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PLASTIC PAIL SELECTION AND USAGE

Return to Pail Selection and Usage Index

Guidelines for the Selection and Use of Plastic Pails:
Materials of Construction

Plastic Pails provide customers with the ability to customize package performance to meet specific product and distribution environment requirements.  Some of the ways plastic pails can be customized through material selection include: 

  • Impact Resistance (Low and High Temperature)
  • Compressive Strength (Low and High Temperature)
  • Chemical Compatibility
    • Environmental Stress Crack Resistance (ESCR)
    • Product Permeation
  • FDA Approved Materials
  • Ultra Violet Resistance
  • Printing Requirements
  • Colors/Pigments

By answering questions 1-4 and working with your pail manufacturer to answer questions 5-14, you can ensure your getting the best package for your product.  Testing with your product may be required to verify performance. 

 


  1. What are the properties of my product?
  2. What hazards will be encountered during the distribution of my product?
    • Temperature Extremes (During shipping, storage, filling, etc.)
    • Impact Severity and Frequency
    • Compressive Loads and Duration
  3. What is life of my product.  How long will it remain in the plastic pail?
  4. Is my product regulated  (DOT, FDA, Transport Canada, etc.) and/or subject specific performance requirements. Visit our performance section for information on determining if your material is regulated 

  1. What is the chemical resistance of the material of construction?  Is "my product" compatible with the material of construction?  Are there issues with the length of time my product will remain in the package?
  2. What is the general compressive strength, impact resistance and environmental stress crack resistance of the material of construction?  If I want greater compressive strength, impact resistance or environmental stress crack resistance how will the other properties be affected?
  3. What are the low temperature properties of the material of construction?  What happens to impact resistance at my anticipated minimum environmental temperature? 
  4. What are the high temperature properties of the material of construction?  What happens to the compressive strength and impact resistance at my anticipated maximum fill and environmental temperatures?
  5. What is the UV (ultra violet / sunlight) resistance of the base material of construction?  May I request more or less UV protection based on my needs?
  6. What colors are offered and do some colors outperform others (i.e. impact, UV).  How does "my color of choice" withstand sunlight exposure?  How "environmentally-friendly is "my color of choice"?  Is "my color of choice" offered in metal-free format and is their extra expense?
  7. What is the UV (ultra violet / sunlight) resistance of the base material of construction?  May I request more or less UV protection based on my needs?
  8. If my product is regulated by the US Department of Transportation  will the material of construction provide the required performance (Chemical Compatibility, low temperature Impact, high temperature compressive strength, etc.) Visit our performance section for information on determining if your material is regulated 
  9. If any, what are the food or medical limitations on the material of construction.  Has the material of construction been certified by FDA?
  10. Can I print on this material and if so is there any special pre-treatments required before printing?

Environmental Stress Crack Resistance (ESCR)
Although many molders treat ESCR and CPR as similar attributes, failure mechanisms of these attributes are quite different and further discussion is warranted.  ESC agents are thought to penetrate the amorphous regions of the polyethylene (between the spherulites or crystalline regions of the polymer), and result in crack initiation and propagation along inter-spherulitic boundaries.  Classic ESC failures show a brittle initiation point, with ductile tearing as the crack propagates.  Polyethylene resins most resistant to this form of attack will have lower density (higher co-monomer content thus higher tie molecule content) and lower melt index (higher molecular weight and thus higher tie molecule content).   CP agents attack polyethylene by penetrating the crystalline or spherulitic regions of the polymer.  Failure mode for this type of attack is typically loss in strength properties such as flexural modulus (related to dynamic top load) or tensile strength, which translates into a buckling or ductile tearing.  Polyethylene resins most resistant to this type of attack will have higher density (higher levels of crystallinity).
Selection of the optimum high-density polyethylene resin for a specific packaging application is accomplished through an in depth knowledge of pail performance attribute / resin property relationships.
 
HDPE RESIN SELECTION FOR OPTIMUM PAIL PERFORMANCE
 
Resin Selection Process
  • Confirm HDPE is the correct resin for the application
  • Determine end use market segment
  • Determine performance criteria
  • Select optimum resin Melt Index / Density balance to achieve performance criteria
  • Recognize that productivity (cycle time) is often in conflict with pail physical performance
Confirm HDPE is the Correct Resin
Consult with:
  • Pail content supplier
  • Chemical compatibility databases / chemical resistance charts
  • PE Resin suppliers
 
Determine End Use Market Segment
Typical Segments Include:
  • Lube Oils
  • Vegetable Oils
  • Latex Paints
  • Alkyd Paints
  • Janitorial Cleaners
  • Construction Materials
  • Liquid Foods
  • Dry Foods
Determine Performance Criteria
Typical Performance Attributes:
  • Stack Strength
  • Drop Resistance
  • Dynamic Topload Strength
  • Environmental Stress Crack Resistance ESCR.doc
  • Chemical Permeation Resistance ESCR.doc
Market segmentation by content type allows the opportunity for resin design to extract the maximum value in processing, while still achieving the necessary property balance.  Table 1 lists performance requirements for various pail market segments.
Table 1: Performance Requirements for Various Market Segments
Market Segment
Stack Strength
Drop Resistance
ESCR
CPR
Lube Oils High Medium Medium High
Vegetable Oils High Medium Low Medium
Latex Paints Very High Medium High High
Alkyd Paints Very, Very High High High Very, Very High
Janitorial Cleaners High Low Very High High
Construction Materials Very High High High Very High
Liquid Foods Medium Low Medium Low
Dry Foods Low Low Low Low Table 1: Performance

Figure 1 below outlines the basic relationships between various container performance criteria, and resin melt index and density.  For illustrative purposes, the range of densities typically used in container applications is shown as 0.950 to 0.964 g/cc, while melt index values range from 4 to 20 g/10 min.  Property tradeoffs are also highlighted below.

Maximum Productivity
  • Resin Melt Index é
  • Resin Density - Minor Effect
  • Property Tradeoff
    • Drop Strength
    • ESCR

 

Maximum Drop Resistance/Maximum ESCR

  • Resin Melt Index
  • Resin Density
  • Property Tradeoff
    • Productivity
    • Stack Strength Dynamic Top Load
Practical Ml/D for demanding applications (e.g.UN)
: 4-7 MI/0.950-0.954 D.
 

Maximum Stack Strength/Maximum CPR

  • Resin Density
  • Resin Melt Index
  • Property Tradeoff
    • Drop Resistance
    • ESCR

Dynamic Topload/Fill Temperature

  • Resin Density
  • Resin Melt Index - Minor Effect
  • Property Tradeoff
    • Drop Resistance
    • ESCR

 

Thorough knowledge of the performance attribute / resin property relationships discussed here will result in the correct resin choice required to achieve the desired container attributes and the ultimate goal of successful field performance.