5 Key Facts About Polytetramethylene Ether Glycol (PTMEG) in Polyurethane Elastomers

Polytetramethylene Ether Glycol (PTMEG) is the premier polyether polyol used worldwide in the manufacture of high-performance polyurethane elastomers. Known for its many performance attributes and advantages, PTMEG is used in a variety of applications, including polyurethane elastomers, prepolymers, coatings, adhesives, cast polyurethane resins, TPUs, protective films, spandex fibers, and much more. 

Processors know PTMEG as a high-performance polyol capable of formulating polyurethane elastomers in several positive directions, whether it’s low temperature flexibility, dynamic properties, resiliency, hydrolytic stability, or abrasion resistance. 

In this article, we outline five relevant facts regarding the use of PTMEG polyols in high-performance polyurethane elastomers to assist our prospective customers in optimal product selection.

1. A Broad Grade Slate of PTMEG Polyols Available for Selection

As a global supplier of chemicals for multiple targeted industries, Gantrade offers a full slate of PTMEG polyols available in a broad range of molecular weights. While the workhorse grades of polytetramethylene ether glycol (PTMEG) are the 1000, 1800, and 2000 MW diols, the PTMEG 220 and 650 grades are notable, in that formulators find them easier to handle low viscosity liquids at room temperature. In addition, PTMEG 1400 offers properties intermediate between the workhorse grades. PTMEG 3000 is a grade of interest for customers seeking enhanced resiliency and rebound, and abrasion resistance.

The different PTMEG polyol grades available from Gantrade are offered in a variety of physical forms, which in turn affect processing. PTMEG  650, for example, has a softening point of 11°C (52°F) and can be a liquid at room temperature. PTMEG 1000, along with the other offerings in higher molecular weight grades, appears in the form of low-melting waxy solids, with softening points starting at about 24°C (75°F).

2. The Benefits of PTMEG Polyether Polyols vs. PPG-based Polyether Polyols

Both polytetramethylene ether glycol (PTMEG) and polypropylene glycol (PPG) polyols are polyethers, valued for imparting excellent low-temperature flexibility and strong hydrolytic stability to polyurethane elastomers. These polyether chemistries share very low glass transition temperatures (Tg) in the soft segments of polyurethanes.

• PTMEG polyol grades typically have a Tg around –75 °C, significantly lower than the ~–65 °C Tg of PPG polyols.
  
  
• PTMEG’s uniform, linear molecular structure enables tight chain packing within polyurethane soft segments. This structure promotes stress-induced crystallization, which increases tensile strength and overall mechanical performance.
  
  
• In contrast, PPG polyols have branched structures with pendant methyl groups that disrupt chain packing. This results in amorphous, non-crystallizable soft segments and prevents the beneficial stress-crystallization effect seen with PTMEG.

The result: PTMEG vs PPG polyols comparisons consistently show that PTMEG delivers superior tensile properties, resiliency, and durability in polyurethane elastomers, making it the preferred choice for demanding industrial applications.

The table below compares the key characteristics and properties of PTMEG and PPG Polyols, highlighting why formulators often choose PTMEG for demanding applications. 

3. The Benefits of PTMEG Polyether Polyols vs. Polyester Polyols

When selecting a polyol, it’s important to compare the inherent characteristics of each chemistry. Here’s how PTMEG polyol grades differ from polyester polyols:

• PTMEG polyols
  - Superior hydrolysis resistance
  - Excellent low-temperature resilience and property retention
  - Low hysteresis with high resiliency and dynamic performance
  - Strong processing characteristics and strain-induced crystallization
  
  
• Polyester polyols
  - Higher tensile strength, tear strength, and flex fatigue resistance
  - Greater resistance to oil, grease, solvents, and oxidation
  - More susceptible to hydrolytic breakdown compared to PTMEG
  
  

Superior hydrolysis resistance of PTMEG-based PURs

We have compared the hydrolysis resistance of MDI/BDO elastomers based on PTMEG 2000 to elastomers based on two adipate polyester polyols of MW 2000. The elastomers were prepared by chain-extending MDI prepolymers with BDO in the molar ratio of 1:3:2, Polyol/MDI/BDO. The NCO/OH index was 1.05. 

Tensile strength retention was observed under extreme conditions of superheated steam at 105 °C and 100 % relative humidity.  The results are shown in the figure below for PTMEG 2000 vs. 1,6-hexanediol adipate and 1,4-butanediol adipates. After 72 hours at 105 °C and 100 % RH, the PTMEG/MDI/BDO elastomer showed a 67% retention of the initial tensile strength. The HDO adipate and the BDO adipate elastomers showed 72-hour retention of 20% and 12%, respectively. The data below, derived under extreme conditions, demonstrates the superior hydrolysis resistance of the PTMEG polyols.  

4. Conformance with Regulatory Statements

Our PTMEG grades conform to the compositional requirements listed in the following food contact regulations:

USA - FDA 21 CFR Regulations

PTMEG grades are listed as follows under indirect food additives, adhesives, and components of coatings, and as polymers:

• 175.105   "Adhesives" under section (c)(05)
• 177.1590 "Polyester elastomers"
• 177.1680 "Polyurethane resins" under (a)(2)
• 177.2600 "Rubber articles intended for repeated use”
  
  

Europe - EU Regulation 10/2011

PTMEG grades are compliant with EU Regulation 10/2011. The monomer, Tetrahydrofuran (FCM substance No: 246, Ref No: 25150, CAS 109-99-9), is listed in Annex I with the following restriction: SML = 0.6 mg/kg

Based on our quality assurance systems, quality control systems, and documentation management, we are confident our PTMEG grades meet and exceed the criteria set out in EC Regulation No: 202.

5. A Broad Spectrum of Application Arenas

Cast polyurethane elastomers and TPUs using PTMEG as the soft segment are among the most useful polyurethane materials, offering both cost and performance advantages. These materials deliver the balance of durability, resiliency, and processing efficiency that formulators and end users depend on.

They are used across a wide spectrum of urethane applications, including:

• Transportation & mobility: used in wheels, heavy-duty casters, and tires for lift trucks, mowers, and all-terrain vehicles
  
  
• Industrial equipment: used in belts, wiper blades, chute liners, pipe, hose, pump components, and tank liners for abrasive service
  
  
• Mining, power & oilfield: used in gaskets, valves, hydrocyclones, screens, and flotation parts
  
  
• Consumer & recreational goods: used in athletic shoes, boots, and recreational equipment
  
  
• Specialty uses: used in protective films, interlayers, and medical devices
  
  
  

Contact the Experts at Gantrade For Your PTMEG Polyol Supply

Known around the world as experts in PTMEG and other polyols, the team at Gantrade is ready to help you select the right product varieties for your distinct industry applications. To learn more about how our global supply chain can benefit your production needs, contact us today. We’ll use more than 40 years of experience and expertise, along with the latest market data and product resources, to make sure you get the products your applications require, every time.

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