Change of processing behavior of rubbers in injection molding caused by material storage

Fasching, Michael; Friesenbichler, Walter; Berger, Gerald

doi:10.1063/1.4965537

Cited by 2 publications

(4 citation statements)

References 3 publications

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“…Boehm and Nguyen, 9 for example, reported the occurrence of carbon black flocculation in a filled rubber compound during storage, which obviously increased the storage modulus. Similar experience was found by Fasching et al, 10 when analyzing the kinetics of a rubber compound prior to a 4 weeks storage period and afterwards. They also mention the storage‐dependent change of the viscosity, which increases over time as the compound becomes stiffer.…”

Section: Introductionsupporting

confidence: 79%

“…The quoted volume fraction V r is derived from Equation ,

V_{normalr} = \frac{m_{r}}{m_{normalr} + m_{normals} ∙ \frac{ρ_{r}}{ρ_{s}}}

with m r and m s representing the initial weight of the rubber sample and the weight of solvent in the sample at equilibrium swelling respectively, and the corresponding densities ρ r = 1.267 g cm −3 and ρ s = 0.867 g cm −3 of rubber and solvent. Contrary to in some cases reported methodology, 2,44 it should be noted that active wiping of the samples with paper tissues, done to remove surface solvent prior to gravimetrical testing, was avoided. Instead, all solvent was removed from the sample, which was then dumped onto a paper tissue and left in the hood for 10 min before it was put on the balance.…”

Section: Methodsmentioning

confidence: 97%

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Investigation on strategies for optimizing process definition in rubber processing: A study on mechanical and chemical properties of vulcanizates as basis for the development of a new calculation model for quality prediction

Traintinger,

Kerschbaumer,

Hornbachner

et al. 2023

J of Applied Polymer Sci

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Rubber compounds may exhibit significant batch variations due to multiple different ingredients mixed in one compound. Hence, defining the manufacturing process for constant part quality can be challenging. Common strategies in considering batch variations in rubber processing include the determination of reaction kinetics, and the definition of process parameters according to normalized vulcanization isotherms. Thereby, maintenance of the degree of cure is targeted. With this path, information on the mechanical properties of vulcanizates is lost, despite its visibility from the kinetic data and part quality assurance is missed. This contribution points out the differences obtained for parts produced to the same degree of cure at various temperatures and intends to emphasize new strategies in process definitions. Therefore, compression molded parts were produced from styrene‐butadien rubber, which was then characterized with mechanical and chemical methods. Each of the methods revealed a significant difference in part behavior, which were manufactured to the same degrees of cure but at different temperatures. It was concluded that a temperature‐dependent reaction rate should be considered when quality maintenance is targeted in the production. Only then will it be possible to predict the properties adequately, with simultaneous effect of enhancing sustainability policies in rubber processing.

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Section: Introductionsupporting

confidence: 79%

“…The quoted volume fraction V r is derived from Equation ,

V_{normalr} = \frac{m_{r}}{m_{normalr} + m_{normals} ∙ \frac{ρ_{r}}{ρ_{s}}}

Section: Methodsmentioning

confidence: 97%

Investigation on strategies for optimizing process definition in rubber processing: A study on mechanical and chemical properties of vulcanizates as basis for the development of a new calculation model for quality prediction

Traintinger,

Kerschbaumer,

Hornbachner

et al. 2023

J of Applied Polymer Sci

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show abstract

“…Even under proper storage conditions, after some weeks the incubation time decreases, thus causing a risk of premature start of curing reaction, and the viscosity increases. This is reflected in deteriorated mechanical properties of the cured rubber [15]. Typically, the AEM rubber compounds are characterized by a shelf life of about 1 month, obviously if properly stored according to ISO 2230:2002-Rubber products-Guidelines for storage.…”

Section: Resultsmentioning

confidence: 99%

“…Moreover, also the processability of the raw rubber needs to be continuously controlled, because it is subject to fluctuations, from batch to batch and with storage time and temperature. A longer storage time may cause an increase in viscosity and a reduction of incubation time, thus reducing the processing window [15]. In industrial practice, the control of the process is exerted through: setup of machine parameters and laboratory tests on compounds before production run, and/or sorting of faulty parts after production run.…”

Section: Introductionmentioning

confidence: 99%

Monitoring of shear heating effects during injection molding of rubber to improve the process control

Ramini

Agnelli

2022

Polym. Bull.

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This work aims to get new insights into the “process monitoring tool” proposed by the authors for the online monitoring of the shear heating phenomenon during injection molding of technical rubber parts. The online monitoring is based on direct measurement of the surface rubber temperature (shear heating temperature, TSH) by an infrared thermal camera of the rubber as it leaves the extruder barrel of the injection molding machine. The measured rubber temperature is a process indicator giving the thermal history of the rubber compound injection and process safety. Therefore, this fast process control is applied to industrial applications to investigate the processing behavior of ethylene acrylate (AEM) rubber compounds. In particular, the relationships between TSH vs injection pressure, vs injection speed, vs screw speed rotation and vs screw length over diameter ratio (L/D ratio) and vs AEM rubber compound properties variation due to exceeding the shelf life are investigated. The results show that TSH is manly influenced by the screw L/D ratio, followed by injection pressure and screw speed rotation (especially if are set to higher levels), whereas the injection speed is the least effective parameter to reduce TSH. Furthermore, a previously found robust correlation between the shear heating parameter (ηSH) and the minimum torque measured in rheometric laboratory tests (ML) is used to show the noteworthy deviation from the proportional trend when the AEM rubber compound exceeded it shelf life. Therefore, the coefficient of determination of $${\text{log}}\eta_{{{\text{SH}}}}$$ log η SH vs ML curves provides a good indication of process stability, while it is running.

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Change of processing behavior of rubbers in injection molding caused by material storage

Cited by 2 publications

References 3 publications

Investigation on strategies for optimizing process definition in rubber processing: A study on mechanical and chemical properties of vulcanizates as basis for the development of a new calculation model for quality prediction

Investigation on strategies for optimizing process definition in rubber processing: A study on mechanical and chemical properties of vulcanizates as basis for the development of a new calculation model for quality prediction

Monitoring of shear heating effects during injection molding of rubber to improve the process control

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