaust to avoid leaving gas in the mold cavity;
■ Balance the thickness of TPE with the expected touch;
■ Keep the temperature of TPE melt to ensure the bonding effect.
■TPE materials need to be baked and reprocessed for overmolding, so as to reduce the water marks on the surface of products and obtain the effect of uniform surface color;
■ The carrier resin of the selected masterbatch is compatible with TPE and structural member materials;
■ For smooth surfaces, special treatment is required to increase the bonding contact surface between soft glue and hard glue and enhance the bonding effect;
■TPE should have good fluidity. Because the ratio of thickness to size of the coating layer of TPE is very small, TPE usually needs to flow through a long path and thin wall area to fill the mold.
■ the flow length/product thickness ratio of ■TPE is less than 150: 1;
■ Use good adhesive.
Treatment of common encapsulation defects.
Lack of glue: increase the injection molding temperature; Increase injection pressure; Improve material fluidity.
Cleavage and edge overflow: reduce injection molding temperature; Increase the clamping force; Reduce injection pressure; Reduce fluidity from the perspective of formula.
The surface is pitted and dull: increase the injection molding temperature; Bake materials to reduce the moisture of raw materials.
Poor viscosity: fully dry materials before injection molding; Improve injection temperature; Adjust the formula.
Injection molding deformation: strengthening mold cooling; Appropriately extend the mode locking time.
Sticking of products: Add release agent or lubricant (for internal lubricant-release agent, pay attention to the addition amount to prevent release agent from precipitation and migration).
德创化工 (edit：dechuang)
