TPU elastomer polyester and polyether concept of distinction

  • Time of issue:2022-05-20
  • Views:981

TPU elastomer polyester and polyether concept of distinction

  • Categories:Elastomer knowledge
  • Author:SPP
  • Time of issue:2022-05-20
  • Views:981

  TPU's soft section can use a variety of polyols, which can be roughly divided into two types of polyether and polyester systems.

  Polyether (Ether): high strength, hydrolysis resistance and high resilience, good low temperature performance.

  Polyester (Ester): better tensile properties, flexural properties, resistance to friction, as well as solvent resistance and resistance to higher temperatures.

  The difference in the soft segment has the following effects on the physical properties:

  Tensile strength: Polyester > Polyether

  Tear strength: Polyester > Polyether

  Abrasion resistance: Polyester > Polyether

  Chemical resistance: Polyester > Polyether

  Transparency: Polyester > Polyether

  Bacteria resistance: Polyester < Polyether

  Moisture evaporation: Polyester < Polyether

  Low temperature impact: polyester < polyether

  1、 Differences in production materials and formulations

  (1) Polyether TPU production raw materials are mainly 4-4'-diphenylmethane diisocyanate (MDI), polytetrahydrofuran (PTMEG), 1,4-butanediol (BDO), of which the amount of MDI is about 40%, PTMEG about 40%, BDO accounts for about 20%.

  (2) polyester TPU production materials are mainly 4-4'-diphenylmethane diisocyanate (MDI), 1, 4-butanediol (BDO), adipic acid (AA), of which the amount of MDI is about 40%, AA accounts for about 35%, BDO accounts for about 25%

  2、Molecular mass distribution and influence

  The relative molecular mass distribution of polyether follows the Poisson odds equation, and the relative molecular mass distribution is narrower; while the relative molecular mass distribution of polyester diol obeys the Flory odds distribution, and the relative molecular mass distribution is wider.

  In general, assuming the same molecular weight of polyurethane, if the soft segment is polyester, the strength of polyurethane increases with the increase of polyester diol molecular weight; if the soft segment is polyether, the strength of polyurethane decreases with the increase of polyether diol molecular weight, but the elongation increases. This is because the soft segment of polyester itself is more polar, and the high molecular weight is good for improving the strength because of its high structural regularity, while the soft segment of polyether is less polar, and if the molecular weight increases, the relative content of the hard segment in polyurethane decreases and the strength decreases.

  3. Comparison of mechanical properties.

  Polyether, polyester and other oligomeric polyols are composed of soft segments. The soft segment accounts for most of the polyurethane, and the performance of polyurethane prepared by different oligomeric polyols and diisocyanates varies. Polyurethane elastomers and foams made from polyesters with strong polarities as soft segments have better mechanical properties. Because polyurethanes made from polyesters contain polar ester groups, not only can hydrogen bonds be formed between the hard segments of these polyurethanes, but the polar groups on the soft segments can also partially form hydrogen bonds with the polar groups on the hard segments, allowing the hard phase to be more uniformly distributed in the soft phase and acting as an elastic crosslinking point. Some polyesters can form soft segment crystals at room temperature, which can affect the performance of polyurethane. The strength, oil resistance and thermal oxidation stability of polyester polyurethane are higher than those of PPG polyether, but the hydrolysis resistance is worse than that of polyether.

  4. Comparison of hydrolysis stability.

  The hydrolysis resistance of polyester-type TPU is improved after it is protected by carbodiimide. Polyether ester type TPU and polyether type TPU have the best hydrolysis resistance at high temperature.

  The polyesters are susceptible to fracture by water molecules, and the acid generated by hydrolysis catalyzes further hydrolysis of the polyester. The type of polyester has an influence on the physical properties and water resistance of the elastomer. As the number of methylene groups in the polyester glycol raw material increases, the water resistance of the resulting polyester polyurethane elastomer increases. The water resistance is also better with smaller ester group content. Similarly, the water resistance of polyurethane elastomer made from polyester synthesized with long-chain dibasic acid is better than that of polyester polyurethane made from short-chain dibasic acid.

  5. Comparison of microbial resistance.

  Polyester-based flexible TPUs are subject to microbial erosion when in contact with moist soil for a long time, while polyether-based flexible or rigid TPUs and polyether-based TPUs or rigid TPUs are usually not subject to microbial erosion.

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