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     

基体树脂对长玻璃纤维增强PP力学性能的影响

采用在线混合设备制备了长玻璃纤维(LGF)增强聚丙烯(PP)复合材料(LGF-PP),研究了基体性质及界面相容剂对LGF-PP力学性能的影响。基体树脂熔体流动速率的增加,使最终LGF-PP中的玻璃纤维长度从5.63 mm增至8.56 mm,提高了力学性能。与均聚PP比较,以共聚PP为基体树脂的LGF-PP冲击强度高出约10%,但其他性能略差。界面相容剂有利于增强玻璃纤维与PP的界面结合,拉伸强度和拉伸模量明显增加,但是冲击强度降低了20%～30%。     

木粉增强聚丙烯力学性能的改善方法

以废弃木粉为增强材料,制备了木粉增强聚丙烯复合材料,研究了改善废弃木粉增强聚丙烯复合材料力学性能的途径。结果表明,通过适当的处理方法对木粉进行表面处理、对基体树脂进行改性,可以有效地提高复合体系的界面粘接强度,能大幅度改善复合体系的力学性能;采用短切玻璃纤维及玻璃纤维毡与废弃木粉组合,可以获得力学性能很高、能作为结构材料使用的复合材料。     

The effect of fiber concentration on mechanical and thermal properties of fiber‐reinforced polypropylene composites

A novel composite material consisting of polypropylene (PP) fibers in a random poly(propylene‐co‐ethylene) (PPE) matrix was prepared and its properties were evaluated. The thermal and mechanical properties of PP–PPE composites were studied by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) with reference to the fiber concentration. Although, by increasing PP fiber concentration in PPE, no significant difference was found in melting and crystallization temperatures of the PPE, the storage, and the tensile and flexural modulus of the composites increased linearly with fiber concentrations up to 50%, 1.5, 1.0, 1.3 GPa, respectively, which was approximately four times higher than that for the pure PPE. There is a shift in glass transition temperature of the composite with increasing fiber concentration in the composite and the damping peak became flatter, which indicates the effectiveness of fiber–matrix interaction. A higher concentration of long fibers (>50% w/w) resulted in fiber packing problems, difficulty in dispersion, and an increase in void content, which led to a reduction in modulus. Cox–Krenchel and Haplin–Tsai equations were used to predict tensile modulus of random fiber‐reinforced composites. A Cole–Cole analysis was performed to understand the phase behavior of the composites. A master curve was constructed based on time–temperature superposition (TTS) by using data over the temperature range from −50 to 90°C, which allowed for the prediction of very long and short time behavior of the composite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2260–2272, 2005     

Effect of electron beam irradiation on mechanical and dielectric properties of polypropylene films

In the present investigation the effect of electron beam irradiation on the mechanical properties of thin films of Polypropylene (PP) were measured. The dielectric properties of PP films were carried out in the frequency range from 20 Hz to 1 MHz at various DC bias potential. All measurements were carried out at room temperature. It is found that the electron beam irradiation caused an increase in Young's Modulus of PP film dose of up to 70 kGy were applied, but tensile strength and % elongation at break were found to be decrease with the increasing dose rate. The significant changes were observed in the case of dielectric constant and dielectric loss for electron irradiated PP films. The DSC results indicate that irradiation on PP films changes the thermal behavior. Minor differences in FTIR spectra were observed after irradiation treatment. It is observed that, the effect of radiation damage results in improvement in mechanical strength of the films. The increased dielectric constant and dependence of the bias voltage in case of irradiated and unirradiated PP films has been reported. It is suggested that, the PP films modified with the electron beam irradiation can be used as a good dielectric material for different electronic devices. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical properties of polypropylene fibers produced from the binary polymer blends of different molecular weights

The mechanical properties of multifilament yarns, spun from the blends of a plastic‐grade polymer with a fiber‐grade CR‐polymer in the composition range of 10–50 wt % added, were investigated. The predicted modulus of a two‐phase blend, calculated from several representative equations, was compared with the elastic modulus of drawn yarns, determined from the stress vs. strain curve and dynamic modulus obtained from the sound velocity measurements. The best fit was achived with the Kleiner's simplex equation. For both the static and dynamic elastic modulus, the largest negative deviation is seen at the 80/20 and 60/40 plastic/fiber‐grade polymer blend composition, while the largest positive deviation is seen at the 90/10 plastic/fiber‐grade polymer blend composition, suggesting good compatibility of both polymers, when only a small percent of the fiber‐grade CR‐polymer is added. Improved spinnability and drawability of blended samples led to the yarns with the tensile strength over 8 cN/dtex, elastic modulus over 11 GPa and dynamic modulus over 15.5 GPa. Structural investigations have shown that the improved mechanical behavior of blended samples, compared to the yarn spun from the pure plasic‐grade polymer, is the consequence of a higher degree of crystallinity, and above all, of a much higher orientation of macromolecules. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1211–1220, 2000     

Dynamic mechanical and mechanical properties of polypropylene/poly(vinyl butyral)/mica composites

Three-component composites consisting of polypropylene (PP) matrix, poly(vinyl butyral) (PVB) modifier, and mica filler at various ratios of matrix to modifies and a constant mica content (30 wt %) were prepared by using two different kinds of PVB, viz., PVB and PVB-P. By correlating with the morphology, the dynamic mechanical and mechanical properties of the composites are studied in detail. PVB component in PP/PVB/mica composites cannot display a reinforcing effect to PP/mica binary composites, while impact strength of the composites are reduced further. It associates with incompatibility between PP and PVB, and as well as higher glass transition temperature of PVB. For PP/PVB-P/mica composites, stiffness decreases and, meanwhile, impact strength increases when PVB-P content is 7 wt %. The improvement of impact strength on PP/mica binary composites at the composition is due to a little affinity between the PP matrix and the plasticizer of PVB-P. Moreover, a minor amount of PP-g-MA in the 63/7/30 PP/PVB/mica composites only acts as an adhesion promoter. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2003–2011, 1997     

Quantification of the Young's modulus for polypropylene: Influence of initial crystallinity and service temperature

In this study, the mechanical properties of isotactic polypropylene (iPP) materials with different crystallinities at room and elevated temperatures were investigated. In order to obtain samples with a certain range of crystallinity, and to ensure a uniform microstructure of these samples, the iPP samples obtained by injection molding required melt compression molding and controlled annealing. In the macromechanical studies, the experimental results showed that the storage modulus and Young's modulus of polypropylene were sensitive to the service temperature. The crystallinity also had a great influence on this relationship. A function was proposed to evaluate the dependence of the Young's modulus of polypropylene on initial crystallinity and service temperature, and tested based on experimental data. The Young's modulus of iPP is reduced by about 90% when the service temperature rises from 25 to 125 °C. Moreover, the reduced value in Young's modulus between polypropylene having the highest and lowest crystallinity was reduced from 214.55 to 56.75 MPa. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48581.     

Fiber preparation and mechanical properties of recycled polypropylene for reinforcing concrete

Polypropylene (PP) fibers have been widely used to reinforce concrete footpaths as an alternative to steel mesh. The reinforcing effect of the PP fiber is directly proportional to its tensile strength and Young modulus. This research explored the feasibility of using an improved melt spinning and hot drawing process to produce virgin and recycled PP fibers of high mechanical properties in an industrial scale. Commercial grade granules of virgin PP, recycled PP and HPDE were mixed in different proportions in preparing five different types of fibers. All the fibers obtained high tensile strength and Young modulus. A relationship between the structural parameters and mechanical properties was then established. It was observed that the melt spinning and hot drawing process formed both α‐form and β‐form crystals in the PP fibers, and significantly improved crystallinity from about 50% to 80%. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41866.     

Parameters regulating interfacial and mechanical properties of short glass fiber reinforced polypropylene

The performance of thermoplastic composites is known to depend on the intrinsic properties of the two composite components, the quality of the fiber–matrix interface, and the crystalline properties of their matrix. The objective of this work is to characterize the effect of the addition of modified polypropylene (PP) and silane coupling agent on the mechanical and interfacial properties of short fiber reinforced PP composites. Differential scanning calorimetry (DSC), single fiber composite fragmentation tests (SFC), and mechanical testing are used to understand the different parameters regulating the interfacial properties of composites. No influence of the modified PP on the level of crystallinity is observed. Some differences in the size of the spherulites are observed for acrylic acid grafted PP (PP‐g‐AA). Those samples also show lower mechanical properties in spite of good interfacial interactions. Maleic anhydride grafted PP (PP‐g‐MAh) leads to better mechanical performances than PP‐g‐AA. A high MAh content PP‐g‐MAh grade with low viscosity is the best polymeric additive used in the present work. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2047–2060, 2000     

An efficient way to improve the mechanical properties of polypropylene/short glass fiber composites

Enhancement of tensile strength, impact strength, and flexural strength of polypropylene/short glass fiber composites by treating the glass fibers with coupling agent, mixing with maleated polypropylene (MPP) for compatibilization and adhesion, and with nucleating agent for improvement of polypropylene crystallization was studied. The results showed that both the silane coupling agent and MPP enhance tensile strength, impact strength, and flexural strength. In the absence of MPP, the effect of silane coupling agent on the mechanical properties of the composites decreases in the following order: alkyl trimethoxy silane (WD‐10) > γ‐methacryloxypropyl trimethoxysilane (WD‐70) > N‐(β‐aminoethyl)‐γ‐aminopropyl trimethoxysilane (WD‐52), whereas in the presence of MPP, the order changes as follows: WD‐70 > WD‐10 > WD‐52. When the glass fibers were treated with WD‐52, 4,4‐diamino‐diphenylmethane bismaleimide (BMI) can further enhance the mechanical properties of the composite. The three kinds of strengths increase with MPP amount to maximum values at 5% MPP. As a nucleating agent, adipic acid is better than disodium phthalate in improving the mechanical properties, except for the notched impact strength. Wide‐angle X‐ray diffraction showed that the adipic acid is an α‐type nucleating agent, whereas disodium phthalate is a β‐type nucleating agent. Blending with styrene–butadiene rubber can somewhat improve the notched impact strength of the composites, but severely lowers the tensile strength and bending strength. Scanning electron micrographs of the broken surface of the composite showed greater interfacial adhesion between the glass fibers and polypropylene in the modified composite than that without modification. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1414–1420, 2005     

Phase transformation and mechanical properties of halloysite nanotubes‐modified isotactic polypropylene filaments

Phase transformation and mechanical properties of isotactic polypropylene (iPP) with well‐distributed 0.3, 0.8, and 1.2 wt % halloysite nanotubes (HNTs) are studied. The spatial distribution of HNTs in the iPP matrix is analyzed using transmission electron microscopy and found to be homogeneously dispersed. Phase transformation from molten to solid states is characterized by polarized optical microscopy under an isothermal condition at different temperatures and differential scanning calorimetric in cooling and heating at different rates. Average size of spherulites, the degree of undercooling and total solidification time of iPP decrease as the amount of HNTs increases, suggesting HNTs act as nucleation sites for iPP. More interestingly, the wide‐angle X‐ray diffraction analysis only showed the formation of the α‐form iPP crystallites for the extruded filament, while kinetics results indicating the existence of β‐form crystals. These results together demonstrated the presence of HNTs leads to heterogeneous phase distribution which enhances the mechanical strength of the iPP filaments without reducing their ability for elongation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44714.     

聚丙烯/分子筛共混纤维的结构与性能

用钛酸酯偶联剂对分子筛进行表面处理,按一定比例与聚丙烯(PP)切片共混纺丝,制得PP/分子筛共混纤维,研究PP/分子筛共混纤维的结构与性能。结果表明:当纤维中分子筛的质量分数为1%时,PP/分子筛共混纺丝纤维的可纺性好,断裂强度比纯PP纤维提高31.85%,上染率提高44.86%,初始模量、断裂功、回潮率均有所提高;与纯PP纤维相比,PP/分子筛共混纤维的结晶度略小、晶粒变大,取向度降低,纤维的染色性、吸湿性得到改善。分子筛与偶联剂发生化学反应,有利于分子筛和PP的结合,适当的分子筛含量时,纤维的力学性能有所提高。     

硅酸钠模数对无机聚合物力学性能与微观结构的影响

用模数m=1.0、1.2、1.4和1.6的4种硅酸钠溶液作激发剂制备偏高岭土基无机聚合物,通过强度测试、红外分析(IR)、X线衍射(XRD)和扫描电镜(SEM)等方法考察激发剂模数对无机聚合物力学性能和微观结构的影响。结果表明:模数在1.0~1.6变化时,激发剂中硅氧四面体呈低聚合态;随养护时间延长,无机聚合物抗压强度和抗折强度提高,m=1.2的无机聚合物28 d抗压强度最高(74.6 MPa),抗折强度为11.2 MPa;4种无机聚合物主体相均呈非晶态,结构上由凝胶体和残留原料颗粒组成,其中,m=1.2时无机聚合物的显微结构最平整。     

Effects of 1-n-tetradecyl-3-methylimidazolium bromide on the properties of polypropylene

In this study, 1-n-tetradecyl-3-methylimidazolium bromide ([C₁₄mim]Br), one kind of imidazolium ionic liquids (imi-IL), was incorporated into polypropylene (PP) via melting blend. The structure and properties of PP/[C₁₄mim]Br blend were investigated by differential scanning calorimetry (DSC), dynamical mechanical analysis (DMA), and thermogravimetric analysis (TGA). DSC results show that the [C₁₄mim]Br has effects on the melting and crystallization process so that PP and PP/[C₁₄mim]Br blends (weight ratio is 100/3) have different melting and crystallization temperature. Results of DMA show that the [C₁₄mim]Br has the effects on the plasticization and crystallization of PP, and the glass transition temperature (T_g) of PP decreases around 11°C when 3 weight shares of [C₁₄mim]Br were incorporated into 100 weight shares of PP. Moreover, both tensile strength and impact strength of PP have been improved reasonably in this situation. TGA also shows the thermal stability of PP is not affected by the [C₁₄mim]Br, which was incorporated into it though its molecule is small. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and mechanical properties of polypropylene/clay nanocomposites for automotive parts application

Nanocomposites of polypropylene with organically modified clays were compounded in a twin‐screw extruder by a two‐step melt compounding of three components, i.e., polypropylene, maleic anhydride grafted polypropylene (PPgMA), and organically modified clay. The effect of PPgMA compatibilizers, including PH‐200, Epolene‐43, Polybond‐3002, and Polybond‐3200, with a wide range of maleic anhydride (MA) content and molecular weight was examined. Nanocomposites' morphologies and mechanical properties such as stiffness, strength, and impact resistance were investigated. X‐ray diffraction patterns showed that the dispersion morphology of clay particles seemed to be determined in the first compounding step and the further exfoliation of clays didn't occur in the second compounding step. As the ratio of PPgMA to clay increased, the clay particles were dispersed more uniformly in the matrix resin. As the dispersibility of clays was enhanced, the reinforcement effect of the clays increased; however, impact resistance decreased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 427–433, 2005     

Preparation and mechanical properties of high‐performance short ramie fiber‐reinforced polypropylene composites

Short ramie fiber (RF) was used to reinforce the polypropylene (PP). The composites were prepared in a twin‐screw extruder followed by injection molding. The experimental results showed that both the strength and the modulus of the composites increase considerably with increasing RF content. The tensile strength and flexural strength are as high as 67 and 80 MPa by the incorporation of ramie up to 30 wt %. To the best of our knowledge, this is one of the best results for short natural fiber‐reinforced PP composites. However, the preparation method in this study is more simple and economic. This short RF‐reinforced PP composites extend the application field for short‐nature fiber‐reinforced PP composites. Morphological analysis revealed that it is the high aspect ratio of the fiber and good interfacial compatibility that result in the high performance of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

高强高模维纶纤维的表面修饰及其在水泥中的分散性

目前高强高模维纶纤维由于缺乏合理的分散方案且分散性不佳,极大地限制了在工程领域的应用。为了解决这一问题,采用聚乙烯醇磷酸酯（TFOPVA）分散剂对高强高模维纶纤维进行表面涂层改性处理,并以此为基础制备维纶纤维/水泥基复合材料。利用X射线光电子能谱仪（XPS）、场发射扫描电子显微镜（SEM）、万能材料试验机、纤维强伸度仪（XQ-1A）等对改性前后的维纶纤维的分散性及其复合材料的力学性能进行测试和表征。结果表明：当TFOPVA上浆质量分数和吸附量分别为1%和5mg/g时纤维分散效果最佳;维纶纤维短丝在水泥基体中的分散系数提高33.3%;TFOPVA处理后的维纶纤维单丝断裂强度增加4.5%,与维纶纤维之间能牢固结合;TFOPVA改性后的维纶纤维/水泥复合材料的抗压强度和抗折强度相比改性前分别提高了27.9%和21.2%。     

Influence of nanoclay and coupling agent on the physical and mechanical properties of polypropylene/bagasse nanocomposite

In this work, the effects of nanoclay (1–4 wt %) and coupling agent (2 and 4 wt %) loading on the physical and mechanical properties of nanocomposites are investigated. Composites based on polypropylene (PP), bagasse flour, and nanoclay (montmorillonite type) was made by melt compounding and then compression molding. When 1–3 wt % nanoclay was added, the tensile properties increased significantly, but then decreased slightly as the nanoclay content increased to 4%. The impact strength was 6% lower by the addition of 1 wt % nanoclay, it was decreased further when the nanoclay content increased from 1 to 4%. Finally, the water absorption of PP/bagasse composites was lowered with the increase in nanoclay content. Additionally, the coupling agent, 4 wt % MAPP, improved the mechanical and physical properties of the composites more than the 2 wt % MAPP. From these results, we can conclude that addition of nanoclay enables to achieve better physical and mechanical properties in conventional composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009