A method based on the time–temperature superposition principle to predict pressurization time in compression molding

Zhang, Tao; Zhao, Yongxiang; Zhang, Boming

doi:10.1002/app.46664

Cited by 4 publications

(3 citation statements)

References 43 publications

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“…Hence, we introduce the time-temperature equivalence principle to illustrate why longer processing times are required compared to melt processing, which is described by WLF law, that is, deformation and relaxation response of viscoelastic polymers is deeply dependent relation between time and temperature. [33,34] Many properties, including the relaxation modulus, viscosity, diffusion rate, etc, is depending on macromolecular mobility. For polymers in a highelastic state with low pressure applied, the requirement of more processing time can overcome the viscoelasticity of the polymer particles and promote their fusion.…”

Section: Processing Condition Effectmentioning

confidence: 99%

Preparation and tribological behavior of high‐temperature oil‐containing porous polyimides

Wan

Jia

Zhan

et al. 2023

Polymer Engineering & Sci

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This paper aimed to attempt the fabrication of high‐temperature oil‐containing porous polyimides (OCPPIs) using as‐polymerized powder with a no processing melting point, as well as investigate its tribological behavior. The OCPPIs were fabricated using a cold‐press sintering technique containing multiple gradient processing steps. Coalescence tightly among polymer powders was successfully achieved under a high‐elastic state by extending holding time vastly based on the time–temperature equivalence principle. The results indicate that OCPPIs possessed a high performance of oil retention after centrifuging in rotation 6000 r/min within 120 min whether low or high porosity. The tribological behaviors were evaluated by reciprocating friction tests under point‐contact conditions. Surprisingly, the tribological properties showed counterintuitive performance, wherein the best performance on the anti‐friction and wear resistance is encountered for the PPIs with the lowest porosity due to the excellent mechanical performance. The corresponding tribological mechanism with respect to multi‐phase wear and liquid–solid lubrication was also discussed comprehensively. This work fills the gap with respect to the fabrication of high‐temperature oil reservoirs and contributes to further understanding the forming mechanisms of porous materials under a high‐elastic state.

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Section: Processing Condition Effectmentioning

confidence: 99%

Preparation and tribological behavior of high‐temperature oil‐containing porous polyimides

Wan

Jia

Zhan

et al. 2023

Polymer Engineering & Sci

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“…deformation and relaxation response of viscoelastic polymers is a deeply dependent relation between time and temperature. 44,45 The relaxation kinetics of polymers obeys the WLF law as heating to a solid-like state. Many properties, including the relaxation modulus, viscosity, diffusion rate, etc., are depending on macromolecular mobility.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Property investigation for high-Performance Polyimides fabricated via compression molding in solid-like state

Wan

Jia

Zhan

et al. 2022

High Performance Polymers

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A compacted body was fabricated by pulverulent polyimide (PI) block copolymers using solid-like state compression molding (SCM) technique. Polymer heated to solid-like state, i.e. the high-elastic non-melting state above the glass transition temperature ( Tg) and well below melting temperature, could achieve plasticity due to dramatic decreases in elastic modulus. Tensile properties were taken as response values, and the results of single-factor experiments indicated that molding temperature was the dominant parameter on mechanical performances, followed by molding pressure and holding time. Within this context, the SCM process possesses a longer processing time window whereas the processing temperature is narrow. The manufacturing defects induced by inappropriate processing conditions also hurt the tribological performance of PIs. Particles in a solid-like state could coalesce tightly only by exerting both high temperature and pressure in the SCM process. Thermoforming mechanism examined by atomic-scale molecular dynamics simulation indicated that non-bonding interaction forces, especially van der Waals forces play a key role in fusing among polymeric particles. This study is devoted to establishing the interdependence of structure-formability-property for high-temperature polymers that are not melt processible.

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“…On the other hand, Li & Zhang [26] obtained viscosities of epoxy resin at each curing degree using the "viscositycure" shift function. Zhang, Zhao & Zhang [27] discovered the temperature-time regulation of viscosity. The Williams-Landel-Ferry (WLF) equation is applied by Karkanas & Partridge [28] to model the viscosity.…”

Section: Introductionmentioning

confidence: 99%

A preform deformation and resin flow coupled model including the cure kinetics and chemo-rheology for the VARTM process

Larsson

Blinzler

2020

Int J Mater Form

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The present paper deals with preform deformation and resin flow coupled to cure kinetics and chemo-rheology for the VARTM process. By monitoring the coupled resin infusion and curing steps through temperature control, our primary aim is to reduce the cycle time of the process. The analysis is based on the two-phase porous media flow and the preform deformation extended with cure kinetics and heat transfer. A novel feature is the consideration of temperature and preform deformation coupled to resin viscosity and permeability in the VARTM process. To tackle this problem, we extend the porous media framework with the heat transfer and chemical reaction, involving additional convection terms to describe the proper interactions with the resin flow. Shell kinematics is applied to thin-walled preforms, which significantly reduces the problem size. The proposed finite element discretized system of coupled models is solved in a staggered way to handle the partially saturated flow front under non-isothermal conditions efficiently. From the numerical example, we conclude that the cycle time of the VARTM infusion process can be shortened over 68% with the proper temperature control. Moreover, the proposed framework can be applied to optimize the processing parameters and check the compatibility of a resin system for a given infusion task.

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A method based on the time–temperature superposition principle to predict pressurization time in compression molding

Cited by 4 publications

References 43 publications

Preparation and tribological behavior of high‐temperature oil‐containing porous polyimides

Preparation and tribological behavior of high‐temperature oil‐containing porous polyimides

Property investigation for high-Performance Polyimides fabricated via compression molding in solid-like state

A preform deformation and resin flow coupled model including the cure kinetics and chemo-rheology for the VARTM process

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