In order to strengthen the cohesive force of the phase interface layer, promote phase dispersion, stabilize the morphological structure, and leverage the bonding force between polymer molecules to lessen the degradation of the two phases, compatibilizer should be added to the mixture of two or more polymer components. Phase separation is decreased and the overall performance of polymer blending is improved due to the interfacial tension between the components.
Compatibilizers must be added since polyolefins like PE and PP lack good compatibility despite having complementing characteristics. The PE/PP blend’s two components are insufficiently compatible with one another, but after 15% of the compatibilizer EPR is added, the morphological structure is homogenized, the phase interface bonding is strengthened, and the performance is noticeably enhanced. Another illustration: The formability and full incompatibility of PBT and PPO. PBT and PPO are more compatible when 5% to 8% PS graft compatibilizer is added with epoxy group, which also helps with processing and mechanics. Performance has improved significantly.
2. Cross-linking reaction
A common chemical alteration in the plastics sector is the polymer cross-linking process. Cross-linking is the term for the chemical reaction that forms chemical bonds between polymer macromolecular chains. When cross-linking occurs between polymers that are incompatible with one another, the compatibility of the two polymers can be significantly increased, and even the incompatible parts can become compatible parts.
Chemical and physical cross-linking are the two categories into which cross-linking can be subdivided. Using radiation to chemically cross-link LDPE/PP is one example. Physical cross-linking is what causes crystallization. The morphological structure of the generated blend is solidified as a result of the crystallization of orientated fiber tissue, creating a compatibility effect.
Most businesses employ dynamic cross-linking to increase the compatibility of polymer mix components. Without sacrificing the blend’s intrinsic thermoplasticity, dynamic cross-linking can make the blend compatible and enhance its overall performance. Thermoplastic molding processing techniques can still be used to process it.
The following are the prerequisites for the dynamic cross-linking of polymers:
The dispersed polymer’s particle size should be between 1 and 2 m; the surface tension difference between two or more polymers should be between 0.5 and 3.0 mN/m; and the plastic resin’s crystallinity should be between 15% and 30% or higher.
PP/EPDM, PE/EPDM, PP/CPE, PP/PA, PP/butyl rubber, PP/natural rubber, PA/nitrile rubber, etc. are examples of dynamic cross-linking types.
3. IPN innovation
Interpenetrating network technology is another name for IPN technology. Physical blends can be manufactured chemically using the interpenetrating network (IPN) technique to create interpenetrating network polymer (IPN) blends. In order to create the effects of “forced mutual accommodation” and “molecular synergy” at the molecular level, two polymer molecules penetrate each other in the mix system. This is a relatively effective way for increasing the compatibility of blends.
4. Adding interaction groups between the polymer’s constituent parts
To improve compatibility between polymer molecular bonds, ionic or ion-dipole functional groups are inserted into the polymer components. Promote the interaction of the original acidic or basic groups on the molecular chain, resulting in proton transfer during blending, to achieve compatibility. Introduce hydrogen bonds or ionic connections between polymer components.
Because hydrogen bonds can form between molecular chains, for instance, PMMA/PVA blending has strong compatibility; another example: PS is given 5%mol of the -SO3H group, and 5%mol of ethyl acrylate is combined with it. Vinyl pyridine can be copolymerized, and then the two can be combined to create a composite substance with exceptional stability.
5.Modify the molecular chain composition
Because PS is a weakly polar polymer, it is challenging to combine it with other polymers. However, due to a change in its molecular mid-chain structure, SAN, a copolymer of styrene and acrylonitrile, can be blended with several polymers, including PC, PVC, PSF, and other resins. Polyvinyl chloride and non-polar polybutadiene are incompatible, however the copolymer of butadiene and acrylonitrile is compatible with polyvinyl chloride.
Although EVA, a copolymer of ethylene and vinyl acetate, has strong compatibility with PVC, PE and PVC are also difficult to mix. While PE and PA are incompatible, the copolymer of ethylene and acrylic acid can create a system that is. Therefore, changing the molecular chain structure of polymers and improving polymer compatibility by copolymerization is a more efficient process.
