Compatibilization

Last updated

In polymer chemistry, compatibilization is the addition of a substance to an immiscible blend of polymers that will increase their stability. Polymer blends are typically described by coarse, unstable phase morphologies; this results in poor mechanical properties. Compatibilizing the system will make a more stable and better blended phase morphology by creating interactions between the two previously immiscible polymers. Not only does this enhance the mechanical properties of the blend, but it often yields properties that are generally not attainable in either single pure component. [1]

Contents

Block or graft copolymers as compatibilizing agents

Block or graft copolymers are commonly used as compatibilizing agents. The copolymer used is made of the two components in the immiscible blend. The respective portions of the copolymer are able to interact with the two phases of the blend to make the phase morphology more stable. [1] The increased stability is caused by reducing the size of the phase-separated particles in the blend. [2] The size reduction comes from the lower interfacial tension, due to accumulating block copolymers at the many interfaces between the two copolymers. This helps the immiscible blends break up into smaller particles in the melt phase. In turn, these phase separated particles will not be as inclined to consolidate and grow because the interfacial tension is now much lower. This stabilizes the polymer blend to a usable product. [2] An example of this are Ethylene/propylene copolymers. They are able to act as good compatibilizing agents for blends of polypropylene and low density polyethylene. In this specific application, longer ethylene sequences are preferred in the copolymer. This is because cocrystallization also factors into this case, and the longer ethylene sequences will retain some residual crystallinity. [3]

Reactive compatibilization

Reactive compatibilization is a procedure in which immiscible polymer blends are compatibilized by creating copolymers in the solution or melt state. Copolymers are formed when the proper functional groups in each component of the immiscible blend interact in the compatibilization process. These interactions include hydrogen, ionic or covalent bonding. The functional groups that cause these interactions can be the end groups that are already present in the blend polymers (e.g., carboxylic acids or alcohols on polyesters, or amine groups on nylons). Another approach is to add functional groups to the component chains by grafting. The many possible functional groups allow for many types of commercial polymer blends, including polyamide/polyalkene blend systems. [4] There are a number of advantages reactive compatibilization has over using the traditional block or graft copolymer as the compatibilizing agent. Unlike the latter approach, reactive compatibilization does not rely on diffusing pre-formed copolymers. Copolymers form at the interfaces of the two immiscible blends and do not need to be dispersed. In the traditional approach the system needs to be well mixed when adding the copolymers. Reactive compatibilization is also much more efficient than traditional compatibilization. This is because in reactive compatibilization, functional groups are either already present, or easily grafted on the blend components. In the traditional compatibilization, copolymers must be synthesized on a case-by-case basis for the components to blend. [4]

Related Research Articles

Polymer Substance composed of macromolecules with repeating structural units

A polymer is a substance or material consisting of very large molecules, or macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass, relative to small molecule compounds, produces unique physical properties including toughness, high elasticity, viscoelasticity, and a tendency to form amorphous and semicrystalline structures rather than crystals.

Micelle Group of molecules

A micelle or micella is an aggregate of surfactant phospholipid molecules dispersed in a liquid, forming a colloidal suspension. A typical micelle in water forms an aggregate with the hydrophilic "head" regions in contact with surrounding solvent, sequestering the hydrophobic single-tail regions in the micelle centre.

Copolymer Polymer derived from more than one species of monomer

In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained by copolymerization of two monomer species are sometimes called bipolymers. Those obtained from three and four monomers are called terpolymers and quaterpolymers, respectively.

Aggregate (composite) Term used for composite materials

Aggregate is the component of a composite material that resists compressive stress and provides bulk to the composite material. For efficient filling, aggregate should be much smaller than the finished item, but have a wide variety of sizes. For example, the particles of stone used to make concrete typically include both sand and gravel.

Microemulsions are clear, thermodynamically stable isotropic liquid mixtures of oil, water and surfactant, frequently in combination with a cosurfactant. The aqueous phase may contain salt(s) and/or other ingredients, and the "oil" may actually be a complex mixture of different hydrocarbons. In contrast to ordinary emulsions, microemulsions form upon simple mixing of the components and do not require the high shear conditions generally used in the formation of ordinary emulsions. The three basic types of microemulsions are direct, reversed and bicontinuous.

Hot-melt adhesive

Hot melt adhesive (HMA), also known as hot glue, is a form of thermoplastic adhesive that is commonly sold as solid cylindrical sticks of various diameters designed to be applied using a hot glue gun. The gun uses a continuous-duty heating element to melt the plastic glue, which the user pushes through the gun either with a mechanical trigger mechanism on the gun, or with direct finger pressure. The glue squeezed out of the heated nozzle is initially hot enough to burn and even blister skin. The glue is sticky when hot, and solidifies in a few seconds to one minute. Hot melt adhesives can also be applied by dipping or spraying, and are popular with hobbyists and crafters both for affixing and as an inexpensive alternative to resin casting.

Nanocomposite

Nanocomposite is a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers (nm) or structures having nano-scale repeat distances between the different phases that make up the material.

Superabsorbent polymer

A superabsorbent polymer (SAP) is a water-absorbing polymer that can absorb and retain extremely large amounts of a liquid relative to its own mass.

In materials science, a polymer blend, or polymer mixture, is a member of a class of materials analogous to metal alloys, in which at least two polymers are blended together to create a new material with different physical properties.

Copolymers are polymers that are synthesized with more than one kind of repeat unit. Gradient copolymers exhibit a gradual change in monomer composition from predominantly one species to predominantly the other, unlike with block copolymers, which have an abrupt change in composition, and random copolymers, which have no continuous change in composition . In the gradient copolymer, as a result of the gradual compositional change along the length of the polymer chain less intrachain and interchain repulsion are observed.

Short Fiber Reinforced Blends are partial case of ternary composites, i.e. composites prepared of three ingredients. In particular they can be considered as a combination of an immiscible polymer blend and a short fiber reinforced composite. These blends have the potential to integrate the easy processing solutions available for short fiber reinforced composites with the high mechanical performance of continuous fiber reinforced composites. The performance of these complex, ternary systems is controlled by their morphology.

Janus particles type of nanoparticle or microparticle

Janus particles are special types of nanoparticles or microparticles whose surfaces have two or more distinct physical properties. This unique surface of Janus particles allows two different types of chemistry to occur on the same particle. The simplest case of a Janus particle is achieved by dividing the particle into two distinct parts, each of them either made of a different material, or bearing different functional groups. For example, a Janus particle may have one-half of its surface composed of hydrophilic groups and the other half hydrophobic groups, the particles might have two surfaces of different color, fluorescence, or magnetic properties. This gives these particles unique properties related to their asymmetric structure and/or functionalization.

Rubber toughening is a process in which rubber nanoparticles are interspersed within a polymer matrix to increase the mechanical robustness, or toughness, of the material. By "toughening" a polymer it is meant that the ability of the polymeric substance to absorb energy and plastically deform without fracture is increased. Considering the significant advantages in mechanical properties that rubber toughening offers, most major thermoplastics are available in rubber-toughened versions; for many engineering applications, material toughness is a deciding factor in final material selection.

Polymeric materials have widespread application due to their versatile characteristics, cost-effectiveness, and highly tailored production. The science of polymer synthesis allows for excellent control over the properties of a bulk polymer sample. However, surface interactions of polymer substrates are an essential area of study in biotechnology, nanotechnology, and in all forms of coating applications. In these cases, the surface characteristics of the polymer and material, and the resulting forces between them largely determine its utility and reliability. In biomedical applications for example, the bodily response to foreign material, and thus biocompatibility, is governed by surface interactions. In addition, surface science is integral part of the formulation, manufacturing, and application of coatings.

Hybrid materials are composites consisting of two constituents at the nanometer or molecular level. Commonly one of these compounds is inorganic and the other one organic in nature. Thus, they differ from traditional composites where the constituents are at the macroscopic level. Mixing at the microscopic scale leads to a more homogeneous material that either show characteristics in between the two original phases or even new properties.

Novel polymeric alloy (NPA) is a polymeric alloy composed of polyolefin and thermoplastic engineering polymer with enhanced engineering properties. NPA was developed for use in geosynthetics. One of the first commercial NPA applications was in the manufacturer of polymeric strips used to form Neoloy® cellular confinement systems (geocells).

Graft polymer Polymer with a backbone of one composite and random branches of another composite

In polymer chemistry, graft polymers are segmented copolymers with a linear backbone of one composite and randomly distributed branches of another composite. The picture labeled "graft polymer" shows how grafted chains of species B are covalently bonded to polymer species A. Although the side chains are structurally distinct from the main chain, the individual grafted chains may be homopolymers or copolymers. Graft polymers have been synthesized for many decades and are especially used as impact resistant materials, thermoplastic elastomers, compatibilizers, or emulsifiers for the preparation of stable blends or alloys. One of the better-known examples of a graft polymer is high impact polystyrene, which consists of a polystyrene backbone with polybutadiene grafted chains.

Biodegradable athletic footwear is athletic footwear that uses biodegradable materials with the ability to compost at the end-of-life phase. Such materials include natural biodegradable polymers, synthetic biodegradable polymers, and biodegradable blends. The use of biodegradable materials is a long-term solution to landfill pollution that can significantly help protect the natural environment by replacing the synthetic, non-biodegradable polymers found in athletic footwear.

Reactive compatibilization is the process of modifying a mixed immiscible blend of polymers to arrest phase separation and allow for the formation of a stable, long-term continuous phase. It is done via the addition of a reactive polymer, miscible with one blend component and reactive towards functional groups on the second component, which result in the "in-situ" formation of block or grafted copolymers.

The methods for sequence analysis of synthetic polymers differ from the sequence analysis of biopolymers. Synthetic polymers are produced by chain-growth or step-growth polymerization and show thereby polydispersity, whereas biopolymers are synthesized by complex template-based mechanisms and are sequence-defined and monodisperse. Synthetic polymers are a mixture of macromolecules of different length and sequence and are analysed via statistical measures.

References

  1. 1 2 Chen, C., & White, J. (1993). Compatibilizing Agents in Polymer Blends: Interfacial Tension, Phase Morphology, and Mechanical Properties. Polymer Science and Engineering, 33(14), 923-930. Retrieved from http://onlinelibrary.wiley.com/doi/10.1002/pen.760331409/pdf
  2. 1 2 Roe, R.J. (1993) Use of Block Copolymer as Polymer Blend Compatibilizer. U.S. Army Research Office. Retrieved from http://www.dtic.mil/dtic/tr/fulltext/u2/a260435.pdf
  3. ↑ Rudin, Alfred, and Phillip Choi. The Elements of Polymer Science and Engineering. 3rd. Oxford: Academic Press, 2013. Print
  4. 1 2 Tan, N. (1994). Reactive Compatibilization in Immiscible Polymer Blends. Doctor of Philosophy Thesis, University of Maryland. Retrieved from http://www.dtic.mil/dtic/tr/fulltext/u2/a334673.pdf
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.