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  Liner Specs


Manufacturing Quality Control (MQC) is a planned system of routine inspections that is used to directly monitor and control the quality of a material.

Manufacturing Quality Assurance (MQA) is independent of the MQC and includes inspections, verifications, audits, and evaluations of materials and workmanship necessary to determine and document the quality of a material.


2.1 Raw Material

Our quality control and quality assurance for HDPE and LLDPE geomembrane manufacturing starts with the testing of the raw materials. The resin manufacturers provide documentation confirming that the raw materials comply with our specifications.

Resin manufacturers report the following properties with each resin shipment:

This property is a measure of unit weight and is an indicator of the degree of crystallinity. It can be related to the material's chemical resistance, rigidity, permeability, tensile strength, and deformation characteristics.

Melt Index
This property is an indicator of the molecular weight and rheological properties of the polymer and can be related to the processability.

Carbon Black Content
(pre-compounded only)

The carbon black content is an important property to ensure protection against ultraviolet radiation. The raw materials may be pre-compounded with the carbon black. However, if resins are not pre-compounded, we will supplement them with the appropriate quantity of carbon black before manufacturing liner.

2.1.1   Geomembrane Material Railcar Acceptance

All resins, additives and concentrates used in Poly-Flex® geomembranes must have their physical integrity validated before they can be released into the production material stream. All incoming railcars are sampled by compartment; incoming materials not delivered by railcar are statistically sampled. Upon verification of the resin compliance with the specifications, the resin is pumped from the railcar into the silos dedicated to the production of the geomembrane.

  1. Resin samples are taken from each of the four payload compartments in an incoming railcar.
  2. Resin samples are sent to the laboratory. Using state of the art equipment, highly trained Quality Assurance personnel test the resin to ensure that it meets the specifications for producing Poly-Flex® geomembranes. The following tests are performed and compared against our specifications:

    Property Resins Additives & Concentrates
    Density (ASTM D 1505)  
    Melt Index (ASTM D 1238)  
    Carbon Black Content (ASTM D 1603)  
    Oxidative Induction Time (ASTM D 3895)

  3. After meeting production specifications, the resin is pumped from its railcar into a silo dedicated to that material.
  4. Off-spec material is returned to the vendor.

Applicable Test Methods

American Society for Testing and Materials (ASTM)

ASTM D 792   Specific gravity (relative density) and density of plastics by displacement
ASTM D 1004   Initial tear resistance of plastic sheeting
ASTM D 1238   Flow rates of thermoplastics by extrusion plastometers
ASTM D 1505   Density of plastics by the Density-Gradient technique
ASTM D 1603   Carbon black in olefin plastics
ASTM D 1898   Sampling of plastics
ASTM D 3895   Test method of oxidative induction time of polyolefins by thermal analysis
ASTM D 4437   Determining the integrity of field seams used in joining flexible polymeric sheet geomembranes
ASTM D 4833   Index Puncture Resistance of geotextiles, geomembranes and related products
ASTM D 5199   Test method for measuring nominal thickness of geotextiles and geomembrane
ASTM D 5323   Determination of 2% secant modulus for polyethylene geomembranes
ASTM D 5397   Procedure to perform a single point notched constant tensile load - Appendix (SP-NCTL) test
ASTM D 5596   Test method for microscopic evaluation of the dispersion of carbon black in polyolefin geosynthetics
ASTM D 5617   Multi-axial tension test for geosynthetics
ASTM D 5721   Practice for air-oven aging of polyolefin geomembranes
ASTM D 5885   Test method for oxidative induction time of polyolefin geosynthetics by high pressure differential scanning calorimetry
ASTM D 5994   Test method for measuring the core thickness of textured geomembranes
ASTM D 6692   Determining the integrity of nonreinforced geomembrane seams produced using thermo-fusion methods
ASTM D 6693  

Determining tensile properties of nonreinforced polyethylene and reinforced flexible polypropylene geomembranes

ASTM D 7238  

Test method for effect of exposure of unreinforced polyolefin geomembrane using fluorescent UV condensation apparatus

ASTM D 7466  

Test method for measuring the asperity height of textured geomembrane

Geosynthetic Research Institute (GRI) Standards

GM 10   Specification for the stress crack resistance of geomembrane sheet
GM 11   Accelerated weathering of geomembranes using a florescent UVA-condensation exposure device
GM 12   Measurement of the asperity height of textured geomembranes using a depth gauge

Addendum to Test Procedures

The following are modifications or clarifications to test procedures

  1. Specifications are based on the average of Machine Direction (MD) and Cross Direction (XMD) values.
  2. Specimens shall be taken uniformly across the width of the sheet as stated in ASTM D 1898.
3.1 Blown Sheet Process

Polyethylene resin is pumped directly from storage silos or from totes on the floor to hoppers above the extruder.

Hoppers feed resin into the extruder. The resin is heated to the melting point in the extruder barrel. It is conveyed through the barrel by the rotation of a specially designed screw which, in conjunction with heating elements along the barrel, provides consistency to produce a molten polymer stream.

The molten stream is forced through a screen pack, which act as a final filter for impurities or contaminants, and up through a die. It extrudes from the circular die as a film tube ("bubble"), pulled vertically by a set of nip rollers located at the top of a cooling tower. An IBC (Internal Bubble Cooling) unit, part of the extruder, maintains consistent bubble diameter. Material gauge is monitored and maintained by a computer system which controls the operation of the extruder.

At the top of the tower the bubble passes through a collapsing frame and is pulled through the nip rollers. The material is directed back toward the ground, and continues cooling as it approaches a winding machine. Before being taken up by the winder, the tube is split and spread to its deployable width. The winder rolls the finished geomembrane onto a specially made heavy-duty core.

3.2 Process Quality Control

Poly-Flex® geomembranes are manufactured via the blown sheet process. This is a continuous process. The key elements to successfully producing a high quality liner is to maintain consistency in both the raw material and the process. As described above raw material consistency is established in the laboratory when the resin is initially received. Consistency during the processing is assured by an on-line quality control monitor. This representative of the quality department has been specially trained to monitor the process and the liners during the manufacturing process.

The extrusion process starts with the verification of the formulation. This is done at the beginning of each order or blend change by the extrusion manager and then is continuously monitored by the on-line quality control representative.

The process conditions during manufacturing have been optimized for each resin formulation. These conditions are kept in a log book which is available to the line operator. These process conditions must be maintained throughout the production run. Any variation of process parameters from the set point range recorded on the process log book are immediately reported to the production supervisor by the on-line quality control representative. If the variation exceeds the control range, the quality control representative places the material being produced on hold. Materials are placed on hold until the process is brought under control.

The on-line quality monitor can also place material on hold if the material has any visual defect (holes, water spots, or scratches) or dimensional abnormalities (width, length, and thickness).

All materials placed on hold will be further inspected and tested. If the material passes specification and is approved by the quality control manager and/or production manager, the material will then be released into stock. If the material fails to pass specification or does not get approval of either the quality control or production manager then the material will be reclassified or scrapped. In either case it cannot be sold as a prime Poly-Flex® geomembrane.

Poly-Flex® geomembranes are continuously monitored for pinholes during the manufacturing process by spark testing equipment. The spark tester unit is a perpetual monitor of any holes that could surface in the sheet. The spark tester monitors the entire layflat width of the sheet as it is being manufactured. The detector operates from a 120 V AC power supply. The 120 volts are transformed to a higher voltage that ranges from 0-24 kilovolts. The electrode is made up of a long semiconductor blanket that is positioned to lay over the sheet as it passes over a steel roller prior to final winding. A grounding conductor is connected to the roller with a return line to the controller. If a hole passes under the electrically charged blanket, the voltage will arc to the steel roller and the detection system will sense the voltage drop, thus triggering an audible alarm and shutting down the winder. Twice per shift, the quality control technician tests the spark tester by introducing a 1/32" pinhole in the sheet. This hole is at the end of a roll after the scheduled footage has been achieved. The winder continues to run until the hole is detected. Once the hole is detected, the alarm sounds and the winder shuts down. The Q.C. technician restarts the winder and cuts out the entire layflat area of the pinhole.

After a roll of material has been produced it is labeled and a retain is cut for laboratory evaluation.

3.3 Roll Labeling

Three labels are affixed to each roll, as described below:

      1. One label on the outside of the core.

      2. One label on the core plug.

      3. One label on the roll surface.

      An additional label is attached to the laboratory sample.

3.4 Storage, Staging and Shipping of Geomembrane Rolls

Finished rolls (verified and labeled) are moved to the storage area using a specially designed cart and remain in storage until a Purchase Order is received. Rolls selected for shipment are moved to a staging area, where they are held for a truck. Before loading the order for shipment, all documentation is checked against the information on the roll labels. Rolls are lifted and moved using a loading arm equipped with rigging and hooks. Fork-lifting machinery are never to be used to lift or move geomembrane rolls.

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