Effects of nanoparticle size and concentration on optical,toughness, and thermal properties of polycarbonate

The influences of size and content of silicon dioxide (SiO₂) nanoparticles on the morphological, optical, toughness, and thermal properties of polycarbonate (PC) were investigated. The PC nanocomposites were prepared using a twin-screw extruder followed by injection molding. The scanning electron microscope (SEM) micrographs displayed an adequate level of nano-SiO₂ particle distribution within the PC matrix but still revealed some agglomerated particles. Upon increasing the content of nanoparticles, slightly larger agglomerates formed. These agglomerated particles caused a reduction in material transparency due to light loss via reflection and scattering. However, the incorporation of nano-SiO₂ into the PC matrix greatly improved toughness properties and slightly increased glass-transition temperature (T_g), in conjunction with filler content (up to 4 vol %). This was particularly in the case with the smaller sized nano-SiO₂, which not only significantly improved toughness but also enhanced optical properties of the PC nanocomposites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47634.     

PC/MWCNT纳米复合薄膜的制备及性能研究

将表面功能化的多壁碳纳米管(g-MWCNT)添加到质量分数8%聚碳酸酯(PC)的三氯甲烷溶液中,经室温浇筑挥发成膜后,得到光学透明性良好的复合薄膜。经UV-VIS法测定薄膜的透光率得出,当g-MWCNT的添加量为0.05%时,透光率≥85%,弹性模量比纯PC薄膜提高13%,极限拉伸强度与纯PC相当。通过扫描电镜表征和增强机理分析得出,力学性能的提升可归因于碳纳米管的桥接作用和PC-MWCNT界面结合机理。     

Mechanical and thermal properties of polycarbonate,part 1: Influence of free quenching

The effect of different thermal treatments on the mechanical and thermal properties of polycarbonate was investigated. The first quenching procedure which involves the quench of the samples from the melt state to different temperatures allowed improving impact strength and elongation at break for a quenching temperature of 0°C. A second quenching procedure, corresponding to specimens heated again at 160°C (T_g + 15°C) and quenched a second time, showed a better enhancement of the impact strength and elongation at break to the detriment of other properties such as elastic modulus, density, yield stress, and heat distortion temperature, for a quenching temperature of 40°C. This effect was associated to the existence of a relaxation mode around 35°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

聚碳酸酯双向拉伸薄膜的制备与性能

利用流延薄膜挤出机将两种熔体流动速率(MFR)不同的聚碳酸酯(PC)流延成片,并制备双向拉伸PC(BOPC)薄膜,比较了BOPC薄膜成膜的难易及其性能。结果发现:纵、横向拉伸倍率为2.5×2.5时,BOPC薄膜的拉伸模量提高20.0%左右。具有高MFR的PC2407纵、横向拉伸倍率更大,为4.0×4.0。PC2407薄膜的冲击强度为PC3113薄膜的2倍多,当同种PC在拉伸倍率超过2.5×2.5时,薄膜冲击强度降低。PC2407与PC3113薄膜雾度均小于1.60%,随着拉伸倍率的增加而降低;透光率高于90.0%,随着拉伸倍率的增加而减小;有效光散射值较低。与原料相比,PC2407与PC3113薄膜的玻璃化转变温度下降,热分解温度为480.0℃左右。     

Structure and mechanical properties of soy protein materials plasticized by Thiodiglycol

Thiodiglycol (TDG) is a relatively nontoxic compound from organic wastes. By using TDG as a plasticizer with weights from 2.5 to 40%, we prepared soy protein isolate (SPI) films by a compression‐molding technique at 140°C and 15 MPa. The TDG‐plasticized films (SPI–TDG films) were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, dynamic mechanical thermal analysis, thermogravimetric analysis, optical transmittance, and water uptake experiments. The SPI–TDG film plasticized with 25% TDG exhibited good mechanical properties, such as a tensile strength and modulus of 20.3 and 582 MPa, respectively, whereas the SPI–glycerol film with 25% glycerol had a tensile strength and modulus of 16.2 and 436 MPa, respectively. The results from the thermogravimetric analysis and water uptake experiments indicated that the thermal stability and water resistance of the TDG‐plasticized SPI materials were higher than that of the glycerol‐plasticized one. The improvements in the mechanical properties, water resistance, and thermal stability of the SPI–TDG films could be attributed to the strong intermolecular hydrogen bonding between soy protein and TDG and the presence of fewer hydroxyl groups in TDG, as compared structurally with glycerol. This study provided a new plasticizer for the preparation of soy protein materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical and thermal properties of polycarbonate. II. Influence of titanium dioxide content and quenching on pigmented polycarbonate

The effects of quenching temperature including different thermal histories on mechanical, physical, and thermal properties of pigmented polycarbonate (PC/TiO₂) were investigated. Tensile test, Izod impact strength and heat distortion temperature (HDT) were performed on specimens of 3 mm thickness. Pigment content and quenching temperature are two key factors that affect the properties of the materials. A higher content of pigments results in an increase of modulus of elasticity and a decrease of unotched and notched Izod impact strength, as well as elongation at break. A maximum of yield stress and HDT is obtained at 3% of TiO₂, which was considered as the optimum level of pigment. An additional second quenching at 40°C has allowed to improve Izod impact strength and elongation at break of specimens with 3% of TiO₂; whereas modulus of elasticity, density, yield stress, and HDT were minimum at this quenching temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Phase transitions and mechanical properties of nitrocellulose plasticized by glycidyl azide polymer and nitroglycerine

Films of nitrocellulose (NC), glycidyl azide polymer (GAP), and nitroglycerine (NG) have been evaluated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, dynamic mechanical analysis (DMA), and tensile testing. The SEM micrographs demonstrate that, even at low GAP concentration, a portion of GAP will coalesce into spherical domains due to a saturation effect. This is related to the inability of higher molecular weight GAP to effectively situate itself between NC polymer chains. The addition of a small fraction of lower molecular weight NG completely changes this behavior. DMA confirms that two transitions are present and can be attributed to a plasticizer rich phase (β), a polymer rich phase (α) and that NC plasticized with GAP is in accordance with the Gordon-Taylor equation. Tensile results show that the addition of a small fraction of NG to a NC/GAP based-formulation increases elongation at break to values similar to that of the NC/NG base formulation. The combination of these two plasticizers, GAP and NG, allows for the plasticization of NC at significantly lower environmental and human toxicity levels.     

Melt flow properties,mechanical properties,thermal properties and morphology of polycarbonate/highly branched polystyrene blends

A highly branched polystyrene (HBPS) was synthesized via the copolymerization of 4‐(chloromethyl) styrene with styrene using the self‐condensing atom transfer radical polymerization method. The addition of HBPS as a melt modifier for polycarbonate (PC) was attempted. Melt flow properties, mechanical properties, thermal properties and morphology of the blends were studied. The results showed that a significant drop in the blend viscosity occurs immediately on addition of HBPS. Impact strength, tensile strength and glass transition temperature (T_g) of all the blends have not been significantly reduced compared with those of pure PC. The TGA analyses showed that an initial weight loss temperature of all the blends is above 458 °C and slightly low compared with that of pure PC, but all the blends still have excellent thermal stability. Morphological studies using SEM showed that a two‐phase morphology is characteristic of all the blends, with more or less spherical droplets of the minor HBPS phase dispersed in the continuous PC phase. Copyright © 2006 Society of Chemical Industry     

Synthesis and properties of bisphenol-Z polycarbonate via melt transesterification

Polycarbonate (PC) is a thermoplastic engineering plastic with excellent properties, and its excellent dielectric properties have broad application prospects in the field of electronics. In this paper, bisphenol Z (BPZ) and diphenyl carbonate (DPC) are used as raw materials to synthesize special polycarbonate (BPZ-PC) by melt transesterification. The effects of catalyst type, catalyst dosage, molar ratio of raw materials, transesterification reaction time and vacuum degree, polycondensation reaction temperature and time on the molecular weight of the product are investigated, and the optimal reaction conditions are obtained. The chemical structure of the product is verified by FTIR, ¹H-NMR and ¹³C-NMR spectra tests. The thermal properties, mechanical properties, optical properties and dielectric properties of BPZ-PC are evaluated. Therefore, due to its excellent performance, BPZ-PC, a high-performance low-dielectric polycarbonate, can be widely used in high-frequency communication, microelectronics, and aerospace industries.     

注射压缩成型聚碳酸酯制品的低温拉伸力学性能

以聚碳酸酯为材料,利用自行设计带有压缩功能的模具,采用常规注塑成型(IM)和注射压缩成型方法(ICM)对比研究制品在常温和低温环境下的拉伸力学性能;基于单因素实验方法,研究熔体温度、模具温度、模板压缩距离、延迟时间和压缩力对ICM制品残余应力和低温拉伸性能的影响规律。结果表明:在相同的环境温度下,ICM制品较IM制品有较大的屈服应力和弹性模量;低温环境下样品的拉伸性能有所提升,并在-40℃附近出现了聚碳酸酯分子的次级玻璃化转变;残余应力是影响ICM制品低温拉伸性能的主要因素,较高的熔体温度、模具温度、模板压缩距离,以及较短的延迟时间,较小的压缩力会减小ICM制品的残余应力,提高制品的低温拉伸性能。     

聚乙二醇增塑聚乳酸的非等温结晶动力学研究

采用DSC方法对聚乙二醇(PEG)增塑聚乳酸的非等温结晶动力学进行了研究。结果表明,PEG的加入明显提高了聚乳酸的结晶速度。对所得数据分别用Ozawa方程和莫志深方法进行了处理,发现在给定温度范围里非等温结晶时,PLA/PEG主要是以均相成核的三维生长方式结晶;PLA的结晶速度随着PEG分子质量的增加而升高。     

Structure and properties of soy protein films plasticized with hydroxyamine

Two kinds of transparent films of soy protein were successfully prepared by plasticizing with diethanolamine (DEA) and triethanolamin (TEA). The films were hot pressed at 140°C and 20 MPa, and characterized with Fourier transform infrared spectroscopy, scanning electron microscope, ultraviolet–visible spectrometer, differential scanning calorimetry (DSC), thermogravimetric analysis, and tensile testing. The results indicated that films with triethanolamine plasticizers possessed better optical transmittance (more than 80% at 800 nm) than those with diethanolamine and glycerol. All of the sheets exhibited only one T_g in DSC curves. Moreover, the soy protein plastics with TEA had higher thermal stability and mechanical properties, as well as lower water uptake than those with DEA and glycerol, as a result of the strong interaction between TEA and protein molecules. The soy protein materials will be promising for the application in the fields of package and container, substituting for the nongreen polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

多壁碳纳米管/聚碳酸酯复合材料的制备与性能

经硝酸氧化纯化的碳纳米管,在离子液体[Bmim]PF6存在下,溶液混合法制备了MWNTs/PC纳米复合薄膜。利用TEM、SEM对碳纳米管处理前后的形态结构、复合薄膜的微观结构进行了表征,考察了碳纳米管用量对MWNTs/PC复合材料的电学性质和力学性能的影响。结果表明,碳纳米管比较均匀地分散在PC基体中,在[Bmim]PF6作用下改善了碳纳米管与PC的相容性,提高了复合材料的力学性能。同时得出,复合材料的导电阈值出现在碳纳米管质量分数为1.0%～2.0%的范围内。     

Influence of functionalized calcium carbonate nanofillers on the properties of melt-extruded polycarbonate composites

In an effort toward developing better tribological properties of polycarbonate (PC), a reinforcement with calcium carbonate (CaCO₃) nanoparticles (3% by weight), in the size range of 30–60?nm, functionalized using stearic acid, was carried out by melt extrusion method. It was established that scratch resistance of PC/CaCO₃ composites (PCC) improved by 30% in comparison with pure PC. Nevertheless, an assessment of thermal properties using thermogravimetric analysis and differential scanning calorimetry (DSC) indicated an inferior thermal stability of PCC. Thermomechanical properties as obtained from dynamic mechanical analysis revealed an improvement in storage modulus for PCC but loss tangent (tan δ) results indicated lower glass transition (T_g) values in agreement with DSC results. To comprehend the thermal behavior of PCC, degradation kinetics was studied using the model-free method, and it was observed that the presence of organically modified nanoparticles resulted in catalysis of degradation, thus, lowering apparent activation energy (E_α) for PCC at the initial stages of degradation.     

Optical nonlinearity and photoinduced anisotropy of an azobenzene‐containing ionic liquid crystalline polymer

The nonlinear optical properties of an azobenzene‐containing ionic liquid crystalline polymer were investigated using single‐beam Z‐scan and optical Kerr effect (OKE). The polymer film exhibited large nonlinear absorption (～10^?6 cm W^?1) and nonlinear refraction (～10^?11 cm² W^?1) under 532 nm ps excitation. The femtosecond time‐resolved OKE results suggested that the nonlinear optical response time in off‐resonant region was as fast as 300 fs. Moreover, stable molecular reorientation and a large photoinduced birefringence ( ) were achieved in the polymer film with a 405 nm continous wave (CW) laser as pump light. The large optical nonlinearity, ultrafast response, and effective photoinduced molecular reorientation of the polymer films indicated their potential applications in nonlinear photonic devices and optical storage. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Modulus enhancement of polycarbonate by addition of lithium perchlorate

The mechanical properties of polycarbonate (PC) containing lithium perchlorate (LiClO₄), which is found to ionize in PC, are examined. The modulus of PC is greatly enhanced by the addition of LiClO₄ because of the electrostatic interaction between the lithium cation and the carbonyl group in PC molecules. Previously reported organic antiplasticizers, which fill the free volume of polymers, are known to reduce mechanical toughness and heat resistance. However, the addition of LiClO₄ does not sacrifice the advantages of PC, such as heat resistance, transparency, and mechanical toughness. This phenomenon is notable because it is applicable for the enhancement of the mechanical properties of PC. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44882.     

Relationship between degree of polymerization and optical and thermal properties of fluorene in polycarbonate polymers

The influences of average degree of polymerization (D_p) and terminal group on thermal and optical properties of high refractive indexed transparent polymers were investigated. In this study, 9,9‐bis[4–(2‐hydroxyethoxy) phenyl] fluorene (BPEF) homo polymer was selected because it has been used as a representative monomer in high refractive index polymers as well as its unique property. BPEF has stable amorphous phase and reacts like a polymer. Its unique reaction allows continuous investigation from monomer to polymer. For hydroxyl‐terminated polymer, the refractive index (n_d) decreased with increasing D_p. On the other hand, for a phenolic‐terminated group, n_d increased with increasing D_p, and both converged to same value in high D_p region. As for glass transition temperatures (T_g), both terminal group series were increased as D_p increased. Though T_g of hydroxyl‐terminated polymer was higher than that of phenolic‐terminated polymer in the low D_p region, both converged to the same value and the inverse number of T_g had linear correlation against the weight percentage of carbonyl groups (CO), which was calculated by D_p. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45042.     

Optical properties of bismuth tellurite based glass

A series of binary tellurite based glasses (Bi(2)O(3))(x) (TeO(2))(100-) (x) was prepared by melt quenching method. The density, molar volume and refractive index increase when bismuth ions Bi(3+) increase, this is due to the increased polarization of the ions Bi(3+) and the enhanced formation of non-bridging oxygen (NBO). The Fourier transform infrared spectroscopy (FTIR) results show the bonding of the glass sample and the optical band gap, E(opt) decreases while the refractive index increases when the ion Bi(3+) content increases.     

Key properties to understand the performance of polycarbonate reprocessed by injection molding

The reprocessing of injection‐molded polycarbonate was studied in an attempt to understand the physical background for the variation of its performance upon sequential molding cycles. The effect of reprocessing on different properties of the moldings and the regrind is presented and discussed. A quantitative analysis of the Fourier transform IR spectra indicates that phenol and carbon dioxide are released during the initial cycles, probably due to molecular scission near the chain ends. Most of the results obtained agree well with the findings reported elsewhere. Essentially, the molecular weight, the free volume, and the specific volume were found to be critical properties for understanding the global performance of the moldings. Both the free volume and the reciprocal of the molecular weight depend linearly on the number of reprocessing cycles. Based on these properties, it is possible to develop relatively simple relations to estimate the variation of the rheological, optical, and mechanical properties with the number of reprocessing operations. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1393–1400, 2000     

Correlation between structural evolution and rheological properties for polycarbonate in the molten state

In this work, multiple rheological and molecular structure characterization methods are utilized to investigate the melt post-polycondensation (MPP) process of polycarbonate (PC) at high temperatures (260–300°C) under a nitrogen atmosphere. We find some unexpected phenomena that the complex viscosity of PC melt rise rapidly and it reaches an extraordinarily high value of about 10⁶ Pa·s during the MPP process of 10 h at 300°C. Dissoluble PC and insoluble gel residue are separated and both fractions are analyzed by gel permeation chromatography, ¹H-NMR, and pyrolysis-gas chromatography mass spectrometry. Results show that the molecular weight of dissoluble PC significantly increases at the early stage of the reaction (less than 1 h). After that, it continues to reduce due to the occurrence of branching reactions and degradation reactions caused by high temperature reactions for a long time. Chemical structure analysis indicates that the same two branched structures are discovered in both dissoluble PC and insoluble gel residue, the changes in structures indicate that no new structures are formed during the crosslinking reaction. According to this study's results, we clearly understand the correlation between the rheological properties and structural changes for PC in the MPP progress.