Chemistry

Difference Between TPU and PU

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Main Difference

The main difference between TPU and PU is that TPU is a type of thermoplastic elastomer and is known for its property of being elastic and melt-processable, whereas PU is composed of urethane linkages and are known for temperature bearing abilities as they do not melt when are subject to high temperatures.

TPU vs. PU

TPU is an improved form of thermoplastic elastomer that has the properties of plastics because of their behavior, whereas, PU is a polymer that repetitively contains urethane linkages that are also known as carbamate linkages. TPU can be administered by using a method such as extrusion, injection molding, and blow molding, etc., whereas the polyurethane linkages in the PU are formed by condensation polymerization.

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Structure of TPU is composed of hard and soft materials, when their structure is viewed under a microscope, a noticeable alteration between its soft and hard segments, contrary, PU that does not contain these types of segmenting structure properties. TPU is a short form for Thermoplastic urethane, whereas PU is a short form for Polyurethane. TPU does not contain any cross-linkages based on the type of polyols used in it; however, PU can contain cross-linkages based on the type pf polyols used in it.

TPU contains hard and soft segments both in its composition, whereas, PU contains urethane linkages and differ TPU in this regard. TPU compose of raw materials like polyester or polyether or polycaprolactones; on the other hand, PU is composed of polyols and isocyanates. TPU belongs to a category commonly known as block polymers, on the flip side, PU belongs to a class of reaction polymers. TPU is known for its thermoplastic nature and is known melt-processable, contrary to PU, who are thermosets as they do not melt when heated.

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Comparison Chart

TPUPU
An improved form of thermoplastic elastomer is known as TPU.A polymer that can have urethane linkages continually is called as PU.
Abbreviation
Thermoplastic PolyurethanePolyurethane
Cross-Links
That has no cross-links for polyols used in it.These can have cross-links that are based on the type of polyols used in it.
Composition
It contains hard and soft segments both in its composition.It contains urethane linkages.
Raw Material
These are made from polyether or polyester or polycaprolactones.These are made from Polyols and isocyanates.
Category
These are a form of block polymer.They belong to the family of reaction polymers.
Nature
These are thermoplastic materials.Most of these are thermosets, but some of these are thermoplastic materials as well.
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What is TPU?

TPU belongs to a group of thermoplastic elastomers, which means they behave like elastic plastics. TPU contains linear flexible coiled and rigid packaged segments that can merge without the degradation of urethane linkages. They have undeviating chains and have molecular mass ranges from 15000 and 40000, with an alteration temperature below 0 degrees Celsius.

The TPU is made from polyols that have a molecular weight between 600 and 4000, the chain extenders in its segments contain molecular weight in between 61 to 4000 diisocyanates. Because of the variety due to mixtures of rigid and flexible parts, these are expressed as soft and flexible segments with a high modulus.

TPU can be treated by using a procedure such as extrusion, injection molding, and blow molding, etc. This process is then dried before use until the moisture content gets below 0.05%. This drying time may take 3 to 6 hours, which depends upon the hardness of the material between 90 and 110-degree Celsius temperature.

Its treating involves consideration in the speediness of the injection molding machine, and the barrel temperature as high screw speed can cause shear degradation. In addition to this, while injecting the nozzle, any cold point can result in the problem of clogging.

TPU does not contain any cross-linkages based on the type of polyols used in it. TPU compose of raw materials as Polyester or polyether or polycaprolactones, and it also belongs to a category commonly known as block polymers as their family represents that these contain high levels of elasticity and are incredibly resistant towards stress imposed by abrasions and strains.

Their structure is composed of hard and soft materials, when their structure is viewed under a microscope, a noticeable alteration between its soft and hard segments gives a clear picture of its structure. These hard and soft segments are linked together in some chain and give them an important characteristic for their different structures.

The chained form of hard and soft segment gives this an advantage for amendments that can be made to its structure, and material with required hardness or softness can be obtained. As when the segments are manipulated by changing its number, it changes its properties. It includes varying hardness and softness. TPU coating has its multiple uses, as these coatings have applications in a multitude of industries not only in engineering rubber and plastics, but it is also used in strengthening other materials too.

What is PU?

PU stands for polyurethane. These are the type of polymer material that is composed of urethane linkages which are also known as carbamate linkages. Most of the PU are thermosets, which means they do not meltdown when heated, but there is some thermoplastic PU as well.

Due to the absence of urethane monomers, they differ from other polymers. These other polymers differ in their name based on the monomers used in their production, as PU is a polymer of ethylene. The polymers’ name is based on the linkages that repetitively present in the polymer, as in this case, the linkages are urethane linkages, which can be presented as (-R-NH-C(=O)-O-). This PU is produced by initiating a reaction between alcohols.

The alcohols that take part in the reaction have more than one OH group; that’s why they are called polyols. The isocyanates are known for the property of having more than one reacting NCO group. For the production of PU the isocyanates, polyols are produced.

Two major components that are used in its production are toluene diisocyanate and methyl diphenyl diisocyanate. TDI is used in producing low-density flexible foams or cushions; however, the addition of MDI gives it the property of production of rigid foams. The number of hydroxyl groups presents per monomer in determining the cross-linkage between polymer molecules, which have an impact on the mechanical properties of the polymer material.

When two OH groups per monomer are mixed with TDI or MDI, a linear PU is formed. The PU linkages in the polyurethane are formed by condensation polymerization. If the polyols contain more than two hydroxyl groups per monomer, a cross-linked PU is produced. That’s why the name PU is given to the materials that are produced with the reaction between isocyanates and polyols.

Polyurethanes (PU) are very adaptable as they are used in the formation of solid goods as well as in foams and sponges too. In addition to its use mentioned above, they can be thermoplastic as well as thermosetting. Its properties change by varying the basic substances used in its production. As already mentioned above, OH group per monomer leads to a difference in its structure, as well as short-chain diol long-chain diol along with diisocyanate vary its properties.

Based on OH groups used in its production, they can be classified. As present in the case of polyether polyurethane or polyester PU. They are higher resistant to hydrolysis and lower temperature transition. It also has better resistance to oils and fuels due to its properties.

Based on its varied characteristics, these polyurethanes (PU) have great use at the industrial level as well as lower levels. They are widely used in the production of hard and soft foams as well as used in the formation of rubbery or elastomeric products. Their thermosetting abilities are of widely useable in deriving required products.

Key Differences

  1. TPU is an enhanced form of thermoplastic elastomer, and because of their behavior, they are present with properties of plastics, whereas, PU is considered as a polymer that frequently contains urethane chains.
  2. TPU is derived from Thermoplastic urethane, whereas PU is derived from Polyurethane.
  3. TPU, based on the type of polyols used in it, does not contain any cross-linkages; however, PU based on the type pf polyols used in it can contain cross-linkages.
  4. TPU, in its composition, contains both hard and soft segments, whereas, PU contains urethane linkages and change TPU in this respect.
  5. TPU made up of raw materials like polyester or polyether or polycaprolactones; on the other hand, PU is formed of polyols and isocyanates.
  6. A category which is commonly known as block polymers, from which TPU belongs; on the flip side, PU fits into a class of reaction polymers.
  7. The thermoplastic nature of TPU is used worldwide, and it is melt-processable; on the converse, PU is thermosets, and they do not melt when heated.

Conclusion

The above discussion concludes that the TPU is a kind of thermoplastic elastomer and does not contain any cross-linkages, whereas, PU is composed of urethane linkages and can contain cross-linkages.

Harlon Moss

Harlon currently works as a quality moderator and content writer for Difference Wiki. He graduated from the University of California in 2010 with a degree in Computer Science. Follow him on Twitter @HarlonMoss

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