The crucial role of material hardness and the contribution of Vintech PVC

The hardness of a plastic material is a crucial parameter that directly affects its resistance to scratches, dents, and other forms of mechanical wear. The ability of a material to maintain its characteristics under stress is fundamental to determine its suitability in specific applications.

Vintech represents a significant step forward in the field of plastic coatings, offering custom solutions that meet a variety of industrial needs, while ensuring high and long-lasting performance.

As part of the continuous search for advanced solutions for long-lasting protective coatings, R.P. Rivestimenti Plastici s.r.l. has developed the Vintech compound in-house, a PVC designed for applications on metal substrates of various kinds.

This innovative material was the focus of an in-depth study conducted in collaboration with the Department of Materials Science and Chemical Engineering of the Politecnico in Turin. For this trial, R.P. Rivestimenti Plastici s.r.l. created and then made available seven different formulations of Vintech, each characterised by a different plasticizer content and with a hardness measured in Shore A ranging from 30 to 90Sh.

This study allowed us to examine how variations in hardness affect the performance of coatings, showing Vintech’s extreme versatility and adaptability to a variety of industrial needs.

The importance of hardness in plastic materials

The hardness of a plastic material is a measure of its resistance to permanent deformation under the application of a force over a given period of time. This parameter is fundamental to determine the ability of the material to resist scratches, dents, penetrations and other forms of mechanical wear to which the items are notoriously subject.

Hardness is a crucial factor in the selection of plastic materials for specific applications. For example, in applications where materials must resist scratches and abrasions, such as coatings or machine parts, where greater hardness is preferable. On the other hand, less hard plastic materials may be more suitable for applications where a certain flexibility and shock absorption capacity is required, or again, vibration and noise reduction.
Therefore, the hardness of a plastic material provides key indications about its softness and performance in everyday use situations, directly influencing the choice of material for specific engineering and industrial applications.

Hardness standards: evaluation methods and criteria

As hardness is a particularly significant parameter affecting the performance and suitability of applications, there are reference standards relating to the methods and criteria used to measure this property in elastomeric materials, such as rubbers, plastomers and polymers.

The use of reference hardness standards is crucial for several reasons:

Comparability: they allow direct comparison between the hardness of different materials.
Reliability: they provide consistent and reproducible measurements.
Selection of materials: they help engineers and designers in choosing the suitable material for specific applications based on deformation resistance requirements.

Hardness is usually assessed using different standardised tests, which vary depending on the type of material and the specific application.

Some of the most common methods for measuring the hardness of plastics include:

Shore Hardness Scale: the Shore hardness scale is commonly used for elastomers and some thermoplastic polymers.
It measures the penetration depth of a standard penetrator applied directly to the sample. There are two main types of Shore tests:
- Shore A: used for softer materials such as rubber and flexible plastic. The test uses a durometer with a blunt conical tip that penetrates the material on a surface no less than 8/10 millimetres.
- Shore D: used for harder materials such as rigid plastics. This test uses a durometer with a sharper conical tip.
The result is expressed on a scale from 0 to 100 Sh.A, where a higher number indicates greater hardness.
The harder the product is considered, the greater its ability to resist wear.
This is especially true for harder PVC, which offers several significant advantages. First of all, it’s extremely resistant to impacts and scratches, making it ideal for applications where high durability is required. Moreover, the hardest PVC maintains its shape and functionality even under extreme environmental conditions, guaranteeing a long life over time. Finally, it requires little maintenance, making it a cost-effective and efficient choice for multiple uses.

Rockwell Hardness Scale: The Rockwell Hardness Test is most commonly used for metals, but some of its variants are also used for plastics. Rockwell hardness is measured in different scales, for example:
- Rockwell R: used for softer plastic materials.
- Rockwell L and M: used for harder plastics.
The test measures the depth of penetration of a penetrator under a pre-set load.

Vickers Hardness Scale: The Vickers Hardness Test can also be used for some rigid plastics. This method uses a diamond pyramid penetrator and measures hardness by calculating the surface area of the imprint left by the penetrator. Vickers hardness is expressed in kilogram-force per square millimetre (kgf/mm²).
Brinell Hardness Scale: the Brinell hardness test, similarly to the Vickers one, is most commonly used for metals, but can be adapted for some rigid plastics. It uses a steel ball or tungsten carbide to penetrate the material under a pre-set load, and the hardness is calculated based on the footprint size.

Standardisation organisations and international hardness standards

How to understand and analyse the performance of a plastic material before choosing it? The reference hardness standards are established by standardisation organisations at both the national and international level. These organisations develop, publish, and maintain technical standards that ensure quality, safety, and interoperability across various industry sectors. Some of the main organisations that set the hardness standards for plastics include:

International organisations:
- ISO (International Organization for Standardisation): is a worldwide federation of national standardisation bodies. ISO develops and publishes international standards in a wide range of sectors, including those related to the hardness of materials. For example, the ISO 868 standard specifies how to determine the Shore A and D hardness for plastics and rubbers.
- ASTM International (American Society for Testing and Materials): is one of the leading international standardisation organisations that develops and publishes technical standards for a wide range of materials and products. ASTM standards for hardness include, for example, ASTM D2240 for Shore hardness and ASTM E18 for Rockwell hardness.
National organisations:
- ANSI (American National Standards Institute): coordinates the US voluntary standardisation system and accredits organisations that develop standards, including ASTM International.
- DIN (Deutsches Institut für Normung): is the German standardisation organisation that develops standards for a wide range of industrial products and processes. For example, DIN 53505 describes the method for determining Shore hardness for elastomeric materials such as Vintech and other types of PVC.
- BSI (British Standards Institution): is the British national organisation that develops and publishes standards. As well as adopting many ISO standards, BSI also develops national standards.

Many of these bodies work together to harmonise their standards, ensuring international compatibility around the world. For example, ISO standards often result from standards developed by ASTM or other national organisations, facilitating their global adoption and implementation. These organisations ensure that hardness tests are performed consistently and repeatably, so that results can be reliable and comparable worldwide.