Weft Knitted Fabrics Test by Sweating Guarded Hotplate

Sweating guarded hotplate is a proven and trusted thermal and vapor characteristics device. Here we will analyze its application in testing weft knitted fabrics.

1. Moisture conductivity

Moisture conductivity means fabric conducting liquid water ability and it depends on fabric absorption ability to water. Wicking means fabric flowing freely under the pressure from liquid-gas interface in capillaries. The better vapor permeability fabrics have, the easier sweat discharges, therefore human surface temperature reduces and people will feel comfortable.

1.1 Test objects

8.3 tex/48f (75D/48f) wicking PTT, 8.3 tex/48f wicking PET

1.2 Test specification

Sample size 300*25mm, wicking time is 30s.

 

Swearting guarded hotplate

2. Moisture permeability

Moisture permeability means vapor going through fabrics ability. Human body moisture mainly comes from perspiration evaporation; Gaseous sweat spreads out through fiber absorption-dismiss moisture and voids, thus moisture permeability is an important feature to measure fabric swearing guarded ability.

2.1 Test objects

NO.1   8.3tes/48f PTT (four groove deformed section)

No.2   8.3 tex/48 f PET (four groove deformed section)

No.3   8.3 tex/48 f PET plus 8.3tex (four groove deformed section)

No.4   8.3 tex/72 f PET water Hydrophilic agent process

2.2 Tester

YG601 computer moisture permeability tester

2.3 Test specification

Oven temperature 160℃, moisture permeability chamber temperature 38 ℃, humidity 90%, Hygroscopic agent Anhydrous calcium chloride

2.4 Test result

NO.1  6 043 g/m2•d

NO.2  5 715 g/m2•d

NO.3  5 611 g/m2•d

NO.4  5 304 g/m2•d

 

PET fabrics for sweating guarded hotplate

 

PTT fabric for sweating guarded hotplte

Conclusion

From the test data, we come to conclusion that PTT fabric is better than PET fabric due to their different regain of 1.22% and 0.4% respectively. The large regain ensures stronger Hydrophilic capacity. In terms of fiber structure, PTT fiber has loose molecular structure and the crystallinity is less than 50% while PET is more than 80%.

From NO.3 and NO.4 data, we can tell that samples with deformed section are superior to those with water hydrophilic agent process. Deformed section increases fiber gaps and moisture absorption ability; besides, it has bigger surface for more water absorption.

Water Hydrophilic agent increases moisture absorption ability, but has poor effect because it can only change fabric superficial features rather than its inner structure ( like thickness and porosity).

PTT deformed section fabrics have better moisture permeability than PET fabrics, thus they are ideal moisture wicking polyester materials for sweating guarded hotplate testing and will have further application in textile industry.

For more professional information on sweating guarded hotplate or textile testing instruments, please contact QINSUN Instruments.

Get to Know Sweating Guarded HotplateTesting Materials

Sweating Guarded Hotplate Testing Materials

There are 3 ways for moisture penetrating fabrics:

1. Vapor spreads through fabric microporous;

2. Fiber absorbs moisture and flows out from the place where water pressure is lower;

3. Large amount of water molecule creates dew and spreads through capillary and evaporates at a place where water pressure is lower. 

                                             
                                                    Sweating Guarded Hotplate test materials

The Vapor amount generated from absorption, transfer and flowing out is related to fiber, moisture absorption amount, expansion degree, fiber pores and channels.

The textile products of sweating guarded hotplate test should be water absorption and quicksetness. Polyester has high crystallinity molecular chain structure, thus ensures polyester these features such as small amount of water absorption and bad air permeability which stands out definitely in the feature of quicksetness. Natural fiber like cotton is endowed with many holes which make it good at water absorption, but the expansion results in water gripping and poor quicksetness.

Generally speaking, hydroscopic and sweat fiber tested for sweating guarded hotplate uses capillarity generated from fine groove to make sweat volatilized quickly. For more sweating guarded hotplate test and textile testing instruments, contact QINSUN Instruments.

Sweating Guarded Hotplate Operation

Heating and damp comfort are human’s higher requirements on fabrics except their basic use of covering, keeping warm and cold-proof, thus these two features are more important factors to measure fabrics comfort. Heating resistance stands for fabric heating transforming features thus the bigger heating resistance is, the more cold-proof. While in summer, we tend to choose clothes with smaller damp resistance which can disperse moisture in our body and make people feel dry and comfortable.

Here we will introduce you the sweating guarded hotplate operating method.

1. Before starting, check the water level in constant temperature and humidity tank if there is enough water, since it won’t work even started without enough water.

Fill water in this way: open the front door, unscrew the left stainless steel cover and take the funnel to add water for adjusting moisture; stop adding at the water lever line.

2. After starting the switch, the setting panel displays for setting the temperature and moisture in climatic chamber. Heating resistance requires the temperature should be 20℃ and the moisture be 65%; while damp resistance requires the temperature be 35℃ and moisture be 40%.

3. Sweating Guarded Hotplate Heating Resistance Test

(1) The test sequence is: preheating--setting heat resistance specifications--heat resistance empty panel test--heat resistance test

(2) Preheating:  start the switch and preheat for 45 minutes; add a block of medium thickness fabric on testing board and take it out when the board is 35 ℃. Watch the heating board and floor board temperature reaching 35.2℃, We finish preheating and put the samples on test platform.

(3) Heating resistance specifications set: refer to the standards.

(4) Heat resistance empty panel test: test heat resistance when there are no samples. There is no need to do the empty panel test since it has quite small mistakes and we suggest do it every 3-6 month.

(5) Heat resistance test: put the sample on test board surface and adjust the lift button in the front of test stand; Cover the metal as blanket in four sides; When metal blanket is horizontal, put down organic glass cover and close tester door. Press start button and the tester runs; Press stop button after it runs stably and tester remain displays heat resistance results.

(6) Change samples and repeat the above process. Use the average data for evaluating and keep them 3 valid digits. 

4. Sweating Guarded Hotplate Damp Resistance Test

(1) Test sequences: Preheating—damp resistance specifications set—supply water and put test film—damp resistance empty plate test—damp resistance test

(2) Preheating: start the switch and preheat for 60 minutes; add a block of medium thickness fabric on testing board and take it out when the board is 35 ℃. Watch the heating board and floor board temperature reaching 35.2℃, we finish preheating and put the samples on test platform.

(3) Supplying water and putting test film belong to damp resistance test. Press the damp resistance button and loosen waterproof connector, water can flow to test tank from inside of the water supplement chamber. Watch water indicator on the right of test stand and the surface of perforated plate; tighten waterproof connector when the water flows out.

(4) Take out 2 films and use the flexible side; pave them to the perforated plate and add distilled water properly. Use cotton blocks to pave films and remove bubbles between films and perforated plate.

For more information on sweating guarded hotplate or textile testing instruments, you can visit our website www.qinsun-lab.com .

How to Calculate Sweating Guarded Hotplate Testing Result

Sweating guarded hotplate testing result calculation formula:

Thermal Resistance:  Rct = (Tm-Ta) .A / (H- Hc) - Rct0

Dampness:  Ret = (Ps-Pa) .A / (H- He) - Ret0

If necessary, you can calculate other parameters according to the following formula:

Insulation rate: Wr = (1-b / a)%

ASTM F 1868A Rcf = Rct-Rcpb

ASTM F 1868B Ref = Ret-Repb

Breathable index: im = 0.060 Rcf / Ref

Water vapor transmission rate: Wd = 1 / Ret.ΦTm

When Tm = 35 ℃ when, ΦTm = 0.627W.h / g.

Crow value: clo = Rct /0.155 = 6.451 Rct

Thermal conductivity: k = 10-5.d / Rct

Wherein d is the thickness of the material (mm)

                                                        sweating guarded hotplate

Other related symbols and is defined as:

Rct resistance, m2.K / W

Ret dampness, m2.Pa / W

imt breathable index, dimensionless

Rct0 for the determination of the thermal resistance Rct determined instrument constant, m2.K / W

Ret0 for the determination of moisture resistance Ret determined instrument constant, m2.Pa / W

Rcpb bare-board thermal resistance, with Rct0

Repb bare board dampness, with Ret0

Wd water vapor transmission rate, g / m2hPa

ΦTm test plate surface temperature of saturated steam latent heat Tm when, Wh / g

A test board area, m2 sweating guardedhotplate formula

Ta climate chamber air temperature, ℃

Temperature Tm test plate, ℃

Ts hot grommet temperature, ℃

Pa water vapor pressure (in a climate chamber when the temperature Ta), Pa

Pm saturated water vapor pressure (when the surface temperature of the test plate when Tm), Pa

va test sample over the surface of the air velocity, m / s

sv standard deviation of flow velocity va, m / s

Relative humidity R.H.,%

H provided to the test panel heating power, W

                                                     sweating guarded hotplate testing

△ Hc measurement of thermal resistance Rct heating correction amount of power

△ He dampness Ret correction amount determination heated power

α △ Hc calculation of the amount of slope correction

β △ He corrected the calculation of the amount of slope

k Thermal conductivity, W / m.K

d material thickness, mm

Wr Insulation rate

plus a empty plate heat (J / Cm2.S)

b have the test sample plus heat (J / Cm2.S)

clo CLO value, the thermal resistance of a representation unit. At a temperature of 21 ° C, the air flow does not exceed 0.1m / s environmental conditions, meditation (whose basal metabolism of 58 W / m2) feel comfortable when they wear clothing insulation value of 1 Crow (clo) value.

For more professional textile testing instruments infomation, please visit QINSUN Instruements Co., Ltd.