Twin‐screw extrusion compounding of polypropylene/organoclay nanocomposites modified by maleated polypropylenes

Polypropylene/organoclay nanocomposites modified with different maleic anhydride grafted polypropylene (PPgMA) compatibilizers were compounded on a twin‐screw extruder. The effectiveness of the feeding sequence and compatibilizer type toward the dispersion of organoclay into PP matrix was critically studied. The composites prepared with side feed appeared to provide better dispersion and modulus improvement over that with hopper feed. The effect of PPgMA compatibilizers, including PB3150, PB3200, PB3000, and E43, with a wide range of maleic anhydride (MA) content and molecular weight was also examined. The structure was investigated with X‐ray diffraction and transmission electron microscopy. The relative complex viscosity curves also revealed a systematic trend with the extent of exfoliation and showed promise for quantifying the hybrid structure of the nanocomposites. Mechanical properties were determined by dynamical mechanical analysis and tensile and impact tests. Maleated polypropylene with low‐melt flow index and moderate MA content enhanced clay dispersion and resulted in significant improvement in tensile modulus of the nanocomposites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 100–112, 2004     

Grafting of maleic anhydride onto polypropylene by reactive extrusion

Maleic anhydride grafting onto polypropylene was conducted in a twin‐screw extruder according to an experimental design in which the maleic anhydride and peroxide concentrations were varied. The modified polypropylene was characterized by FTIR spectroscopy, melt‐flow index measurements, size‐exclusion chromatography, differential scanning calorimetry, and nuclear magnetic resonance. The results showed that only the independent variable peroxide concentration influenced the amount of reacted maleic anhydride, whereas the two variables studied influenced the molecular weight of the grafted polypropylene. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2706–2717, 2002     

Combination of double‐modified clay and polypropylene‐graft‐maleic anhydride for the simultaneously improved thermal and mechanical properties of polypropylene

Double‐modified montmorillonite (MMT) was first prepared by covalent modification of MMT with 3‐aminopropyltriethoxysilane and then intercalation modification by tributyl tetradecyl phosphonium ions. The obtained double‐modified MMT was melt compounded with polypropylene (PP) to obtain nanocomposites. The dispersion of the double‐modified MMT in PP was found to be greatly improved by the addition of PP‐graft‐maleic anhydride (PP‐g‐MA) as a “compatibilizer,” whose anhydride groups can react with the amino groups on the surface of the double‐modified MMT platelets and thus improve the dispersion of MMT in PP. Fourier transform infrared, X‐ray diffraction, transmission electron microscopy, thermogravimetric analysis, scanning electron microscopy, and tensile test were used to characterize the structure of the double‐modified MMT, morphology, and the thermal and mechanical properties of the nanocomposites. The results show that PP‐g‐MA promotes the formation of exfoliated/intercalated morphology and obviously increases the thermal properties, tensile strength, and Young's modulus of the PP/double‐modified MMT nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The role of filler type in the photo‐oxidation behaviour of micro‐ and nano‐filled polypropylene

The rising interest in polymer nanocomposites leads also to an increasing concern for their photo‐oxidation resistance. The main properties and photo‐oxidation behaviour of polypropylene‐based microcomposites and nanocomposites were investigated. The results show that the use of nanosized calcium carbonate may lead to a higher photo‐oxidation rate than that of pristine polypropylene, in a way that is comparable to organo‐modified nanoclays. It is also observed that nanosized calcium carbonate causes higher photodegradation rates than microsized calcium carbonate. The main reasons for the increased photo‐oxidation rates when using organo‐modified nanoclays include the presence of iron ions, the degradation of the organo‐modifier and the formation of acidic sites on nanoclay layers, while in the case of calcium carbonate the main reasons are related to the achieved morphology and structure. The presence of calcium carbonate, especially when nanosized, significantly modifies the distribution of photo‐oxidation products in comparison to clay‐filled nanocomposites. Copyright © 2011 Society of Chemical Industry     

两步法制备聚丙烯/蒙脱土纳米复合材料及其性能研究

采用两步法制备聚丙烯/蒙脱土纳米复合材料PP/MMT,考察了工艺配方和制备条件对材料力学性能的影响。结果表明,两步法制备工艺对PP/MMT的力学性能有明显提高,最佳工艺配方:蒙脱土含量为2%,相容剂含量为15%,最佳制备条件:加工温度200℃,螺杆转速50 r/min。在此条件下制备的PP/MMT复合材料中蒙脱土达到纳米级分散。     

Photo‐oxidation of polystyrene/clay nanocomposites under accelerated UV exposure: Effect on the structure and molecular weight

The present work investigates the effects of photo‐oxidation under accelerated UV conditions on the structure, the molecular weight and the morphology of polystyrene (PS)/organophilic montmorillonite (OMMT) at various clay contents: 2.5, 5, and 7 wt %. Fourier transform infrared spectroscopy, viscosimetry and scanning electron microscopy were used to evaluate the extent of degradation of nanocomposite samples in comparison with neat PS, up to 216 h of exposure. The study has shown that the formation rates of both carbonyl and hydroperoxide groups increase with exposure time, being much higher for PS/OMMT nanocomposites. Moreover, it is also observed that all samples exhibit a large increase in the scission index, however less pronounced for neat PS. These results clearly indicate the formation of low molecular weight products that could arise from chain scission. Further, the photo‐oxidation rate seems to be more affected by the presence of clay, which acts as a catalyst, rather than by the variation of clay contents. Finally, the degraded materials exhibit eroded surface. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

改性剂和增容剂在EPDM/蒙脱土纳米复合材料中的作用

采用熔融插层和不同链长的改性荆改性蒙脱土的方法制备了三元乙丙橡胶(EPDM)／蒙脱土(MMT)纳米复合材料。X-射线衍射(XRD)和透射电镜(TEM)的测试结果表明：采用分子中亚甲基的数量小于16的改性剂改性MMT获得的有机蒙脱土与EPDM复合所得到的复合材料为传统型复合材料。而采用分子中亚甲基的数量大于16的改性剂改性MMT获得的有机蒙脱土与EPDM复合所得到的纳米复合材料为插层型。同时，笔者还探讨了EPDM接枝马来酸酐增容剂时复合材料形态的影响以及获得剥离型纳米复合材料的增容剂中马来酸酐的临界接枝率和增容剂最佳含量。此外，时该纳米复合材料的物理机械性能进行了评价。     

Synthesis and characterization of solid‐phase graft copolymer of polypropylene with styrene and maleic anhydride

Polypropylene (PP) was modified by solid‐phase graft copolymerization with maleic anhydride (MAH) and styrene (St), using benzoyl peroxide as the initiator and xylene as the interfacial agent. Effects of various factors such as monomer concentration, monomer ratio, initiator concentration on grafting percentage, and acid value were investigated. The graft copolymer was characterized by Fourier transform infrared, pyrolysis gas chromatography—mass spectroscopy, and dynamic mechanical analysis, and the intrinsic viscosity of the extractive from the reaction product was investigated. The results showed that the grafting percentage and acid value of the graft copolymer of PP with two monomers (MAH and St) were considerably higher than those of the graft copolymer of PP with MAH alone. The graft segments were shown to be the copolymer of St and MAH with a substantial molecular weight. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2482–2487, 2000     

Chemiluminescence of isotactic polypropylene induced by photo‐oxidative degradation and natural weathering

The analysis of the chemiluminescence (CL) kinetic parameters (induction time, oxidation rate, and activation energy) after the UV irradiation and outdoor exposure of isotactic polypropylene (i‐PP) films have been studied. The initial CL emission intensity increased with increasing photodegradation time of i‐PP films. On photodegradation, the activation energies were found to decrease linearly with time of UV‐irradiation and outdoor exposure. The slopes of these linear dependences were used to indicate the degree of photodegradation of the polymer and also for the characterization of the stabilizing effect of the additive. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4623–4629, 2006     

Analysis of chain‐scission and crosslinking rates in the photo‐oxidation of polystyrene

A study of the chain‐scission and crosslinking rates in polystyrene photodegraded in the laboratory with fluorescent tubes (UVA‐340) was made using GPC molecular weight distributions. The analysis was based on the assumption that scission and crosslinking occur randomly and employed a Monte Carlo procedure to compute the changes in molecular weight distribution for chosen values of scission and crosslinking rates and compared the computed profiles with measurements made on the photodegraded samples. Results were obtained for three different exposures and at various depths within 3.2‐mm‐thick bars. The scission/crosslinking ratio, λ, was between 3 and 8 for all samples measured in this study. The lowest values of λ were found near the exposed surface and the highest near the bar center. Both scission and crosslinking rates were much lower in the interior, presumably the result of oxygen starvation. Some bars were exposed while loaded to 10 MNm⁻² in uniaxial tension. The stress appeared to increase the reaction rates somewhat near the surface and to depress the rates in the interior correspondingly. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3015–3023, 2000     

Effect of pre‐treatments based on UV photocatalysis and photo‐oxidation on toluene biofiltration performance

BACKGROUND: The integration of UV photocatalysis and biofiltration seems to be a promising combination of technologies for the removal of hydrophobic and poorly biodegradable air pollutants. The influence of pre‐treatments based on UV_{254 nm} photocatalysis and photo‐oxidation on the biofiltration of toluene as a target compound was evaluated in a controlled long‐term experimental study using different system configurations: a standalone biofilter, a combined UV photocatalytic reactor‐biofilter, and a combined UV photo‐oxidation reactor (without catalyst)‐biofilter. RESULTS: Under the operational conditions used (residence time of 2.7 s and toluene concentrations 600–1200 mg C m^?3), relatively low removal efficiencies (6–3%) were reached in the photocatalytic reactor and no degradation of toluene was found when the photo‐oxidation reactor was operated without catalyst. A noticeable improvement in the performance of the biofilter combined with a photocatalytic reactor was observed, and the elimination capacity of the biological process increased by more than 12 g C h^?1 m^?3 at the inlet loads studied of 50–100 g C h^?1 m^?3. No positive effect on toluene removal was observed for the combination of UV photoreactor and biofilter. CONCLUSIONS: Biofilter pre‐treatment based on UV_{254 nm} photocatalysis showed promising results for the removal of hydrophobic and recalcitrant air pollutants, providing synergistic improvement in the removal of toluene. Copyright © 2011 Society of Chemical Industry     

Impact modification of polypropylene by ethylene propylene copolymer‐grafted maleic anhydride

Blends of polypropylene (PP) and ethylene propylene rubber (EPR) were studied. The effect of the level of rubber addition and the ethylene content is described. The results show that the viscosity of the PP, rubber content, ethylene content, and grafted EPR by maleic anhydride (MA) are important factors in controlling the blend properties. The miscibility and dynamic properties of the blends were studied by DMTA. Impact and tensile properties were also studied. SEM was used for the investigation of the phase morphology and rubber particle size and particle‐size distribution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1257–1265, 1999     

Polypropylene–intumescent flame‐retardant composites based on meleated polypropylene as a coupling agent

The phosphoric acid‐pentaerythritol‐melamine copolymer, which is composed of three main components of intumescent flame retardant (IFR) and has optimal intumescent degree, was selected as IFR. The influence of meleated polypropylene (PP‐g‐MAH) on the properties and compatibility of IFR polypropylene (PP) composites were studied. The results obtained from mechanical tests, rheological behavior of composites, and scanning electron microscope showed that PP‐g‐MAH was a true coupling agent for IFR/PP blends and did not change the necessary flame retardancy. The cocrystallization between bulk PP and PP segments of PP‐g‐MAH was also proven by WAXD analysis. Flow test showed that the flow behaviors of composites in the melt are those of a pseudoplastic and it is very small for PP‐g‐MAH affecting rheological behavior of the PP/IFR composite. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 257–262, 2002     

Transparent photo‐curable co‐polyacrylate/silica nanocomposites prepared by sol‐gel process

This work prepared the highly transparent photo‐curable co‐polyacrylate/silica nanocomposites by using sol‐gel process. The FTIR and ¹³C NMR analyses indicated that during the sol‐gel process, the hybrid precursors transform into composites containing nanometer‐scale silica particles and crosslinked esters/anhydrides. Transmission electron microscopy (TEM) revealed that the silica particles within the average size of 11.5 nm uniformly distributed in the nanocomposite specimen containing about 10 wt % of Si. The nanocomposite specimens exhibited satisfactory thermal stability that they had 5% weight loss decomposition temperatures higher than 150°C and coefficient of thermal expansion (CTE) less than 35 ppm/°C. Analysis via derivative thermogravimetry (DTG) indicated that the crosslinked esters/anhydrides might influence the thermal stability of nanocomposite samples. The UV‐visible spectroscopy indicated that the nanocomposite resins possess transmittance higher than 80% in visible light region. Permeability test revealed a higher moisture permeation resistance for nanocomposite samples, which indicated that the implantation of nano‐scale silica particles in polymer matrix forms effective barrier to moisture penetration. Adhesion test of nanocomposite samples on glass substrate showed at least twofold improvement of adhesion strength compared with oligomer. This evidenced that the silica and the hydrophilic segments in nanocomposite resins might form interchains hydrogen bonds with the ? OH groups on the surface of glass so the substantial enhancement of adhesion strength could be achieved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

反应挤出马来酸酐接枝聚丙烯的结构与性能

选择最佳的配方和工艺条件,制备了每100g试样总酐基含量为8．1mmol的马来酸酐接枝聚丙烯(PP-g-MAH)产品、通过化学分离和红外光谱分析,发现PP-g-MAH产品的纯度很高,几乎没有游离态的MAH。广角X射线衍射实验发现,PP经过接枝处理后,晶型没有改变,但040晶面明显增大;晶胞在a和c轴上变化不大．在b轴上减小;结品度略有上升：通过分析接枝物的流变性能,发现接枝物与PP一样．仍属于非牛顿型假塑性流体。实验证明,PP-g-MAH产品具有良好的可注塑性。     

Exfoliation targeted toughness enhancement in polypropylene‐blend‐ montmorillonite nanocomposites

BACKGROUND: Both exfoliated and toughened polypropylene‐blend‐montmorillonite (PP/MMT) nanocomposites were prepared by melt extrusion in a twin‐screw extruder. Special attention was paid to the enhancement of clay exfoliation and toughness properties of PP by the introduction of a rubber in the form of compatibilizer toughener: ethylene propylene diene‐based rubber grafted with maleic anhydride (EPDM‐g‐MA). RESULTS: The resultant nanocomposites were characterized using X‐ray diffraction, atomic force microscopy, scanning electron microscopy, thermogravimetric analysis, dynamic mechanical analysis and Izod impact testing methods. It was found that the desired exfoliated nanocomposite structure could be achieved for all compatibilizer to organoclay ratios as well as clay loadings. Moreover, a mechanism involving a decreased size of rubber domains surrounded with nanolayers as well as exfoliation of the nanolayers in the PP matrix was found to be responsible for a dramatic increase in impact resistance of the nanocomposites. CONCLUSION: Improved thermal and dynamic mechanical properties of the resultant nanocomposites promise to open the way for highly toughened super PPs via nanocomposite assemblies even with very low degrees of loading. Copyright © 2008 Society of Chemical Industry     

Effect of montmorillonoite modification and maleic anhydride‐grafted polypropylene on the microstructure and mechanical properties of polypropylene/montmorillonoite nanocomposites

Two types of modified montmorillonite (MMT) were achieved using octadecylamine as the modifying agent by the methods of dry process and wet route. Polypropylene (PP)/MMT nanocomposites were prepared using the melt mixing technique and employing maleic anhydride‐grafted polypropylene (PP‐MA) as the compatibilizer. The modification of montmorillonite was characterized by fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), and scanning electron microscope (SEM). The effect of MMT modification and PP‐MA on the microstructure and properties of PP/MMT nanocomposites was investigated by SEM, differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and polarizing microscopy. The results show that organic montmorillonite modified by wet process (WOMMT) has a large d‐spacing increment; whereas montmorillonite modified by dry process (DOMMT) shows little d‐spacing increment. Furthermore, the mechanical properties of composites incorporating WOMMT are better than that containing DOMMT. As a third component, the addition of PP‐MA benefits the formation of exfoliated structure and the dispersion of MMT in PP matrix, and hence, enhances the physical properties of the nanocomposite. With the presence of PP‐MA, the highly dispersed MMT increases the number of spherulite crystals, enhances the melting enthalpy, improves the thermal stability, and induces the desired tiny crazes more effectively. MMT increases the storage modulus (E′) and glass‐transition temperature (T_g) of PP because of the stiffness of MMT layers, but PP‐MA decreases them owing to its high melt flow index, both of which were in favor of improving the physical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3952–3960, 2013     

Evaluation of cross‐linking after accelerated photo‐ageing of silicone rubber

Silicone formulations based on polydimethylsiloxane (PDMS) were investigated by using a number of analytical techniques. Horizontal attenuated total reflectance Fourier‐transform infrared (HATR‐FTIR) spectroscopy studies have confirmed the stability of these materials towards photo‐oxidation. No significant oxygenated products were detected after 5000 h of accelerated photo‐ageing. However, by using thermoporosimetry, hardness measurements and densitometry, an important vulnerability of these formulations towards the cross‐linking reactions provoked by UV visible radiation was identified. Thermoporosimetry, using the solid‐solid cyclohexane transition as a textural probe, was also used to visualize the profile of cross‐linking inside the materials by calculation of the mesh size distribution in successive slices of 40 µm in thickness. Copyright © 2003 Society of Chemical Industry     

A study on the preparation of polymer/montmorillonite nano‐composite materials by photo‐polymerization

The preparation of polymer/montmorillonite intercalation composite materials was studied by two kinds of photo‐polymerization reaction (photo‐acid generation and photo‐radical generation). Small‐angle X‐ray diffraction was used for the structural characterization of montmorillonite contained in the products. Results indicated that, after chemical modification of montmorillonite, the monomer (methyl methacrylate) and the prepolymer (m‐cresol/HMMM) were able to intercalate into the layers of clay and to polymerize ‘in situ’, thus producing photo‐polymerized composite materials. The advantages and shortcomings of the method of photo‐polymerization for the preparation of these composite materials are discussed. © 2001 Society of Chemical Industry     

Melt rheological properties of polypropylene–maleated polypropylene blends. I. Steady flow by capillary

Melt rheological properties of blends of polypropylene (PP) and PP grafted with maleic anhydride (PP‐g‐MA) are studied using a capillary rheometer. A pseudoplastic flow behavior is observed. The pseudoplasticity of the melt reduces with an increase of PP‐g‐MA content and/or temperature. The PP‐g‐MA component in the blend acts as decreasing melt viscosity, especially in the lower shear rate region, while the addition of PP‐g‐MA to PP does not cause obvious increase of die swell ratio. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1641–1648, 1999