Bamboo fiber reinforced polypropylene composites and their mechanical,thermal, and morphological properties

Short bamboo fiber reinforced polypropylene composites were prepared by incorporation of various loadings of chemically modified bamboo fibers. Maleic anhydride grafted polypropylene (MA‐g‐PP) was used as compatibilizer to improve fiber–matrix adhesion. The effects of bamboo fiber loading and modification of the resin on the physical, mechanical, thermal, and morphological properties of the bamboo reinforced modified PP composites were studied. Scanning electron microscopy studies of the composites were carried out on the interface and fractured surfaces. Thermogravimetric analysis and IR spectroscopy were also carried out. At 50% volume fraction of the extracted bamboo fiber in the composites, considerable increase in mechanical properties like impact, flexural, tensile, and thermal behavior like heat deflection temperature were observed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical and thermal properties of polypropylene/sugarcane Bagasse composites

To determine the possibility of using sugarcane bagasse (SCB) waste as reinforcing filler in the thermoplastic polymer matrix, SCB‐reinforced polypropylene (PP) composites were prepared. The PP and SCB composites were prepared by the extrusion of PP resin with 5, 10, 15, and 20 wt % of SCB filler in a corotating twin screw extruder. The extruded strands were cut into pellets and injection molded to make test specimens. These specimens were tested for physicomechanical properties such as tensile, flexural, Izod, and Charpy impact strengths, density, water absorption, and thermal characteristics, namely, heat deflection temperature (HDT), melt flow index, and thermogravimetric analysis. It was found that the flexural strength increased from 23.66 to 26.84 MPa, Izod impact strength increased from 10.499 to 13.23 Kg cm/cm, Charpy impact strength increased from 10.096 to 13.98 Kg cm/cm, and HDT increased from 45.5 to 66.5°C, with increase in filler loading from 5 to 20% in the PP matrix. However, the tensile strength and elongation decreased from 32.22 to 27.21 MPa and 164.4 to 11.20% respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3827–3832, 2007     

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     

Thermal and mechanical properties of polypropylene/wood‐flour composites

In this research, polypropylene/wood‐flour composites (WPCs) were blended with different contents of wood and/or maleated polypropylene (MAPP) and clay. We found that the addition of MAPP or clay in the formulation greatly improved the dispersion of the wood fibers in the composite; this suggested that MAPP or clay may have played the role of an adhesion promoter in the WPCs. The results obtained with clay indicate that it also acted as a flame retardant. The thermal tests carried out with the produced samples showed an increased crystallization temperature (T_c), crystallinity, and melting temperature (T_m) with wood loading. The increase of the two former parameters was explained by the incorporation of wood flour, which played the role of nucleating agent and induced the crystallization of the matrix polymer. On the other hand, the T_m increase was ascribed to the insulating properties of wood, which hindered the movement of heat conduction. The effects of UV irradiation on T_m and T_c were also examined. T_c increased with UV exposure time; this implied that UV degradation generated short chains with low molecular weight that could move easily in the bulk of the sample and, thus, catalyze early crystallization. The flexural strength and modulus increased with increasing wood‐flour content. In contrast, the impact strength and tensile strength and strain decreased with increasing wood‐flour content. All of these changes were related to the level of dispersion of the wood flour in the polymeric matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of repetitive processing,wood content,and coupling agent on the mechanical,thermal, and water absorption properties of wood/polypropylene green composites

In an effort to determine to what extent natural fiber/plastic composites were recyclable, this study conducted repetitive processing cycles on wood flour/polypropylene composites through extrusion up to three times followed by injection molding. Mechanical properties of the composites, containing 10–50?wt% wood flour and with/without addition of 3?wt% maleic anhydride polypropylene (MAPP) as coupling agent, were evaluated by conducting tensile test, thermal analysis, and water absorption test. Repetitive processing as well as wood content and coupling agent addition influenced physical properties of the composites. MAPP functioned well in improving fiber-matrix adhesion in terms of mechanical properties. Repetitive processing did not deteriorate the composite’s properties; rather opposite effect was shown. Thermal analysis indicated that the alteration in properties was contributed by the molecular condition of the polypropylene matrix. Water absorption increased with the wood flour content but reduced when MAPP was added and with more processing cycles.     

Mechanical and thermal properties of polypropylene/modified basalt fabric composites

Basalt fabric (BF) was first treated with silane coupling agent KH550, modified basalt fabric (MBF) was obtained. Then MBF were molded with polypropylene (PP) matrix, and polypropylene/modified basalt fabrics (PP/MBF) composites were obtained. The influence of concentration and treating time of KH550 on MBF were characterized by hydrophilicity and lipophilicity. The tensile strength and morphology of basalt fabric were tested by single filament strength tester and scanning electron microscopy. The mechanical properties of composites were measured with electronic universal testing machine and impact testing machine, and the thermal properties were tested by thermogravimetric analysis and dynamic mechanical analysis. The results showed that the lipophilicity of MBF is improved significantly by KH550 while the tensile is nearly damaged. The mechanical properties of composites are larger than that of pure PP, among which the impact property was improved the most, showing 194.12% enhancement. The thermal stability and dynamic viscoelasticity were better than pure PP; furthermore, the concentration of KH550 virtually had no effect on the thermal stability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42504.     

Dynamic mechanical properties,crystallization behaviors,and low‐temperature performance of polypropylene random copolymer composites

In this study, polypropylene random copolymer (PPR) composites were prepared by the addition of either three kinds of thermoplastic rubber (TPR) modifiers (types 2088A, 2095, and 2096) or an ethylene–octene copolymer (POE)/high‐density polyethylene (HDPE; 2 :1 w/w) blend. Differential scanning calorimetry, wide‐angle X‐ray diffraction, and dynamic mechanical analysis were used to characterize the crystallization behaviors and dynamic mechanical properties of the PPR composites. The results indicated that PPR/POE/HDPE and PPR/TPR2088A had better comprehensive mechanical properties, especially the low‐temperature toughness among all of the samples. The obtained PPR/POE/HDPE blends showed a high toughness and good stiffness in the temperature interval from ?10 to 23°C with the addition of only 10 wt % POE/HDPE. When the temperature continued to fall below ?10°C, the PPR/TPR2088A composites exhibited a better impact toughness without a loss of too much stiffness. The good low‐temperature toughness of those two composites was attributed to both the decrease in the crystallinity and the uniform dispersion, obvious interfacial adhesion, and cavitation ability of POE/HDPE and TPR2088A in the PPR matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42960.     

Low dielectric loss LNT/PEEK composites with high mechanical strength and dielectric thermal stability

(3-Aminopropyl)triethoxysilane treated La_(2−x)/3Na_0.06TiO₃ (x = 0.06) (LNT) microparticles filled polyetheretherketone (PEEK) composites were prepared using hot pressing process. The effects of variation of LNT ceramic filling fraction on dielectric properties, water absorption, thermal stability and mechanical strength were investigated. All composites demonstrate low water absorption (less than 0.4%) when the ceramic filling fraction is lower than 0.6V_f. The obtained composites exhibited dielectric permittivities varying from ~4 to ~22 as the ceramic fillers increased from 0.1 to 0.8V_f and low losses (~10⁻⁴ @1 MHz, 3~5 × 10⁻³ at the frequencies of microwave (10 GHz) and millimeter wave (29-50 GHz), respectively). The mechanical strength, dimensional and dielectric thermal stability of the composite are remarkably improved by the addition of LNT ceramic fillers. A composite with near zero temperature coefficients of dielectric permittivity or resonant frequency and flexural strength of ~140 MPa could be obtained. The out-of-plane coefficient of thermal expansion (CTE) could be reduced to ~20 ppm/°C as the ceramic filler loading reached 0.7V_f.     

Mechanical properties,thermal, and crystallization behavior of polypropylene composites reinforced by starch and wasted cotton cloth

In this study, wasted cotton cloth was bonded with soluble starches as an adhesive, then dried, cut into fiber fragments and filled into polypropylene (PP) to achieve resource efficiency. The mechanical, thermal, and crystallization properties of the composites were characterized. The results indicated that with the addition of wasted cotton cloth treated without or with silane coupling agent (RC or TRC), PP composites' tensile strength, impact strength, and flexural strength have been improved. The heat distortion temperatures increased slowly, indicating that wasted cotton cloth filled into PP can be turned back into useful items without degradation of PP composites exhibited. Thus, it is a good avenue for the utilization of an otherwise wasted cotton cloth resource. The crystallization activation energy, nucleation constant, and folding surface free energy of PP were markedly reduced in PP/RC composites and its compatibilized composites. The value of F(T) gradually increased with the increasing relative degree of crystallinity. The addition of wasted cotton cloth could significantly reduce the spherulitic size of PP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of compatibilizers on mechanical properties,crystallization, and morphology of polypropylene/scrap rubber dust blends

Polypropylene blends containing a dispersed phase of scrap rubber dusts obtained from sport shoes manufacture; midsole (M, vulcanized EVA foam) and outsole (O, vulcanized rubber blend of NR, SBR, and BR) were studied. The influence of various compatibilizers on the mechanical properties of these blends were investigated. Significant development of impact strength was attained by using 6 and 10 phr of styrene–ethylene–butylene–styrene (SEBS) and maleic anhydride‐grafted styrene–ethylene–butylene–styrene (SEBS‐g‐MA) as compatibilizers for both compounds filled with midsole and outsole dusts. The tensile strength of each compound was slightly decreased when the compatibilizer loading increased, whereas the elongation at break was significantly increased. The enhancements of the impact strength and the elongation at break are believed to arise from reduction of interfacial tension between two phases of the rubber and the PP, which results in some reduction of the particle size of the fillers. Scanning electron microscopy (SEM) confirmed the evidence of the reduction of scrap rubber dust into small rubber particle sizes in the compound, and also showed the occurrence of some fibrils. Optical microscopy (crossed polars) observations suggested that the addition of the rubber dust resulted in a less regular spherulite texture and less sharp spherulite boundaries. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 148–159, 2002     

Effect of different compatibilizers on the mechanical and thermal properties of starch/polypropylene blends

Starch was treated with three kinds of compatibilizers (coupling agents or modifying agents), KH‐550, KH‐570, and glycerin monostearate. Blends of polypropylene (PP) and treated starch were prepared by a twin‐screw extruder. The effects of the starch before and after treatments and the kinds and contents of the compatibilizers on the mechanical and thermal properties of the PP/starch blends were investigated in this study. We found that the mechanical properties (tensile strength, impact strength, and elongation at break) of the blends were obviously improved with increasing content of different kinds of compatibilizers. Meanwhile, the most significant improvement in the mechanical properties was obtained in the samples containing just a 1 wt % loading of compatibilizers, and KH‐570 had the best improved effects among the different kinds of compatibilizers. The results of thermogravimetric analysis demonstrate that to some extent, the thermal stability of the PP/starch blends was improved after the addition of compatibilizers. Scanning electron microscopy showed that the dispersion of starch in the PP matrix and adhesion between the starch and PP matrix were obviously improved after the addition of compatibilizers. KH‐570 not only had the best improved effects among the coupling agents but also still acted as a similar plasticizer. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43332.     

Impact of compression molding conditions on the thermal and mechanical properties of polyethylene

Compression molding is a current technique in polymer processing. Despite numerous studies, effect of molding pressure on physical properties has surprisingly not been fully investigated. In this study, the thermal and mechanical behavior of the compression‐molded polyethylene were thus explored to better grasp the relationship between processing parameters and ensuing properties. The effect of the molding temperature, pressure, cooling rate, and temperature profile on the tensile and flexural moduli as well as melting point of polyethylene was studied. We conclude that higher tensile and flexural moduli are obtained by increasing pressure and molding temperature, as well as decreasing the cooling rate. Our results were corroborated by X‐ray diffraction and differential scanning calorimetry measurements. Moreover, the use of a temperature gradient with different temperatures for the upper and bottom plates of the mold leads to asymmetric samples whose tensile and flexural moduli are improved. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46176.     

Graphene/polypropylene nanocomposites with improved thermal and mechanical properties

Small amount of large surface area graphene (G) is expected to significantly alter functional properties of polymers. The property enhancement is a function of degree of exfoliation and dispersion of G as well as its compatibility with base polymer. However, nonpolar nature of polyolefins such as polypropylene (PP) restricts homogeneous dispersion of G, leading to significant agglomeration and properties reduction. In this work, two compatibilizers, poly (ethylene-co-butyl acrylate) (EBA) (new compatibilizer) and PP-grafted-maleic anhydride (MA-PP) (conventional compatibilizer) were compared to enhance the dispersion efficacy of G in PP. The EBA-compatibilized nanocomposites exhibited 44% increase in the Young's modulus compared to 32% increment in MA-PP-compatibilized nanocomposites. Higher elongation at break for EBA-compatibilized nanocomposites is attributed to lower degree of crystallinity in these nanocomposites. On the other hand, EBA-compatibilized nanocomposites showed significantly improved thermal stability compared to MA-PP-compatibilized nanocomposites. The results indicate that EBA may act as a potential compatibilizer for G/PP nanocomposites.     

Morphologies,crystallization, and mechanical properties of PLA-based nanocomposites: Synergistic effects of PEG/HNTs

In this study, the compounding modifier poly(ethylene glycol)/halloysite nanotubes (PEG/HNTs) was prepared by supersonic vibration and dynamic vacuuming. A series of poly(lactic acid) (PLA)/PEG and PLA/PEG/HNT composites were fabricated using a twin-screw extruder. Fourier transform infrared spectroscopy indicated that the hybrid between PEG and HNTs had no evident chemical interaction via supersonic vibration and dynamic vacuuming. The dispersed morphology of the compounding modifier in the PLA matrix was tested by high-resolution scanning electronic microscopy and transmission electron microscopy. The results showed that the low content of PEG/HNTs presented a good dispersion morphology. The binding energy of the PLA-based composites was studied through contact angle measurements. The results showed that PEG and PEG/HNTs can decrease the water contact angle of PLA, and that the binding energy between PEG and HNTs is higher than that of PLA/HNTs, which leads to more location of HNTs in the PEG phase. The crystallization behavior of PLA-based composites was examined by wide-angle X-ray diffraction and differential scanning calorimetry. The results suggested that the addition of PEG and PEG/HNTs effectively enhanced the crystallization of PLA and that the diffraction peak intensity of the PLA-based composites reached a maximum when the content of PEG/HNTs was 1.2 wt %. The spherulite morphology indicated that the addition of PEG resulted in perfect spherulites. The mechanical properties of PLA-based composites were analyzed with a universal testing machine and impact tester, which confirmed that the tensile strength and impact strength of the PLA-based composites increased slightly when the content of the PEG/HNT modifier was 1.2 wt %, while the tensile modulus of the PLA-based composites increased distinctly. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47385.     

The flame retardancy and mechanical properties of jute/polypropylene composites enhanced by ammonium polyphosphate/polypropylene powder

Surface flame retarded jute/polypropylene composites (J/P/A) were prepared via a modified strategy: the mixture of PP and APP powder was spread over the surface of jute/PP nonwoven felts, and then transformed into the flame retarded layer by the hot pressing process. The flame retardancy and thermal properties of composites were analyzed by limit oxygen index (LOI), horizontal burning rate (HBR), thermogravimetric analyses (TGA), and differential scanning calorimetry (DSC). We demonstrated that the flame retardancy and mechanical properties of composites was significantly improved compared with those obtained by presoaking the nonwoven fiber felts in flame retardant (FR) solvent before hot pressing. The mechanism of thermal degradation of jute fiber and flame‐retardant mechanism of composites were analyzed by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and scanning electron microscope (SEM). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43889.     

PVDF/PMMA/Basalt fiber composites: Morphology,melting and crystallization,structure, mechanical properties,and heat resistance

This paper is to study the effect of basalt fiber on morphology, melting and crystallization, structure, mechanical properties, melting and crystallization of PVDF/PMMA composites using scanning electron microscopy (SEM), X‐ray, differential scanning calorimeter (DSC), dynamical mechanical analysis (DMA), etc. Basalt fiber may disperse well in PVDF/PMMA matrix and form compact fiber network, and this makes tensile and flexural strength of fiber reinforced PVDF/PMMA composites get to the maximum value of 62 and 102 MPa, respectively. However, the mechanical properties begin to decrease when basalt fiber content exceeds 20 wt %. The α and β phase of PVDF can coexist in composites, and basalt fiber and PMMA can induce β phase of PVDF. The melting temperature of PVDF in composites is kept unchanged, but the degree of crystallinity of composites increases as basalt fiber content increase, and then declines when fiber content exceeds 20%. The DSC results confirm that the nucleation ability of PVDF is enhanced by basalt fiber. Also, the heat resistance of PVDF/PMMA composite is improved from 133 to 146.1°C due to basalt fiber. The DMA shows that basalt fiber increases the storage modulus of PVDF/PMMA composite, and the loss peak of PMMA increases from 116.1 to 130°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40494.     

Effect of tensile rates on thermal and mechanical properties of porous PTFE composites

To achieve polymer-matrix composites for sealing materials with thermostability and toughness, PTFE composites filled with short glass fibers (SGFs) were hyperthermal stretched to prepare a substrate material with high thermal stability and porosity. The effects of various tensile rates on the thermal and mechanical properties and morphologies were investigated. The results revealed that the thermal stability could be improved slightly and the thermal expansion coefficient of composites increased by the tensile rate. Through observing the morphologies, tensile process produced cavities and the increased tensile rate had negligible effects on porosity, which also could be proved by density test. From mechanical properties analysis, stretched composites exhibited that the tensile strength increases first and then decreases with the increased tensile rate. Although the variation tendency of Young's modulus is similar to that of tensile strength, which is smaller than that of unstretched composite. When the tensile rate reached 50 mm·min⁻¹, the tensile strength and Young's modulus of the stretched composites increased by 65 and 9% to maximum, respectively. Meanwhile, elongation at break and shore hardness decreased. The thermal and mechanical properties improvement could be ascribed to the strain-induced crystallization and crystal alignment. In addition, the interplanar spacing and grain size were inversely proportional to the tensile rate. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48175.     

Effects of SiC whisker addition on mechanical,thermal, and permeability properties of porous silica-bonded SiC ceramics

The effects of SiC whisker addition into nano-SiC powder-carbon black template mixture on flexural strength, thermal conductivity, and specific flow rate of porous silica-bonded SiC ceramics were investigated. The flexural strength of 1200°C-sintered porous silica-bonded SiC ceramics increased from 9.5 MPa to 12.8 MPa with the addition of 33 wt% SiC whisker because the SiC whiskers acted as a reinforcement in porous silica-bonded SiC ceramics. The thermal conductivity of 1200°C-sintered porous silica-bonded SiC ceramics monotonically increased from 0.360 Wm^–1K^–1 to 1.415 Wm^–1K^–1 as the SiC whisker content increased from 0 to 100 wt% because of the easy heat conduction path provided by SiC whiskers with a high aspect ratio. The specific flow rate of 1200°C-sintered porous SiC ceramics increased by two orders of magnitude as the SiC whisker content increased from 0 to 100 wt%. These results were primarily attributed to an increase in pore size from 125 nm to 565 nm and secondarily an increase in porosity from 49.9% to 63.6%. In summary, the addition of 33 wt% SiC whisker increased the flexural strength, thermal conductivity, and specific flow rate of porous silica-bonded SiC ceramics by 35%, 133%, and 266%, respectively.     

Effects of calcium carbonate and its purity on crystallization and melting behavior,mechanical properties,and processability of syndiotactic polypropylene

Calcium carbonate‐filled syndiotactic poly(propylene) (CaCO₃‐filled s‐PP) was prepared in a self‐wiping, co‐rotating twin‐screw extruder. The effects of CaCO₃ of varying particle size (1.9, 2.8 and 10.5 μm), content (0–40 wt %), and type of surface modification (uncoated, stearic acid‐coated, and paraffin‐coated) on the crystallization and melting behavior, mechanical properties, and processability of CaCO₃‐filled s‐PP were investigated. Non‐isothermal crystallization studies indicate that CaCO₃ acts as a good nucleating agent for s‐PP. The nucleating efficiency of CaCO₃ for s‐PP was found to depend strongly on its purity, type of surface treatment, and average particle size. Tensile strength was found to decrease, while Young's modulus increased, with increasing CaCO₃ content. Both types of surface treatment on CaCO₃ particles reduced tensile strength and Young's modulus, but improved impact resistance. Scanning electron microscopy (SEM) observations of the fracture surfaces for selected CaCO₃‐filled s‐PP samples revealed an improvement in CaCO₃ dispersion as a result of surface treatment. Finally, steady‐state shear viscosity of CaCO₃‐filled s‐PP was found to increase with increasing CaCO₃ content and decreasing particle size. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 201–212, 2004     

Mixed percolating network and mechanical properties of polypropylene/talc composites

Injected polypropylene/talc composites were studied to evaluate the conditions leading to the formation of a mixed talc/polymer crystalline lamella percolating network and the influence of such a network on the nanocomposite mechanical properties. The talc was either conventional micrometer‐sized (conventional talc) or submicrometer‐sized particles (μ‐talc). In the case of μ‐talc, several talc fractions were studied, ranging from 3 to 30 wt %. The nanocomposite crystallinity was characterized with differential scanning calorimetry and wide‐angle X‐ray scattering. Talc was found to act as a nucleating agent, and only the α phase was detected. Through quantification on a Wilchinsky diagram, the talc particles were found to lie in the sample plane, the polypropylene crystalline lamellae being orthotropically distributed perpendicularly to the talc particles. The mechanical properties of the composites were tested in different directions by tensile and compression tests. The mechanical behavior of the composites confirmed the microstructural model. For low talc loadings, the composite moduli could not be well fitted by a law of mixtures. The large difference between the observed and predicted moduli was attributed to the formation of a mixed percolating network, including talc particles and polypropylene crystalline lamellae. At high talc loadings, when the mixed percolating network was completely formed, the reinforcement could well be described by parallel coupling, which indicated a classical reinforcement mechanism. Finally, the value of the critical talc fraction, at which the mixed percolating network was formed, was examined as a function of talc. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009