Material properties

Material Properties

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The properties and performance characteristics of any rope are reliant on the materials from which they are made.  The following series of tables sets out to compare the key physical properties of the most frequently used materials. 
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MODULUS, STRENGTH AND ELONGATION

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Modulus, strength and elongation are all interconnected 
MATERIALMODULUS
Tenacity (g/Denier)
STRENGTH
Tenacity (g/Denier)
ELONGATION
(% at break)
Dyneema SK99 (HMPE)1800483.6
Dyneema SK78 (HMPE)1267403.5
Dyneema DM20 (HMPE)1042353.6
Zylon Type HM (PBO)1948422.5
Zylon Type AS (PBO)1302423.5
Zyex (PEEK)-6.530
Teflon (PTFE)1328.5
Technora (Para-Aramid)590274.5
Twaron (Para-Aramid)600233.6
Vectran (LCP)60025.93.8
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SPECIFIC GRAVITY

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Specific gravity (buoyancy of a rope / material) Specific gravity is a measure of the density of a material; a Specific Gravity of 1.0 is equivalent to a density of 1g per cm3 (i.e. a Specific Gravity <1 means the material floats). The following table shows the specific gravity of some of the materials commonly used in fibre ropes.
MATERIALSPECIFIC GRAVITY
Polypropylene 0.91
HMPE (Dyneema)0.98
Fresh Water1
Salt Water1.03
Nylon1.14
Polyester1.38
Vectran1.41
Aramids (Technora, Twaron, Kevlar, Nomex)1.44
Zylon1.54
Steel7.85
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ULTRA-VIOLET RADIATION RESISTANCE

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All materials are affected by UV radiation to some extent. The actual affect on a rope by UV is very difficult to predict as it is reliant on a number of random factors such as intensity of UV and length of exposure. 

The table on the right attempts simply to rank different materials in line with their resistance to UV radiation on a scale of 1 to 5, with 5 being most resistant to UV and 1 being least resistant.

MATERIALUV RANKING
Polyester5
HMPE (Dyneema)5
Nylon (UV treated)4
Aramids (Technora, Twaron, Kevlar, Nomex)3
Vectran3
Polypropylene2
Zylon1
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MELTING POINT

The table on the left shows the typical melting or decomposition temperature of some common rope making materials. 

MATERIALMELTING POINT (Deg. C)
Zylon650 (Decomposition)
Aramids (Technora, Twaron, Kevlar, Nomex)500 (Decomposition)
Vectrancell
Polyestercell
Nylon (6.6 / 6)250 / 220
Polypropylene170
HMPE (Dyneema)150
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CHEMICAL RESISTANCE

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Exposure to chemicals can have a significant affect on the strength and performance of ropes, depending on the material used in construction.  This table details the residual strength of synthetic fibres after chemical exposure under specific conditions.

Nylon ropes are particularly badly affected by exposure to most acids.  For this reason, Marlow developed a special Halochromic indicating (acid indicating) marker incorporated into to some of our nylon PPE Static Ropes.


TEST CONDITIONS


RESIDUAL STRENGTH

ChemicalConcentration
Chemical / water %
Temperature
Deg. Centigrade
Exposure
Hours
NylonPolyesterPolypropyleneAramidHMPE
Acids







Hydrochloric34%201000%90%100%95%100%
Nitric66%201000%70%100%95%95%
Sulphuric96%201000%100%100%40%90%
Formic90%201000%95%100%90%100%
Acetic100%2010085%95%100%100%100%
Alkalis







Caustic soda40%2010050%0%90%90%100%
Caustic soda20%70150100%0%100%85%90%
Caustic potash20%2010090%0%90%90%100%
Solvents







Trichloroethylene100%30150100%95%80%100%1005
Carbon tetrachloride100%20150100%100%100%98%100%
Benzene100%70150100%100%100%98%95%
Metacresol100%10040%0%100%80%100%
Oxidising agents







Hydrogen peroxide10%201000%100%90%95%100%
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