1,4-Butanediol (BDO) is a versatile liquid diol intermediate with reactive primary hydroxyl functionality and a linear structure that lends itself to formulating polyurethane elastomers with a superior balance of properties and cost.
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Gantrade’s standard grade of BDO is ideal for polyurethane applications, with a high purity (≥ 99.85%) and a very low moisture content.
1. BDO is a preferred chain extender for Polyurethane Elastomers.
When it comes to MDI or H12MDI systems, 1,4-BDO is the chain extender of choice for most processors. Functioning in this role, BDO reacts efficiently with MDI, H12MDI and other aliphatic isocyanates or prepolymers to create crystalline “hard segment” domains that efficiently microphase separate. Many studies have shown that the properties of a polyurethane are highly dependent on the extent and perfection of this hard-block phase separation. BDO as a urethane chain extender affords tough, high strength, durable, and thermally stable polyurethane elastomers.
In thermoplastic polyurethane (TPU) compositions, un-crosslinked BDO-MDI domains can be melted and will flow at elevated temperatures to allow thermoplastic processing. The associated networks reform when cooled to form tough elastomeric compositions.
Gantrade promotes the use of BDO as a urethane chain extender, especially for MDI systems and offers a low moisture-high purity grade for this application.
2. BDO has beneficial characteristics as a Chain Extender.
The first criterion for an effective diol urethane intermediate is linearity. The second criterion is that it ideally contains an even number of carbon atoms (number of CH2 groups in the repeating chain). Molecular level chain packing of the individual hard and soft segments of polyurethanes benefits the overall performance properties of the resulting elastomers.
As revealed in the table below, the high degree of crystallinity and melt enthalpy (heat required to melt the crystalline hard segment) in MDI-BDO hard segments are particularly noteworthy. Modeling has shown that the molecular chains align better, and inter-chain hydrogen bonding is facilitated with BDO as the chain extender.
Melt Enthalpy for MDI/Diol Segments in Polyester Polyol based PURs
| DIOL IN HARD SEGMENT | ΔH(J/G) – TM | TM °C |
| 1,2-EG | 0.9 | 175 |
| 1,3-PDO | 0.4 | 145 |
| 1,4-BDO | 2.8 | 148 |
| 1,5-PDO | 0.14 | 167 |
| 1,6-HDO | 0.69 | 156 |
Source: DuPont Tate & Lyle BioProducts Susterra White Paper at CPI 2020
3. Gantrade’s BDO has high purity and low moisture content.
Gantrade’s urethane grade BDO has a purity of ≥ 99.85% and moisture content of ≤ 150 ppm, making it particularly beneficial in polyurethane applications. With its low moisture content, our BDO permits processors good control of stoichiometry by avoiding the reaction of H2O with isocyanates and attendant release of CO2 gas bubbles.
| SPECIFICATIONS | 1,4-BUTANEDIOL |
| Assay, % | ≥ 99.85 |
| Water, Wt. % | ≤ 0.015 |
| Carbonyl, mgKOH/g | ≤ 0.100 |
| Color, APHA | ≤ 5 |
| Appearance | Clear & Free of Suspended Matter |
BDO has a high boiling point of 235°C (455°F) and a freeze point of 19-20°C (68°F). Since BDO will solidify at temperatures around 20°C, appropriate storage and handling temperatures are required in transferring BDO. The equivalent weight of BDO is 45.06 and the hydroxy number is 1245 mgKOH/g.
4. Gantrade’s BDO is available and easy to handle.
Gantrade stocks BDO in factory sealed 200-KG (441-LB) drums and 20 metric ton ISO tanks.
BDO is non-hazardous with a low order of toxicity. It is easily handled in standard polyurethane processes. The shelf-life of BDO is two years under the proper storage and handling conditions. An associated SDS can be obtained through Gantrade Corporation.
BDO is a regulated product. It is only intended for use in industrial applications and is not intended for human consumption.As a part of the Gantrade Corporation Product Stewardship process, certain standard customer information and control measures for BDO need to be documented prior to sale and distribution of 1,4-butanediol. Gantrade can guide our customers through this process.
5. Because of its many attributes, BDO is used in a wide range of applications.
1,4-Butanediol is used extensively as a chain extender in the manufacture of polyurethanes. In MDI systems, BDO provides:
- High, consistent reactivity and shorter demold times with MDI, H12MDI and prepolymers
- Hard-block domains that efficiently microphase separate affording tough networks
- Polyurethanes with a good balance of hardness and low temperature flexibility
- Polyurethanes exhibiting high strength, durability, and thermal stability
- TPUs with good melt stability and excellent processing characteristics
- Good compatibility with other system components
