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The crystalline behaviors and micromorphology of polymers have a large impact on the physical and mechanical properties, especially for polypropylene (PP) composites with toughening effect. In this work, the changes of the content ratio for layered double hydroxide (LDH) and [beta]-nucleating agent (CaHA), mechanical properties, and crystallization behaviors of PP/ethylene vinyl acetate copolymer (EVA)/LDH ternary composites are investigated by differential scanning calorimeter (DSC), polarizing optical microscopy (POM), scanning electron microscopy (SEM), and notched impact strength testing. The CaHA is used for synergistic toughening with LDH, and the highest notched impact strength is achieved in the 6PEL2 sample with CaHA of 0.03 phr and LDH of 5.70 phr, which is about 100% higher than that of pure PP. It is found from the crystallization behaviors and SEM images of the composites that 6PEL2 has the highest relative content of [beta]-crystals and the appearance of rougher interface and deformation pullout of the EVA phase in 6PEL2 because of dislocations in the [beta]-crystals and the formation of a large number of cavities absorbing the impact energy. KEYWORDS composites, crystallization, polypropylene, toughness, 1 | INTRODUCTION Polypropylene (PP), one of the general-purpose plastics, is used in large quantities due to its excellent corrosion resistance, processability, and low price. [1] Due to the poor [...]

In this work, the effect of calcium sulfate whisker (CSW) and ultrasonically-modified CSW (UCSW) on the crystal structure and isothermal crystallization of isotactic polypropylene (iPP) is studied by using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarized optical microscopy (POM). UCSW obviously increases heterogeneous nucleation. The isothermal crystallization kinetics of pure iPP, iPP/CSW, and iPP/UCSW composites are analyzed by the Avrami method. Although the Avrami exponent (n) of these samples only changed slightly, the half crystallization time ([t.sub.1/2]) indicates that CSW and UCSW decrease the overall crystallization time and increase the crystallization rate ([R.sub.c]). POM results show that most crystals are [beta]-iPP shaped and the spherulite size decreases significantly with the addition of UCSW. The apparent equilibrium temperature of iPP/UCSW composites is lower than that of pure iPP and iPP/CSW composites. The values of [beta]-iPP fold surface free energy ([[sigma].sub.e]) and the nucleation parameter ([K.sub.g]) are much lower than that of [alpha]-iPP for these iPP composites. The content of [beta]-crystal in iPP composites increases due to the addition of UCSW. KEYWORDS composites, crystallization, kinetics, ultrasonic, 1 | INTRODUCTION As well known, isotactic polypropylene (iPP) has been widely used thermoplastic because of its comprehensive properties, such as easy of processing, low density, high heat resistance, recycle [...]

A phenethyl-bridged DOPO derivative (DiDOPO) is combined with polytetrafluoroethylene (PTFE) in thermoplastic Polyurethane (TPU). The flame retardancy and thermal stability of TPU/PTFE/DiDOPO composites with different weight percentages of DiDOPO are investigated by using limiting oxygen index (LOI), UL-94 test, cone calorimetry test (OCT), scanning electronic microscopy (SEM), energy-dispersive spectrometry, and thermogravimetric analysis (TGA). With the incorporation of 8 wt% DiDOPO, the LOI value of TPU/PTFE/DiDOPO composites increases to 34.0% from 25.4% of TPU, and the V-0 rating level is achieved. The CCT results indicate that the peak heat release rate and total heat release of TPU/PTFE/ DiDOPO composites decrease due to the addition of DiDOPO and PTFE. The thermal decomposition process of TPU is changed due to the present of DiDOPO and PTFE. Based on this, the Flynn-Wall-Ozawa method for the determination of characteristic degradation kinetics parameters is evaluated. SEM results and residues from TGA curves show that the addition of DiDOPO promotes the increase In the char layer and a crosslinked char coating exists after burning. The flame-retardant mechanism is flame inhibition. Overall, these findings indicate that the combination of DiDOPO with PTFE in TPU is an effective way in developing high-performance resins with attractive flame retardancy., INTRODUCTION Thermoplastic polyurethane (TPU) is a block copolymer that has been widely used in many fields such as automobiles, tubes, belts, and cables, because of its excellent properties of abrasion [...]

In this work, the long glass fiber reinforced poly(decamethylene terephthalanide) (PA10T/LGF) composites and short glass fiber reinforced PA10T (PA10T/SGF) composites were prepared by two different extrusion processing methods, respectively. The results of mechanical properties reveal the introduction of glass fiber can improve the performance of the material, and the LGF reinforced PA10T composites can achieve much higher performance than the SGF reinforced ones at the same level of fiber contents. The thermal stabilities of neat PA10T, PA10T/ SGF, and PA10T/LGF are investigated by nonisothermal TG analysis. The thermal degradation kinetics is introduced by using Kissinger and Flynn-Wall-Ozawa methods and the thermal degradation mechanism functions of the samples are calculated by the Coats-Redfem model. The results show that the thermal stabilities of PA10T/SGF and neat PA10T are better than that of PA10T/LGF. In addition, the incorporation of glass fiber into PA10T do not have much effect on the reaction mechanism type of thermal degradation compared with that neat PA10T. Furthermore, the thermal stability analysis of the composites is verified by the computed results of Gibbs free energy ([DELTA]G#)., INTRODUCTION With the miniaturization of electronic equipment, especially the emergence and development of surface mount technology, there are higher requirements on the heat resistance and dimensional stability of materials, such [...]

In this work, the composites based on long glass fiber reinforced polypropylene/intumescent flame retardant (LGFPP/ IFR) were prepared by melt blending. This article presented an experimental research on the influence of combined environment elements in natural condition on the properties of LGFPP/IFR composites with 0-12 months ageing. The flammability and thermal properties of the composites were investigated by limiting oxygen index (LOI), UL-94 test, cone calorimeter test (OCT), thermal gravimetric analysis (TGA), mechanical properties test and energy dispersive X-ray analysis (EDAX). The LOI values increased from 27.5 to 28.3 in 0-6 months ageing, and then decreased back, however, the TGA curves shift to the lower temperature. The thermal degradation kinetics were analyzed and the apparent active energy (E) of aged and unaged samples were calculated by Flynn-Wall-Ozawa method. The results indicated that much lower E values were obtained after 3-12 months ageing. EDAX data proved that the IFR particles gathered on the surface of samples in natural exposing, by which had some effect on the thermal stability and flame retardancy of the composites. The mechanical properties showed a global decrease in the whole ageing period by matrix degradation and interface debonding under the influence of combined environment elements. POLYM. ENG. SCI., 58:2098-2105, 2018., INTRODUCTIONPolypropylene (PP) is an important kind of general-purpose plastics, which has been widely used for decades due to its excellent comprehensive performances and low price. But as a structure material, [...]

Nanocomposites of organic nano-montmorillonite (nano-OMMT)-filled immiscible polyamide 6 (PA6)/polystyrene (PS) blends were prepared by three different processing methods. Masterbatch M1 of OMMT/PA6 and masterbatch M2 of OMMT/PS were prepared as [...]

In this work, the flammability behaviors and synergistic effects of red phosphorus masterbatch (RPM) with expandable graphite (EG) in flame-retardant high-density polyethylene/ethylene vinyl-acetate copolymer (HDPE/ EVA) composites have been investigated by limiting oxygen index (LOI), UL-94 test, cone calorimeter test (CCT), thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) and scanning electron microscopy (SEM). The data obtained from LOI, UL-94 test and CCT showed that suitable amount of RPM had synergistic effects with EG in the HDPE/EVA/EG/RPM composites. The addition of RPM greatly increased the LOI values by 3.4%, obtained UL-94 V-0 rating, decreased the heat release rates and total heat release, and prolongated the ignition time when 6.7 phr RPM substituted for EG in the HDPE/EVA/EG/RPM composites. The data from TGA and FTIR spectra also indicated the synergistic effects of RPM with EG considerably enhanced the thermal degradation temperatures. The morphological observations after UL-94, CCT, and SEM images presented positive evidences that the synergistic effects took place for RPM with EG, and the flame-retardant mechanism has been changed in flame-retardant HDPE/EVA/EG/RPM composites. The formation of stable and compact charred residues promoted by RPM acted as effective heat barriers and thermal insulations, which improved the flame-retardant performances and prevented the underlying polymer materials from burning., INTRODUCTION High-density polyethylene (HDPE) is one of the most widely used polyolefins due to its balanced mechanical properties, chemical resistance, and ease processing advantages [1-4]. To improve its flexibility, toughness, [...]

In this work, polyamide 6 (PA6) as a charring agent has been used in combination with thermoplastic polyurethane (TPU)-microencapsulated ammonium polyphosphate (MTAPP) forming intumescent flame retardants (IFRs) which applies in polypropylene (PP). The effects of the IFRs on the flame retardancy, morphology of char layers, water resistance, thermal properties and mechanical properties of flame-retardant PP composites are investigated by limiting oxygen index (LOI), UL-94 test, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and mechanical properties test. The results show that the PP/MTAPP/PA6 composites exhibit much better flame-retardant performances than the PP/MTAPP composites. The higher LOI values and UL-94 V-2 of the PP/MTAPP composites with suitable amount of PA6 are obtained, which is attributed to the thick and compact char layer structure evidenced by SEM. The results from TGA and DSC demonstrate that the introduction of PA6 into PP/ MTAPP composites has a great effect on the thermal stability and crystallization behaviors of the composites. Furthermore, the mechanical properties of PP/MTAPP/PA6 composites are also improved greatly due to the presence of PA6 as a charring agent., INTRODUCTION Polypropylene (PP), as an important commodity plastic, has been widely applied in many fields, such as cars, electronic shells, architectural materials, furniture, interior decorations, etc. [1-3] However, PP is [...]

In this article, high-density polyethylene/ethylene vinyl-acetate copolymer (HDPE/EVA) composites filled with two different particle sizes (45 and 150 µm) of expandable graphite (EG) were prepared by using a twin-screw extruder. The thermal stability, flammability, and mechanical properties of HDPE/EVA/EG composites were investigated by thermogravimetric analysis (TGA), cone calorimeter test (CCT), tensile test, and scanning electron microscopy (SEM). The results from TGA and CCT indicated that EG significantly enhanced the thermal stability and fire resistance of HDPE/EVA blend. The thermal stability and flame retardancy of HDPE/ EVA/EG composites were improved with decreasing particle size of EG. Although the onset of weight loss of the flame-retardant composites occurred at a lower temperature than that of HDPE/EVA blend, the flame-retardant composites produced a large amount of char residue at a high temperature. The consolidated char layer formed a barrier, which could reduce heat, low-molecular transfer, and air incursion, and thus enhanced the flame retardancy. The data from the tensile test showed that the addition of EG deteriorated the mechanical properties; however, the tensile stress and strain of HDPE/EVA/EG composites increased with decreasing the particle size of EG owing to the strong interface adhesion between polymer matrix and inorganic particles. POLYM. ENG. SCI., 54:1162-1169, 2014. © 2013 Society of Plastics Engineers, INTRODUCTION Polyethylene (PE) is one of the most widely used polymeric materials owing to its low cost, balanced mechanical properties, good processability, and so on [1-3]. However, there are some [...]

Polypyrrole (PPY) was prepared by the method of chemical oxidation polymerization in ice bath, and a series of products with different morphology or particle size were obtained through changing volume ratio of acetonitrile to water (VRAW) in the mixed reaction solvents. The structures, morphologies, yield, and conductivities of the as-prepared PPY were characterized by FTIR, SEM, electronic balance, and Four-probe conductivity meter. Furthermore, the effect of VRAW on the morphology of the obtained PPY was investigated in detail. As shown from the corresponding results, PPY's average diameter decreased with the increase of VRAW in the range of 1:9 to 4:6, with particle morphology; the film-shaped PPY was obtained when VRAW was in the scope of 5:5 to 7:3. According to the analysis on the polymerization mechanism of pyrrole in the reaction mixture, the change of PPY's morphology was attributed to the structure change of acetonitrile micelle from spherical structure to double layered structure. As the further study shown, the PPY synthesized at a VRAW of 1:9 shows higher yield and conductivity than which prepared in pure water without acetonitrile; however, the further increase of VRAW results in the decrease of the yield and conductivity. POLYM. ENG. SCI., 52:1600-1605, 2012.[C] 2012 Society of Plastics Engineers, INTRODUCTION Because of the good properties of easy preparation, high electronic conductivity, and excellent stability (1-6). the conducting polymer polypyrrole (PPY) has attracted more and more attentions since its first [...]

Melt grafting of the multimonomer system of maleic anhydride (MAH)/styrene (St) onto ethylene-octene copolymer (POE) was performed by a twin-screw extruder. The effects of St and initiator contents as well as MAH/St on the properties of the grafted POE were characterized by the Fourier transform infrared spectroscopy, melt flow index, dynamic rheological behaviors, and thermogravimetric analysis. It is shown that the addition of St can significantly enhance MAH grafting degree onto POE. MFI values of grafted POE are affected not only by MAH/St copolymer concentration, but also by initiator concentration. These data indicate that the interaction and reaction between MAH and St monomers plays an important role in the grafting reaction. St improves the grafting reactivity of MAH and reacts with MAH before the two monomers graft onto POE. And high grafting degree can be obtained while the gel connect is still low. Compared with neat POE, grafted POE shows different dynamic rheological behaviors and high thermal stability. POLYM. ENG. SCI., 48:2289-2296, 2008. © 2008 society of Plastics Engineers, INTRODUCTION Polyolefin elastomer (POE) is ethylene-octene copolymer developed using a metallocene catalyst by Dow Chemical. POE is characterized by narrow molecular weight distribution and homogeneous comonomer distribution. It has fast [...]

In this study, the flammability characterization and synergistic effects of different particle size of expandable graphite (EG) with modified magnesium hydroxide (MH) in flame-retardant polypropylene (PP) composites were studied by limiting oxygen index (LOI), UL-94 test, ther-mogravimetric analysis (TGA), and fourier transform infrared (FTIR) spectroscopy. The results showed that the particle size of EG had a great effect on the flammability of the PP/MH/EG composites. The EG2 with smaller particle size could apparently increase the LOI value and improved the UL-94 flammability properties rating of the PP composites. The data obtained from the TGA and FTIR curves indicated that the thermo-oxidative stability of PP/MH/EG composites increased with decreasing particle size of EG. And the smaller the particle size of EG, the higher the residues of the composite. POLYM. ENG. SCI., 47:1756-1760, 2007. © 2007 Society of Plastics Engineers, INTRODUCTION Traditionally, halogen containing compounds, alone or in conjunction with antimony trioxide, are the main flame retardants (FR) of polyolefins (PO). There is an increasingly restriction about the use of [...]