- A selection of Lurethane® products
Lurethane
The commercial production of castable polyurethanes was successfully pioneered by Ludowici Ltd. in the mid-sixties and is marketed under the tradename of Lurethane®. The company designs, formulates, manufactures and distributes an extensive range of Lurethane® products for industrial use in both the domestic and international manufacturing fields.
The Product
®Lurethane is a thermoset elastomeric polyurethane which possesses toughness and durability far in excess of most rubbers and plastics. One of the most important characteristics is its extremely broad hardness spectrum, which ranges from eraser-soft to golf ball-hard. This hardness is governed by the pre-polymer's molecular structure, not by the addition of plasticisers and fillers. Lurethane® combines the toughness of metal with the elasticity of rubber and will withstand the most severe abuse. It offers an outstanding alternative to more traditional materials, and is ideally suited for use in an ever- increasing range of demanding applications.
The Advantages
Lurethane® has remarkable resistance to abrasion and low temperature stiffening. It has high load-bearing capacity, hydrolytic stability and castability as a liquid raw product. Harder grades can be machined, and the product has superior resistance to oils, chemicals, radiation and weathering. Lurethane® also has an extremely high flex life and cut resistance.
Quality
The company has in-house quality control systems in place, which ensure a commitment to manufacture Lurethane® products of consistent dimension and formulation. These quality control systems extend to machine shops in Christchurch and Auckland, where Ludowici Plastics engineers use a variety of machine tools and plant to manufacture Lurethane® for specific applications. The company also actively pursues a policy of continuous improvement, which covers every aspect of its business dealings and product development.
Service
Customer service is an all-important facet in Ludowici Plastics company philosophy. Both technical and sales personnel take an active role in assessing individual requirements for specific applications. They offer soundly-based recommendations and solutions on the use of Lurethane® products, and take pride in their problem-solving ability.
Benefits
The major characteristic of Lurethane® is that it possesses unique and unprecedented physical properties. These properties enable all Lurethane® products to be classified as engineering material.
Why use Lurethane?
- cost effectiveness
- Extended life lessens process downtime
- Inexpensive tooling & equipment costs
- Small production runs
- performance
- Abrasion resistance
- Tear resistance
- Load-bearing ability
The advantages of Lurethane®
Lurethane®, because of its physical properties, offers many advantages over traditional metals, rubbers and plastics in a wide range of applications.
- advantages over rubber
- Higher cut and tear resistance
- Higher load-bearing capacity
- Higher abrasion resistance
- Pourable and castable
- Will cast wide range of shapes and sizes
- Excellent saltwater resistance
- advantages over plastic
- Better impact resistance
- Lower tooling costs
- Higher abrasion resistance
- Improved elastomeric memory
- Wider hardness range
- Smaller production runs
- advantages over metal
- Higher abrasion resistance
- Less noise pollution
- Very cost-competitive
- More corrosion-resistant
Properties
Hardness
Polyurethanes are usually classified according to their degree of hardness. The accompanying chart indicates how Lurethane® rates in terms of hardness when compared with other materials. Lurethane® can be manufactured in a range of hardness grades to suit a wide variety of industrial applications, from 50 Shore A to 70 Shore D. Hardness is identified by the following standard colours:-
| PU60A | 60A | Green |
| PU20 | 75A | Orange |
| PU30 | 85A | Yellow |
| PU40 | 90A | Red |
| PU50 | 95A | Black |
| PU70 | 70D | Blue |
Abrasion Resistance
The outstanding abrasion resistance of Lurethane® offers solutions in many applications where severe wear is present. It also offers remarkable durability, when compared to rubber, plastic and even metals. Abrasion resistance is a complex problem and is a vitally important consideration when selecting the appropriate Lurethane® formulation for the intended purpose. This decision is usually based on actual experience, simulated service tests, or informed advice from one of Ludowici Plastics sales engineers.
Impact Resistance
Practically all elastomers, including Lurethane®, will yield under impact at lower hardness levels. Elastomeric materials should do this, but when traditional elastomers are forged to higher hardness levels, they tend to lose elasticity and will crack under impact. Lurethane®, even at the highest hardness level, has significantly better impact resistance than many plastics and also exhibits good low temperature impact resistance and brittle points. This impact resistance, together with other properties associated with high hardness levels, enable Lurethane® to provide the ideal solution to many engineering applications.
Compression
Lurethane® has a much higher load-bearing capacity in both compression and shear than do conventional elastomers of comparable hardness. Compression, as it relates to Lurethane®, means that the elastomer will not change in volume under pressure, but will undergo a change in shape to the limit of its strength under load. When a load is placed on polyurethane, it reacts by exerting force consistently in all directions.Lurethane® will change shape under load, but will return to its original shape when that load is removed. This characteristic can offer important advantages and provide solutions to problems in many applications.
Friction Coefficient
Lurethane® has a low, unlubricated coefficient of friction that decreases as hardness increases. Surface contact is very important in bearing applications which is why Lurethane® with its friction characteristic, load-bearing capacity and abrasion resistance, is used in bearings and bushes.
Water Resistance
Water absorption is very low and volume swell is insignificant. Lurethane® is highly-resistant to water at room temperature and has superior long-term stability in water as hot as 50°C. Constant use in water over 55°C is not recommended. Consult Ludowici Plastics sales engineers about the suitability of Lurethane® for specific applications.
Oxygen, Ozone and Weather Resistance
Lurethane® is highly-resistant to oxygen and ozone in atmospheric concentrations and no observable degradation is found. Compounds will darken and physical properties will be reduced by prolonged exposure to ultra-violet light, but no significant surface deterioration occurs. These factors allow Lurethane® to be used in conjunction with electrical equipment, as it does not harden or crack like many plastics.
Oil, Grease, Chemical and Solvent Resistance
The resistance of Lurethane® to chemical attack means it can be widely used in many different environments. The exceptions are aromatic hydrocarbons and polar solvents, which have a moderate to severe effect on polyurethane material. Oil and solvent resistance makes Lurethane® particularly suitable for use with lubricating oils and automotive fuels. However, if severe use is intended with corrosive fluids or chemicals, specific laboratory or usage data should be first obtained from Ludowici Plastics sales engineers.
Resistance to Other Factors
Lurethane® formulations do not support fungus or mildew growth and are generally resistant to microbiological attack. They are considered to have the best resistance to gamma radiation, retaining a high proportion of their original flexibility and toughness during exposure. Lurethane® is self-extinguishing and, if required, can be manufactured with flame-retardant compounds, which are completely non-burning under test conditions.
Non-marking
Lurethane® will not damage polished or coated stock, unlike metals which tend to scratch or mark highly- polished surfaces. Soft materials are gripped by Lurethane® with a firm yet gentle contact.
Machineability
Harder grades can be machined using conventional plant. They can be drilled, routed, sawn, line-bored, turned and shaped. Lurethane® requires special skills to machine effectively. Machining data can be supplied, or Ludowici Plastics engineers will undertake product machining in one of the company's well-equipped machine shops in either Auckland or Christchurch.
Moulding
The ability to mould complex shapes is one of the key advantages of Lurethane®. It will also bond to metal surfaces - ideal for wheels, rollers and inserts. Lurethane® will successfully mould components weighing either a few grams or many kilograms, and will produce those components economically in either a small or large production run.