The basic idea behind compatibilization is to lower the energy present at the interface between two polymers in order to improve adhesion and promote dispersion. In general, adding compatibilizer can also provide morphology with finer dispersion, better regularity, and stability. Compatibilizers frequently enhance mechanical qualities and surface quality. There are three different categories of compatibilizers:

•Non-reactive block copolymer

Block copolymers that are reactive and function in situ • Polar copolymers that don’t react to each other (polar interactions that are particular)

•Compatibility with block copolymers

The compatibility concept of block copolymers or graft copolymers is depicted in the figure below. In reality, compatibilizers function as “surfactants” and migrate preferentially to the contact to lower surface tension. The blue block is compatible with polymer B (dispersed phase), while the red block is suitable with polymer A (matrix). Better interfacial adhesion and dispersion will be the end consequence.

Compatibility of block copolymers  

Block copolymer compatibility

Block copolymers also have a propensity to result in gums, just like surfactants. Compatibility enhancer typically has a very high content (possibly greater than 5%). Block copolymers are scarce and frequently expensive in the commercial marketplace, just like all polymers.

Reactive functional copolymers’ compatibility

As a result of a reaction between the functional groups of various polymers, the principle of action is to produce grafted block copolymers “in situ” at the interface. Functionalized copolymers react with the functional groups of the dispersed phase and are miscible with the matrix.  

The mechanism of action of reactive functional groups

The benefit is: •Adjustable responsiveness • Effectiveness Usually less expensive than block copolymers

Manipulated polymer

Maleic anhydride is frequently the reactive monomer. The most popular family of functionalized polymers utilized as compatibilizers and adhesion boosters is maleated polymers. They can be made immediately by polymerization or indirectly through y-modification during compounding (this is known as reactive extrusion). Amine, epoxy, and eventually alcohol groups can all react with anhydride groups. In order to make PA/polyolefin blends compatible, Figure 8 depicts an example of the reaction between maleated polymers and the -NH2 end groups of polyamide or nylon 6,6.   Also utilizing maleic resin are: •Increases the adherence of plastic to metal. •Increase cohesiveness between fillers (such mica, wood, and ATH) and polymers. •Better adherence of fiberglass and polymers in thermoplastics and composites •Shock adjustments epoxy plastic There are other commercially available epoxy polymers. Typically, glycidyl methacrylate is the major modification agent. With NH2, anhydrides, acids, and alcohol groups, they are quite reactive. According to the mechanism depicted in the picture below, it is advised to make polyesters (PET, PBT) and olefin polymers or elastomers compatible.  

compatibility of polar copolymers that are not reactive

The idea is to produce certain polar interactions, like hydrogen bonds or van der Waals forces, to lower interfacial tension and boost adhesion. The compatibilizer must create particular interactions with the other phase and be compatible with one phase (often a nonpolar one). The mechanism of action is represented in the figure above.

Applications for adhesion promoters

Plastic alloy

Many developers frequently combine polymers to get the best balance of qualities in order to suit the demands of the polymer business. This method eliminates the creation of new macromolecules, which is frequently more time-consuming and expensive than polymer alloying, and provides for a great degree of freedom in property tuning. Commercially accessible polymer mixes include PBT/PC, PC/ABS, and PP/PA

reuse and recycle

Multi-layer structures are employed in various packaging applications. These layers are typically combined to provide the final product a blend of the various characteristics of the polymers used, such as: •Barrier effectiveness •Strict seal • Chemical or moisture resistance •rigidity …often not possible with only one polymer. A multilayer film’s general structure is as follows:     The exterior layer is typically inert or sealable, and the core layer is typically the barrier layer. Cohesion between the layers is good thanks to the adhesive layer. Due to increased worries about environmental issues, landfill space, and care, multilayer film packaging waste has emerged as a significant issue of global concern. Compatibilizers must be introduced throughout the recycling process to the used materials in order to make them compatible in order to improve material performance and stability. Examples of multilayer constructions and suggested compatibilizers are provided in the table below.

For wire and cable compounds, flame retardants and coupling agents

Many applications necessitate the use of halogen-free flame retardants in order to satisfy the requirements and standards of cable manufacturers. Aluminum trihydrate (ATH) is the most popular flame retardant utilized for this purpose. The polymer matrix must have 60 to 65% ATH added to it in order to achieve effective flame retardancy, which lowers the material’s initial mechanical characteristics. However, mechanical characteristics, particularly elongation at break and tensile stress at break, are also important in cables. It’s important for the filler and matrix to adhere well in order to maximize mechanical qualities. A coupling agent can be used to accomplish this. While silanes can be utilized for this, functionalized polyolefins provide good alternatives because they also give the material some flexibility and are simple to work with.  

Glass fiber-filled polypropylene coupling agent

Tackifiers operate as coupling agents in mineral- and glass-filled polypropylene while the polymer backbone transforms into a miscible state with the base polypropylene (see Mechanism of Action). It fuses the filler to the polymer matrix in this manner. Additionally, this increases the filler’s surface wettability, filler dispersion, and mix homogeneity. The composite’s tensile strength and impact strength have significantly improved as a result. The desired physical qualities of the finished combination determine the impact modifier that is most suited for your application. There are grades available on the market that provide impact strength or stiffness (flexural modulus). Other circumstances, such as pultrusion applications where adequate surface wetting of the glass roving is required, call for high flowability of the base resin and extremely high grafting rates. The amount of coupling agent needed to maximize physical qualities is typically between 2% and 5%, but this varies depending on how well the mixing equipment mixes.

A different TPO-filled coupling agent

The tackifier in mineral-filled polypropylene can react with the functional groups on the filler surface while the polymer backbone is miscible with the basic polypropylene. PP/Calcium Carbonate. It works to link the filler into the polymer matrix in this way. Additionally, this enhances the filler’s surface wettability, filler dispersion, and mix homogeneity. The composite’s tensile and impact strength significantly increase as a result.