top of page
  • Writer's picturePipe Dream Team

Molecular Compatibility - Molecular Matching Importance In Polywelding

Molecular compatibility - Incompatibility in molecular compounds being welded or attempted to be joined can create unstable welds and lead to potential risk or harm. It is important to understand what compounds are compatible in the field to ensure the durability and safety of a finished product long term. While certain plastics seamlessly meld during the process, others exhibit incompatibility due to differences in molecular structures. This article explores the intricacies of molecular compatibility, shedding light on which structures harmonise and why; and why others do not.


The Foundation of Molecular Compatibility

Molecular compatibility hinges on the structural similarities between plastics. In successful polywelding, plastics with akin molecular structures can form strong and durable bonds. Conversely, attempting to polyweld plastics with disparate/differing molecular structures often results in weak joints that compromise the overall integrity of the weld.

Plastics with Compatible Molecular Structures

Polyethylene (PE):

PE is a thermoplastic with a simple linear structure, consisting of repeating ethylene units. Its compatibility with similar molecular structures makes it an excellent candidate for polywelding.

Polypropylene (PP):

PP, characterized by a propylene repeat unit, shares molecular similarities with polyethylene, contributing to its compatibility for successful polywelding.

Polyvinyl Chloride (PVC):

PVC, featuring a vinyl chloride monomer, aligns well with other vinyl-based molecular structures, enabling robust polywelding joints.

Plastics with Incompatible Molecular Structures

Polyethylene vs. Polyvinyl Chloride:

Attempting to weld polyethylene and polyvinyl chloride together poses challenges due to their distinct molecular compositions. PE's linear structure contrasts sharply with PVC's vinyl-based structure, weakening bonds.

Thermosetting Plastics:

Thermosetting plastics, such as epoxy and phenolic resins, adopt intricate three-dimensional structures during their curing process. These irreversible structures hinder molecular mobility, rendering them unsuitable for polywelding.

What causes Molecular Incompatibility?

Chemical Dissimilarity:

Plastics with dissimilar molecular compositions lack the chemical affinity necessary for molecular integration, in essence, an inability to seamlessly bond. This divergence impedes the formation of a cohesive and resilient joint during polywelding, creating a weak and unstable joint.

Molecular Weight Disparity:

Molecular weight variations between plastics can result in uneven melting and fusion during polywelding, leading to weak joints.

Ensuring Compatible Materials are Used

Material Data Sheets:

Refer to material data sheets provided by manufacturers to understand the molecular composition and recommended applications of each plastic type.

Industry Guidelines:

Adhere to industry guidelines that specify compatible plastics for polywelding applications. These guidelines often consider molecular structures and chemical compatibility.

In summary, the success of polywelding hinges on the molecular compatibility of plastics. Plastics with similar structures, such as polyethylene, polypropylene, and polyvinyl chloride, lend themselves well to polywelding. Conversely, plastics with disparate structures or thermosetting properties may not be compatible, emphasizing the importance of understanding molecular composition for successful polywelding outcomes in industrial projects.

3 views0 comments


bottom of page