Material Data Sheets

Polyurethane

General information:

The polyurethane block copolymer consisting of linked segments of hard and soft PUR has superior properties compared to many other plastics. The hard segments provide extremely high mechanical stability, while at the same time the soft segments give the material high flexibility and dynamic load capacity.

The intrinsic colour of PUR is opaque to transparent and turns yellowish with age. The material can be dyed or painted subsequently without difficulty.

Mechanical properties:

According to standard tests, the abrasion resistance of our polyurethanes is about two and a half to five times higher than for many rubber raw materials and about three to four times higher than that of soft PVC. The differences in the field are frequently even greater, since the excellent damping and impact resilience of polyurethane does not come into play with the standard test methods.

The high tensile strength as well as values for elongation at break coupled with very high elasticity and unusually high creep resistance result in static and dynamic load capacities that far exceed the values of many other rubber-like materials. PUR hoses handle overstraining in the bending radius and repeated rhythmic stress from intermittent operation well due to their good resilience and low compression set. This enables us to develop special hoses with good performance under opposing conditions, which can handle high tensile and compression loads despite their low weight. The high resistance to tear propagation means, for example, that a hose with cut damage can be patched and continue to be used without the need to relieve the axial forces. This is rarely possibly with hoses made from other materials.

Low temperature flexibility:

Polyurethane becomes increasingly harder with lower temperature, but in contrast to many other plastics, it does not become brittle. Thus all our polyurethanes withstood the notched bar impact test even at -30°C without breaking. The long molecular chains (high molecular weights) of our raw materials give significantly better flexibility at low temperatures. Compared with many competitive products made of PUR, our hoses require significantly less bending force under cold conditions and are less prone to kinking. Our ether TPUs are fundamentally even more flexible at low temperatures than ester TPUs.

Fire behaviour:

(The following information does not apply to electrically conductive, antistatic and flame-resistant types.) Like all organic materials, polyurethane is combustible. The toxicity of the combustion gases and smoke density are usually measured according to DIN 53436. Judged on the basis of this leading international standard, the potential release of hazardous substances (acute inhalation toxicity) at 800°C is not even more critical than that of natural products such as wood, wool or leather.

Our flame-resistant polyurethane hoses for the wood processing industry are type-tested according to DIN 4102-B1 and meet the safety requirements of the Holz BG (the German liability insurance association for the wood industry). Our products are tested according to UL94 and many products achieve the classification HB, V2 oder V0. Moreover, AIRDUC 352 has been tested according to DIN 54837 and DIN 5510 part 2 and meets the requirements for flammability class S4.

Resistances:

Our high-quality raw materials with special stabilisers demonstrate considerably better stability and significantly longer service life than can be obtained with many other products.

An appropriate measure of this is also hydrolysis testing in water at 80°C, since the mechanism of chemical degradation of polyester-polyurethane is frequently hydrolysis of the polyester chains. The chart shows a comparison of our ester Pre-PUR and an other typical commercial ester TPU. Our ether Pre PUR has even better chemical resistance than our ester Pre PUR, however it tends to a greater increase in volume and loss of strength in contact with swelling media.

Acids and bases:

Our polyurethanes show good resistance to dilute acids and bases. However, they are subject to attack by concentrated solutions and strongly oxidizing acids.

Oils, fats and fuels:

Our TPUs offer excellent resistance to pure mineral oils and fats. ASTM test oils 1, 2 and 3 cause no loss of strength at 20°C nor after three weeks of exposure at 100°C. Our TPUs are also resistant to diesel, kerosene and the FAM test fluid Fuel A (ASTM D 471), showing no loss of strength, and show limited resistance to Fuels B and C.

Saturated aliphatic hydrocarbons:

In contact with isooctane and petroleum ether, for example, there is a small degree of reversible swelling (about 1 to 3%), accompanied by a drop in tensile strength of less than 20%. There is no degradation of the material.

Aromatic hydrocarbons:

PUR swells strongly up to 50% in contact with benzene, toluene and xylene, for example, and loses a similar proportion of strength.

Solvents:

Alcohols, such as ethanol and isopropanol, cause about 15 to 30% swelling and a decrease in tensile strength of 40 to 60%. Ketones, such as acetone, methyl ethyl ketone (MEK) and cyclohexanone and aliphatic esters, such as ethyl acetate and butyl acetate, act as partial solvents, so PUR is not suitable for long-term use. Highly polar organic solvents, such as dimethylformamide (DMF), N-methylpyrrolidone and tetrahydrofuran (THF), dissolve polyurethanes

Water:

Our polyurethanes can remain in water at 20° to 40°C for years. Polyester polyurethanes in contact with warm water or steam at about 60°C or higher undergo irreversible degradation (hydrolysis) of the polyester chains. However, due to stabilization and extremely high molecular weight, our ester Pre PUR loses only 8% of its tensile strength after 56 days at 80°C (see above). Hoses made from ether Pre PUR are not sensitive to hydrolytic degradation and are an even better solution in such cases.

Heat aging:

Our hoses are also stabilised against hot air aging and are able to achieve an extremely long service life under heat conditions. Thus even after a year of usage at 100°C, half the tensile strength remains. At 120°C our ester Pre PUR loses only half its strength after 4 months, and the strength of our ether Pre PUR is reduced by the same factor after 2 months.

Weathering:

PUR has good resistance to oxygen, ozone and UV light. Intensive, long-term weathering leads to yellowing and a loss of mechanical properties. In such cases, additional UV stabilisers or colouring pigments should be added.

Energetic radiation:

The resistance of polyurethane α-, β- and γ-radiation is superior to most other plastic materials, such as PTFE, natural rubbers, PE, PVC, silicones, etc.). However, at doses of 108 rad, the material does become brittle.

Microbiological:

Unstabilized Ester TPU in long-term contact with soils and similar substances or heavy contamination under conditions favourable to microbes can be destroyed by enzymes from the organisms which attack the chemical bonds. Under very unfavourable conditions the first signs of damage can be seen after 8 to 24 weeks. Ether polyurethanes are inherently resistant to microbiological attack over long periods.


Polyvinyl chloride - soft PVC

PVC is an amorphous plastic. Nonetheless, this material is distinguished by its outstanding media resistance. This is why PVC hoses are frequently used in applications with difficult media or environments. It is only attacked by a few solvents (aromatics, esters, ketones and chlorinated hydrocarbons).

PVC is an inexpensive, versatile material, but it does have the following disadvantages:

Its operating temperature range as well as resistance to wear are significantly less than PUR. Moreover, with flexible hoses, migration of the plasticiser can cause brittleness over time, leading to premature failure.

Today, PVC is becoming increasingly undesirable for the following reasons:

  • Disposal problems (PVC is classified as hazardous waste in many cases)
  • High clean-up costs after a fire
  • Many customers have issued a general prohibition against the use of PVC
  • Import duties on PVC products in certain countries
  • The plasticisers are classified as possible health hazards in some cases

Polyethylene

Polyethylene belongs to the polyolefin group, which includes polypropylene (PP), ethylene vinyl acetate (EVA), ethylene acrylate (AEM) and the polyolefin elastomers. The umbrella term "polyolefin" cover linear (i.e. unbranched) polymers with a carbon chain backbone that are produced by polymerization.

The polyethylene used by NORRES is extremely well suited to hose extrusion due to its particular resistance to stress cracking and good impact resistance at low temperatures. In addition to that, the walls of AIRDUC® PE-F hoses produced by NORRES comply with the food use regulations of EU Directive 10/2011 as well as the FDA regulation 21 CFR 177.1520 (c) 3.2 (see also the appendix "Legal requirements for food contact").

Polyolefins are superior to polyurethane and PVC materials in their chemical resistance in contact with fatty substances in food (essential oils, as well animal fats and oils), most polar organic media, particularly alcohol and concentrated organic and inorganic acids and bases. Summary of key properties:

  • Environmentally friendly material only carbon dioxide and water are produced during combustion)
  • Low resistance to mineral oils and fats, fuels and natural gas
  • Considerable resistance to most organic and inorganic chemicals, inorganic salts, alkalis and bases (except for oxidizing agents)
  • Resistant to many solvents
  • Low water vapour permeability, but high gas permeability
  • No plasticisers
  • Odourless and without taste

Polypropylene

  • This material is very similar to PE in its mechanical, electrical and optical properties as well as chemical resistance.
  • Very low density -> low weight (approx. 25% lighter than TPU)
  • High hardness and very low elongation
  • Good dimensional stability at high temperatures up to about +110°C
  • Good resistance to many media
  • Very low water vapour permeability, but high gas permeability

Vulcanised thermoplastic elastomers (TPE-V)

The hoses made by NORRES that are labelled TPE (or TPE-V) are hoses manufactured from a thermoplastic rubber. This completely vulcanised polyolefin material belongs to a group of elastomers which provide an excellent combination of the performance characteristics of vulcanised rubber, such as thermal resistance and low compression set, with the superior processing characteristics of thermoplastics. The manufacture involves a special dynamic vulcanization process, which produces fully networked rubber particles distributed in a continuous matrix of thermoplastic material. The rubber particle size of a micron or less results in excellent physical properties for the material.

TPE-V has a resistance to environmental influences corresponding to that of standard EPDM rubber mixtures, whereas the chemical resistance is comparable to chloroprene rubber mixtures.

The thermoplastic rubber used by NORRES has excellent resistance to heat aging and maintains its tensile properties after prolonged exposure to high temperature better than most vulcanisable rubbers.

Summary of key properties:

  • Temperature range -40°C to +125°C (150°C):
    The brittle point is at about -60°C
    Outstanding hot air aging behaviour at temperatures up to 150°C for periods up to two weeks and for longer periods at up to 125°C
  • Good resistance to aqueous solutions, dilute acids and bases, organic solvents, mineral oils and grease and antifreeze
  • Very good resistance to ozone and weathering
  • Mechanical strength similar to PVC
  • Very good dynamic fatigue strength and good damping ability
  • Low rate of combustion, satisfying FMVSS302 requirements.
  • Classified as slow burning according to UL 94: 94 H.B.

PTFE (TEFLON®*)

TEFLON® PTFE is a linear, completely fluorinated polymer of high molecular weight. The carbon-fluorine bonds of PTFE are extremely stable and contribute considerably to the extraordinary characteristics profile of the material. The fluorine atoms form a protective shell around the chain of carbon atoms; they shield the carbon chain from the effect of chemicals and provide outstanding chemical and thermal stability. The protective shell also reduces the surface energy and contributes to the low coefficient of friction and anti-stick (release) properties.

PTFE responds neutrally to nearly all chemicals and is neither attacked nor dissolved by organic solvents. TEFLON® PTFE contains no extractable materials that migrate and can affect nearby materials in an unfavourable manner. This is among the reasons for the physiological compatibility of PTFE. It is extremely hydrophobic and repels water almost completely. It also shows little effect from oxygen, ozone and both visible and UV light. Moreover, TEFLON® is resistant to microbes. Fluoropolymers are not attacked by fungus and bacteria.
TEFLON® is not combustible for the most part (UL 94: 94 V0). Due to its high melt viscosity, PTFE does not drip if it is heated above its melting point. Its flame propagation and heat dissipation are extremely low.

PTFE has extremely low friction coefficients. Because of its low surface energy, PTFE demonstrates excellent anti-stick properties and thus prevents encrustation of all kinds.

TEFLON® PTFE is extremely stable at high temperatures. Its constant use temperature is around 260°C. Moreover, it is one of the few polymers to retain a certain durability and strength at extreme low temperatures.


VITON®*

Viton® has proven its worth through years of field use under extreme environmental conditions ? the best credentials to satisfy your most demanding applications.

In many applications hoses are exposed not only to brief temperature spikes but also higher temperatures of use. Depending on the task, Viton® can handle constant use temperatures as high as 205°C and has excellent resistance to many aggressive fluids. It has excellent resistance to aromatic and aliphatic hydrocarbons, moderate resistance to bases and poor resistance to solvents. Viton® has outstanding resistance to atmospheric oxidation, sunlight and ozone. Viton® also has very low permeability to gases.


HYP

HYP chlorosulfonated polyethylene has demonstrated its long service life under extreme conditions of use many times. It is used in a wide range of industrial applications where the demands on material properties are very high. The hoses made by NORRES with HYP coated webbing satisfy many of these demanding requirements.

The advantages of HYP are clear when exposed to high temperatures and oxidizing chemicals. The HYP coated webbings used by NORRES withstand kinking and wear, as well as destruction by the actions of weather, ultraviolet light and ozone. Moreover, HYP has excellent resistance to oil, fuel, acids and bases. On the other hand, resistance to solvents, aromatic and aliphatic hydrocarbons is only moderate.


NEOPRENE

Neoprene chlorinated rubber is a very versatile, many-sided synthetic rubber that has demonstrated its outstanding properties in many industrial sectors for over 70 years. It was originally developed as an oil resistant alternative to natural rubber. Neoprene has a balanced combination of properties:

  • Excellent resistance to weathering, UV and ozone
  • Good oil and chemical resistance
  • Usable over a wide temperature range
  • Good fire behaviour

Silicone

Silicone rubber belongs to the class of materials known as silicones, whose backbone structure is composed of extremely stable silicone-oxygen chains, referred to as polysiloxane chains. This structure gives silicone rubber particularly advantageous properties compared to other elastomers, including outstanding resistance to heat, cold, weathering, ozone and oxidation. It has only moderate resistance to oil, fuel, acids and solvents and poor resistance to aromatic and aliphatic hydrocarbons. The mechanical properties are relatively constant over the entire temperature range.


All dimensions and values specified are approximations and were determined at 20°C. We reserve the right to make technical changes.

* TEFLON® and VITON® are registered trademarks of DuPont.

 

Engineering modifications subject to change.

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