Kancheng Mai

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.

Effect of macromolecular coupling agent on the property of PP/GF composites

Silane-grafted polypropylene manufactured by a reactive grafting process was used as the coupling agent in polypropylene/glass-fiber composites to improve the interaction of the interfacial regions. Polypropylene reinforced with 30% by weight of short glass fibers was injection-molded and the mechanical behaviors were investigated. The results indicate that the mechanical properties (tensile strength, tensile modulus, flexural strength, flexural modulus, and Izod impact strength) of the composite increased remarkably as compared with the noncoupled glass fiber/polypropylene. SEM of the fracture surfaces of the coupled composites shows a good adhesion at the fiber/matrix interface: The fibers are coated with matrix polymer, and a matrix transition region exists near the fibers.

Isothermal crystallization behavior and melting characteristics of injection sample of nucleated polypropylene

The isothermal crystallization behavior and melting characteristics of pure polypropylene (PP) and PPs nucleated with a phosphate nucleating agent (A) and a sorbitol derivative (D) have been studied by differential scanning calorimetry (DSC). Compared with pure PP, nucleated PPs show a shorter half-times of crystallization. Dependence of crystallization rate of nucleated PP on the crystallization temperature is stronger than that of pure PP at the higher crystallization temperature, whereas the opposite results are obtained at the lower crystallization temperature. Addition of nucleating agent shifts the temperature at the deviation from the baseline of DSC melting curve, T, and the temperature at the completion of melting, T, to higher temperatures, indicating that nucleated PPs exhibit a higher perfection of PP crystals. A shoulder peak in the high temperature range of melting peak of nucleated PP and a wider low temperature region in the melting peak of pure PP are observed. Obviously, PP and nucleated PPs form different distribution of crystal perfection in the isothermal crystallization process. According to the half-time of crystallization, nucleating agent A is more effective than D.

Nonisothermal crystallization of poly(phenylene sulfide) in presence of molten state of crystalline polyamide 6

The nonisothermal crystallization and melting behavior of a poly(phenylene sulfide) (PPS) blend with polyamide 6 (PA6) were investigated by differential scanning calorimetry. The results indicate that the crystallization parameters for PPS become modified to a greater extent than those for PA6 in the blends. The PPS and PA6 crystallize at high temperature as a result of blending. The crystallization temperatures of PPS in its blends are always higher than that of pure PPS and are independent of the melting temperature and the residence time at that temperature. The PPS crystallization peak becomes narrower and the crystallization temperature shifts to a higher temperature, suggesting a faster rate of crystallization as a result of blending with PA6. This enhancement in the nucleation of PPS could be attributed to the possible presence of interfacial interactions between the component polymers to induce heterogeneous nucleation. On the other hand, the increase in the crystallization temperature of PA6 can be attributed to the heterogeneous nucleation provided by the already crystallized PPS. The heterogeneous nucleation induced by interfacial interactions depends on the temperature at which the polymers remain in the molten state and on the storage time at this temperature.

Effect of high-performance polymers on crystallization and multiple melting behavior of poly(phenylene sulfide)

The crystallization and multiple melting behavior of poly(phenylene sulfide) (PPS) and its blends with amorphous thermoplastic bisphenol A polysulfone (PSF) and phenolphthalein poly(ether ketone) (PEK-C), crystalline thermoplastic poly(ether ether ketone) (PEEK), and thermosetting bismaleimide (BMI) resin were investigated by a differential scanning calorimeter (DSC). The addition of PSF and PEK-C was found to have no influence on the crystallization temperature (Tc) and heat of crystallization (ΔHc) of PPS. A significant increase in the value of Tc and the intensity of the Tc peak of PPS was observed and the crystallization of PPS can be accelerated in the presence of the PEEK component. An increase in the Tc of PPS can also be accelerated in the BMI/PPS blend, but was no more significant than that in the PEEK/PPS blend. The Tc of PPS in the PEEK/PPS blends is dependent on the maximum temperature of the heating scans and can be divided into three temperature regions. The addition of a second component has no influence on the formation of a multiple melting peak. The double melting peaks can also be observed when PPS and its blends are crystallized dynamically from the molten state.

Effect of blending on the multiple melting behavior of polyphenylene sulfide

The effects of melting time (tmelt) and annealing time (ta) at a temperature closer to the melting point of polyphenylene sulfide (PPS) on the multiple melting behavior of neat PPS, and PPS component in their blends have been investigated by differential scanning calorimetry (DSC). It is found that double endotherm peak of PPS annealed at 275°C for less than three hours is different from that annealed for twelve hours. Double endotherm peak of PPS in PEEK/PPS blends shifts to lower temperature, and the intensity of the upper melting peak decreases significantly by addition of polyether ether ketone (PEEK). An additional third melting peak could be observed. The temperature of third melting peak is above 310°C and increases as the ta and PEEK content are increased. For PEK-C/PPS blends, the lower and upper melting temperatures of the PPS component are higher than that of neat PPS annealed at 275°C for twenty-three hours.

Preparation and characterization of polypropylene composites with nonmetallic materials recycled from printed circuit boards

After separation of metals from printed circuit boards (PCBs), they are sent to recycling process; however, significant amounts of useless nonmetallic particles are also included. Recycling useful materials from used PCBs is a major challenging problem that must be solved in China renewable resource industries through harmless and feasible processes. In this article, a novel β-polypropylene (PP)/nonmetals composite was prepared and evaluated. The nonmetallic particles were treated with calcium pimelate (PA, a β-nucleating agent for PP) and then compounded with PP through melt blending method. The results show that when cooling and crystallizing from the melt, β-PP are formed because of the surface effects of PA. This observation is assumed as the source of good rigidity and toughness of prepared PP composites. In the composite containing 10 wt % nonmetallic particles treated with 5 wt % PA, the content of β-PP was found to be larger than 90% and the impact strength and flexural modulus of PP composite increased by 205.3 and 61.8%, respectively, compared with those of neat PP. Although the addition of PA-modified nonmetals slightly increased the tensile strength of PP, considering all factors, the optimal mass ratio of PP/nonmetals/PA composites to reach optimum mechanical properties was observed as 100/10/0.5. Thus, the application of treated nonmetals to prepare nonmetals/β-PP composites provides a promising way to recycle PCBs waste and produce useful PP composites.

Non-isothermal crystallization kinetics and morphology of wollastonite-filled β-isotactic polypropylene composites

To obtain wollastonite-filled β-iPP composites, the wollastonite with β-nucleating surface (β-wollastonite) was prepared through chemical reaction between wollastonite with α-nucleating surface (α-wollastonite) and pimelic acid. The formation of calcium pimelate on the surface of wollastonite was proved using Fourier transform infrared spectrometry and scanning electron microscopy. The crystallization behavior, melting characteristics, non-isothermal crystallization kinetics, and crystalline morphologies of α- and β-wollastonite-filled iPP composites were studied by differential scanning calorimetry and polarizing optical microscopy. It is found that the crystallization peak temperatures of β-wollastonite-filled iPP composites were higher than that of α-wollastonite-filled iPP composites, which indicated that wollastonite with β-nucleating surface has stronger heterogeneous nucleation than that of wollastonite with α-nucleating surface. Although the crystallization temperatures of iPP and iPP composites decreased with increasing cooling rates, α-wollastonite-filled iPP composites mainly crystallized in α-spherulite and β-wollastonite-filled iPP composites formed β-spherulite. In addition, the spherulite size of β-wollastonite-filled iPP composites was smaller than that of α-wollastonite-filled iPP composites. Jeziorny and Mo methods were applicable to study the non-isothermal crystallization kinetics of wollastonite-filled iPP composites. The activation energy (∆E) and the nucleation efficiency (EN) of non-isothermal crystallization were calculated by Kissinger method and the equation proposed by Fillon, respectively. The β-wollastonite-filled iPP composites exhibited higher crystallization rate, activation energy, and EN than that of α-wollastonite-filled iPP composites.

Non-isothermal crystallization kinetics of montmorillonite filled β-isotactic polypropylene nanocomposites

Abstract Montmorillonite filled isotactic polypropylene nanocomposites (iPP/MMT) generally form α-modification due to the heterogeneous α-nucleation of MMT for iPP crystallization. To obtain MMT filled β-iPP nanocomposites, MMT with β-nucleating surface (β-MMT) was prepared by supporting calcium pimelate (CaPA) as β-nucleator on the surface of MMT particles. The crystallization behavior, melting characteristics, and non-isothermal crystallization kinetics and crystallization activation energies of MMT and β-MMT filled iPP nanocomposites were studied by differential scanning calorimetry. It is found that the crystallization peak temperatures of β-MMT filled iPP nanocomposites were higher than those of β-iPP and MMT filled iPP nanocomposites, which indicated that the heterogeneous nucleation of β-MMT is stronger than that of MMT. Jeziorny and Mo methods were applicable to study the non-isothermal crystallization kinetics of iPP and its nanocomposites. Addition of CaPA, MMT and β-MMT can increase the crystallization rate. The crystallization activation energies were calculated by Friedman methods, and nucleating activities were calculated by Dobreva methods. It is indicated that β-nucleation decreased the crystallization activation energy of iPP, and the nucleating activity of β-MMT is higher than that of CaPA and MMT.

Multiple melting behavior of polyphenylene sulfide blends with polyamide 6

Although there are many studies on the multiple melting behavior of polyphenylene sulfide (PPS) homopolymer, similar investigations on PPS component in PPS blends with thermoplastics are relatively rare. In the present paper, the multiple melting behavior of PPS blends with polyamide 6 (PA6) have been investigated by differential scanning calorimetry (DSC). The double melting peaks are also observed for PPS in the blends. Although the annealing temperature and time as well as the heating rate of DSC scanning are different, the lower melting peak temperature of PPS in the blend is higher than that of pure PPS and the higher melting peak temperature is lower than that of pure PPS. It is suggested that PA6 can accelerate the cold-crystallization of amorphous PPS due to the possible presence of interfacial interaction between the component polymers to induce the heterogeneous nucleation, and increase the perfection of PPS crystals. The multiple melting behavior of PPS in the blends are explained by recrystallization.