Difference Between TPU and PU

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, while PU is composed of urethane bonds and is known for its ability to withstand temperature as it does not melt when subjected to high temperatures.

TPU vs PU

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

The structure of TPU is composed of hard and soft materials, when its structure is observed under a microscope, an alteration between its soft and hard segments is noted, on the contrary, PU does not contain this type of properties of segmented structure. TPU is a short form of thermoplastic urethane, while PU is a short form of polyurethane. TPU does not contain crosslinks based on the type of polyols used in it; however, PU may contain crosslinks based on the PF-type polyols used in it.

TPU contains both hard and soft segments in its composition, while PU contains urethane bonds and differs from TPU in this regard. TPU are composed of raw materials such as 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 other hand, PU belongs to a class of reaction polymers. TPU is known for its thermoplastic nature and is known as melt processable, unlike PU which are thermoset as they do not melt when heated.

Comparison chart

TPU belongs to a group of thermoplastic elastomers, which means that they behave like elastic plastics. TPU contains linear flexible coiled and rigid packed segments that can be fused together without degradation of the urethane bonds. They have non-deviating chains and have molecular mass ranges between 15,000 and 40,000, with an alteration temperature below 0 degrees Celsius.

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

TPU can be treated by process such as extrusion, injection molding, and blow molding, etc. This process is dried before use until the moisture content drops below 0.05%. This drying time can take from 3 to 6 hours, which depends on the hardness of the material between 90 and 110 degrees Celsius of temperature.

Its treatment involves considering the speed of the injection molding machine and the temperature of the cylinder, since the high speed of the screw can cause shear degradation. In addition to this, when injecting the nozzle, any cold spot can result in the clogging problem.

TPU does not contain cross-links based on the type of polyols used in it. TPU is made up of raw materials such as Polyester or polyether or polycaprolactones, and also belongs to a category commonly known as block polymers, as its family represents that these contain high levels of elasticity and are incredibly resistant to stress imposed by abrasions and deformations. .

Its structure is composed of hard and soft materials, when its 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 in a chain and give them an important characteristic for their different structures.

What is PU?

PU stands for polyurethane. These are the type of polymeric material that is made up of urethane linkages which are also known as carbamate linkages. Most PUs are thermoset, meaning they don’t melt when heated, but there is also some thermoplastic PU.

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

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

Two main components used in its production are toluene diisocyanate and methyl diphenyl diisocyanate. TDI is used to produce low-density flexible foams or cushions; however, the addition of MDI gives it the property of producing rigid foams. The number of hydroxyl groups present per monomer determines the crosslinking between polymer molecules, which has an impact on the mechanical properties of the polymeric material.

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

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

Due to their varied characteristics, these polyurethanes (PU) are widely used at an industrial level as well as at lower levels. They are widely used in the production of hard and soft foams, as well as in the formation of elastomeric or rubbery products. Its thermosetting capabilities are very useful to derive the required products.

Key differences

1. TPU is an improved form of thermoplastic elastomer and, due to its behavior, they are present with properties of plastics, while PU is considered a polymer that frequently contains urethane chains.
2. TPU is derived from thermoplastic urethane, while PU is derived fm polyurethane.
3. TPU, based on the type of polyols used in it, does not contain crosslinks; however, the PU based on the PF-type polyols used in it may contain crosslinks.
4. TPU, in its composition, contains hard and soft segments, while PU contains urethane bonds and changes TPU in this regard.
5. TPU composed of raw materials such as polyester or polyether or polycaprolactones; on the other hand, PU is made up of polyols and isocyanates.
6. A category that is commonly known as block polymers, to which TPU belongs; on the other hand, PU fits into a class of reaction polymers.
7. The thermoplastic nature of TPU is used throughout the world and is melt processable; In contrast, PU is thermoset and does not melt when heated.