Effect of washing on the photo-oxidation resistance of stabilized polypropylene fibers

The effect of aqueous detergent and benzine washing on the photo-oxidation stability of stabilized polypropylene fibers was studied. The fibers were stabilized by higher molecular weight light stabilizers based on 2-hydroxybenzophenones and by thermo-oxidative stabilizers. The content of the light stabilizers in washed fibers was determined, and photo-oxidation curves of the original and washed fibers were measured. The effectiveness of stabilization of the original and the washed fibers was compared with that of 2-hydroxy-4-n-octyloxybenzophenone at identical content of 2-hydroxybenzophenone structural units. Another criterion was comparison of washed and unwashed fibers. Photo-oxidation curves of accelerated aging and induction periods showed that washing with either aqueous detergent or benzine decreases the resistance of fibers to photo-oxidation, i.e., washing lowers the content of stabilizers in fibers. Extraction with benzine exerts a more pronounced effect than washing with water. Extractability by benzine of higher molecular weight stabilizers is considerably lower than with low molecular weight stabilizer. On the basis of experimental results it is assumed that washing of fibers leads to leaching not only of thermo-oxidative stabilizers but also to a decrease in the content of light stabilizers. Derivatives alkylated by tert-butyl are more extractable by benzine, while the nonalkylated derivatives are more extractable by washing with water.     

The relationship between structure and properties in titanium dioxide filled polypropylene

Summary The effect of a pigment grade of titanium dioxide on the morphology, crystallisation and mechanical properties of a typical grade of isotactic polypropylene are described. Pigment particles are able to nucleate additional spherulites, and are incorporated within spherulitic and lamellar morphologies. Measurements of isothermal crystallisation rates using differential scanning calorimetry and hot-stage microscopy show that bulk crystallisation rate is increased by addition of the pigment due to the larger number of spherulites, while the growth rate of the spherulites is unchanged. Addition of the pigment increased tensile modulus, and reduced yield stress. The elongation at break and impact resistance were modulus, and reduced yield stress. The elongation at break and impact resistance were increased by the addition of pigment, showing that particle debonding processes can lead to toughening of the polypropylene matrix.     

Structural,elastic and thermal properties of titanium dioxide filled isotactic polypropylene

Titanium dioxide (TiO₂)-filled isotactic polypropylene (iPP) composites with various contents of TiO₂ were prepared by a locally fabricated extrusion molding machine. The extrudates were melt-pressed at 180 °C and produced as plane sheets of nearly equal thickness by rapid cooling. X-ray diffraction studies reveal a decrease of crystallinity and crystallites size as well as a change of α-, β- and γ-crystalline phases of the neat iPP to the α-form due to filler inclusion. Scanning electron micrographs taken on the fractured surface of the samples show increasing amount of voids with increasing filler content. Tensile strength, elongation-at-break (%) and glass transition temperature of the samples are found to decrease considerably with the increase in TiO₂ content, whereas microhardness decreases slightly with the filler content.     

Effect of an acidic comonomer on thermooxidative stabilization of polyacrylonitrile

This paper presents a study of the reactions involved in stabilization of polyacrylonitrile (PAN) through the effect of various experimental variables on the differential scanning calorimetry (DSC) exotherm and thermogravimetric measurements coupled with Fourier transform infrared (FTIR) spectroscopy, i.e., DSC-FTIR and TG-FTIR. The experimental variables used were the environment of heat treatment (viz. oxidative and inert) and in corporation of an acidic comonomer (viz. itaconic acid). The essential findings include the broadening of the exotherm in an air atmosphere over that in a nitrogen (i.e., inert) atmosphere. This broadening of the exotherm was further enhanced in the presence of the acidic comonomer. Furthermore, the exotherm revealed a doublet character with greater separation of the peaks in case of the copolymer than the homopolymer. Possible explanations of these observations are discussed. © 1995 John Wiley & Sons, Inc.     

相对分子质量对等规聚丙烯性能的影响

选取了6个相对分子质量不同的等规聚丙烯(i PP),研究了相对分子质量对i PP特性黏数和熔体流动速率的影响,并探讨了相对分子质量对i PP力学性能的影响规律。结果表明:i PP的特性黏数和熔体流动速率分别与重均分子量成0.78,-3.84次方关系,特性黏数与熔体流动速率成-0.200次方关系。随着i PP相对分子质量的减小,其弯曲强度、弯曲模量和拉伸强度先增大后减小,而断裂拉伸应变和悬臂梁缺口冲击强度单调递减。     

Correlations between rheological and mechanical properties of mineral filled polypropylene compounds

A comparative study of rheological and mechanical properties of Polypropylene compounds with talc as a mineral filler is presented. It turns out that the main factors determining the mechanical behavior, namely (a) filler concentration, (b) filler particle size, and (c) degree of dispersion, influence the linear viscoelastic properties as well. Thus, a quick method for estimating compound properties from melt rheology is established. © 1994 John Wiley & Sons, Inc.     

Effect of temperature on the dispersion properties of polypropylene fibers

A Biolar PI polarizing interference microscope (a Pluta microscope) attached to a special hot stage was used to study the influence of temperature on the dispersion properties of polypropylene fibers with different deniers (6 D and 90 mm, 6 D and 150 mm, and 12 D and 150 mm) over the temperature range of 30–50°C. This study was carried out with a variable‐wavelength interferometry technique. Constant A of Cauchy's dispersion formula and the oscillation and dispersion energies for light vibrating parallel and perpendicularly to the fiber axis were determined at different temperatures. Microinterferograms are given for illustration. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1135–1141, 2005     

激光表面改性对聚丙烯非织造布性能的影响

采用激光技术对聚丙烯(PP)非织造布进行表面改性处理,探讨了激光功率和进布速度对PP非织造布的面密度、厚度、抗静电性、透气性、断裂强力和色泽度(K/S)的影响。结果表明:激光表面改性对PP非织造布的抗静电性、面密度和厚度影响不大;进布速度对PP非织造布的透气性、断裂强力和K/S的影响比激光功率显著,但是激光功率相比进布速度对接触角的影响更明显;随着进布速度的提高,PP非织造布的断裂强力先增加后减小,透气性、接触角和K/S呈下降趋势;随着激光功率的增大,PP非织造布的透气性先增加后趋于稳定,断裂强力和接触角显著降低,K/S增加;当激光功率为40 W,进布速度为9.0 m/min,激光表面改性处理后的PP非织造布的综合性能较好。     

Effect of hydrothermally synthesized titanium nanotubes on the behaviour of polypropylene for antimicrobial applications

TiO₂ nanotubes (TiO₂‐Ntbs) synthesized by a hydrothermal method were used as filler to prepare polypropylene (PP) composites by melt blending. Their structural properties as well as their biocidal potential were studied. Nanotubes were used either as‐synthesized or organically modified with hexadecyltrimethoxysilane (Mod‐TiO₂). These nanoparticles form secondary structures with sizes around 100 nm that are well dispersed in the polymer matrix, but not homogeneously because agglomerates larger than 1 µm are also seen by transmission electron microscopy. Regarding the properties of the composites, the incorporation of the nanoparticles increased the polymer's crystallinity and thermal stability. The maximum decomposition temperature of the matrix increased by ca 13 °C compared to virgin PP. The nanotubes further increase the spherulite nucleation density, and therefore a reduction in the diameter of spherulites and an increase in their number were observed. Despite the above, the addition of TiO₂ nanoparticles did not modify the mechanical properties of PP. The PP/TiO₂‐Ntb nanocomposites exposed to UVA radiation showed a biocidal behaviour, reducing a colony of Escherichia coli by 81%. © 2015 Society of Chemical Industry     

Effect of charring agent THEIC on flame retardant properties of polypropylene

Tris(2‐hydroxyethyl) isocyanurate (THEIC) was used as charring agent and combined with ammonium polyphosphate (APP) to form an intumescent flame retardant (IFR) for polypropylene (PP). The flame retardancy and combustion performance of PP/IFR composite was tested by limiting oxygen index (LOI), UL‐94 vertical burning test and cone calorimeter. The results showed that PP/IFR composite had highest LOI of 34.8 and obtained V‐0 rating when 30 wt % IFR was loaded and mass ratio APP/THEIC was 2 : 1. The peak heat release (PHRR) and total heat release (THR) values of PP composite containing FRs were remarkably reduced compared with that of pure PP. However, water resistant test demonstrated the PP/IFR composite had poor flame retardant durability, both the LOI value and UL‐94 V‐rating decreased when PP/IFR composite was soaked in water at 70°C after 36 h. The degradation process and the char morphology of IFR and PP/IFR composite were investigated by TGA and SEM images. The possible reaction path between APP and THEIC in the swollen process was proposed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41214.     

注射工艺条件对抗冲共聚PP性能的影响

研究了注射成型工艺条件对抗冲共聚聚丙烯(PP)性能的影响.分析了熔体温度、注射速率、注射压力对抗冲共聚PP微观形态的影响.熔体温度为200～220℃,注射速率为45～90 mm/s,抗冲共聚PP的弯曲模量最大相差近10％,冲击试样的断裂方式发生改变,负荷变形温度最大相差5℃.注射压力的变化对抗冲共聚PP的性能影响不大....     

Effect of polymeric additives on the rheological properties of talc-filled polypropylene

The effect of small amounts of low molecular weight polypropylene oxide on the rheological properties of talc-filled polypropylene composites was studied experimentally using a capillary viscometer. The elastic behavior of the system was investigated by exit pressure and die swell methods. Initial studies showed that the talc filler does not influence the viscosity of the polypropylene but decreases the elasticity of the polymer system. Addition of oligomer concentration in a 40 wt percent talc-filled polypropylene not only decreases the viscosity but also further decreases considerably the elasticity of the filled polymer composite. In both cases about 3 wt percent oligomer cone entration appears to be optimal, and further addition of oligomer does not significantly influence the rheological characteristics of the talc-filled polypropylene composite.     

超支化聚酰胺对聚丙烯及其纤维的性能影响

研究了超支化聚酰胺对聚丙烯(PP)的热性能、漉变性能和力学性能及其纤维的染色性能影响。结果表明:超支化聚酰胺在PP中分散均匀;超支化聚酰胺的加入,改善了PP纤维的染色性,当加入超支化聚酰胺质量分数为8%时,分散蓝的上染率可达70%,改性PP纤维的织物染色牢度均在4级以上;随着超支化聚酰胺含量增大,改性PP表观粘度下降,加工性能得到改善,其力学性能变化不大。     

改性剂对聚丙烯流变性能和发泡行为的影响

在改性聚丙烯PPFP1920中加入丙烯酸类树脂改性剂(记作G200)进行共混改性,制备了PPFP1920/G200复合材料,研究了G200含量对聚丙烯流变性能、发泡行为的影响.结果表明:随着G200含量的增加,复合材料的熔体流动速率大幅降低,复数黏度和低频储能模量提高,低频损耗因子降低,熔体弹性变好,复合材料可发泡性提...     

Effect of rolling temperature on microstructure and tensile properties of polypropylene

Rolling process was carried out with extruded polypropylene as crystalline polymer at various rolling temperatures, and the rolling characteristics, cross‐section morphologies, and tensile properties were investigated. The rolling characteristics were evaluated by springback and dimensional change. The springback increased with increasing rolling temperature. The increment of length was larger than that of width because of the influence of uniaxial drawing by rotation of the rollers. Uniform morphologies were observed at a rolling ratio of 70% and a rolling temperature of 23°C. In contrast, molecular orientation near the surface was higher compared with the inner part when rolled at 70°C. Furthermore, micro spherulitic structures were observed near the surface where recrystallization occurred because of the rising temperature on the specimen surface by friction. Therefore, different morphologies appeared near the surface and in the inner part. Tensile strength was obtained for the rolling direction when rolled at 110°C lower than at other rolling temperatures. It was likely that the molecular orientation was decreased by increasing the springback when rolled at high temperature. POLYM. ENG. SCI., 53:2573–2581, 2013. ©2013 Society of Plastics Engineers     

Effect of titanate coupling agents on mechanical properties of mica-filled polypropylene

The application of titanate coupling agents for the surface modification of mica filler and its reinforcement in polypropylene (PP) has been directed towards improvement in mechanical properties. Four titanate coupling agents, namely neoalkoxy tri(dioctylpyrophosphato) titanate (C₁), neoalkoxy trineodecanoyl titanate (C₂); bis-(acetylacetonato)distearato titanate (C₃), and bis-(acetylacetonato)dipalmitato titanate (C₄) were used in the present investigation. Mica powder (10 μm particle size) was coated with these coupling agents of varying concentration (0.5 to 1 % on the weight of filler) and then blended with polypropylene powder of 10 melt flow index. The mica (10 to 50 wt. %) filled polypropylene samples with and without coupling agents, were injection molded and the mechanical properties of the specimens tested. There is an improvement in the tensile, flexural, and impact strength of PP/mica samples coupled with titanates. The best performance in terms of yield stress and flexural strength was observed in PP/mica samples having 0.7% C₁, titanate coupling agent. The fracture behavior of mica filled PP has also been studied using a scanning electron microscope.     

TMPTMA和TAIC对PP发泡材料性能的影响

在过氧化二异丙苯引发下,分别以三羟甲基丙烷三甲基丙烯酸酯(TMPTMA)和三烯丙基异氰脲酸酯(TAIC)作助交联剂,考察其对发泡聚丙烯(EPP)材料力学性能的影响。结果表明:TAIC与TMPTMA均可有效提高PP的交联度;与TMPTMA相比,TAIC助交联的EPP不仅凝胶率提高了18.67%,还具有更优的硬度、拉伸强度、撕裂强度和压缩永久变形等力学性能。     

Effect of reinforcement type on the mechanical properties of polypropylene composites

The possible reinforcing effects of six different types of filler particles on composites based on the thermoplastic polypropylene have been examined. It is found that significant increases in elastic modulus and tensile strength can be obtained by addition of ≥ 10 percent by volume of glass fibers. Ceramic whiskers, based on alumina and silicon carbide, also lead to increases in modulus but to decreases in strength and ductility. Additional measurements were made with composites prepared from two sizes of spherical glass beads and from carbon spheres. For the glass beads, an increase in modulus was obtained but strength and elongation to fracture decreased. Carbon spheres were ineffective as a reinforcing agent. The possible effects of nonuniform mixing, of size and shape of filler particles, and of surface coatings are discussed.     

Flame retardation of polypropylene: Effect of silane treated antimony compounds

Flame retardation of polypropylene was accomplished by blending with antimony compounds (Sb₂O₃ and SbPO₄) in conjunction with polyvinyl chloride (PVC) or ferric oxide. The compatibility and dispersion of antimony compounds in the polymer matrix was enhanced by using silane coupling agents, viz., vinyltriethoxysilane (A-151) and γ-aminopropyltriethoxysilane (A-1100). Rheological properties of filled polypropylene were studied in the temperature range 180 to 220°C at shear rates of 29.5 to 119.5 sec^?1. An increase in the melt viscosity was found in the filled polypropylene as compared to virgin polymer. Silanation of antimony compounds also influenced the melt rheology of flame retardant polypropylene. Incorporation of 6 phr Sb₂O₃ and 19 phr PVC raised the oxygen index of polypropylene to 22.9 and this sample was found to be self extinguishing in 65 s with a burning rate of 0.06 mm/s as compared to 1.1 mm/s for unfilled polypropylene. Though silanation of antimony compounds slightly reduced the oxygen index of flame retardant polypropylene, yield strain and flexural rigidity of injection molded samples was improved over unsilanated flame retardant polymer.     

Influence of titanium dioxide pigments on the optical properties of polycarbonate and polypropylene for diode laser wavelengths

In laser transmission welding of polymers, additives and colorants could influence the welding result. In this work, polypropylene and polycarbonate probes colored with titanium dioxide (TiO₂) pigments of various concentrations are investigated. The probes are produced using an extrusion process to obtain a homogeneous distribution of colorants. The TiO₂ pigments change the optical properties of the polymers considerably. The measured reflectance increases with increasing pigment load while the transmittance decreases. From the measured data of transmittance, reflectance, and collimated transmittance, the scattering, the absorption coefficient, and the anisotropy factors are calculated. It is shown that the scattering coefficient at 1530 nm (laser) wavelength is smaller than for 968 nm, while the absorption coefficient is negligible for both wavelengths. Scattering coefficient and anisotropy factor are used to simulate the propagation of the laser radiation in the polymers. The influence of the scattering process on the beam propagation is represented by the change of the power density distribution. It is shown that the maximum intensity of the distribution is reduced more than the transmittance with increasing pigment concentration. The effect is higher for 968 than for 1530 nm wavelength making the larger wavelength more favorable for transmission welding. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40073.