Through the grafting of maleic anhydride onto polypropylene, Coace focuses on improving the interface morphology and gas barrier qualities of blends of polypropylene (PP) and polyethylene terephthalate (PET). A stronger compatibility between PP and PET will result in better mechanical and barrier qualities thanks to the grafting process. The advantages of grafting maleic anhydride onto polypropylene will be discussed, as well as how it affects the interface morphology and gas barrier qualities of blends of PP and PET.

1. Understanding PP and PET Blends

Due to their exceptional qualities, polypropylene (PP) and polyethylene terephthalate (PET) are two of the most commonly used polymers. However, because of their dissimilar chemical structures, mixing these two polymers might lead to poor interfacial adhesion. Reduced mechanical strength and gas barrier qualities are the result of this weak contact. These problems can be solved by grafting polypropylene with maleic anhydride.

2. Grafting Maleic Anhydride onto Polypropylene

In order to graft Maleic Anhydride onto Polypropylene, chains of polypropylene must react. This process improves the polypropylene backbone’s compatibility with PET by adding functional groups made of maleic anhydride. Melt grafting, solution grafting, and reactive extrusion are a few of the techniques that can be used to complete the grafting process. A third component, known as a compatibilizer, is frequently employed to mix incompatible polymers by enhancing the qualities of the blend interface. In order to improve the interfacial bonding force between polypropylene (PP) and polyethylene terephthalate (PET), this study uses polypropylene grafted with maleic anhydride (PP-g-MAH) as a compatibilizer to create high-performance Film with water vapor barrier qualities.  

Figure 1 is the SEM image of 60% PET and 40% PP blend (1) and 60% PET, 37.5% PP and 2.5% PP-g-MAH blend (2)

  The mix without adding PP-g-MAH has clear flaws, as the figure illustrates. Poor compatibility between the two is indicated by the presence of the granular PP phase, which is represented by these flaws as pores. surface adhesion is decreased; also, the copolymer is more evenly distributed and has fewer flaws with the addition of PP-g-MAH, which helps to limit the entry of gas molecules.  

Figure 2 Water vapor permeability of various mixtures, pure PP, and pure PET

The mixes’ water vapor permeability is depicted in Figure 2. The figure illustrates that among all blends, the water vapor permeability of the blends with PP-g-MAH is superior to that of pure PP and the blends without compatibilizer, and the water vapor permeability of the blends with the compatibilizer The blend with 2.5% PP-g-MAH has the lowest water vapor permeability, indicating that adding PP-g-MAH improves the mix’s interfacial characteristics and raises its water vapor barrier.

3. Effect on Interface Morphology

The interface morphology of PP and PET blends is improved by the grafting of maleic anhydride onto polypropylene. The covalent bonds that the functional groups of maleic anhydride create with PET help to increase interfacial adhesion. This reduces phase separation and improves the blend’s mechanical characteristics by causing a more uniform dispersion of PET inside the PP matrix.

4. Improvement of Gas Barrier Properties

The gas barrier qualities of PP and PET blends are also improved by the grafting of maleic anhydride onto polypropylene. The blend’s gas permeability is decreased by the improved interfacial adhesion. The functional groups in maleic anhydride work as barriers that prevent the diffusion of gases across the contact. For applications needing high gas barrier qualities, such packaging materials, this improvement is especially helpful.

5. Grafting Conditions Optimization

Grafting conditions must be improved in order to obtain the required improvements in interface morphology and gas barrier characteristics. The efficiency of the grafting procedure can be affected by variables such grafting temperature, reaction time, maleic anhydride concentration, and initiator type. The PP and PET mixes’ desirable qualities and maximum grafting efficiency are guaranteed by adequate optimization. To enhance the interface morphology and gas barrier qualities of PP and PET blends, maleic anhydride can be grafted onto polypropylene. Maleic anhydride functional groups are added to improve the compatibility of PP and PET, leading to increased mechanical strength and decreased gas permeability. To attain the necessary benefits, grafting conditions must be improved. This method has a lot of promise for a variety of uses, such as packaging materials where improved interface morphology and gas barrier qualities are crucial.