Direct In-Mold Impregnation of Glass Fiber Fabric by Polypropylene with Supercritical Nitrogen in Microcellular...

Area of Science:

• Materials Science
• Polymer Engineering
• Composite Materials

Background:

• Glass fiber fabric (GFF) reinforced polypropylene (PP) composites are widely used.
• Improving interfacial bonding and impregnation in GFF/PP composites remains a challenge.
• Existing methods may not fully optimize the properties of composite foams.

Purpose of the Study:

• To develop and investigate a new injection molding technique for GFF/PP composite foams.
• To evaluate the effect of supercritical nitrogen (SCN) on in-mold impregnation.
• To analyze the influence of processing temperature on composite foam properties.

Main Methods:

• Combined microcellular injection molding and insert injection molding.
• Directly placed GFF in the mold cavity for in-mold impregnation with PP/SCN.
• Investigated two types of GFF (EWR300, EWR600) at varying injection temperatures (230-250 °C).
• Analyzed morphological and tensile properties of the resulting composite foams.

Main Results:

• Initial interfacial bonding was poor due to GFF/PP heterogeneity.
• Unfoamed GFF/PP showed lower specific tensile strength than solid PP.
• GFF/PP composite foams exhibited increased tensile strength, indicating improved impregnation.
• SCN reduced viscosity, aiding in-mold impregnation.
• Higher temperatures improved bonding but negatively impacted foaming and tensile strength.

Conclusions:

• The proposed injection molding technique enhances impregnation and interfacial bonding in GFF/PP composite foams.
• Supercritical nitrogen is beneficial for in-mold impregnation of GFF.
• Processing temperature significantly influences interfacial bonding, foaming, and final tensile strength.
• Material properties vary within the mold cavity due to temperature distribution.