Interdiffusion Of Chains Research Articles

Stereocomplex crystal formation in sheath/core and sea/island Poly(l-lactic acid)/poly(d-lactic acid) fibers prepared through laser-heated melt electrospinning and subsequent annealing processes

Sheath/core (S/C) and sea/island (S/I) bicomponent fibers consisting of poly (l-lactic acid) (PLLA) as the sheath or sea component and poly (d-lactic acid) (PDLA) as the core or island component were fabricated using a bicomponent melt-spinning process. The obtained fibers were then subjected to laser-heated melt electrospinning (LES) using a rotating collector. The molecular orientation of the LES fibers increased as the fiber diameter decreased because of the increase in take-up velocity. Wide-angle X-ray diffraction revealed that the as-spun fibers were in an amorphous state. The differential scanning calorimetry (DSC) measurements showed a cold crystallization peak, followed by melting peaks of the homocrystal (HC) and stereocomplex crystal (SC), with the SC peak being more prominent for the S/I fibers. It is speculated that the distance required for the interdiffusion of PLLA and PDLA molecular chains in the fiber cross section substantially affected the transition from HC to SC during DSC measurements. The S/C and S/I fibers annealed at 120 °C after the LES were composed of HC. However, after annealing at 190 °C, which is above the melting temperature of HC, the S/C fibers fused, whereas the S/I fibers remained intact, resulting in well-separated ultrafine fibers composed of highly oriented SC.

Flexural behaviours and heterogeneous interface fracture in overmoulded multi-material thermoplastic composites

The development of lightweight multi-material composites is imperative to meet the demands of the aerospace and automotive industries. Thermoplastic-based multi-material composites represent a novel approach, wherein two or more distinct composite materials are combined to create a hybrid material with enhanced performance characteristics. However, varying failure modes across multi-scale interfaces in the composites affect their mechanical performance in a complex manner. In this study, multi-material composites were manufactured through overmoulding of virgin polycarbonate (VP) and short-fibre reinforced polycarbonate (SFP) on continuous fibre-reinforced thermoplastic polycarbonate (CFRTP) laminate to assess behaviours of heterogeneous interfaces and structural performance under flexural loading. In the compression overmoulding process, the consolidation of thermoplastics creates interdiffusion of polymer chains across the multi-material interfaces. The multi-material composites successfully demonstrated enhanced flexural properties compared to single material constituent such as VP, SFP, and CFRTP. Benchmarking with CFRTP composite laminates, results revealed that overmoulding SFP on CFRTP results in 319 % higher flexural strength and 36 % higher of flexural modulus. VP/CFRTP composite offered 103 % more flexural strain and 175 % more specific energy absorption during fracture. Strategic optimization of the neutral axis (NA) and integration of high modulus materials in multi-material systems contributed to such performance enhancements. Failure analysis conducted using optical microscope and scanning electron microscopy (SEM) revealed progressive heterogeneous interface fracture and crack propagation in the CFRTP laminate layer. Results indicated that control of interface failure modes need to be considered in multi-material structure design to achieve desired flexural strength.

Fabrication of PEI/CF composite parts with multi-angle reinforced mechanical properties by a micro-extrusion foaming FDM process

The combination of fused deposition modeling (FDM) and foaming technology enables the fabrication of complex hierarchical and lightweight parts. However, this approach is hindered by a reduction in the mechanical properties of final parts. To this end, with the aim of addressing the challenge of the fabrication of 3D-printed parts with enhanced mechanical and lightweight features, a micro-extrusion foaming FDM process using CO2 as a blowing agent was hereby established, and the carbon fiber (CF) was selected as a reinforcing filler. Compared to pure polyetherimide (PEI) parts, the longitudinal tensile strength of the PEI/CF parts with 5.0 wt% CF added increased by 30.3 %, while the interfacial bonding strength of PEI/CF-5.0 foamed parts increased by 86.3 % compared to the unfoamed parts. Furthermore, the PEI/CF-5.0 foamed parts, weighing only about 1.7 g, could bear a load of a 60 kg human body in multiple directions. Additionally, focusing on the filler orientation and the enhanced interdiffusion and entanglement of polymer chains at interfaces, the reinforcement mechanisms of the foamed parts fabricated by micro-extrusion foaming FDM process were discussed. The micro-extrusion foaming FDM process demonstrated the capability to produce lightweight parts with enhanced mechanical properties, making it a promising technology for applications in the aerospace and military industries.

Statistical aspects of diffusive adhesion between polymers with drastically different molecular mobility: Weibull’s and normal probability analysis

ABSTRACT A comprehensive statistical analysis of the distributions of the lap-shear strength (σ) originated during the contact of the specimens of dissimilar miscible entangled amorphous polymers with drastically different bulk glass transition temperatures (T g b) has been carried out in the vicinity of the T g b of one polymer but well below the T g b of the other. For this purpose, polystyrene (PS) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) were chosen. To form mechanically durable PS-PPO adhesive joints (AJ) via the chain interdiffusion mechanism, the specimens of PS (T g b = 103°C) and PPO (T g b = 216°C) were kept in contact for a period of time (t) of 2 min to 96 h at a constant bonding temperature (T) in the vicinity of the PS T g b but, at the same time, well below (even by 126°C) the PPO T g b. The AJs formed were shear fractured in tension at ambient temperature. Totally, 21 σ datasets measured have been analyzed using Weibull’s and normal probability models. By using proposed two dimensionless statistical parameters, the reciprocal Weibull’s modulus (1/m) and the standard deviation (SD) reduced to the average σ value (σ av), SD/σ av, the data scatter estimated in the two methods have been compared.

Protein‐Mediated ZnO Synthesis for Self‐Healing in Natural Rubber

AbstractNatural rubber (NR) consists of mainly cis‐1,4‐polyisoprene with proteins as notable nonrubber components that significantly influence its properties. A relatively unexplored aspect is the role of these proteins in reducing and stabilizing metal ions to form metallic particles. Here, the NR/ZnO composite is successfully prepared by in situ generation of ZnO in the NR latex for the first time. With the aid of the proteins, the amount of ZnO is slightly higher than that formed in the saponified NR latex (SPNR), where some proteins are removed. Importantly, the noncovalent bonds between the proteins and/or amino acids with the ZnO formed in the NR latex can provide the self‐healing behavior of the NR/ZnO composite. However, heating at ≈40 °C is still necessary for reducing the healing time and increasing the self‐healing efficiency of the composite. Nevertheless, greater noncovalent bonds within NR/ZnO hinder rubber molecular chain interdiffusion and rearrangement essential for self‐healing behavior in uncross‐linked rubber, resulting in lower healing efficiency compared to SPNR/ZnO. This study underscores the significance of proteins and/or amino acids on NR's properties, despite their minor presence. Without sophisticated NR modification, this is a very simple and low‐cost technique to achieve the NR/ZnO composite with self‐healing behavior.

Bead geometry–induced stress concentration factors in material extrusion polymer additive manufacturing

PurposeMaterial extrusion additive manufacturing processes inevitably produce bead-shaped surface patterns on the walls of parts, which create stress concentrations under load. This study aims to investigate the influence of such stress concentrations on the strength along the build direction (“Z-strength”).Design/methodology/approachThis work consists of two main parts – an experimental demonstration to show the significance of stress concentrations on the Z-strength, followed by numerical modeling to evaluate the theoretical stress concentration factors (kt) for such shapes. Meso-scale finite element analysis (FEA) was performed to evaluate kt at the roots of the intersecting bead shapes. The critical bead shape parameters influencing kt were identified, and parametric FEA studies were performed on different bead shapes by varying the normalized parameters.FindingsThe experimental results showed that up to a 40% reduction in the effective Z-strength could be attributed only to the presence of surface bead shapes. Bead overhang and root radius were identified as critical shape parameters influencing kt. The results of the parametric FEA studies were used to generate a single empirical equation to determine kt for any bead shape.Originality/valuePredictive models for Z-strength often focus on crystallization kinetics and polymer chain interdiffusion to predict interlayer adhesion strength. The authors propose that the results of such studies must be combined with surface bead-shape induced stress concentration factors to obtain the combined, “effective” Z-strength.

Effect of drying conditions on adhesion strength of a pressure-sensitive adhesive

ABSTRACT Regular surface roughness could be created on the surface of a pressure-sensitive adhesive (PSA) film through Marangoni flow during the drying process. Therefore, tailoring of both surface and bulk characteristics of the PSA and consequently its adhesion strength could be expected by controlling the drying conditions. Herein, surface and bulk properties of a water-based PSA dried at various temperatures and humidities were scrutinized. Increase in the drying temperature improved the adhesion strength of the PSA to poly(ethylene terephthalate) due to enhanced surface nanoroughness of its film. At constant humidity, the higher the Péclet number, the higher the Marangoni number and the rougher the PSA film surface. Drying humidity rise, however, improved the adhesion strength due to more uniform distribution of copolymers constituting the PSA, better interdiffusion of chains through the interface of polymer particles in a prolonged drying process, and increased surface free energy of the film. The adhesion strength of the PSA, similar to the here-defined viscoelastic dissipation ability, demonstrated a power dependence on the film surface nanoroughness. This newly-defined parameter considers taking advantage of the real viscoelastic dissipation of the PSA regarding its potentiality through thorough wetting of the substrate surface with the PSA.

Influence of Molecular Weight on the Bead Foaming and Bead Fusion Behavior of Poly(butylene terephthalate) (PBT)

A current trend in the progress of bead foams is the use of engineering polymers (i.e., poly(butylene terephthalate) (PBT)), which are more temperature resistant than commodity polymers and thus offer new areas of application. Currently, foaming and molding of PBT bead foams seem to be possible only with an epoxy-based chain extender. This modification leads not only to an increase in molecular weight but also to a changed PBT chain architecture (i.e., branching or even cross-linking). Thereby, the crystallization behavior is considerably slowed down so that the time for chain interdiffusion across neighboring bead surfaces is prolonged. This study investigates the molecular weight influence separately. The crystallization behavior is controlled by varying the length of linear PBTs in such a way that different bead fusion phenomena result. With increasing molecular weight, a lower open cell content (OCC), and therefore a higher expansion behavior during thermomechanical analysis, was observed, which increases the contact area between the beads in the cavity during the steam chest molding process. Adding to the literature shown so far, this study shows that linear chemically unmodified PBT can also be processed into bead foam components using PBTs having a higher molecular weight.

Crosslinking versus interdiffusion in two pot one pack acetoacetoxy-amine based binder system

A two-pot-one-pack waterborne crosslinking system is studied by following the crosslinking and interdiffusion between the polymer particles functionalized with acetoacetoxy on one hand and with polyethyleneimine on the other. FTIR spectroscopy and rheological measurements are used to follow the evolution of crosslinking, while pyrene excimer fluorescence is used to analyse the interdiffusion of polymer chains between neighbouring particles during film formation. Both crosslinking and interdiffusion proceed slowly at room temperature. However, crosslinking is complete after 24 h at 60 °C, while interdiffusion does not proceed further at this temperature. TEM images confirm the presence of a honeycomb structure in the final film, produced by the crosslinked moieties between polymer particles that can act as a barrier for interdiffusion of polymer chains between particles. Nevertheless, strong films are produced even in the absence of significant interdiffusion, due to the crosslinks between particles.

Construction of self-healing polyethersulfone ultrafiltration membrane by cucurbit[8]uril hydrogel via RTIPS method and host-guest chemistry

In this work, the self-healing polyethersulfone ultrafiltration membrane constructed by host-guest chemistry between cucurbit [8]uril (CB [8] is a family of macrocyclic compounds comprising 8 glycoluril units) and two guest molecules based on reverse thermally induced phase separation (RTIPS) method was developed, which had excellent self-healing performance, better mechanical properties, and high permeation flux and BSA rejection rate. The membrane autonomously restored it BSA rejection rate up to about 89% from rejection rate levels as low as 21% after damage. The observed self-healing performance were attributed to the swelling of pore-filled CB [8] hydrogel into the damage position, the molecular interdiffusion of the hydrogel chains, the strong hydrogen bond of the hydrogel chains and the host-guest interaction between CB [8] and two guest molecules (HEC-Np and PVA-MV). SEM morphologies illustrated that the prepared pore-filled membrane via the RTIPS method had homogeneous and porous skin surface and sponge-like cross-section, which imparted the prepared membranes with improved permeability and better mechanical properties. Properties of MR-CB [8] membranes, which varied with increased content of CB [8], were evaluated by permeability, water contact angle, thermogravimetric analysis (TGA), mechanical properties, FRR, scanning electron microscope (SEM) and atomic force microscopy (AFM). The contact angle water showed that CB [8] hydrogel enhanced the surface hydrophilicity of the prepared membrane. TGA illustrated that the thermal stability improved with the increased content of CB [8]. The optimal pore-filled CB [8] hydrogel membrane (MR-CB [8]2) exhibited that the pure water flux reached 2100.5 L/m2 h, while the BSA rejection rate remained at 86.0%. The results of this work suggested pore-filled CB [8] hydrogel membrane was a more promising way to develop polyethersulfone ultrafiltration membranes with self-healing performance.

Microstructure development of PEBA and its impact on autoclave foaming behavior and inter-bead bonding of EPEBA beads

Expanded poly(ether-block-amide) (EPEBA) bead foams are a new class of advanced thermoplastic elastomer foams with low density and high resilience. Steam-chest molding realizes the fabrication of the molded EPEBA bead foams with complex geometry. However, the evolution of polymer microstructure in autoclave foaming process and the bonding mechanism behind the steam-chest molding of EPEBA beads are still unclear. In this work, the microstructure development of PEBA was characterized by DSC, SAXS and rheological methods. Then, EPEBA beads with an expansion ratio higher than 25-fold were prepared by autoclave foaming, and the molded EPEBA bead foams with a density lower than 0.15 g/cm3 and a resilience higher than 70% were produced by steam-chest molding. According to the change about thermal properties of EPEBA beads before and after steam-chest molding, a possible inter-bead bonding mechanism during EPEBA beads molding was proposed. The amorphous soft segments and melted low-ordered hard segments promoted the welding process. However, the well-ordered hard segments hindered the interdiffusion of polymer chains at the interface, which leaded to the reduced tensile strength and the narrowed molding temperature window of EPEBA bead foams.

Plugging performance and mechanism of temperature-responsive adhesive lost circulation material

Lost circulation is a great challenge during drilling and results in high financial costs. Despite the extensive advances in recent decades, lost circulation materials (LCMs) still have low success rates that fail to address lost circulation in fractured formations. This study proposes a novel temperature-responsive adhesive lost circulation material (TALCM) to control such losses. TALCMs consist of bridging and adhesive LCMs, which can be activated by formation heat. Once activated, the surfaces of the adhesive LCMs bond to the bridging LCMs through interdiffusion and entanglement of polymer chains. First, the thermodynamic properties of three kinds of thermoplastic resins were studied, namely low-density polyethylene, acrylonitrile butadiene styrene, and polyamide 6. Then, one of these resins was chosen as the adhesive LCM for its better adhesive and viscoelastic properties. Finally, a series of experiments was conducted on the plugging efficiencies of TALCMs. The results show that TALCMs achieve adhesive plugging when activated by formation heat during lost circulation control. The maximum pressure-bearing capacity of a TALCM was observed to be 14 MPa, with the compressive strength being higher than those of conventional bridging LCMs (7.5 MPa) when plugging a 1-mm-wide slot. More importantly, TALCMs can control severe lost circulation that the conventional LCMs or crosslinking polymers cannot address.

Two-step heat fusion kinetics and mechanical performance of thermoplastic interfaces

Thermoplastic polymers and composites are ubiquitous in the industry for their reshaping and fusing capabilities at elevated temperatures. The quality of heat-fused thermoplastic interfaces is of great concern for adhesion, coating, and welding applications, especially those between dissimilar materials. Kinetic evolution of the microstructures defines the mechanical performance of heat-fusion thermoplastic interfaces, which is studied here using polyethylene and polypropylene as an example. Key factors such as the viscosity and compatibility of polymers and the time and temperature of fusion are discussed by combining molecular-level simulations and structural-level hot-compression experiments. Inter-diffusion and entanglement of polymer chains are identified as the two elementary kinetic steps of the fusion, which dominate the control on the stiffness and strength of the interfaces, respectively. Experimental data shows that the quality of fused interfaces can be improved by reducing the viscosity and the interaction parameter. Following the same set of time-scaling relations as identified in the simulations, the two-step characteristics and their effects on the stiffness and strength are experimentally validated. Both simulation and the experiment results show that Young’s modulus of fused interfaces recovers faster than the strength that is controlled by polymer entanglement to a large extent, rather than diffusion. These findings add insights into the design of fusion processes, laying the ground for the applications of thermoplastic polymers and composites.

Reducing the amount of coalescing aid in high performance waterborne polymeric coatings

One of the objectives of the waterborne coatings industry is to reduce or eliminate solvents out of latex paints, maintaining or increasing the mechanical performance in a way that makes industrial adaptation as plain and economical as possible. This task has been tackled by the use of temporary oligomer plasticizers (TOP) in this work. The aim of TOPs is to use oligomers to achieve the plasticisation during film formation without changing significantly the final properties of the film. The incorporation of oligomers in the polymer particles is obtained by in-situ formation with the help of a chain transfer agent added in the reactor at the end of the main polymerization step. The TOP concept is translated as well from a conventional copolymer acrylic composition to a commercial formulation with promising results. On the other hand, a study of the role of the plasticizer during film formation is carried out by measuring the chain interdiffusion rate using the Pyrene Excimer Fluorescence (PEF) technique. The reduction of the amount of co-solvent needed to produce films at room temperature by the use of TOP is therefore associated to a faster diffusion of polymer chains in the presence of oligomers.

Interlayer fusion bonding of semi-crystalline polymer composites in extrusion deposition additive manufacturing

This work focuses on the evolution of interlayer fracture toughness properties of fiber-reinforced, semi-crystalline polymers in the extrusion deposition additive manufacturing (EDAM) process. Further, this work bridges the gap between the additive process conditions (time-temperature history) and the effective layer-to-layer fracture properties developed within a printed component. This is the first step to predict delamination that can occur during printing, during cooling to room temperature after printing, and during service performance of an additively manufactured geometry. A phenomenological model is developed for fusion bonding of semi-crystalline polymer matrix composites by coupling the interdiffusion of polymer chains with the evolution of polymer crystallinity. While the interdiffusion is captured by reptation theory of polymer dynamics, the evolution of crystallinity is modeled by phenomenological crystallization kinetics and crystal melting dynamics. Further, a methodology is developed to determine the critical strain energy release rate, GICof the interlayer interface and experiments are conducted utilizing the double cantilever beam fracture test geometry. Predictions of GIC as a function of thermal history are compared with experiments.

Surface enrichment and interdiffusion in blends of semiflexible polymers of different stiffness.

A model for a mixture of two kinds of semiflexible polymers (A and B) with the same chain length (NA = NB = 32), but different persistence lengths, confined between parallel planar repulsive walls in a common good solvent is studied by molecular dynamics simulations. In the isotropic phase at low polymer concentrations, both polymers are repelled by the walls, and the system is anisotropic near the walls over a range controlled by the polymer linear dimensions. Close to the concentrations where in the bulk nematic order sets in, precursors of thick nematic layers at the walls are observed, strongly enriched by a stiffer component, which hence is depleted in the center of the slit pore. At larger concentrations, where in the bulk a uniformly mixed nematic phase occurs, the enrichment of B-chains at the walls is rather minor, extending over the scale of the transverse correlation length of concentration fluctuations, which is of the order of a few monomeric diameters only for the present model. In this ordered phase, both self-diffusion and interdiffusion of chains (in the direction perpendicular to the director) are found to be significantly slowed down in comparison to dilute solutions. Since equilibration times scale with the square of the slit thickness, incomplete equilibration is predicted when polymeric coatings on substrate containing polymers differing in stiffness are produced.

Investigation of Carbon Black/ Polyester Micro-composites: An Insight into Nano-size Interfacial Interactions

In the micro/nanomaterial reinforced composites, interfacial interactions at the interface of filler/polymer lead to the formation of a third layer called interphase as the secondary reinforcing mechanism. The interphase may be formed due to local adsorption of polymer chains at the interface, mechanical interlocking, and interdiffusion of polymer chains. Since the interactions govern the load transfer at the filler/polymer interface, they play a key role in the mechanical response of reinforced composites. However, there exist only a few well-established and validated studies in the description of the interfacial interactions presented in thermosetting composites. This research aims at the understanding of correlations amongst the mechanical properties of thermosetting polyester composites reinforced with 0-15 wt. % of carbon black (CB) focusing on the nano-size cooperative rearranging region (CRR). To estimate the length of CRR, thermal analysis of the variations in the specific heat capacity or the relaxation strength within the glass transition temperature (Tg) range was measured using a thermodynamic model. A nano-size CRR of 10 nm on average was estimated and correlated to the enhanced impact and toughness behavior of the specimens. The results suggested the presence of softer interphase based on the Tg values influenced by the CBs agglomeration level and cross-linking density, which in turn governs the mechanical response of the composites. The methodology introduced in this study can be used in the explanation of changes in mechanical and physical properties of reinforced composites with a focus on the underlying role of nano-size interfacial interactions.

Basic physicochemical processes governing self‐healable polymers†

AbstractThis short review outlines basic chemical and physical principles that can be utilized in the development of self‐healing polymers. Physical processes include the interdiffusion of polymer chains, the introduction of phase‐separated morphologies, shape memory effects or incorporating active nanoparticles into a polymer matrix. Dynamic covalent, free radical or supramolecular bonds are predominantly chemical processes. However, self‐healing will also involve a combination of physical and chemical events, such as taking advantage of enhanced van der Waals forces resulting in inter‐digitated copolymer morphologies or embedded reactive encapsulated fluids that burst open upon damage to fill up a wound. Sufficient molecular mobility for autonomous self‐healing under ambient conditions can also be achieved while maintaining high strength and stiffness in precisely designed commodity polymers. The efficient storage and recovery of conformational entropic energy stored during damage or excess of surface energy resulting from damage will drive the reduction of newly generated interfaces created upon damage by shallowing and widening wounds until healed. © 2021 Society of Industrial Chemistry.

Elongational Flow Field Processed Ultrahigh Molecular Weight Polyethylene/Polypropylene Blends with Distinct Interlayer Phase for Enhanced Tribological Properties.

Herein, we produced a series of ultrahigh molecular weight polyethylene/polypropylene (UHMWPE/PP) blends by elongational-flow-field dominated eccentric rotor extruder (ERE) and shear-flow-field dominated twin screw extruder (TSE) respectively and presented a detailed comparative study on microstructures and tribological properties of UHMWPE/PP by different processing modes. Compared with the shear flow field in TSE, the elongational flow field in ERE facilitates the dispersion of PP in the UHMWPE matrix and promotes the interdiffusion of UHMWPE and PP molecular chains. For the first time, we discovered the presence of the interlayer phase in blends with different processing modes by using Raman mapping inspection. The elongational flow field introduces strong interaction to enable excellent compatibility of UHMWPE and PP and induces more pronounced interlayer phase with respect to the shear flow field, eventually endowing UHMWPE/PP with improved wear resistance. The optimized UHMWPE/PP (85/15) blend processed by ERE displayed higher tensile strength (25.3 MPa), higher elongation at break (341.77%) and lower wear loss of ERE-85/15 (1.5 mg) compared to the blend created by TSE. By systematically investigating the microstructures and mechanical properties of blends, we found that with increased content of PP, the wear mechanism of blends varies from abrasive wear, fatigue wear, to adhesion wear as the dominant mechanism for two processing modes.

The effect of phase separation on crystallization of polyethylene/poly(ethylene-alt-propylene) blend

The influence of liquid–liquid phase separation (LLPS) on crystallization kinetics in off-critical and near-critical blends of polyethylene/poly(ethylene-alt-propylene) (PE/PEP) is studied to explore the origin of the two crystallization peaks in differential scanning calorimetry with the same long period. The PE/PEP blend systems show upper critical solution temperature (UCST) type of phase diagram and the crystallization temperature of PE component is much lower than the UCST, LLPS occurs first. The crystal nuclei first form at the interface region of two phases and then it is necessary for the PE chains to diffuse there to continue the crystallization process from both PE-rich and PEP-rich regions. As a result, the crystallization kinetics pathway is dynamically influenced by LLPS period of time, quench depth and initial composition because they control inter-diffusion coefficient in both phases. In the off-critical blend, the LLPS is extremely slow. The area ratio of the two DSC crystallization peaks doesn't fit with the ratio of coexistence compositions of PE in PE-rich and PEP-rich phases until LLPS has reached its equilibrium before crystallization. The crystallization of PE dominates the final morphology. Small and randomly dispersed crystals could be observed because the inter-diffusion of PE chains in PEP-rich phase is greatly hindered and they could not contribute to the formation of more perfect crystals. In the near-critical blend, LLPS kinetics is comparatively much faster, so the area of the two DCS crystallization peaks agrees with the coexistence compositions of PE. LLPS is the key factor to determine the final morphology.