Office Chair Injection Molding Formula

The injection molding formulas for office chairs vary depending on the functions and structural differences of the components. The formulas and material selections for common components are as follows:

1. PP Plastic Chair Body Formula
Using polypropylene (PP) as the base material, suitable for the main structure of the chair. The formula requires adding 1 part of AC blowing agent to achieve lightweighting, 0.8 parts of talc powder as a nucleating agent to improve the uniformity of foaming, 0.3 parts of white oil to lubricate the mold and reduce friction, and colorants to adjust the color according to requirements. During processing, a 1000g low-foaming dedicated injection molding machine should be used, with a foaming expansion ratio of 1.8, a barrel temperature of 185-200°C, a mold temperature of 30°C, an injection pressure of 13 MPa, and a molding cycle of 120-180 seconds. This formula can reduce material costs while ensuring the strength and toughness of the chair.

2. Office Chair Armrest Formula
Armrests need to withstand frequent pressure, and the industry mainly uses PA6-GF30 or PA66-GF30 modified plastics (nylon 6 or 66 with 30% glass fiber). Glass fiber reinforcement can significantly improve material rigidity, heat resistance, and dimensional stability, but it is prone to defects such as fiber floatation, whitening, and shrinkage. Some companies improve these issues by optimizing the modified material formula (such as adding compatibilizers and lubricants) or adjusting the injection molding process (such as increasing the mold temperature and optimizing the holding time) to ensure smooth armrest surfaces and stable structures.

3. Material Selection for Other Key Components

• Headrest and Back Frame: The main body uses PA material + 30% glass fiber reinforced plastic, paired with branded mesh fabric to enhance breathability and comfort.
• Lumbar Support: Selects high-molecular new material TPEE (thermoplastic polyester elastomer), which combines elasticity and support, conforming to the body's curves to relieve lumbar pressure.
• Seat Cushion: Provides cushioning with 6cm thick high-density shaped cotton, enhances breathability with elastic seat fabric, and uses 14mm curved plywood as the support frame to ensure no sagging during prolonged sitting.
• Chair Legs: Uses nylon high legs (radius 350mm), with an independently designed load-bearing structure optimized for both lightweight and stability.
• Wheels: Uses PA straight wheels (60/25 black), with nylon material that is wear-resistant and quiet, suitable for various floor surfaces.

Formula design should consider component functions, costs, and processing feasibility. For example, the PP foaming formula is suitable for lightweighting needs, while glass fiber-reinforced nylon is used for high-strength structural components. In actual production, process parameters need to be adjusted through mold trials to balance material performance and production efficiency.