聚碳酸亚丙酯/聚甲基丙烯酸甲酯复合材料热降解动力学研究

利用溶液共混法制备聚碳酸亚丙酯/聚甲基丙烯酸甲酯(PPC/PMMA)复合材料,采用热重分析法研究PPC/PMMA热性能,结果表明PMMA的加入可以有效提高PPC的热稳定性能。以多升温速率法对PPC/PMMA热降解动力学进行研究,利用Friedman法、Kissinger法、Flynn-Wall-Ozawa法、Coats—Redfem方法对热降解动力学数据进行分析,确定PPC/PMMA热分解反应机理函数为Avrami-Erofeev方程,遵循一种热降解机理。     

Thermo-mechanical properties of poly(vinylidene fluoride) modified graphite/poly(methyl methacrylate) nano composites

Poly(methyl methacrylate) (PMMA) nano composites were synthesized by melt compounding technique. Different graphite loadings were investigated, including some treated with poly(vinylidene fluoride) (PVDF). A homogeneous dispersion of graphite throughout the PMMA matrix was observed under microscopic analysis. Thermo-gravimetric analysis showed the incorporation of graphite resulted in improvement of thermal stability of neat PMMA. Dynamic mechanical thermal analysis also showed a significant improvement in the storage modulus over the temperature range of 25–150 °C. Coating the graphite with a small amount of PVDF was found to further extend the improvement in the modulus of the PMMA nano composite at 1 wt.% graphite loading.     

介孔纳米羟基磷灰石/左旋聚乳酸复合材料的制备及性能

为考察介孔纳米羟基磷灰石(MHA)/左旋聚乳酸(PLLA)复合材料的性能,以十六烷基三甲基溴化铵(CTAB)为模板合成MHA,采用溶液相分离结合粒子沥滤法制备了不同纳米粒子含量的MHA/PLLA多孔支架复合材料,考察了其抗压缩性能和淬断面微观结构。采用溶液浇注法制备了MHA/PLLA复合膜,并对其拉伸性能和拉伸断面微观结构进行了研究。FTIR、XRD、TEM和氮气吸附测试等结果显示:合成的MHA具有典型的晶体结构、介孔结构和较高的比表面积。力学测试结果显示:在发生10%压缩形变时,填料含量为1%、5%和10%的MHA/PLLA多孔支架复合材料的抗压缩强度随填料含量增加而提高,与相应含量的纳米羟基磷灰石(HA)/PLLA多孔支架复合材料相比,分别提高了约37.0%、67.7%和144.7%。在填料含量为5%和10%时,MHA/PLLA复合膜的拉伸强度较HA/PLLA复合膜分别提高约38.7%和46.1%,拉伸模量分别提高约35.4%和14.5%。而且MHA/PLLA复合膜具有更高的断裂伸长率,填料含量为1%、5%和10%时断裂伸长率分别较HA/PLLA复合膜提高约91.3%、79.7%和96.1%。FESEM结果显示:尤其当填料含量较高时,MHA/PLLA多孔支架复合材料或复合膜中填料粒子分布较HA/PLLA中均匀。结果表明:与HA/PLLA复合材料相比,随着MHA含量增加,MHA/PLLA复合材料具有更好的力学性能,MHA在PLLA基体中分布相对更均匀。     

Cadmium sulfide photoluminescence in poly(methyl methacrylate)-matrix composites

Poly(methyl methacrylate)-matrix composites containing cadmium, lead, and zinc sulfides and also mixed (cadmium lead and cadmium zinc) sulfides were prepared by reacting metal salts with thioacetamide. The transmission of the composites in the range λ > 500 nm is 92% at absorbing layer thicknesses of ≤5 mm. The photoluminescence (PL) of the composites in the wavelength range 500–820 nm is due to the cadmium sulfide, and that in the wavelength range 300–550 nm arises from the zinc sulfide. It results from radiative recombination at levels of extrinsic structural defects in CdS and ZnS, respectively. The PL excitation spectra contain excitonic absorption bands of cadmium sulfide and zinc sulfide quantum dots. The PL of the cadmium sulfide in the composites is influenced by the presence of lead(II) and zinc(II) ions and the complexation of cations on the surface of the particles.     

高分子量聚甲基丙烯酸甲酯的制备

通过悬浮聚合法制取了分子量在100万～150万范围的聚甲基丙烯酸甲酯(PMMA).研究了温度、引发剂浓度、转化率对聚合物分子量的影响情况,用粘度法测量了PMMA的分子量.结果表明:温度升高、引发剂用量增加使得聚合物分子量降低;随反应的进行和单体转化率提高,聚合物分子量增大并趋于定值.在单体:水相=1:5(质量比),过氧类引发剂浓度1%,反应温度60～70℃,反应时间5h左右的实验条件下,制备得到了高分子量PMMA.     

聚甲基丙烯酸甲酯包覆十二醇微胶囊的制备及表征

以相变物质正十二醇(DA)为芯材,聚甲基丙烯酸甲酯(PMMA)为壁材,采用悬浮聚合法制备了正十二醇-聚甲基丙烯酸甲酯(DA@PMMA)微胶囊。通过差示扫描量热仪(DSC),扫描电镜(SEM),透射电镜(TEM),傅里叶变换红外光谱仪(FIIR)和热重分析仪(TGA)等仪器对微胶囊进行检测表征。结果表明:当工艺为苯乙烯-马来酸甘钠盐(SMA)加入量占DA质量的7.5%,偶氮二异丁腈(AIBN)加入量占单体甲基丙烯酸甲酯(MMA)质量的7.5%,芯材壁材质量比为2∶1,搅拌速度为1 000r/min时,所制备的微胶囊整体性能最好。DA@PMMA微胶囊为球形,平均粒径26μm,DA@PMMA微胶囊中DA的质量分数为66%。DA@PMMA微胶囊的熔化焓和结晶焓分别是137.6J/g和132.8J/g。TGA和FIIR的分析表明,DA@PMMA微胶囊具有良好的性能。     

Pickering乳液技术制备纤维素纳米纤丝-还原氧化石墨烯/聚甲基丙烯酸甲酯电磁屏蔽复合材料

利用纤维素纳米纤丝（CNF）和氧化石墨烯（GO）共稳定的含有聚甲基丙烯酸甲酯（PMMA）的Pickering乳液法,并经抽滤、还原、热压等工艺制备高性能的纤维素纳米纤丝-还原氧化石墨烯/聚甲基丙烯酸甲酯（CNF-rGO/PMMA）电磁屏蔽复合材料。通过调节油相中聚合物的质量浓度、水油体积比,从而调控GO在复合材料中的质量分数。研究GO还原方式、质量分数及热压过程对所制备的CNF-rGO/PMMA电磁屏蔽复合材料的形貌结构与性能的影响。CNF-rGO/PMMA电磁屏蔽复合材料中GO经水合肼处理后有效还原为rGO,热压工艺使包裹在PMMA颗粒外的CNF-rGO片层与PMMA颗粒紧密堆积并形成交联的三维导电网络从而具有优异的导电率,在X波段不同频率（8.2~12.4 GHz）下具有良好的电磁屏蔽效能及稳定性,电磁屏蔽效能可达20 dB以上,可用于民用电磁屏蔽材料。      

Poly(vinylidene fluoride)-assisted melt-blending of multi-walled carbon nanotube/poly(methyl methacrylate) composites

Multi-walled carbon nanotubes (MWNTs) were sonicated in the dimethylformamide solution of poly(vinylidene fluoride) (PVDF). The PVDF-covered MWNTs were then melt-blended with poly(methyl methacrylate) (PMMA). The dynamic mechanical behavior of various composites was studied. The presence of a small amount of PVDF leads to a significant improvement in the storage moduli of the MWNT/PMMA composites at low temperatures. The storage modulus of a PVDF/MWNT/PMMA composite containing 0.5 wt.% PVDF is almost twice as that of a MWNT/PMMA composite at 50°C. However, a further increase in the PVDF content leads to a reduction of the storage modulus. The beneficial effect of PVDF diminishes at higher temperatures.     

Effect of hydrophilic–hydrophobic balance on biocompatibility of poly(methyl methacrylate) (PMMA)–hydroxyapatite (HA) composites

The purpose of this study is to put in evidence the correlation between hydrophilic/hydrophobic balance and biocompatibility of PMMA–HA composites, in order to select the best composites for futures clinical applications. For this purpose, PMMA–HA cements with different compositions were prepared and static contact angle measurements, water absorption and gingival fibroblasts cell culture were performed and discussed.     

Surface characterizations of conductive poly(methyl methacrylate)/polypyrrole composites

The composites of poly(methyl methacrylate) and polypyrrole (PMMA/PPy) were prepared by a chemical oxidation of pyrrole in a PMMA latex medium resulting in a network like structure of polypyrrole embedded in the insulating polymer matrix. Water was used as the dispersion medium. The content of polypyrrole was determined by elemental analysis as varying from 0.25 wt.% to 10 wt.%. The electrical conductivity of prepared composites depends on the concentration of polypyrrole and reached values of between 1 × 10_{– 9} S/cm to 0.1 S/cm The surface of powder form of PMMA/PPy composites was characterized by X-ray photoelectron spectroscopy (XPS) and by scanning electron microscopy (SEM). The antistatic properties of compression moulding form of composites were tested.     

Processing and properties of poly(methyl methacrylate)/carbon nanofiber composites

Single wall carbon nanotubes, multiwall carbon nanotubes, as well as carbon nanofibers (CNF) are being used for reinforcing polymer matrices. In this study, poly(methyl methacrylate) (PMMA) nanocomposites have been processed by melt blending, containing two different grades (PR-21-PS and PR-24-PS) of CNF manufactured by Applied Sciences Inc. The amount of nanofibers used was 5 and 10% by weight, respectively. The PMMA/CNF composites were processed into 4 mm diameter rods and 60 μm diameter fibers using the small-scale melt processing fiber spinning equipment. At 5 wt% CNF, composite rods as well as fibers show over 50% improvement in axial tensile modulus as compared to the control PMMA rod and fibers, respectively. The reinforcement efficiency decreased at 10 wt% CNFs. The PMMA/CNF nanocomposite fibers also show enhanced thermal stability, significantly reduced shrinkage and enhanced modulus retention with temperature, as well as improved compressive strength. CNF reinforcement efficiency has been analyzed using the modified Cox model.     

Hot compaction of poly(methyl methacrylate) composites based on fiber shrinkage results

Uniaxial self-reinforced composite poly(methyl methacrylate) (SRC-PMMA) is being investigated as a pre-coat material for the femoral component of total hip replacements. Hot compaction of self-reinforced composites is largely an empirical process which varies the processing parameters of time, temperature and pressure until the desired properties are obtained. Previous work has shown that PMMA fibers have unique thermal relaxation properties dependent upon the retained molecular orientation in them. This work processed composites at times and temperatures that span the relaxation process for a single fiber. It was found that molecular orientation, as measured by birefringence, was lost in composites processed at times greater than relaxation times for single fibers. Flexural properties were also found to vary with processing conditions, with the highest values of 165 ± 15 MPa and 168 ± 3 MPa found at high and low processing times, respectively. These are significantly stronger than unreinforced PMMA which has a flexural strength of 127 ± 14 MPa. It is hypothesized that diffusion between fibers occurs much more quickly than the loss of molecular orientation and it was seen that SRC-PMMA processing conditions can be predicted from the relaxation times and temperatures from single fibers.     

Structure characterization of Ag-Ga/poly(methyl methacrylate) nanoparticles

The Ag-Ga/poly(methyl methacrylate) nanoparticles were prepared in-situ by emulsion polymerization method under ultrasonic irradiation without any initiators or metal reductant. HRTEM, EDS and XRD experiments were performed to characterize the nanoparticles. The results indicated that the nanocomposite particles possessed core-shell structure with diameters of 80-200 nm, as well as excellent monodispersity. The phenomenon that the polymer forms the shell via layer-by-layer self-assembly was found. XRD proved the existence of Ag0.72Ga0.28 and the probability of new Ag-Ga alloy because of two unknown diffraction peaks.     

Mechanical behaviour of poly(methyl methacrylate)

A series of tensile and three-point bending studies was conducted at various temperatures and loading rates using a commercial poly(methyl methacrylate) (PMMA). Tensile properties and fracture toughness data were obtained for the various conditions. In general, both tensile strength and fracture toughness increase with increasing loading rate and decreasing temperatur E. However, when the temperature reaches the glass transition region, the relationships between fracture toughness, loading rate, and temperature become very complex. This behaviour is due to the simultaneous interaction of viscoelasticity and localized plastic deformation. In the glass transition region, the fracture mechanism changes from a brittle to a ductile mode of failure. A failure envelope constructed from tensile tests suggests that the maximum elongation that the glassy PMMA can withstand without failure is about 130%. The calculated apparent activation energies suggest that the failure process of thermoplastic polymers (at least PMMA) follows a viscoelastic process, either glass or transition. The former is the case if crack initiation is required.Deceased.     

原位聚合羟基磷灰石/聚醚醚酮复合材料

通过原位聚合法制备HA/PEEK复合材料,利用X射线衍射仪、红外光谱仪、差示扫描量热仪、扫描电镜对PEEK、HA/PEEK复合材料进行表征。研究表明,基体PEEK的聚合过程受到一定的影响;HA颗粒在基体之中有着优异的分散性。将PEEK、HA/PEEK复合材料压模成型,通过拉伸试验和硬度测量检测材料的力学性能,结果表明,HA的加入对复合材料的力学性能产生较大的影响。     

Blends of poly(methyl methacrylate) and polyamides

The morphology of PMMA blends with different polyamides (PA-6, 6/9 and 12) was investigated by transmission electron microscopy, recognizing PA-6/PMMA as the most miscible pair. Blends of these polymers were prepared from solutions in m-cresol and formic acid and the morphology was highly dependent on the solvent. The morphology and the segregation degree of extruded PA-6/PMMA blends was investigated by scanning electron microscopy and dynamic-mechanical analysis. The compatibilization succeeded by the introduction of a block copolymer of polyamide and poly(ethylene oxide).     

Chemical synthesis of hydroxyapatite/poly(ε-caprolactone) composites

Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂)—biodegradable polymer composites as bone replacement scaffolds were synthesized by a colloidal non-aqueous precipitation technique at room temperature. The starting materials used for synthesizing hydroxyapatite (HA) were Ca(NO₃)₂·4H₂O and H₃PO₄ with a Ca/P ratio of 1.67 while poly(ε-caprolactone) (PCL) was used as the biodegradable polymer. The composites were prepared containing up to 34.5 wt.% HA and PCL polymer without any evidence of phase separation. This paper describes, the synthesis and structure of the HA/PCL composites. In addition, the pH changes during precipitation, the yield of the chemical reaction, and the possible existence of any bond between the ceramic and the polymer including the microstructure of the composites were studied. Finally, the mechanical and thermal properties of the composites were investigated. The results of these studies are described and discussed.     

Electrospun poly(methyl methacrylate) nanofibers and microparticles

Electrospinning at relatively low polymer concentrations results in particles rather than fibers. This particle-formation process can be termed as electrospray. So electrospinning/electrospray is a highly versatile method to process fibers and particles with different morphologies. In this work, poly(methyl methacrylate) (PMMA) micro- and nanostructures with different morphologies (fibers, spheres, cup-like, and ring-like) have been produced by a facile electrospinning/electrospray method. PMMA was electrospun into various morphologies from only DMF without any other solvents. Field emission scanning electron microscope (FESEM) images demonstrate the different morphologies and prove this technique to be an effective method for obtaining morphology-controllable polymer materials by changing the processing parameters. These micro- and nanostructured polymer materials may find applications in drug delivery and filtration media.     

Processing and properties of poly(methyl methacrylate)/carbon nano fiber composites

Single wall carbon nanotubes, multi-wall carbon nanotubes, as well as carbon nano fibers (CNF) are being used for reinforcing polymer matrices. In this study, poly(methyl methacrylate) (PMMA) nanocomposites have been processed by melt blending, containing two different grades (PR-21-PS and PR-24-PS) of CNF manufactured by Applied Sciences Inc. The amount of nano fibers used was 5 and 10 wt%, respectively. The PMMA/CNF composites were processed into 4 mm diameter rods and 60 μm diameter fibers using small-scale melt spinning equipment. At 5 wt% CNF, composite rods as well as fibers show over 50% improvement in axial tensile modulus as compared to the control PMMA rod and fibers, respectively. The reinforcement efficiency decreased at 10 wt% CNF. The PMMA/CNF nanocomposite fibers also show enhanced thermal stability, significantly reduced shrinkage and enhanced modulus retention with temperature, as well as improved compressive strength. The CNF reinforcement efficiency has been analyzed using the modified Cox model.