A supplier asks which document you want the polyurethane against — GOST or TU — and the buyer is at a loss because the drawing shows only the part name. In practice, a node fails not because of the type of normative document but because hardness and wear resistance do not match the actual load. The standard type alone does not save a part from premature wear. This article explains how GOST and TU differ, which actual properties determine the service life of a polyurethane part, and how to state technical requirements so that the node runs its designed life.
GOST or TU: What the Documents Actually Mean
The direct answer: GOST and TU are two types of normative documents, not two different materials. GOST sets general requirements for a product type at the interstate level; TU defines the technical specifications for a specific product or material from the manufacturer. Both documents fix requirements for properties and the methods of verifying them — but neither guarantees that the part suits your particular node.
For an engineer this leads to a simple conclusion: it is the specific numbers in the document that matter, not its name. A part made to TU with correctly set hardness and abrasion will outlast one made to a general standard whose properties do not match the operating conditions. A competent technical specification therefore describes not the type of document but the operating parameters of the node.
Cast polyurethane is convenient precisely because its properties are built in at the formulation stage to suit the task. By adjusting the composition, a material of the required hardness and elasticity is obtained while maintaining high wear resistance. Free-casting technology allows a part to be manufactured to specific technical requirements rather than forcing the node to work with a single universal material. Typical products are listed in the polyurethane product catalogue.
It is also important to understand the reverse side: behind an identical reference to a standard, parts from different grades of polyurethane with different hardness and wear resistance may be supplied. A standard sets the frame of acceptable values and the control method, but within that frame the properties vary over a wide range. A requirement for “polyurethane to such-and-such standard” without specifying hardness and operating conditions therefore leaves the supplier room to choose a cheaper grade that formally complies with the document but does not withstand the load.
Which Properties Actually Determine Service Life
Service life of a polyurethane part is determined by three primary properties: wear resistance, operating temperature, and hardness. These are what should be placed in technical requirements instead of general formulations such as “wear-resistant” or “strong.” These parameters are measured by standard methods and can be verified.
Wear resistance is assessed by DIN 53516 or ISO 4649: this is the volume loss of the material in mm³ in a standard abrasion test, and a lower figure means higher resistance. Cast polyurethane shows 38-39 mm³, while SBR rubber reaches 100-200 mm³. A several-fold difference maps directly onto part service life in an abrasive node.
The operating temperature of cast polyurethane is -60 to +100 °C, and hardness is set in the range from 50 Shore A to 70 Shore D. Fixing these limits in the specification matters because a node in a cold store and one near heated equipment require different formulations. The practical rule: describe operating conditions in numbers first, then select the material against them — never the other way around. Testing methods and property explanations are in the reference information section.
Comparison of Polyurethane with Other Materials in Numbers
To make technical requirements well-grounded, it is useful to see how polyurethane compares with other materials on the same measurable parameters. The table compiles reference values from standard tests.
| Material | Abrasion DIN 53516, mm³ | Operating t, °C | Hardness | Tensile strength, MPa | Rebound elasticity, % |
|---|---|---|---|---|---|
| Polyurethane TIMOL | 38-39 | -60…+100 | 85A-95A | 39-87 | 34-61 |
| SBR rubber | 100-200 | -40…+80 | 40A - 80A | 8-20 | 30-55 |
| NBR rubber | 80-150 | -30…+100 | 40A - 90A | 10-25 | 20-45 |
| Natural rubber NR | 60-130 | -50…+70 | 30A - 80A | 20-30 | 40-75 |
| Capron PA6/PA66 | 30-90 | -40…+100 | 75D - 85D | 60-85 | 5-15 |
Polyurethane shows the lowest abrasion among elastomers while retaining high rebound elasticity of 34-61 %. Natural rubber has higher rebound but poor oil resistance and an upper limit of only +70 °C. Capron is close in abrasion but its rebound is only 5-15 %, so it cracks under impact. These numbers illustrate why technical requirements should be built on properties, not document types: behind the same GOST name, completely different materials with different service lives may stand.
Engineer’s tip: instead of requiring polyurethane against a specific standard, describe three things in the specification: operating temperature range, wear character (abrasive, impact, sliding), and required Shore hardness. From these three parameters a technologist can select the formulation more accurately than from any marking. A standard is useful as a way of fixing the control method, not as a substitute for engineering calculation.
How to Verify Polyurethane Compliance
Verification starts with the same three parameters you put in the specification. Hardness is checked with a Shore durometer directly on the finished part — the quickest and most accessible check. The value must fall within the range you specified for the grade you ordered, not just within the broad frame of the standard.
Wear resistance is assessed by standard DIN 53516 or ISO 4649 abrasion on a sample, and resistance to the medium is checked by soaking a sample in the service oil or solution. Visual inspection of the part body in cross-section reveals any voids from poor degassing. The practical acceptance rule: a part must comply not with a document name but with the combination of measured properties, so the specification should state from the outset which methods will be used for acceptance.
How to State Technical Requirements for a Polyurethane Part
A competent technical specification for a polyurethane part contains dimensions, required Shore hardness, operating temperature range, and a description of the load. Add the nature of the contact medium: presence of oils, water, chemicals, abrasive. This data allows the formulation to be selected and the working layer thickness calculated, rather than falling back on a single universal grade.
The factory manufactures parts from a drawing, sketch, or worn sample, so a non-standard size is not a problem. Free-casting technology does not require expensive tooling, which makes individual parts and production batches equally economical. If you have an existing rubber or metal part, it can serve as a prototype to recalculate in polyurethane.
This approach removes most disputes about the document type before the order is placed. Rather than negotiating whether material is supplied to GOST or TU, the customer and technologist fix measurable parameters in the specification: hardness, operating temperature, wear character, and dimensions. These numbers are unambiguous and verifiable by standard tests, so the finished part suits not the name of a document but the real conditions of the node in which it will work.
For advice on properties, hardness selection, and calculation against your technical specification, contact us via TIMOL factory contacts. Engineers will help translate general requirements into specific numbers and arrange manufacture of the part for your node.