Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D1755-21 – Standard Test Method Technical Guide
📐 Scope and Classification of PVC Resins
This specification, designated D1755-21, establishes comprehensive requirements for homopolymers of vinyl chloride in their original powder form. These resins are intended for subsequent mixing and processing into thermoplastic compositions. The standard explicitly defines a nominal specific gravity of 1.4 and a theoretical chlorine content of 56.8 %. All values stated in the specification are in SI units.
Two principal types of resin are recognized: Type GP (General Purpose) covering suspension and mass resins, and Type D (Dispersion) resins primarily intended for use in organosols and plastisols. A critical processing distinction is that when mixed with plasticizer, Type GP resins yield a dry or moist powder, whereas Type D resins yield a liquid slurry. The standard references Terminology D883 and D1600 for applicable definitions and abbreviations.
💡 Processing Insight: The choice between Type GP and Type D fundamentally dictates the manufacturing route. GP resins are typically used in dry blending, extrusion, and injection molding. Type D dispersion resins are indispensable for high-quality coatings, rotational casting, and dip molding where a fluid paste is required.
⚙️ Test Methods and Property Classification
The classification system provides for a wide choice of grades based on the possible combinations of requirements in the specification tables. A grade is designated by the resin type (GP or D), followed by cell numbers for each property in the order they are listed.
Table 1 — General Purpose Resin (Type GP) Requirements
| 🟦 Property | 📏 Test Method | 📐 Cell 1 | 🎯 Cell 2 |
|---|---|---|---|
| Dilute Solution Viscosity | D1243 | < 0.70 dL/g | 0.70 – 1.20 dL/g |
| Apparent Density | D1895 | < 0.45 g/mL | 0.45 – 0.60 g/mL |
| Plasticizer Sorption | D3367 | < 30 g/100g | ≥ 30 g/100g |
| Volatile Matter (incl. Water) | D3030 | < 0.50 % | |
Table 2 — Dispersion Resin (Type D) Requirements
| ⚡ Property | 🎯 Test Method | 📐 Cell 1 | 🔢 Cell 2 |
|---|---|---|---|
| Volatile Matter (incl. Water) | D3030 | < 0.4 % | 0.4 – 0.8 % |
| Particle Size (% through 200 mesh) | D1921 | < 95 % | ≥ 95 % |
| Apparent Viscosity (Low Shear) | D1824 | < 50 Poise | 50 – 100 Poise |
⚠️ Standard Conformance: Per Note 1 of D1755-21, this ASTM standard and ISO 1264-1980 address the same subject matter but differ in technical content. Users must verify the specific requirements applicable to their jurisdiction or contractual agreements.
📊 Key Measured Properties and Applications
Beyond general classification, the standard specifies rigorous test methods for practical processing properties. D2396 evaluates powder-mix time using a torque rheometer. D3892 provides a standard practice for packaging and packing. For electrical applications, D495 and D2132 assess arc resistance and tracking. The D3030 test method is critical for measuring volatile matter (including water), which directly impacts processing stability and final product quality. High shear viscosity of plastisols is evaluated via D1823.
The standard places safety and environmental responsibility squarely on the user, requiring them to determine the applicability of regulatory limitations before use.
❓ Frequently Asked Questions
🔍 What is the nominal specific gravity of PVC resins under D1755-21?
The standard specifies a nominal specific gravity of 1.4 and a theoretical chlorine content of 56.8 % for the homopolymers covered by this specification.
💡 How are Type GP and Type D resins defined and differentiated?
Type GP (General Purpose) encompasses suspension or mass resins that form a dry or moist powder when mixed with plasticizers. Type D (Dispersion) resins are designed specifically to create a liquid slurry for use in organosols and plastisols.
⚡ Which test methods are used for viscosity under this standard?
The standard references D1243 for Dilute Solution Viscosity of the resin, D1823 for Apparent Viscosity of Plastisols at High Shear Rates, and D1824 for Apparent Viscosity at Low Shear Rates.
📌 How is a resin grade designated in this specification?
A grade is designated by the resin type (GP or D), followed by a series of cell numbers corresponding to the specific property limits defined in Table 1 and Table 2 of the standard.