Interfacial interaction in AI(OH)3/polypropylene composites modified by insitu‐functionalized polypropylene

To investigate the interfacial interaction of AI(OH)₃/polypropylene (PP) composites modified by in situ‐functionalized polypropylene (FPP), AI(OH)₃/polypropylene (PP) composites containing a low AI(OH)₃ content, modified by in situ‐grafted acrylic acid, were prepared by a one‐step melt‐extrusion process. The effect of in situ FPP on the crystallization and melting behavior, crystalline morphology of the composites, and interfacial interaction between the filler and PP was investigated. The crystallization and melting behavior and crystalline morphology of PP in the composites depended upon the interfacial physical [heterogeneous nucleation of AI(OH)₃; cocrystallization and compabilitization of PP with in situ FPP] and the interfacial chemical interaction between both the components in the composites. FTIR results indicated that there exists a chemical reaction between AI(OH)₃ and in situ FPP. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 110–120, 2002; DOI 10.1002/app.10270     

Thermal properties and flame retardance of Al(OH)3/polypropylene composites modified by polypropylene grafting with acrylic acid

The effect of polypropylene grafting with acrylic acid, PP‐g‐AA (FPP), on crystallization and melting behavior, thermal degradation, and limiting oxygen index of Al(OH)₃/PP composites were investigated. The results indicated that crystallization temperature of PP shifted to high temperature with increasing content of Al(OH)₃ because of the interfacial heterogeneous nucleation of Al(OH)₃ and further increased by the addition of FPP and with increasing FPP content because of the improvement of the dispersion of Al(OH)₃ in PP matrix and the increase in the nucleating sites of Al(OH)₃. With adding Al(OH)₃ and increasing the content of Al(OH)₃, limiting oxygen index values of composites increased and further improved by adding FPP. This is attributed to the presence of an interfacial interaction between FPP and Al(OH)₃. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2679–2686, 2001     

Crystallization and melt behavior of magnesium hydroxide/polypropylene composites modified by functionalized polypropylene

The crystallization and melting behavior of Mg(OH)₂/polypropylene (PP) composites modified by the addition of functionalized polypropylene (FPP) or acrylic acid (AA) and the formation of in situ FPP were investigated by DSC. The results indicated that addition of FPP increased crystallization temperatures of PP attributed to the nucleation effect of FPP. The formation of in situ FPP resulted in a reduced crystallization rate, melting point, and degree of crystallization because of the decreased regularity of the PP chain. For the Mg(OH)₂/PP composites, addition of Mg(OH)₂ increased the crystallization temperatures of PP attributed to a heterogeneous nucleation effect of Mg(OH)₂. Addition of FPP into Mg(OH)₂/PP composites further enhanced the crystallization temperatures of PP. It is suggested that there is an activation of FPP to the heterogeneous nucleation effect of Mg(OH)₂ surface. The addition of AA also increased the crystallization temperatures of PP in Mg(OH)₂/PP composites, but crystallization temperatures of PP were not influenced by the AA content, a phenomenon explained by the heterogeneous nucleation effect of the Mg(OH)₂ surface activated by FPP and AA. A synergistic effect on crystallization of PP in Mg(OH)₂/PP composites further increased the crystallization temperatures of PP. However, the crystallization temperatures of Mg(OH)₂/PP composites modified by in situ FPP were lower than those of Mg(OH)₂/PP composites modified by the addition of FPP or AA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:3899–3908, 2004     

Crystallization and melt behavior of Mg(OH)2/PP composites modified by functionalized polypropylene

The crystallization and melting behavior of Mg(OH)₂/PP composites modified by the addition of functionalized polypropylene (FPP) or acrylic acid (AA) and the formation of in situ FPP were investigated by DSC. The results indicated that addition of FPP increased the crystallization temperatures of PP because of the nucleation effect of FPP. The formation of in situ FPP resulted in a reduced crystallization rate, melting point, and degree of crystallization attributed to the decreased regularity of the PP chain. For Mg(OH)₂/PP composites, the addition of Mg(OH)₂ increased the crystallization temperatures of PP resulting from a heterogeneous nucleation effect of Mg(OH)₂. The addition of FPP into Mg(OH)₂/PP composites further enhanced the crystallization temperatures of PP. It is suggested that there is an activation of FPP to the heterogeneous nucleation effect on the Mg(OH)₂ surface. The addition of AA also increased the crystallization temperatures of PP in Mg(OH)₂/PP composites, although the crystallization temperature of PP was not influenced by the AA content, which is explained by the heterogeneous nucleation effect of the Mg(OH)₂ surface activated by FPP and AA. A synergistic effect on the crystallization of PP in Mg(OH)₂/PP composites further increased the crystallization temperatures of PP. However, The crystallization temperatures of Mg(OH)₂/PP composites modified by in situ FPP were lower than those of Mg(OH)₂/PP composites modified by addition of either FPP or AA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3610–3621, 2004     

Mechanical properties and fracture morphology of Al(OH)3/polypropylene composites modified by PP grafting with acrylic acid

Al(OH)₃/polypropylene (PP) composites modified by polypropylene grafted with acrylic acid (FPP) were prepared by melt extrusion. Effect of PP grafting with acrylic acid on mechanical properties and fracture morphology of Al(OH)₃/polypropylene composites were investigated. Although incorporation of Al(OH)₃ reduced the mechanical properties of PP, addition of FPP increased the mechanical properties of Al(OH)₃/PP composites. It is suggested that addition of FPP improve the dispersion of Al(OH)₃ and the interfacial interaction between filler and matrix. Mechanical properties of Al(OH)₃/FPP/PP composites depend on the grafting rate and the content of FPP. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2617–2623, 2001     

Mechanical properties of Mg(OH)2/polypropylene composites modified by functionalized polypropylene

Modified Mg(OH)₂/polypropylene (PP) composites were prepared by the addition of functionalized polypropylene (FPP); and acrylic acid (AA) and by the formation of in situ FPP. The effects of the addition of FPP and AA and the formation of in situ FPP on the mechanical properties of Mg(OH)₂/PP composites were investigated. Experimental results indicated that the addition of Mg(OH)₂ markedly reduced the mechanical properties of PP. The extent of reduction in notch impact strength of PP was higher than that in flexural strength and tensile strength. However, tensile modulus and flexural modulus increased with increased Mg(OH)₂ content. The addition of FPP facilitated the improvement in the flexural strength and tensile strength of Mg(OH)₂/PP composites. The higher the Mg(OH)₂ content was, the more significant the effect of FPP was. The incorporation of AA resulted in further increased mechanical properties, in particular the flexural strength, tensile strength, and notch impact strength of Mg(OH)₂/PP composites containing high levels of Mg(OH)₂. It not only improved mechanical properties but also increased the flame retardance of Mg(OH)₂/PP composites. Although the mechanical properties of composites modified by the formation of in situ FPP were lower than those of composites modified by only the addition of AA in the absence of diamylperoxide, the mechanical properties did not decline with increased Mg(OH)₂ content. Moreover, the mechanical properties increased with increasing AA content. The addition of an oxidation resistant did not influence the mechanical properties of the modified Mg(OH)₂/PP composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2139–2147, 2003     

原位形成FPP偶联Al(OH)3/PP中的界面相互作用研究

制备低含量Al(OH)3填充PP复合材料[Al(OH)3/PP]，研究原位形成的官能团化聚丙烯（FPP）在Al(OH)3/PP中的结晶、熔融行为，结晶形态，以及与各组分间的相互作用。研究认为，在复合材料中存在Al(OH)3与FPP间的化学作用，FPP与PP的相容与共结晶作用，Al(OH)3表面异相诱导成核作用，FPP对Al(OH)3表面异相诱导成核作用的活化作用等，从而改善了Al(OH)3/PP的物理与力学性能。     

Fracture morphology of Mg(OH)2/polypropylene composites modified by functionalized polypropylene

The morphologies of the fracture surface under impact and flexural testing of Mg(OH)₂/Polypropylene (PP) composites and their modified composites were investigated by scanning electron microscopy. Experimental results indicated that addition of functionalized polypropylene (FPP) and acrylic acid (AA) and the formation of in situ FPP changed the fracture morphologies of Mg(OH)₂/PP composites. We believe that addition of these modifiers improved the interfacial interaction and enhanced the interface adhesion between the particle and the matrix in Mg(OH)₂/PP composites. The degree of improvement was more significant in Mg(OH)₂/PP composites modified by the formation of in situ FPP. At low Mg(OH)₂ content, 2 phr AA exhibited a marked effect, but at high Mg(OH)₂ content, 4 phr AA afforded good effect. Due to the improved interface adhesion by interface interactions the fracture mechanism transformed from interface debonded fracture into a matrix fracture. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2148–2159, 2003     

Crystallization and melting behavior of nano‐CaCO3/polypropylene composites modified by acrylic acid

Nano‐CaCO₃/polypropylene (PP) composites modified with polypropylene grafted with acrylic acid (PP‐g‐AA) or acrylic acid with and without dicumyl peroxide (DCP) were prepared by a twin‐screw extruder. The crystallization and melting behavior of PP in the composites were investigated by DSC. The experimental results showed that the crystallization temperature of PP in the composites increased with increasing nano‐CaCO₃ content. Addition of PP‐g‐AA further increased the crystallization temperatures of PP in the composites. It is suggested that PP‐g‐AA could improve the nucleation effect of nano‐CaCO₃. However, the improvement in the nucleation effect of nano‐CaCO₃ would be saturated when the PP‐g‐AA content of 5 phf (parts per hundred based on weight of filler) was used. The increase in the crystallization temperature of PP was observed by adding AA into the composites and the crystallization temperature of the composites increased with increasing AA content. It is suggested that the AA reacted with nano‐CaCO₃ and the formation of Ca(AA)₂ promoted the nucleation of PP. In the presence of DCP, the increment of the AA content had no significant influence on the crystallization temperature of PP in the composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2443–2453, 2004     

Effect of silane‐grafted polypropylene on the mechanical properties and crystallization behavior of talc/polypropylene composites

Talc‐filled polypropylene (PP) composites coupled with silane‐grafted polypropylene (PP‐g‐Si) were prepared. Effect of PP‐g‐Si on the mechanical properties, crystallization, and melting behavior of PP composites was investigated. Compared with the uncoupled composites, the mechanical properties of Talc/PP composites coupled with a small amount of PP‐g‐Si were increased to some extent. Meanwhile, PP‐g‐Si can promote crystallization rate and increase crystallization temperature of PP in the composites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2974–2977, 2000     

Multiwalled carbon nanotubes‐based polypropylene composites: Influence of interfacial interaction on the crystallization behavior of polypropylene

Composites of polypropylene (PP) and multi‐walled carbon nanotubes (MWCNTs) were prepared via melt‐mixing utilizing Li‐salt of 6‐amino heaxanoic acid (Li‐AHA) modified MWCNTs in the presence of a compatibilizer (polypropylene‐g‐maleic anhydride; PP‐g‐MA). Improved interaction between the anhydride group of PP‐g‐MA and the amine functionality of Li‐AHA was confirmed via FTIR and Raman spectroscopic analysis. A higher glass transition temperature (T_g) of the PP phase has been observed in these composites as compared to pristine MWCNTs‐based composites. The crystallization temperature (T_c) of the PP phase was increased as a function of pristine MWCNTs concentration in PP/MWCNTs composites indicating hetero‐nucleating action of MWCNTs. However, T_c value was decreased in the presence of Li‐AHA modified MWCNTs indicating the adsorbed Li‐AHA on the MWCNTs surface. Moreover, T_c value was higher in the presence of Li‐AHA modified MWCNTs with PP‐g‐MA as compared to that of without PP‐g‐MA, suggesting the desorbed Li‐AHA from the MWCNTs surface due to melt‐interfacial reaction. Further, MWCNTs were extracted by hot vacuum filtration technique from PP/MWCNTs composites containing Li‐AHA and PP‐g‐MA. The isothermal crystallization kinetics showed a variation in crystallization behavior of the PP phase in the corresponding composites as compared to the “extracted MWCNTs.” POLYM. ENG. SCI., 57:183–196, 2017. © 2016 Society of Plastics Engineers     

Structural properties and mechanical behavior of injection molded composites of polypropylene and sisal fiber

Composites based on isotactic polypropylene (PP) and sisal fiber (SF) were prepared by melt mixing and injection molding. The melt mixing characteristics, thermal properties, morphology, crystalline structure, and mechanical behavior of the PP/SF composites were systematically investigated. The results show that the PP/SF composites can be melt mixed and injection molded under similar conditions as the PP homo‐polymer. For the composites with low sisal fiber content, the fibers act as sites for the nucleation of PP spherulites, and accelerate the crystallization rate and enhance the degree of crystallinity of PP. On the other hand, when the sisal fiber content is high, the fibers hinder the molecular chain motion of PP, and retard the crystallization. The inclusion of sisal fiber induces the formation of β‐form PP crystals in the PP/SF composites and produces little change in the inter‐planar spacing corresponding to the various diffraction peaks of PP. The apparent crystal size as indicated by the several diffraction peaks such as L_(110)α, L_(040)α, L_(130)α and L_(300)β of the α and β‐form crystals tend to increase in the PP/SF composites considerably. These results lead to the increase in the melting temperature of PP. Moreover, the stiffness of the PP/SF composites is improved by the addition of sisal fibers, but their tensile strength decreases because of the poor interfacial bonding. The PP/SF composites are toughened by the sisal fibers due to the formation of β‐form PP crystals and the pull‐out of sisal fibers from the PP matrix, both factors retard crack growth.     

Properties of microinjection‐molded polypropylene/graphite composites

In this study, polypropylene (PP) composites filled with two different types of graphite particles, that is, flake‐shaped synthetic graphite (SG) and low‐temperature expandable graphite (LTEG), were prepared by melt blending, followed by microinjection molding (μIM). The microparts had three consecutive zones with decreasing thickness along the flow direction (FD). Results showed that, in addition to the larger particle size, the in situ exfoliation of LTEG during melt processing is crucial to the overall enhancement of electrical conductivity when compared with their SG‐containing counterparts, as corroborated by morphology observations. Moreover, the preferential alignment of conductive particles favors the construction of conductive pathways along the FD. The melting and crystallization behavior for PP, PP/LTEG, and PP/SG materials, and samples from each section of the corresponding microparts were evaluated by differential scanning calorimetry. Results indicated that both the addition of graphite particles and the typical thermomechanical history of μIM (i.e., high shearing and cooling rates) experienced in different sections of the three‐step microparts influence the melting and crystallization behavior of the composites. POLYM. ENG. SCI., 59:1560–1569 2019. © 2019 Society of Plastics Engineers     

A study of the flame‐retardant properties of polypropylene/Al(OH)3/Mg(OH)2 composites

Polymeric materials are used extensively, but their applications are limited because many of them are flammable. Therefore ways to make them flame retardant have received much attention. In this work, polypropylene (PP) was used as the matrix resin, aluminium hydroxide (Al(OH)₃) and magnesium hydroxide (Mg(OH)₂) as flame‐retardant additives and zinc borate (ZB) as a flame‐retardant synergist. PP/Al(OH)₃/Mg(OH)₂ and PP/Al(OH)₃/Mg(OH)₂/ZB flame‐retardant composites were prepared with a twin‐screw extruder. The flame‐retardant properties, i.e. oxygen index (OI), burning velocity and smoke density, of the composites were measured. The results showed that OI increased with an increase of the filler content and decreased with an increase of the filler particle diameter. The burning velocity decreased with an increase of the filler content, while it first increased and then decreased with an increase of the filler particle diameter. The smoke density decreased with an increase of the filler content and increased with an increase of the filler particle diameter. There was a flame‐retardant synergy between Al(OH)₃/Mg(OH)₂ and ZB in the composites, and the smoke suppression effect was marked when ZB was added. Copyright © 2009 Society of Chemical Industry     

Isothermal crystallization kinetics of polypropylene in melt‐mixed composites of polypropylene and multi‐walled carbon nanotubes

The isothermal crystallization behaviour of the polypropylene (PP) phase in PP/multi‐walled carbon nanotubes (MWCNTs) composites has been investigated via differential scanning calorimetric analysis, which showed the influence of the varying dispersion level of MWCNTs in the respective PP matrix. PP/MWCNTs composites were prepared via melt‐blending technique, wherein two different grades of MWCNTs of varying average “agglomerate” size and varying entanglements (N‐MWCNTs and D‐MWCNTs) were utilized. Furthermore, the influence of melt‐viscosity of the PP phase was investigated on the crystallization kinetics of the PP/MWCNTs composites. Heterogeneous nucleation ability of MWCNTs has resulted in a decrease in half time of crystallization (t _1/2) from ～14 min for pure PP to ～6 min for PP/N‐MWCNTs and ～11 min for PP/D‐MWCNTs composites at 1 wt% of MWCNTs at 132 °C. Overall rate of crystallization (k) has significantly increased to 4.9 × 10^?2 min^?1 for PP/N‐MWCNTs composite as compared with 6.2 × 10^?3 min^?1 for PP/D‐MWCNTs composite at 0.5 wt% of MWCNTs at 132 °C. Moreover, the effect of a novel organic modifier, Li‐salt of 6‐amino hexanoic acid along with a compatibilizer (PP‐g‐MA) has also been investigated on the crystallization kinetics of the PP phase in PP/MWCNTs composites. POLYM. ENG. SCI., 57:1136–1146, 2017. © 2017 Society of Plastics Engineers     

Crystallization kinetics of polypropylene composites filled with nano calcium carbonate modified with maleic anhydride

The subject of this study was the crystallization behavior and thermal properties of polypropylene (PP)/maleic anhydride (MAH) modified nano calcium carbonate (nano‐CaCO₃) composites. In this study, 5 wt % nano‐CaCO₃ modified with different contents of MAH was filled into a PP matrix. X‐ray diffraction and differential scanning calorimetry were used to characterize the crystal morphology and crystallization kinetics of a series of composites. The results demonstrate that the nano‐CaCO₃ modified with MAH had an important effect on the thermal and morphological properties of the nanocomposites. The Avrami exponent of the pure PP was an integer, but those of the composites were not integers, but the crystallization rate constant decreased as the content of MAH in the nano‐CaCO₃ filler increased in isothermal crystallization. In nonisothermal crystallization, the kinetic parameter F(T) and the degree of crystallinity of pure PP were compared with those of the PP composites filled with nano‐CaCO₃. We suggest that heterogeneous nucleation existed in the PP composites and that the transformation and retention of the β‐form crystal into the α‐form crystal took place in the composite system and the β‐form crystal had a higher nucleation rate and growth process than the α‐form crystal in the PP composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Crystallization Behaviors of amino-terminated polyurethane (ATPU)-grafted polypropylene

Summary A melt-grafting approach was employed to prepare a novel functional polypropylene(FPP)—amino-terminated polyurethane grafted polypropylene (PP-g-ATPU). The crystallization behaviors of PP and PP/FPP blends were characterized using differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and polarized optical microscopy (POM). The effects of FPP composition on crystallization behavior, crystal transformation, and morphology of PP/FPP crystalline were investigated. The results showed that at a low dosage (<2.0 wt%) ATPU acted as a heterogeneous nucleation agent during the crystallization of PP/FPP blends. However, when the content of ATPU reached 2.0 wt% or higher, ATPU deteriorated the crystallization of PP or PP/FPP blends. The crystallite size decreased and the number of crystallites increased as the ATPU content increased. The Avrami analysis was adopted to describe the isothermal crystallization process. The difference in the exponent n between PP and PP/FPP suggested that the isothermal crystallization kinetics of PP/FPP blends followed a three-dimensional growth via heterogeneous nucleation. In terms of the half-time of the crystallization, t_1/2, the crystallization rate of functional PP blends was faster than that of PP homopolymer at a given crystallization temperature.     

Crystallization behaviors of polypropylene and functional polypropylene

The crystallization behaviors of polypropylene (PP) homopolymer and its blends with 0–15% functional polypropylene (FPP), the backbones of which were grafted with guanidine and diamide polymer chains, were investigated with differential scanning calorimetry and wide‐angle X‐ray scattering. The crystallization kinetics were studied with spectral depolarization. The results revealed that the presence of FPP reduced the crystallinity and crystallite size of PP. Meanwhile, FPP increased the crystallization rate. Compared with that of the PP homopolymer, the crystallization temperature of PP/FPP blends was increased by more than 10°C. During isothermal crystallization, the relative crystallinity, developed as a function of time, was described by the Avrami equation. The half‐time of crystallization for PP/FPP blends was much shorter than that for the PP homopolymer. The half‐time of crystallization of PP/FPP blends depended much less on the crystallization temperature than that of the PP homopolymer. Therefore, FPP accelerated the crystallization rate of PP in a manner similar to that of a nucleator. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 872–877, 2003     

Isotactic polypropylene metal oxide and silica nanocomposites by a two‐step process comprising in situ olefin polymerization and melt compounding

Nanocomposites of isotactic polypropylene (iPP) with 0.5 wt% filler of MgO@Mg(OH)₂ (35 nm) or silicon dioxide (20–60 nm) or barium titanate (50 nm) nanoparticles were obtained from melt compounding of filler masterbatches with commercial iPP. The masterbatches with 5 wt% nanofiller were prepared in an in situ polymerization procedure using a metallocene/methylaluminoxane (MAO) catalyst system that was supported on the respective oxides. The original agglomerates of the nanoparticles were broken up by treatment with dibutylmagnesium for MgO@Mg(OH)₂, and with ultrasound in the presence of MAO for SiO₂ and BaTiO₃. The tacticity (98% mmmm) of the in situ formed PP was not influenced by the presence of the nanofillers. Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy mapping show a fine dispersion of single particles and small clouds or clusters. The primary nanoparticles appear to be surrounded by polymer. The elongation at break was decreased to 50, 17 and 9% for MgO@Mg(OH)₂), SiO₂ and BaTiO₃, respectively. After melt compounding with iPP, a homogeneous single‐particle distribution of the oxidic nanoparticles was found in the resulting composites with 0.5 wt% filler content. © 2019 Society of Chemical Industry     

Effects of interfacial adhesion on properties of polypropylene/Wollastonite composites

Wollastonite reinforced polypropylene (PP/CaSiO₃) composites were prepared by melt extrusion. A silane coupling agent and a maleic anhydride grafted PP (PP‐g‐MA) were used to increase the interfacial adhesion between the filler and the matrix. The increased adhesion observed by scanning electron microscopy (SEM) resulted in improved mechanical properties. A model was applied to describe the relationship between the interfacial adhesion and tensile properties of PP/CaSiO₃ composites. There is stronger interfacial adhesion between silane‐treated CaSiO₃ and polymer matrix containing PP‐g‐MA as a modifier. Results of dynamic mechanical thermal analysis (DMTA) showed that stronger interfacial adhesion led to higher storage modulus. The influence of CaSiO₃ particles on the crystallization of PP was studied by using differential scanning calorimetry (DSC). The introduction of CaSiO₃ particles does not affect the crystallization temperature and crystallinity of PP matrix significantly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008