乳聚丁苯互穿网络型热塑性弹性体的制备

以丁苯胶乳为种子乳液,苯乙烯、甲基丙烯酸甲酯、丙烯腈或它们的混合物的硬单体,用氧化还原引发体系,经种子乳液聚合法同备出复合乳液,絮凝干燥后所得互穿聚合物网络可热塑性反复加工。考察了硬单体的种类和用量、交联剂的种类及用量、反复加工次数对聚合物力学性能的影响。用透射电子显微镜观察了乳胶粒微观形态,结果表明：用混合单体,聚合物力学性能较优,以３５份Ｓｔ＾＋ＭＭＡ为第二单体制备的聚合物的攫断伸长率为４００％,拉伸强度为９．３ＭＰａ,３００％定伸应力为７．６ＭＰ,撕裂强度为７３．９ｋＮ．Ｍ＾－１,邵尔Ａ型硬度为８４。     

Monitoring nonisothermal crystallization of thermoplastic polymers using a quartz crystal resonator

A new monitoring device for the nonisothermal crystallization of thermoplastic polymers, polyethylene, polypropylene, polystyrene, and polyamide, is developed utilizing a quartz crystal resonator, and its performance is evaluated by comparing the measurements with the results of DSC thermoanalysis and microscopic observation. The experimental results of four different polymers indicate that the variation of resonant freency of the quartz crystal resonator is a good means to monitor the crystallization process. Though the measurements of melting and crystallization are close to the DSC outcome, more deviation is observed with the new device. The change in crystalline morphology during the crystallization process is also detected from the slope changes of the frequency decrease. In comparison with the microscopic observation of polymer films, it is found that the processes of nucleation and crystal growth in nonisothermal crystallization can be explained with the variation of the resonant frequency of the quartz crystal resonator. In addition, crystallization kinetics is modeled with the Avrami equation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Impact of renewable carbon on the properties of composites made by using three types of polymers having different polarity

Pine wood derived biocarbon (BioC) is investigated as a renewable alternative to carbon black (CB) for plastics and composites applications. Three different polymers with different polarity were used to prepare the composites: polypropylene (PP), polylactic acid (PLA), and polyamide 6 (PA6). Comparatively, CB had a nodule size of ~300 nm and surface area of 8 m²/g, whereas BioC showed an average particle size of ~950 nm and surface area of ~260 m²/g, respectively. CB, in the composites, was found in large aggregations in the flow direction (FD), while BioC particles showed a better dispersion. Aggregation of CB affected mostly the mechanical strength of the composites. Furthermore, it was found that the overall performance of composites was influenced more by the polarity of the phases, rather than the particle size or the surface area of the fillers. Even when the polarity of the particles had an expected trend (PA6 > PLA > PP with BioC > CB), the work of cohesion obtained for the composites was PA6-BioC > PP-BioC > PLA-BioC, showing, in particular, that the chain-to-chain intermolecular forces in neat PLA are stronger as compared to those developed by the particle-matrix interactions.     

Compatibility Investigations on Polymer‐Fiber‐Reinforced Cements Modified with Polymer Latexes

Summary: In construction, polymer fibers are commonly applied beside steel, glass and mineral fibers to improve material's flexibility to shear stress. As in other composite systems, there are compatibility problems present between the fibers and the cement due to the different chemical natures and the different thermal expansion coefficients of the cement and the polymers. Within this study the interactions between two Portland cements and polymer fibers were investigated by SEM and solid‐state NMR spectroscopy. To improve the wetting ability of the polymer fibers by the cement matrix, redispersible latex powders were successfully applied to improve the adhesion between the cement matrix and the fibers. Within this study, several solid‐state nuclear magnetic resonance (NMR) spectroscopy methods, detecting ¹H, ¹³C, ²⁷Al and ²⁹Si nuclei, and scanning electron microscopy (SEM) were applied. Thus, cement pastes, inorganic additives and organic admixtures could be monitored individually.

SEM images of the interface between poly(propylene) fibers and Portland cement, hardened and hydrated in the presence of a 2 wt.‐% poly[(vinyl acetate)‐co‐ethylene] latex.     

Morphology development in polychloroprene–polystyrene latex interpenetrating polymer networks

Latex interpenetrating polymer networks (LIPNs) have been prepared using a crosslinked polychloroprene latex as the seed emulsion, followed by the in situ polymerization of styrene, typically with a 10% divinyl benzene crosslinker. Polychloroprene–crosslinked polystyrene (XPS) ratios ranging from 70/30 to 40/60 were used, with the second monomer being added as a single aliquot rather than by “starvation” routes. The majority of the work has been conducted using the water‐soluble persulfate initiator method, which entails lengthy (∼ 6 h) polymerizations. To follow the development of microstructure, polymerizations were also stopped at 0.5, 1, and thence hourly intervals up to 6 h, so that any effect of time on shell and domains could be seen by transmission electron microscopy (TEM). Parallel studies using azo‐bis(isobutyronitrile) (AIBN) as initiator at the same temperature were conducted. Products were also studied, after staining, by TEM. For the persulfate initiator, domain structures predominated for the 70/30 ratio, but polystyrene‐rich shells are found in all cases, with increasing thickness as the chloroprene/styrene ratio was reduced. The styrene‐rich products (i.e., 40/60 Neoprene/XPS ratio) appear to have larger unstained domains suggesting phase separation. For the AIBN‐initiated styrene polymerization, shells are less evident, and where they exist, are both thinner and less continuously developed. Domain sizes are somewhat larger. This relatively hydrophobic initiator has caused polymerization predominately in the interior of each latex particle. The particle size distribution of the seed neoprene latex is broad and bimodal. As the LIPNs form, the larger diameter component increases and little evidence for fresh nucleation, in the form of small diameter particles, is seen. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 629–638, 1999     

Shape memory composites based on a thermoplastic elastomer polyethylene with carbon nanostructures stimulated by heat and solar radiation having piezoresistive behavior

A thermoplastic elastomer polyethylene (TEPE) based on an ethylene/1‐butene copolymer having shape memory effect (SME) without any chemical modification is presented and the effect of adding either carbon nanotubes or thermally reduced graphite oxide is analyzed. For electrical percolated samples, the development of a polymer sensor that changes its electrical conductivity under solar radiation triggered by SME is further presented. Our results showed that programmed samples recovered their permanent shape showing SME under a direct heating stimulus at 60 °C. The addition of carbon nanostructures increased the times needed to reach 100% recovery as compared with pure TEPE. Noteworthy, the SME was also stimulated remotely by solar radiation increasing the sample temperature. Composites presented a faster SME under this remote radiation process as compared with pure TEPE due to their higher radiation absorption. Percolated TEPE/carbon nanotube composites displayed further a decrease in the electrical resistivity during SME under this solar radiation. Finally, our results showed that the glass transition also triggered the SME in these samples allowing the development of triple shape memory polyethylenes without any chemical crosslinking process. Based on these findings, a simple route was developed to produce double, or even triple, shape memory piezoresistive polyethylenes that can be activated remotely by solar radiation. © 2018 Society of Chemical Industry     

Study on the miscibility and rheological properties of thermotropic liquid crystalline polymers in thermoplastic matrices

The interfacial properties of polymer blends of the engineering thermoplastics (TPs) polycarbonate (PC) and polyethersulfone (PES) with thermotropic liquid crystalline polymers (TLCPs) were studied using FTIR and DSC. The TLCP/TP blend systems were mainly immiscible. The viscosity properties of the TLCP/TP blends were analysed. The mechanism of the viscosity variation of the blends is discussed. Based on the assumptions given in this paper, a reasoned theoretical formula of the blend viscosity is derived to express the viscosity reduction of the TLCP/TP blends.     

On the development of natural fiber composites of high‐temperature thermoplastic polymers

A new method is presented for the development of natural fiber composites of high‐performance thermoplastic polymers considering poly(phenylene ether) (PPE) and wood flour as an example system. The large gap between the high processing temperature of PPE, typically between 280 and 320°C, and the low decomposition temperature of wood flour, about 200°C, was reduced by using a reactive solvent, a low molecular weight epoxy. The epoxy formed miscible blends with PPE, which offered much lower viscosity compared to PPE and processing temperatures well below the decomposition temperature of wood flour. In addition, the epoxy component accumulated around the polar wood flour particles upon polymerization during the fabrication step. The composite materials consisted of a thermoplastic continuous phase and two dispersed phases, one of polymerized epoxy and the other of wood flour particles coated with polymerized epoxy. These composites offered a significant reduction in density and better mechanical and physical properties when compared to commercially available grades of engineering polymer blends filled with short glass fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2159–2167, 2002     

Dielectric properties of polymer/ceramic composites based on thermosetting polymers

Summary A series of thermosetting polymer/ceramic composites were prepared. Three kinds of thermosetting polymers, i.e. cyanate resin, bismaleimide resin, and epoxy resin, were used as matrixes, and BaTiO₃ particles were as fillers. The dielectric properties of these composites were investigated. Experimental data of the dielectric constants were fitted to several theoretical equations in order to obtain the best-fitting equations of the dielectric constants of these composites. The result indicates that the dielectric constants of composites all increase with the increase of BaTiO₃ content. Using bismaleimide resin and epoxy resin as matrixes, the dielectric losses both increase obviously as the amount of BaTiO₃ particles is increased, but the dielectric loss of cyanate/BaTiO₃ composite decreases. With the increase of the frequency, the variation ranges of the dielectric constant and dielectric loss of cyanate/BaTiO₃ composite are both the smallest. The predications of the effective dielectric constants by Lichterecker mixing rule are in good agreement with experiment data.     

D相法微乳胶的研究与应用

采用D相法，由烷基苯磺酸钠（LAS）、醇醚（AE）、多元醇、混合苯等制备了微乳胶，以正交实验考察了各种组分质量比对所得溶液界面张力的影响，最佳配方为：50g质量分数为20％的多元醇溶液，7g混合苯，31g界面活性剂。微乳胶的界面张力为3，70mN／m，微乳胶澄清、透明，热力学稳定，久置不分层。以此微乳胶酸液进行了油井现场应用，结果表明，平均单井日增液0，8t，平均单井日增油0．7～1．8t，平均含水单井降低10％～18．5％，这在同类措施中是不多见的。     

Natural fiber composites of high‐temperature thermoplastic polymers: Effects of coupling agents

Our earlier paper (Jana, S.C.; Prieto, A. J Appl Polym Sci 2002, 86, 2159) on the development of natural fiber composites of high‐performance thermoplastic polymers described a new methodology for the manufacturing of composite materials of a high‐temperature thermoplastic polymer, poly(phenylene ether) (PPE) and wood flour, a cellulosic natural filler. A thermosetting epoxy, used as a reactive solvent, reduced the processing temperature of PPE/epoxy blends to well below the decomposition temperature of natural fillers. In addition, the epoxy component, upon polymerization, formed coating layers around the filler particles to provide resistance against moisture diffusion and attacks by acids and alkali. This article describes the results of an investigation on two outstanding issues: (1) the influence of cellulosic wood particles and coupling agents on the speed of epoxy curing and reaction‐induced phase separation and (2) the effects of coupling agents on the morphology of crosslinked epoxy at the surfaces of natural fillers and mechanical properties of the composites. It was found that wood particles expedited epoxy curing in the composites; the extent of epoxy curing, however, was reduced in the presence of coupling agents. Also, the coupling agents promoted complete coverage of wood flour particles by polymerized epoxy, although the mechanical properties deteriorated over systems without coupling agents. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2168–2173, 2002     

Natural fiber suspensions in thermoplastic polymers. I. Analysis of fiber damage during processing

The final properties of the composites materials are strongly dependent on the residual aspect ratio, orientation, and distribution of the fibers, which are determined by the processing conditions. Present work is a systematic study of the influence of natural fiber concentration on its damage during all the steps involved in the composite compounding. The system under study is cellulose fiber‐reinforced polypropylene. The fiber geometrical parameters—length, diameter, and aspect ratio—are measured, and their statistical distributions are assessed for different concentrations. It is found that the higher the fiber concentration, the lower the fiber damage. These results evidence a difference in behavior between the damage of flexible natural fiber and rigid ones. The results are analyzed in terms of fiber concentration regimes, fiber–fiber interaction, flexibility, and entanglements. Two competitive mechanisms of the fiber interaction are proposed for explaining the fiber damage behavior during the flow of the flexible natural fiber suspensions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2501–2506, 2007     

星形聚合物的功能化应用研究进展

简要介绍了星形聚合物的结构、种类。从星形聚合物复合材料、星形聚合物光电学材料、星形聚合物基因载体和星形聚合物药物载体几方面综述了星形聚合物功能化的研究及应用情况,并展望了星形聚合物的未来发展。     

Dispersivity of rubbers in thermoplastic polymers

The main factors influencing the dispersivity of rubbers (nitrile and ethylene–propylene) in nylon 6 (PA-6) and polypropylene (PP) are investigated. On the basis of an equation, describing the influence of interfacial tension and viscosity ratio of disperse and matrix phases on the average size of dispersed phase particles, analysis of dispergation process in researched blended systems has been conducted. The limits of applicability of a given equation were established. It was shown that the best dispersivity of rubbers in the PA matrix is observed in that case when the viscosity values of initial components of a blend are close to each other. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1563–1567, 1999     

Thermal properties of strained thermoplastic polymers

Injection moulded tensile bars of several amorphous and semi-crystalline thermoplastic polymers have been deformed uniaxially to a macroscopic strain of 40% so that they showed necked and unnecked regions. From both the necked and unnecked regions of the tensile bars the specific heat and the thermal expansion coefficient were measured. The specific heat of the necked regions decreases about 20% with respect to unstrained samples for semi-crystalline polymers at temperatures between 40°C and 60°C and for amorphous polymers at temperatures between 50°C and 70°C. The thermal expansion coefficient becomes negative at these temperatures. A smaller negative expansion coefficient is observed even in the unnecked region although nearly no change in specific heat can be observed. There is also an increase in the heat of fusion of the semi-crystalline specimens of the necked region. Strain rate dependent effects on specific heat and thermal expansion were not observed within the accuracy of thermal analysis.     

External lubrication of high-temperature thermoplastic polymers

External lubrication of high-temperature thermoplastic polymers was studied experimentally. It was found that the nature of the lubrication fluid has a pronounced effect upon the behavior of the contact. It is postulated that premature failure of PEEK-lubricated contacts is caused by the migration of linear carboxylic acids into the polymer matrix at elevated temperatures, thereby producing significant plasticization. A sequence of events leading to failure is given and some rationale for it provided. © 1993 John Wiley & Sons, Inc.     

Miscibility of polyethyloxazoline with thermoplastic polymers

Polyethyloxazoline (PEOx) blends with several other thermoplastic polymers were examined by differential scanning calorimetry (DSC) for miscibility. Styrene/acrylonitrile (SAN) copolymers having compositions in the range of about 20–40% acrylonitrile (AN) by weight were found to be miscible with PEOx whereas SANs outside this range were not. The polyhydroxyl ether of bisphenol A (Phenoxy) was also found to be miscible with PEOx. A vinylidene chloride copolymer (Saran) was found to be partially miscible with PEOx, whereas poly(methyl methacrylate) and polycarbonate were not miscible at all.     

Latex interpenetrating polymer networks based on high styrene resin

Latex interpenetrating polymer networks based on high styrene resin (“HSR300”) as seed latex and polystyrene as the second polymer have been synthesized in different compositional ratios. The morphology of resultant materials was determined by field emission electron microscopy, atomic force microscopy, transmission electron microscopy, and by dynamic mechanical analysis. A polystyrene (PS) rich shell is observed in the latex particles. At higher second polymer ratios, a PS‐rich shell can be resolved, but in general the majority of the polymer is incorporated as domains within each particle. The two crosslinked polymers are well intermeshed at the microscopic level, as reflected not only by morphology but also by single tan δ peaks in dynamic mechanical analysis (DMA) data. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 622–628, 1999     

Polymer latex containing carboxylic acid functional groups. II. Humidity‐sensitive properties of rigid films made from MMA and AA

The polymer latexes of poly(MMA‐AA) were synthesized using two techniques: soapless seeded emulsion polymerization, and soapless emulsion copolymerization. Then a series of rigid polymer films containing a COOH group were prepared from the synthesized latex. The humidity‐sensitive properties of the polymer films were investigated. Our studies confirmed that there exists both an optimum ratio of hydrophilic to hydrophobic monomers and initial structure of the latex particle that provides the humidity‐sensitive polymer film with excellent water resistivity and sensitivity to humidity. In addition, little hysteresis and quick response were observed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3121–3129, 1999