Methoxy Polyethylene Glycol 350 (MPEG-350) CAS 9004-74-4

Identity and physicochemical profile

Quality control for MPEG-350 grades

For synthesis grades, hydroxyl value, water and diol content help define reaction suitability. Diol impurities have two hydroxyl ends and can form unwanted diesters during esterification. We can provide the applicable quality-control information, including HPLC diol-content data for grades that require diol control. HPLC area percent is not a mass-percent purity. Viscosity is reported with its method, temperature and units; pH is reported with the aqueous concentration and test temperature.

Applications and grade selection

MPEG-350 is used as an intermediate for ester derivatives, including methacrylate building blocks for polycarboxylate superplasticizers and paint additives. It can also serve as a water-soluble solvent, carrier, humectant or lubricity component, depending on the formulation and specified grade.

For methacrylate synthesis by transesterification, MPEG-350 can be used with methyl methacrylate (MMA). 4-Methoxyphenol (MEHQ) is one polymerization-inhibitor option for this route; its suitability depends on the reaction system, the inhibitor already present in the monomer and subsequent polymerization requirements. This does not mean that neat MPEG-350 grades require added MEHQ.

• For synthesis, use the measured hydroxyl value (mg KOH/g) to calculate the amount of hydroxyl equivalents in the feed. Set the water and diol limits for the reaction, and assess conversion by a method appropriate to that reaction.
• Do not substitute PEG-400 directly: PEG is nominally difunctional, whereas MPEG has a methyl end cap and one terminal hydroxyl group.
• Compare viscosity, water, color and downstream reaction or formulation performance before approving a new source.

Storage and handling

MPEG-350 is hygroscopic. Keep containers tightly closed and limit humid-air exposure, especially where low water content is needed for synthesis. Storage, transfer and any inert-gas blanketing requirements for the offered grade are stated in the TDS and SDS.

Safety, documentation and procurement

Use the current SDS for PPE, spill control, transport and disposal. For a quotation, share the intended application, quantity and destination. If known, include the desired molecular-weight or hydroxyl-value range, water and diol limits, viscosity conditions, preferred packaging or a reference specification.

Compare PEG-300 and PEG-1500 when selecting polyethylene-glycol carriers with different molecular-weight and physical-form requirements. These PEG grades have two hydroxyl ends; MPEG-350 is methyl-capped at one end, so functionalization reactions require different stoichiometry and grade selection.