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Using benzoyl hydrazide and benzoyl chloride with different end-capping structures, three kinds of organic hydrazide nucleating agents, 1, 4-dibenzoyl p-phenylhydrazide (BTAD), 1, 4-bis(4-methylbenzoyl) p-phenylhydrazide (BTAD-CH3) and 1, 4-bis(4-tert-butylbenzoyl) p-phenylhydrazide [BTAD-(CH3)3], were prepared by coupling reaction. Their effects on crystallization behavior, mechanical properties and heat resistance of polyethylene terephthalate (PET) were also discussed. The results show that when the addition of nuclearing agents BTAD, BTAD-CH3 and BTAD-(CH3)3 are 1.0%, the crystallization peak temperature (Tc) of PET is increased by 51, 53, 56 °C, respectively, and the crystallinity (Xc) is increased from 18.1% to 26.3%, 26.9% and 29.7%, respectively. BTAD-(CH3)3 can further refine the size of PET spherulite and show better nucleation effect. When BTAD-(CH3)3 is added at 2.0%, the bending modulus of PET composites is increased to 2 675 MPa, with an increase of 22%, and the Vicat softening temperature and thermal deformation temperature are increased by 60 °C and 10 °C, respectively, compared with PET, and the mechanical properties and heat resistance are improved. [ABSTRACT FROM AUTHOR]

A linear diamides derivative (TMC-300) was incorporated into biosourced and biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) to investigate the influence of TMC-300 on the crystallization and rheological properties of P34HB. TMC-300 displayed an outstanding nucleating effect on P34HB. Adding 0.5 mass% TMC-300 increased the non-isothermal crystallization temperature by about 20 °C at rate of 5 °C min−1. Isothermal crystallization half-time at 95 °C obviously decreased from 20 min for neat P34HB to 2.5 min for P34HB/0.2TMC. Adding TMC-300 dramatically increased nucleation density and reduced spherulite size. Moreover, the rheological properties were obviously enhanced by adding TMC-300. The most intriguing result was that percolation network was formed at TMC-300 content between 0.5 and 1 mass%, which led to the transition of melt behaviors from liquid-like to solid-like. The unusual combination of nucleating effect and rheological properties promotion of TMC-300 on P34HB was in great potential for expanding practical application of biosourced and biodegradable P34HB. [ABSTRACT FROM AUTHOR]

The main purpose of this work is to present the effect of long-chain branching and specific α-nucleation on the optical properties, crystallization and supermolecular structure of polypropylene (PP). Commercially available α-nucleating/ clarifying agent 1,3;2,4-bis(3,4-dimethylbenzylidene)sorbitol (Millad 3988) was mixed into linear PP and long-chain branched PP (LCB-PP) in the concentration of 0.2 wt%. For the study of polymorphic composition, crystallinity, and crystallization process under isothermal conditions in the temperature range of 130-150 °C, differential scanning calorimetry and wide-angle X-ray scattering were used. Although the used nucleating/clarifying agent appears to have a slight effect on the optical properties of long-chain branched polypropylene, it does not appear to affect the crystallization kinetics significantly. LCB-PP exhibited self-nucleation, favored over nucleation by a specific nucleating agent. [ABSTRACT FROM AUTHOR]

Nucleation efficiency and the special supermolecular structure formed in the presence of novel nucleating agents, N,N′-dicyclohexylsuberoylamide and N,N′-dicyclohexylsebacoylamide are presented in this work. The nucleation effect is studied in isotactic polypropylene (iPP). The melting and crystallization processes as well as the polymorphic composition are studied using calorimetric and thermo-optical techniques, while the solubility of the nucleating agents is studied by rheology. The properties of the iPP products nucleated by the novel compounds are characterized by conventional tensile and impact tests and the optical properties are measured by standardized haze measurements. The results indicated clearly that the studied nucleating agents are partially soluble in the iPP melt and possess dual nucleating ability. The formation of β-phase is evidenced by the calorimetric and thermo-optical measurements. The morphology of the nucleated samples shows similarity to iPP nucleated by well-known soluble "organogelators"; however, the nucleating agents introduced in this work are the first "organogelators" with β-nucleating efficiency. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The relation between chemical structure of branched amide compounds as nucleating agents and the nucleation effect of them in isotactic polypropylene (iPP) was investigated through studying the crystallization and melting behavior of iPP nucleated with these nucleating agents by differential scanning calorimetry (DSC). The crystallization peak temperature (Tc) of nucleated iPP had different degrees of increase after the amide groups were introduced into the benzene ring. The nucleation efficiency of 1,3,5-benzenetrisamide was superior to that of terephthalamide due to the existence of benzamide. At the same time, the nucleation effect of different side chain-substituted amide compounds on iPP was investigated. The results showed that the crystallization peak temperature of iPP nucleated with ring-substituted amides was higher than that of iPP nucleated with chain-substituted amides, that of the 6-membered ring-substituted amides was better than that of the five-membered ring-substituted amides and that of the cyclohexyl group substitution was superior to that of the benzene ring. Besides, the amide compounds with different central group were also studied as iPP nucleating agents. The results show that the sequence of nucleating efficiency from high to low is six carbons > benzene > ten carbons. In addition, the optimum contents of 1,3,5-benzenetricarboxylic acid tris(cyclopentylamine) (BTA-CP), 1,3,5-benzenetricarboxylic acid tris(tert-pentylamine) (BTA-TP) and 1,3,5-benzenetricarboxylic acid tris(iso-pentylamine) (BTA-IP) in iPP were 0.20 mass%, 0.20 mass% and 0.15 mass%, respectively. Under the optimum content of BTA-CP, BTA-TP and BTA-IP, the crystallization peak temperature of nucleated iPP was increased from 117.6 °C of pure iPP to 127.2°C, 125.7°C and 123.4 °C, respectively. [ABSTRACT FROM AUTHOR]

A series of dicarboxylic dihydrazide compounds (DCDH-R-n) were prepared and used as nucleating agents for isotactic polypropylene (iPP). To investigate the relation between chemical structure of nucleating agents and nucleation effect in iPP, the influences of DCDH-R-n on crystallization and melting behaviors of iPP were analyzed by differential scanning calorimeter. The results showed some of dicarboxylic dihydrazide compounds were highly efficient for iPP. The nucleation efficiency of these nucleating agents depended on different substituent groups (R) and the number of methylene groups (n). When R is phenyl or cyclohexyl, the corresponding nucleating agents had relatively excellent nucleation effect. A nucleating agent was likely to have better nucleation effect as the number of methylene groups in the structure increases. In addition, the optimum addition amount of DCDH-R-n in iPP ranged from 0.10 to 0.20 mass% and the crystallization temperatures of nucleated iPP under optimum addition amount reached above 130.0 °C. [ABSTRACT FROM AUTHOR]

The nucleation efficiency (NE) of stereocomplex crystallites (SCs) formed in asymmetric poly(L‐lactide)/poly(D‐lactide) (PLLA/PDLA) blends is generally unsatisfactory because the competition between stereocomplexation and chain mixing involved in the melt‐mixing process can cause low formation efficiency and even severe aggregation of SCs. Herein, it is attempted to achieve high‐efficient formation of finely dispersed SCs particles by designing a unique melt‐mixing procedure, where the mixing of PLLA with 0.75 wt% PDLA is first performed at elevated temperatures (far above the melting temperature of SCs) to allow the homogeneous mixing of PLLA/PDLA chains and then at a low temperature (slightly above that of homocrystallites) to permit the full stereocomplexation of the premixed chains. It is found that the SCs formed in the blends exhibit unexpectedly low NEs (e.g., 54.5%), much inferior to that (73.6%) in the counterpart without undergoing premixing. This is because the introduction of premixing leads to a remarkable deterioration in the amount of SCs particles formed, despite decreased particle size, highlighting that the direct mixing at low temperatures of 170–180 °C (about 20–30 °C lower than that used in common melt‐processing of PLA) is more effective for the construction of SCs with superior NE. The mechanisms for these striking findings are discussed. [ABSTRACT FROM AUTHOR]

The mechanism of nucleating agents (NAs) accelerating the crystallization of semi-crystalline polymers has received continuous attention due to the extreme importance in academic research and industry application. In this work, the nucleation effect and probable mechanism of 1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol (DMDBS) on promoting the crystallization of syndiotactic polypropylene (sPP) was systematically investigated. Our results showed that DMDBS could significantly accelerate the crystallization process and did not change the crystalline form of sPP. The in situ infrared spectra recorded in the crystallization process showed that in pristine sPP the tttt conformers decreased and the ttgg conformers increased subsequently. In sPP/DMDBS system, DMDBS could promote the increase of ttgg conformers rather than the decrease of tttt conformers. The further analysis by 2D-IR spectra revealed that ttgg conformers increased prior to the decrease of tttt conformers in the sPP/DMDBS system comparing with pristine sPP. Considering that ttgg conformers were basic elements of helical conformation of Form I crystal for sPP, we proposed a probable nucleation mechanism of DMDBS for sPP:DMDBS could stabilize the ttgg conformers which induced these ttgg conformers to pre-orientate and aggregate into helical conformation sequences as initial nuclei quickly and early to promote the sPP crystallization. Our work provides some new insights into the nucleation mechanism of NAs for sPP. [ABSTRACT FROM AUTHOR]

Green and renewable foaming poly(lactic acid) (PLA) represents one of the promising developments in PLA materials. This study is the first to use the lignin graft PLA copolymer (LG‐g‐PLA) to improve the foamability of PLA as a biobased nucleating agent. This agent was synthesized via ring‐opening polymerization of lignin and lactide. The effects of LG‐g‐PLA on cell nucleation induced by the crystallization, rheological behavior, and foamability of PLA were evaluated. Results indicated that LG‐g‐PLA can improve the crystallization rate and crystallinity of PLA, and play a significant nucleation role in the microcellular foam processing of PLA. LG‐g‐PLA improved the foam morphology of PLA, obtaining a reduced and uniform cell size as well as increased expansion ratio and cell density. With the addition of 3 wt% LG‐g‐PLA content, the PLA/LG‐g‐PLA foams increased the compressive strength 1.6 times than that of neat PLA foams. The improved foaming properties of PLA via a biobased nucleating agent show potential for the production and application of green biodegradable foams. [ABSTRACT FROM AUTHOR]

Addition of an α‐nucleating agent is the simple and effective method to increase nucleation efficiency of isotactic polypropylene (iPP). However, severe agglomeration and poor dispersibility of sodium 2,2′‐methylene‐bis(4,6‐di‐tertbutylphenyl) phosphate (NA11) decrease the nucleation efficiency in the iPP, and much more nucleating agent is needed to maintain the nucleating property. As a result, it becomes the key how to decrease the size of NA11 and increase the nucleating property. In this paper, zeolite 4A (Z4A) was firstly supported by NA11 through solution impregnation, and NA11 was dispersed by Z4A depending on the dispersion of zeolite as carrier for the second component. Then, the dispersed NA11 system (NA11‐Z4A) exhibited a superior nucleation behavior during the crystallization of the iPP matrix when it was used with iPP together. The isothermal and nonisothermal crystallization kinetics indicated that the NA11‐Z4A/iPP system had the best crystallization effect. Polarized optical microscopy (POM) and scanning electron microscopy (SEM) analyses showed that the size of NA11 decreased obviously when it was adsorbed on the surface of Z4A, which leads a better dispersibility of the nucleating agent and thus an accelerated nucleation process in the iPP matrix. In the end, the mechanism for the excellent dispersibility of NA11‐Z4A, which was based on hydrogen bonding between NA11 and Z4A, was confirmed by Fourier‐transform infrared spectroscopy (FTIR). Based on the research work, the solution impregnation strategy can potentially be applied to other systems to inhibit the agglomeration and improve the dispersibility of additives in iPP. [ABSTRACT FROM AUTHOR]

A highly efficient compound nucleating agent of carboxylated graphene/calcium pimelate (Gra/CaPi) for isotactic polypropylene (iPP) was prepared. The structure of Gra/CaPi was investigated by Fourier-transform infrared spectroscopy. The effects of Gra/CaPi on the crystallization and melting behaviors and crystalline morphology of iPP were investigated by differential scanning calorimetry, wide-angle X-ray diffraction and polarized optical microscopy. The results showed that CaPi and Gra were combined by chemical bonds, improved the dispersibility and nucleation ability of Gra in iPP. When the addition amount of Gra/CaPi in iPP was 0.3 mass%, the crystallization peak temperature was increased by 8.0 °C and the relative content of β-crystal in iPP reached up to 0.868 compared with that of pure iPP. [ABSTRACT FROM AUTHOR]

• Effect of β-nucleating agent on crystallization of post-consumer PP is studied. • Post-consumer PP with relative β-phase content higher than 0.80 is able to prepare. • It is possible to apply polymorphic modification in post-consumer PP recycling. The effect of two kinds of β-nucleating agents, an aryl amide derivative β-nucleating agent (TMB-5) and a rare earth complex (WBG), on crystallization of post-consumer polypropylene (PCW-PP) were investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (XRD) and polarized-light optical microscopy (POM). The results indicate that introduction of TMB-5 and WBG is able to increase the crystallization temperature of PCW-PP and to induce a large amount of β-crystals. TMB-5 has stronger β-nucleating effect than WBG at low content, while the β-nucleating effect of WBG exceeds that of TMB-5 at a content of about 0.7 wt%, referring to the calculated relative content of β-phase and the concentration of nuclei in PCW-PP. Through adding 0.3 wt% TMB-5 or 0.7 wt% WBG, PCW-PP with β-phase content higher than 0.80 can be prepared, which provides a promising method to realize high-value added recycling of PCW-PP. [ABSTRACT FROM AUTHOR]

A simple method was used to prepare microcellular foams of poly(lactic acid) (PLA) and its nanocomposites to improve its shortcomings such as low impact resistance and high cost. The batch foaming process of pure PLA and PLA filled with Nano calcium carbonate (NCC) was conducted using supercritical nitrogen (N2) as a blowing agent. The effect of NCC on crystallization of PLA is discussed as a remarkable parameter in foaming of semicrystalline polymers. Differential scanning calorimetry (DSC) was used to optimize the process temperature. The effect of foaming conditions (temperature, pressure, and cooling rate) and nanoparticle content on the foam microstructure of PLA and its nanocomposites were investigated using scanning electron microscopy (SEM). Foams were obtained in the range of macro‐ and microscale (different cell sizes) using different foaming conditions. The results revealed that nanoparticles show excellent nucleation performance on PLA foaming. Results of dynamic mechanical thermal analysis (DMTA) also showed significant influences of NCC on foamed and prefoamed samples to different foaming structures. [ABSTRACT FROM AUTHOR]

Addition of a β-nucleating agent (β-NA) is the most effective method of preparing β-nucleated isotactic polypropylene (β-iPP); however, the poor dispersion and agglomeration of β-NAs limit nucleation efficiency. To solve this problem, a self-dispersing β-NA strategy was developed based on in situ preparation of β-NA (instead of pre-addition) during the processing of iPP. Zinc adipate (ZnAA), a typical β-NA, was chosen; self-dispersed ZnAA (ZnAA(IS)) was prepared in situ from its reaction precursors adipic acid (AA) and zinc oxide (ZnO) during extrusion of iPP. In situ preparation of ZnAA(IS) led to a significantly higher nucleation efficiency than pre-addition of ZnAA. The β-crystal content ( k β value) of nucleated iPP prepared with ZnAA(IS) reached 0.99, significantly higher than iPP prepared with ZnAA. Moreover, the impact strength of 0.1 wt % ZnAA(IS)/iPP composites was nearly 5.3-fold higher than neat iPP with a net gain in reinforcement (157%) compared to pre-addition of ZnAA. To explain these phenomena, we proposed mechanism for the self-dispersion of β-NA in the context of in situ generation of β-NA during iPP processing; the mechanism was confirmed by Fourier Transform Infrared Spectroscopy (FTIR), Polarized Optical Microscopy (POM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) data. Therefore, this strategy and method of preparing β-NA in situ offers unique advantages that will advance the production and application of β-iPP. Furthermore, this strategy could potentially be extended to solve issues of poor dispersion and agglomeration for other additives. [ABSTRACT FROM AUTHOR]

Abstract: Crystallophores are lanthanide complexes that act as powerful auxiliary for protein crystallography due to their strong nucleating and phasing effects. To get first insights on the mechanisms behind nucleation induced by Crystallophore, we systematically identified various elaborated networks of supramolecular interactions between Tb‐Xo4 and subset of 6 protein structures determined by X‐ray diffraction in complex with terbium–Crystallophore (Tb‐Xo4). Such interaction mapping analyses demonstrate the versatile binding behavior of the Crystallophore and pave the way to a better understanding of its unique properties. [ABSTRACT FROM AUTHOR]

The thermal stability of nucleation effect of three highly effective β-nucleating agents, namely an aryl diamide-based nucleating agent (TMB-5), a rare earth complex (WBG-II), and calcium pimelate (Ca-Pi) in isotactic polypropylene (iPP) was investigated by DSC multi-scanning cycles. All three nucleating agents induced iPP to form high contents of β-crystals. After several thermal cycles, the relative content of β-phase crystals (KDSC) in the nucleated iPP was decreased and the crystallization peak temperature (Tcp) was also decreased. The KDSC and Tcp of iPP nucleated with TMB-5, WBG-II, and Ca-Pi were decreased by 0.0477, 0.1257, 0.0603, and 0.97, 2.71, 1.18 °C, respectively. It indicated that the nucleation effect became worse. The nucleation effect of TMB-5 decreased less while that of WBG-II and Ca-Pi was significantly reduced. Thus, the orders of thermal stability for nucleation effect of these three nucleating agents were TMB-5 > Ca-Pi > WBG-II. [ABSTRACT FROM AUTHOR]

Adding β nucleating agent (β-NA) is the most effective way to induce β-form in isotactic polypropylene (iPP). However, the problem of agglomeration and poor dispersion result in the low nucleation efficiency of β-NA. We reported herein a novel self-dispersed β nucleating agent of iPP, zinc salt of bicycle [2.2.1] hept-5-ene-2-dodecanamide-3-carboxylate (NBDA30), which exhibited a unique nucleation behavior during the crystallization of iPP. The results showed that the content of β crystal of iPP nucleated with 0.2 wt% NBDA30 can reach 0.82 (k β value), implying that NBDA30 is an effective β nucleating agent of iPP. Polarized optical microscopy (POM) analyses showed that the NBDA30 gradually melted upon increasing temperature and then the melt induced the crystallization of iPP. The unique nucleation behavior was first reported in this study and the nucleation mechanism of iPP induced by NBDA30 was revealed by POM, fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), transmission electron microscopy (TEM) and scanning electron Microscope (SEM). The results indicated that the NBDA30 was converted into ZnO nanoparticles and the group of ROO¯ chemically adsorbed on the surface of ZnO nanoparticles (NPs). The problem of agglomeration of ZnO nanoparticles was well solved by in situ thermal decomposition of NBDA30 and the compatibility of ZnO and iPP matrix was greatly improved by chemical adsorption of organic carboxylic acid on the surface of ZnO NPs. Therefore, the nucleation efficiency of ZnO NPs was greatly increased. The preparation method of self-dispersed nucleating agent can potentially be extended to other nucleating agent or additives to prevent them from aggregating. [ABSTRACT FROM AUTHOR]

the relationship between side chain isomerism of aliphatic C4 substituted 1,3,5-benzenetricarboxylamides (BTA-Rs, 1,3,5-benzenetricarboxylic acid tris( tert -butylamide) (BTA-TB), 1,3,5-benzenetricarboxylic acid tris(iso-butylamide) (BTA-IB) and 1,3,5-benzenetricarboxylic acid tris( n -butylamide) (BTA-NB)) and nucleation effects in iPP were investigated by differential scanning calorimeter (DSC), polarizing optical microscope (POM) and wide-angle X-ray diffractometer (WXRD). The results showed BTA-TB, BTA-NB and BTA-IB were efficient nucleating agents for iPP, and all of them induced formation of α-form spherulites and increased the crystallization peak temperature of iPP dramatically. However, BTA-NB had dual nucleation abilities for both α- and β-form crystals and induced iPP to form β-form spherulites at high content. The optimum contents of BTA-TB, BTA-NB and BTA-IB in iPP were 0.25 wt%, 0.3 wt% and 0.15 wt%, respectively. Under the optimum content the crystallization peak temperature of iPP nucleated with BTA-TB, BTA-NB and BTA-IB increased from 122.5 °C of neat iPP to 130.4 °C, 132.1 °C and 130.1 °C, respectively. [ABSTRACT FROM AUTHOR]

1,3,5-Benzenetricarboxylic acid tris(phenylamide) (hereinafter called as 'BTA-93') was synthesized and proved to be a highly efficient α-crystalline nucleating agent through investigation of crystallization and melting behaviors of nucleated isotactic polypropylene (iPP) by differential scanning calorimetry. The optimum addition amount of BTA-93 in iPP was 0.07 wt%. At this low addition amount, crystallization peak temperature of iPP was increased from 119.3 °C of neat iPP to 126 °C and the nucleation effect was comparable to that of a highly effective commercial nucleating agent disodium bicyclo [2.2.1] heptane dicarboxylate (HPN-68) at addition amount of 0.2 wt%. Furthermore, the crystal structure of BTA-93 was obtained by single crystal X-ray diffraction. The crystal data indicated that the b-direction of BTA-93 crystal was about four times of 0.655 nm which was the cell edge of (010) plane, and the lattice mismatch degree was 2.81%. The outstanding nucleation efficiency of BTA-93 in iPP could relate to the lattice matching between BTA-93 and α-iPP crystals. [ABSTRACT FROM AUTHOR]

We used an innovative visualization mold to investigate the effect of foam processing parameters on bubble nucleation and growth. This was also done to uncover the mechanisms responsible for cellular structural development in the high-pressure foam injection molding process. The effects of the injection speed, the injection gate geometry, the blowing agent content, the melt flow rate and the use of talc as a heterogeneous nucleating agent on the formation and dynamics of cell bubbles were all explored. In the high-pressure foam injection molding process with a proper packing pressure, the overall cell density did not change with the injection speed nor with the injection gate resistance. However, the cell density increased significantly with the blowing agent's concentration and with a nucleating agent. We also observed the growth mechanism of the bubbles in a confined mold cavity, and concluded that the bubble growth rate decreased as the cell density increased. In addition, the satelliting phenomenon, i.e. bubble nucleation around the previously nucleated cells, was observed. This was due to the induced stress fluctuations in the surrounding melt, which could eventually affect the final cellular structure. [ABSTRACT FROM AUTHOR]

An attempt to prepare graft copolymer of natural rubber, NR and poly(stearyl methacrylate), PSMA, was made to improve mechanical properties of NR, since the grafted PSMA was composed of crystallizable stearyl groups as a nucleating agent and methacrylate units. The graft-copolymerization of stearyl methacrylate (SMA) onto deproteinized natural rubber (DPNR) was performed in latex stage with tert -butylhydroperoxide (TBHP)/tetraethylenepentamine (TEPA) as an initiator, after purifying the rubber with urea and sodium dodecyl sulphate followed by centrifugation. The optimal conditions for the graft-copolymerization were determined as follows: 3.3 × 10 −2 mol/kg-rubber of initiator, 1.5 mol/kg-rubber of monomer and 30 w/w% of dry rubber content (DRC). The conversion and grafting efficiency of SMA were 95 mol% and 60 mol%, respectively. After graft-copolymerization, the melting temperature of PSMA increased from 304.1 K to 306.2 K. The morphology showed that the DPNR particles, which were about 1 μm in average diameter, were well dispersed in PSMA nanomatrix. The stress at break increased about three times, i.e. 13 MPa, as high as that of DPNR. The increase in the mechanical properties was promoted by the nucleating effect of stearyl group of PSMA. [ABSTRACT FROM AUTHOR]

In this study, a bio-based branched polymer bearing a castor oil core was synthesized, and the nucleating effect of the branched polymer on the crystallization of poly( l-lactic acid) (PLLA) was investigated by a differential scanning calorimetry and a polarized optical microscopy. The bio-based branched polymer was synthesized by ring-opening polymerization of l-lactide using castor oil core as an initiator, and subsequently modification of terminal groups was performed. A small amount of the trimellitoyl-terminated branched polymer accelerated the crystallization of PLLA, and the crystallization half time was dependent on the molecular weight of the branched polymer. By the addition of the branched polymer, the spherulite size of PLLA became much smaller than that of neat PLLA. Furthermore, the strain at break of PLLA containing the branched polymer was improved, compared with that of neat PLLA. [ABSTRACT FROM AUTHOR]

Copyright of Polimery is the property of Industrial Chemistry Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nucleation is one of the primary contributions to the microstructure of glass-ceramics. However, the nucleation process within glass-ceramics is not understood across all glass systems, nor is the specific role of nucleating agents. The present article proposes a comprehensive definition of a nucleating agent: " a nucleating agent is a minority component of the glass composition that leads to increased internal nucleation rates or precipitation and control of desired crystal phases, either by lowering the thermodynamic or the kinetic barrier for nucleation, or some combination thereof ". We also examine the role that five important nucleating agents (TiO 2 , ZrO 2 , MoO 3 , P 2 O 5 , and OH−) play in different systems, particularly in their effect on the thermodynamics and kinetics of the nucleation process. We argue that nucleating agents help control the nucleation process either by decreasing the thermodynamic or kinetic barrier or some combination of the two and provide a method to distinguish their effect. [ABSTRACT FROM AUTHOR]

An aryl amide derivative (TMB-5) was used to nucleate the poly( l -lactide)/poly( d -lactide) (PLLA/PDLA) blend for the first time. The effect of TMB-5 nucleating agent on the crystallization behavior of PLLA/PDLA blend was systematically investigated. The selective nucleation of stereocomplex (sc) crystals by incorporation of TMB-5 was realized under appropriate crystallization conditions. During the cooling process, various morphology of TMB-5 due to its partial or complete dissolution in the PLLA/PDLA blend melt was observed. Furthermore, an sc crystals layer on the lateral surface of TMB-5 was found. Upon cooling a PLLA/PDLA blend from 260 °C at rates between 2 and 100 °C/min, 0.5 wt% addition of TMB-5 induced a single melting peak of sc crystals and no homocrystallization was observed in the subsequent DSC heating scan. The melting temperature of the sc crystals was found to decrease in the presence of TMB-5 from 230 to ca. 200 °C, which is still 20 °C higher than that of PLLA homopolymer. The results suggest that the supramolecular structure of the nucleating agent plays an important role in the crystallization of the PLLA/PDLA blend. The difference in solubility and recrystallization ability of TMB-5 in polymer melt results in the variation of crystallization behavior of PLLA/PDLA blend, which is correlated with the concentration of TMB-5 and crystallization conditions including the final melting temperature, annealing time and cooling rate. [ABSTRACT FROM AUTHOR]

The effect of cadmium phenylmalonate (PMA-Cd) as a novel nucleating agent on the crystallization behaviors and spherulitic morphology of poly(lactic acid) (PLA) as well as non-isothermal crystallization kinetics of the nucleated PLA were studied by means of differential scanning calorimetry and polarized light microscopy. The results showed that PMA-Cd served as an effective nucleating agent to accelerate the crystallization rate of PLA. The presence of PMA-Cd significantly increased the number and decreased the size of the spherulites. The non-isothermal crystallization kinetics of the nucleated PLA was well described by Mo's model. The activation energies (Δ E) of non-isothermal crystallization were calculated by Kissinger's method. The crystallization rate of PLA/0.5 % PMA-Cd sample was faster than that of PLA/0.2 % PMA-Cd sample, while the Δ E of the former was greater than that of the latter. The nucleation mechanism between PMA-Cd and PLA was satisfactorily explained by dimensional lattice-matching criterion. [ABSTRACT FROM AUTHOR]

Microencapsulated phase change materials (PCM) must not experience any supercooling, otherwise cannot be used in any latent heat applications. In this study Rubitherm ® RT58 and1-octadecanol were selected as nucleating agents in an attempt to reduce or eliminate the supercooling issue of PCM in microcapsules. The PCM microcapsules (PCMMC) were prepared using a suspension polymerization. Fourier transformed infrared (FT-IR) measurements confirmed that RT21 has been successfully encapsulated. Differential Scanning Calorimetry (DSC) shows that the onset crystallization temperature of PCMMC was approximately 10 °C lower than that of the non-encapsulated RT21, due to supercooling. The degree of supercooling has been reduced dramatically when either RT58 or 1-octadecanol was used. However, the addition of 1-octadecanol has a negative impact on the PCM thermal behaviour, which represented by spreading the solidification over wider range of temperature. PCM content in the microcapsule was determined using Thermal Gravimetric Analysis (TGA) and DSC measurements. TGA provided more accurate measure of the core material mass content, since the DSC measurement assume no change in the latent heat of the PCM due to the addition nucleating agent, which may not be true. SEM shows that the surface morphology of the PCMMC without a nucleating agent is a smooth. However, buckles and dimples were observed on the surface of the PCMMC when nucleating agent was introduced. The mass loss, when the capsules were place at 50 °C in oven, was higher and more significant when 1-octadecanol was added as a nucleating agent. In contrast, when Rubitherm ® RT58 was used, the mass loss of the PCMMC was small and stabilized after a short period of time. The latent heat of fusion and phase transition temperatures of PCMMC containing 5 wt. % RT58 were stable even after 2000 thermal recycle. [ABSTRACT FROM AUTHOR]

The incorporation of nanoparticles to polymer foams not only reinforces the cell walls and struts but can also lead to a decrease of cell size and enhanced cell morphology which in turn, yield foams with superior mechanical properties. For this purpose, several studies have focused on identifying close-to-ideal nucleating agents as well as understanding the influence of processing parameters on foam cell morphology. [ABSTRACT FROM AUTHOR]

We describe the ultrasonic initiated modification of four types of oil; sunflower oil, transformer oil, cable oil and silicone oil. Ultrasound is effective in initiating and driving reactions of the three hydrocarbon oils but ineffective in the case of silicone oil. The hydrocarbon oils showed noticeable reductions in viscosity after sonication; this reduction can be enhanced by incorporating nucleating agents such as particulate carbon. The viscosity loss is not permanent without using stabilisers and with time the viscosity approaches its initial value. The ultrasonic reaction is thought to be free radical in nature, since incorporation of a radical scavenger before sonication prevents any viscosity loss, whereas incorporation after sonication stabilises the drop in viscosity. Oxygen is proposed to be involved since purging with nitrogen diminishes any viscosity drop observed, and selected ion flow tube MS analysis of volatiles from the oils after sonication indicates an increase in the number and quantity of oxidised products. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Glass stability (GS) parameters based on typical temperatures obtained by differential thermal analysis were determined for glasses composed of Li 2 O:BaO:SiO 2 :nucleant, using TiO 2 , V 2 O 5 , ZrO 2 and Nb 2 O 5 as nucleants. The GS parameter proposed by Saad and Poulain, S , showed values of 21.26 for ZrO 2 , 13.77 for Nb 2 O 5 , 11.42 in the glass without nucleating agent, 6.91 for V 2 O 5 and 6.29 in that containing TiO 2 . GS was also inferred from the apparent activation energy of crystallization, A E , and these values of the compositions, in kJ mol − 1 , were 355 in the glass without nucleating agent, 322 for TiO 2 , 254 for ZrO 2 , 278 for V 2 O 5 and 300 for Nb 2 O 5 . A surface crystallization mechanism was observed, and thermal treatment yielded crystalline Li 2 Si 2 O 5 and Li 2 SiO 3 . The time–temperature–transformation diagrams, TTT diagrams, were consistent with the obtained GS parameters. [ABSTRACT FROM AUTHOR]

Isotactic polypropylene (iPP) has been modified with various nucleating agents, based on layered metal monoglycerolate complexes. Increased crystallisation temperatures (T c ) of iPP were observed in the presence of the isostructural zinc and cobalt layered monoglycerolates (ZMG & CoMG) and the structurally-related calcium monoglycerolate (CaMG), at loadings as low as 200 ppm, indicating highly effective nucleation. Optical microscopic observations showed that iPP nucleates from the thin edges/sides of CoMG and not from the larger area flat hexagonal/rhombic surfaces of the platelets. X-ray powder diffraction (XRD) studies revealed predominantly selective α-nucleation, although small amounts of the β-phase were observed with CaMG/iPP. The (040) peak of α-phase of iPP was enhanced for nucleated injection moulded samples. Molecular modelling indicated a close structural match between the edges of nucleating platelets and α-iPP in multiple lattice directions, each with a dimensional mismatch of less than 4%. [ABSTRACT FROM AUTHOR]

To control the influence of supercooling on the preparation of poly(vinyl alcohol) (PVA) cryogel, various biocompatible ice nucleating agents, including, two fatty alcohols, and eight different amino acids are investigated for their ice nucleating efficiency in PVA aqueous solutions. The L-aspartic acid is found to be the most efficient ice nucleating agent with the ability to induce freezing at ∼−5.5 °C in 8.3 wt% aqueous PVA solution as compared to ∼−20 °C without L-aspartic acid. The PVA cryogels are prepared with L-aspartic acid as the heterogeneous ice nucleating agent and investigated for their rheological properties. Finally, it is found that freezing temperature close to the sol-gel transition temperature produces cryogel with the high tack important for various biomedical applications. [ABSTRACT FROM AUTHOR]

Nanoscale foaming using nucleating agents was modeled based on coarse-grained molecular dynamics simulations to analyze the nucleation and growth of nanocellular foams. Interactions between the polymer chains and nucleating agents, the blowing rate, and the number of nucleating agents were varied, and foam formation was analyzed. Snapshots of the simulated foamed structures were obtained and characteristic parameters—such as the number of foams and the size distribution of the foams—were estimated. In the case of weak attractive interactions between the polymers and nucleating agents, foams formed first at the interfaces of the polymers and nucleating agents, then formed in the polymer matrix. In the case of strong attractive interactions, foams originated only in the polymer matrix. These nucleation-type foams depended on the number and size of the foams, and on their growth and coalescence. Our simulations indicate that the foamed structures can be modulated by the following parameters: interactions between the polymer chains and nucleating agents, the blowing rate, and the number of nucleating agents. [Display omitted] • Nanocellular foaming with nucleating agents was simulated using coarse-grained model. • Nucleation, growth, and coalescence of nano foams can be reproduced by simulations. • Foaming mechanism was changed by interactions between polymers and nucleating agents. • There are two mechanisms: Foaming from nucleating agents and foaming within matrix. [ABSTRACT FROM AUTHOR]

Addition of a commercial available multiamide compound (N,N′,N′′-tricyclohexyl-1,3,5- benzenetricarboxylamide, defined here as TMC) into ecofriendly poly(lactic acid) (PLA) can accelerate the crystallization rate of the material remarkably and broaden its applications. In this paper, the nonisothermal crystallization behavior of biodegradable PLA nucleated by 0.3 wt.% of TMC was investigated by differential scanning calorimetry (DSC). The modified Avrami, Tobin, Ozawa, and Mo models were applied to describe the kinetics of the crystallization process. Various parameters of nonisothermal crystallization, such as the crystallization half-time and crystallization rate constant, reflected that TMC significantly accelerated the crystallization process. The activation energy values of the neat PLA and PLA/TMC blend, determined by the Kissinger method, increased with the addition of TMC. The study should be helpful for understanding the relationship between processing and properties of this material. [ABSTRACT FROM AUTHOR]

Abstract: In the preparation of glass–ceramics, bulk crystallization of glasses can be improved by adding nucleating agents. However, surface crystallization of glasses conventionally can only be enhanced by using small particles, whose surfaces provide nucleating sites. Herein, oxide nucleating agents such as TiO2 and Cr2O3 which are normally used to improve bulk crystallization were introduced into a lithium–iron-phosphate (LIP) glass. Differential thermal analysis results suggest that tendency to bulk crystallization of the LIP glass increases to some extent after addition of the nucleating agents. However, no bulk crystallization really occurred in the thermally treated samples. Instead, surface crystallization of the glass is facilitated by the nucleating agents. The samples containing nucleating agents show thicker crystallized surface layers compared with the pure LIP glass. It is proved nucleation stage to be important to increase the surface crystallization, further confirming the enhancement effect of the nucleating agents on surface crystallization. The results enrich the understanding of surface crystallization of glass and provide useful information for the preparation of glass–ceramics via glass powder sintering process which is based on surface crystallization. [Copyright &y& Elsevier]

The effect of processing conditions, nucleating agent and compatibilizer on the crystallinity, mechanical property and oxygen permeability of polypropylene was studied using differential scanning calorimetry, x-ray diffraction, thermogravimetric analysis and universal tensile testing. The as received polymer had much lower extent of crystallinity, which was enhanced to 58% by the processing and molding using either slow cooling or fast cooling conditions. Although the overall crystallinity was not affected by the rate of cooling, the crystallization behavior was, however, affected as indicated by different onset and peak crystallization temperatures as well as different crystallite sizes indicated by the differences in oxygen permeation and mechanical performance of the polymer. Nucleating agent further enhanced the extent of crystallinity (crystal plane peaks were shifted and broadened) and tensile modulus, but the polymer was observed to become brittle and had higher gas permeation through it. The compatibilizer, on the other hand, reduced the tensile modulus, but enhanced the yield strain owing to matrix plasticization and retained the similar oxygen permeation as the polymer. The temperature used during processing also affected the oxygen permeation and mechanical property as the high temperature may induce partial polymer degradation resulting in the reduction of molecular weight and deteriorated properties. [ABSTRACT FROM PUBLISHER]

The preparation of γ-phase in polypropylene is still an interesting issue in a long-term. In this work, we introduced a highly effective α-phase nucleating agent 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol derivatives (DMDBS) into polypropylene block copolymer (PPB) and investigated the crystallization behaviors of nucleated PPB sample under high pressure. The crystallization and melting behaviors of samples were characterized by differential scanning calorimetry, and the crystalline structure as well as the relative fraction of γ-phase in the sample was characterized by wide-angle X-ray diffraction (WAXD) and two-dimensional WAXD. Scanning electron microscope was used to characterize the supermolecular structure of samples. The results show that the effects of DMDBS and high pressure on crystallization behavior of PPB were dependent on the content of DMDBS. When the content of DMDBS is smaller than the critical value, there is a synergistic effect between DMDBS and high pressure to promote the formation of γ-phase. Specifically, the critical pressure under which γ-phase dominates completely is also decreased dramatically. When the content of DMDBS is higher than the critical value, there is a competition between the effect of DMDBS, which promotes the formation of α-phase and the effect of high pressure which promotes the formation of γ-phase. [ABSTRACT FROM AUTHOR]

The nucleating ability of p-cyclohexylamide carboxybenzene (β- NA) towards isotactic polypropylene ( iPP) was investigated by differential scanning calorimetry, X-ray diffraction, polarized optical microscopy and scanning electron microscopy. β- NA is identified to have dual nucleating ability for α- iPP and β- iPP under appropriate kinetic conditions. The formation of β- iPP is dependent on the content of β- NA. The content of β-phase can reach as high as 96.96% with the addition of only 0.05 wt% β- NA. Under non-isothermal crystallization the content of β- iPP increases with increasing cooling rate. The maximum β-crystal content is obtained at a cooling rate of 40 °C min-1. The supermolecular structure of the β- iPP is identified as a leaf-like transcrystalline structure with an ordered lamellae arrangement perpendicular to the special surface of β- NA. Under isothermal crystallization β-crystals can be formed in the temperature range 80-140 °C. The content of β-crystals reaches its maximum value at a crystallization temperature of 130 °C. © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The phase morphology and toughening behavior of impact polypropylene copolymer (IPC) with and without nucleating agent (NA), prepared at different processing melt temperatures ( Tp), were investigated. Interestingly, three different structures can be formed in the IPC samples by adding NA or tuning Tp. A well-defined core-shell structure is obtained in samples with α-NA or without NA prepared at all Tp. A developing multilayered structure is mainly formed at high Tp with added β-NA, while an incomplete phase separation structure with interpenetrating chains is the dominant structure for IPC samples prepared at low Tp with added β-NA. In this case, because of the synergistic effect between phase morphology and relatively high β-form crystal content, the chain interaction among the components and chain mobility of the amorphous portion of IPC are distinctly improved, resulting in a largely improved toughness under 0 °C. This improvement in toughness is very important for applications. © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: The present work proposes a simple preparation of multi-branched poly(l-lactic acid)s (m-PLLAs) and their performance as nucleating agents for PLA. By a simple polycondensation of l-lactic acid (l-LA) on the multi-functional core molecules of succinic acid (SA), malic acid (MA) and citric acid (CA) using stannous octanoate (SnOct2) as a catalyst, the m-PLLAs as two, three, and four branched PLLA can be obtained easily. Averagely, about 80% of the l-LA feed contents are successfully polymerized on core molecules. Non-isothermal crystallization studies of the PLA blend which contains 1 wt% m-PLLAs indicate that m-PLLAs induce the crystallization of PLA as evidenced from the decreases in glass transition temperature (T g) and crystallization temperature (T c), and the increase in degree of crystallinity (χ c) under the α-form of perfect crystalline in PLA. Isothermal crystallization studies related to Avrami exponent (n), kinetic constant (k) and crystallization half-time (t 1/2) indicate that the blend maintains its three-dimensional growth for the film thickness 0.05 mm, whereas the crystallization growth rate increases more than 4 times as observed from polarized optical microscope (POM). Among m-PLLA, the highest number of multi-branches with the shortest chain PLLA, i.e. CA-PLLA1, initiates the blends to increase its tensile strength and elongation at break for as high as 1.5 times and 1.2 times, respectively. [Copyright &y& Elsevier]

In this work, a novel nucleating agent (NA) based on substituted-aryl phosphate salts was introduced into poly(L-Lactide) (PLLA). The nonisothermal and isothermal crystallization behaviors of nucleated PLLA samples were investigated through differential scanning calorimetry (DSC), wide angle X-ray diffraction, and polarized optical microscope (POM). Furthermore, the effect of annealing treatment on the cold crystallization behaviors of nucleated samples was also investigated. The results show that the crystallization of PLLA, whether for the melt crystallization (including nonisothermal and isothermal crystallization process) or for the cold crystallization (including the cold crystallization occurring during the DSC heating process and during the annealing process), is greatly dependent upon the content of NA. At relatively lower NA content (≤0.1 wt%), the nucleation effect of NA is inconspicuous, however, at higher NA content (≥0.2 wt%), it exhibits great nucleation effect for the crystallization of PLLA. Further results show that the double endothermic peak of PLLA depends on the temperature applied for the crystallization. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Kevlar fiber [KF; poly( p-phenylene terephthalamide)] can be used as a reinforcing element to improve the mechanical properties of the resulting wood thermoplastic composites. This study was devised to investigate the effects of incorporation of KF on the isothermal crystallization kinetics of high-density polyethylene (HDPE) in the resulting composites using differential scanning calorimetry. Avrami model was applied to describe the isothermal crystallization process, and the fold surface-free energy was calculated according to the Hoffman-Lauritzen theory. Comparative study of neat HDPE, wood flour/HDPE composite (WPC), virgin KF-reinforced WPC (KFWPC), and grafted Kevlar fiber (GKF)-reinforced WPC (GKFWPC) showed that the overall crystallization rate, the activation energy, the equilibrium melting temperature, and the fold surface-free energy of the WPC were apparently changed due to the addition of KF; the crystallizability exhibited an order of KFWPC > GKFWPC > HDPE > WPC. The incorporation of virgin KF may cause the heterogeneous nucleation to induce a change in the crystal growth of HDPE from the tridimensional to bidimensional or to the mixed patterns. Avrami exponent values of the composites decreased with time, confirming the change of crystallization behavior. This study demonstrates that both the KF and GKF can act as nucleating agents to improve the crystallization rate of HDPE. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]