Two compounds meeting the same Shore A hardness specification can require different processing conditions and retain different properties during service. An existing Innovative PVC grade can serve as the reference compound in a substitution trial. The technical comparison needs to establish how changes to PVC additives affect thermal stability and plasticiser retention. Approval requires evidence that the replacement compound meets the processing requirements and performance specifications relevant to the finished product.
A replacement compound that meets your Shore A target still needs qualification against the processing conditions and failure modes of your product. At Innovative PVC, we manufacture flexible compounds for extrusion and injection moulding, where similar hardness specifications may apply to products with different performance requirements. Changes to PVC additives should be assessed through production trials and testing of the finished component.
PVC Additives and Thermal Exposure During Interruptions
Material held inside a hot barrel during a stoppage experiences a different thermal history from material moving through uninterrupted production. A successful continuous run therefore does not establish tolerance of extended residence time.
PVC stabilisers limit degradation during processing, but their protective capacity depends on the formulation and thermal exposure. Comparing the existing and replacement grades requires a defined heat-stability assessment alongside the production trial. Colour change after controlled exposure provides one indicator, while testing retained mechanical properties helps determine whether the material continues to meet its specification.
Lubrication also influences fusion and flow. Changes to these PVC compound additives require checks on melt temperature and processing pressure, even if barrel settings remain unchanged. Identical machine settings do not establish identical conditions within the compound.
Plasticiser Substitution and Retained Flexibility
Replacing PVC plasticisers changes the chemistry governing flexibility and plasticiser retention. Adjusting dosage to restore the original hardness does not establish equivalent behaviour at low temperatures or in contact with substances that extract plasticiser.
Plasticiser loss reduces flexibility and increases hardness. A substitution therefore needs testing against the actual exposure: migration into adjacent materials differs from extraction by oils or cleaning fluids. The relevant acceptance criterion is the property retained after exposure, rather than the initial hardness alone.
For flexible PVC compounds, a replacement trial should compare:
- Hardness after conditioning and after the specified exposure.
- Low-temperature flexibility at the required service temperature.
- Mass change after extraction testing, where relevant to the intended application.
In rigid PVC grades, changes to impact modifiers similarly require impact testing at the specified temperature, as hardness alone does not establish resistance to brittle fracture.
Gasket Approval Under Comparable Compression Conditions
Two gasket grades meeting the same hardness target need compression-set results under comparable conditions. Compression set measures residual deformation after release; test temperature and duration affect the result, as do the recovery conditions.
ISO 815-1 outlines compression-set testing methods for vulcanised and thermoplastic rubbers, demonstrating the importance of consistent test conditions. For PVC seals, the selected test method must be appropriate for the material and the customer’s specifications.
Material testing then needs verification in your actual profile. Wall thickness and installed compression affect sealing contact, so material recovery alone does not establish sealing performance. Assessing the replacement PVC formulation against material test results and finished-profile performance provides a clearer technical basis for approval.
Get the Right PVC Formulation for Your Application
The right PVC additives play an important role in processing efficiency, product consistency and long-term performance. At Innovative PVC, we work with you to identify compound requirements that meet your manufacturing processes and end-use specifications.
Get in touch with us to discuss your application and find a PVC compound that delivers the performance you need.
FAQs
What are PVC additives, and why are they important?
PVC additives are ingredients incorporated into a PVC formulation to achieve specific processing and performance characteristics. These include thermal stability, flexibility, impact resistance and flow behaviour, depending on the intended application.
How do PVC stabilisers improve processing performance?
PVC stabilisers help protect the material against thermal degradation during processing. Their effectiveness depends on the formulation, processing temperature and exposure time, making heat-stability testing important when evaluating replacement compounds.
How do PVC plasticisers affect flexibility and durability?
PVC plasticisers increase flexibility and influence how a compound performs under different service conditions. Changes in plasticiser type or concentration can affect low-temperature flexibility, migration resistance and long-term hardness, even when the initial Shore A hardness remains unchanged.
Why should manufacturers test PVC formulations before substituting compounds?
Two PVC formulations with identical hardness ratings may behave differently during processing and in finished products. Testing factors such as thermal stability, retained flexibility, compression recovery and application-specific performance helps manufacturers determine whether a replacement compound meets their requirements.
