Research on the Quality of Curved Pipes Formed via Gas‐Projectile Assisted Co‐Injection Molding

ABSTRACT Curved pipes were prepared using the Gas‐Projectile‐Assisted Co‐Injection Molding Overflow (GPACIM‐O) process, with long glass fiber‐reinforced polypropylene (LGFR‐PP) as the outer layer material and polypropylene (PP) as the inner layer material. The effects of cavity deflection angles (0°, 30°, 60°) on the microstructure and properties of the pipes were investigated. The results indicate that both the total wall thickness and the inner layer wall thickness of the pipes gradually decrease along the penetration direction, while the outer layer wall thickness increases. With an increase in the cavity deflection angle, the standard deviation of the pipe wall thickness gradually increases, and the circumferential uniformity decreases. The cavity deflection angle significantly influences the degree of glass fiber orientation in GPACIM pipes: as the deflection angle increases, the fiber orientation becomes more disordered, and the proportion of fibers oriented at large angles or perpendicular to the melt flow direction increases. Furthermore, the degree of fiber orientation gradually deteriorates with increasing distance from the mold wall, and the distribution density becomes uneven. Simultaneously, the distribution range of fiber lengths narrows, and the average residual fiber length decreases. The pressure resistance of GPACIM pipes gradually decreases with an increase in the cavity deflection angle.