Effect of Individualized Cellulose Fibrils on Properties of Poly(Methyl Methacrylate) Composites

Cellulose fibrils were manufactured from flax fibers using chemical treatments followed by cryo-crushing and ultrasonication techniques. The fibrils, consisting mainly of cellulose free from lignin, pectin and hemicellulose, were exploited as a biofiller in preparing poly(methyl methacrylate) (PMMA) matrix composites. The effects of incorporating cellulose fibrils on the physical and mechanical properties of the polymer matrix were investigated. In particular, the influence of the fibrils on the thermal stability and degradation of the composites was studied by means of thermogravimetric analysis carried out in both inert and oxidative atmospheres. The runs performed under air flow revealed the efficiency of the cellulose fibrils in delaying the polymer decomposition during thermal oxidation. The weight loss was slowed down in the composites of all compositions and the temperature of degradation increased with increasing the amount of the fibrils. The combustion properties of the fibril-based composites were evaluated by means of pyrolysis combustion flow calorimetry. The addition of cellulose fibrils into the PMMA matrix resulted in a noticeable decrease of the primary combustion parameters.     

Thermal Stability and Degradation Kinetics of Poly(Methyl Methacrylate)/Sepiolite Nanocomposites by Direct Melt Compounding

Poly(methyl methacrylate) (PMMA) nanocomposites based on sepiolite modified with trimethyl hydrogenated tallow amine by an adsorption process were prepared by melt compounding using a corotating twin screw extruder. The morphology and dispersion of sepiolite in the PMMA were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability and the activation energies were investigated by thermogravimetric analysis/differential thermogravimetric (TGA/DTG). The XRD and TEM results show that the sepiolite was dispersed homogeneously in the PMMA matrix at a nanometer scale. The TGA analysis revealed that the addition of sepiolite improved the thermal stability of PMMA. The apparent activation energies were calculated by the method of Flynn–Wall–Ozawa in nitrogen at four different heating rates, showing that sepiolite increased the apparent activation energies by about 20 kJ/mol within the degree of conversion (α) of 0.35–0.9, as compared with the reference PMMA sample.     

Effect of Molecular Architecture on Physical Properties of Tree-Shaped and Star-Shaped Poly(Methyl Methacrylate)-Based Copolymers

The synthesis of star-like A(B)_n copolymers based on the hydrophilic poly(ethylene glycol) monomethyl ether (m-PEG, block A) and the hydrophobic poly(methyl methacrylate) (PMMA, blocks B) is reported. We obtained copolymers made of one m-PEG chain and 2 or 4 PMMA blocks using a combined “arm first”—“core first” approach. Such structures were called tree-shaped copolymers where the m-PEG was considered as the trunk and PMMA arms as the branches. Star-like copolymers (B)_nA-A(B)_n built by two tree-shaped fragments with a poly(propylene oxide) (PPO) as the central junction, were also synthesized according to a previously reported procedure. The latter were called star-shaped structures and the synthesis was performed to obtain architectures different from the tree-shaped one but characterized by a similar length of the PMMA arms. Microstructural analysis was carried out through ¹H-NMR and GPC, and the thermal and transport properties (sorption and diffusion) to liquid water were investigated and correlated to the molecular architecture of the two classes of copolymers.     

聚甲基丙烯酸甲酯(PMMA)微流控芯片DNA分析系统的研制

生物分析是微流控芯片分析最具进一步发展及商品化前景的分支领域之一。报道了基于聚甲基丙烯酸甲酯(PMMA)微流控芯片DNA分析系统的研制。采用简易热压法自制的PMMA芯片,以小型光纤式激光诱导荧光为检测器,以四触点可切换1 800 V高压电源为电驱动系统,以2%羟乙基纤维素(HEC)为筛分介质,通过用于DNA分析的TO-PRO-3荧光染料和激光诱导荧光检测器670 nm截止滤光片的选择,构建了微流控芯片DNA分析系统。芯片凝胶电泳分离φX174-HaeⅢRF DNA片段, 以603 bp片段计算理论塔板数n为1.14×106·m-1, 271/281 bp的分离度R为1.2。建立的PMMA微流控芯片DNA分析系统具有制作和运行成本低,芯片可重复使用,分析重现性好等特点。该研究可用于制作微型化便携式DNA分析仪,应用于临床诊断、疾病筛查等领域。     

Parametric Studies on the Grafting of Poly(Methyl Methacrylate) onto Organophilic Montmorillonite Using Silylated Clay Platelets

Poly(methyl methacrylate) (PMMA)/organophilic montmorillonite (Cloisite 30B) nanocomposites were synthesized by the chemical grafting of PMMA onto Cloisite 30B via solution polymerization of methyl methacrylate (MMA) with vinyl-modified organoclay. The effects of different parameters such as clay weight percent (CWP), solvent per monomer volume ratio, and dispersion time on the properties of the PMMA grafted Cloisite 30B were investigated using the Taguchi experimental design method. This method gives a much-reduced variance for the experiments with optimum setting of control parameters and provides a set of minimum experiments compared to the conventional methods. Qualitative evidence for the chemical grafting of the PMMA onto Cloisite 30B was confirmed by Fourier transform infrared spectroscopy (FT-IR). X-ray diffraction (XRD) was used to investigate interlayer changes of the clay in the grafted nanoplatelets. The exfoliated/intercalated morphology of the nanocomposites was confirmed by XRD. Furthermore, thermal properties were measured by thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). Statistical analysis of results revealed that clay weight percent and solvent per monomer ratio had significant effects on the properties of final products. The percent of grafted PMMA and storage modulus of PMMA/30B nanocomposites decreased with increasing clay content due to better dispersion of the clay at lower loadings. On the other hand, because of a tendency to formation of homopolymer and oligomers at higher solvent loadings; the percent of grafted PMMA, storage modulus and glass transition temperature of PMMA/30B nanocomposites decreased with an increase in solvent per monomer volume ratio. However, the obtained PMMA/30B nanocomposites at the optimum conditions, was exhibited a higher glass transition temperature, higher storage modulus and better thermal stability than the pure PMMA.     

对－氯苯乙烯和丙烯酸甲酯梯度共聚物的微观结构表征

对由原子转移自由基聚合(ATRP)方法得到的具有“活性”聚合特征的对－氯苯乙烯(S)和丙烯酸甲酯(M)梯度共聚物结构进行了表征．通过¹H、¹³C 核磁共振(NMR)方法和对羰基¹³C峰峰面积的拟合积分研究了该共聚物的单体以及以M为中心的三元组序列结构的组成含量随转化率的变化．研究结果表明：共聚物链中S和M单体含量随着转化率的增加分别表现出减小和增大的变化趋势;三元组序列结构的含量变化中,SMS和MMM分别呈现出单调下降和上升的变化,而MM/MMS则随着转化率的增加达到一个最大值,然后呈现下降趋势．本文还尝试运用了以M为中心的五元组序列结构对羰基¹³C峰峰面积进行更精确的拟合积分,其拟合峰面积的计算结果显示了与上述三元组序列结果相同的变化规律．     

Mechanical,Thermal, and Rheological Properties of EPDM-graft-methyl Methacrylate and Styrene (EPDM-g-MS)/Methyl Methacrylate-Styrene Copolymer (MS Resin) Blends

EPDM-graft-methyl methacrylate and styrene (EPDM-g-MS) were synthesized by solution graft copolymerization of methyl methacrylate (MMA) and styrene (St) onto ethylene-propylene-diene terpolymer (EPDM). EPDM-g-MS/MS resin blends (MES) tht were prepared by melt blending EPDM-g-MS and methyl methacrylate-styrene copolymer (MS resin). The mechanical properties, compatibility, thermal stabilities and rheological properties of MES were studied by the pendulum impact tester and the tension tester, differential scanning calorimetric (DSC), thermogravimetry analysis (TGA), and the capillary rheometry, respectively. The results showed that EPDM-g-MS had an excellent toughening effect on MS resin; the notched Izod impact strength of MES reached 20.7 kJ/m² when EPDM content in MES was 25 wt%, about 14 times that of MS resin. EPDM-g-MS and MS resin were partially compatible, and the compatibility increased with an increasing MMA/St ratio of EPDM-g-MS. MES had excellent heat-resistance, which increased as the EPDM content in MES and MMA/St ratio of EPDM-g-MS rose. MES melt flow confirmed pseudoplastic flow characteristics. The apparent viscosity (η _a ) of MES decreased with an increasing shearing rate (γ) and temperature, but increased with an increasing EPDM content in MES and MMA/St ratio of EPDM-g-MS. The flow activation energy of MES was lower than that of MS resin.     

Thermal Behavior of Polypropylene-g-glycidyl Methacrylate Prepared by Melt Grafting

The thermal behaviors of glycidyl methacrylate (GMA)-grafted polypropylene (PP) (PP-g-GMA) with two different grafting degrees, namely, GPP1 and GPP2, were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide-angle X-ray diffraction (WAXD), dynamic mechanical analysis (DMA), and thermogravimetrical analysis (TGA). DSC results suggested that the GMA grafted PP exhibited higher crystallization temperature T_c, higher melting temperature T_m, and higher crystallinity compared with the neat PP. The isothermal crystallization kinetics was analyzed with the Avrami equation and the total crystallization activation energy was calculated. It was concluded that the crystallization processes of PP and the grafted PP were controlled by nucleation and the values of the crystallization activation energy of PP and the grafted PP were almost identical. POM results suggested that the GMA grafted PP exhibited smaller spherulites size compared with the neat PP. WAXD patterns indicated that the neat PP encouraged the formation of γ phase, compared with the grafted PP, during the crystallization process. DMA results showed that melt grafting did not induce a clear effect on the γ-transition and β-transition of the amorphous phase but resulted in a decrease in mobility of the PP chains in the crystals. TGA curves suggested that the melt grafting slightly improved the thermal stability of PP.     

Mechanical and Thermal Properties of Poly(Tetrahydrofurfuryl Methacrylate) Nano-Composites

To obviate the brittleness and improve the mechanical properties of poly(tetrahydrofurfuryl methacrylate) (PTHFMA), clay mineral nano-composites of PTHFMA with two different montmorillonites (MMT), Cloisite® 20A and Cloisite® 30B, were prepared. The mechanical properties were investigated by dynamic mechanical analysis (DMA) and nanoindentation. The thermal properties of the nano-composites were studied using thermogravimetric analysis (TGA). According to the DMA results, tanδ was increased by addition of the clay, leading to the improvement in the mechanical properties which was also confirmed by the nanoindentation results. TGA thermograms showed better thermal stability for the nano-composites compared to that of the homopolymer. Considering all results, the clay mineral polymer nano-composites (CPN) with Cloisite® 20A exhibited better properties compared to those with Cloisite® 30B. Transmission electron microscopy (TEM) micrographs, and X-ray diffraction (XRD) patterns validated intercalation-exfoliation of the clay mineral layers for the Cloisite 20A and intercalation of the Cloisite 30B in the polymer matrix.     

高压下三种脂肪酸甲酯液相导热系数的实验研究

生物柴油是新型环境友好型替代能源,其主要成分为碳数分布在C6～C24的长链脂肪酸酯.利用瞬态单丝法导热系数测量系统在272～352K温度范围内、0.1～15 MPa压力范围内对三种生物柴油组成成分壬酸甲酯、庚酸甲酯和己酸甲酯的液相导热系数进行了实验测量,并将导热系数拟合成关于温度和压力的方程,壬酸甲酯、庚酸甲酯和己酸甲...     

Bonding at Compatible and Incompatible Amorphous Interfaces of Polystyrene and Poly(Methyl Methacrylate) Below the Glass Transition Temperature

Abstract

Films of high‐molecular‐weight amorphous polystyrene (PS, M _w = 225 kg/mol, M _w/M _n = 3, T _g‐bulk = 97°C, where T _g‐bulk is the glass transition temperature of the bulk sample) and poly(methyl methacrylate) (PMMA, M _w = 87 kg/mol, M _w/M _n = 2, T _g‐bulk = 109°C) were brought into contact in a lap‐shear joint geometry at a constant healing temperature T _h, between 44°C and 114°C, for 1 or 24 hr and submitted to tensile loading on an Instron tester at ambient temperature. The development of the lap‐shear strength σ at an incompatible PS–PMMA interface has been followed in regard to those at compatible PS–PS and PMMA–PMMA interfaces. The values of strength for the incompatible PS–PMMA and compatible PMMA–PMMA interfaces were found to be close, both being smaller by a factor of 2 to 3 than the values of σ for the PS–PS interface developed after healing at the same conditions. This observation suggests that the development of the interfacial structure at the PS–PMMA interface is controlled by the slow component, i.e., PMMA. Bonding at the three interfaces investigated was mechanically detected after healing for 24 hr at T _h = 44°C, i.e., well below T _g‐bulks of PS and PMMA, with the observation of very close values of the lap‐shear strength for the three interfaces considered, 0.11–0.13 MPa. This result indicates that the incompatibility between the chain segments of PS and PMMA plays a negligible negative role in the interfacial bonding well below T _g‐bulk.     

The Mechanical Properties,Compatibility, and Thermal Stabilities of POE-Graft-Methyl Methacrylate and Acrylonitrile(POE-g-MAN)/ Styrene-Acrylonitrile Copolymer (SAN Resin) Blends

POE-graft-methyl methacrylate and acrylonitrile (POE-g-MAN) was prepared by graft copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) onto polyethylene-octene copolymers (POE) with suspension polymerization. POE-g-MAN/SAN resin blends (AOMS) were prepared by blending POE-g-MAN with styrene-acrylonitrile copolymer (SAN resin). The mechanical properties, compatibility, and thermal stabilities of AOMS were studied. The notched impact strength of the blends reached 54.0 kJ/m² when the AN/(MMA + AN) ratio (f_AN) of POE-g-MAN, benzoyl peroxide dosage, and POE content in AOMS were 15 wt%, 1.0 wt%, and 25 wt%, respectively. Transmission electron microscopy analysis showed that the highest toughness occurred when the size of POE-g-MAN particles and the surface-to-surface inter-particle distance were proper. Scanning electron microscopy analysis indicated that the AOMS fracture surface had plastic flow visible, which looked like a fibril morphology when the AN/(MMA + AN) ratio (f_AN) of POE-g-MAN was 15 wt%. The toughening mechanism of AOMS was shear yielding of the matrix, which endowed AOMS with remarkable toughness. Dynamic mechanical thermal analysis showed that the compatibility of the POE phase and SAN phase improved after graft copolymerization of MMA and AN onto POE. When the grafting chain polarity was appropriate, the miscibility between POE-g-MAN and SAN resin was the best. Thermogravimetry analysis showed that thermal stability of AOMS increased with increasing AN units in POE-g-MAN.     

Swelling Parameters and Mechanical Properties of Functional Fibers Based on Butyl Methacrylate-Hydroxyethyl Methacrylate Copolymer

Butyl methacrylate-hydroxyethyl methacrylate (BMA-HEMA) copolymers were synthesized by the method of suspension polymerization. The copolymer fibers were prepared for absorbing liquid organic matter by gelation-spinning in a twin screw extrusion machine. The swelling parameters and mechanical properties were investigated, and the morphology was observed by scanning electron microscope (SEM). The results show that the degree of equilibrium swelling for the fibers increased with increasing the mass fraction of HEMA in the monomer feed when toluene, trichloroethylene, or chloroform were selected as organic absorbates. All of the interaction parameters, χ ₁, for the fibers and organic liquids were less than 0.5, with the order of the interaction parameters χ ₁ being as follows: toluene > trichloroethylene > chloroform. Average molecular weights between crosslink points, M _c, and effective crosslink density, V _e, were dependent on the selected organic liquids; for the different organic liquids, M _c and V _e were different. The breaking tenacity, initial modulus, and yield stress of the fibers increased with an increase in the mass fraction of HEMA. However, elongation at break and elongation at yield decreased with increasing the mass fraction of HEMA; in particular, for the mass fraction of HEMA equal to 15 wt%, the fiber did not yield, and underwent a brittle fracture.     

Kinetics Study on Thermal Decomposition of Polyepoxyphenylsilsesquioxane/Epoxy Resin Systems

The thermal decomposition kinetics of epoxy resin (EP) containing polyepoxyphenylsilsesquioxane (PEPSQ) was studied by thermogravimetric analysis (TGA) in a nitrogen atmosphere. Kissinger and Flynn–Wall–Ozawa methods were both used to analyze the thermal decomposition process under nonisothermal conditions. The results showed that a slight increase of activation energy was observed in the presence of PEPSQ, which indicated that the addition of PEPSQ retarded the thermal decomposition of EP. The Flynn–Wall–Ozawa method further revealed that PEPSQ significantly increased the activation energy of the whole EP thermal decomposition, especially in the final stage of the thermal decomposition process, which is attributed to the PEPSQ stabilizing the char layer and improving the flame retardancy of EP.     

Thermal Stability and Decomposition Kinetics of Poly(Methacryloyloxyethyl Trimethyl Ammonium Chloride-Co-Acrylamide)

Abstract

Poly(methacryloyloxyethyl trimethyl ammonium chloride-co-acrylamide) (P(DMC-AM)), is widely used for various applications under a wide range of conditions. In this work the thermal stabilities and decomposition kinetics of P(DMC-AM) with various intrinsic viscosities, synthesized in our laboratory, were studied by thermogravimetric analysis (TGA) at various heating rates, 5, 10, 20 and 40?K/min, and differential scanning calorimetry (DSC) at 10?K/min, all under a dynamic nitrogen atmosphere. The kinetic parameters were calculated using a model fitting method (Coats–Redfern, CR) and two model–free methods (Kissinger–Akahira–Sunose, KAS and Flynn–Wall-Ozawa, FWO). The result showed that all samples exhibited three steps of mass loss, one for the elimination of the adsorbed water and organic solvents and two for the thermal decomposition of P(DMC-AM). The first decomposition stage for the three samples was in the range of 5% to 45%, the second decomposition stage in the range of 65% to 95% and with 55% conversion separating the first and second decomposition stages. The E values increased with the increasing intrinsic viscosity of the samples. Hence, P(DMC-AM) had good thermal stability and the higher the molecular weight, the better the thermal stability was.     

一种有机电致发光共聚物的制备和性能

采用Suzuki方法合成了9，9-二辛基芴与萘并硒二唑的两种无规共聚物并研究了其紫外光谱、光致发光和电致发光性能。两种聚合物的电致发光波长为650～666nm，均为发饱和红光的LED材料，其电致发光外量子效率最高达到了1．05％。随着共聚物中萘并硒二唑含量的增加，共聚物的光致发光和电致发光的发射波长均有少量红移。证明了根据共轭高聚物链内能量转移原理，在聚芴链中引入不同含量的窄带隙杂环单元可实现对聚芴发光颜色的调节。     

Electronic and Optical Properties of Some Polysulfone-Polydimethylsiloxane Copolymers in Thin Films

Polysulfone (PSF)-polydimethylsiloxane (PDMS) block copolymers (PSF-b-PDMS) with various compositions were prepared by condensing chloro-terminated polysulfone oligomers with α, ω -dihydrogensilyl-polydimethylsiloxane in refluxing chlorobenzene solution in the presence of urea as a hydrogen chloride acceptor. The temperature dependences of the electrical conductivity and thermoelectric power (Seebeck coefficient) of copolymers were studied using thin films deposited from a dimethylformamide solution (spin coating method) onto glass substrates. It was established that the various copolymers showed typical semiconducting properties. Some correlations between these properties (activation energy, ratio of carrier mobilities, etc) and molecular structure of the copolymers were found. A model based on band gap representation was found to be suitable for explanation of the electronic transport mechanism through the studied copolymers in thin films. The study of the transmission and absorption spectra (in the spectral range from 300 nm to 1400 nm) evidenced that the indirect allowed optical transitions were predominant. The values of the optical energy band gap (ranged between 1.50 eV and 1.70 eV) are in agreement with values of width of the forbidden band calculated from the temperature dependence of the electrical conductivity.     

玻璃纤维/环氧树脂复合材料热分解动力学参数的确定

采用热重分析仪对空气和氮气气氛中的玻璃纤维增强环氧树脂基复合材料进行热分析,得到该材料在空气气氛中的烧蚀热为3125～3440J/g,而在氮气气氛中并未出现明显的氧化放热峰。基于阿伦纽斯形式的多步分解模型和直接解法,计算了该材料在空气气氛中的热分解动力学参数。分析表明:阿伦纽斯形式的多步分解模型能够较好地描述该材料的热分解过程;直接解法适用于计算复合材料的热分解动力学参数;确立的热分解动力学参数是正确有效的。     

Rheological Property and Thermal Conductivity of Multi-walled Carbon Nano-tubes-dispersed Non-Newtonian Nano-fluids Based on an Aqueous Solution of Carboxymethyl Cellulose

The non-Newtonian nano-fluids with 0.1, 0.5, 1, and 2 wt% of multi-walled carbon nano-tubes have been prepared by dispersing different amounts of multi-walled carbon nano-tubes into an aqueous solution of carboxymethyl cellulose at a weight fraction of 3 wt%, respectively. The nano-fluids exhibit the shear-thinning rheological behavior. The viscosity of the nano-fluid increases with the weight fraction of multi-walled carbon nano-tubes and decreases with the increase in temperature. The thermal conductivity of all the nano-fluids is higher than that of the base liquid. The thermal conductivity enhancement is as high as 14.6% for the nano-fluid containing 2 wt% of multi-walled carbon nano-tubes.