Introduction of Coating Viscosity Testing Methods, Standards and Viscosity Testing Instruments

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Viscosity is a measure of the resistance one part of a liquid experiences when it moves over another part of the liquid, and is a property of a fluid that impedes its relative flow. In coatings, except for powder coatings, other coatings are relatively viscous liquids. Viscosity is an important technical index of paint products. In the process of paint production, the relative molecular weight of high polymers in the paint base can be controlled by measuring viscosity; viscosity is also an important process parameter in paint construction. In the coating construction such as spraying, dipping, etc., by adjusting the viscosity of the coating, the thickness of the coating can be controlled, and the appearance of the coating can be improved to a certain extent. The unit of viscosity is Pascal· second (Pa·s), that is, [dynamic] viscosity, indicating the magnitude of internal friction when the liquid flows; when using the so-called kinematic viscometer (such as small hole and bubble type viscometer ) When measuring viscosity or in order to design pipeline devices for conveying paint or paint, it is necessary to introduce the concept of kinematic viscosity. Kinematic viscosity is defined as the ratio of the (dynamic) viscosity of a liquid to the density of the liquid, which can be expressed by the following formula:


ν=η/ρ

Among them: ν means kinematic viscosity; η means dynamic viscosity; ρ means liquid density

Introduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 1

For paint production and painting construction, using a paint cup and falling ball viscometer to test its conditional viscosity is a simple and easy method to control process parameters. The conditions for measuring viscosity with a paint cup refer to the time for a certain amount of sample to flow out of a hole with a specified diameter at a certain temperature, expressed in seconds (s). Domestic paint cups are divided into two specifications: TU-1 cup and TU-4 cup. The outflow time of the test can be converted into kinematic viscosity value (mm2/s) according to the following formula: 

Tu-1 cup: t = 0.053v+ 1.0

Tu-4 cup: t 60; t = 0.154V + 11 23s≤60 at 235; t = 0.223v+ 6.0 at t 150s 

Where t-outflow time (s); v-kinematic viscosity (m2/s).


The conditional viscosity measured with a falling ball viscometer is: at a certain temperature, the time required for a steel ball of a certain specification to pass through the upper and lower scale lines of the glass tube containing the sample, so the measured sample should be transparent of. In addition, there is also a kind of bubble viscometer or Gardner tube commonly used in the industry, which is mainly used for intermediate control of the production process and to measure the viscosity of semi-finished products such as paint and resin liquid.

    Foreign countries usually use the method of measuring conditional viscosity to control coating production and coating construction, such as the international standard (ISO) viscosity cup (the domestic equivalent standard GB6753. 4-1986), the British standard (BS) No. 4 cup, the French standard (NFT) No. 4 cup, American (ASTM) standard Ford cup, German standard (DIN) 4mm cup, German standard (DIN) 6mm cup, etc. Bubble viscometer can be used to measure the viscosity of varnish. This section will introduce the test methods of Tu-1 Viscometer, Tu-4 Viscometer, Falling Ball Viscometer, Ford Cup and Bubble Viscometer.

Tu-1 viscometer method

It is used to measure the paint products whose outflow time is not less than 20s (based on this viscometer).

 l) InstrumentIntroduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 2 The instrument is shown in Figure 4.1-1. The upper part is cylindrical and the lower part is a conical  metal container . One hole is used for plugging rods, the other hole is used for inserting thermometers, the container is fixed in a circular water bath, and the viscometer is installed on a frame with two adjusting level screws. Basic dimensions: the inner diameter of the cylinder is Introduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 3, the height of the cone from the bottom to the scribe line Introduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 4, and the angle inside the cone of the viscometer is Introduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 5. Nozzle height Introduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 6, Nozzle diameterIntroduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 7


2 )测试方法  每次测试前须用纱布蘸溶剂将粘度计内部擦试干净,在空气中干燥或用冷风吹干,对光观察粘度计漏嘴应清洁,然后将粘度计置于水浴套内,插人塞棒。将试样搅拌均匀,有结皮和颗粒时用孔径为Introduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 8的金属筛过滤,调整温度至Introduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 9; 或Introduction of coating viscosity testing methods, standards and viscosity testing equipment with Figure 10;, 然后将试样倒入粘度计内,调节水平螺钉使液面与刻线刚好重合,为使试样中气泡逸出应静置片刻,盖上盖子并插人温度计,试样保持在Paint viscosity testing methods, standards and viscosity testing equipment introduction with Figure 11。在粘度计漏嘴下面放置一个50mL 量杯,当试样温度符合要求后,迅速将塞棒提起,试样从漏嘴流出并滴人杯底时,立即开动秒表。当杯内试样达到50mL 刻度线时,立即停止秒表,试样流人杯内50mL 所需时间(s ) ,即为试样的流出时间,两次测定值之差不应大于平均值的3 %。


涂-4 粘度计法    

       此粘度检测方法用于测定流出时间在150s以下(以本粘度计为标准)的涂料产品。

 l )仪器该仪器见图4.1-2 ,上部为圆柱形,下部为圆锥形,在锥形底部有可以更换的漏嘴,在容器上部有凹槽,作多余试样溢出用。粘度计装置于带有两个调节水平螺钉的架上。涂-4 粘度计有塑料制与金属制两种,其内壁粗糙度为Ra0.4μm但以金属粘度计为准。基本尺寸: 

Introduction of coating viscosity testing methods, standards and viscosity testing equipment with Figure 12

图4.1-1 涂-1 粘度计                                                                     

图4.1-2 涂-4 粘度计


 粘度计容量为Introduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 13,漏嘴是用不锈钢制成的,其孔高Introduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 14,孔内径Introduction of coating viscosity testing methods, standards and viscosity testing equipment with Figure 15 ,粘度计锥体内部的角度为81°±15′,总高度72.5mm,圆柱体内径Paint viscosity testing methods, standards and viscosity testing equipment introduction with Figure 16

 2 )测试方法  粘度计的清洁处理及试样准备同涂-1 粘度计测试法,调整水平螺钉,使粘度计处于水平位置,在粘度计漏嘴下面放置150mm的搪瓷杯,用手堵住漏嘴孔,将试样倒满粘度计中,用玻璃棒将气泡和多余的试样刮人凹槽,然后松开手指,使试样流出,同时立即开动秒表,当试样流液(丝)刚中断时停止秒表,试样从粘度计流出的全部时间( s ) ,即为试样的条件粘度。两次测定值之差不应大于平均值的3 % ,测试时试样温度为(25±l ) ℃ 或(23±l ) ℃。

落球粘度计法

     此粘度检测方法用于测定粘度较高的透明的涂料产品。

  l )仪器见图4.1-3 。由玻璃管与钢球组成,玻璃管长350mm,内径为(25±0.25 )mm;距两端管口边缘50mm处各有一刻度线,两线间距为250mm,在管口上、下端有软木塞子,上端之软木塞中间有一铁钉,管垂直固定在架上(以铅锤测定),钢球直径为(8±0.03)mm,重2.091g。

2 )测试方法  将透明的试样倒人管中,使试样高于刻度线4cm ,钢球也一同放人,塞上带铁钉的软木塞,用长久磁铁放置在带铁钉的软木塞上,将管子颠倒使铁钉吸住钢球,再翻转过来,固定在架上,并用铅锤调节使其垂直,然后移去长久磁铁,使钢球自由落下,当钢球通过上刻度线时立即开动秒表,至钢球落到下刻度线时停止秒表,记下钢球通过两刻度线的时间(s ) ,即为试样的条件粘度。两次测定值之差不应大于平均值的3 %。

福特杯法

此粘度检测方法适用于用福特型粘度杯测量色漆、清漆和有关流体物料的粘度,系选用组合杯口(福特2 号、3 号或4 号)测定在20-100s内的流出时间。

 1 )仪器

福特杯由耐腐蚀、耐溶剂的材料制成,按图4.1-4 中所表示的尺寸要求,装成一个整体。

Introduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 17


2 )测试方法  每次测试前后,均要用适当的溶剂和软毛刷清洗杯子,决不能用金属清洗Introduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 18

工具与仪器相接触,在清洗漏嘴孔时需要特别细心清洗,以避免任何膜沉积在内壁上或造成内壁刻痕。
    应在无通风和无温度急剧变化的房间内进行测试,为了达到高的精确度,室温应在20-30℃, 测定时的温度应在仪器周围大气的露点以上,试样温度应为(25±0.1 )℃。对于流出时间在20-100s之间的物料宜选用福特3 号杯和福特4 号杯,流出时间在40-100s之间的物料宜选用福特2 号杯。 调节仪器使其处于水平位置,用手指堵住漏嘴孔,将事先搅拌均匀、且无任何异物或气泡的物料倒入杯内,更好是使其过量,然后用直尺刮平多余部分,松开手指,按动秒表,测量物料开始流出到流液(丝)第一次中断的时间,所得秒数即为该物料的粘度。




气泡计时法

此粘度检测方法适用于以气泡的秒数计时或对比的方法测定没有晶体或胶体颗粒的透明液体的粘度。对于大多数液体而言,气泡秒数与其斯数 (运动粘度单位)近似相等。lSt =10-4 m2/s 。

1 )仪器

恒温浴任何能保持温度在(25±0.1)℃,以水为介质的浴器均适用。
    a .标准粘度管  内径为(10.65 ±O.025 )mm, 外部长度为(114±l )mm的平底透明玻璃管。应自管底向上在(27±0. 5 )mm、(100 ±0.5)mm、(l08±0.5) mm 处刻有明显的标准线。第一、二两条标线间的距离应为(73±0.5 )mm。
    b .参考标准  为一组标准粘度管,管中充满预先测知以斯和泡秒数表示粘度的透明液体,并按递增26 %的对数列人表4.1-2 ( log1 . 260 = 0.100) ,这些标准应按表4.1-2 所示作出与斯或气泡时间无关的数字标记。在表4.1-2 中还列有长系列的加德纳-霍尔德( Gordner -Holdt )字母标准,仅供一般和历史性资料使用。加氏管没有标准粘度管上的三条标线,而且比标准粘度管短。为方便起见,参考标准可分为三个系列,从0.22-8.0 的15根管为稀薄系列,从10 到200 的14 根管为高粘度系列,从250 到1000 的7 根管为超高粘度系列。计时装置能够精确读到0.1s的秒表或电子闹钟。
    c .管架  能够倒转1 个或多个粘度管180°,精确至1°的直立活动架,并能使管浸人恒温浴中。粘度管软木塞-NO.2 短塞。


 2 )测试方法

装待测粘度的材料于标准粘度管中,约至其108mm标线处。移粘度管到25℃的恒温浴内,并用软木塞轻轻塞住粘度管,在该温度下保温10min。控制恒温浴的温度很重要,恒温浴的温度变化0.1℃,将会引起气泡全程计时1 %的变化。过10min 后,调整液位以使其弯月面底部在100mm线上,塞紧塞子,使塞子的底面在108mm线上,这将保证气泡稳定和大小合适。将粘度管插人管架,并将该管架浸人25℃水浴中。如果用对比法测定,则将适当的标准管挨着待试验的粘度管插人管架。在读粘度值之前,应将带软木塞的试管在水浴中至少保持20min 。对于粘度按气泡升程时间为4s或4s不到的液体,为取得更为准确的结果,可与事先测好粘度或测过气泡时间的参考标准进行比较的方法测粘度(见前述参考标准)。

读数时,迅速倒置粘度管,并测空气泡上升所需秒数或与标准样对比的结果。当气泡顶部与27mm线相切时,即开动计时器读取秒数,当气泡顶部与100mm线相切时,即结束计时,则测得73mm升程的气泡时间。所有计时和比较过程,均应使粘度管保持垂直位置。若粘度管偏离其垂直方向一个半径的距离将会造成约为泡程时间10 %的误差。

对比粘度管用暂行计算标准见表4.1-2 。

加氏管与涂-4 杯粘度对照见表4.1-3 。

The viscosity of a fluid changes with temperature. For example, in the vicinity of normal temperature, if the temperature changes by 1°C, the rate of change of viscosity is about (2-10)%. , while high-viscosity fluids have a large rate of change, so no matter what method is used to measure the viscosity of the coating, attention should be paid to strictly controlling the temperature. When measuring, you should avoid lighting that exceeds the necessary illumination around the environment. The radiant heat generated by excessive lighting will change the correct indication of the thermometer or the temperature of the measured fluid. In addition, due to the large volatility of the paint, so The measurement test should be completed as soon as possible. After long-term use, some viscometers need to be calibrated with a viscosity standard solution (such as distilled water) with a guaranteed viscosity value. The viscosity and density of distilled water at various temperatures are shown in Table 4.1-4.

    See 4.1-5 for the conversion table of viscosity commonly used for coatings. Table 4.1-2 Provisional calculation standards for comparative viscosity pipes

Introduction of coating viscosity testing methods, standards and viscosity testing equipment with Figure 19

① Arranged according to the relationship between Si, Bubble Seconds and Gardner-Scherd letters, and Si according to its logarithmic value.

② The bubble time (in seconds) of the viscosity tube marked with a number less than 4s is measured by photography.

③ When the number of bubble seconds is above 2.65, for most products, it is roughly equivalent to the value measured by the dynamic method, and when it is below 2.65, this relationship is no longer maintained.

Viscosity Comparison Table of Gastrin Tube and Tu-4 Cup

Paint viscosity testing methods, standards and viscosity testing equipment introduction with Figure 20


Viscosity, kinematic viscosity and density of distilled water at various temperatures

Introduction of paint viscosity testing methods, standards and viscosity testing equipment with Figure 21

Note: The viscosity and kinematic viscosity values in the table are relatively measured based on the value of 1.0038×10-6m2/s at 20°C.

Common Viscosity Conversion Table for Coatings

Paint viscosity testing methods, standards and viscosity testing equipment introduction with Figure 22

Note: 1. Kinematic viscosity: 1, 13 drag, 2. Grignard tube, 3. International standard (ISO) viscosity cup, 4 , British standard (BS) No. 4 cup, 5 . French standard (NFT) cup size 4, 6 .American Standard (ASTM) Ford Cup No. 4, 7 . German standard (DIN) 4mm cup, 8 . German standard (DIN) 6mm cup, 9 . Engua viscometer, 10 . Barbie viscometer, 11 . Holdwood orifice viscometer, 12 . Saybolt Universal Viscometer.
2 . Dynamic viscosity: 14. Park, 15.Krebs unit.


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