ASTM D3596-19

Standard Practice for Determination of Gels (Fisheyes) In General-Purpose Poly(Vinyl Chloride) (PVC) Resins

SIGNIFICANCE AND USE
5.1 The gel (fisheye) in PVC resins is generally recognized as a hard particle of resin which will not fuse when the plastic mass is subjected to set conditions of hot processing. The number of unfused particles present is related to the conditions used. The presence of an excess of such particles is detrimental to many applications.
SCOPE
1.1 This practice provides a quantitative measure of the gels remaining in a flexible vinyl compound processed from general-purpose poly(vinyl chloride) (PVC) resins under a prescribed set of working conditions.  
1.2 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
Note 1: There is no known ISO equivalent to this standard.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Mar-2019
• ICS: 83.080.10 - Thermosetting materials
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.15 - Thermoplastic Materials

Relations

• Replaces: ASTM D3596-14 - Standard Practice for Determination of Gels (Fisheyes) In General-Purpose Poly(Vinyl Chloride) (PVC) Resins
• Effective Date: 01-Apr-2019
• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM D883-20 - Standard Terminology Relating to Plastics
• Effective Date: 01-Jan-2020
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2019
• Refers: ASTM D883-18a - Standard Terminology Relating to Plastics
• Effective Date: 01-Dec-2018
• Refers: ASTM D883-18 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2018
• Refers: ASTM D1600-18 - Standard Terminology for Abbreviated Terms Relating to Plastics (Withdrawn 2024)
• Effective Date: 01-Jan-2018
• Refers: ASTM D883-17 - Standard Terminology Relating to Plastics
• Effective Date: 15-Aug-2017
• Refers: ASTM D1600-14 - Standard Terminology for Abbreviated Terms Relating to Plastics
• Effective Date: 01-Feb-2014
• Refers: ASTM D1600-13 - Standard Terminology for Abbreviated Terms Relating to Plastics
• Effective Date: 15-Apr-2013
• Refers: ASTM D883-12e1 - Standard Terminology Relating to Plastics
• Effective Date: 15-Nov-2012
• Refers: ASTM D883-11 - Standard Terminology Relating to Plastics
• Effective Date: 15-May-2011

Overview

ASTM D3596-19: Standard Practice for Determination of Gels (Fisheyes) in General-Purpose Poly(Vinyl Chloride) (PVC) Resins provides a quantitative method to assess the presence of gels-also known as fisheyes-in flexible vinyl compounds produced from general-purpose PVC resins. Gels are hard, unfused resin particles that do not melt under the specified hot processing conditions. Excessive gels can negatively impact the physical and optical properties of the final PVC product, making their detection critical for quality control in a range of PVC applications. This standard is developed in accordance with internationally recognized standardization principles, although it currently has no ISO equivalent.

Key Topics

• Purpose: To determine and quantify the presence and size of gels (fisheyes) in flexible PVC compounds, supporting manufacturers in maintaining product consistency and quality.
• Test Procedure:
  • A sample of PVC resin is blended with standard additives and processed in a laboratory mixer.
  • The blend is milled, press-polished, and examined for gels using a viewing box and optionally a magnifying comparator.
  • Gels are counted and categorized by size for quality assessment.
• Classification: Gels are classified based on their diameter:
  • Size A: ≥ 0.5 mm
  • Size B: ≥ 0.4 mm
  • Size C: ≥ 0.3 mm and < 0.4 mm
• Reporting: The test requires detailed documentation, including gel counts by category, equipment specifications, sheet thickness, material amounts, and the method of measurement (visual or comparator).
• Units: SI units are the standard, with parentheses values provided as informational references.

Applications

• Quality Control: Manufacturers of PVC resins and flexible vinyl compounds use ASTM D3596-19 to monitor and minimize gel content, ensuring material processability and surface appearance.
• Product Development: R&D teams apply this standard to optimize resin formulations and processing conditions, resulting in products with fewer defects.
• Customer Specifications: Suppliers of PVC materials reference ASTM D3596-19 results to demonstrate gel quality to customers in applications like extrusion, calendaring, and molding.
• Regulatory Compliance and Reporting: Consistent gel measurement allows producers to comply with industry or customer-imposed limits, helping to prevent product failure or rejection.
• Troubleshooting Production Issues: The standard method helps identify sources of gels related to resin quality, blending uniformity, or equipment performance.

Related Standards

• ASTM D883 – Terminology Relating to Plastics
• ASTM D1600 – Terminology for Abbreviated Terms Relating to Plastics

As there is currently no ISO standard equivalent, ASTM D3596-19 serves as the primary international guideline for gel determination in general-purpose PVC resin.

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Keywords: ASTM D3596-19, gels in PVC, fisheyes, general-purpose poly(vinyl chloride), quality control, gel determination, PVC defects, plastic processing standards, flexible vinyl compounds, ASTM standards for plastics

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D3596 − 19
Standard Practice for
Determination of Gels (Fisheyes) In General-Purpose
Poly(Vinyl Chloride) (PVC) Resins
This standard is issued under the fixed designation D3596; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 4. Summary of Practice
4.1 A sample of PVC resin is mixed with calcium/zinc
1.1 This practice provides a quantitative measure of the gels
stabilizer, stearic acid, carbon black, and a plasticizer in a
remaining in a flexible vinyl compound processed from
laboratory mixer. The dry blend is milled on a two-roll
general-purpose poly(vinyl chloride) (PVC) resins under a
laboratory mill.
prescribed set of working conditions.
4.2 The milled sheet is press-polished and the gels counted
1.2 The values stated in SI units are to be regarded as the
using a bottom-lighted viewing box and a magnifying com-
standard. The values in parentheses are for information only.
parator.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
5. Significance and Use
responsibility of the user of this standard to establish appro-
5.1 The gel (fisheye) in PVC resins is generally recognized
priate safety, health, and environmental practices and deter-
as a hard particle of resin which will not fuse when the plastic
mine the applicability of regulatory limitations prior to use.
mass is subjected to set conditions of hot processing. The
NOTE 1—There is no known ISO equivalent to this standard.
number of unfused particles present is related to the conditions
used.The presence of an excess of such particles is detrimental
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard- to many applications.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- 6. Apparatus
mendations issued by the World Trade Organization Technical
6.1 Laboratory Mixer, with stainless steel mixing bowl.
Barriers to Trade (TBT) Committee.
6.2 Two-Roll Mill, 152.4 by 304.8 mm (6 by 12 in.),
263.5 mm (10.5 in.) between guides, differential speed ratio
2. Referenced Documents
1.40 6 0.04, fast roll speed 34 6 2 rpm, with an adjustable
2.1 ASTM Standards:
temperature range of 120–205 °C (250–400 °F).
D883 Terminology Relating to Plastics
NOTE 2—If the mill available does not meet these criteria, the
D1600 Terminology forAbbreviatedTerms Relating to Plas-
specifications of the mill used should be included in the report.
tics
6.3 Surface Pyrometer
3. Terminology
6.4 Balance, 0.1-g sensitivity.
3.1 General—Definitions are in accordance with Terminol- 6.5 Hydraulic Press having platens at least 203 by 203 mm
ogy D883 and abbreviations with Terminology D1600, unless
(8 by 8 in.), rated at a minimum of 140 MPa (20 000 psi) ram
otherwise indicated.
pressure on a 100-mm (4-in.) ram, which has the capacity for
heating to 163 6 3 °C (325 6 5 °F) on the pressing surfaces
and equipped with cooling water.
This practice is under the jurisdiction ofASTM Committee D20 on Plastics and
6.6 Timer, capable of being read in seconds.
is the direct responsibility of Subcommittee D20.15 on Thermoplastic Materials.
6.7 Cotton Gloves.
Current edition approved April 1, 2019. Published May 2019. Originally
approved in 1977. Last previous edition approved in 2014 as D3596 – 14. DOI:
6.8 Mill Knife.
10.1520/D3596-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6.9 Plates or Mold, two 203 by 203-mm (8 by 8-in.)
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
chrome-platedferroplates,orachrome-platedmoldwitha152
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. by 152 by 6.4-mm (6 by 6 by 0.25-in.) cavity.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3596 − 19
aclean-upbatchtodeterminethecorrectamount.Reporttheweightofdry
6.10 Backing Plates, two 203 by 203 by 6.4 mm (8 by 8 by
blend used.
0.250 in.).
8.3 Cut a 152 by 152-mm (6 by 6-in.) section from the
6.11 BrassShims, four, 0.51 by 13 by 203 mm (0.020 by 0.5
milled stock.
by 8.0 in.).
8.3.1 Placethesectioncutfromthemilledsheetbetweenthe
6.12 Magnifying Comparator (optional), equipped with a
two chrome-plated ferro plates, chrome side to the specimen,
transparent reticule (scale) showing circles from 0.03 to
then put the chrome ferro plates and the specimen between the
1.27 mm (0.001 to 0.050 in.) in diameter.
backingplatesandinsertinapressat163 63 °C(325 65 °F).
Preheat for 0.5 min with the press closed at zero pressure. A
6.13 Bottom-Lighted Viewing Box.
chrome-plated mold can be used instead of the plates.
7. Materials
8.3.2 After preheating, apply ram pressure for 2 min. Use
enoughpressuretoproduceasheetthicknessof0.5 60.03mm
7.1 PVC Resin
(0.020 6 0.001 in.). At the end of the 2 min, turn the heat off
7.2 Plasticizer
and the cooling water on. Allo
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D3596 − 14 D3596 − 19
Standard Practice for
Determination of Gels (Fisheyes) In General-Purpose
Poly(Vinyl Chloride) (PVC) Resins
This standard is issued under the fixed designation D3596; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This practice provides a quantitative measure of the gels remaining in a flexible vinyl compound processed from
general-purpose poly(vinyl chloride) (PVC) resins under a prescribed set of working conditions.
1.2 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only.
1.3 This standard does not purport to address all of the safety problems,concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and
determine the applicability of regulatory limitations prior to use.
NOTE 1—There is no known ISO equivalent to this standard.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
D1600 Terminology for Abbreviated Terms Relating to Plastics
3. Terminology
3.1 General—Definitions are in accordance with Terminology D883 and abbreviations with Terminology D1600, unless
otherwise indicated.
4. Summary of Practice
4.1 A sample of PVC resin is mixed with calcium/zinc stabilizer, stearic acid, carbon black, and a plasticizer in a laboratory
mixer. The dry blend is milled on a two-roll laboratory mill.
4.2 The milled sheet is press-polished and the gels counted using a bottom-lighted viewing box and a magnifying comparator.
5. Significance and Use
5.1 The gel (fisheye) in PVC resins is generally recognized as a hard particle of resin which will not fuse when the plastic mass
is subjected to set conditions of hot processing. The number of unfused particles present is related to the conditions used. The
presence of an excess of such particles is detrimental to many applications.
6. Apparatus
6.1 Laboratory Mixer, with stainless steel mixing bowl.
6.2 Two-Roll Mill,152.4 by 304.8 mm (6 by 12 in.), 263.5 mm (10.5 in.) between guides, differential speed ratio 1.40 6 0.04,
fast roll speed 34 6 2 rpm, with an adjustable temperature range of 120–205 °C (250–400 °F).
This practice is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.15 on Thermoplastic Materials.
Current edition approved Aug. 1, 2014April 1, 2019. Published September 2014May 2019. Originally approved in 1977. Last previous edition approved in 20132014 as
D3596 – 13.D3596 – 14. DOI: 10.1520/D3596-14.10.1520/D3596-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3596 − 19
NOTE 2—If the mill available does not meet these criteria, the specifications of the mill used should be included in the report.
6.3 Surface Pyrometer
6.4 Balance, 0.1-g sensitivity.
6.5 Hydraulic Press having platens at least 203 by 203 mm (8 by 8 in.), rated at a minimum of 140 MPa (20 000 psi) ram
pressure on a 100-mm (4-in.) ram, which has the capacity for heating to 163 6 3 °C (325 6 5 °F) on the pressing surfaces and
equipped with cooling water.
6.6 Timer, capable of being read in seconds.
6.7 Cotton Gloves.
6.8 Mill Knife.
6.9 Plates or Mold, two 203 by 203-mm (8 by 8-in.) chrome-plated ferro plates, or a chrome-plated mold with a 152 by 152
by 6.4-mm (6 by 6 by 0.25-in.) cavity.
6.10 Backing Plates, two 203 by 203 by 6.4 mm (8 by 8 by 0.250 in.).
6.11 Brass Shims, four, 0.51 by 13 by 203 mm (0.020 by 0.5 by 8.0 in.).
6.12 Magnifying Comparator (optional), equipped with a transparent reticule (scale) showing circles from 0.03 to 1.27 mm
(0.001 to 0.050 in.) in diameter.
6.13 Bottom-Lighted Viewing Box.
7. Materials
7.1 PVC Resin
7.2 Plasticizer
7.2.1 Plasticizer Type—The plasticizer selected shall represent the plasticizer type commonly used with the resin being tested.
Less solvating plasticizers will yield a higher gel count.
7.2.2 Plasticizer Level—The plasticizer usage level shall yield a test compound with approximately the same a similar shore
hardness as the compound that will be based on the resin being tested.being commercially produced.
7.3 Stearic Acid
7.4 Liquid Calcium/Zinc Stabilizer
7.5 Carbon Black
8. Procedure
8.1 Weigh 200200.0 g of the sample resin, 4.0 g liquid calcium/zinc stabilizer, 0.5 g stearic acid, 0.6 g carbon black, and
plasticizer into the stainless steel mixing bowl. Blend the ingredients in the laboratory mixer at 23.0 6 2.0 °C (73.0 6 3.6 °F) for
3 min.
NOTE 3—Other mixers capable of yielding a uniform dispersion can be employed.
8.2 Set the mill temperature so the dry blend fuses and bands on the front roll of the mill within 45–90 seconds and check to
dete
...