Dust content

Dust content, despite not being assessed within PN-EN ISO 1279-4:2018 norm is an indispensable parameter that affects usability of selected desiccant in IGU and its price. The dust content greater than 50 ppm (50 mg/kg) is unacceptable because of the possibility of elutration of the smallest particles within IGU space and possibility to settle on the glass panel

Unfortunately, dust content, is not specified in PN-EN ISO 1279-4:2018 norm, however, based on numerous complaints and dialogues with IGU providers, it may significantly decrease the quality of certain desiccant. Small particles of dust, can be elutrated or even deteriorate the filling process, hernce knowing its exact amount (mostly not more than 50 µg/kg = 50 ppm) is profitable from both technical perspecitve and economical point of view. Its content in certain amount of desiccant should be close to the smallest amount or even not appear. In addition high dust content can cause malfunactions of automatic filling machine

AWAC - Available Water Adsorption Capacity

One of the key parameter that ensures there is no condensation within IGU and low humidity environment is sustained during reasonable, economic lifetime. Expressed as the percentage [%] by weight of the mass of the desiccant

Since facilitation of the low humidity and water-vapor free environment within the IGU, the AWAC is the key parameter that describes the perfomance of the selected desiccant which has to be simultaneously effective and selective toward gaseous chemicals that occur in IGU. It is worth to mention, that the stability of the desiccant in the function of time is neglected but indispensible when proper AWAC is to be maintained.

Electrostatic charge

Electrostatic charge is also unspecified parameter in abovemnetioned ISO norm. Nevertheless, presence of electric charge is an effect of the chemical nature of the desiccant raw material. Molecular sieves used for the purpose of manufacturing of the desiccant garunles (mostly zeolites - skeleton aluminosilicates minerals) are composed of tetrahedral building units composed of silicon central atom bonded with oxygen atoms in the nods of the tetredr. Presence of aluminium may trigger heterovalent diadochy*  phenomena, therefore Si4+ cations are replaced by Al3+ cations, which generates negative charge on the surface of the zeolite.

Electric charge is of importance for prospective use of certain desiccant because once attached to positively charged surface it may deteriorate the filling process and spoil the volumetric occupation of the IGU frame.

L.p.

Parameter

Unit

2

AWAC* (Available Water Adsorption Capacity) (EN 1279-4)

[% wt.]

≥15.5

≥20.0

16.5

≥16.5

≥20.0

≥20.0

≥20.2

≥20.0

>21

>20

>19

>20

>20

>17

≥16

4

Dust content

[ppm]**

≤40

≤30

≤25

≤70

≤20

≤20

≤50

n.d.a***

22

<30

<30

<50

≤30

<50

<50

6

Diameter of a single granule

[￠mm]

0.5-1.0

0.5-1.1

0.5-0.9

0.7-0.9

0.5-0.8

0.5-0.7

0.5-1.2

0.5-1.15

1.0-1.68

1.3-1.7

0.5-0.9

0.5-0.9

0.7-1.3

0.5-0.85

0.5-1.25

Phenomenon

Bulk phenomenon

Surface interactions

Temperature impact

Independent of T

Favourable in low T's

Concentration of the chemical indviduum

Uniform throughout the material

Concentration on the surface greatly differs from the one observed in the bulk