In the wave of modern manufacturing pursuing high efficiency, low carbon and low cost, foam injection molding technology is gradually becoming the key to break through the bottleneck of traditional production. This process of forming a porous structure in the polymer melt by means of a blowing agent not only significantly reduces the weight of parts, but also reduces material consumption and production costs.
Foam injection molding is a special injection molding process that forms parts with a porous honeycomb structure inside the mold cavity by adding a blowing agent to the molten polymer resin. Compared to traditional injection molding, the core difference is that it relies on internal gas expansion to fill the mold, rather than relying solely on solid melt filling by high pressure injection, and the density of the final product can be reduced by 10%-30%.
The core mechanism of foam injection molding is the synergistic effect of “gas expansion - structural curing”: the blowing agent decomposes or releases gas in the molten polymer at high temperature, forming uniformly dispersed micro-bubbles; these bubbles enter the mold cavity along with the melt under the injection pressure, continue to expand and fill the entire cavity; as the mold cools down, it fills the entire cavity with gas. These bubbles enter the mold cavity with the melt under injection pressure, continue to expand and fill the entire cavity; as the mold cools, the polymer melt solidifies and sets, and the bubble structure is permanently retained, resulting in a foam product that is both lightweight and structurally strong. This honeycomb structure reduces weight while dispersing stresses to improve the impact resistance of the part.
Chemical Foaming Agents (CFAs) are additives that decompose and release gases (e.g., carbon dioxide, nitrogen) at high temperatures or under specific pressures, and can be categorized as solid powders, liquids, or masterbatches. Compared with physical blowing agents (e.g. inert gases, volatile liquids), chemical blowing agents have significant advantages: no need for additional gas storage and injection equipment, easy to mix with the resin, lower production costs; the gas release is highly controllable, and can be adapted to the processing temperature range of different resins; wider compatibility with most commonly used engineering plastics, such as polypropylene (PP), acrylonitrile butadiene styrene copolymers (ABS), polyamides (PA), and so on. PA) and most commonly used engineering plastics.
Organic chemical blowing agents: azodicarbonamide (ADC), benzenesulfonyl hydrazine, etc. are representative. Advantage lies in the high gas yield (up to 200-300cc/g), decomposition temperature range (150-250 ℃), suitable for high-temperature processing of engineering plastics; disadvantage is that some varieties of decomposition may produce a slight odor, which can be solved by adding odor inhibitors.
Inorganic chemical blowing agent: common such as sodium bicarbonate, ammonium carbonate and so on. Characterized by low cost, environmental protection and no odor, decomposition products are inorganic salts and water, suitable for food contact grade or low odor requirements of the scene; but the gas yield is lower (50-150cc/g), the decomposition temperature is lower (80-150 ° C), more suitable for low-temperature processing of resins.
Nucleating agent: Although not a foaming agent, it is often used in conjunction with CFAs. Such as talc, silica and other particles, can provide a core for bubble formation, control bubble size (usually stabilize the bubble diameter at 50-200μm) and distribution uniformity, to avoid the emergence of large holes or bubble aggregation defects.
Significant lightweighting advantages: 10%-30% reduction in part weight is crucial for weight-sensitive industries such as automotive and aerospace.
Material and cost savings: reduce the amount of resin per unit of parts, directly reduce the cost of raw materials; at the same time, after the foam melt fluidity to improve, can reduce the injection pressure and clamping force, reduce the energy consumption of the equipment, the overall production costs can be reduced by 15% -25%.
Optimization of part performance: the honeycomb structure disperses the internal stress, reducing the warping and deformation of the part by more than 50%, and significantly improving dimensional stability; in addition, the foam structure also absorbs the impact energy, and the impact strength is improved by 10%-20%.
Improved productivity: The foam structure has a higher heat transfer efficiency, reducing cooling time by 15%-30% compared to traditional injection molding. Combined with cycle time optimization due to lower injection pressure, overall productivity can be increased by more than 20%.
Increased Design Freedom: Lower injection pressure and good melt flow make foam injection molding easy to mold thin-walled (minimum wall thickness of up to 0.5mm), complex geometric parts without worrying about underfilling or flying edges.
Resin selection: Priority should be given to resins with high melt flow rate (MFR) and good thermal stability, such as PP (MFR 10-30g/10min), ABS (MFR 15-25g/10min), etc. For high-temperature application scenarios, engineering plastics such as PA6, PA66, etc., can be used, together with high-temperature-resistant CFAs (decomposition temperature > 220℃).
CFA adding method: There are two common forms, one is to mix CFA powder with resin granule directly (need to ensure the mixing is uniform), the other is to use pre-made CFA masterbatch (concentration 20%-50%), and add it proportionally through the metering feeding system, the amount of CFA added is usually 1%-5% of the weight of the resin, which needs to be adjusted according to the target foam rate (the higher the foam rate, the higher the amount of CFA, but need to avoid exceeding the material's tolerance limit). (the higher the foaming rate, the higher the additive amount, but avoid exceeding the material's tolerance limit).
Plasticizing and mixing: the resin particles and CFA are heated and melted in the screw barrel, the shear effect of the screw makes CFA evenly dispersed in the melt, and at the same time, the initial decomposition of gas is started.
Injection foaming: the molten mixture is pushed by the screw and injected into the mold cavity, the pressure is gradually reduced during the injection process, CFA is fully decomposed to release the gas, and the bubbles fill the whole cavity with the flow of the melt.
Holding Pressure Cooling: A certain holding pressure is maintained to prevent over-expansion or rupture of the bubbles, while the mold is cooled by water, so that the polymer melt is cured and the bubble structure is finalized.
Demolding: After cooling, the mold is opened and the foam part is ejected. Because the foamed structure reduces internal stress, the part usually does not require additional annealing and can go directly to the next process.
Automotive industry: It is the largest application field of foam injection molding, covering parts such as instrument panel skeleton, door interior panel, engine compartment bracket, air conditioning duct, etc.
Electronics industry: It is suitable for thin-walled shells (wall thickness 1-2mm) and internal support structures of smart phones and notebook computers, utilizing the lightweight and cushioning of the foam structure to protect the electronic components and improve the heat dissipation performance at the same time.
Packaging industry: used in the production of high-strength cushioning packaging, fresh food transportation insulation box, etc., the honeycomb void of the foam structure can effectively absorb the impact, and than the traditional solid packaging materials to save more than 30% of raw materials.
Medical industry: Medical grade PP or PE with non-toxic CFAs are used to produce disposable surgical trays and medical device housings. The lightweight design facilitates the operation of medical personnel and meets the requirements of biocompatibility at the same time.
Home Appliances Industry: The weight of parts such as refrigerator inner liner supports, washing machine control panel frames, and air conditioner air guides is reduced by foam injection molding, which lowers transportation costs and reduces the energy consumption of home appliances when they are in operation.
Uneven bubble structure: It is manifested in large local bubbles or scattered distribution, which is mainly caused by poor CFA dispersion or uneven cylinder temperature. Solution: Optimize the screw combination and increase the length of mixing section; add CFA in the form of masterbatch to improve dispersion; ensure the temperature stability of each section of the barrel through infrared temperature measurement.
Surface defects: such as silver wire, pinholes, depressions, etc., mostly caused by too fast gas release or insufficient injection pressure. Solution: add nucleating agent to refine the gas bubbles; reduce the amount of CFA or adjust the barrel temperature to delay decomposition; increase the injection pressure and pressure maintaining pressure appropriately.
Decrease in mechanical strength: Excessive foaming will lead to thin bubble walls and decrease in part strength. Need to determine the optimal foaming rate through testing (usually controlled at 15% -25%), with the selection of high-strength resins (such as glass fiber reinforced PP), or reduce the amount of CFA to balance the lightweight and strength.
Poor process stability: CFA decomposition is greatly affected by fluctuations in temperature and pressure, which easily leads to batch differences. It is recommended to use closed-loop temperature control system to control the barrel temperature accurately (error ≤±2℃); choose CFA with high stability (e.g. ADC masterbatch after surface treatment); calibrate the metering feeding system regularly to ensure the precise amount of additive.
Foam injection molding technology is becoming an important direction for manufacturing upgrading by virtue of the advantages of lightweight, low cost and high efficiency, while the chemical blowing agent, as the core driving force, directly determines the success or failure of the process in terms of its performance and selection. Whether it is automotive weight reduction, electronic thinning or packaging cost reduction, foam injection molding can provide practical solutions. Shuntai brand stands out among many foam agent manufacturers.
Zhejiang Shuntai Rubber & Plastic Technology Co., Ltd. has been focusing on the field of foam blowing agents for 17 years since its establishment in 2008, and is a professional rubber and plastic technology enterprise integrating research and development, production, sales and consulting services.
Shuntaitech has advanced and sophisticated production and testing equipment, as well as a professional technical research and development team, which provides a solid guarantee for product quality and technical support. The production process starts from the source, and each link is strictly controlled to ensure stable and excellent product quality. The company has a wide range of products, including AC blowing agent, white blowing agent, formamide remover, OBSH blowing agent, H blowing agent, microsphere blowing agent, etc., which can fully satisfy the foaming needs of many kinds of plastics and rubbers, such as polyethylene, polychloroethylene, polyphenylene ethylene, polypropylene, natural rubber, nitrile rubber, and so on.
If you are looking for a reliable chemical blowing agent supplier, Shuntaitech Rubber & Plastic Technology is undoubtedly a trustworthy choice, and we look forward to working with you to jointly promote the widespread application and development of foam injection molding technology in various industries.
