布氏粘度通常是指用布氏粘度计进行的粘度测量,有时称为布氏粘度计。Brookfield有几种型号的粘度计,但大多数都以相同的方式运行:粘度计电机以定义的速度(以rpm为单位)或剪切速率旋转主轴,粘度计测量旋转阻力并报告粘度值。According to样品的性质和要求,可以采用各种主轴设计。这是流行的安排的简要介绍:
浸入式LV主轴和RV主轴
这些标签为LV或RV主轴组,包括以圆盘或圆柱体结尾的简单轴。将400-600ml的样品放在合适的容器中,放在粘度计下,然后降低粘度计,将锭子浸入样品中,直至锭子轴上的浸没标记。浸入式主轴适用于自由流动流体粘度的比较测试。
小样本适配器(SSA)
小样品适配器是同心圆柱体测量系统,通常称为同轴或“杯和鲍勃”系统。在小样品适配器中,一个小样品(通常只有5-10ml)在移动的内筒和固定的外筒或腔室之间被剪切。顾名思义,该附件最初是为测量有限数量的样品而设计的,但是由于其间隙很小,该系统可在一定的剪切强度下运行-您希望对样品执行粘度/剪切速率曲线的宝贵能力。
超低适配器(ULA)
ULA无非是一个大型的同心圆筒,专门设计用于将粘度较低的液体引入粘度计的测量范围。
该附件使粘度计能够测量软固体,例如糊剂,乳膏和软膏。Helipath系统是一个特殊的支架,其中装有可缓慢驱动粘度计探头向下的电动机。同时,将粘度计电机设置为低速旋转(通常为2-5 rpm),并且磁头的向下运动会导致T型杆主轴切下穿过样品的螺旋路径。此处的很好的做法是在30到60秒的时间内进行几次测量并取平均值。
因此,这就是关键所在:在测量同一样品时,上述所有附件都将产生不同的结果!那么哪个是正确的呢?嗯,这超出了本文的范围(获得一些建议),但是很显然,任何报告的材料粘度规范都需要因此引用相关的仪器设置和测量条件。
此类规范中应包括的最关键参数包括:
扭矩范围:按增大扭矩(从而增加粘度)的顺序,范围为:LV,RV,HA或HB。扭矩范围通常以型号为前缀,例如:RVDVI +或LVDVII +。
Spindle, such as RV2, LV3, TC, speed: 10rpm, etc.
measure temperature
For many samples, the following will also need to be specified:
Container size and fill level details
Instrument model: such as DVI+, DVII+, etc.
Measuring time: how long you need to run the test before taking a reading - this cannot be overemphasized for thixotropic samples.
Sample Pretreatment Instructions: Premix or rest time.
So a typical specification might look like this: Brookfield LVDVII+, 500ml sample in 600ml beaker, 20 rpm rotor 3 at 25°C, measurement after 30s.
Below are some typical reported test methods and viscosity specifications for some products:
Viscosity of Anti-icing Fluids, ASTM D2196 Method B: Brookfield LVT Viscometer with Small Sample Adapter SC4-31/13R, 0.3rpm
Viscosity of resin for plastisol: Brookfield LVT or equivalent product, No. 3 spindle, rotation speed 12 rpm, temperature 25°, measure viscosity after 60s
Gel coat viscosity: Brookfield RV viscometer, spindle 4, 4 rpm, 25°C.
Brookfield "Thixotropic Index" for Gel Coat: The ratio of RV4 spindle viscosity from 4 rpm to 20 rpm at 25°C. NOTE: The term "Thixotropic Index" for this test is now obsolete, and the test is often relabeled "Shear Thinning Index"
Aluminum hydroxide gel viscosity for antacids: Brookfield LV spindle 2 at 12 rpm
