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浙江大学学报(工学版)
Journal of ZheJiang University (Engineering Science)  2020, Vol. 54 Issue (8): 1474-1480    DOI: 10.3785/j.issn.1008-973X.2020.08.004
    
On-line measurement device for viscosity of polymer melt during injection molding process
Jian-feng ZHANG1(),Peng ZHAO1,*(),ZHOU Hong-wei 2,Jian-zhong FU1,Zi-chen CHEN1
1. Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province, Zhejiang University, Hangzhou 310027, China
2. Tederic Machinery Co. Ltd, Hangzhou 310018, China
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Abstract  

A device for measuring the viscosity of the polymer melt during injection molding process was designed and manufactured. The cavity of this non-isothermal and high-shear rate rheological mold is designed as a slit with a thickness of 1 mm or 2 mm. The bottom is un-sealed and the continuous flow of polymer melt can be maintained. The pressure sensors are mounted along the central line of flow direction, thus the melt pressure in the mold cavity can be real time detected. The mold temperature is controlled by the mold temperature machine. A PXIe acquisition card is utilized to acquire, display and record the experimental data. The melt pressure at different locations is measured by pressure sensors. The melt viscosity was calculated according to the corrected law of Newton's shear stress theorem and compared with the theoretical value of the Cross-WLF model. Results show that the designed mold is safe and reliable, and the melt pressure of the low density polyethylene (LDPE) can be detected during the injection molding process. Further, the apparent viscosity evolution of the material during injection molding process can be calculated. Experimental results agree well with the theoretical values in the high shear rate range with the shear rate greater than 500 s?1, the error is within 18%, and the minimum is 4%. This proposed device can realize the online measurement of the melt information during injection molding process.

Key words： polymer      injection molding      rheology      mold      viscosity      on-line measurement     
Received: 04 July 2019      Published: 28 August 2020
CLC:  TQ 320  
Corresponding Authors: Peng ZHAO     E-mail: 21725029@zju.edu.cn;pengzhao@zju.edu.cn
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Jian-feng ZHANG
Peng ZHAO
ZHOU Hong-wei
Jian-zhong FU
Zi-chen CHEN
Cite this article:

Jian-feng ZHANG,Peng ZHAO,ZHOU Hong-wei ,Jian-zhong FU,Zi-chen CHEN. On-line measurement device for viscosity of polymer melt during injection molding process. Journal of ZheJiang University (Engineering Science), 2020, 54(8): 1474-1480.

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http://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2020.08.004     OR     http://www.zjujournals.com/eng/Y2020/V54/I8/1474


注射成形中聚合物熔体黏度的在线测量装置

设计并制造在线测量注射成形过程中聚合物熔体黏度变化的装置. 在测量装置中，非等温高剪切流变模具的型腔结构设计成厚度为1 mm或2 mm的狭缝，底部不封口，维持熔体的持续流动；在流动中心线上沿流动方向布置一组压力传感器实时检测聚合物熔体在模具型腔中的压力变化情况，并使用模温机控制模具温度. 使用PXIe采集系统采集、显示、记录实验数据. 实验通过压力传感器测量得到不同位置熔体压力，根据修正的牛顿黏性定律计算熔体黏度，并与Cross-WLF模型的理论值进行对比. 实验结果表明：所设计的模具安全可靠，可获得低密度聚乙烯(LDPE)熔体在注射成形过程中熔体压力的变化情况，从而可以计算出材料在成形过程中的表观黏度演化情况. 实验测量结果与理论值在剪切速率大于500 s?1的高剪切速度范围内较吻合，误差均在18%以内，最小为4%. 该装置能满足真实成形条件下聚合物熔体信息的在线检测要求.


关键词： 聚合物,  注射成形,  流变,  模具,  黏度,  在线检测 
Fig.1 Schematic diagram of cavity structure of rheological mold and pressure sensors arrangement
Fig.2 Schematic diagram of overall structure of rheological mold
Fig.3 Schematic diagram of overall architecture of measurement system for viscosity of polymer melt
Fig.4 Pressure curves of different injection speeds with oil of mold temperature machine set to 100 °C
Fig.5 Pressure curves of different injection speeds with oil of mold temperature machine set to 120 °C
Fig.6 Variety of pressure peaks at different temperatures and injection speeds
Fig.7 Viscosity curve of melt at different mold temperatures with 1 mm thickness cavity
Fig.8 Viscosity curve of melt at different mold temperatures with 2 mm thickness cavity
Fig.9 Corrected viscosity curve of melt with 1 mm thickness cavity
Fig.10 Corrected viscosity curve of melt with 2 mm thickness cavity
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