Electron-induced Reactive Processing Research Articles

Fabrication of melt-spun fibers from irradiation modified biocompatible PLA/PCL blends

The effect of electron induced reactive processing (EIReP) on the properties of biodegradable polylactide/masticated polycaprolactone (PLA/PCL) blends was firstly investigated without introducing any chemical additives. Subsequently, the melt spinnability of EIReP modified PLA/PCL blends was explored by a piston spinning. Different PCL concentrations (0, 5 and 10 wt%), applied dose (0, 12.5 and 25 kGy) and take up speeds (500 and 2000 m min−1) were evaluated in order to investigate their influences on the fiber morphology, thermal and mechanical properties. SEM investigation indicated that the non-irradiated PLA/PCL fibers demonstrated less uniform diameter. However, the EIReP modification leads to a homogenous fiber diameter distribution hence uniform as-spun fibers can be produced. The crystallinity of PLA phase increased concomitantly with increased PCL contents for all fibers, whereas it slightly reduced by increasing dose. In addition, the crystallinity degree of neat PLA raised from 6.19 to 36.05% by increasing take up speed from 500 to 2000 m min−1. Interestingly, the irradiated PLA/PCL blend fibers with 5 and 10 wt% PCL demonstrated an increased fracture strain of 48.7 and 34.4%, respectively, compared with their non-irradiated fibers. It can be due to the enhanced chain entanglements and interfacial bonding between two phases. However, the irradiated fibers demonstrated similar initial modulus and reduced tenacity compared with the non-irradiated fibers.

Melt spinning of PLA/PCL blends modified with electron induced reactive processing

AbstractThe effect of electron induced reactive processing (EIReP) on the properties of biodegradable polylactide/masticated polycaprolactone (PLA/PCL) blends was firstly investigated without introducing any chemical additives. Subsequently, the melt spinnability of EIReP modified PLA/PCL blends was explored by a piston spinning. The EIReP modified PLA/PCL blends showed improved melt strength and elastic behavior. This is due to the formation of long chain branches and the enhanced chain entanglements. The crystallinity of PLA phase increased from 2.4% to 35.7% as the applied dose increased from 0 to 50 kGy. The PLA/PCL blends treated with 12.5 kGy demonstrated 2.4‐fold of impact toughness than that of neat PLA, suggesting a superior interfacial adhesion and chain interactions between two phases. The crystallinity of the PLA/PCL fibers decreased from 33.3% to 17.8% as the applied dose increased from 12.5 kGy to 50 kGy. It is resulted from the hindered chain mobility of branched/grafted structures during fiber formation. The fracture strain of the fibers using a non‐irradiated blend was 232.9% which increased to 311.5% for the 50 kGy irradiated blends. However, the fibers spun from irradiated blends demonstrated similar initial modulus but reduced tenacity compared to fibers spun from non‐irradiated blend material.

A new strategy to improve viscoelasticity, crystallization and mechanical properties of polylactide

Biodegradable polylactide/masticated natural rubber (PLA/mNR) blends were prepared by electron induced reactive processing (EIReP) without using any chemical additives. The PLA/mNR blends showed droplet-matrix morphology with decreased mNR particle size after EIReP treatment. The absolute value of complex viscosity and storage modulus increased significantly for the EIReP modified blends, suggesting the improved melt strength and elasticity. The crystallization investigation showed that the cold crystallization peak of PLA phase gradually disappeared after EIReP modification. Instead, the crystallization peak arose during melt cooling process. Consequently, the crystallinity of PLA phase increased from 6.2% to 39.0% as the mNR content increased from 0 to 20 wt%. It was found that the softening temperature of PLA examined by dynamic mechanical analysis increased effectively with the characters of higher modulus compared to the non-modified blends. The EIReP modified blends exhibited excellent mechanical properties with 7-fold increase of impact toughness compared with neat PLA, implying a superior interfacial adhesion and chain interactions between the two polymer phases. Furthermore, the thermogravimetric analysis demonstrated that the thermal stability was slightly enhanced for the EIReP modified blends.

Improved Rheology, Crystallization, and Mechanical Performance of PLA/mPCL Blends Prepared by Electron-Induced Reactive Processing

Biodegradable polylactide/modified polycaprolactone (PLA/mPCL) blends were successfully prepared by sustainable electron-induced reactive processing (EIReP) without introducing any chemical compati...

Continuous electron-induced reactive processing – A sustainable reactive processing method for polymers

The reactive processing is the method of choice for the preparation of high performance functional polymer materials, since it combines physical and chemical modification of polymer materials. During reactive processing, three different processes have to be controlled as a function of process time or process length. These are melt mixing, heat transport, and chemical reaction. Due to the use of temperature-sensitive chemical initiators, all these processes are temperature dependent whereby the precise control of the desired chemical reaction is difficult to handle. Moreover, alternative more eco-friendly reaction initiators are required. The electron-induced reactive processing uses the spatial and temporal precise initiation of the chemical reaction by high energy electrons. The precise process control enables the preparation of polymer materials with enhanced mechanical properties. With respect to future industrial applications, a continuous process of low energy electron-induced reactive processing was developed, tested and partially verified by flow simulations.

Influence of electron-induced reactive processing on structure, morphology and nano-mechanical properties of polyamide 6/fluoroelastomer blends

Electron-induced reactive processing (EIReP) is a sustainable and energy effective processing technology to modify polymeric materials in the molten state by its spatial and temporal precise energy input. In the present research, the influence of EIReP on nano-mechanical properties of polyamide 6 (PA6)/fluoroelastomer (FKM) blends (50/50 w/w) was successfully explored using advanced PeakForce quantitative nano-mechanical mapping (PF QNM) atomic force microscopy (AFM) technique. In addition, the influence of EIReP on long period of PA6 lamellae and its crystallinity in the blends was studied using small- and wide-angle X-ray scattering (SAXS and WAXS). The AFM based DMT (Derjaguin-Muller-Toporov) moduli of the matrix phase (PA6) and the dispersed phase (FKM) were found to increase, whereas, adhesion force, dissipation energy and deformation of both phases decreased with increasing dose (12.5–25 kGy). Besides of the different crystallinity of PA6 in blends compared to pure PA6, WAXS experiments have demonstrated that the unit cell dimension c-axis of PA6 was sensitive to the melt blending and EIReP. SAXS provided information about the lamellar morphology of the blend component PA6. Variations in the long period of the PA6 lamellae could be assigned to parameters of melt blending and EIReP (dose) and were correlated with the interaction parameter of the phase components and the crystallinity of the blends. PF QNM AFM and X-ray scattering studies established the relationship between the nanoscale phase structure and properties of EIReP modified rubber-plastic blends.

Process-induced morphology and mechanical properties of high-density polyethylene

Electron induced reactive processing (EIReP) is an emerging technology for the development of high performance polymer materials. It simultaneously combines the traditional electron beam (EB) treatment of polymers and their melt mixing in the presence of shear stresses and/or rates of deformation. In comparison to traditional EB treatment of high-density polyethylene (HD-PE) at room temperature, EIReP modified HD-PE shows an inhomogeneous morphology, a self-nucleation effect as well as a significant increased tensile strength and decreased elongation at break. In order to identify the reason of these changed properties and the working principle of EIReP, HD-PE has been modified by EB treatment in solid and molten state as well as before and after the presence of shear stresses and/or rates of deformation. Shear stresses and/or rates of deformation were applied during injection moulding of tensile specimens. Based on results of previous work the EB treatments and EIReP of HD-PE were performed under nitrogen atmosphere in order to reduce oxygen induced side reactions. The process induced morphological and mechanical properties have been investigated using optical light microscopy, transmission electron microscopy as well as thermal analysis and tensile tests. Changes of molecular mass were measured with size exclusion chromatography and confirmed by rheological measurements. The results demonstrate that the morphology and specific tensile properties of HD-PE were only changed by an EB treatment before the influence of shear stresses and/or rates of deformation on EB modified HD-PE during injection moulding. In addition, the state of aggregate during EB treatment has no influence on morphology and tensile properties. Consequently, the EIReP induced effect based on electron induced changes of HD-PE molecular structure and the subsequent influence of shear stresses and/or rates of deformation.

Electron-induced reactive processing of polyamide 6/polypropylene blends: Morphology and properties

Electron-induced reactive processing (EIReP) recently has appeared as an advanced processing technology to modify several polymer compounds at melt state by its spatial and temporal precise energy input. In the present work, an attempt was made to prepare a compatible blend from polar polyamide 6 (PA6) and non-polar polypropylene (PP) using EIReP without any chemical crosslinking and chemical additives. EIReP modified blends were prepared at different doses (5, 10 and 20 kGy) and dose per revolutions (3, 6 and 12 kGy/rev) while keeping constant the values of mass ratio (PA6/PP 50/50 w/w), electron energy (1.5 MeV), rotor speed (60 rpm) and temperature (230 °C). EIReP process parameters-morphology-property relationship of this blend was studied. Interestingly, co-continuous morphology of the blend was converted to droplet-matrix morphology after EIReP whether PA6 was continuous phase. Influence of dose and dose per revolution on the DMT modulus (Derjaguin-Muller-Toporov) at different phases of the blends was also measured and analyzed using advanced PeakForce Quantitative Nanomechanical Mapping atomic force microscopy (PF QNM AFM) technique. Improved nano- and macroscopic properties of EIReP modified blends were originated from the properties of the continuous matrix phase, electron-induced branching and also from the reduction of domain size of PP phase with increased dose.

Design and properties of high-performance polyamide 6/fluoroelastomer blends by electron-induced reactive processing

In recent years, electron-induced reactive processing (EIReP) has emerged as a state-of-the-art technology to modify and develop several kinds of polymeric materials. EIReP uses the spatial and temporal tuneable energy input by high energy electrons during melt mixing process in order to precisely control the desired chemical reactions and processability. Motivated by the successful development of high performance polyolefin based compounds by EIReP, we report herein for the first time the successful preparation of high-performance polyamide 6/fluoroelastomer (50/50, w/w) blends. Relationships between EIReP process parameters (non-reactive mixing time, dose per revolution, electron energy), morphology and properties of blends were established. The blends were prepared using a range of absorbed dose (12.5, 17.5 and 25kGy) while keeping constant values of electron energy (1.5MeV), dose per revolution (17.2kGy/rpm), temperature (230°C) and rotor speed (60rpm). The EIReP-modified blends exhibited excellent mechanical properties and outstanding oil swelling resistance along with good thermal stability. For example, volume swell of the blends was only 5–8% in IRM oil at 150°C for 72h, which was found to be the lowest amongst this type of rubber-plastic blends reported. The improved properties of these blends were explained with the help of interfacial tension between the phase components and electron-induced long-chain branching.

Effect of electron-induced reactive processing on morphology and structural properties of high-density polyethylene

High-density polyethylene (HD-PE) irradiated in the solid state is compared with HD-PE modified by electron-induced reactive processing (EIReP) which combines in a unique set-up the modification of polymers with high energy electrons and melt mixing processes. The effect of these different processes on the morphology and structural properties of HD-PE was investigated with X-ray analysis, differential scanning calorimetry, optical light microscopy combined with a hot stage and transmission electron microscopy as function of applied dose. The increased molecular mass was measured by using gel permeation chromatography and confirmed with rheological measurements. Even though the crystallinity and melting temperatures are constant within the studied range of dose significant differences have been observed in the morphology as well as in the crystallization behaviour. Electron treatment in the solid state causes a shift of crystallization temperature to lower temperatures due to branching and degradation whereas the irradiation under the dynamic conditions of melt mixing leads to higher crystallization temperatures with increased doses due to in-situ self-nucleation. The morphology and crystalline structure of HD-PE is not influenced by an electron treatment in the solid state, but by EIReP. Spatial and thermal stable heterogeneities have been generated only in HD-PE modified with high energy electrons under the dynamic conditions of melt mixing.

Additive free thermoplastic vulcanizates based on natural rubber

Electron induced reactive processing (EIReP) is an eco-friendly and sustainable reactive processing method based on the use of high energy electrons. It was used to cross-link the elastomeric domain phase during melt mixing in order to prepare natural rubber (NR) and polypropylene (PP) based thermoplastic vulcanizates (TPVs). The electron treatment with various values of absorbed dose showed a prominent effect on mechanical, rheological, and morphological characteristics of the PP/NR TPVs. SEM and TEM studies confirmed that these TPVs can exists across the co-continuous or discrete phase morphology. The maximum set of mechanical properties (tensile strength of 15 MPa and elongation at break of more than 500%) were obtained at an absorbed dose of 100 kGy for a 50/50 blend ratio of NR and PP without addition of any compatibilizer or chemicals. At higher values of absorbed dose the degradation of polypropylene showed a negative impact on the properties of the TPVs. Depending on the morphology and the evaluation of mechanical properties a structure–property co-relationship is drawn on the basis of common phenomenological understanding of the TPVs.

Polypropylene/natural rubber thermoplastic vulcanizates by eco-friendly and sustainable electron induced reactive processing

TPVs are a special class of thermoplastic and elastomer blend where cross-linking of elastomeric phase takes place during melt mixing process known as dynamic vulcanization (DV). A 50/50 blend of natural rubber (NR) and polypropylene (PP) were dynamically vulcanized using Electron Induced Reactive Processing (EIReP) as a function of absorbed dose (150, 250, and 350kGy) at fixed electron energy (1.5MeV) and dose per rotation. Different methods like tensile test, DSC, melt rheology, and SEM have been employed to understand the structure–property relationship of the prepared samples. The results suggest that EIReP is a novel technique to offer handful of additional features without compromising the end user property.

Electron-induced reactive processing of thermoplastic vulcanizate based on polypropylene and ethylene propylene diene terpolymer rubber

Thermoplastic vulcanizate (TPV) was prepared by in situ cross-linking of the rubber phase by high-energy electrons during melt mixing with a thermoplastic. The electron accelerator was directly coupled with the mixing device to cross-link the rubber phase in situ. The effect of the electron energy and absorbed dose per rotation on the properties and morphology of the TPV was studied. An absorbed dose of 100 kGy and a dose per rotation of 90 kGy per rotation resulted in a TPV with the best set of mechanical properties, as confirmed by morphological analysis too. The effect of different blend ratios was also studied, and it was found that a 50:50 blend ratio produced TPV with superior mechanical properties compared with 30:70 blends, as confirmed by the morphological analysis. A mechanism for the observed improvement in mechanical properties was proposed, based on the viscosity ratio of the blend components and the blend ratio. Finally, the effect of the premixing time of the blend components on the mechanical properties and morphology before the electron-induced reactive processing (EIReP) was studied. A premixing time of 14 min was required to achieve the optimum dispersion of the rubber phase in the thermoplastic phase before in situ cross-linking. EIReP of ethylene propylene diene monomer (EPDM)/polypropylene (PP) blends presents a novel approach where the EPDM phase is cross-linked and grafted to PP by high-energy electrons without any coagent during melt mixing with PP. In the present work, the effect of absorbed dose, absorbed dose per rotation, and of different blend ratios on the properties and morphology of PP-EPDM TPVs is discussed in detail. The effect of premixing time is also discussed to observe its influence on the morphology and final properties of the TPVs prepared.

Electron‐Induced Reactive Processing of Poly(propylene)/Ethylene–Octene Copolymer Blends: A Novel Route to Prepare Thermoplastic Vulcanizates

AbstractTPVs are prepared by dynamic vulcanization in which crosslinking of an elastomeric polymer takes place during its melt mixing with a thermoplastic polymer under high‐shear conditions. 30:70 wt% blends of PP and ethylene–octene copolymer are vulcanized using electron‐induced reactive processing (EIReP) employing a range of absorbed doses (25, 50, and 100 kGy) while keeping the electron energy and treatment time fixed. The structure/property relationships of the prepared samples are studied using various characterization techniques such as DMA, DSC, SEM, and melt rheology. The results suggest that EIReP offers a novel route to prepare TPVs without any chemical crosslinking and coupling agents.magnified image

Preparation of polypropylene (PP)/ethylene octene copolymer (EOC) thermoplastic vulcanizates (TPVs) by high energy electron reactive processing

Thermoplastic vulcanizates (TPVs) based on 50/50 composition of PP/EOC blend were prepared by electron induced reactive processing. To facilitate dynamic crosslinking in the PP/EOC blend, a 1.5 MeV electron accelerator was directly coupled to an internal mixer to induce chemical reactions via high energy electrons under dynamic conditions of melt mixing process. This kind of setup has been conceptualized for the first time in our laboratory and termed as electron induced reactive processing (EIReP) technique. Mechanical, morphological, and rheological properties of PP/EOC TPVs were studied with special reference to the exposure time (16–64 s) keeping absorbed dose (100 kGy) and electron energy (1.5 MeV) invariable. Chain scission dominates over chain crosslinking in both EOC as well as PP phases with the increase in exposure time. The primary factor is found to be the predominance of oxidative degradation during electron induced reactive processing in air atmosphere. The above observation was supported by Fourier Transform Infrared analyses and gel content values. Furthermore, it was found that mechanical properties depend not only on the extent of degradation in the blend system but also on the state and the mode of dispersion of the blend components.