5 Key Facts on PTMEG

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 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 grades of PTMEG 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 PTMEG and PPG polyols are polyethers, which impart good low-temperature properties and excellent hydrolytic stability to polyurethane elastomers. Both polyether classes exhibit very low Tgs in the soft segment of polyurethanes. The Tg of PTMEG polyol (Tg  ~ 75°C) is lower than that of PPG polyols (~65°C). Additionally, PTMEG has a uniform linear structure, which allows it to tightly pack in a PUR soft segment and undergo stress-induced crystallization. Stress crystallization results in a significant increase in the tensile properties of PTMEG-based polyurethane elastomers. PPG polyols are complex structures with pendant methyl groups that disrupt chain packing and afford non-crystallizable amorphous soft-segment structures. As a result, PPG polyols in a PUR elastomer do not “stress crystallize,” a beneficial feature of the PTMEG soft-segments.

The table below compares the key characteristics and properties of PTMEG and PPG Polyols.

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

Selecting the best polyol for a specific formula can be the difference between making a high-quality product or a low-performing one. The key for making a proper material selection is a good understanding of the inherent characteristics of each polyol chemistry. PTMEG-based polyurethanes are known for superior resistance to hydrolytic cleavage, excellent mechanical properties retention at low temperature, high resiliency, low hysteresis, good processing characteristics, and excellent mechanical and dynamic properties. Strain-induced crystallization of the PTMEG soft-segments, exact di-functionality, and low acid values are all contributing factors to the superior mechanical properties in the associated polyurethane elastomers. These attributes make PTMEG the material of choice for processors specializing in wheels, belts, tires, tubing, abrasion-resistant surfaces, and many other products. 

Compared with polyester-type polyurethanes, PTMEG polyether polyols exhibit best-in-class hydrolysis resistance, resilience, and low-temperature properties. In contrast, polyester polyols possess better mechanical properties such as tensile and tear strength and flex fatigue resistance. The polyester-type polyurethanes are more resistant to oil, grease, solvents. and oxidation.

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

We believe, based on our quality assurance systems, quality control systems, and documentation management, that our PTMEG grades meet 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 cost and performance advantages.  These elastomers are used in a myriad of diverse urethane applications, including wheels, heavy duty casters and tires for lift trucks, mowers and all-terrain vehicles; industrial belts, wiper blades and chute liners; pipe, hose, pump components, and tank liners used in abrasive service; mining, power and oil-field equipment such as gaskets, valves, hydro cyclones, screens, and flotation parts; athletic shoes, boots, and recreational equipment; protective film and 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.