Interfacial Tension Quantification in Mixed Recycled Polyolefin Streams
Dynamic oscillatory rheology coupled with Palierne model inversion quantifies interfacial tension in mixed polyolefins to control compatibilization economics.
Maleic Anhydride Grafting
Meaning
Chemical attachment of polar functional groups onto a non-polar polymer backbone modifies the interfacial properties of the base resin. This maleic anhydride grafting creates functionalized polymers that can react with fillers, glass fibers or polar matrices to improve adhesion. It is commonly performed on polypropylene or polyethylene in a twin-screw extruder.
Reaction Control
Reactive extrusion utilizing organic peroxides initiates the radical mechanism required for functionalization. During maleic anhydride grafting, the peroxide decomposes to form free radicals that abstract hydrogen atoms from the polymer backbone. Maleic anhydride monomers then attach to these radical sites before chain termination occurs.
Control of the initiator concentration is necessary to limit chain scission and thermal degradation of the polymer. Excessive peroxide concentrations lower the molecular weight, causing reduced viscosity and flash defects during moulding.
Industrial Performance
Glass fiber reinforced polyolefins exhibit superior tensile strength when the matrix contains polymers that have undergone maleic anhydride grafting. The polar anhydride groups react with the silane coupling agents on the glass fibers, creating a robust covalent bond. This strong interface allows efficient stress transfer from the polymer matrix to the fibers under load.
Without this chemical coupling, the composite behaves poorly and fails at low stresses.
Processing Guideline
Molders must manage melt temperatures during processing to prevent the thermal decomposition of the grafted chains. High temperatures can cause the maleic anhydride grafting to release volatile species that create bubbles in the molded parts. These voids degrade the appearance and mechanical properties of the component.
Proper venting during extrusion and molding reduces this risk.
Quantifying Interfacial Tension Reduction in Recycled Polyolefin Blends
Quantifying polyolefin blend interfacial tension via Palierne rheological modeling confirms compatibilizer migration, reducing droplet size and scrap rates.