Melt Rheological Behavior Research Articles

Influence of Polyetheretherketone radicals on interfacial interaction with carbon fiber and crystal formation of Polyetheretherketone at the interphase

This study investigates the impact of free radicals present in polyetheretherketone (PEEK) on its interfacial adhesion with reinforcing fibers and the resulting crystal formation at the interphase. Microdroplet tests revealed that the interfacial shear strength between PEEK and carbon fiber (CF) was enhanced under increased preparation temperatures or prolonged holding times in the molten state, corresponding to an upsurge in PEEK radicals, elucidated by electron spin resonance and melt rheological behavior analyses. The post-microdroplet testing fracture surface and PEEK crystal structure near the fiber were investigated through micro-Raman spectroscopy under varying reinforcing fiber types and functional group concentrations (e.g., -OH and -COOH) on the CF surface. The results revealed that PEEK crystal formation along the CF axis at the interphase is driven by noncovalent interfacial interactions, such as π interactions and hydrogen bonds. Conversely, covalent interfacial interactions suppress crystal formation.

Melt Rheological and Bead Foaming Behavior of Recycled Polyethylene Terephthalate/Polybutylene Terephthalate Blends Modified with a Joncryl Chain Extender

Melt Rheological and Bead Foaming Behavior of Recycled Polyethylene Terephthalate/Polybutylene Terephthalate Blends Modified with a Joncryl Chain Extender

Influence of N,N′‐ethylene bis oleamide on the flowability of the acrylonitrile‐butadiene‐styrene resin and lubrication mechanism

AbstractAs a high‐performance engineering plastic, the acrylonitrile‐butadiene‐styrene (ABS) resin possesses excellent heat resistance, chemical resistance, and toughness. However, there is a lack of flow properties of the ABS resin for many processing operations. With the aim of enhancing the flowability of the ABS resin, the effect of N,N′‐ethylene bis oleamide (EBO) as a new lubricant on the melt flow rate (MFR), torque value, and rheological behavior of the ABS resin was investigated. The result showed the MFR of the ABS resin with 2.0 wt% EBO was 22.1 g/10 min, which was improved by 49% compared with the pure ABS resin (14.8 g/10 min). The torque value of the ABS resin, including 2.0 wt% EBO (1.69 N m) was lower than that of the pure ABS resin (2.03 N m). The rheological study further indicated that EBO can reduce the complex viscosity of the ABS resin. The above results indicated that EBO was an effective lubricant for the ABS resin. A possible lubrication mechanism was proposed based on the consequences of the rotational rheometry, dynamic mechanical analysis, and molecular dynamics simulation. EBO decreased the entanglement density of the polystyrene‐acrylonitrile (SAN) molecular chains and increased the mobility of the SAN molecular chain segments. On the other hand, EBO increased the free space of motion of the SAN molecular chain segments due to the free‐volume effect thereby increasing the mean square displacement of the system. This work will provide a new way to achieve the high‐flow ABS resin and provide new insights into the lubrication mechanism of lubricants in the ABS resin thereby expanding the applications of the ABS resin.

Mechanical upcycling of single-use face mask waste into high-performance composites: An ecofriendly approach with cost-benefit analysis

The COVID-19 pandemic created an unprecedented demand for PPE, with single-use face masks emerging as a critical tool in containing virus transmission. However, the extensive use and improper disposal of these single-use face masks, predominantly composed of non-biodegradable plastics, has exacerbated environmental challenges. This research presents an innovative method for mechanically upcycling PPEs used in medical sectors i.e. single use face masks. The study investigates a facile approach for reclamation of infection-free and pure polypropylene (PP) plastic from discarded single use face masks (W-PP) and blends it with various vegetable oil percentages (5, 10 and 20 %), resulting in a versatile material suitable for various applications. Melt flow index, rheological behaviour, DSC and FTIR were employed to investigate the effect of vegetable oil/radical initiator through chemical grafting on W-PP properties. The results demonstrate significant enhancements in the tensile strength and modulus of W-PP when blended with vegetable oil and a radical initiator. There was a marked increase in tensile strength (33 %) and strain (55 %) compared to untreated W-PP, rendering W-PP both robust and flexible. Furthermore, we employed this upcycled W-PP in the fabrication of glass fibre-reinforced composites, resulting in notable enhancements in both tensile strength and impact resistance. The upcycled W-PP demonstrates excellent potential for various applications, such as sheet forming and 3D printing, where the non-brittleness of plastics plays a pivotal role in manufacturing high-quality products. The cost-benefit analysis of this approach underscores the potential of upcycling PPE waste as a sustainable solution to mitigate plastic pollution and conserve valuable resources. The applications of this upcycled material span a wide range of industries, including automotive composites, packaging, and 3D printing.

Comparative study on matrix resins in two low‐density polyethylene based cable insulation materials with different voltage grades

AbstractIn industry, crosslinked polyethylene (XLPE) cable insulation is usually produced from crosslinkable compounds consisting of low‐density polyethylene (LDPE) and additives, which known as “cable materials”. Considering that in addition to additives, the structure of matrix resin is a key factor in determining the property of XLPE, it is worthy to study the structure requirements of matrix resin for the development of cable materials with different voltage grades. In this work, the structure of matrix resins of a high voltage grade and an extra high voltage grade cable material were comparatively investigated. Interestingly, it was found that the matrix resins have no significant difference in chain structure parameters including molecular weight and its distribution and vinyl content between two samples, and their crystalline structure as well as the melt rheology and melting crystallization behavior are also very similar. These results suggest that these matrix resins may not substantially differ. Our work shows that cable materials with different voltage grades are not necessarily diverge in terms of matrix resin structure, and it could be possible to develop higher grade cable materials using the same matrix resin as lower grade counterparts.

Short aramid fiber reinforced thermotropic liquid crystalline polyester composites: Fabrication, thermal, and mechanical properties

We conducted a study to analyze the impact of short aramid fibers (AFs) on the melt-rheological behavior, thermal transition, thermal stability, and mechanical durability of thermotropic liquid crystal polyesters (TLCPs). By using different AF loading contents ranging from 3–15 wt%, we produced TLCP matrix composites through masterbatch-based melt-compounding and injection-molding. The SEM images and FT-IR spectra demonstrate that the AFs are dispersed in the TLCP matrix with a microfibrillar structure through good interfacial adhesion caused by specific intermolecular interactions between the TLCP and AFs. As a result, the complex viscosity, shear storage/loss moduli, and thermal transition (melt-crystallization, glass transition, and melting) temperatures of the composites increase with increasing AF filler content. However, the melt-crystallization and melting enthalpies increase only at low AF loading contents of 3–5 wt%. At high AF contents of 7–15wt%, the enthalpies decrease owing to the partial aggregation of AF fillers. The thermogravimetric analysis proves that the thermal stability of TLCP/AF composites improves when the AF filler is introduced. The dynamic mechanical analysis using the stepped isothermal method shows that the addition of 5 wt% AF to the TLCP leads to an approximately 150% improvement in elastic moduli and long-term mechanical durability at elevated temperatures.

Insights into the Iron- and Phosphorus-Induced Structural Rearrangements in Sodium Aluminoborosilicate Glasses and Their Impact on Melt Rheology and Crystallization Behavior

This paper presents an insight into the structural rearrangements induced by Fe2O3 and P2O5 in glasses designed in the Na2O–Al2O3–B2O3–SiO2 quaternary system. A suite of state-of-the-art characterization techniques, including magic angle spinning-nuclear magnetic resonance (MAS NMR) (on both iron-free and iron-containing glasses), Raman, and Mössbauer spectroscopies, have been employed to study the structural evolution of glasses as a function of the Fe2O3/Al2O3 ratio and P2O5 content over a broad composition space. It has been shown that while P2O5 tends to repolymerize the structure of Fe2O3-free glasses, it has a minimal impact on the network connectivity of iron-rich glasses. Further, there seems to exist a strong tetrahedral avoidance between AlO4 and FeO4 units in the glass structure. In P2O5-free glasses, iron tends to preferentially bond with borate and silicate units, while in the presence of P2O5, iron prefers to associate with phosphate (over borate and silicate) units in the glass structure. Finally, an attempt has been made to correlate the underlying structural descriptors with the rheological and crystallization behavior of glasses with an overarching goal to establish the composition–structure–property relationships in the investigated glass system.

Biocomposite PBAT/lignin blown films with enhanced photo-stability

Lignin can be obtained as a byproduct during cellulose-rich pulp fibers production and it is habitually treated as waste or intended for low-value destinations. However, due to UV absorption and mechanical properties, lignin can contribute to the fabrication of biodegradable blown films with superior performances. In this study, it was established the suitability of lignin for manufacturing biocomposite PBAT blown films with higher stiffness and photo-oxidation resistance. The effect of the filler concentration on the melt rheological behavior in non-isothermal elongational flow was investigated. The results allowed us to choose the correct filler concentration for producing films through a film blowing operation. The PBAT/lignin blown film composites displayed an increase of the elastic modulus if compared to neat PBAT films without affecting their elongation at break. Furthermore, the filler delayed the photo-oxidative degradation of PBAT hence potentially allowing open-air applications.

Structure and mechanical properties of a multilayer biomedical shaft tubing: effect of layer composition

Abstract Trilayer polymer tubes were manufactured through an extrusion process using Pebax 6333 and high density polyethylene (HDPE) as outer and inner layer, respectively. A maleic grafted linear low-density polyethylene (LLDPE) was used as the bonding layer or tie-layer. Three types of multilayer tubes were produced: (1) outer layer (Pebax) at 70% of the total wall thickness (WT), (2) outer layer at 90% of WT, and (3) outer layer at 20% of WT. The analysis of mechanical properties showed that the inner layer contributes to strength and rigidity of the tube while the outer layer provides flexibility. Melt rheology behavior for HDPE and Pebax were studied, and HDPE showed a more pronounced shear thinning behavior compared to Pebax. Orientations of the tubes were assessed using Fourier transform infrared spectroscopy (FTIR) and it was found that HDPE layer is more sensitive to molecular orientation when extruded compared to Pebax material. Melting behavior for the tubes was investigated using dynamic scanning calorimetry (DSC). The tubes showed two melting temperatures: one associated with HDPE and one with Pebax. The HDPE peak showed a specific shift to a higher melting point for tubes as a result of molecular orientation during processing. Burst and compression testing were performed on the tubes and results demonstrated that the HDPE-rich extrusion showed the highest burst pressure and compression resistance.

Characterization of polymeric biomedical balloon: physical and mechanical properties

Abstract Tubes from nylon 12 and Pebax 6333 resins were produced using an extrusion process. The extruded tubes were used to produce balloons for angioplasty applications. The tubes were stretched using blow molding process to produce balloons. Melt rheology behavior for nylon 12 and Pebax were studied and nylon 12 showed a more pronounced shear thinning behavior compared to Pebax. Orientations of the tubes and the balloons were assessed using Fourier transform infrared spectroscopy (FTIR) and it was found that nylon material is more sensitive to molecular orientation when stretched compared to Pebax material. Melting behavior for the tubes and balloons were investigated using dynamic scanning calorimetry (DSC). The melting temperature shifted to higher temperatures when the tubes are stretched into balloons and the shift was more pronounced for Pebax balloon than nylon. Morphology of Pebax balloon surface revealed a hybrid structure consisting of hard segments dispersed in soft segments and amorphous phases. The hard segments are crystallized polyamides that are biaxially oriented in the balloon with higher molecular orientation in the radial direction compared to axial direction. This resulted in a higher tensile strength along the radial direction compared to axial for the balloons. Dynamic mechanical analyzer (DMA) tests showed that the glass transition temperature of the nylon tubes shifted to higher temperatures (from 51 to 82 °C) during the balloon forming process, which means the nylon becomes stiffer and less flexible when formed into a balloon.

Influence of the Melt Extrusion Process on the Mechanical Behavior and the Thermal Properties of Ethylene Vinyl Alcohol Copolymer by Applying the Successive Self-nucleation and Annealing Thermal Fractionation

Ethylene vinyl alcohol copolymer was processed three times in a twin-screw extrusion pilot plant in order to reproduce the processing steps required to obtain EVOH nanocomposites. Thin film of the extruded EVOH was prepared by using a cast-film line. The melt flow index and rheological behavior of the film were determined. Viscoelastic parameters were evaluated in a dynamic mechanical testing instrument that revealed the presence of two signals, one attributed to the glass transition temperature and the other one related to the structural modifications associated to interlamellar separation. Thermal properties were evaluated in a differential scanning calorimetry by applying a standard evaluation and successive self-nucleation and annealing approach, finding structural modifications influenced by the melt extrusion process, although the overall percentage of crystallinity degree remains similar. Based on the structural results, the mechanical properties were evaluated considering the ethylene content and resulting on distinct mechanical behavior. Lower ethylene content allows the chain orientation induced during the processing of the film that favors the mechanical performance. Higher ethylene content promotes different deformation mechanisms and a relevant ductility.

Melt rheological behaviour of high-density polyethylene/montmorillonite nanocomposites

The present study explains the preparation of high-density polyethylene (HDPE)-based nanocomposites containing different amounts of montmorillonite (MMT) nanoclay (1–10 wt%). These nanocomposites were obtained by melt blending in a co-rotating twin screw extruder in absence and presence of a compatibiliser (HDPE-g-MA). The melt rheological behaviour of HDPE/MMT nanocomposites has been investigated by using capillary rheometer at 190°C, 200°C and 210°C over the shear rate range of 50–1000 s−1. The melt viscosity of HDPE increased marginally at 10 wt% filler loading while addition of compatibiliser to HDPE/MMT composites did not show any significant effect on viscosity. All nanocomposites showed shear thinning and non-Newtonian flow behaviour. The power law index reduced with increase in MMT concentration and increased with increase in temperature while opposite trend was observed for the consistency index. The activation energy was highest for the nanocomposites containing 10 wt% MMT and decreased upon addition of coupling agent.

Unraveling the Effect of Citric Acid on Microstructure, Rheology, and Structural Recovery of Thermoplastic Potato Starch

AbstractThe main objective of the present work is to explore the role of citric acid (CA) on microstructural changes and their impact on the melt rheological behavior, mechanical performance, and shape recovery of thermoplastic starch (TPS). The results of frequency sweep test show a pronounced nonterminal storage modulus (G’) at lower frequencies (high melt elasticity) for TPS, which is found to be greatly reduced in favor of improving the processability through the addition of CA. This could be explained in terms of reduced disentanglements of amylopectin molecules, as a crucial parameter responsible for the 3D‐type interconnected microstructure of TPS, through catalyzing effect of CA on hydrolysis. The results of the temperature sweep test (cooling mode) show a pronounced liquid‐to‐solid transition at ∼136℃ for CA‐modified TPS. This transition could be attributed to the temperature‐driven significant strengthening of the formation of single helical amylose crystalline structure and/or the hydrogen bonds between hydrolyzed amylopectin chains at temperatures below 136℃. The results are found to be consistent with the results obtained from the tensile and DMTA experiments. As expected, the shape recovery of the CA‐modified TPS sample is lower than that of unmodified TPS because of the lower elastic stored energy (stiffness) in the presence of CA, which can be largely compensated by incorporating appropriate nanoparticles.

Numerical simulation of rheological behavior of polymer in three layer co-extrusion process

The two-dimensional rheological models of the three-layer co-extrusion process for the generalized Newtonian fluid were established. Meanwhile, the flow characteristics of melts in the die channels were numerically simulated using the finite element method to explain the influence of the structure change of flow channels in the die section on the rheological behavior of melts. The simulation results indicated that the changes in the convergence angle of flow channels have certain impacts on the shift of the confluence interface of the three-layer co-extruded melt flow while little effects on the interface shape at the outlet. The flow ratio of the melt in each layer at the entrance has a significant effect on the interface shift. The flowing pressure of melts in the die is mainly determined by the inclination angle of flow channels while less influenced by the fact whether the inlets of the flow channels in each layer are smoothed or not.

Melt Rheological Behavior and Morphology of Poly(ethylene oxide)/Natural Rubber-graft-Poly(methyl methacrylate) Blends.

The influence of morphology on the rheological properties of poly(ethylene oxide) (PEO) and natural rubber-graft-poly(methyl methacrylate) (NR-g-PMMA) blends in the melt was investigated. The blends were prepared at different blend compositions by a solution-casting method. Linear viscoelastic shear oscillations measurements were performed in order to determine the elastic and viscous properties of the blends in the melt. The rheological results suggested that the blending of the two constituents reduced the elasticity and viscosity of the blends. The addition of an even small amount of NR-g-PMMA to PEO changed the liquid-like behavior of PEO to more solid-like behavior. Morphological investigations were carried out by optical microscopy to establish the relationship between morphology and melt viscosity. Depending on the blend compositions and viscosities, either droplet–matrix or co-continuous morphologies was observed. PEO/NR-g-PMMA blends exhibited a broad co-continuity range, and phase inversion was suggested to occur at the PEO/NR-g-PMMA blend with a mass ratio of 60/40 (m/m), when NR-g-PMMA was added to PEO as a matrix.

Strengthening of poly (ethylene terephthalate) by filling with short glass fibers and multi-wall carbon nanotubes

The effect of hybrid filling of poly (ethylene terephthalate) (PET) with short glass fibers (GF) and multi-walled carbon nanotubes (MWCNTs) on the static and dynamic mechanical properties of composites, as well as the structural features and rheological behavior of melts were investigated. Compounding materials was carried out by the PET melt blending with the use of the reaction extrusion method. The studied composites contained from 15 to 60 wt. % GF, the concentration of MWCNTs was 0.5 and 1.6 wt. %. It was shown that the PET hybrid filling led to a synergistic increase in the strength, the elastic modulus and the dynamic shear modulus of composites under tension and bending in a wide temperature range. MWCNT additives intensified interfacial adhesion, had a nucleating effect on the crystallization of the binder, and increased its thermal stability.

Enhancement of polyamide laser sinter powder reusability by acid catalyzed hydrolysis

This contribution introduces a method to reverse the deterioration in melt rheological behaviour (‘ageing’) of polyamide 12 that has previously been used in powder bed fusion processing by reduction of the polymers molecular weight via acid catalysed hydrolysis. Chosen hydrolysis conditions allow for a reconditioning below melting temperature and therefore leave the particulate nature of the powder intact while significantly improving the polymers rheological properties. The influences of different temperatures, acids and pH-values are investigated and the processability of recycled powders is assessed by melt rheological, optical and thermal characteristics.

Modeling of Shear Rheological Behavior of Uncured Rubber Melt

AbstractTo describe uncured rubber melt flow, a modified Phan–Thien–Tanner (PTT) model was proposed to characterize the rheological behavior and a viscoelastic one-dimensional flow theory was established in terms of incompressible fluid. The corresponding numerical method was constructed to determine the solution. Rotational rheological experiments were conducted to validate the proposed model. The influence of the parameters in the constitutive model was investigated by comparing the calculated and experimental viscosity to determine the most suitable parameters. The uncured rubber viscosity was 3–4 orders larger than that of plastic and did not have a visible Newtonian region. Compared with the Cross-Williams-Landel-Ferry (Cross-WLF) and original PTT models, the modified PTT model can describe the rheological characteristics in the entire shear-rate region if the parameters are set correctly.

Effects of Golden Flaxseed Flour on Ice Recrystallization in Uvaia (Eugenia pyriformis Cambess.) Diet Sherbet

In this study, the effects of golden flaxseed flour (GFF; Linum usitatissimum) concentrations (0, 1, 2, and 3%; w/w) on ice recrystallization in uvaia (Eugenia pyriformis Cambess.) diet sherbets fortified with iron were evaluated. Experiments were performed to simulate the conditions of temperature fluctuations. Samples were transferred from storage (− 25 °C) to a freezer programmed to perform 14 temperature fluctuation cycles ranging from − 20 °C/12 h to − 10 °C/12 h (each cycle, 48 h). The chemical composition and pH were determined before the temperature cycles. Physical parameters such as overrun, rheological properties of steady and dynamic shear, hardness, thermal properties, and ice crystal sizes were measured before the temperature cycles and every 7 days for 4 weeks. The sensory attributes were evaluated using an optimized descriptive profile (ODP). The ash content and pH results were statistically significant, and their values increased as the GFF concentration increased. The results were significant for instrumental hardness, initial melt resistance, rheological behavior, frequency and temperature sweeps, ice crystal size, and recrystallization. In the sensory evaluation, scores for coarse texture decreased and scores for GFF flavor increased as the GFF concentration increased. The ODP results were consistent with those for the rheological parameters, which justified the ice crystal size and ice recrystallization observed in the sherbets.

Effect of multi walled carbon nanotube on mechanical, thermal and rheological properties of polypropylene

In this study, multi-walled carbon nanotube (MWCNT) filled polypropylene (PP) nanocomposites prepared by melt processing methods by employing extruder and injection molding techniques were examined with various characterization methods and test procedures, in detail. Aim and novelty of the work were to merely investigate the effects of amount and dispersion of MWCNTs on mechanical, thermal and rheological properties of PP including no compatibilizer and thus chemical interaction and/or interfacial adhesion effect. The mechanical test results showed that the incorporation of MWCNTs increased the tensile strength (18.4%), flexural strength (35.2%) and modulus of elasticity (45%) while it decreased the impact strength (18%) and elongation at break (690%) values of PP/MWCNT nanocomposites. Thermal analysis data revealed that the MWCNT addition slightly increased the crystallization peak onset and peak maximum temperatures of PP under non-isothermal conditions. Frequency-dependent melt rheological behaviors of nanocomposites in linear viscoelastic regime pointed out that the storage modulus (G'), loss modulus (G''), complex viscosity (η*), and relaxation time of PP increased with the increasing amount of MWCNT. Non-linear rheological tests such as creep and stress relaxation also depicted that nanocomposites exhibited lower creep strain and relaxation rate than PP. Based on the thermal and mechanical test results, 0.3 wt% of MWCNT could be considered as the critical filler amount also called as “percolation threshold” for improving the solid-state physical properties of PP/MWCNT nanocomposites under the circumstances of no compatibilizer.