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Polypropylene materials have attracted much attention due to their wide using temperature zones and are nonpoisonous. However, the poor electrical and thermal properties limit their application. In this work, the Cu nanowires with the single phase structure and uniform microstructure were successfully synthesized by tuning the reaction time. Then, the Cu nanowires were in the polypropylene matrix to optimize the electrical transport properties and thermal transport properties. The results show that the resistance of Cu nanowire-composited samples decreases by orders of magnitude, the resistance for the PP+0.5wt% Cu nanowires sample is $2.5\times 10^{10}\mathrm{\Omega }$, which is two orders of magnitude lower than that of the pristine sample due to the addition carrier transport path. Besides, the thermal diffusion coefficient of the Cu nanowire-composited sample increases to 0.194mm²s${}^{-1}$, which is 12.7% higher than that of the pristine sample. The improvement in electrical transport properties and thermal transport properties for polypropylene materials can be applied in the field of package materials, which can reduce energy consumption and the occurrence of safety accidents in the production process.

The examination of serration behavior has been made after the tensile deformation of the AA/PP/AA sandwich sheets as well as that of the 5182 aluminum skins. All sandwich sheets and the 5182 aluminum skin showed serration behavior on their flow curves. However, the magnitude of serration was significantly diminished in the sandwich sheet with high volume fraction of the polypropylene core. According to the results of the analysis of the surface roughness following the tensile test, Lüders band depth of the sandwich sheet evidently showed lower than that of the 5182 aluminum skin. The strain rate sensitivity, m-value, of the 5182 aluminum skin was -0.006. By attaching these skins to the polypropylene core, which has relatively large positive value of 0.050, m-value of the sandwich sheets changed to a positive value. The serration reduction of the sandwich sheets was quantitatively investigated with respect to the effect on polypropylene thickness variation, that on the strain rate sensitivity and that on the localized stress state. It was found that the serration reduction degree from the experimental results of the sandwich sheet was higher than from the calculated values by the rule of mixture based on the volume fraction of the skins and the core.

This paper deals with an investigation on the photoluminescence (PL) properties of PP+PbS/CdS nanocomposites at different temperatures ($100^{\circ }\mathrm{\text{C}}$, $120^{\circ }\mathrm{\text{C}}$ and $140^{\circ }\mathrm{\text{C}}$) under vacuum. The optical bandgap was calculated on the basis of the spectra of UV absorption and it was shown that after thermal treatment the nanocomposites optical bandgap changed. The change has been attributed to the modification of the upper molecular structure of the polymer matrix due to the thermal process. The luminescence spectra of nanocomposites before and after thermal treatment at different temperatures ($100^{\circ }\mathrm{\text{C}}$, $120^{\circ }\mathrm{\text{C}}$ and $140^{\circ }\mathrm{\text{C}}$) under vacuum were also measured and discussed. A very high luminescence intensity was observed after thermal treatment at $100^{\circ }\mathrm{\text{C}}$ temperature. This was attributed to the luminescent centers’ increase and the optimal structure formation.

At present, research is actively being conducted into composite materials using natural fibers and thermoplastic resins that can serve as eco-friendly materials. However, the weak interfacial bonding shape between natural fibers and thermoplastic resins leads to low mechanical properties in the natural fiber-reinforced polymer composite. This study examined the usage of basalt fibers (BFs) and polypropylene (PP) to address this issue. Plasma surface modification (PSM) was performed on the surface of the BF to improve the interfacial bonding force between the fiber and the thermoplastic resin. Studies on monomer selection (HMDSO), plasma generation conditions (3 kV), and surface modification time (20–150 s) were conducted to determine the optimal conditions for PSM. FT-IR analysis was performed to confirm the surface modification and the fracture surface was observed after the mechanical properties were measured. The experimental results confirmed the effect of PSM on the BF resulting in about 10% improvement on the related mechanical properties.

Membrane wetting by liquid absorbents limits the performance of membrane contactor, which shows the necessity of using superhydrophobic membranes in these systems. In recent years, the use of plasma irradiation to modify polymer membranes has received much attention from researchers. In this experimental research, the polypropylene membrane surface was irradiated with CF₄ plasma at different times to reduce the membrane wetting and create a superhydrophobic surface. The modified membranes were evaluated in terms of measurements of roughness and morphology, chemical properties, and hydrophilicity. In the results of the AFM^* and SEM^† tests, the structural difference caused by the surface modification and the resulting roughness can be well observed. The FTIR^‡ results showed the creation of new functional groups due to the surface modification process. The physicochemical changes of the modified surface led to an increase in the CA^§ to 166^∘. Finally, the performance of modified membranes was evaluated for protein adsorption, and the results indicated a significant decrease in adsorption for modified superhydrophobic membranes compared to the control membrane. Achieving superhydrophobic PP membranes by plasma treatment without damaging the physical structure of these membranes is a significant result that is simply not achieved by other methods because it causes the membrane tissue to disintegrate. It has also been shown that the conditions of plasma application play a decisive role in the hydrophobicity of modified surfaces.

The objective of our study was to (1) evaluate mesh strength and collagen incorporation after 4 and 12 weeks of implantation in a rat abdominal wall model and (2) determine the relationship between collagen deposition and mechanical strength of a chitosan-coated polypropylene mesh. We implanted 0.5% chitosan-coated polypropylene mesh (PPM), collagen-coated PPM (PelvitexTM; C.R. Bard), and PPM (Avaulta Solo${}^{\mathrm{\text{®}}}$; C.R. Bard) using a rat abdominal defect model. Mechanical properties were determined from uniaxial tensile testing and collagen deposition of each mesh was evaluated 4 and 12 weeks post-implantation. We found that after implantation, the neo tissue of Ch-PPM is stiffer than the commercially available meshes. We also observed no significant difference in the ratio of collagen types I/III between mesh samples at 4 weeks or 12 weeks. We found no relationship between the ratio of collagen types I/III and the mechanical strength of mesh samples after implantation. The increased stiffness with chitosan coating could be due to increased muscle tissue ingrowth.

Nanosize barium sulfate (BaSO₄) particles prepared with dodecyl benzene sulfonic acid (DBSA) in ethanol–water reaction system are used to prepare BaSO₄/polypropylene (PP) nanocomposites by melt mixing method. It is then made into hybrid fibers by melt spinning and subsequent drawing with different ratios. The hybrid fibers are characterized by rheology, morphology, thermal stability and mechanical properties, respectively. The results indicate that the DBSA-modified BaSO₄ can improve the spinnability of BaSO₄/PP hybrid multifilament even at high BaSO₄ nanoparticles concentration. DBSA can be used as compatibilizer to enhance the interface interaction of BaSO₄/PP nanocomposites, because DBSA contains both hydrophobicity long alkyl chain and hydrophilic sulfonic group. Therefore, it can improve the performances of BaSO₄/PP hybrid multifilament.

Selective laser sintering (SLS) is an additive manufacturing technology whereby parts are built through selective consolidation of a powder by a laser beam. Recently, Polypropylene (PP) has been used in the SLS because of its appropriate mechanical performance as well as low cost and density. In the SLS, laser parameters are very effective on the mechanical properties of the sintered parts. In this study, the effects of the laser parameters including power, the laser scanning speed, and the laser scanning pattern on the tensile strength of the sintered samples were experimentally investigated. The PP and PP/CNT (carbon nanotube) composites were used as raw materials and the results were compared. Taguchi method was employed as the experimental design, and optimal levels of parameters were extracted using signal-to-noise analysis. The main effects of factors and interactions were considered in this paper. The results show that the laser scanning pattern and the laser power have the most effects on the tensile strength of the produced samples. In addition, the comparison between the results of the experiments demonstrates an increase in the tensile strength, which is 15% in maximum value, by adding CNT to PP.

The isothermal crystallizations of three kinds of commercial isotactic polypropylene have been studied by DSC and rheometric experiments, in a range of temperatures where the rate of crystallization is moderate. As the crystallization proceeds, volume contraction induces tensile force upon the parallel plates. The tensile force relaxed quickly in liquid states, but after a critical amount of the relative crystallinity, it starts to accumulate in the static test, that is, with the motionless parallel plates. A new method to determine the liquid-solid transition by the static tensile force is proposed and compared with two dynamic methods of detecting liquid-solid transition, that is, the power-law modulus theory and the yield modulus model. The tensile force method predicted considerably earlier transition than the dynamic methods, and the corresponding DSC data indicate relative crystallinity of larger than 0.2 at the transition times. The limitation of dynamic methods and other possible errors have been analyzed. While the dynamic methods are suitable for slow crystallization, the tensile force method is more appropriate for the crystallization of moderate rates. Moreover, it has the advantage of almost not disturbing the crystallizing materials before the transition.

The effect of N,N,N′,N′-tetraalkyl terephthalamide (TATA) on the non-isothermal crystallization and melting characteristics of polypropylene (PP) was studied. The addition of TATA can lead to the formation of β-crystal PP. With the increase in TATA concentration the degree of crystallinity for β-crystal PP increased significantly, and that for α-crystal PP decreased, which indicated that TATA effectively induced the formation of β-crystal PP. WAXD also revealed the existence of β-crystal PP after the introduction of TATA into PP. PP containing TATA crystallized at a temperature range of 5–10°C higher than that of pure PP, and the half-crystallization time (t_1/2) and Avrami exponent (n) of PP at the same cooling rate were decreased by the addition of TATA, indicating that TATA influenced the crystallization rate and crystallization growth mode of PP. The rate constant of crystallization of PP containing TATA (Z_c) was larger than that of pure PP, which further indicated that the crystallization of PP was accelerated by the addition of TATA.

The hierarchical structure and interfacial morphology of injection-molded bars of polypropylene (PP) based blends and composites have been investigated in detail from the skin to the core. For preparation of injection-molded bars with high-level orientation and good interfacial adhesion a dynamic packing injection molding technology was applied to exert oscillatory shear on the melts during solidification stage. Depending on incorporated component, interfacial adhesion and processing conditions, various oriented structure and morphology could be obtained. First, we will elucidate the epitaxial behavior between PP and high-density polyethylene occurring in practical molded processing. Then, the shear-induced transcrystalline structure will be the main focus for PP/fiber composites. At last, various oriented clay structures have been ascertained unambiguously in PP/organoclay nanocomposites along the thickness of molded bars.

Oleic acid (OA)-modified SiO₂(OA-m-SiO₂) nanoparticles were prepared using surface modification method. Infrared spectroscopy (IR) was used to investigate the structure of the OA-m-SiO₂ nanoparticles, and the result showed that OA attached onto the surface of SiO₂ nanoparticles through esterification. Effect of OA concentration on the dispersion stability of OA-m-SiO₂ in heptane was also studied, and the result indicated that OA-m-SiO₂ nanoparticles were dispersed in heptane more stably than the unmodified ones. OA-m-SiO₂ nanoparticles can also be dispersed in polypropylene (PP) matrix in nano-scale. The effect of OA-m-SiO₂ on crystallization of PP was studied by means of DSC. It was found that the introduction of OA-m-SiO₂ resulted in significant increase in the crystallization temperature, crystallization degree and crystallization rate of PP, and OA-m-SiO₂ could effectively induce the formation of β-crystal PP. Effect of OA-m-SiO₂ content on mechanical properties of PP/OA-m-SiO₂ nanocomposites was also studied. The results show that OA-m-SiO₂ can significantly improve the mechanical properties of PP.

A novel charring agent, bis(1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane) phenylphosphine sulfide (BCPPS), has been synthesized, and it is combined with ammonium polyphosphate (APP) and melamine phosphate (MP) to impart flame retardance and dripping resistance for polypropylene (PP). The fire performance of the treated PP is investigated by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter, and the thermal stability and thermal oxidative stability of the composites are studied using thermogravimetric analysis (TG). It has been found that the treated PP with the optimal flame retardant formulation of APP:MP:BCPPS = 12:6:12 (weight ratio, formulation 10) gives an LOI of 31.3 and UL-94 V-0 rating. The results from cone calorimeter indicate that both the heat release rate (HRR) and the total heat evolved (THE) of IFR-PP (formulation 10) decrease significantly compared with those of neat PP. The TG result shows that the IFR-PP (formulation 10) has a high yield of residual char at high temperature. FTIR is used to investigate the residue of the treated PP that degrades at 400°C for different time. The compact outer surface and the shaggy inner surface can be observed from the SEM graph of the residual chars after LOI test, which form a much better barrier for the transfer of heat and fuel during combustion and show good flame retardancy. Moreover, the treated PP and its residue are investigated by XPS analysis.

A series of polydimethylsiloxane (PDMS) with varied molecular weights (M_w = 3 × 10⁶, 1 × 10⁶ and 0.5 × 10⁶) were melt blended with PP to investigate the effect of PDMS molecular weight (MW) on the morphology and mechanical properties of PP/PDMS blends. Scanning electron microscopic (SEM) examination showed that the size of PDMS domains was dependent on the MW of PDMS. It was found that the lower the value of PDMS MW, the better dispersion of the PDMS domains in the PP matrix. Tensile and Izod impact tests revealed that the addition of PDMS with lower MW would lead to a more significant increase in impact strength of the blends compared with the blends with higher MW ones, while the influence of the molecular weight on tensile strengths of the blends was relatively small in the MW range studied. Differential scanning calorimetry (DSC) results also showed that the crystallization temperature of PP was increased with decreasing PDMS MW, indicating a better nucleation capability of lower MW of PDMS. Melting flow rate (MFR) measurements indicated that the processibility of PP could be enhanced by adding PDMS, and again the lower MW PDMS resulted in better data. Our work demonstrates that not only the processibility but also the mechanical properties of PP could be enhanced to a more significant degree by using low MW PDMS than the higher ones.

A novel intumnescent flame melamine salt of dipentaerythriol phosphate (MDP), was prepared from dipentaerythritol (DPE) polyphosphoric acid, and melamine. The flammability, combustion behavior, and thermal degradation and stability of PP-MDP were characterized. When MDP loading was 20 wt%, LOI values of the composites reached up to 27%, and UL94 rating, V-2. PP-MDP containing 1 wt%; Cu-ZSM-5 presented the highest LOI value of 30.5%; and UL94 rating, V-0, and released lest heat during cone test. TG data showed that the thermal degradation of PP was improved by the addition of MDP. While the loading of ZSM-5 was 1 wt%; or higher, the main weight loss delayed with 50°C, and 80°C, compared with PP and PP-MDP respectively. The appropriate loading Cu-ZSM-5 made PP-MDP possess higher thermal oxidative stability. By SEM, the formation of a dense and thick char layer was observed on the char layer of PP-MDP-containing Cu-ZSM-5, responsible for high flame retardancy. So, the synergistic flame retardancy effects of MDP and Cu-ZSM-5 on PP existed. The mechanism of synergistic effect of Cu-ZSM-5 zeolite on flame retarded PP by MDP was discussed.

Polypropylene (PP)/multi-walled carbon nanotube (MWCNT)/calcium carbonate (CaCO₃) composites are prepared by melt mixing using two types of CaCO₃ of different sizes. The electrical resistivities of the composites with the two types of CaCO₃ are all lower than those of the corresponding PP/MWCNT composites at various MWCNT loadings (1 wt%–5 wt%). The morphology of the composites is investigated by field emission scanning electron microscopy (FESEM). The crystallization behavior of PP in the composites is characterized by differential scanning calorimetry (DSC). The storage modulus, as measured by dynamic mechanical analysis (DMA), increases significantly by the presence of CaCO₃.

The service life of a polyolefin product depends to large extent on the type and amount of the antioxidants added. During the manufacturing, storage and use of the product the antioxidants are depleted by physical processes and chemical degradation, and this impairs its long-term performance. The initial and in-use oxidation stability is often characterized and monitored by the measurement of the oxidative induction time (OIT), and service life predictions are based on the rate of decrease of the OIT value. To study the correlation between the OIT value and the actual antioxidant concentration, eight random arrays of high-impact polypropylene (PP) strands stabilized using six different antioxidant packages (composed of Irgafos 168, Irganox 1010 and 1330, Chimassorb 944) were immersed in hot water (80°C and 90°C) and oven aged in air (80°C) for more than two years, and the change of OIT values and antioxidant concentrations was measured. For phosphitic and phenolic stabilizers water immersion is generally a more critical aging condition than oven aging in air, while for the hindered amine stabilizers (HAS) the opposite was observed. As expected, a linear correlation between OIT values and concentrations was found for the "classical" package of phosphitic and phenolic stabilizers. In the case of Irganox 1330, the change of the OIT values during aging was considerably slower than the change of concentration. Even when zero concentration was reached according to the vanishing peak height in the chromatogram, a considerable OIT value was still measurable. This may be due to unidentified degradation products of Irganox 1330 which still act as antioxidants in the long run. Addition of HAS (Chimassorb 944) seems to enhance the initial OIT of stabilized phenolic samples and the long-term effectiveness of the phenolic stabilization under air oven aging conditions. However, the marked long-term effectiveness of the HAS itself and the slow change with time of the concentration were not detectable by OIT measurements above the PP melting point of about 170°C.

A model experiment was done to clear the formation mechanism of protective layers during combustion of polypropylene (PP)/organically modified montmorillonite (OMMT) nanocomposites. The investigation was focused on the effects of annealing temperature on the structural changes and protective layer formation. The decomposition of OMMT and degradation of PP/OMMT nanocomposites were characterized by means of thermogravimetric analysis (TGA). The structural evolution and composition change in the surface region of PP/OMMT nanocomposites during heating were monitored by means of X-ray photoelectron spectroscopy (XPS), ATR-FTIR and field emission scanning electron microscopy (FESEM). The results showed that the formation of the carbonaceous silicate barrier in the surface region of PP/OMMT nanocomposites resulted from the following three processes: (1) The formation of strong acid sites on the MMT sheets, which could promote the degradation of PP and the carbonization of its degradation products; (2) The gases and gas bubbles formed by decomposition of the surfactant and degradation of PP, which pushed the molten sample to the surface; (3) The degradation of PP and the carbonization of the degradation products, which led to accumulation of MMT sheets tightly linked by the char in the surface region.

This study designs Ni–Mg bimetallic catalysts for preparation of multi-walled carbon nanotubes (MWCNTs) from polypropylene (PP). The study further investigates the influence of Mg content on the catalytic activity of Ni catalyst. It is found that bimetallic Ni–Mg catalysts have higher reduction temperature, smaller Ni particle size and improved stability. Consequently, the addition of Mg not only enhances the yield of MWCNTs, but simultaneously improves the morphology and graphitization of MWCNTs. The activities of the bimetallic Ni–Mg catalysts are dependent on their composition. Among the different Ni–Mg bimetallic catalysts ration, Ni–Mg catalyst shows the highest activity when the ratio of Ni/Mg is 9/1. Moreover, the obtained MWCNTs presents smooth surface with highest graphitization degree. With our bimetallic Ni–Al catalyst, it is promising to achieve mass production of MWCNTs by using waste polymers as feedstock.

Polypropylene (PP) has some disadvantages when used in food packaging: PP does not have antibacterial properties, and it exhibits low barrier properties. In this study, nanocomposites of PP filled with different amounts of silver-decorated multiwalled carbon nanotubes (MWCNTs-Ag) were fabricated. A new nanomaterial with silver had the advantage of providing antibacterial capabilities, and the contribution of MWCNTs was to reinforce mechanical properties. PP was melt-blended with MWCNTs-Ag, but the ensuing problem was the poor interfacial interaction of fillers with the polymer matrix, especially at high filler content. Nonetheless, a small quantity of fillers resulted in the following improvement in nanocomposite properties, relative to neat PP: better antibacterial ability, lower water vapor permeation flux, lower oxygen barrier performance, higher thermostability, faster crystallization rate and higher tensile strength. Therefore, nanocomposites formed from modifying PP with a low content of MWCNTs-Ag show promise in the field of packaging and medical material applications.