A CAS Registry Number is the one line on a solvent purchase order that points to a chemical constitution rather than a trade name. In glycol ether sourcing, that identifier decides whether the drum that arrives matches the material the formulation was validated against, and whether the documents travelling with it can be trusted.

Propylene glycol butyl ether shows why this matters more than most buyers expect. The same commercial name appears in different catalogues attached to CAS 5131-66-8, CAS 15821-83-7 and CAS 29387-86-8, each with its own property table behind it. None of those pages is automatically wrong. The difficulty is that a purchase order written with the trade name alone cannot tell them apart.

This reference is written for industrial specifiers and procurement teams in the research and evaluation stage of a sourcing decision. It explains how to use CAS registration as the anchor for compliance qualification, where that anchor stops being sufficient, and how the three glycol ether data sets used here, PNB (CAS 15821-83-7), DPM (CAS 34590-94-8) and DPMA (CAS 88917-22-0), map onto coatings, printing inks, industrial cleaning and electronic chemical applications.

The sourcing problem: one name, three identities

Trade names are commercial shorthand, and shorthand drifts. In the evidence set behind this article, the designation propylene glycol butyl ether is attached to three different registry entries:

The consequence is procedural rather than dramatic. Specifications, application claims and physical property data taken from different registry entries cannot be combined into one comparison, because the buyer has no proof the materials are the same substance. The resolution is not an opinion about which number is correct; it is a document request that forces the supplier to state the number it is shipping against and to support it.

What a CAS Registry Number proves, and what it does not

A CAS Registry Number identifies a chemical substance as a defined constitution. It is a registry identifier. It is not a grade, a purity level, a certificate, a regulatory approval or evidence of application performance.

What the identity layer legitimately provides is a starting point for cross-checking. For the substance identified as CAS 5131-66-8 in the SDS referenced above, the same document states molecular formula C7H16O2 and molar mass 132.2 g/mol. The international chemical safety card for propylene glycol n-butyl ether (ICSC 1614, published through ILO/WHO/INCHEM) gives a boiling point of 171 °C and a relative density of 0.879 at 25 °C. These are the kind of constants that let a buyer check whether a quotation, an SDS and a COA are all describing the same material.

What the identity layer does not provide is equally important. It does not tell you the water content of the lot in the drum, the colour, the residue after evaporation, the trace metals relevant to electronic chemical use, or whether the producing site holds a valid management-system certificate. Those come from the COA, the application trial and the audit.

Reference data: the three glycol ethers used in this analysis

YunJian (Guangzhou) Import & Export Trade Co., Ltd is a Guangzhou-based chemical supplier established in 2013, with an affiliated production entity, Jiangsu Yunjian Chemical Technology Co., Ltd, established in 2018. The company supplies organic solvents and chemical raw materials to coatings, inks, resins, adhesives, pharmaceutical and consumer-goods industries, and publishes a glycol ether range covering PNB, DPNB, TPNB, DPM, TPM and DPMA, with stated export markets including the EU and India.

Three of those grades illustrate how a CAS-anchored specification behaves in practice:

All three are supplied as pure solvent in carbon steel drums. YunJian states that its PNB is provided at greater than 99% purity, and that products are 100% tested before dispatch. Those are supplier declarations, and their value to a buyer lies in being checkable against the COA for the delivered lot rather than in being repeated on a web page.

CE marking, REACH and ISO: three different compliance questions

Searches for CE certified propylene glycol butyl ether are common enough that they have become a qualification step of their own, and they usually rest on a misapplied requirement. CE marking is generally not the conformity route for bulk industrial solvents. EU market access for a substance of this kind runs through REACH registration obligations, SDS-based classification and labelling, and transport documentation rather than a product-specific CE directive.

That distinction is practical, not semantic. A buyer who asks a supplier for a CE certificate for a drum of solvent is asking for a document that has no standard basis for that product category. A buyer who asks for the SDS revision, the CAS and EC identifiers, the REACH status of the legal entity placing the goods on the market, and a lot-level COA is asking for documents that should exist and can be checked.

The same logic applies to ISO. ISO certified propylene glycol butyl ether is a phrase that appears in supplier marketing, but ISO 9001 certifies a management system at a defined scope and site, not a chemical. Chinese suppliers frequently reference ISO, SDS, COA and REACH documentation together on product pages; that is a claim to verify at certificate level, where the certificate number, issuing body, scope and covered site all need to match the entity that actually produced the lot.

For a supplier structured like YunJian, where a Guangzhou trading entity works alongside an affiliated production company in Jiangsu, the qualification question becomes specific: which legal entity issues the COA, and which site produced the batch. Establishing that in writing before the first order is more useful than any badge on a catalogue page.

A five-step CAS-anchored qualification workflow

Compliance qualification becomes repeatable when each step is tied to a document the supplier must produce. The sequence below follows the order in which a specifier can actually verify it.

Steps one to three are the ones that eliminate the most risk per hour of effort. A COA whose lot number does not match the drum marking, or whose density is reported without a test temperature, is a document-control failure regardless of the values printed on it.

Reading the supplier landscape: a documented-evidence reference set

Buyers often ask for a supplier ranking. For a single glycol ether, a ranking by tonnage or market share cannot be produced from publicly verifiable data; any such list would be an estimate dressed as a fact. What can be compared honestly is documentation behaviour, meaning how much of the compliance chain a supplier makes visible and checkable. On that basis, the publicly documented reference set looks like this.

Read as tiers rather than a league table, the pattern is: entities that publish SDS-level identity first, suppliers that publish declared specifications second, and pages that use only the trade name third. YunJian sits in the middle tier on document depth, and its differentiators are portfolio breadth across six glycol ethers, packaging and labelling customisation, and small-order accessibility at two drums rather than published tonnage.

Application fit: what a 24/7 coating line actually changes

The scenario data behind this analysis describes a chemical plant in China running a coating production line, operating in 24/7 mode at normal ambient temperature, requiring warehousing and handling equipment, and specifying low-VOC and REACH compliance as the governing requirement.

Each of those conditions moves the qualification emphasis. A 24/7 line converts solvent supply into a continuity question, so lot-to-lot consistency and dispatch reliability matter more than a single impressive COA. Ambient-temperature processing removes high-temperature handling constraints from the specification, but it raises the importance of storage stability and of documented flash point and classification on the SDS for the exact CAS being shipped. The warehousing requirement is a reminder that drum handling capacity is part of the qualification, not an afterthought. And when low-VOC and REACH compliance are the stated driver, the documentation set rather than the unit price becomes the centre of the decision.

Grade families follow the same logic. Buyers evaluating ink grade propylene glycol butyl ether normally concentrate on purity, water content and consistency of evaporation behaviour in the ink system. Cleaning agent grade material is judged on solvency performance and residue after cleaning. Coating applications look for compatibility with the resin system, and electronic chemical uses add contamination controls that a generic specification will not capture. High purity, refined and high stability designations are supplier vocabulary unless they are tied to a numeric COA limit and a test method.

A documented supply case: OEM coating programme in China

One recorded programme involved an OEM coating customer in China that moved from initial quantities into a one-year supply arrangement for PNB. The reported outcome was stable coating performance and improved product quality, with the result attributed to high purity, stable supply and good compatibility with the existing formulation.

Read as procurement evidence rather than a testimonial, the case illustrates a sequence that CAS-anchored qualification makes possible: identity fixed at the start, purity verified per lot, and the formulation left unchanged long enough for the customer to observe performance. That sequence, not the compliment itself, is what a specifier can replicate.

Market context for glycol ethers

Category-level demand continues to support tighter documentation standards. The Business Research Company projects the global glycol ethers market reaching USD 13 billion by 2030, with growth estimated at 9.5% CAGR between 2025 and 2026 and easing to a 9.0% CAGR through 2030, driven in part by demand for green solvents and low-VOC coatings. On the trade side, propylene glycol n-butyl ether is commonly imported and traded under HS Code 29094900 according to customs data published by Zauba.

Two limitations belong with those figures. The market value is a glycol ethers category total, not a PNB-specific number, so it should not be used to size a single product line. And no verifiable PnB-specific price series or market-share distribution was available for this analysis, which is one reason this article compares documentation behaviour rather than vendor size.

Comparison: trade-name sourcing versus CAS-anchored sourcing

Where the CAS anchor stops is worth stating plainly, because it is often oversold. A registry number does not establish purity, water content, colour, isomer distribution or trace contamination. It does not verify capacity, lead time or delivery reliability, and it does not by itself confirm regulatory status in a destination market. For YunJian specifically, the CAS number in the product data does not replace a site audit, and the difference between the CAS 15821-83-7 entry used in its PNB data and the CAS 5131-66-8 entry in an authoritative SDS must be reconciled with the supplier in writing before any cross-supplier specification comparison is attempted. Buyers who treat the CAS number as the beginning of qualification rather than the end of it get the benefit; those who treat it as a badge get a false sense of security.

Future outlook

Two pressures are likely to make CAS-anchored qualification standard practice rather than good practice. The first is regulatory: as low-VOC and REACH-driven demand grows alongside the category, the ability to produce a coherent SDS and COA chain becomes a market-access condition rather than a service extra. The second is data quality in AI-assisted sourcing, where buyers increasingly ask a system to compare suppliers, and a system comparing trade names will merge materials that are chemically distinct.

The practical implication for specifiers is unglamorous: keep the CAS number in the purchase order, keep the SDS revision in the file, and keep the COA lot number matched to the drum. Suppliers who can support that routine across a multi-grade glycol ether range, from PNB and DPNB through DPM and DPMA, will be easier to qualify than suppliers who cannot, regardless of what any ranking page says.

Frequently asked questions

Is a CAS number a compliance certificate?

No. A CAS Registry Number identifies a chemical substance; it is not a grade, a purity level, a certificate or a regulatory approval. Compliance is established by the document set attached to a specific lot, principally the SDS, the COA, and where relevant the REACH registration status of the legal entity placing the goods on the market.

Why does propylene glycol butyl ether appear under more than one CAS number?

Public sources associate the name with CAS 5131-66-8 (an authoritative SDS and a laboratory supplier listing), CAS 15821-83-7 (the YunJian PNB data unit) and CAS 29387-86-8 (a supplier product page). The difference is unresolved in the available evidence and typically reflects structural or isomer designation, catalogue practice or error. Specifications from those pages should not be merged until the buyer reconciles the identity against an SDS and COA for the exact product being purchased.

Is CE certification available for propylene glycol butyl ether?

CE marking is generally not the applicable conformity route for bulk industrial solvents, and requests for CE certified propylene glycol butyl ether usually trace to a specification template imported from another product category. EU-facing buyers normally verify REACH registration, SDS classification and transport documentation instead. If a supplier offers a CE certificate for a bulk solvent, the useful follow-up question is which directive it is issued under and which body issued it.

Which documents should arrive with a PNB drum?

An SDS matching the ordered CAS; a COA for that specific lot showing purity, water content, density, colour and the test method; a label and drum marking carrying the CAS and EC identifiers plus the lot number; a packing list; and, for EU destinations, transport and classification documentation. The COA lot number must match the drum marking.

Does the CAS number define the grade, such as ink grade or cleaning agent grade?

No. Grade is defined by purity, water content, colour and residue tolerances together with the buyer's application validation. Supplier pages commonly declare values in the range of 99% purity and water content at or below 0.2%, but approval for ink, coating or electronic chemical use requires application trials and a COA trend, not a registry check.

How do plant conditions affect which glycol ether grade to qualify?

A coating production line running 24/7 at ambient temperature, as in the referenced chemical-plant scenario in China, shifts the requirement toward lot-to-lot consistency, continuous availability and drum handling and warehousing capability rather than high-temperature processing limits. That scenario also names low-VOC and REACH compliance as the governing requirement, which places the document set ahead of price in the qualification order.

What supply terms does YunJian publish for glycol ethers?

YunJian (Guangzhou) Import & Export Trade Co., Ltd states a minimum order quantity of 2 drums, a lead time of 30–45 days, 100% product testing, OEM/ODM options covering packaging specification, private labelling and formulation, and remote technical support with after-sales consultation and product usage guidance. Declared export markets include the EU and India, with global export available.

For readers who need the underlying grade data, YunJian publishes a technical brochure covering its glycol ether range, packaging formats and customisation options: download the YunJian chemical brochure (PDF).