Three-dimensional simulation of shear-induced crystallization for polymers during injection molding process

doi:10.11949/j.issn.0438-1157.20170552

Abstract

Abstract:

Based on shear induces polymer orientation and increases its equilibrium melting temperature, a Nakamura equation based shear-induced crystallization kinetics model was presented. A model for injection molding simulation was also established, in which the influence of crystallization was considered into WLF-Cross viscosity coefficient. Three-dimensional shear-induced crystallization behavior was simulated by an improved finite volume method, which coupled flow field, melt pressure, temperature, induction time index and crystallinity. Experimental results show that the proposed method can clearly simulate the three-dimensional “fountain” flow behavior and the three-layer “skin-core” crystallization structure during injection molding process. The simulated shear-induction time index results and crystallinity results agree well with the theoretical and experimental results.

Key words: injection molding, flow, crystallization, computer simulation, finite volume method

摘要：

在考虑剪切导致分子链取向并升高其平衡熔点的基础上，建立了基于Nakamura方程的剪切诱导结晶动力学模型。在WLF-Cross黏度模型中引入结晶对黏度系数的影响，构建了考虑结晶的注射成型过程模型。采用改进的有限体积法对聚合物剪切诱导结晶行为进行了三维数值模拟，模拟中耦合了流动场、熔体压力、温度、诱导时间与结晶度。结果表明，本方法可清晰模拟出注射成型过程中聚合物的三维“喷泉”流动行为以及3层“皮-芯”结晶结构，同时，诱导结晶时间指数与相对结晶度的模拟结果与理论及实验结果吻合。

关键词: 注射成型, 流动, 结晶, 计算机模拟, 有限体积法

CLC Number:

TQ320

ZHAO Peng, ZHAO Yao, YAN Bo, WANG Xiaoman, LU Shengkun, FU Jianzhong. Three-dimensional simulation of shear-induced crystallization for polymers during injection molding process[J]. CIESC Journal, 2017, 68(11): 4359-4366.

赵朋, 赵耀, 严波, 汪晓蔓, 卢圣坤, 傅建中. 注射成型中聚合物剪切诱导结晶行为的三维模拟[J]. 化工学报, 2017, 68(11): 4359-4366.

References 33

[1]	ZHAO P, PENG Y, YANG W, et al. Crystallization measurements via ultrasonic velocity:study of poly(lactic acid) parts[J]. Journal of Polymer Science Part B:Polymer Physics, 2015, 53(10):700-708.
[2]	严大东, 张兴华. 聚合物结晶理论进展[J]. 物理学报, 2016, 65(18):101-111. YAN D D, ZHANG X H. Recent development on the theory of polymer crystallization[J]. Acta Physica Sinica, 2016, 65(18):101-111.
[3]	TROISI E M, CARLERS H J M, PETERS G W M. Full characterization of multiphase, multimorphological kinetics in flow-induced crystallization of IPP at elevated pressure[J]. Macromolecules, 2017, 50(10):3868.
[4]	SANTIS F D, VOLPE V, PANTANI R. Effect of molding conditions on crystallization kinetics and mechanical properties of poly(lactic acid)[J]. Polymer Engineering & Science, 2017, DOI:10.1002/pen.24414.
[5]	王柯, 张琴, 傅强. 高分子加工制品的多层次结构控制——从传统加工到定构加工[J]. 高分子学报, 2013, (5):583-588. WANG K, ZHANG Q, FU Q. Multi-level structure control of polymeric processed products-from traditional processing to structured machining[J]. Acta Polymerica Sinica, 2013, (5):583-588.
[6]	PANTANI R, COCCORULLO I, SPERANZA V, et al. Modeling of morphology evolution in the injection molding process of thermoplastic polymers[J]. Progress in Polymer Science, 2005, 30(12):1185-222.
[7]	阮春蕾, 刘春太. 剪切流场中聚乙烯结晶过程的建模与模拟[J]. 化工学报, 2016, 67(5):2144-2151. RUAN C L, LIU C T. Modeling and Simulation of polyethylene crystallization in shear flow field[J]. CIESC Journal, 2016, 67(5):2144-2151.
[8]	王锦燕, 陈静波, 刘春太, 等. 聚合物流动诱导结晶数值模拟[J]. 化工学报, 2011, 62(4):1150-1156. WANG J Y, CHEN J B, LIU C T, et al. Numerical simulation of polymer flow induced crystallization[J]. CIESC Journal, 2011, 62(4):1150-1156.
[9]	周应国, 申长雨, 陈静波. 半结晶性聚合物熔体冷却过程双尺度模拟[J]. 工程科学学报, 2007, 29(2):186-192. ZHOU Y G, SHEN C Y, CHEN J B. Two-scale simulation of melt-cooling process of semi-crystalline polymer[J]. Chinese Journal of Engineering, 2007, 29(2):186-192.
[10]	KOWALSKA B. Study on crystallization of polymers during the injection molding[J]. Polimery -Warsaw-, 2007, 52(2):83-87.
[11]	ZHOU H. Computer Modeling for Injection Molding:Simulation, Optimization, and Control[M]. Hoboken, New Jersey:John Wiley & Sons, 2013:200-201.
[12]	DOUFAS A K, MCHUGH A J. Simulation of melt spinning including flow-induced crystallization(Ⅲ):Quantitative comparisons with PET spinline data[J]. Journal of Non-Newtonian Fluid Mechanics, 2001, 92(1):81-103.
[13]	TANNER R I. On the flow of crystallizing polymers(Ⅰ):Linear regime[J]. Journal of Non-Newtonian Fluid Mechanics, 2003, 112(2/3):251-268.
[14]	JABBRAZADEH A, TANNER RI. Flow-induced crystallization:unravelling the effects of shear rate and strain[J]. Macromolecules, 2010, 43(19):8136-8142.
[15]	TANNER R I. A suspension model for low shear rate polymer solidification[J]. Journal of Non-Newtonian Fluid Mechanics, 2002, 102(2):397-408.
[16]	BOUTAOUS M, BOURGIN P, ZINET M. Thermally and flow induced crystallization of polymers at low shear rate[J]. Journal of Non-Newtonian Fluid Mechanics, 2010, 165(5/6):227-237.
[17]	ZINET M, OTMANI RE, BOUTAOUS M, et al. Numerical modeling of nonisothermal polymer crystallization kinetics:flow and thermal effects[J]. Polymer Engineering & Science, 2010, 50(10):2044-2059.
[18]	申长雨, 周应国, 陈静波. 半结晶聚合物注射成型中结晶动力学的数值模拟[J]. 高分子学报, 2008, (8):771-777. SHEN C Y, ZHOU Y G, CHEN J B. Numerical simulation of crystallization kinetics during injection molding for semi-crystalline polymers[J]. Acta Polymerica Sinica, 2008, (8):771-777.
[19]	WANG X, KLAASEN B, DEGREVE J, et al. Volume-of-fluid simulations of bubble dynamics in a vertical Hele-Shaw cell[J]. Physics of Fluids, 2016, 28(5):243-258.
[20]	曹伟, 王蕊, 申长雨. 塑料熔体在注塑模中的三维流动模拟[J]. 化工学报, 2004, 55(9):1493-1498. CAO W, WANG R, SHEN C Y. Three dimensional flow simulation of plastic melt in injection mold[J]. Journal of Chemical Industry and Engineering(China), 2004, 55(9):1493-1498.
[21]	严波, 李阳, 孔啸, 等. 塑料注射成型结晶过程三维数值模拟[J]. 高分子学报, 2011, (2):173-179. YAN B, LI Y, KONG X, et al. Three dimensional numerical simulation of plastic injection molding process[J]. Acta Polymerica Sinica, 2011, (2):173-179.
[22]	DEMIRDZIC I, MUZAFERIJA S. Numerical method for coupled fluid flow, heat transfer and stress analysis using unstructured moving meshes with cells of arbitrary topology[J]. Computer Methods in Applied Mechanics and Engineering, 1995, 125:235-255.
[23]	严波, 李阳, 赵朋, 等. 基于改进有限体积法的三维注塑成型充模过程数值模拟[J]. 机械工程学报, 2015, 51(10):25-32. YAN B, LI Y, ZHAO P, et al. Numerical simulation of mold filling process based on improved finite volume method[J]. Journal of Mechanical Engineering, 2015, 51(10):25-32.
[24]	周文, 欧阳洁, 杨斌鑫, 等. 三维非等温非牛顿流体充模过程的建模与模拟[J]. 化工学报, 2011, 62(3):618-627. ZHOU W, OUYANG J, YANG B X, et al. Modeling and simulation of 3D non-isothermal non-Newtonian fluid filling process[J]. CIESC Journal, 2011, 62(3):618-627.
[25]	严波, 韩先洪, 孔啸, 等. 改进的有限体积法扩散项离散格式[J]. 华中科技大学学报(自然科学版), 2012, 40(5):20-23. YAN B, HAN X H, KONG X, et al. Improved finite volume method for diffusion term discretization[J]. Journal of Huazhong University of Science and Technology(Natural Science Edition), 2012, 40(5):20-23.
[26]	CHEN Y, ZOU H, LIANG M, et al. Melting and crystallization behavior of partially miscible high density polyethylene/ethylene vinyl acetate copolymer(HDPE/EVA) blends[J]. Thermochimica Acta, 2014, 586(8):1-8.
[27]	GUO J, NARH K A. Simplified model of stress-induced crystallization kinetics of polymers[J]. Advances in Polymer Technology, 2002, 21(3):214-222.
[28]	TITOMANLIO G, SPERANZA V, BRUCAO V. On the simulation of thermoplastic injection process(Ⅱ):Relevance of interaction between flow and crystallization[J]. International Polymer Processing, 1997, 12(1):45-53.
[29]	李阳, 严波, 赵朋, 等. GLS/GGLS/SUPG在三维注射成形充填模拟中的应用[J]. 化工学报, 2010, 61(2):510-515. LI Y, YAN B, ZHAO P, et al. Application of GLS/GGLS/SUPG in three dimensional injection molding filling simulation[J]. CIESC Journal, 2010, 61(2):510-515.
[30]	GUO J, NARH K A. Computer simulation of stress-induced crystallization in injection molded thermoplastics[J]. Polymer Engineering & Science, 2001, 41(11):1996-2012.
[31]	WANG L X, LI Q, SHEN C Y. The numerical simulation of the crystallization morphology evolution of semi-crystalline polymers in injection molding[J]. Polymer-Plastics Technology and Engineering, 2010, 49(10):1036-1048.
[32]	GUO X, ISAVEV A I, DEMIRAY M. Crystallinity and microstructure in injection moldings of isotactic polypropylenes(Ⅱ):Simulation and experiment[J]. Polymer Engineering & Science, 1999, 39(11):2132-2149.
[33]	LIMA M F S, VASCONCELLOS M A Z, SAMIOS D. Crystallinity changes in plastically deformed isotactic polypropylene evaluated by X-ray diffraction and differential scanning calorimetry methods[J]. Journal of Polymer Science Part B:Polymer Physics, 2002, 40(9):896-903.