PVC Resin SG-7 (K 60-62): Specification and Applications

SG-7 is where PVC starts flowing properly. The molecular weight is low enough that the melt fills a thin section and releases from a hot calender roll cleanly, and the apparent density is high enough that you get useful output per screw turn. If you make rigid sheet, calendered film, bottles or thin-wall injection parts, this is the grade worth testing.

We ship SG-7 as a first-tier distributor out of Shandong, China. We do not polymerise it. The batch certificate is issued by the producing plant, and we obtain it for you.

Quick answer: SG-7 is defined by GB/T 5761-2018 as a viscosity number band of 87–95 mL/g, which is the same thing as a K value of 60–62 and an average degree of polymerisation of 741–845. Its characteristic figures are a higher apparent density requirement, at least 0.50 g/mL, and a low plasticiser absorption requirement of at least 12 g per 100 g. It is bought for rigid sheet, bottles and containers, calendered film and high-flow injection moulding.

1. What SG-7 actually is

SG-7 sits below SG-5 on the molecular weight ladder. The band, in three expressions:

• Viscosity number: the standard defines SG-7 as 87–95 mL/g.
• K value: 60–62. Buyers outside China usually write K61 or K60.
• Average degree of polymerisation: 741–845.

Two consequences follow from the lower molecular weight, and both are the reason people buy this grade in place of SG-5.

It flows. Melt viscosity is lower, so the material fills thin and intricate sections (a bottle wall, a thin calendered film, a complex injection part) at lower melt temperature and lower injection pressure. On a calender, lower viscosity also means cleaner release from the roll and a better surface, which is why transparent and glossy rigid film is usually not made on a high-K grade.

It packs. SG-7 carries a higher apparent density requirement (at least 0.50 g/mL, against at least 0.48 for SG-5) and a finer particle size distribution. In practice that means more kilograms per screw turn and better feeding stability, which shows up as output before it shows up on any certificate.

The cost is toughness. Lower molecular weight means lower impact strength and lower resistance to creep under load. Rigid sheet made on SG-7 alone will crack before a sheet made on SG-5 will. This is not a defect of the grade. It is why rigid formulations on SG-7 normally carry an impact modifier and a processing aid, and why the formulation work matters more on this grade than on SG-5. The plasticiser absorption requirement, at least 12 g per 100 g, reflects the same thing from the other side: this is a rigid-product grade and it is not built to take a heavy plasticiser load.

2. Specification

Values below are the requirement figures for the SG-7 band under GB/T 5761-2018.

Three notes on reading this table.

Note the two limits that are looser than on SG-5. Impurity particles go from ≤ 16 to ≤ 20 per 100 g, fish eyes from ≤ 20 to ≤ 30 per 400 cm², and whiteness from ≥ 75 % to the same ≥ 75 %. For a pigmented or filled rigid product this is not a problem. For a transparent sheet or a clear bottle, fish eyes and impurity particles are exactly the defects your customer will see, so if clarity is the requirement, write tighter acceptance figures into the order line.

These are the SG-7 band requirements. A conforming batch has to sit inside them, and the lot's own measured values are on its own certificate. Your incoming inspection should compare against your own acceptance range.

Batch COA comes from the producing plant. Tell us at enquiry stage and we will obtain the certificate for the lot we are offering and send it before you commit. We do not issue certificates ourselves.

Standards note: GB/T 5761-2018 remains in force. The official record shows it was reviewed on 1 July 2025 with a conclusion of continuing validity. GB/T 3402.1-2026 and GB/T 3402.2-2026, which govern designation and test methods, take effect on 1 February 2027 in place of the 2005 and 2010 editions. What a buyer should now check is written up here.

3. Where SG-7 goes, and how it is processed

The formulation point again, because it decides whether SG-7 works for you: on this grade you are buying flow, and you are buying it against impact strength. Budget for the impact modifier and the processing aid in your costing before you switch a line over, or the sheet you produce will be beautiful and brittle.

4. Naming it correctly on a purchase order

If you are producing clear or glossy material, the order line needs one field a pigmented-product buyer does not: a tight fish eye and impurity particle limit. The standard limit is not a clarity specification.

5. Packaging, marking and documents

How to read the markings on a PVC resin bag covers batch number, grade marking and the fields your incoming sheet should record.

6. What to send us for a firm offer

1. Grade and position in the band: SG-7, plus a viscosity number or K value target.
2. End product and process: sheet, film, bottle or injection part; calendering, extrusion, blow moulding or injection.
3. Clarity requirement: pigmented, translucent or optically clear. This decides which limits go on the order line.
4. Formulation context: whether you run an impact modifier and processing aid, and what you are switching from.
5. Quantity: first order and expected monthly volume. FCL and LCL are both workable.
6. Packaging: 25 kg bags, jumbo bags, palletised, or private label.
7. Discharge port: name it and we will quote FOB, CFR or CIF against it.
8. Documents you need: Certificate of Origin, Form E, third-party inspection at loading.
9. Payment terms: so we can show you the total cost of the order.

7. Frequently asked

SG-7 or SG-8 for rigid sheet? Both are low-viscosity grades and both are used in rigid sheet. SG-7 sits at K 60–62, SG-8 at K 55–59. SG-8 flows further and is the usual choice for foam board and thin transparent sheet; SG-7 holds a little more toughness, which matters on thicker sections. Tell us the sheet thickness and the process and we will tell you which one we would ship.

Why is the fish eye limit looser than on SG-5? Because the standard treats SG-7 and SG-8 as grades aimed at pigmented and filled rigid products, where a fish eye does not show. If you are making clear material, the standard limit is not the number you should be accepting. Set your own and put it in the contract.

Can I get the COA before I place the order? Yes. Tell us the quantity you are considering and we will obtain the certificate for the lot we are offering from the producing plant and send it for review. If the apparent density or viscosity number does not sit inside your acceptance range, you have spent nothing.

Do you supply in jumbo bags, or with our own bag design? Both are possible. 800 kg jumbo bags and palletised loading on request; private-label bag printing for volume orders.

What does the price depend on? The feedstock route the lot came from, volume and packaging, delivery basis, payment terms, and timing. PVC quotes hold for a shorter window than most plastics.