Węże poliuretanowe / Węże PU

General

Block copolymer polyurethane, which consists of interlinked PUR hard and PUR soft segments, has superior properties compared to many other plastics. The hard segments are responsible for the extremely high mechanical strength, while the soft segments offer extreme flexibility and dynamic load-bearing capacity.

Abrasion resistance

The abrasion resistance of our Pre-PUR^® polyurethanes is approximately 2.5–5 times better than that of many rubber raw materials and approximately 3–4 times higher than that of most soft PVCs (measured at 20°C). This was determined by a standard measurement. In addition, it was found that these significant differences are even greater in everyday use. The detailed results can be found in the comparison chart:

The high tensile strengths and elongation at break values, combined with very high elasticity and unusually high creep resistance, are static and dynamic load-bearing capacities that far exceed the values of many other rubber-like materials. PUR hoses tolerate over-bending in the bending radius and repeated rhythmic stress during intermittent operation well due to their good resilience and low compression set. This enables us to develop special hoses under conflicting boundary conditions that allow high tensile and pressure loads despite their low weight. Due to their high tear resistance, hoses damaged by cutting, for example, can in most cases continue to be used by bandaging without having to absorb axial forces. This is hardly possible with hoses made of other materials.

Low-temperature flexibility

At low temperatures, polyurethane becomes increasingly hard but, unlike many other plastics, it does not become brittle. All of our polyurethanes passed the notch impact test without breaking, even at –30°C. The long molecular chain length (high molecular weight) of our raw materials results in significantly greater flexibility at low temperatures. Compared to many competing PUR products, our hoses require significantly less bending force when bent in cold conditions and are less prone to kinking. Our ether TPU's are generally even more flexible in cold conditions than the ester types.

Fire behaviour

(The following information does not apply to electrically conductive, antistatic and flame-retardant types.) Like all organic substances, polyurethane is flammable. The fire gas toxicity and smoke density are usually assessed in accordance with DIN 53436. Based on the results of this leading international standard, the potential for harmful substances to be released (acute inhalation toxicity) at 800°C is no more critical than that of other natural products such as wood, wool or leather.

Our flame-retardant polyurethane hoses for the woodworking industry are type-tested in accordance with DIN 4102-B1 and meet the safety requirements of the German Woodworking Industry Association (Holz-BG). Our products are tested in accordance with UL94, and many products achieve HB, V2 or V0 classification.

Resistances

Pre-PUR^® raw materials, including stabilisers, result in better resistance and longer service life for PU hoses. Hydrolysis measurement in water at 80 °C is ideal for comparison. During hydrolysis measurement, we measured the abrasion and tensile strength between hoses made of Pre-PUR^® and ester TPU. Our ester Pre-PUR^® is compared to a commercially available ester TPU in the following graph:

Resistance to certain materials, substances and processes:

Acids and alkalis

Our polyurethanes are highly resistant to diluted acids and alkalis. However, they are attacked by concentrated solutions and strongly oxidising acids.

Oils, fats and fuels

Our TPUs offer excellent resistance to pure mineral oils and fats. ASTM test oils No. 1, 2 and 3 do not cause any loss of strength at 20°C, and even after three weeks of storage at 100°C, no degradation occurred. Our TPUs are resistant to diesel, kerosene and the FAM test fluid Fuel A (ASTM D 471) without any loss of strength, and are still conditionally resistant to Fuel B and C.

Saturated aliphatic hydrocarbons

Contact with, for example, isooctane and petroleum ether causes slight reversible swelling of approx. 1-3%, which is associated with a decrease in tensile strength of less than 20%. There is no degradation of the material.

Aromatic hydrocarbons

In benzene, toluene and xylene, for example, PUR swells significantly by up to approx. 50% and loses strength to a similar extent.

Solvents

Alcohols such as ethanol and isopropanol cause 15-30% swelling and a 40-60% drop in tensile strength. Ketones such as acetone, methyl ethyl ketone (MEK) and cyclohexanone (Anon) and aliphatic esters such as ethyl acetate and butyl acetate act as partial solvents, making PUR unsuitable for continuous use. Highly polar organic solvents such as dimethylformamide (DMF), N-methylpyrrolidone and tetrahydrofuran (THF) dissolve polyurethanes.

Water

Our polyurethanes can be stored in water at 20°-40°C for years. In the case of polyester polyurethane, irreversible decomposition (hydrolysis) of the polyester chains occurs in contact with warm water or steam at temperatures above approx. 60°C. However, thanks to its stabilisation and extremely high molecular weight, our ester Pre-PUR loses only 8% of its tensile strength after 56 days at 80°C (see above). Tubes made of ether Pre-PUR are insensitive to hydrolytic degradation and are the even better solution in such cases.

Heat ageing

Our hoses, which are also stabilised against hot air ageing, achieve extreme service lives in heat. After one year of use at 100°C, half of the tensile strength can still be measured. At 120°C, our ester Pre-PUR has lost only half of its strength after 4 months and our ether Pre-PUR after 2 months.

Weather

PUR is highly resistant to oxygen, ozone and UV light. Continuous and intense weathering causes yellowing and a reduction in mechanical strength. In such cases, additional UV stabilisers or colour pigments should be added.

High-energy radiation

Polyurethane is superior to most other plastics (such as PTFE, natural rubbers, PE, PVC, silicone, etc.) in its resistance to α, β and γ radiation. However, embrittlement also occurred at 108 Rad.

Microbes

Unstabilised ester TPU can be destroyed by prolonged contact with earthy substances or heavy soiling under conditions favourable to microbes, as the enzymes released by the organisms damage the chemical bonds. Under very unfavourable conditions, initial damage occurred after 8–24 weeks. Ether polyurethanes are inherently more resistant to microbes.