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FAQ | HQEE (Hydroquinone bis(2-Hydroxy Ethyl Ether)

Explore our frequently asked questions

What differentiates HQEE as a diol chain extender?

HQEE functions as a high-performance, symmetrical aromatic diol chain extender for segmented polyurethanes. The rigid aromatic structure promotes hard segment packing and the symmetrical -OCH2CH2- segment in HQEE enable intermolecular hydrogen bonding with urethane linkages. These aggregate forces effectively facilitate hard segment packing, subsequently leading to well defined microphase separation morphologies in the polyurethane.
 
As a result, polyurethanes prepared from HQEE are more thermally resistant because of the effective packing of the hard segments and the positive effects of the aromatic moiety in the chain extender. By TGA (thermogravimetric analysis), the hard segment degradation peak for MDI/HQEE occurs around 350 °C, well above the degradation peak observed for MDI/BDO hard blocks under the same conditions. TPU’s based on MDI/HQEE display we defined melting points at around 125 °C. With the complete phase separated architecture, HQEE-based TPUs exhibited very high tensile strengths, excellent hardness, superior stability at elevated temperatures, increased tear strengths, abrasion resistance, high resiliency, and resistance to moisture.
 

What are the primary applications for HQEE/MDI based polyurethanes?

Applications for MDI/HQEE elastomers include high speed industrial wheels and tires, forklift tires; sport and amusement park wheels, pipe linings and coatings; seals and gaskets; conveyor belts, rollers and roll covers; oil well and hydraulic cylinder seal, oil field and mining equipment components and other high-performance end-uses.
 

What conditions are required to process HQEE in a polyurethane formulation?

Despite HQEE’s variety of applications and advantage over BDO, processors face challenges with this chain extender. There are two main difficulties associated with HQEE:
  • HQEE has a high melting point (>98 °C / 208 °F).
  • HQEE does not supercool but rapidly crystallizes below its melting point.  
 
To appropriately process HQEE, melting tanks and all process lines must be heated to ~110 °C and lines need to be insulated to prevent clogging. Furthermore, processors must preheat the prepolymer to around 100 °C before mixing it with HQEE. Otherwise, the HQEE will crystallize in the mix causing “starring” in the cured urethane elastomer. Molds will also require preheating to above 110 °C. An alternative to HQEE is 1,3-Bis (2-hydroxyethyl) resorcinol (HER). An aromatic diol chain extender for polyurethane prepolymers, HER manifests good compatibility with MDI-based prepolymers and is used in cast polyurethane and TPU applications. Compared to HQEE, HER has a lower melting temperature (89 °C vs. 98-102 °C) and the ability to supercool, which significantly improves the overall ease of handling and processing.  
 

What are Gantrade’s Sales Specifications for HQEE?

Gantrade’s sales specifications for HQEE are shown in the table below. The product form is flake. The minimum purity is 99%. 
 
Method Specification Typical Values
Appearance White to off-white
crystalline flake or pellets
Off-white flakes
Melting Point, °C 102 - 105 102 - 104
Moisture Content, % Max. 0.10 0.08
Color (1% Acetone), APHA Less than 50 Less than 10
Hydroxyl Value, mg. KOH/g 555 ± 1 555.2
Alkalinity, µeq/g Max. 0.7 NIL
Hydroquinone, % Max. 0.4 NIL
HQEE Purity, % Min. 99 99.79

 

What are the packaging options and storage requirements for HQEE?
HQEE is available in flake or pellet form. Packaging is 25 Kg. cartons within LDPE bags, 10 MT per FTL or 100 Kg. iron drums within LDPE bags, 8 MT per FTL. HQEE is hygroscopic and must be protected from atmospheric moisture. It is sensitive to light and should be kept in a dark space or container. The shelf life if stored is one year from the manufacturing date when stored properly in the original sealed container.
 
To explore how our range of urethane chemistries can address your unique applications, partner with Gantrade Corporation. Our expert teams, armed with a wealth of technical knowledge and experience, can guide you to the best solutions for your applications. Contact Gantrade today to get started.
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