Construction of interfacial interlocking structure through elastic turbulence in multi⁃melt multi⁃injection molding （M3IM）

doi:10.19491/j.issn.1001-9278.2024.12.014

Abstract

Abstract:

In this study， multi⁃melt multi injection molding （M3IM） was employed to construct a hierarchical structure for an incompatible system of poly（vinylidene difluoride）（PVDF） and high⁃density polyethylene （PE⁃LD）， and their interfacial properties were investigated. The results indicated that a unique interfacial interlocking structure was formed in these two incompatible polymers under the special external field of M3IM process， resulting in an increase in the peeling strength by 3.3 times. The experimental and numerical simulation analyses demonstrated that the formation of such an interfacial interlocking structure was attributed to an unstable flow generated at the breakthrough region when the secondary melt was injected into the primary melt as well as the elastic turbulence of the polymer melt at low Reynolds numbers. The Reynolds numbers in the thickness direction presented a bimodal distribution and tended to increase by more than one order of magnitude at the interface region. Compared to the regions before the breakthrough part， the turbulent kinetic energy and kinetic energy dissipation rate of the melt increased significantly after the breakthrough part.

Key words: multi?melt multi?injection molding, interfacial interlocking structure, elastic turbulence, interface strengthening

CLC Number:

TQ320.66⁺2

XIAO Yuanhao, CHU Liqiu, CHEN Libo, ZHANG Shijun, ZHAO Xin, ZHANG Hao, LYU Yun, LIU Lei, ZHANG Kai, YANG Mingbo. Construction of interfacial interlocking structure through elastic turbulence in multi⁃melt multi⁃injection molding （M3IM）[J]. China Plastics, 2024, 38(12): 81-89.

Figures/Tables 14

Fig.1. Schematic representation of melt filling process in M3IM

Fig.2. Schematic diagram of M3IM system and samples preparation

样品	一次熔体	二次熔体	一次注射温度/℃	二次注射温度/℃	一次注射体积/cm³	二次注射体积/cm³	一次注射速率/cm³·s^-1	二次注射速率/ cm³·s^-1	模具温度/℃	延迟时间/s
MPE 160	PVDF	PE⁃HD	200	160	4.6	4.3	40	28.4	20	1
MPE 180	PVDF	PE⁃HD	200	180	4.6	4.3	40	28.4	20	1
MPE 200	PVDF	PE⁃HD	200	200	4.6	4.3	40	28.4	20	1
MPE 220	PVDF	PE⁃HD	200	220	4.6	4.3	40	28.4	20	1

Tab.1. Processing conditions used in M3IM

Fig.3. Shear viscosity of PVDF and PE⁃HD at different temperatures.

Fig.4. PLM micrographs of MPE220 samples in D1~D6 regions

Fig.5. PLM micrographs of MPE220 in D1~D6 regions

Fig.6. Thickness of the primary flow layer and the secondary flow layer in MPE samples prepared with different melt temperatures of PE⁃HD

Fig.7. DSC curves of MPE samples

Fig.8. FTIR spectrum of MPE samples

Fig.9. The volume fraction nephogram of the MPE220 sample after the secondary melt started to be injected

Fig.10. Velocity in Y⁃axis as a function of time for D1~D6 regions

Fig.11. Renold number as a function of time for D1~D6 regions

Fig.12. （a） Turbulent dissipation rate （ε） and （b） turbulent kinetic energy（κ） varying at the center of D1~D6 regions

Fig.13. Interfacial peeling properties of MPE samples with different processing temperatures

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[1]	. Construction of interfacial interlocking structure through elastic turbulence in Multi-melt Multi-injection Molding (M3IM) [J]. , 2024, (12): 0-0.
[2]	JI Cao, ZHOU Guofa. Interface Strengthening Mechanism of Short Fiber Bridging for Metal⁃Matrix Polymeric Composites [J]. China Plastics, 2021, 35(3): 59-66.