PVC Resin Model Codes: S1000, S1300, S700, SP660 Explained

A model code is the maker's label, not a grade. See how the number tracks polymerisation degree, the SG band it lands in, and what each class is for.

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A quote that arrives for "S1000" or "S700" is built on the supplier's internal model code, not on a grade the buyer can specify by that name. The code is the producer's own designation, printed on the bag and used inside the supplier's plant. Reading it takes two steps: recover the degree of polymerisation the number stands for, then place that number in the SG band the national standard defines. The grade a buyer orders against is the second step, never the first, and most confusion between a quote and a production line starts at the gap between the two.

1. The number is the degree of polymerisation

The numeric part of a model code is a rounded figure for the average degree of polymerisation. S1000 points at roughly 1000, S1300 at roughly 1300, S700 at roughly 700, and SP660 at roughly 660. The letters in front of the number are a series marker: S is the common suspension series, SP a special or specific series, SE a series some makers use for grades near a boundary. The letter marks the family. What the band table actually reads is the number behind it, since not every maker uses one letter for one series and the letter by itself cannot fix a grade.

The standard does not use the code. GB/T 5761-2018 sets each suspension grade from the measured viscosity number, and the viscosity number yields both the K value and the average degree of polymerisation. The model code is shorthand for the last of those three. A buyer who treats "S1000" and "SG-5" as the same word reads the shorthand as if it were the specification, and the shorthand was never written to be one.

The table is a guide, not a contract. The code states the producer's intent. The certificate of analysis records the measured result. The two usually agree on the class, then part company on the position inside it; that position is the part a production line actually feels.

2. Same number, different producer

The same numeric code does not map to the same grade across every producer, for two reasons. Some producers print a brand code as the model number. The brand family then carries its own numbering, which is why the same numeric value can appear under different letter prefixes. For three ethylene-route producers, the parallel codes denote the same class: Sinopec S-1000, Hengtong HT-1000 and Wanhua WH-1000 all sit in the SG-5 band. The numeric part still tracks the degree of polymerisation, a property of the molecular chain. A buyer who sees HT-1000 or WH-1000 should read it as the SG-5 class, the same as an S1000 from a producer that prints the polymerisation figure directly.

The second reason is the trailing letter. A code such as S1000R adds a producer's qualifier for a variant within the same polymerisation class, often a low-residual-VCM grade or a modified-process version. The letter changes the variant, not the SG band. A buyer who sees a trailing letter should ask the supplier what the letter denotes; the SG band does not move with it. The qualifier is commercial information the supplier controls, and the standard does not name it.

Some export markets quote the resin by K value directly, as "K67" or "K66". That is the same information in a different form: the K value is the conventional figure the viscosity number produces, and it lands in the same SG band. A buyer who receives a K designation should map it through the band table exactly as a model code, because the two describe one resin from two directions.

3. The four classes and what they are bought for

SG-5 is the workhorse for rigid building goods. Pipe, fittings, profiles and window frames run on it, and S1000 is the code most often seen against it. The chain length supplies the melt strength a pressure pipe needs at calibration, and a high-output line still processes it without a temperature penalty.

SG-3 sits at the high end of the chain length and is bought for flexible goods: cable insulation, artificial leather, film and shoe soles. Its longer chains take more plasticiser before the dry blend turns sticky, which is what those end uses require. S1300 is its common code.

SG-7 and SG-8 sit below SG-5 on the chain. Both are used where faster processing or rigid injection is wanted, in sheet, film and moulded fittings. SG-8 carries the shorter chain of the two, so it processes fastest and reads as the most rigid and most brittle; S800, S700 and SP660 are the codes that appear. The boundary between SG-7 and SG-8 is the smallest step in the range. That step is also the one most often confused on a quote. A buyer moving from SG-5 to SG-7 or SG-8 for a rigid part is moving down the chain, and the screw, temperature profile and stabiliser package move with it.

4. What a buyer can check before fixing the grade

Four checks settle most of the ambiguity, and none needs a laboratory.

The model code on the quote beside the SG band the supplier claims. A quote that names S1000 and SG-5 is internally consistent. A quote that names S700 and SG-5 is not. The mismatch is the first thing to raise.

The degree of polymerisation on the certificate of analysis against the number the code implies. The code points at a figure; the certificate shows the measured figure, and the two should sit in the same SG band.

Whether moving between two suppliers also means moving between two model codes, and therefore revalidating the line. Two suppliers both offering "SG-5" may mean two different model codes, two different points in the band, and a line tuned to one of them.

The K value window written into the contract, alongside the grade name. A contract that names SG-5 accepts the whole band. Adding a K window such as K 67 ± 0.5 narrows it to a single point, and the certificate must then show the measured value against that clause.

5. The code names a class, not a position

A model code names a class. It does not name the position inside the band. Two S1000 lots from two producers can sit at different points of the same SG-5 range, and the difference shows up on the line, not on the bag. The certificate of analysis is the only document that settles the point. (The full band structure across the four grades is set out on the grade guide.)