Maleic anhydride (MA) is commonly used in the grafting of fillers to polyethylene (PE) to improve the properties of the polymer matrix.
Chemical Reaction
Maleic anhydride undergoes a chemical reaction with the polyethylene matrix. The double bond in maleic anhydride makes it reactive, allowing it to attach to the polyethylene chains.
Grafting
Maleic anhydride can be grafted onto the polyethylene chains through a process called free-radical grafting. This involves initiating a reaction that forms free radicals on the polyethylene chains, which then react with maleic anhydride molecules.
Bond Formation
Maleic anhydride molecules can bond to the polyethylene chains through covalent bonds. This alters the surface properties of the polyethylene, making it more polar and reactive.
Filler Incorporation
After maleic anhydride is grafted onto the polyethylene chains, fillers such as inorganic materials (e.g., clay, silica) or organic materials (e.g., carbon black) can be incorporated into the polymer matrix. The presence of maleic anhydride groups enhances the compatibility between the filler and the polyethylene matrix.
Percentage of maleic anhydride
The percentage of maleic anhydride (MA) used for grafting onto polyethylene (PE) can vary depending on several factors including the desired properties of the final product, the specific application, and the processing conditions. However, typical levels of maleic anhydride grafting onto polyethylene are often in the range of 0.5% to 5% by weight.
Mixing Maleic Anhydride with Fillers
Dry Mixing: Maleic anhydride powder is mixed with the filler particles using mechanical mixing equipment such as a blender or a mixer. The aim is to achieve a uniform distribution of MA onto the surface of the filler particles.
Solution Mixing
Maleic anhydride can be dissolved in a suitable solvent, and the filler particles are then added to the solution. The solvent is then evaporated, leaving behind a layer of maleic anhydride on the surface of the filler particles.
Activation of Maleic Anhydride
Maleic anhydride may need to be activated before mixing with the filler to enhance its reactivity. This can be achieved by methods such as heating or adding a suitable catalyst.
Mixing Maleic Anhydride-Filler Mixture with Polyethylene
Once the maleic anhydride is uniformly distributed onto the filler particles, the mixture is then combined with polyethylene resin. This can be done using standard polymer processing equipment such as extruders or mixers.