Coating solvent effects producing adhesion to molded plastic parts

While adhesion is of paramount importance to ensure durability and quality of a coating system, solvents have long been known to affect coating adhesion to molded plastics, including polyolefins. Varions research group in their characterizations of interfaces and/or adhesion to plastics, have produced much understanding of the role played by solvents in adhesion to plastics. However, the 'goodness' of a coating solvent for the plastic, defined as a small Flory interaction parameter χ12, was not indicative of the quality of the coating adhesion to the molded plastic substrates under consideration. For instance, coating adhesion to either polypropylene or ethylene–styrene interpolymer substrates, as affected by the coating solvent, was poorly related to the solvent–polymer miscibility, the magnitude of solubility parameter mismatch, or the ability of the solvent to swell the polymer bulk, except where such swelling produced a topographical change to the polymer surface. Though the topographical change was different for polypropylene compared to the interpolymer surface, if a coating solvent induced little or no change in the topography of a molded plastic then little or no coating adhesion to the plastic was observed. Polymer surface crystallinity reduced the amount of topographical change caused by a solvent and, likewise, reduced adhesion of a coating containing the solvent. The alteration of topographical features by solvent provides an adhesion mechanism and an explanation for the reported formation of diffuse interfaces and how a coating solvent could expose sub-surface domains within a polymer substrate.     

PVC-U注塑制品红纹现象浅析

考虑到北方的气候,结合天津中财型材有限公司设备、模具、混料及原材料等条件,分析并验证了PVC-U注塑制品表面出现红纹的缺陷。在实际生产中,可通过修模、调试配方、更换原辅料等措施来解决。结果表明:PVC树脂质量和模具结构对制品的表观质量和力学性能影响很大。     

Self-assembled organic semiconductors for monolayer field-effect transistors

Recent data on the structures and properties of self-organized molecules used for the production of the semiconducting layer in self-assembled organic monolayer field-effect transistors are reviewed. Methods for fabrication of these transistors are presented together with their advantages and shortcomings. Electric characteristics of the produced devices are compared. Major structural regularities for selection of the reactive group in self-organized semiconductor oligomer molecules are elucidated with respect to the type of substrate.     

Numerical and experimental studies on the ejection of injection‐molded plastic products

Numerical and experimental studies have been conducted on the ejection stage of plastics injection molding process. A numerical approach is proposed to predict the ejection force from the mold‐part constraining and friction forces as the product cools in the mold cavity up to the moment of ejection. The finite element thermoviscoelastic solidification analysis has taken into account the stress and volume relaxation behavior of polymers under the cavity‐constrained condition. The predicted ejection force and its distribution over ejector pins are validated by injection molding experiment of rectangular boxes using a polycarbonate resin. Different cases of the ejector pin layout are evaluated to examine the effect of the number, location and dimension of ejector pins, so as to identify the balanced layout causing minimum stress and deformation to the product. The approach is also applied to another product geometry which shows complex distribution of the mold‐part constraining and friction forces and involves multi‐step operations in the demolding stage.     

Modeling material property heterogeneity in fiber‐reinforced injection molded plastic parts

Fiber reinforced plastic parts manufactured by injection molding have heterogeneous stiffness and strength behavior due to the molding process influence on the fiber orientations. This paper presents a methodology for determining the process‐dependent anisotropic and inhomogeneous mechanical properties of injection‐molded parts using a thickness‐wise layered homogenization technique. This technique produces an equivalent laminated meso‐scale representation at any location in the part and enables point‐wise application of the existing laminated plate and shell theories. The methodology is demonstrated by illustrating property variations in edge‐gated and center‐gated plaques. Spatial variations of elastic moduli, shear modulus, and Poisson's ratio are modeled. The model can be conveniently embedded within finite element structural analyses accounting for the process‐dependent material heterogeneities within the structure. POLYM. COMPOS., 26:98–113, 2005. © 2004 Society of Plastics Engineers     

The influence of maltodextrins on the structure and properties of compression‐molded starch plastic sheets

Starch plastic sheets were prepared by compression molding of starch‐based plastic granulates. The granulates were prepared by extrusion processing of mixtures of granular potato starch and several maltodextrins (5% w/w) in the presence of glycerol and water as plasticizers and lecithin as melt flow accelerator. The materials were semicrystalline, containing B‐type, V_h‐type, and E_h‐type crystallinity. The properties were dependent on water content. For the materials, a brittle‐to‐ductile transition occurred at a water content in the range of 11–12%, which was in accordance with the observed glass transition temperature. The structural and mechanical properties were a function of starch composition and maltodextrin source as well as molding temperature. The amount of granular remnants and residual B‐type crystallinity decreased with increasing processing temperature. The amount of recrystallized single‐helical amylose increased with increasing temperature. At molding temperatures in the range of 180–200°C, a sharp decrease in starch molecular mass occurred. The influence of molding temperature was reflected in a sharp increase in elongation at molding temperature above 160°C and a gradual decrease in elastic modulus. The tensile strength showed an initial small increase up to 160°C and a sharp decrease at higher molding temperatures. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2207–2219, 1999     

Recent advances in solid‐state organic lasers

Organic solid‐state lasers are reviewed, with a special emphasis on works published during the last decade. Referring originally to dyes in solid‐state polymeric matrices, organic lasers also include the rich family of organic semiconductors, paced by the rapid development of organic light‐emitting diodes. Organic lasers are broadly tunable coherent sources, potentially compact, convenient and manufactured at low cost. In this review, we describe the basic photophysics of the materials used as gain media in organic lasers with a specific look at the distinctive features of dyes and semiconductors. We also outline the laser architectures used in state‐of‐the‐art organic lasers and the performances of these devices with regard to output power, lifetime and beam quality. A survey of the recent trends in the field is given, highlighting the latest developments in terms of wavelength coverage, wavelength agility, efficiency and compactness, and towards integrated low‐cost sources, with a special focus on the great challenges remaining for achieving direct electrical pumping. Finally, we discuss the very recent demonstration of new kinds of organic lasers based on polaritons or surface plasmons, which open new and very promising routes in the field of organic nanophotonics. Copyright © 2011 Society of Chemical Industry     

高性能P-型有机薄膜晶体管材料(OTFT)进展

有机薄膜晶体管(Organic Thin Film Transistors OTFT)以其工艺简单,成本低廉及柔韧性良好等优势,受到人们日益重视和广泛的研究,逐步成为下一代显示技术的核心。本综述根据制备方法的不同,主要针对真空沉淀此种OTFT器件的制备方法,对高迁移率的P-型有机薄膜晶体管材料的近期进展进行总结和评述。     

Photoconductive and supramolecularly engineered organic field-effect transistors based on fibres from donor-acceptor dyads

We report on the formation of photoconductive self-assembled fibres by solvent induced precipitation of a HBC-PMI donor-acceptor dyad. Kelvin Probe Force Microscopy revealed that upon illumination with white light the surface potential of the fibres shifted to negative values due to a build-up of negative charge. When integrated in a field-effect transistor (FET) configuration, the devices can be turned 'on' much more efficiently using light than conventional bias triggered field-effect, suggesting that these structures could be used for the fabrication of light sensing devices. Such a double gating represents an important step towards bi-functional organic FETs, in which the current through the junction can be modulated both optically (by photoexcitation) and electrically (by gate control).     

Donor-acceptor copolymer based on dioctylporphyrin: Synthesis and application in organic field-effect transistors

A novel alternating D–A copolymer, PPor–BT, with dioctylporphyrin (Por) as a donor unit and 5,6-bis(octyloxy)benzo-2,1,3-thiadiazole (BT) as an acceptor unit, was designed and synthesized by Pd-catalyzed Sonogashira-coupling reaction. The copolymer showed good solubility and film-forming ability. PPor–BT exhibited a broad absorption band from 350 to 950 nm with two peaks centered at 456 and 818 nm corresponding to the Soret band and Q-bands absorption of porphyrin segments, respectively. The employment of electron deficient BT unit to construct donor-acceptor structure observably broadened the absorption spectrum and enhanced the Q-band absorption of the porphyrin-based polymer. The HOMO and LUMO energy levels of the polymer are ?5.06 eV and ?3.63 eV, respectively. The solution-processed organic field-effect transistors (OFETs) were fabricated with bottom gate/top-contact geometry. The mobility of PPor–BT based OFEFs reached 4.3 × 10^?5 cm² V^?1 s^?1 with an on/off current ratio of 10⁴. This mobility is among the highest values for porphyrin-based polymers.     

Chemical and engineering approaches to enable organic field-effect transistors for electronic skin applications

Skin is the body's largest organ and is responsible for the transduction of a vast amount of information. This conformable material simultaneously collects signals from external stimuli that translate into information such as pressure, pain, and temperature. The development of an electronic material, inspired by the complexity of this organ is a tremendous, unrealized engineering challenge. However, the advent of carbon-based electronics may offer a potential solution to this long-standing problem. In this Account, we describe the use of an organic field-effect transistor (OFET) architecture to transduce mechanical and chemical stimuli into electrical signals. In developing this mimic of human skin, we thought of the sensory elements of the OFET as analogous to the various layers and constituents of skin. In this fashion, each layer of the OFET can be optimized to carry out a specific recognition function. The separation of multimodal sensing among the components of the OFET may be considered a "divide and conquer" approach, where the electronic skin (e-skin) can take advantage of the optimized chemistry and materials properties of each layer. This design of a novel microstructured gate dielectric has led to unprecedented sensitivity for tactile pressure events. Typically, pressure-sensitive components within electronic configurations have suffered from a lack of sensitivity or long mechanical relaxation times often associated with elastomeric materials. Within our method, these components are directly compatible with OFETs and have achieved the highest reported sensitivity to date. Moreover, the tactile sensors operate on a time scale comparable with human skin, making them ideal candidates for integration as synthetic skin devices. The methodology is compatible with large-scale fabrication and employs simple, commercially available elastomers. The design of materials within the semiconductor layer has led to the incorporation of selectivity and sensitivity within gas-sensing devices and has enabled stable sensor operation within aqueous media. Furthermore, careful tuning of the chemical composition of the dielectric layer has provided a means to operate the sensor in real time within an aqueous environment and without the need for encapsulation layers. The integration of such devices as electronic mimics of skin will require the incorporation of biocompatible or biodegradable components. Toward this goal, OFETs may be fabricated with >99% biodegradable components by weight, and the devices are robust and stable, even in aqueous environments. Collectively, progress to date suggests that OFETs may be integrated within a single substrate to function as an electronic mimic of human skin, which could enable a large range of sensing-related applications from novel prosthetics to robotic surgery.     

Thermal and mechanical behavior of flexible polyurethane‐molded plastic films and water‐blown foams with epoxidized soybean oil

Water‐blown flexible polyurethane foams and molded plastic films were made by replacing 0 to 50% of Voranol® 4701 in the B‐side of foam and plastic film formulation by epoxidized soybean oil (ESBO). Physical properties of foams including density, 50% compression force deflection (CFD), 50% constant deflection compression (CDC), and resilience were determined. A dynamic mechanical spectrometer (DMS) and a differential scanning calorimeter (DSC) were used to characterize the hard segment (HS) and soft segment (SS) ratio and thermal properties of plastic. Various functional groups in both flexible polyurethane foam and plastic film were characterized using Fourier transform‐infrared spectroscopy with attenuated total reflectance (FTIR‐ATR). When increasing the ESBO content, both density and 50% CFD of water‐blown polyurethane foams decreased first, then increased. On the other hand, the 50% CDC and resilience of foams showed a sharp increase and decrease, respectively. When increasing the ESBO content, the peak of tan δ in DMS analysis and Δc_p in DSC analysis of plastic films both decreased indicating the hard segment increased and the soft segment decreased in plastic film, respectively. The FTIR‐ATR results also show the hydrogen‐bonded urethane group increased in plastic films with increasing ESBO content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A simple PAN-based fabrication method for microstructured carbon electrodes for organic field-effect transistors

Facile and efficient fabrication of polyacrylonitrile (PAN)-based conductive graphitic carbon microstructures (GCMs) and their application to the electrodes of organic field-effect transistors (OFETs) is described. The PAN thin films spin-coated on a SiO₂-deposited Si wafer was irradiated through a pattern mask with 150 keV H⁺ ions at various fluences, and subsequently developed to form PAN microstructures. The resulting PAN microstructures were carbonized at various temperatures to create the GCMs. The analytical results revealed that the optimized fluence and carbonization temperature for well-defined GCMs was 3 × 10¹⁵ ions cm⁻² and 100 °C, respectively, and that the resulting GCMs created at the optimized condition exhibited a greatly low surface roughness of 0.36 nm, a good electrical conductivity of about 600 S cm⁻¹, and a high work function of 5.11 eV. Noticeably, the GCM electrodes-based p-type OFET showed a comparable performance to that of the gold electrode-based one, demonstrating that the practical use of GCMs as cheap electrodes to replace expensive metallic ones for organic electronic devices.     

Effect of UV/ozone treatment on polystyrene dielectric and its application on organic field-effect transistors

The influence of UV/ozone treatment on the property of polystyrene (PS) dielectric surface was investigated, and pentacene organic field-effect transistors (OFETs) based on the treated dielectric was fabricated. The dielectric and pentacene active layers were characterized by atomic force microscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The results showed that, at short UVO exposure time (<10 s), the chemical composition of PS dielectric surface remained the same. While at long UVO exposure time (>60 s), new chemical groups, including alcohol/ether, carbonyl, and carboxyl/ester groups, were formed. By adjusting the UVO exposure time to 5 s, the hole mobility of the OFETs increased to 0.52 cm²/Vs, and the threshold voltage was positively shifted to -12 V. While the time of UVO treatment exceeded 30 s, the mobility started to shrink, and the off-current was enlarged. These results indicate that, as a simple surface treatment method, UVO treatment could quantitatively modulate the property of PS dielectric surface by controlling the exposure time, and thus, pioneered a new way to modulate the characteristics of organic electronic devices.     

Catalytically enhanced organic transistors for in vitro toxicology monitoring through hydrogel entrapment of enzymes

The regulation of cell metabolism is important for cell function and viability. In the presence of toxic compounds or pathogens, cell metabolism can change drastically because of excess stress on the cell. The monitoring of key metabolites, such as glucose and lactate, can provide insight into cellular function and can be used as a tool for toxicology studies. The development of enzymatic sensors based on organic electrochemical transistors (OECTs) was demonstrated in this study through the immobilization of enzymes in a photocrosslinkable hydrogel, which was, in turn, tethered to the platinum‐modified gate of a planar OECT. The resulting sensors exhibited high stability, sensitivity, and selectivity. The sensing of relevant metabolites in complex media collected from live kidney epithelial cells was performed. As a proof of the principle, the monitoring of glucose and lactate was also performed from cells treated with cisplatin, a known nephrotoxicant. The glucose and lactate monitoring show that the metabolism of cells was significantly altered by the presence of cisplatin. These findings support the monitoring of cell metabolism as a good approach for toxicology studies. They also illustrate the need for the development of enzymatic sensors that can be used in situ to monitor cell viability and function. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44483.