Effective Nucleating Agent Research Articles

Effect of starch nanoparticles on the crystallization kinetics and photodegradation of high density polyethylene

Starch nanoparticles (SNp) with a diameter of ca. 70 nm were synthesized and used as fillers to prepare high density polyethylene (PE) composites by in situ polymerization. The effect of these particles on the thermal degradation, isothermal and nonisothermal crystallization, and photodegradation of PE was studied. SNp decreased the thermal degradation temperature of PE as tested by thermogravimetric analysis and increased the relative crystallinity and crystallization rate under isothermal conditions. This nucleating agent effect was confirmed by nonisothermal crystallizations as composites presented higher crystallization temperatures than neat PE. The photodegradation tests under UV radiation during 28 days showed that NPp promoted the polymer degradation by increasing the amount of carbonyl groups and by forming cavities at the nanoparticle/PE interface. Our findings open up new strategies for using SNp as filler in PE matrices to increase not only its photodegradation, but also its thermal properties.

Effective Nucleation Host Alloys (ENHAs): A New Materials Solution for Stable and Effective Li Metal Anodes

There is a global demand for high energy storage systems for portable consumer devices of cell phones, laptops, including electric vehicles. Lithium ion batteries (LIBs) are the most promising options due to the high volumetric, gravimetric energy, and power densities. Current LIBs using LiCoO2, LiNiO2, LiMnO4, and LiFePO4 cathodes coupled with a graphite anode exhibit a power density of 100-260 Whkg-1 [1]. Recent studies on high capacity Li – S batteries indicate their promise for replacing low capacity carbon anodes with Li metal and composites. However, Li metal plating on Cu/Li substrates shows undesirable performance due to Li plating instabilities leading to formation of high surface area Li, loss of Li due to uneven plating/deplating, increase in internal resistance and formation of deleterious Li dendrites[2-4]. The fundamental plating phenomena, result in low columbic efficiencies, increase in plating/deplating potentials and consequent hysteresis losses causing rapid fade in specific capacity/energy density and thermal run away either due to increased internal resistance or internal short circuiting of the cell due to formation and growth of unwanted dendrites. To address the above issues, novel structurally isomorphous alloys (SIAs) were developed to replace the copper/carbon systems with their ability to modify the Li plating morphology by altering the nucleation and growth mechanisms. These alloys comprise effective host alloys (EHAs) with similar crystallographic registry as Li serving as the Li source. Different effective nucleating agents (ENAs) are alloyed with EHAs to form novel effective nucleating host alloys (ENHAs) transforming the Li plating phenomena towards the uniform homogenous nucleation and growth regimes. High energy mechanical milling (HEMM) was used to synthesize these new materials and the evolution of the phases was studied using X-ray diffraction. The EHAs as the anode system with a hexagonal close packed crystal (HCP) structure shows inferior overall performance albeit eliminating dendrite formation. However, ENHAs formed by alloying EHAs with ENAs with the body-centered cubic structure, display the ability of ENHAs to act as an effective Li source for plating/de-plating. The ENHAs when studied for Li plating/de-plating in a CR2025 coin cell using Li as the counter/reference electrode and 1M LiPF6 in EC:DEC:FEC as the electrolyte at different areal current/charge densities, improved reversible Li plating/de-plating with a high coulombic efficiency of ~99.6% at the end of 200 cycles is observed (Fig 1a). The plating/de-plating potential decreases ~20-40 mV as the electrode stabilizes after 40 cycles (Fig 1b). Post cycling SEM analysis (Fig 1c) reveal absence of dendritic morphologies due to efficient nucleation and uniform growth during Li plating. Different alloy compositions of ENHAs are studied for lithium plating and their phase evolution, electrochemical performance and post cycling SEM analysis results will be presented and discussed.

Morphology and Isothermal Crystallization Kinetics of Polypropylene/Poly(ethylene-co-vinyl alcohol) Blends

Abstract Polypropylene (PP)/poly(ethylene-co-vinyl alcohol) (EVOH) blends were prepared by melt blending using PP-g-MAH as a compatabilizer. The microstructure and rheological behavior of PP/EVOH blends were studied. The results showed the that EVOH particles were uniformly dispersed in the PP matrix and inhibited the mobility of PP chains. The isothermal crystallization kinetics and morphology development of PP/EVOH blends were compared with that of pure PP. It was found that the EVOH essentially acted as an effective nucleating agent for PP, which could significantly increase the nucleation rate because the EVOH molecules in PP/EVOH blends aggregated together to form interface. Therefore, the introduction of EVOH increased the overall rate of isothermal crystallization compared with pure PP, although the PP molecular chains would be hindered seriously if excessive amounts of EVOH were added. X-ray diffraction showed that pure PP and PP/EVOH blends exhibited an identical crystal structure, and the crystallinity of the PP phase in the blends was not significantly different from that of pure PP.

Development of Sustainable and Cost-Competitive Injection-Molded Pieces of Partially Bio-Based Polyethylene Terephthalate through the Valorization of Cotton Textile Waste.

This study presents the valorization of cotton waste from the textile industry for the development of sustainable and cost-competitive biopolymer composites. The as-received linter of recycled cotton was first chopped to obtain short fibers, called recycled cotton fibers (RCFs), which were thereafter melt-compounded in a twin-screw extruder with partially bio-based polyethylene terephthalate (bio-PET) and shaped into pieces by injection molding. It was observed that the incorporation of RCF, in the 1–10 wt% range, successfully increased rigidity and hardness of bio-PET. However, particularly at the highest fiber contents, the ductility and toughness of the pieces were considerably impaired due to the poor interfacial adhesion of the fibers to the biopolyester matrix. Interestingly, RCF acted as an effective nucleating agent for the bio-PET crystallization and it also increased thermal resistance. In addition, the overall dimensional stability of the pieces was improved as a function of the fiber loading. Therefore, bio-PET pieces containing 3–5 wt% RCF presented very balanced properties in terms of mechanical strength, toughness, and thermal resistance. The resultant biopolymer composite pieces can be of interest in rigid food packaging and related applications, contributing positively to the optimization of the integrated biorefinery system design and also to the valorization of textile wastes.

Droplet Microfluidics XRD Identifies Effective Nucleating Agents for Calcium Carbonate

AbstractThe ability to control crystallization reactions is required in a vast range of processes including the production of functional inorganic materials and pharmaceuticals and the prevention of scale. However, it is currently limited by a lack of understanding of the mechanisms underlying crystal nucleation and growth. To address this challenge, it is necessary to carry out crystallization reactions in well‐defined environments, and ideally to perform in situ measurements. Here, a versatile microfluidic synchrotron‐based technique is presented to meet these demands. Droplet microfluidic‐coupled X‐ray diffraction (DMC‐XRD) enables the collection of time‐resolved, serial diffraction patterns from a stream of flowing droplets containing growing crystals. The droplets offer reproducible reaction environments, and radiation damage is effectively eliminated by the short residence time of each droplet in the beam. DMC‐XRD is then used to identify effective particulate nucleating agents for calcium carbonate and to study their influence on the crystallization pathway. Bioactive glasses and a model material for mineral dust are shown to significantly lower the induction time, highlighting the importance of both surface chemistry and topography on the nucleating efficiency of a surface. This technology is also extremely versatile, and could be used to study dynamic reactions with a wide range of synchrotron‐based techniques.

Mesoporous Metal–Organic Frameworks as Effective Nucleating Agents in Protein Crystallography

Mesoporous metal–organic frameworks (mesoMOFs) have gained some attention as protein immobilization agents. Herein, and for the first time, three model proteins (lysozyme, trypsin, and albumin) wer...

Development and characterization of novel and stable silicon nanoparticles-embedded PCM-in-water emulsions for thermal energy storage

A phase change material (PCM) emulsion was prepared by dispersing the PCM in water with the aid of emulsifiers, which had higher fluidity, higher thermal conductivity, and more flexible volume change than the solid-liquid PCMs. However, a critical issue for their large-scale applications is phase instability due to aggregation and precipitation of the PCM droplets. This work was to develop stable PCM emulsions prepared with n-hexadecane by manipulating the key factors and analyzing the emulsion properties including emulsifier combinations and process conditions, interfacial film properties, droplet size distribution, and rheology characteristics. The stability was further improved with the addition of SiO2 nano-particles. The SiO2 nano-particles also acted as an effective nucleating agent to reduce the degree of supercooling. The thermal performance for potential application in thermal energy storage systems was also examined. Eventually, a novel and highly stable PCM-in-water nano-emulsions with droplets on a scale of tens of nanometers and a transparent appearance was developed for potential application in active thermal energy storage systems.

Non-Isothermal Crystallisation Kinetics of Carbon Black- Graphene-Based Multimodal-Polyethylene Nanocomposites.

The effect of carbon black (CB) and microwave-induced plasma graphene (g) on the crystallisation kinetics of the multimodal high-density polyethylene was studied under non-isothermal conditions. The non-isothermal crystallisation behaviour of the multimodal-high-density polyethylene (HDPE), containing up to 5 wt.% graphene, was compared with that of neat multimodal-HDPE and its carbon black based nanocomposites. The results suggested that the non-isothermal crystallisation behaviour of polyethylene (PE)-g nanocomposites relied significantly on both the graphene content and the cooling rate. The addition of graphene caused a change in the mechanism of the nucleation and the crystal growth of the multimodal-HDPE, while carbon black was shown to have little effect. Combined Avrami and Ozawa equations were shown to be effective in describing the non-isothermal crystallisation behaviour of the neat multimodal-HDPE and its nanocomposites. The mean activation energy barrier (ΔE), required for the transportation of the molecular chains from the melt state to the growing crystal surface, gradually diminished as the graphene content increased, which is attributable to the nucleating agent effect of graphene platelets. On the contrary, the synergistic effect resulting from the PE-CB nanocomposite decreased the ΔE of the neat multimodal-HDPE significantly at the lowest carbon black content.

One-pot route to graft long-chain polymer onto silica nanoparticles and its application for high-performance poly(l-lactide) nanocomposites.

A facile “one-pot” synthetic route to modify SiO2 nanoparticles with long-chain polymer was developed. The structure and morphology of SiO2 grafted with poly(l-lactide) (SiO2-g-PLA) were characterized by FTIR, TGA, GPC, and TEM. Furthermore, a series of PLA/SiO2-g-PLA nanocomposites were prepared with different nanofiller loadings, and their related performances were investigated. As an effective nucleating agent, the SiO2-g-PLA had a positive effect to improve the crystallization rate and increase the crystallinity. Meanwhile, the PLA nanocomposites presented outstanding mechanical properties including excellent toughness and high stiffness. In addition, the PLA materials kept good transparency with less than 3 wt% nanofillers. Overall, this work provides a useful method for preparing high-performance polymer nanocomposites.

Industrializable and sustainable approach for preparing extended-chain crystals of biodegradable poly(butylene succinate) and their applications

While polymer extended-chain crystals (ECCs) own promising physicochemical properties, effective product and application of ECCs is still challenging. Here, we develop an industrializable and sustainable production procedure process for ECCs of poly(butylene succinate) (PBS), which consists of a specially-designed melt mixing of the polymer and urea in internal mixer to produce inclusion complex and thereafter a washing step with water. The prepared ECCs show melting point at 137 °C and crystallinity higher than 90%, and the auxiliary materials, urea and water, can be recycled. The ECCs are further used as highly effective nucleating agent and reinforcer for commercial PBS, resulting in remarkable simultaneous increases in crystallization temperature, yield stress and elongation at break due to the perfect lattice matching and interfacial compatibility. Moreover, a shape memory material of single component of PBS has been fabricated with the in-situ addition of ECCs.

Hollow Fiber Porous Nanocomposite Membranes Produced via Continuous Extrusion: Morphology and Gas Transport Properties.

In this work, hollow fiber porous nanocomposite membranes were successfully prepared by the incorporation of a porous nanoparticle (zeolite 5A) into a blend of linear low-density polyethylene (LLDPE)/low-density polyethylene (LDPE) combined with azodicarbonamide as a chemical blowing agent (CBA). Processing was performed via continuous extrusion using a twin-screw extruder coupled with a calendaring system. The process was firstly optimized in terms of extrusion and post-extrusion conditions, as well as formulation to obtain a good cellular structure (uniform cell size distribution and high cell density). Scanning electron microscopy (SEM) was used to determine the cellular structure as well as nanoparticle dispersion. Then, the samples were characterized in terms of mechanical and thermal stability via tensile tests and thermogravimetric analysis (TGA), as well as differential scanning calorimetry (DSC). The results showed that the zeolite nanoparticles were able to act as effective nucleating agents during the foaming process. However, the optimum nanoparticle content was strongly related to the foaming conditions. Finally, the membrane separation performances were investigated for different gases (CO2, CH4, N2, O2, and H2) showing that the incorporation of porous zeolite significantly improved the gas transport properties of semi-crystalline polyolefin membranes due to lower cell wall thickness (controlling permeability) and improved separation properties (controlling selectivity). These results show that mixed matrix membranes (MMMs) can be cost-effective, easy to process, and efficient in terms of processing rate, especially for the petroleum industry where H2/CH4 and H2/N2 separation/purification are important for hydrogen recovery.

Polymorphism and properties of biodegradable poly(1,4‐butylene adipate) tailored using an aliphatic diamide derivative

AbstractN,N′‐Ethylenebis(12‐hydroxystearamide) (EBH), an aliphatic diamide organic compound with environmental friendliness, was selected as an effective nucleating agent to be incorporated into poly(1,4‐butylene adipate) (PBA) polyester. EBH increased the crystallization temperature, crystallinity, crystal density and thermal stability, and shortened the crystallization time of PBA. EBH slowed down the critical temperature of the PBA α‐crystal, accelerated the β‐to‐α phase transition rate and tailored the polymorphic crystalline structure of the PBA probably via the interfacial interaction and/or crystal lattice matching between PBA and EBH. In the presence of EBH, the degradation rate of PBA decreased. The mechanisms of the nucleation, manipulation of the crystal type, accelerated β‐to‐α phase transition, enhanced thermal stability and decreased enzymatic degradation rate of PBA are proposed and discussed in detail. © 2018 Society of Chemical Industry

Crystallization kinetics and morphology of poly(lactic acid) with polysaccharide as nucleating agent

An ever-increasing concern about environmental pollution has spearheaded research into alternative biodegradable polymers. Currently, poly(lactic acid) (PLA) is one of the most notable biodegradable polymers due to its superior properties and low production cost. Nucleating agents have been used to overcome slow PLA crystallization. The present work aims at investigating cashew gum (CG) as nucleating agent in PLA produced by casting process. The effect of the CG (1–10 mass%) on the PLA crystallization process was evaluated by thermal analysis and hot-stage optical microscopy. The relative degree of crystallinity, crystallization kinetic parameters under isothermal conditions, and crystallite morphology of pure PLA and PLACG samples were also investigated. The PLA crystallization rate increased with the CG content at a temperature ranging from 130 °C to 140 °C. An increase in the degree of crystallinity and a reduction in the crystallite size of the PLA were observed in the samples which contained 5 and 10 mass% of CG. Cashew gum proved to be an effective nucleating agent for PLA. Results show that cashew gum can be used as a natural nucleating agent for PLA when faster crystallization rate, better crystallite size control or higher degree of crystallinity are required.

Modification of polypropylene with nanosized α-Al2O3 powders prepared by the mechanochemical method

Nanosized [Formula: see text]-Al2O3 powders were prepared by the mechanochemical method, with AlCl[Formula: see text]H2O and NH4HCO3 as raw materials, the environmentally friendly starch as an effective dispersant. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to characterize the ammonium aluminum carbonate hydroxide (AACH) precursor and products. The results show that nanosized spherical [Formula: see text]-Al2O3 powders without hard agglomeration and with particle size in the range of 20–40 nm can be obtained by this novel and green method. Then, polypropylene (PP)/nano [Formula: see text]-Al2O3 nanocomposites were prepared by melt blending in a mixer apparatus. The crystallization behavior and mechanical properties of PP/[Formula: see text]-Al2O3 nanocomposites were further investigated in this study. Wide-angle X-ray diffraction (WAXD) results show that a small amount of [Formula: see text]-crystal of PP forms after adding [Formula: see text]-Al2O3 nanoparticles. According to differential scanning calorimetric (DSC) measurement, the [Formula: see text]-Al2O3 nanoparticles make crystallization temperature of PP enhanced by acting as effective nucleating agents. The tensile strength and impact strength were both improved significantly with the addition of [Formula: see text]-Al2O3 nanoparticles through tensile and impact tests. Scanning electron microscopy (SEM) observation showed that the fracture surface became rougher and further confirmed the above result.

The Influence of Space Restriction on the Mechanical Properties of Isotactic Polypropylene/Reduced Graphene Oxide Nanocomposite Injection Bars

Isotactic polypropylene (iPP)/reduced graphene oxide (RGO) nanocomposite bars were prepared by injection molding and the effects of RGO on the iPP matrix were investigated via differential scanning calorimetry, two dimensional wide angle X-ray diffraction (2D WAXD) and small angle X-ray scattering (2D SAXS) techniques. It is demonstrated that RGO is an effective nucleation agent for iPP and the incorporation of RGO can enhance the degree of orientation of iPP crystals at flow direction. Furthermore, the orientation of iPP chains at flow direction intensifies with the increase of RGO contents, which can be attributed to that RGO obstructed the motion of orientated polymer chains. Although the enhancement effect is weaker than that of High density polyethylene (HDPE)/RGO nanocomposites with epitaxial crystallization, the mechanical properties of iPP/RGO nanocomposites can also be improved apparently.

Nucleation effect of adipic acid metal salts in isotactic polypropylene

A series of adipic acid metal salts as nucleating agents for isotactic polypropylene (iPP) were synthesized from adipic acid (Adi) and corresponding metal hydroxides or chlorides by neutralization or double decomposition reaction. The effect of different adipate on the crystallization and melting behavior of iPP were investigated by differential scanning calorimetry (DSC). The results indicated that after adding different metal salts of adipic acids, the crystallization peak temperature of nucleated iPP was increased by different degree. Adi, barium adipate (Adi-Ba), and zinc adipate (Adi-Zn) had higher nucleation efficiency. Notably, Adi-Zn and Adi-Ba were highly effective β-crystal nucleating agents; the others were α-crystal nucleating agents. In addition, the relative content of β-crystals in nucleated iPP was higher than 0.9 with the addition of Adi-Ba or Adi-Zn, especially when Adi-Zn was added at 0.05 mass% reached 0.9422, indicating that Adi-Ba and Adi-Zn are highly active and selective β-nucleating agents for iPP.

Ternary nanocomposites based on plasticized poly(3-hydroxybutyrate) and nanocellulose

Poly(3-hydroxybutyrate) (PHB) ternary nanocomposites were obtained by solvent-casting method. The current work compares the behavior of nanocomposites made with two different plasticizers and two types of nanocellulose (cellulose nanocrystals—CNC—and bacterial cellulose—BC). A traditional plasticizer (glyceryl tributyrate—TB) and a polymeric one (poly[di(ethylene glycol) adipate]—A) were chosen in order to evaluate the responses of PHB properties to the addition of plasticizers with different molecular weight. Additionally, the influences of CNC and BC on the properties of the plasticized polymer were compared. Cellulose nanocrystals were determined as effective PHB nucleation agents when TB was added to the samples. On the other hand, the addition of A and CNC seems to retard PHB nucleation but enhances the thermal stability of the samples due to the intrinsic stability of the additives. A counterbalanced effect of TB plasticizer and CNC was observed in the mechanical and water vapor permeation properties. The addition of BC to the plasticized samples showed the highest detriment in thermal stability of PHB due to its poor dispersion. It was concluded that PHB/TB/CNC nanocomposites will be suitable materials for using as packaging in single-use applications, showing an appropriate balance among barrier, thermal, and mechanical properties.

Preparation and Performance Analysis of Modified Sodium Acetate Trihydrate.

In order to solve undercooling and phase separation of sodium acetate trihydrate (SAT), experimental screening method was used to select nucleating agents and thickeners that are suitable for SAT, and the optimal ratio was identified. Through screening experiments of nucleating agents, it is found that disodium hydrogen phosphate can be used as an effective nucleating agent for SAT. When the weight content of disodium hydrogen phosphate in SAT is 2%, the degree of undercooling was reduced to approximately 2 K. The addition of 1–1.5% (weight) of xanthan gum (XG) to SAT can effectively inhibit the phase separation. Since the properties of SAT changes after the modification, the corresponding comparison analysis was performed. The results showed that XG has a significant influence on the SAT performance of SAT. With the addition of 1.5 wt % of XG in pure SAT, the latent heat of fusion and solid/liquid volume expansion reduce by 5.2% and 5.4% respectively, and the thermal conductivity and solid/liquid density also decreases accordingly.

Effect of Carboxylic Acid Nucleating Agent on Crystallization and Mechanical Properties of PLA/PBS Blends

Poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) blends were prepared using a carboxylic acid salt as nucleating agent (NA). The effect of NA on the crystallization kinetics of PLA and PLA/PBS blend was investigated using a differential scanning calorimeter, a polarized optical microscope and a wideangle X-ray diffractometer. The crystallization rate of PLA component in PLA/PBS blends is increased effectively by NA through fast nucleation and growth rate of PLA α'-form crystal, which is confirmed by isothermal crystallization behavior of PLA/PBA/NA composites. The isothermal crystallization results also show that the incorporation of NA induces heterogeneous nucleation mechanism in PLA component. The increased number of crystal nuclei hinders the increase of average grain size of PLA component in composites but contributes to a higher crystallinity of both PLA and PBS components in PLA/PBS blends. Finally, the mechanical properties and dynamic mechanical properties of PLA/PBS/NA composites are improved because of the increased crystallinity, which are superior to that of PLA/PBS blend.

Enhancement of mechanical, thermal and morphological properties of compatibilized graphene reinforced dynamically vulcanized thermoplastic elastomer vulcanizates based on polyethylene and reclaimed rubber

The effect of graphene nanoplatelets (GnPs) introduction into the compatibilized multiphase polymer systems such as dynamically vulcanized thermoplastic elastomers (TPVs) based on linear low density polyethylene (LLDPE) and reclaimed rubber (RR) was explored through using the experimental and theoretical analysis. The nanocomposites were prepared by using traditional melt mixing method and characterized by various experimental measurements including transmission electron microscopy (TEM), scanning electron microscopy (SEM), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), Dynamic mechanical thermal analysis (DMTA), tensile test and rheological measurements. The morphological investigations of prepared TPV nanocomposites show the considerable effect of GnPs on the size reduction of rubber droplets. The DSC measurements indicated the role of GnPs as an effective nucleating agent in the TPV nanocomposites. The results of TGA measurements show that the GnPs can cause a higher thermal stability in LLDPE/RR TPVs especially in the presence of a maleated polyethylene (MA-PE) as a compatibilizer. The mechanical properties exploration of TPV nanocomposites represents the considerable effect of GnPs on the increasing of Young's modulus. The analytical stiffness analysis through using Christensen-Lo model with emphasizing the effect of interphase region could precisely predict the effect of various GnPs loading on the Young's modulus. Fabrication of an industrial applicable TPV nanocomposites with enhanced mechanical, thermal and morphological properties could be achieved by using both the proper loadings of GnPs and compatibilizer.