Study of the assembled morphology of aryl amide derivative and its influence on the nonisothermal crystallizations of isotactic polypropylene

Temperature Effects on the Crystalline Structure of iPP Containing Different Solvent-Treated TMB-5 Nucleating Agents

TMB-5 nucleating agent (NA) treated by different solvents were used as the β-NA of iPP. The effects of temperature on the crystalline structure of different iPP/TMB-5, as well as the crystallization and melting behaviors were investigated. It was found that strong polar solvent treated TMB-5 (TMB-5_DMSO and TMB-5_DMF) could induce more β-crystal at high T_c = 140 °C than the other TMB-5 NAs, while the β-crystal inducing efficiency of untreated TMB-5 (TMB-5_UT) and non-polar solvent treated TMB-5 (TMB-5_LP) is seriously reduced at high T_c = 140 °C. TMB-5_DMSO can induce a high and stable content of β-crystal with K_β = 83-94% within T_c = 90-140 °C, and TMB-5_ODCB can induce a high content of β-crystal with K_β > 91.3% within T_c = 90-130 °C. TMB-5_DMF is the most temperature-sensitive one, but can induce a high fraction of β-crystal with K_β > 92% both at low T_c = 90 °C and high T_c = 140 °C. High temperature pre-crystallization at T_pc = 150 °C tremendously reduces the β-crystal inducing efficiency of all TMB-5 NAs. TMB-5_UT and TMB-5_LP exhibit higher nucleating efficiency than TMB-5_DMSO, TMB-5_DMF and TMB-5_ODCB. During the non-isothermal crystallization process, TMB-5_UT induced β-crystal possesses higher structural perfection and stability, while TMB-5_LP is more likely to induce α-crystal with considerable quantity and stability. The structural perfection and stability of TMB-5 induced β-crystal can be enhanced with appropriate increasing of T_c.

Enhancing Crystallization and Toughness of Wood Flour/Polypropylene Composites via Matrix Crystalline Modification: A Comparative Study of Two β-Nucleating Agents

Incorporation of short wood fillers such as wood flour (WF) into polypropylene (PP) often results in a marked reduction of toughness, which is one of the main shortcomings for WF/PP composites. This research reports a facile approach to achieve toughening of WF/PP composites via introducing self-assembling β-nucleating agents into PP matrix. The effect of two kinds of nucleating agents, an aryl amide derivative (TMB5) and a rare earth complex (WBG II), at varying concentrations on the crystallization and mechanical properties of WF/PP composites was comparatively investigated. The results showed that both nucleating agents were highly effective in inducing β-crystal for WF/PP, with β-crystal content (k_β) value reaching 0.8 at 0.05 wt% nucleating agent concentration. The incorporation of TMB or WBG significantly decreased the spherulite size, increased the crystallization temperature and accelerated the crystallization process of WF/PP. As a result of PP crystalline modification, the toughness of composites was significantly improved. Through introducing 0.3 wt% TMB or WBG, the notched impact strength and strain at break of WF/PP increased by approximately 28% and 40%, respectively. Comparatively, although WF/PP-WBG had slightly higher K_β value than WF/PP-TMB at the same concentration, WF/PP/TMB exhibited more uniform crystalline morphology with smaller spherulites. Furthermore, the tensile strength and modulus of WF/PP-TMB were higher than WF/PP-WBG. This matrix crystalline modification strategy provides a promising route to prepare wood filler/thermoplastic composites with improved toughness and accelerated crystallization.

Crystalline modification of a rare earth nucleating agent for isotactic polypropylene based on its self-assembly

In this paper, the crystalline modification of a rare earth nucleating agent (WBG) for isotactic polypropylene (PP) based on its supramolecular self-assembly was investigated by differential scanning calorimetry, wide-angle X-ray diffraction and polarized optical microscopy. In addition, the relationship between the self-assembly structure of the nucleating agent and the crystalline structure, as well as the possible reason for the self-assembly behaviour, was further studied. The structure evolution of WBG showed that the self-assembly structure changed from a needle-like structure to a dendritic structure with increase in the content of WBG. When the content of WBG exceeded a critical value (0.4 wt%), it self-assembled into a strip structure. This revealed that the structure evolution of WBG contributed to the K_β and the crystallization morphology of PP with different content of WBG. In addition, further studies implied that the behaviour of self-assembly was a liquid-solid transformation of WBG, followed by a liquid-liquid phase separation of molten isotactic PP and WBG. The formation of the self-assembly structure was based on the free molecules by hydrogen bond dissociation while being heated, followed by aggregation into another structure by hydrogen bond association while being cooled. Furthermore, self-assembly behaviour depends largely on the interaction between WBG themselves.

An Effective α/β Nucleating Agent Compoundfor the Preparation of Polypropylene

The crystallization behavior and mechanical properties were investigated by mixing the traditional α-form nucleating agent (sodium benzoate, SB) and commercialized β-form nucleating agent (TMB-5) in isotactic polypropylene (iPP). Mechanical properties were evaluated by universal testing machines. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were conducted to illustrate the crystallization behavior. Polarized optical microscopy (POM) was adopted to observe the crystal morphologies. The experimental results show that the weight ratio of two types of nucleating agents determines the final crystal structure and mechanical properties of iPP. When the weight ratio of [SB] : [TMB-5] is 4 : 1, the impact strength and flexural modulus of iPP reach a maximum value. Compared with the single component β-form nucleating agent, the compound nucleating agent exhibits significant synergistic effect and shows better mechanical properties. It is expected that this new nucleation system will have potential industrial applications.

Toward Subtle Manipulation of Fine Dendritic β-Nucleating Agent in Polypropylene

Dendritic β-nucleating agent (β-NA) can readily manipulate the formation of dendritic β-crystal with a unique toughening effect on polypropylene (PP) to drastically enhance the ductility. However, by the current method, the geometric size is too large to fully perform the nucleating efficiency. In this study, by comparatively investigating the effect of molecular weight of PP and diffusion of β-NAs in a PP melt, we proposed a novel carrier strategy that selective enrichment of β-NAs in a PP carrier was followed by directed migration into polymer matrix. Accordingly, the growth of NAs was controlled by the release from the PP carrier, which decreased the available amount of β-NAs during the growth stage. In this case, the viscosity difference between PP carrier and matrix determined the interfacial movement of β-NAs. When the PP carrier and matrix had same molecular weight, the diffusion and release became favorable to facilitate the formation of the dense and fine dendritic aggregates. As a result, the relative content of β-crystals reached 92%, with a drastic increase of ∼82% in the optimal condition compared to the directed compounded PP/β-NAs sample. This study can open a new avenue to tailor the topologies of β-NAs and the ensuing β-crystals for high-performance PP products.

Nanocellulose-PE-b-PEG copolymer nanohybrid shish-kebab structure via interfacial crystallization

We report a novel nanohybrid shish-kebab (NHSK) architecture of cellulose nanofibers (CNFs) and a block copolymer, (polyethylene-b-polyethylene glycol) (PE-b-PEG). Cellulose microfibers were ultrasonically dispersed to generate cellulose nanofibers in the size range of 50±10nm in diameter, while the block copolymer was crystallized using a solution crystallization approach to prepare NHSK. This unique approach allows the flocculated NHSK product to transfer quickly from toluene to ethanol, in order to shorten the preparation time. Morphological analysis reveals, for the first time, that nanocellulose can be used to induce crystallization of a block copolymer to generate NHSK and trans-crystalline structure. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results reveals the crystal morphology and crystallinity changes by virtue of crystallization. The ordered periodic growth and alignment of polymer crystals is recognized as the virtue of molecular origin of extended polymer chains. The proposed hypothesis affords elucidation of NHSK architecture and promotes the designing of novel nanohybrids with controllable functionality.

Effective enhancement of the creep resistance in isotactic polypropylene by elevated concentrations of DMDBS

We present a method to improve the creep resistance of nucleated PP (polypropylene) by changing the crystalline structure.

Root-like glass fiber with branched fiber prepared via molecular self-assembly

In situ build root-like glass fiber (GF) via molecular self-assemble in polypropylene melts.

Effect of solubility of a hydrazide compound on the crystallization behavior of poly(l-lactide)

The influence of the annealing temperature on the solubility and nucleating efficiency of TMBH has been clarified.

Creep-resistant behavior of beta-polypropylene with different crystalline morphologies

This manuscript investigates the creep performance of β-iPP with different crystalline morphologies.

Melt recrystallization behavior of carbon-coated melt-drawn oriented isotactic polypropylene thin films

The melt recrystallization of vacuum carbon evaporated melt-drawn iPP thin films at varying melting temperature, melting time and recrystallization temperature was studied by means of transmission electron microscopy combined with electron diffraction.