New light stabilizer for coextruded polycarbonate sheet

Weatherable polycarbonate sheet can be produced by coextruding a cap layer containing a UV absorber over a minimally stabilized bulk layer. A new UV absorber based on hydroxyphenyltriazine chemistry has been developed that is especially suited to this application. The product provides superior long term weatherability because of its strong UV absorbance and its excellent photostability. It is also relatively nonvolatile and has only a minimal effect on melt viscosity.     

透明PP片材专用树脂的研制

以均聚聚丙烯(PP)为基础树脂,通过加入成核剂生产透明PP片材专用树脂。探讨了成核剂的加入量及片材加工温度对片材透明性能的影响,确定PP片材最佳加工温度为230℃。成核剂的加入使PP的结晶度由 44．1％提高到51．4％,结晶温度、熔点等均有不同程度的提高。     

Diffusional characteristics of coextruded linear low-density polyethylenes prepared from different conditions of processing

The permeability and diffusivity of oxygen, carbon dioxide, nitrogen, and helium have been obtained for a range of linear low density polyethylene (LLDPE) films prepared from the same raw materials but with different processing conditions. The measurements were carried out by means of a permeation technique over the temperature interval where the α-relaxation processes were observed in earlier studies. The temperature dependence of the permeability and diffusion coefficients of gases shows 2 well-differentiated regions in all films. The break temperature of these regions is approximately located at the same temperature as the α-relaxation takes place. Both the permeability and their temperature dependence do not show a noticeable influence on the processing conditions. The effect of processing conditions on the diffusivity seems to be more complex. Differences are observed for different films in the diffusion coefficients, in the case of oxygen, and in their change with the temperature, which is particularly marked in the case of carbon dioxide. Fujita's free volume model has been applied to diffusivity data in order to study the influence of films microstructure in gas permeation properties through them. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 23–37, 1998     

Recycling of high impact polystyrene in coextruded sheet: Influence of the number of processing cycles on the microstructure and macroscopic properties

High impact polystyrene(HIPS) was repeatedly coextruded at 220°C, maintaining a constant composition of 70 wt% of virgin HIPS and 30 wt% of recycled HIPS. The gel content (GC), grafting degree (GD), swell index (SI), morphology of the rubber phase, and average molecular weight of the polystyrene (PS) matrix ( _w) were characterized after each processing cycle. The effect of these parameters on the melt flow index (MFI), the shear viscosity (η), the power law index (n), the Izod impact, and the stress at break were evaluated. The results demonstrated that the rheological properties changed with the number of processing cycles, e.g. the MFI decreased in the first cycle from 2.8 to 1.7 g/10 min, while from the second to the sixth cycle increased to 3.4 ± 0.2 g/10 min. The power law index increased from n = 0.29, after the first processing cycle, to n = 0.34 in the sixth cycle. The changes in MFI and n were attributed to changes in the physical structure of the rubber phase and to chain scissions in the PS matrix, caused by the recycling. Finally, the impact strength decreased with the increasing number of processing cycles, while the tensile stress at break remained constant. POLYM. ENG. SCI., 46:1698–1705, 2006. © 2006 Society of Plastics Engineers     

High pressure and high temperature treatment of chemical vapor deposited polycrystalline diamond: From opaque to transparent

The enhanced optical properties of chemical vapor deposited (CVD) diamond have been pursued in academia and industry for many applications. However, the barrier of CVD technology limits the application field of diamond. Herein, the performance of CVD polycrystalline diamond thick films was improved by high-pressure and high-temperature (HPHT) treatment. The microstructures of CVD polycrystalline diamond films before and after HPHT treatments were thoroughly examined using optical microscope, UV–visible and infrared absorption, Raman spectroscopy, scanning electron microscope (SEM) and transmission electron microscope (TEM). It is found that the transparency of the CVD samples at 10 GPa increases dramatically with processing temperatures, from the original opacity to almost full optical transparency. Through spectroscopic and microstructural analyses, the modification mechanism of CVD polycrystalline diamond under HPHT conditions is proposed. The results show that the HPHT treatment can significantly enhance the optical properties of the starting CVD polycrystalline diamond films.     

鑫泉塑机成功研制PVC软质透明片材生产线

一种可生产PVC软质透明片材的塑机设备,最近在青岛鑫泉塑料机械有限公司研制成功。青岛鑫泉研发的PVC软质透明片材生产线结构紧凑,性能稳定,具有塑化均匀、产量高、使用寿命长等优点,确保了PVC软质透明片材的连续高效挤出,大大降低了用户的生产成本。     

Evidences for flow‐assisted interfacial reaction in coextruded PA6/PP/PA6 films

We present an investigation of the progressive building of copolymer layers formed by chemical reaction at interfaces in multilayer coextruded polymer films. Analyzing the surface density of copolymers in the final films, we show that the interface always remains under‐saturated in copolymers, even for coextrusion parameters such that the time open to the interfacial chemical reaction is well above the time necessary to reach saturation without flow. Based on a numerical analysis of the flow all along the coextrusion line, we show that this under‐saturation of the interface, which may strongly affect the final adhesion between the different polymers, results from a competition between the interfacial chemical reaction and the dilution of yet formed copolymers in all the zones of the coextrusion line where surface of interface is increased, due to convergent, divergent or elongational flow. We also show that the coupling between flow and reaction kinetics needs be taken into account to control the final surface density of copolymers and precisely optimize the interfacial properties, through an optimization of the coextrusion parameters POLYM. ENG. SCI., 59:E44–E50, 2019. © 2018 Society of Plastics Engineers     

Highly transparent low resistance ATO/AgNWs/ATO flexible transparent conductive thin films

Indium-free flexible transparent conductive thin films (TCFs) composed of silver nanowire (AgNW) networks and Sb doped SnO₂ (ATO) layers were prepared on polyethylene terephthalate (PET) substrates. The ATO layers were deposited via radio frequency (RF) magnetron sputtering at room temperature. The AgNWs were achieved via a modified polyol reduction method and embedded between the ATO layers. The effects of AgNW networks and ATO layers on electrical and optical properties of the ATO/AgNWs/ATO flexible tri-layer thin films are investigated. The ATO layers can improve the optical transmittance and reduce the resistivity of tri-layers, and the corresponding mechanisms are proposed. Typically, an ATO/AgNWs/ATO flexible tri-layers show a high figure of merit value (30.06 × 10^-3 Ω^-1) with a low sheet resistance of 7.1 Ω/sq. and a high transmittance of 85.7%. Meanwhile, the tri-layers present excellent mechanical flexibility, and the ATO layers acted as the protecting layers improve the adhesive and environmental stability at high temperature and humidity for the ATO/AgNWs/ATO flexible tri-layers. These results indicate that ATO/AgNWs/ATO flexible tri-layer thin films can be useful for the fabrication of wearable electronic devices.     

Controlling interfacial instabilities in PP/EVOH coextruded multilayer films through the surface density of interfacial copolymers

Coextruded polypropylene/tie/ethylene vinyl alcohol/tie/polypropylene (PP/tie/EVOH/tie/PP) films often exhibit optical defects which appear as randomly distributed scattering objects, in the submillimeter range. These defects may strongly affect the film transparency and prevent their practical use in packaging. Based on an objective optical test aimed at quantifying the film transparency, and on a systematic analysis, through optical microscopy, of transverse cuts of films obtained in various coextrusion conditions, the nature of the defects could be identified as resulting from a modulation of the thickness of the inner ethylene vinyl alcohol (EVOH) layer, with no variation in the overall thickness of the multilayer films. Thanks to a recently developed method to dose the surface density of interfacial copolymers, a clear correlation between the amplitude of the thickness modulation of the inner EVOH layer and the density of copolymer molecules formed in situ at the EVOH/tie layer interface during the coextrusion process was established. These results open the way to a better design of tie layers composition to avoid these kinds of defects.     

压延存料对PVC透明片材质量影响的探讨

根据G.Ardichuili的压延理论,分析了聚氯乙烯压延加工过程中物料的流变行为,指出存料是影响压延透明片材的厚度均匀性、外观质量的重要因素之一。根据产品的厚度、柔软率,正确控制辊隙存料量是提高压延透明片材质量的重要手段之一。     

板料成形中的载荷及位移边界条件的处理

现有的通用有限元分析软件在其前处理时对载荷及位移边界条件都是人工添加的 ,而产品工艺分析 ( CAPP)中已包含了载荷及位移边界条件中的信息。因此 ,若能将产品工艺分析和有限元分析集成 ,即可将工艺分析的结果直接引入有限元分析中而不必再次进行边界处理。本文结合封头成形工艺 ,提出了板料整体成形 CAPP中的特征造型与有限元前处理集成的原理和方法。     

Biaxially stretched in comparison with conventionally blown coextruded composite plastic films

Multilayer composite films consisting of polyolefins, either polypropylene, linear low density or medium density polyethylene, a thin adhesive layer, and a polyamide in various ratios were prepared using two basically different processes. The first, a conventional blown film process in which the extrudate is stretched while in the molten state; and the second, a two-stage process in which the quenched extrudate is stretched at a temperature below the polymers' melting point. The films so prepared, having identical composition and similar extents of stretching, were compared on the basis of their tensile properties, thermoelastic shrinkage, oxygen transmission rate, and thermal behavior. The effects of stretching temperature, rate, and extent on the behavior of the composite films and control single layer films were investigated. The stretching temperature was found to be the dominating single process parameter in determining the films' behavior. The overall performance including tensile properties, barrier, and shrink properties of the “cold” stretched films was found markedly superior to that of the conventionally blown films. The stretched composite films possess physical properties that cannot be attained by the conventional process.     

Influence of laminate thickness reduction on the deformation mechanism of coextruded multilayered PC/PMMA films

The influence of the morphology of multilayered composites of poly(methyl‐methacrylate) (PMMA) and polycarbonate (PC) fabricated by layer multiplying coextrusion technique on their mechanical and especially their micromechanical deformation behavior was investigated. Electron microscopic studies revealed that the PC/PMMA multilayered composites have a well‐oriented, uniform, and continuous layered architecture. With decreasing layer thickness of each polymer in the composite, the elongation at break of the films was found to increase significantly which was correlated with a transition from a two‐component behavior (for single‐layer thickness of ≥8 μm) to an one‐component behavior (for single‐layer thickness of ≤250 nm). Rheo‐optical measurements using FTIR spectroscopy revealed that the molecular orientation during stretching of the PMMA phase remains unchanged for all the investigated films, whereas the PC orientation function decreases with decreasing layer thickness. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013