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Benefits of the high Reflectivity of Aluminum foil

The Aluminum foil reflects away about 95% of the IR rays incident upon it. Since Aluminum has a low mass to air ratio, very little conduction can take place, particularly when only 5% of the IR rays are absorbed. This is the main reason for having the foil facing the wall where the heat originates primarily. It should be noted that the foil should not come in contact with the inner surface of the wall. Radiation from the inner surface of the wall is minimized by the reflective property of the foil. IR reflectivity is best utilized when the foil and the wall’s inner surface are separated by at-least 0.75 inches or 19 mm. If the foil contacts the inner surface of the wall then heat will conduct from the wall to the foil, which will further conduct it to the foam albeit slower. When the reflective surface of the Aluminum foil is attached to the wall, that particular surface ceases to have radiant insulation value at the points of contact. In both winter and summer, about 75% of the heat passes from the warmer wall to the colder wall by radiation. Placing the Aluminized foam in the wall section with the Aluminum oriented towards the wall with an air space between would retard the heat flow by conduction and convection. Conduction and convection represent about 25% of the heat that passes through them.
ndustries is proud to offer
NITROLITE
a unique closed cell Nitrile foam material designed for both thermal and acoustic insulation and lasting durability. NITROLITE offers superior insulating ability over standard neoprene and other types of closed-cell foams at a much lower price. In addition to wide usage for thermal insulation, the inherent characteristics and physical properties of NITROLITE make it a highly advantageous product in a wide variety of industrial applications.
 
   

 

 

NITROLITE
’s expanded closed cell structure provides an efficient vapor barrier for the prevention of condensation on cooling systems or frost formation on refrigeration lines. It significantly retards heat loss for hot water plumbing and heating, dual temperature piping and solar energy systems.

Benefits of the low emissivity of Aluminum Foil
Of the common materials of construction, Aluminum foil has the lowest emissivity of about 5%. [If 100 units of heat were available in the foil or the source it wraps around the foil would radiate out some 5 units]
The emissivity benefit derived from the Aluminum foil when placed facing the inner surface of the wall is it would retain the heat received by it. The Aluminum foil would radiate out only 5% of it.
This property would be best utilized when the inner surface of the foam that faces the inside of the room is also lined with Aluminum foil.

Benefits of the Aluminum foil as a Convective barrier
Although the Aluminum is a good heat conductor the foil is a good barrier to convective heat transfer. The foil stops about 75% of convective heat when there is an air space of at least 0.75 inches. The low thermal emissivity of the foil and the low thermal conductivity of the air are advantageous in heat gain or loss control.

Other Benefits of Aluminum foil
Aluminum foil, with its reflective surface, can block the flow of radiation. Most Aluminum insulation has only a 5% absorption and emissivity ratio. They are impervious to water vapor and convection currents and reflect away 95% of all radiant energy that strikes its air bound surfaces.

Summary
The foil wrapped foam as it is, when installed in the middle of the wall section with an air space of about 0.75 inch would offer the following benefits:

1] Offers 90% reduction of radiation heat transfer, which is the single largest component of heat flow from the outside when the sun is striking the outer wall surface.

2] Offers about 75% reduction of convection heat transfer which is the second largest component of heat flow from the wall surface.

3] The Aluminum does not contribute much in the way of preventing conduction heat transfer as it is a good conductor, but the LOW thermal conductivity of the NBR-PVC foam retards the flow of conductive heat. Overall the net result of heat flow through all modes of heat flow Aluminum foil wrapped NBR-PVC foam is better than conventional insulation materials by about 50% as it prevents almost all radiation and most of the convection heat transfers.

4] The other inherent properties would include the following:
         
          1. Thermal stability
          2. Good Fire resistance
          3. Low toxicity
          4. Very Low water vapor permeability
          5. Low water absorption
          6. Good mildew resistance
          7. Good weather and ozone resistance
          8. Negligible off gases and odor
          9. Excellent flexibility
          10. Good Sound absorption and acoustic properties
          11. Long Service life
 

Effect of a layer of Aluminum Laminate to the Nitrolite Insulating Material

The Multi layer or Duplex Layer of a highly reflecting material such as Aluminum foil and the low-conductivity Nitrolite™ Foam has very low apparent thermal conductivity in the order or neighborhood of 50 Micro Watts / Meter Kelvin. *
The very low thermal conductivity of multi layer or duplex layer insulations may be attributed to the fact that all modes of heat transfer, CONDUCTIVE, CONVECTIVE & RADIATIVE, are reduced to a bare minimum. Since radiant-heat transfer is inversely proportional to the number of intermediate or terminal reflecting shields, using shield of a low-emissive material minimizes radiation heat absorbing into the insulation. Convection is eliminated or greatly reduced due to the lack of any flow of air currents in the spacing in the bulk of the foam. The low conductivity and discontinuous nature of foam contributes to the solid-to-solid conduction to a minimum.
The Aluminum acts as both a radiation shield and a vapor barrier. As a radiation shield it reflects away heat incident upon the insulation and is very effectively offers resistance to the invasion of moisture, vapor or liquid water. The Aluminum foil provides an effective gas, vapor, liquid and moisture barrier thus preventing degradation of the closed cell foam. The sealed sides of the foam also act as a barrier as the permeability of the NBR-PVC is very low.
* The above statement draws parallel from similar multi-layer insulation studies as stated below. Multi-layer insulation consists of alternative layers of highly reflective material, such as Aluminum or Aluminized Mylar, and a low-Conductivity spacer material or insulator, such as fiberglass mat or glass fabric all under vacuum. When properly applied at the optimum density, this type of insulation can be apparent thermal conductivity of as low as 10 to 50 Micro Watts / Meter Kelvin.

2] The closed cell foam prevents gas or vapor conduction. The large number of air and rubber interfaces increases the resistance to heat transfer. The Aluminum foil reflects away radiated heat thus preventing absorption of heat. The Aluminum foil is a gas and airtight barrier that is required to prevent the rising of the thermal conductivity due to diffusion of air and moisture into the foam. When the temperature is expected to fall below the dew point, this condition would lead to condensation of water vapor within the insulation and result in a substantial decrease in the insulating effectives and life of the foam.

3] The permeance of Water vapor in Aluminum is about 0 in a 1mil thick foil and about 0.05 in a 0.35-mil foil. The permeance figures are dry cup permeance.

4] Chemical Handling Capabilities of NBR-PVC:
In general NBR-PVC synergistically derives the advantages of the two constituents: Acrylonitrile-Butadiene and Poly Vinyl Chloride. The primary of the advantageous Chemical resistances of the constituents are highlighted hereunder.

Acrylonitrile–Butadiene Rubber (NBR) – Oils, Aliphatic Hydrocarbons, Gasoline and Lower alcohols

Poly Vinyl Chloride (PVC) – Alcohols, Acids and Bases.

The composite material, NBR-PVC, can withstand:
Butyl Alcohol
Caustic Soda [Sodium Hydroxide]
Hydrofluoric acid
Hydrochloric acid
Phosphoric Acid
Oil – Mineral and Vegetable
Hydrocarbons – Aliphatic & Aromatic
Hydrogen Peroxide
Potassium Hydroxide
 

Chromic Acid                         
Citric Acid                               
Formic Acid                            
Hydrochloric Acid                  
Hydrofluoric Acid                   
Nitric Acid                                
Phosphoric Acid                    
Sulfuric Acid                            
Aluminum Chloride
Ammonia Aqueous
Ethanol
Glycerin
Hydrogen Peroxide
Methanol
Sodium Chloride  [marine environment]
Sodium Hydroxide
10% up to 150 D
40% up to 150 D
50% up to 100 D
10% up to 150 D
12 % up to 75 D
12 % up to 50 D
50% up to 150 D
30% up to 125 D
50% up to 150 D
25% up to 125 D F
100% up to 75 D F
100% up to 150 D F
25% up to 100 D F
100% up to 125 D F
40% up to 150 D F
50% up to 125 D F

5] Mechanical Properties:

A) Hardness Average Shore Hardness: 30º to 45º
B) Hardness 60+/-5 IRHD per ASTM D-1415. [From SAAB Literature]*
C) Tensile Strength Min 7 MPa ASTM D 412 [From SAAB Literature]*
D) Max. Temperature 116º C @ 100º C @Average Density 85 Kg/m3 90 Kg ~ 145 Kg/m3 Per Standard BS 476 Pt 7 Class 1 ASTM D 1056/85/2B1
[The lower the Density the higher the maximum temperature: i.e. @ 85 Kg/m3 the Max. Temperature is 116º C.]

6] Functional Uses: Gaskets, Seals, Oil seals, Cushioning, Vibration dampening, Packaging, Oil resistant parts and tubes, Weather resistant parts, Shock Absorption and Insulating material.

 
Aluminum Laminate
wrapped around a cold water holding tank.
Aluminum Laminate
being installed on cold water storage tanks
Air Duct Wrapped in ¼” Aluminum Laminate to Regulate Air Temp for Farm-Wide Distribution
   
     
 
 

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