Photooxidation of vulcanized EPDM/montmorillonite nanocomposites

The photooxidation of a vulcanized ethylene-propylene-diene monomer (EPDM)/montmorillonite nanocomposite as well as EPDM/nanocomposite with stabilizers was studied under accelerated UV-light irradiation (λ ≥ 300 nm, 60 °C) for different times. The development of functional groups during oxidation was monitored by infrared spectroscopy. Photodegradation of the neat polymer and composites took place and the increases of absorbance in hydroxyl and carbonyl groups with irradiation times and also the decreases of the EPDM unsaturations were measured. The data indicated that the photooxidation products were not changed in the presence of the nanofiller. However, the presence of MMt was observed to dramatically enhance the rate of photooxidation of EPDM with a shortening of the oxidation induction time, leading to a decrease of the durability of the nanocomposites. On the other hand, it was observed that addition of stabilizers, either Tinuvin P or 2-mercaptobenzimidazole, was efficient in inhibiting the degradative effect of MMt.     

亚临界流体挤出法复合诱导EPDM废胶粉脱硫化及动态交联热塑性弹性体制备

在三元乙丙废胶粉(W-EPDM)与未硫化的三元乙丙橡胶(EPDM)熔融挤出过程中,采用注入亚临界流体和提高双螺杆挤出机螺杆转速的方法,研究了亚临界流体品种(水,乙醇/水混合物,丙醇)、螺杆转速、脱硫促进剂品种(烷基酚多硫化物450、二烯丙基二硫醚)对脱硫共混物(DGTR/EPDM)凝胶含量、门尼粘度、溶胶红外吸收光谱及脱硫共混物共混PP动态交联热塑性弹性体((DEPDM/EPDM)/PP)力学性能的影响,对动态交联热塑性弹性体材料的试样断面形貌也进行了SEM观察。实验结果表明:亚临界乙醇/水混合物(7/3)或亚临界丙醇条件对脱硫反应中S—S键的断裂具有较好的选择性,可引起废胶粉交联网络中S—S交联键断裂反应增加,而主链断裂反应下降,所得脱硫产物制备的动态交联热塑性弹性体材料中未熔融的凝胶颗粒尺寸较小,材料的力学性能明显增大;脱硫促进剂烷基酚多硫化物450具明显的促进脱硫反应的作用。在亚临界正丙醇的最佳挤出反应条件下(220℃,600rpm,促进剂450),所得脱硫共混物(DEPDM/EPDM)制备的动态交联热塑性弹性体材料(DEPDM/EPDM)/PP的拉伸强度和断裂伸长率分别达到17.1MPa和443%,其力学性能和断面形貌结构明显优于以传统罐式脱硫法所得的相应材料。     

Aging of ethylene-propylene-diene monomer (EPDM) in artificial weathering environment

Ethylene-propylene-diene monomer (EPDM) containing ENB as diene was exposed to artificial weathering environment for different periods of time. The changes of appearance, morphology, mechanical properties and chemical structures were monitored by spectrophotometer, glossmeter, microscope, computer-controlled tensile testing, hardness measurements and Fourier Transform Infrared (FTIR) spectroscopy. Crosslink density of EPDM specimens was measured by the solvent swell method. The results showed that the surface of EPDM became redder, yellower and lighter in the first stage of aging and then remained almost unchanged. The specular gloss reached a maximum when the sample was exposed for 18 days and then decreased. The aging process proceeded predominantly via crosslinking. The tensile strength increased with increase in crosslink density up to an optimum value and thereafter decreased with further increase in crosslink density. FTIR spectra confirmed the formation of carbonyl groups in an artificial weathering environment.     

Aging behavior and mechanism of ethylene-propylene-diene monomer (EPDM) rubber in fluorescent UV/condensation weathering environment

Ethylene-propylene-diene monomer (EPDM) rubber was exposed to an artificial weathering environment produced by fluorescent UV/condensation weathering device for different time periods. The surface chemical changes were detected by X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy. The plausible aging mechanism of EPDM was proposed. The surface energy was calculated through contact angles of water and formamide measured by optical contact angle measuring device. The thermal stability was evaluated by thermo-gravimetric analysis (TGA).The results showed that oxygenated species such as C-O-C, CO and O-CO groups were formed in fluorescent UV/condensation weathering environment. EPDM aging occurred from EPDM surface and propagated to EPDM inner body. The surface energy of EPDM increased to a maximum at 36 days of aging and then decreased slowly. Fluorescent UV/condensation weathering environment does not affect the thermal stability of EPDM predominantly.     

EPDM受热氧化与动态流变行为

采用动态流变学方法研究了三元乙丙橡胶(EPDM)高温氧化与动态粘弹响应之间的关系.在熔体状态下,EPDM的动态粘弹行为随温度升高而改变,呈现出非均相结构的流变响应特征;加入复合抗氧剂后,EPDM在一定的时间范围内,呈现均相体系的流变响应特征.这些结果表明,流变响应特征的改变与受热导致EPDM熔体氧化进而引起结构的改变密切相关.低频区域粘弹函数对EPDM结构变化具有敏感响应,2 0 0～2 2 0℃可明显观察到受热氧化导致EPDM结构的生成.     

Surface degradation of ethylene-propylene-diene monomer (EPDM) containing 5-ethylidene-2-norbornene (ENB) as diene in artificial weathering environment

Ethylene-propylene-diene monomer (EPDM) containing 5-ethylidene-2-norbornene (ENB) as diene was exposed to an artificial weathering environment produced by a xenon lamp light exposure and weathering equipment for different time periods. The surface chemical changes were detected by Specular Reflection Fourier Transform Infrared (SR-FTIR) spectroscopy, Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The change in surface color, contact angle and morphology was monitored by spectrophotometer, optical contact angle measuring device and Scanning Electron Microscope (SEM). Furthermore, surface energy was calculated through contact angles of water and formamide. The results showed that hydroxyl, carbonyl and ester groups were formed during exposure to this artificial weathering environment. EPDM surface became redder, yellower and lighter in the first stage of aging and then remained almost unchanged. The contact angles of water and formamide decreased to a minimum and then increased slowly. The surface degradation is a zero order reaction. In addition, the plausible degradation mechanism was proposed.     

Investigation into morphology, microstructure and properties of SBR/EPDM/ORGANO montmorillonite nanocomposites

Rubber compounds based on styrene-butadiene rubber/ethylene propylene diene monomer blends of different compositions (60/40, 70/30, 80/20, 90/10, 100/0) reinforced with 1 wt%, 3 wt%, 5 wt% and 7 wt% organoclay (Cloisite 20A) were prepared on a two roll mill via a vulcanization process and characterized by several techniques. Results of X-ray diffraction showed expansion of the inter-gallery distance, and transmission electron microscopy (TEM) micrographs confirmed that the prepared nanocomposite samples have intercalated and partially exfoliated structures. Cure characteristics showed that, organoclay not only accelerates the vulcanization reaction, but also gives rise to a marked increase of the torque, indicating crosslink density of the prepared compounds increases at the presence of organoclay. Mechanical properties of samples received markedly increase by clay loading due to the good interaction established between nanoclay particles and polymer matrix as it was evidenced by SEM photomicrographs. At the same time, rheological properties showed that addition of nanoclay could improve storage modulus as well as complex viscosity of SBR/EPDM samples. The results of ozone test revealed that the ozone resistance of samples significantly increases as nanoclay or EPDM content increases.     

Effect of polyfunctional monomers on properties of radiation crosslinked EPDM/waste tire dust blend

In this study, waste tire dust is recycled as filler and blended with ethylene-propylene diene monomer (EPDM) rubber. Three different polyfuntional monomers (PFMs) are incorporated into the standard formulation and irradiated under electron beam at different doses up to maximum of 100 kGy. The combined effects of PFMs and absorbed dose on the physical properties of EPDM/WTD blend are measured and compared with sulfur crosslinked formulation. Thermogravimetric analysis showed that radiation developed better crosslinked network with higher thermal stability than sulfur crosslinked structure. The physical properties of radiation crosslinked blend are similar to the sulfur crosslinked blend. The absence of toxic chemicals/additives in radiation crosslinked blends made them an ideal candidate for many applications such as roof sealing sheets, water retention pond, playground mat, sealing profile for windows etc.     

The thermal degradation behaviour of polydimethylsiloxane/montmorillonite nanocomposites

A series of novel polydimethylsiloxane/montmorillonite (PDMS/MMT) nanocomposites was prepared. The thermal degradation behaviour of these nanocomposites was studied by means of Thermal Volatilization Analysis (TVA) and Thermogravimetric Analysis (TGA). The major degradation products were identified as cyclic oligomeric siloxanes from D₃ to D_7, and higher oligomeric siloxane residues. Other minor degradation products include methane, bis-pentamethylcyclotrisiloxane, propene, propanal, benzene and dimethylsilanone. The results demonstrate that the nanoclay significantly alters the degradation behaviour of the PDMS network, modifying the profile of the thermal degradation and reducing the overall rate of volatiles evolution. The results also indicate that the nanoclay promotes the formation of dimethylsilanone and benzene by inducing low levels of radical chain scission.     

Effect of ZnO and organo-modified montmorillonite on thermal degradation of poly(methyl methacrylate) nanocomposites

Since a few years ago, a topic of interest consists in developing composites filled with nanofillers to improve thermal degradation and flammability property of poly(methyl methacrylate) (PMMA). In the present work, the effects of ZnO nanoparticles and organo-modified montmorillonite (OMMT) on the thermal degradation of PMMA were investigated by thermogravimetric analysis (TGA). PMMA-ZnO and PMMA-OMMT nanocomposites were prepared by melt blending with different (2, 5, and 10 wt%) loadings. SEM and TEM analyses of nanocomposites were performed in order to investigate the dispersion of nanofillers in the matrix. According to TGA results, the addition of ZnO nanoparticles does not affect the thermal degradation of PMMA under an inert atmosphere. However, in an oxidative atmosphere, two contrary effects were observed, a catalytic effect at lower concentration of ZnO in the PMMA matrix and a stabilizing effect when the ZnO concentration is higher (10 wt%). In contrast, the presence of OMMT stabilizes the thermal degradation of PMMA whatever be the atmosphere. Differential thermal analysis (DTA) curves showed surprising results, because a dramatic change of exothermic reaction of the PMMA degradation process to an endothermic reaction was observed only in the case of OMMT. During the degradation of PMMA-ZnO nanocomposites, pyrolysis-gas chromatography coupled to mass spectrometer (Py-GC/MS) showed an increase in the formation of methanol and methacrylic acid while a decrease in the formation of propanoic acid methyl ester occurred. In the case of PMMA-OMMT systems, a very significant reduction in the quantity of all these degradation products of PMMA was observed with increasing OMMT concentration. It is also noted that during PMMA-OMMT degradation less energy was released as the decomposition is an endothermic reaction and the material was cooled.     

Mechanical properties of polyamide-12 layered silicate nanocomposites and their relations with structure

The mechanical properties of polyamide-12/Cloisite 30B (PA12/C30B) nanocomposites prepared by melt compounding were studied as a function of clay volume fraction φ under various processing conditions. All measured mechanical characteristics, Young's modulus, yield stress, strain at break and stress at break, exhibit a transition at φ_p1%, identified with a percolation threshold. Also, the linear and non-linear mechanical properties appeared to depend on the degree of exfoliation of the structure, which can be tuned by the processing conditions. The three-phase Ji's theoretical model was used to predict Young's modulus as a function of clay concentration, focusing on the influence of the degree of exfoliation. Experimental yield stress data were fitted to Pukanszky's model and discussed in terms of PA12/C30B interfacial adhesion.     

Biodegradable poly(lactic acid)/chitosan-modified montmorillonite nanocomposites: Preparation and characterization

In this study, the biodegradable poly(lactic acid) (PLA)/montmorillonite (MMT) nanocomposites were successfully prepared by the solution mixing process of PLA polymer with organically-modified montmorillonite (m-MMT), which was first treated by n-hexadecyl trimethyl-ammonium bromide (CTAB) cations and then modified by biocompatible/biodegradable chitosan to improve the chemical similarity between the PLA and m-MMT. Both X-ray diffraction data and transmission electron microscopy images of PLA/m-MMT nanocomposites indicate that most of the swellable silicate layers were disorderedly intercalated into the PLA matrix. Mechanical properties and thermal stability of the PLA/m-MMT nanocomposites performed by dynamic mechanical analysis and thermogravimetric analysis have significant improvements in the storage modulus and 50% loss in temperature when compared to that of neat PLA matrix. The degradation rates of PLA/m-MMT nanocomposites are also discussed in this study.     

Thermal properties of nanocomposites based on polyethylene and n-heptaquinolinum modified montmorillonite

The aim of the research was obtaining and application of smectic clay modifying agent. The organophilic clay is used as nanofiller in polymer nanocomposites [1]. A microwave-assisted reaction led to obtaining N-heptaquinolinum, which is amphiphilic compound, containing both hydrophobic (alkyl and aromatic) and hydrophilic sections in its structure [2]. N-heptaquinolinum was used as a montmorillonite clay modifying agent. Modification was carried out in formulated way [3, 4]. Modification efficiency was determined by X-ray diffraction (XRD) analysis and elementary analysis. Organophilic clay (Ch7) was introduced, using the extrusion method, into polyethylene matrix in different mass relations (1.5, 3 and 5?%) [3]. The structure of obtained materials was studied by means of XRD and SEM. To evaluate potential applications thermal properties of received nanocomposites were tested with thermogravimetric analysis and differential scanning calorimetry. The thermal stability of PE/clay composites can be improved in the case of loading 1.5 and 5?mass%.     

Effect of montmorillonite on structure and properties of nanocomposite with PA6/PS/elastomer matrix

Polyamide nanocomposites with fair balance of mechanical properties were recently obtained by addition of finely dispersed clay-compatibilized rubber or rigid PS phase. This work deals with combination of both components, which recently led also to enhanced mechanical behaviour in an analogous reactively compatibilized ternary system.Application of clay to PA6/PS/EPR matrix leads to a decrease in particle size analogously to corresponding binary blends, but the effect of clay on toughness is predominantly contradictory, i.e., a decrease with increasing clay content was found. Also the toughening effect of formed core-shell (elastomer/clay) particles is lower in comparison with binary PA6/EPR. At the same time, in contrast to the PA/PS system, the presence of core-shell particles formed by PS/C15 preblending leads to fair mechanical behaviour including enhanced toughness. This documents a complex affecting of the system behaviour by clay and the expected synergistic cooperation of numerous clay-induced changes in both component parameters and structure. The obtained results indicate that a proper combination of rigid and elastomeric inclusions can lead to nanocomposites with balanced and enhanced mechanical behaviour.     

Effect of modified carbon nanotube on physical properties of thermotropic liquid crystal polyester nanocomposites

Polymer nanocomposites based on a very small quantity of carbon nanotube (CNT) and thermotropic liquid crystal polymer (TLCP) were prepared by simple melt blending using a twin-screw extruder. Morphological observations revealed that modified CNT was uniformly dispersed in the TLCP matrix and increased interfacial adhesion between the nanotubes and the polymer matrix. The enhancement of the storage and loss moduli of the TLCP nanocomposites with the introduction of CNT was more pronounced at low frequency region, and non-terminal behavior observed in the TLCP nanocomposites resulted from the nanotube-nanotube and polymer-nanotubes interactions. There is significant dependence of the mechanical, rheological, and thermal properties of the TLCP nanocomposites on the uniform dispersion of CNT and the interfacial adhesion between CNT and TLCP matrix, and their synergistic effect was more effective at low CNT content than at high CNT content. The key to improve the overall properties of the TLCP nanocomposites depends on the optimization of the unique geometry and dispersion state of CNT and the interfacial interactions in the TLCP nanocomposites during melt processing. This study demonstrate that a very small quantity of CNT substantially improved thermal stability and mechanical properties of the TLCP nanocomposites, providing a design guide of CNT-filled TLCP composites with as great potential for industrial use.     

Effect of new melamine-terephthaldehyde resin modified graphene oxide on thermal and mechanical properties of PVC

In this study a new melamine-terephthaldehyde resin modified graphene oxide was synthesized and used as a reinforcement of poly(vinyl chloride) (PVC). Characterization, morphology, thermal and mechanical properties of the nanocomposites were examined by means of attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray diffraction, field emission-scanning electron microscopy, thermogravimetric analysis, differential scanning calorimeter and tensile properties. The first hydrochloric acid releasing data of poly(vinyl chloride) was removed by incorporation of the modified graphene oxide as compare to the neat polymer. The temperatures at 2 wt% losses, main decomposition temperatures, maximum decomposition temperatures, also shift to higher temperature in the corresponding nanocomposites as compared to the neat PVC. The tensile strength and elongation at break of the nanocomposite films was increased as compared to the neat PVC. The interesting results in crystallinity of PVC were observed with adding 5 wt% of the modified graphene oxide.     

Gallery structure and exfoliation of organophilized montmorillonite: effect on composite properties

Wyoming montmorillonite was organophilized to different extents with N-cetylpyridinium chloride and its gallery structure was studied by WAXS. PP nanocomposites were prepared using this silicate and their structure, as well as tensile properties were determined as a function of composition. Two peaks were observed in the WAXS patterns of some of the treated silicates, one of which disappeared during processing. The orientation of the organic compound in the galleries depends on its size and amount, as well as on the ion density of the filler. Multiple peaks appearing in the WAXS pattern of organophilized silicate may arise from interference, but they may also indicate the presence of several populations of layer distances. Water is absorbed between the galleries of partially organophilized silicates leading to the separation of the layers resulting in the appearance of new scattering peaks. Exfoliation occurs only above a critical gallery distance, which corresponds to the thickness of two aliphatic chains. Although exfoliation of the silicate is determined by its organophilization and gallery structure, composite properties are dominated by interfacial interaction.     

Biodegradable polyester nanocomposites: The effect of structure on mechanical and degradation behavior

The study describes the effect of the layered silicate content and its dispersion on the mechanical behavior of poly(ε-caprolactone) (PCL) nanocomposites and their corresponding changes during the degradation in a phosphate buffer at 37 °C. Two nanocomposite systems were compared: intercalated and exfoliated nanocomposites. They were prepared by melt-compounding of a high-molecular-weight PCL with in situ polymerized silicate masterbatches or an organophilized montmorillonite. It has been shown that Young modulus increases with the increasing silicate content and at the same time, the highest increase in the modulus is observed for the exfoliated system. The stiffness enhancement is predominantly caused by the dispersed inorganic phase but also supported by the contribution of the low-molecular-weight PCL fraction, which comes from the masterbatch, to the total degree of crystallinity. In contrast, the increase in the yield stress is driven mainly by the present low-molecular-weight PCL fraction with higher crystallinity. The degradation behavior reflects both the presence of the layered silicate as well as the low-molecular-weight PCL fraction. Their presence accelerates the degradation in the phosphate buffer at 37 °C.     

异氰酸酯对EPDM橡胶粘接的影响

异氰酸酯对EPDM橡胶粘接的影响;EPDM橡胶;异氰酸酯;粘接