Behaviour Of High-impact Polystyrene Research Articles

High-accuracy virtual testing of air conditioner’s digital twin focusing on key material’s deformation and fracture behavior prediction

The concept of digital twin has been introduced for some time, yet one fundamental element of digital twin, digital material, has not been thoroughly studied. To interact with the physical product, the digital twin should always truthfully reflect the responses under various stimuli. In this paper, the deformation and fracture behavior of high impact polystyrene (HIPS) under the influencing factors of strain rate and stress triaxiality are studied to construct the material’s digital model. A digital twin of air conditioner product is further built and tested under virtual drop test. Comparing to experimental results, the acceleration curve, crazing induced whitening and the fracture events can all be captured by the digital twin. Our work demonstrates the importance of material characterization as an essential step to construct an accurate digital twin and shows a promising future of digital twin in virtual testing to replace traditional “trial and error” experiments.

Numerical Characterization of Behavior Under Uniaxial Tension and Modelling of Bending of Mechanical Behavior of Polymeric Materials (HIPS) And Comparison with Experience

Considering the wide use of high impact polystyrene in different fields, it is important to know its behavior in different environmental conditions. This work is interested in the characterization of the behavior of high impact polystyrene (HIPS) under tensile and bending stress.

Experimental and numerical investigation of the influence of temperature on the fracture behavior of high impact polystyrene evaluated by the J-integral approach using multiple specimen method

The aim of the present work is to study the mechanical behavior in fracture of high impact polystyrene (HIPS) subjected to tensile tests under the effect of temperature to determine the R-curves. The theory of the J-integral contour has been used for the development of a characterization method of the fracture strength appropriate to the case of this non-linear elastoplastic polymer material. To this end, we used the method of multiple specimens (Single edge notch tension SENT) of thin thickness; we used several identical test pieces containing cracks of the same lengths. The tensile tests were conducted under different temperatures, ranging from 25°C to 100°C. The results suggested a very temperature-dependent behavior due to significant increase in crack resistance as demonstrated by a comparison of JIC values related to initiation of crack propagation. The fracture energy absorbed as a function of the temperature suggested that the increase of the temperature is marked by the brittle-ductile transition in the material, which we confirmed numerically via a CASTEM software simulation.

Experimental investigation and constitutive modelling of the deformation behaviour of high impact polystyrene for plug-assisted thermoforming

This paper concerns the experimental and numerical study of the plug-assisted thermoforming process of high impact polystyrene (HIPS). The thermomechanical properties of this polymer were characterized at different temperatures and deformation rates. To study the influence of different parameters in the real conditions of plug-assisted thermoforming process, we carried out “plug-only” tests at different temperatures and plug velocities. To model the deformation behaviour of HIPS, we proposed a thermo-elastic-viscoplastic model, which we have implemented in Abaqus software. A thermo-dependent friction model was also proposed and implemented in Abaqus software. The parameters of the proposed models were identified by the inverse analysis method in the real conditions of plug-assisted thermoforming. The proposed models were validated with “plug-only” tests and plug-assisted thermoforming of yogurt container.

Fire property and charring behavior of high impact polystyrene containing expandable graphite and microencapsulated red phosphorus

High impact polystyrene (HIPS) flame retarded by expandable graphite (EG) alone or in combination with microencapsulated red phosphorus (MRP) was prepared by melt compounding and investigated in terms of its fire property and charring behavior by limiting oxygen index, UL-94, cone calorimeter test, thermal analysis and scanning electron microscopy. It has been shown that EG itself has some flame-retarding and good smoke-suppressing effect on HIPS, but the flame retardant efficiency is rather low. The addition of a small amount of MRP can improve the flame retardancy and smoke suppression of the HIPS/EG composite and decrease the loading of flame retardant considerably. The HIPS/EG/MRP composite with a mass ratio of 80/15/5 produces more char yield and exhibits good flame retardancy and smoke suppression simultaneously. The thick and thermally stable intumescent char residue covered on the surface of the HIPS/EG/MRP composite can serve as an effective barrier against heat transfer and mass exchange between flame area in the gas phase and the polymer in the condensed phase. The temperature inside the HIPS/EG/MRP (80/15/5) composite is decreased more than that inside the HIPS/EG (80/20) composite upon burning. Due to a lower effective heat flux, the pyrolysis rate of the polymer is decreased. Moreover, fuel release rate is reduced because of the increasing thermal insulation property and char yield. As a result, the flame retardancy of the HIPS/EG/MRP composite is increased noticeably. The burnt residue of the HIPS/EG/MRP composite in cone calorimeter test is not homogeneous and contains much undecomposed polymer beneath the expanded char layer.

Mechanical behavior of high impact polystyrene based on SB copolymers as a function of synthesis conditions: Part II

AbstractThe mechanical properties of different high impact polystyrene (HIPS) were determined by means of impact and tensile tests. Impact strength (IS), yield stress (σy) and Young’s modulus (E) were evaluated as a function of the rubber phase morphological features such as type and particle size (Dp), volume fraction (Φ) and interparticle distance (IPD). In order to evaluate the changes produced in the rubber phase, the initiator, chain transfer agent (CTA), and type and concentration of SB copolymer were varied during the synthesis of HIPS. Transmission electron microscopy was used to analyze the materials’ morphology and the data obtained reveal that the Dp and Φ increases mainly with an increase in the PB content and/or with the use of CTA and decreases with an increase in initiator concentration. In addition, E and yield stress diminishes when increasing the dimensions of the rubber phase (Dp and Φ), contrary to the IS. The IPD/Dp ratio also indicates the dependency of the mechanical properties with respect to the rubber phase features. An increase in IPD/Dp provokes an increases in E and σy, whereas IS diminishes.

Unusual Extensional Rheology and Dispersion Behavior of High Impact Polystyrene/TiO2 Nanocomposites Prepared by Melt‐Compounding

The extensional rheology and dispersion behavior of high impact polystyrene (HIPS) and HIPS/TiO2 nanocomposites prepared by melt‐compounding were investigated. The influence of ethylene‐vinyl acetate (EVA) copolymer on the extensional rheology of HIPS/TiO2 masterbatches was also researched. The rheological experiments investigated with Rosand Presicion Rheometer confirmed that the HIPS/TiO2 masterbatches, the HIPS/EVA/TiO2 masterbatches and the HIPS/TiO2 nanocomposites with low TiO2 loading shown different extensional rheology in comparison to the pure HIPS. Field‐emission scanning electron microscopy (FE‐SEM) shown the dispersion morphology of TiO2 nanoparticles in HIPS based nanocomposites and indicated the influence of TiO2 dispersion behavior on the unusual extensional rheology of HIPS nanocomposites.

Mechanical behavior of high impact polystyrene reinforced with short sisal fibers

Abstract In this work the mechanical behavior of high impact polystyrene (HIPS) reinforced with short sisal fibers was investigated. Tensile and fracture tests were performed under quasi-static and impact loading conditions. From uniaxial tensile tests, an increasing trend of Young's modulus with fiber content was found, whereas tensile strength and deformation at break decreased. On the other hand, in fracture tests irrespectively of loading conditions, all materials exhibited non-linear load–displacement curves with stress whitened fracture surfaces. Hence, Non-Linear Elastic Fracture Mechanics was adopted to characterize fracture behavior in these materials. Higher values of quasi-static fracture toughness were exhibited by the composites in comparison to the plain matrix up to a fiber content of about 10 wt% sisal. Conversely, the addition of sisal fibers to the HIPS matrix led to inferior impact fracture properties.

Effect of Red Phosphorus and Melamine Polyphosphate on the Fire Behavior of HIPS

Pyrolysis and fire behavior of high impact polystyrene (HIPS) containing red phosphorus and melamine polyphosphate were investigated. The thermal and thermo-oxidative decomposition were characterized using thermogravimetry coupled with FTIR and MS, respectively. The fire behavior was monitored with a cone calorimeter using different external heat fluxes and determining the LOI. Red phosphorus reduced the heat release in HIPS due to radical trapping in the gas phase. The reduction in effective heat of combustion was accompanied by an increase of incomplete combustion products such as smoke and carbon monoxide. Melamine polyphosphate in HIPS acted in the condensed phase with barrier formation. The heat release rate was reduced, whereas the total heat evolved, smoke and carbon monoxide formation were not influenced significantly. Using both fire retardants, the resulting fire retardancy was characterized mainly by superposition.

Mechanical behavior of high impact polystyrene based on SBR copolymers: Part I

The dynamic mechanical properties of a series of high impact polystyrene (HIPS) with a rubber phase based on styrene and butadiene (SBR) were studied. The variation of E′ and tan δ as a function of initiator, chain transfer agent (CTA), and SBR concentration, as well as the polybutadiene (PB) content in SBR, during the synthesis of HIPS were evaluated. For the range of concentrations studied, it was found that E′ decreased with an increase in the initiator and/or CTA concentration, as well as with an increase in the SBR content in HIPS and PB content in SBR, independently of the type of rubber phase particle obtained. In the case of tan δ, it showed a minor peak at −80 ± 10°C, which decreased in magnitude and shifted to lower temperatures with the initiator concentration, but increased with an increase in the PB content in the rubber phase. In addition, transmission electron microscopy (TEM) showed that in most cases the particle size of the rubber phase was between 0.15 and 0.25 μm, except for those HIPS samples that contained SBR with 90 wt% of PB, in which it was much larger (0.45–1.15 μm). In the latter case it was found that the modulus decreased with the PB content, and decreased further and perceptibly with increasing particle size. POLYM. ENG. SCI., 45:1288–1296, 2005. © 2005 Society of Plastics Engineers

Investigation about the effect of previous impacts on the impact behavior of high impact polystyrene (HIPS)

Investigation about the effect of previous impacts on the impact behavior of high impact polystyrene (HIPS)

1,2-Methyl-1,2-Oxaphospholan-5-One 2-Oxide Fire Retardance in HIPS: The Effect of Melamine and Novolac

The effects of commercially available 1,2-methyl-1,2-oxaphospholan-5-one 2-oxide (OP), melamine, and novolac on the limiting oxygen index and UL94 test behavior of high impact polystyrene (HIPS) were studied. A synergistic flame-retardant effect between OP and melamine was observed at the ratio 3: 2 of the additives. Thermogravimetric analysis revealed that charring in the HIPS formulations is mainly caused by an interaction between the additives. The FT-IR study of the OP and melamine-based formulation showed that the charring results in the formation of polyaromatic and polyphosphazene-type structures. The data supporting low temperature decomposition of the symm-triazine ring in the condensed state on pyrolysis are presented.

Fracture behaviour of high impact polystyrene Influence of particle morphology

The mechanical behaviour of high impact polystyrene has been examined with special attention to the influence of particle size and morphology. Video extensometry was used to follow the volume strain kinetics during tensile drawing and also to make direct observations of crack initiation in compact tension experiments at moderate rates. Materials incorporating composite particles with either small capsule (0.3 µm) or large salami (>1 µm) structures have been considered, as well as blends combining both morphologies. In the particular case of blends, a marked synergistic behaviour was achieved under impact conditions. Plasticity and fracture results, as well as morphological observations, suggest that the ability of the salami particles to stabilise the crazes initiated by the small capsules plays a key role, even at small volume fractions of salami particles.

Effects of the degree of graft on the tensile and dynamic behavior of high impact polystyrene

High Impact Polystyrene (HIPS) polymers varying widely in the degree of graft, size of the rubber particles and volume fraction of the rubber phase have been tested in uniaxial tension. From these tests, it is shown that the yield stress and tensile modulus decrease as the degree of graft increases up to about 120%, and then increase. Increasing the rubber volume fraction and the size of the rubber particles also reduces the yield stress.A dynamic test is conducted and it is verified that the glass transition temperature of the rubber phase increases with increasing the degree of graft. In addition to this, the maximum tanδ increases with increasing the degree of graft up to about 120%, and then decreases.It is also shown that the yield stress and tensile modulus of HIPS have a relationship with the dynamic behavior of the rubber phase, i.e. the yield stress and tensile modulus decrease almost linearly as the maximum tanδ increases.

Dynamic mechanical behaviour of styrene/butadiene copolymers and their blends

AbstractThe dynamic mechanical behaviour of high impact polystyrene (PS‐HI), styrene/butadiene/styrene block copolymer (SBS) and PS‐HI + SBS blends were investigated. Dynamic mechanical analysis (DMA) was performed in the temperature range −100°C to 100°C. The primary viscoelastic functions were determined. The copolymers PS‐HI and SBS as well as PS‐HI+SBS blends were investigated in creep‐fatigue regime and relaxation at temperatures 25, 30, 35, 40 and 45°C. Dynamic mechanical behavior of PS‐HI, SBS and PS‐HI + SBS blends depends on the copolymer and blends composition, the hard phase content, time and temperature. With the decrement of the hard phase PS concentration, the loss tangent of the soft phase increases while the loss tangent of the hard phase and the storage modulus decrease. All samples have a single Tg of the hard phase and a single Tg of the soft phase. The glass transition temperatures decrease as the content of the PS phase decreases. At the constant load the creep values increase and those of creep modulus decrease over a period of time, for all examined samples. These effects are more pronounced in samples with lower content of hard phase and at higher temperatures. The time‐temperature correspondence principle was applied to create master curves for the reference temperature 25°C for the creep modulus of PS‐HI, SBS and PS‐HI + SBS blends on a time scale far outside of the range measured by DMA experiments. These results enable us to predict the useful life of our copolymers and their blends in a wide range of time and temperature.

Rubber particle size and cavitation process in high impact polystyrene blends

The rubber particle size and its volume fraction are recognised as being important factors in determining the yield and fracture behaviour of high impact polystyrene (HIPS). However, correlations between the average particle size and cavitation in the rubber with toughening efficiency have only recently been established theoretically. This work provides further evidence on how the deformation kinetics in HIPS are affected by variations in the average rubber particle size highlighting along the way the role of rubber cavitation in the process. Variations in the average particle size were achieved by melt blending different proportions of two commercial grades of HIPS that had the traditional multiple inclusion particle morphology. Tensile and impact properties of the blends were measured and correlated to morphological parameters determined by quantitative image analysis. It was found that yield and fracture behaviour in tensile and impact test were strongly dependent on the amount of sub-micron particles in the blend. At high rates, toughness drops steeply with particle size. It was proposed that stress at yield and post yield strain hardening are controlled by particle size and rubber stretching respectively. Microfracture analysis by transmission electron microscopy lent support to the arguments presented.

Stress relaxation of high impact polystyrene

The stress relaxation behaviour of high impact polystyrene has been correlated with the microstructural changes observed in tensile tests. The inhomogeneity of plastic deformation, manifested as stress whitening, has been measured using microhardness tests. This method has been found to be sensitive to the amount of crazing in the material. The stress relaxation behaviour changed at the onset of crazing, but did not change appreciably as the volume fraction of crazes increased. An analysis of the relaxation in terms of a site population model based on White's approach suggests the macroscopic stress relaxation is related to the crazes in the boundary regions between the stress whitened and unwhitened material.

Studies on the rheological behavior of high‐impact polystyrene prepolymerizing systems

AbstractThe rheological behavior of high‐impact polystyrene prepolymer and its two phases separated by ultracentrifugation was studied. The viscosities of prepolymer, polystyrene phase, and rubber phase were correlated with various parameters, and a quantitative relationship among these three viscosities was proposed.

Relative influence of the mobility and the solubility parameters of fluids on the mechanical behavior of high impact polystyrene

AbstractAmong different fluid parameters having some effect on the environmental stress cracking of plastics, the surface tension and the solubility parameter are generally accepted as dominant ones. However, experimental evidence to date indicates that one single parameter can not be used as an index for predicting failure in all cases and a distinction of the conditions of their importance has not been made. This paper presents the results obtained from the creep and fatigue response of high impact polystyrene in different environments, especially those environments that do not show any effect on the unstressed polymer. The results indicate that at high stresses, the mobility of the fluid in penetrating into the polymer craze networks is more important and that at smaller stresses, the solubility parameter is more important.

The mechanical behaviour of high-impact polystyrene under pressure

High-impact polystyrene [HIPS], a two-phase polymeric system, has been investigated studying the pressure dependence of stress-elongation behaviour in tension over the range from atmospheric pressure to 4 kbar at room temperature and constant strain-rate. A comparative study of polystyrene [PS] was also undertaken. HIPS sealed from the environment exhibited ductile behaviour at all pressures. Surprisingly, specimens exposed to silicone oil environment exhibited two transitions as the applied hydrostatic pressure was raised: a ductile-to-brittle followed by a brittle-to-ductile transition. Stress-whitening was suppressed at relatively low pressures. The dilational requirement for profuse crazing was restrained by the combined effect of fluid under pressure resulting in the suppression of the energy absorption mechanism.