A polymer blend or polymer mixture is a member of a class of materials analogous to metal alloy

Alloy

An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

s, in which at least two polymer

Polymer

A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

s are blended together to create a new material with different physical properties. Section 3.2 Polymer Mixtures

History

During the 1940s, '50s and '60s, the commercial development of the new monomers for production of the new polymers seemed endless. In this period, it was discovered that the development of the new techniques for the modification of the already existing polymers, would be economically viable.

The first technique of modification developed was the polymerization, in other words, the joint polymerization of more than one kind of polymer.

A new polymers modification process, based on a simple mechanical mixture of two polymers first appeared when Thomas Hancock

Thomas Hancock

Thomas Hancock VC was an English recipient of the Victoria Cross, the highest and most prestigious award for gallantry in the face of the enemy that can be awarded to British and Commonwealth forces.-Details:...

 got one mixture of natural rubber with Gutta-percha

Gutta-percha

Gutta-percha is a genus of tropical trees native to Southeast Asia and northern Australasia, from Taiwan south to the Malay Peninsula and east to the Solomon Islands. The same term is used to refer to an inelastic natural latex produced from the sap of these trees, particularly from the species...

. This process generated a new polymer class called Polymer Blends.

Basic Concepts

Polymer blends can be broadly divided into three categories:

• Immiscible polymer blends (heterogeneous polymer blends): This is by far the most populous group. If the blend is made of two polymers, two glass transition temperatures will be observed.
• Compatible polymer blends: Immiscible polymer blend that exhibits macroscopically uniform physical properties. The macroscopically uniform properties are usually caused by sufficiently strong interactions between the component polymers.http://goldbook.iupac.org/CT07581.html
• Miscible polymer blends (homogeneous polymer blend): Polymer blend that is a single-phase structure. In this case, one glass transition temperature will be observed.

The use of the term polymer alloy for a polymer blend is discouraged, as the former term includes multiphase copolymers but excludes incompatible polymer blends.http://goldbook.iupac.org/P04736.html

Examples of miscible polymer blends:

• Homopolymer - Homopolymer:
  • Polyphenylene oxide (PPO) - polystyrene
    Polystyrene
    Polystyrene ) also known as Thermocole, abbreviated following ISO Standard PS, is an aromatic polymer made from the monomer styrene, a liquid hydrocarbon that is manufactured from petroleum by the chemical industry...
    
     (PS): Noryl
    Noryl
    Noryl is a blend of polyphenylene oxide and polystyrene that was developed by General Electric Plastics in 1966 . It is a rare example of a homogeneous mixture of two polymers. Most polymers are incompatible with one another, so tend to produce separate phases when mixed...
    
     developed by General Electric
    General Electric
    General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
    
     Plastics in 1966 (now owned by SABIC
    SABIC
    SABIC is a diversified manufacturing company, active in chemicals and intermediates, industrial polymers, fertilizers and metals. It is the largest public company in Saudi Arabia as listed in Tadawul, but the Saudi government still owns 70% of its shares...
    
    ). The miscibility of the two polymers in Noryl is caused by the presence of an aromatic ring in the repeat unit
    Repeat unit
    An essential concept which defines polymer structure, the repeat unit or repeating unit is a part of a polymer chain whose repetition would produce the complete polymer by linking the repeat units together successively along the chain, like the beads of a necklace.A repeat unit is sometimes called...
    
    s of both chains;
  • Polyethylene terephthalate
    Polyethylene terephthalate
    Polyethylene terephthalate , commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination...
    
     (PET) - Polybutylene terephthalate
    Polybutylene terephthalate
    Polybutylene terephthalate is a thermoplastic engineering polymer, that is used as an insulator in the electrical and electronics industries. It is a thermoplastic crystalline polymer, and a type of polyester...
    
     (PBT);
  • Poly(methyl methacrylate) (PMMA) - Polyvinylidene fluoride
    Polyvinylidene fluoride
    Polyvinylidene fluoride, or PVDF is a highly non-reactive and pure thermoplastic fluoropolymer.PVDF is a specialty plastic material in the fluoropolymer family; it is used generally in applications requiring the highest purity, strength, and resistance to solvents, acids, bases and heat and low...
    
     (PVDF);
• Homopolymer - Copolymer:
  • Polypropylene
    Polypropylene
    Polypropylene , also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging, textiles , stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes...
    
     (PP) - EPDM;
  • Polycarbonate
    Polycarbonate
    PolycarbonatePhysical PropertiesDensity 1.20–1.22 g/cm3Abbe number 34.0Refractive index 1.584–1.586FlammabilityV0-V2Limiting oxygen index25–27%Water absorption – Equilibrium0.16–0.35%Water absorption – over 24 hours0.1%...
    
     (PC) - Acrylonitrile butadiene styrene
    Acrylonitrile butadiene styrene
    Acrylonitrile butadiene styrene is a common thermoplastic. Its melting point is approximately 105 °C ....
    
     (ABS): Bayblend, Pulse, Anjablend A.

Polymer blends can be used as thermoplastic elastomer

Thermoplastic elastomer

Thermoplastic elastomers , sometimes referred to as thermoplastic rubbers, are a class of copolymers or a physical mix of polymers which consist of materials with both thermoplastic and elastomeric properties...

External links

• Miscible polymer blends: http://pslc.ws/macrog/blend.htm
• Immiscible polymer blends: http://pslc.ws/macrog/iblend.htm