Modek GRP Technical Product Data

GENERAL

Translucent fibreglass roof sheets were first manufactured in South Africa in 1959. Today MODEK manufactures GRP roof sheets on an automated continuous line laminating machine using a thermosetting process.

This ensures consistently high product quality in successive consignments, and allows for any transportable length of sheet to be made.

MODEK GRP sheeting is manufactured using UV stabilised unsaturated polyester resin and glass fibre reinforcement material. The weathering surface is covered with a highly UV stabilised gelcoat layer. This new generation technology offers superior weathering characteristics to conventional methods of surface protection in the GRP sheeting industry.

All MODEK GRP products are specifically designed to withstand the harsh South African climatic conditions and gelcoated products carry the SABS 1150/1984 mark of approval.

A range of colours is manufactured, with the standards being clear, white (opal 50), green and blue, and certain domestic products are also made in biscuit, linen and a colourful range of stripes.

All the generally used profile shapes, to match those of other non-translucent roofing and cladding sheets, are manufactured and supplied by MODEK in any transportable length.

MODEK'S Technical Department can manufacture almost any new profile provided that the nominal dimensions can be accommodated in our plant



MASS - MODEK GRP

The internationally accepted unit of measurement (as used by MODEK) for GRP sheeting is a nominal weight per area. In South Africa the metric unit used is:

Kilograms per square metre of product (kg / m2).

In imperial measurements, (e.g. USA) the unit used is grams per square foot of product.

Nominal thickness of profiled GRP roof sheeting should not be used, as this measurement will vary slightly from profile to profile when a uniform production weight is used. All continuous line laminating plants in the world manufacture to a mass or weight parameter, and not thickness.

The three weights available are as follows
LIGHT INDUSTRIAL


STANDARD INDUSTRIAL :


HEAVY INDUSTRIAL :

1.4 kg / m2


1.8 kg / m2


2.4 kg / m2


1.4 and 1.8 kg / m2 sheets satisfy most industrial applications in South Africa. Where a special or unusual application applies, or if any doubt exists, MODEK's Technical Department should be consulted.

2.4 kg / m2 (heavy industrial sheeting) is generally recommended where:

  • The length of sheet exceeds 9.0 metres.
  • Excessive wind loading will be experienced.
  • Excessive water loading is likely to be encountered.
  • Additional strength could be advantageous e.g. in a known hail belt.

MODEK's domestic range of products is manufactured between 1.0 kg / m2 and 1.4 kg / m2. These are designed to suit less aggressive conditions than those encountered in industrial applications.

Other weights can be manufactured to specification depending on particular requirements. Refer to MODEK's Technical Department.


LIGHT AND SOLAR ENERGY TRANSMISSION - MODEK GRP

Different translucent roof sheeting applications could call for varying levels of light transmission. With different colours these levels change.

Not only does the natural (or visible) light level vary, but the amount of solar energy (heat) also varies.

The diagram below depicts the approximate transmission of the various wavelengths of the light spectrum for a clear GRP sheet.



More than 70 % of the heating effect of the sun is carried between 350 and 800 nanometres (generally, the visible light spectrum) and we can see that these wavelengths are generously transmitted through a clear MODEK GRP sheet - more than 80 %.

Why does heat build up in a room?

As illustrated, a high percentage of the visible short wave radiation has been transmitted through a MODEK clear sheet.

This radiation is absorbed by surfaces inside the room, and these surfaces become heat radiators. The heat emitted from these "radiators" is long wave radiation which is not so readily transmitted out of the room through the MODEK sheet. The result is that the trapped heat builds up in the room. This is also known as the "greenhouse effect".

An effective method of combating heat build-up in a room is to have good through ventilation. This can also be improved by selecting the most appropriate MODEK GRP roof sheet.


The table below shows the various percentages of transmitted light and solar energy, and also that amount of light and solar energy which is reflected and absorbed by the different coloured MODEK sheets.

ColorQUEST Colorimeter Test Results
MODEK GRP Translucent Roof Sheets


MODEK GRP ROOF SHEET TINT

 CLEAR

 BLUE

 GREEN

 OPAL 50
 
VISIBLE SPECTRUM (380 nm - 700 nm)
     % Light Transmission

 85

 40

 50

 50
     % Light Reflectance

 15

 8

 10

 48
 
SOLAR ENERGY (350 nm - 2100 nm)
     % Rejected

 16

 40

 34

 42
     % Direct Transmission

 83

 47

 57

 57
     % Direct Reflectance

 12

 7

 8

 39
     % Absorption

 5

 46

 35

 4
     % Total Transmission

 84

 60

 66

 58
 
SHADING COEFFICIENT

 0.97

 0.69

 0.76

 0.67


Notes:

  • Shading coefficients are used for comparing solar heat transmission properties of different glazing materials to that of clear float glass 3 mm to 4 mm thick, the glass being given a value of 1. To be used for comparative purposes only.
  • For practical purposes, MODEK GRP sheets do not transmit harmful UV rays.
  • MODEK GRP roof sheets are manufactured with randomly dispersed fibreglass reinforcement material. This results in a very good diffusion of natural light, thereby substantially reducing the amount of glare inside the building. This, in turn, means a more comfortable working environment.

Should there be any further requirements regarding the light and solar energy transmission of MODEK GRP roof sheets, contact the Technical Department.


MODEK 030 - MODEK GRP

MODEK has developed a specific product in GRP profile sheeting designed to offer the optimum combination of maximum light transmission with minimal transmission of solar energy.

The following graph indicates the performance characteristics of a MODEK 030 roof sheet as compared to that of a conventional clear MODEK sheet.



Considerably less solar energy is transmitted, which reduces the greenhouse effect within the building.

This heat protection characteristic of MODEK 030 sheets is useful when it is necessary to provide natural light without heat, such as in supermarkets, public walkways, food storage areas, and so on.

All the physical properties, and price, remain the same as the other MODEK GRP sheets, and can be specified in any industrial profile.


WEATHERABILITY - MODEK GRP

New generation UV stabilised unsaturated polyester resins are used in the manufacture of MODEK GRP sheets by means of a thermosetting process.

A gelcoat layer, consisting of extremely high grade isophthalic neopentyl glycol polyester resin, is chemically bonded to the weathering surface of all SABS 1150/1984 grade sheets. This technology was developed in the USA and is licensed to MODEK, South Africa.

Extensive weathering tests have been done, proving that, because of the gelcoat layer, no fibres become exposed during the normal lifespan of the sheet, and the layer of gelcoat cannot peel off.

The end result is a high-gloss surface providing a tried and tested method of protection against damage from exposure to the weather, UV, chemical attack, corrosion and surface abrasion.

GRP, as with almost all plastics, will be adversely affected by UV attack, over a period of time. This is called photodegradation.

What occurs during this process is the following:

The aggressive short wave length UV rays are absorbed into the polyester resin. They "excite" the chemical molecular bonds of the polymers, causing them to separate, resulting in a yellowing of the sheet.

This process is radically slowed down in a MODEK GRP sheet because of the presence of UV stabilisers and the excellent surface protection afforded by the gelcoat surface treatment which also incorporates UV absorbers.

The noticeable change in a MODEK GRP sheet, after a prolonged period of outdoor exposure, will be a slight yellowing, and the following light transmission levels can be expected :

SABS 1150/1984 3.9.(c) "after the sheet has been subjected to outdoor exposure for 5 years (see 5.5) at least 85 % of the value (light transmission) obtained before exposure, should be retained.”

There will be virtually no change to the physical properties over this period, and, under normal conditions, a MODEK GRP gelcoated sheet will remain structurally sound for more than 20 years.


CORROSION AND CHEMICAL RESISTANCE - MODEK GRP

Standard MODEK GRP sheets will resist chemical attack in most usual industrial and marine environments.

Extensive laboratory research has been carried out on the resistance of MODEK GRP sheets to various chemicals encountered in the industrial environment.



The following table gives an indication of the performance of a MODEK GRP sheet in the presence of a range of chemicals / chemical solutions and gases. These results are based on the MODEK GRP sheet being totally immersed in the relevant agent.  In roofing applications, the actual exposure to the listed aggressive elements would probably be less. Should there be a need to assess the performance of MODEK GRP sheeting in a known aggressive environment, please contact the Modek Technical Department.
CHEMICAL RESISTANCE OF MODEK GRP SHEETING
Immersion at Ambient Temperature (up to 30°C)

CHEMICAL ENVIRONMENT

RECCOMENDATIONS FOR EXPOSURE
Sulphuric Acid 3 %

 B
Sulphuric Acid 30 %

 D
Nitric Acid 10 %

 D
Hydrochloric Acid 10 %

 B
Sodium Hydroxide 1 %

 D
Sodium Hydroxide 10 %

 D
Acetic Acid 5 %

 B
Sodium Carbonate 25 %

 D
Isopropyl Alcohol 50 %

 D
Isopropyl Alcohol 99 %

 D
Hydrogen Peroxide

 D
Citric Acid 10 %

 B
Sodium Chloride 10 %

 B
Distilled Water

 B
Carbon Tetrachloride

 D
Cutting Oil (commercial grade)

 A
Toluene

 D
Chlorine (Gas)

 D
n-Heptane

 D
Oleic Acid CP

 B
Phenol Solution 5 %

 D
Ethyl Acetate

 D
Ammonium Hydroxide 5 %

 D
Ammonia (Dry gas)

 D
Ethylene Dichloride

 D
Urea

 D
   
A - Recommended for continuous exposure.
B - Recommended for intermittent or limited period of exposure.
C - Not recommended for prolonged exposure or immersion.
D - Not recommended.
Notes:

  • Special chemical resistant properties can be built into MODEK GRP sheets once the chemical atmosphere is known.
  • There is no known chemical reaction with any other recognised construction material.

 

ISOPHTHALIC SHEETING

The industrial cladding industry is seriously challenged by high levels of chemical fallout, acid rain and other aggressive environments.  These conditions result in premature degradation of commonly used metal cladding systems.  The frequent maintenance requirements resulting from this type of corrosion can become expensive.

MODEK offers the GRP solution to these problems in the form of an OPAQUE GRP sheet, manufactured from the highest grade of ISOPHTHALIC chemically resistant polyester resin.  These sheets can be tinted to match the most commonly used cladding colours.

For even more aggressive environments, MODEK can offer the neopentyl glycol isophthalic option, which has been designed specifically for the most chemically aggressive environments found in modern industrial developments. 

The following industries are typical of those which should consider the isophthalic option: 

  • Reduction works
  • Battery manufacturing
  • Galvanising plants
  • Refineries
  • Salt laden environments (e.g. salt works)
  • Potash mines
  • Poultry farming
  • Fertiliser plants
    CHEMICAL RESISTANCE OF MODEK ISOPHTHALIC SHEETS

    (at temperatures up to 30°C)
    CHEMICAL ENVIRONMENT

    ISOPHTHALIC (ISO)
    NEOPENTYL GLYCOL ISOPHTHALIC (NPG/ISO)
    Sulphuric Acid 3 %

    		 A

    		 A
    Sulphuric Acid 30 %

    		 A

    		 A
    Nitric Acid 10 %

    		 A

    		 A
    Hydrochloric Acid 10 %

    		 A

    		 A
    Sodium Hydroxide 1 %

    		 D

    		 A
    Sodium Hydroxide 10 %

    		 D

    		 A
    Acetic Acid 5 %

    		 A

    		 A
    Sodium Carbonate 25 %

    		 D

    		 A
    Isopropyl Alcohol 50 %

    		 A

    		 A
    Isopropyl Alcohol 99 %

    		 A

    		 A
    Hydrogen Peroxide

    		 D

    		 A
    Citric acid 10 %

    		 A

    		 A
    Sodium Chloride 10 %

    		 A

    		 A
    Distilled Water

    		 A

    		 A
    Carbon Tetrachloride

    		 D

    		 D
    Cutting Oil (commercial grade)

    		 A

    		 A
    Toluene

    		 D

    		 D
    Chlorine (Gas)

    		 D

    		 A
    n-Heptane

    		 A

    		 A
    Oleic Acid CP

    		 A

    		 A
    Phenol Solution 5 %

    		 D

    		 E
    Ethyl Acetate

    		 D

    		 D
    Ammonium Hydroxide 5 %

    		 D

    		 A
    Ammonia (Dry gas)

    		 D

    		 A
    Ethylene Dichloride

    		 D

    		 D
    Urea

    		 A

    		A

     A         -       Recommended for continuous exposure

    B         -       Recommended for intermittent or limited period of exposure

    C         -       Not recommended for prolonged exposure or immersion

    D         -       Not recommended

    E         -       No data

     

    Please contact Modek’s Technical Department for any requirements not covered in this table.



    PHYSICAL AND MECHANICAL PROPERTIES - MODEK GRP
    Tensile Strength

    		 72 MPa (minimum) - SABS 1150/1984
    Flexural Strength

    		 140 MPa (minimum) - SABS 1150/1984
    Shear Strength

    		 70 MPa (minimum) - SABS 1150/1984

    Modulus in Flexure

    		 3 000 MPa (minimum) - SABS 1150/1984
    Thermal Movement

    		 Coefficient of linear thermal expansion (clear) 24 x 10-6m/¨C. ASTM D-696
    Water Absorption (in situ)

    		 0.3 % by mass after 24 hours at 20¨C. ASTM D-570
    Hardness

    		 Over 40 Barcol.
    Operating Temperature

    		 Temperature range over which sheets may be used in construction is from - 20¨C to + 80¨C.
    Sheets do not become brittle at low temperatures and are unaffected by frost.

    Thermal Conductivity

    		 Clear 0.145 W/mK. ASTM C-177
    Diffused Light

    		 The diffusion is achieved through the inclusion of randomly dispersed fibreglass reinforcement material in the sheet.
    Scratch Resistance

    		 Highly scratch resistant and therefore easily handled on site.
    Profile Variety

    		 GRP sheets can be manufactured to match almost any profile. A wide range of standard roof sheet profiles is available.
    U.V. Light Opaque

    		 Protecting furnishings, materials and people from harmful U.V. radiation.


    DIMENSIONS

    The following extract from SABS 1150/1984 describes the dimensional tolerances applicable to MODEK GRP sheets:
    3.8.1

    		General. The nominal dimensions of a sheet shall be as specified by the purchaser.

    3.8.2

    		Length. The actual length of a sheet, determined in accordance with 5.7.1, shall be at least equal to the nominal length, and shall not exceed it by more than 20 mm.

    3.8.3

    		Width. The actual width of a sheet, determined in accordance with 5.7.1, shall be at least equal to the nominal width, and shall not exceed it by more than 15 mm.

    3.8.4

    		Rectangularity. Any deviation from squareness, determined in accordance with 5.7.2, shall not exceed 10 mm.

    3.8.5

    		Edge Trueness. When a sheet is tested in accordance with 5.7.3, any departure of any edge of the sheet from a straight line shall not exceed 15 mm.



    MODEK's Technical Department is always available to discuss any specification which calls for applications of translucent sheeting outside the normal parameters.




    MODEK GRP PROFILES

    Industrial Fibreglass Profiles

    Domestic Fibreglass Profiles

    Notes:

    • All industrial sheets have gelcoat surface protection on weather side and are manufactured to the SABS 1150/1984 specification.
    • All domestic sheets have resin rich surface protection on weather side.
    • All dimensions are nominal.
    • A wide range of other profiles is available, subject to order quantity.