Summary of Methods to Improve the Compatibility of Polymer Blends

Improving the compatibility of polymer blends is a very important and common topic in polymer materials science and engineering. Since most polymers are thermodynamically incompatible with each other, phase separation occurs, which deteriorates the mechanical properties, optical properties, and thermal stability of the material.

The core idea of improving compatibility is: Reduce the driving force of phase separation (reduce interfacial tension) and enhance the interactions between phase interfaces.Thus obtaining finer, more stable, and uniformly distributed phase morphologies.

The following are the main methods, from commonly used industrial approaches to more cutting-edge academic research:

This type of method does not change the chemical structure of the components but forces dispersion through processing techniques.

Optimize processing technology：

Strong shearBy increasing the screw speed and using an internal mixer, high shear force can be applied to break the dispersed phase into smaller particles.

This is merely a physical "forced dispersion." Once reheated or stored for a long time, the microdomains may reunite and grow (coalescence), resulting in unstable compatibility effects.

The most effective and fundamental method is to enhance the interaction between the two phases through chemical reactions.

1. Introduction of Specific Functional Groups：

By chemically modifying one or more polymers to introduce functional groups capable of interacting with each other, such asCarboxyl group (-COOH), epoxy group (-epoxy), anhydride group (-anhydride), hydroxyl group (-OH), amino group (-NH₂)Etc.

These functional groups can undergo chemical reactions (such as esterification and amidation) during the melt blending process, forming at the interface between the two phases.Covalent bondGreatly reduces interfacial tension and serves an "anchoring" function, preventing phase coarsening.

In the PA6/PP blends, commonly usedMaleic anhydride grafted polypropylene (PP-g-MAH)As a compatibilizer, the PP segment is compatible with the PP phase, while the MAH functional group reacts with the terminal amino groups of PA6, thereby bridging the two phases.

2. Use block or graft copolymers：

This is a classic approach for simulating the stability of polymer colloids.

Add A-b-B (A-B block copolymer) or A-g-B (A-B graft copolymer). In these, the A segment is compatible with polymer A in the blend, while the B segment is compatible with polymer B. The compatibilizer will spontaneously enrich at the interface between the two phases, with its segments integrating into the corresponding phases. Much like an "emulsifier," it effectively reduces interfacial tension and stabilizes the morphology of the dispersed phase.

PS/PP blend can use PS-PP block copolymer; PLA/PBAT blend can use PLA-PBAT block copolymer.

1. Non-reactive compatibilizer：

Usually it is the above.Block or graft copolymersIt does not undergo chemical reactions with the components themselves, but rather reduces interfacial energy through physical interactions (such as chain entanglement and compatibility).

Adding PS-PE block copolymer to the PS/PE blend.

2. Reactive compatibilizer：

This is currently the most widely used type of compatibilizer. Typically, it isPolymers containing reactive functional groupssuch as polymers grafted with maleic anhydride (MAH), epoxy groups, isocyanate groups, etc.

The polymer segments of the compatibilizer are compatible with one phase, while the reactive functional groups chemically react with the functional groups of the other phase during processing to form graft or block copolymers in situ, achieving efficient compatibility.

Common Varieties：

PP-g-MAHUsed for blending polyolefins (PP, PE) with engineering plastics (PA, PET).

PE-g-MAHSame as above.

PS-g-MAH: Used for blending PS with polar polymers.

Ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EGMA)Its epoxy groups can react with various functional groups (carboxyl, amino, hydroxyl), making it a kind of...Universal strong reactive compatibilizerIt is commonly used in PLA, PET, PA and other blend systems.

3. Inorganic Nanoparticle Compatibilizer：

This is an emerging research field. Some nanoparticles (such as silica, clay, etc.) can selectively distribute at the interface of blends, serving as physical barriers to prevent the collision and coalescence of dispersed phase particles, thereby stabilizing the phase morphology.

Similar to the formation mechanism of Pickering emulsions.

Dynamic vulcanization：

Mainly used forThermoplastic Elastomer (TPE)The preparation, especially PP/EPDM (TPV). During the blending process, selective cross-linking (vulcanization) of the rubber phase (such as EPDM) is carried out while applying high-intensity shear. This ultimately forms a stable structure where micron-sized, cross-linked rubber particles are uniformly dispersed in the plastic matrix (PP).

Achieved the ideal state of "thermodynamically incompatible but kinetically stable."

IPN (Interpenetrating Polymer Network) Technology：

By interpenetrating the molecular chains of two polymers and locking them together through chemical crosslinking, the two are forced into a state of “compatibility.” Even though phase separation may still occur at the microscopic level, the size of the phase domains is extremely small (on the nanometer scale) and is permanently fixed, making separation impossible.

In practical applications, the most common and effective method is to add appropriate reactive compatibilizers.The general principle for selecting a compatibilizer is:

Similarity and compatibilityA certain segment of the compatibilizer's chain must be chemically similar to or have good compatibility with one of the components in the blend.

ReactivityThe functional groups on the compatibilizer must be able to effectively react with the functional groups on another component in the blend.

I hope this detailed summary will be helpful to you!