Due to its superior mechanical qualities, low density, and strong chemical resistance, polypropylene (PP) is frequently utilized in a wide range of applications. However, its uses have been constrained by its poor compatibility with polar materials like polyesters and polyamides. Grafting is one method of modifying PP to make it more compatible with polar materials. Maleic anhydride may react with the PP backbone to introduce polar functional groups onto the surface of the PP, making it a popular grafting monomer for PP.
The maleic anhydride-grafted PP’s characteristics are significantly influenced by the grafting ratio, which is the ratio of PP to maleic anhydride in the feed. This article will go over how the grafting ratio influences the characteristics of PP that has been grafted with maleic anhydride.
Effect of Grafting Ratio on Grafting Degree
The degree of grafting (DOG) is one of the grafting ratio’s most important impacts. The weight of the grafted maleic anhydride divided by the weight of the PP substrate is known as the DOG. The DOG controls how many polar functional groups are added to the PP surface, which impacts how well the maleic anhydride-grafted PP interacts with polar substances.
The DOG has been seen to rise with rising grafting ratio up to a threshold beyond which it falls. This is due to the fact that low grafting ratios result in low DOGs since there isn’t enough maleic anhydride to react with all the PP chains. The quantity of maleic anhydride grafted onto the PP substrate, on the other hand, decreases at high grafting ratios because the majority of the maleic anhydride molecules interact with one another.
Thermal and mechanical properties are impacted by the grafting ratio.
The grafting ratio also affects the mechanical and thermal characteristics of maleic anhydride-grafted PP. The polarity of the PP surface is increased by the grafting of maleic anhydride, which has an impact on the material’s mechanical and thermal stability.
It has been noted that, up to a certain amount, the DOG enhances the thermal stability of maleic anhydride-grafted PP, after which it diminishes. This is such that the maleic anhydride does not appreciably alter the thermal stability of the PP at low DOG by introducing enough polar functional groups. The maleic anhydride molecules, however, can interact with one another to form a crosslinked network at high DOG, which lowers the maleic anhydride-grafted PP’s thermal stability.
The grafting ratio affects the mechanical characteristics of maleic anhydride-grafted PP, including tensile strength and modulus. It has been discovered that, up to a certain point, the tensile strength and modulus of maleic anhydride-grafted PP increase with increasing DOG before beginning to decline. This is such that the mechanical characteristics of the PP may be greatly improved at low DOG, where the maleic anhydride does not introduce enough polar functional groups. The flexibility and toughness of the maleic anhydride-grafted PP are lessened by the brittle crosslinked network that might develop when the DOG is high.
Conclusion
In conclusion, the grafting ratio has a significant impact on the characteristics of PP that has been grafted with maleic anhydride. The grafting ratio has an impact on the DOG, thermal stability, and mechanical characteristics of maleic anhydride-grafted PP. It’s critical to comprehend how the grafting ratio affects the characteristics of maleic anhydride-grafted PP in order to best use it for diverse purposes.
