Static measurements of refractive index increments at 633 nm with a modified refractive index detector

Summary A R 401 Waters Assoc. differential refractometer has been modified to obtain the variation of refractive index increments, dn/dc, of polymer solutions at 633 nm. The introduced modifications were in the sample injection system and in the light source. The performance of the modified refractometer both with aqueous and organic solutions is analyzed. In order to localize a conformational transition in lysozyme, the dependence of dn/dc on temperature for lysozyme solutions in phosphate buffer is studied. Similarly, (dn/dc)_k values for the ternary n-alkane/butanone/poly(dimethyl siloxane) systems over the whole composition range of the binary solvent mixtures are evaluated.     

影响聚酯瓶透明性的因素及控制

介绍了影响聚酯瓶透明性的几种因素,其中包括PET树脂原料、原料的湿度、特性粘数、瓶坯厚度及冷却速度,并提出了相应的改善方法。     

How the morphology of poly (vinyl chloride) compounds affects toughness and weatherability

Suspension polymerized poly (vinyl chloride) (PVC) is made up of 150 μm grains. Within these grains are 2 μm primary particles which apparently become the flow units under low melt temperature (175°C) extrusion conditions. The 2 μm particles are visible by light transmission microscopy by shearing the extruded product between glass slides after swelling in acetone or by electron transmission microscopy of ultrathin microtomed samples. This product, made up of 2 μm flow units, is brittle and has poor toughness retention upon weathering. At higher melt temperatures (185–190°C), agglomeration of the 2 μm particles occurs, giving a rough surface but tougher product. At higher melt temperatures, a continuous melt occurs, leading to a smooth surface and tough product with excellent toughness retention upon weathering.     

Effect of modifier characteristics on toughness of poly(vinyl chloride)

The effects of the mechanical properties of an acrylic graft copolymer and a silicone/acrylic composite rubber graft copolymer on the toughening of poly(vinyl chloride) (PVC) are examined. In the experiment for improvement of impact resistance of PVC, toughness of the blend polymer of a silicone/acrylic composite rubber graft copolymer is improved remarkably. The effect is attributed to the suppression of stress concentration below the fibril strength of the polymer alloy effectively by releasing the constraint of strain resulting from easy void formation at low stress. © 1996 John Wiley & Sons, Inc.     

MBS对CPVC凝胶化的影响及CPVC/MBS共混物性能的研究

采用差示扫描量热仪和HAAKE流变仪研究了甲基丙烯酸甲酯-丁二烯-苯乙烯共聚物(MBS)对氯化聚氯乙烯（CPVC）凝胶化性能及流变性能的影响,并对CPVC/MBS共混物的力学性能、耐热性能、微观形貌进行了系统研究。结果表明,MBS能改善CPVC的加工性能。随着MBS含量的增加,共混物的凝胶化度得到极大的提高,塑化时间明显缩短,平衡扭矩不断上升,平衡温度大幅上升。MBS用量为6份时,CPVC/MBS共混物的综合性能最佳。     

Oxygen permeation resistance of polyethylene,polyethylene/ethylene vinyl alcohol copolymer,polyethylene/modified ethylene vinyl alcohol copolymer,and polyethylene/modified polyamide–ethylene vinyl alcohol copolymer bottles

The oxygen permeation resistance of polyethylene (PE), polyethylene/ethylene vinyl alcohol copolymer (PE/EVOH), polyethylene/modified ethylene vinyl alcohol copolymer (PE/MEVOH), and polyethylene/modified polyamide–ethylene vinyl alcohol copolymer (PE/MPAEVOH) bottles was investigated. The oxygen permeation resistance improved significantly after the blending of ethylene vinyl alcohol copolymer (EVOH) barrier resins in PE matrices during blow molding; less demarcated EVOH laminas were found on the fracture surfaces of the PE/EVOH bottles. Surprisingly, the oxygen permeation resistance of the PE/MEVOH bottles decreased significantly, although more clearly defined modified ethylene vinyl alcohol copolymer (MEVOH) laminas were found for the PE/MEVOH bottles as the compatibilizer precursor contents present in the MEVOH resins increased. In contrast, after the blending of modified polyamide (MPA) in EVOH resins, more demarcated modified polyamide–ethylene vinyl alcohol copolymer (MPAEVOH) laminar structures were observed in the PE/MPAEVOH bottles as the MPA contents present in the MPAEVOH resins increased. In fact, with proper MPAEVOH compositions, the oxygen permeation resistance of the PE/MPAEVOH bottles was even better than that of the PE/EVOH bottles. These interesting oxygen barrier and morphological properties of the PE, PE/EVOH, PE/MEVOH, and PE/MPAEVOH bottles were investigated in terms of the free volumes, barrier properties, and molecular interactions in the amorphous‐phase structures of the barrier resins present in their corresponding bottles. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2528–2537, 2004     

Preparation and refractive index characterization of chalcogenide glasses with gradient refractive index

Infrared gradient refractive index (GRIN) lenses have great application value and potential in multispectral imaging systems. This study reports various chalcogenide axial GRIN glasses prepared using the hot-pressing diffusion method. It is worth noting that the S4–S60 GRIN sample has a difference in refractive index (RI) Δn of greater than 0.3 and a diffusion depth of about 5 mm, which is the deepest diffusion depth reported in chalcogenide glass to date. In addition, the linear portion in the profile of the GRIN sample has a RI difference of 0.15 and a thickness of 1.2 mm. The effects of the temperature, concentration difference, and diffusion time on the sample diffusion process are discussed. The dispersion properties of the GRIN samples were further calculated, providing a new option for correcting chromatic aberrations in optical systems. In addition, a method for the indirect nondestructive characterization of sample RI using the Raman intensity ratio is proposed, and the reliability of the method is verified by practical experiments, which is convenient for the subsequent measurement of the GRIN profile.     

White spirit permeation resistance of polyethylene,polyethylene/modified polyamide,and polyethylene/blends of modified polyamide and ethylene vinyl alcohol bottles

The main objective of this study was to investigate the barrier properties of polyethylene (PE), PE/modified polyamide (MPA), and PE/blends of modified polyamide and ethylene vinyl alcohol (MPAEVOH) bottles against white spirit permeation. After MPAEVOH barrier resins were blended with PE, the resistance of the PE/MPAEVOH bottles against white spirit permeation was significantly improved compared to the PE bottle. Surprisingly, with proper compositions of MPAEVOH resins, the white spirit permeation resistance of PE/MPAEVOH bottles at 40°C improved by more than 3000 times compared to the PE bottle, wherein the best permeation resistance (4200 times barrier improvement) of the PE/MPAEVOH bottles was found as the weight ratio of MPA : EVOH reached 4:1. These interesting permeation properties of PE/MPAEVOH bottles were investigated in terms of the barrier and free‐volume properties of the base resins and their corresponding morphologies in blow‐molded bottles. POLYM. ENG. SCI. 45:25–32, 2005. © 2004 Society of Plastics Engineers.     

Orientation and crystalline morphology of blow molded polyethylene bottles

A study was carried out of the development of orientation during processing of conventional blow molded bottles made from low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE). The level of molecular orientation was found to be relatively low in all of the polyethylene bottles examined; it increased with increasing inflation pressure and decreasing extrusion temperature. Pole figures for the HDPE bottles indicated a slight a-axis orientation toward the circumferential direction of the bottle. The b-axes, which correspond to the lamellar growth direction, tend to be parallel to the bottle thickness direction. A comparison was made of the structure developed in blow molded bottles and blown films. The results for both films and bottles indicate that crystallization during processing involves both an increase in level of molecular orientation and an increased tendency toward biaxiality. Based on pole figures and small angle X-ray scattering patterns, a morphological model for HDPE blow molded bottles is proposed.     

Fracture toughness of epoxy resins modified with polyethersulfone: Influence of stoichiometry on the morphology of the mixtures

Toughened mixtures containing 15 wt % polyethersulfone were made with diglycicdyl ether of bisphenol-A resin and 4,4′-diaminodiphenylmethane curing agent, with amine/epoxy group stoichiometric ratios varying from 0.6 to 1.5. Fracture behavior of the modified mixtures has been investigated as a function of the stoichiometry in the matrix. Morphology has been analyzed by transmission and scanning electron microscopy. The increase of amine content in the matrix results in a further increased fracture toughness. This behavior has been related to the changes on the ductility of the matrix upon stoichiometric ratio, but also to the changes on microstructural features of the modified mixtures as stoichiometric amine/epoxy group ratio increased. These morphological changes have been interpreted in terms of spinodal decomposition during curing of the epoxy matrix. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 183–191, 1998     

Effect of molecular weight on the refractive index increment of polystyrenes in solution

The variation of refractive index increment $\text{d}\text{n}\text{d}\text{c}$ with molecular weight has been studied using solutions of monodisperse polystyrenes (2000<M_w<4×10⁶) in benzene. The results are in good agreement with those obtained by several authors using other systems.We have shown that the linear relationship:

$\text{d}\text{n}\text{d}\text{c}\text{=}\text{d}\text{n}\text{d}\text{c}{}_{\mathrm{m}}\text{+}\text{K″}\text{Mn}$

where $\text{(}\text{d}\text{n}\text{d}\text{c)}{}_{\mathrm{m}}$ is the refractive index increment of the repeating unit and K″ a constant, holds only for low molecular weights. With the assumption of volume additivity, we have estimated quantitatively the linear portion of the curve, $\text{d}\text{n}\text{d}\text{c}\text{=f(}\text{1}\text{M}\text{)}$, observed for molecular weights below 20 000 as a function of polymer composition. Beyond this limit, the increase of $\text{d}\text{n}\text{d}\text{c}$ with molecular weight may be probably related to segment-segment interactions within the coil.     

Effect of thermoplastic veils on interlaminar fracture toughness of a glass fiber/vinyl ester composite

The effects of two thermoplastic micro‐veils, polyamide (PA) and polyethylene terephthalate (PET) veil, on the interlaminar fracture toughness of a glass fiber/vinyl ester (GF/VE) composite were investigated. The veils incorporated into the composite as interleaving materials were first characterized via scanning electron microscopy (SEM), differential scanning calorimetry (DSC), contact angle and tensile testing in order determine the best candidate as toughening agent for the GF/VE composite. Composite laminates were manufactured by vacuum‐assisted resin infusion process. Double cantilever beam (DCB) testing was performed to investigate the Mode I type interlaminar fracture toughness of the composites, which was characterized by critical strain energy release rate (G _IC). An increased G _IC was obtained by incorporating the PA veil, but it changed negligibly by the addition of the PET veil. The analysis of the composites fracture surface via SEM revealed increased fiber bridging between adjacent plies in the case of PA veil interleaved composites which played a key role in enhancing the Mode I interlaminar fracture toughness. However, the PET veil present in the interlaminar region did not take part in any energy absorbing mechanism during the delamination, thus keeping the G _IC of the composite unaltered. POLYM. COMPOS., 38:2501–2508, 2017. © 2015 Society of Plastics Engineers     

Effect of hybridization on the mode II fracture toughness properties of flax/vinyl ester composites

In this study, flax fiber reinforced and flax/basalt hybridized vinyl ester composites were produced and their interlaminar fracture toughness (mode II) behavior was investigated using the three‐point bend end‐notched flexural (3ENF) testing. From the results, the average of the maximum values for each group of specimen obtained for critical strain energy release rate G _IIC and stress intensity factor K _II for flax/vinyl ester specimens were 1,940 J/m² and 134 kPam^0.5. Similarly, G _IIC and K _II values recorded for hybridized specimens were 2,173 J/m² and 178 kPam^0.5, respectively. The results for the flax/basalt hybridized composites exhibited an improved fracture toughness behavior compared to flax/vinyl ester composites without hybridization. The cohesive zone modeling (CZM) was also used to predict the delamination crack propagation in mode‐II in laminated composite structures. After the experimental study, the 3ENF specimens were modeled and simulated using ANSYS. The CZM/FEA results were in reasonable agreement with the experimental results. POLYM. COMPOS., 38:1732–1740, 2017. © 2015 Society of Plastics Engineers     

Effect on the toughness and adhesion properties of epoxy resin modified with silyl-crosslinked urethane microsphere

In order to give a toughness and improve adhesion properties of the cured epoxy system, modified epoxy resins, which have pre-reacted urethane microspheres formed using dynamic vulcanization method in liquid diglycidylether of bisphenol A, were prepared. It was found that the size of the particles decreased to sub-micro order with increase in solubility of urethane oligomers in epoxy resin, and coefficient of variance in the particle size distribution resulted in less than 15%. Fracture energy G_1c of the cured system was highly improved. Lap shear strength and peel strength were also improved. These mechanical and adhesion properties do not depend on any curing condition of epoxy resin because of the existing stable particles in the epoxy resin before curing.     

Effect of solvent balance on the surface properties of poly(vinyl chloride)

Films of poly(vinyl chloride) have been cast from solutions of varying thermodynamic quality and the film properties studied by inverse phase gas chromatography. The solvents included tetrahydrofuran, cyclohexanone, and mixtures of toluene with both tetrahydrofuran and cyclohexanone. The solvent composition was followed during evaporation and film formation for the mixed solvents, and it was shown that the slower evaporating solvent component has the greatest effect on the surface properties of the films. The porosity of the polymer film surfaces is interpreted in terms of the mobility of the polymer chains during film formation. At high concentrations, polymer chain–polymer chain interactions become stronger when thermodynamically less powerful solvents are used or are last to leave during film formation; therefore, the solvent balance has a critical influence on the film surface properties. Annealing the poly(vinyl chloride) above the glass transition temperature reduces the surface porosity of the cast polymer.     

Impact fracture toughness and morphology of polypropylene nanocomposites

The nanometer calcium carbonate (nano-CaCO₃)-filled polypropylene (PP) composites were prepared using a twin-screw extruder, and the filler particle surface was pretreated, respectively, with fat acid (SI) and titanate coupling agent (SII) in this article. The notched and unnotched impact fracture properties were measured at room temperature by means of a Charpy impact instrument to identify the effects of the surface treatment and the filler concentration on the impact fracture properties. The results showed that the V-notched and U-notched impact strength slightly increased with an addition of the nano-particle volume fraction (ϕ _f) for both two nanocomposites. When ϕ _f was more than 10%, the V-notched impact strength of the system SII was obviously greater than that of the system SI, and the effect of surface treatment of the nanometer particles on the U-notched impact strength is insignificant. Furthermore, the impact fracture surface was observed by means of scanning electron microscopy to understand the relationship between the interfacial morphological structure and the impact fracture toughness of the PP nanocomposites.     

叔碳酸乙烯酯改性醋丙乳液的制备与性能研究

采用半连续种子乳液聚合,以丙烯酸丁酯(BA)、甲基丙烯酸甲酯(MMA)、乙酸乙烯酯(VAc)为主单体,丙烯酸(AA)为功能单体,叔碳酸乙烯酯(VeoVa10)为改性单体,合成了核壳型丙烯酸酯乳液。探讨了聚合温度、乳化剂、引发剂及功能单体与乳液性能的关系。通过单因素实验探讨了乳化剂用量、配比,改性单体用量等与乳液性能的关系。FT-IR和DSC测试结果表明,各单体之间发生了自由基共聚反应,乳液粒子为核壳结构。     

吹塑工艺对改性共聚尼龙/高密度聚乙烯中空吹塑瓶阻隔性能的影响

将由乙烯-丙烯酸酯-马来酸酐共聚物(CP)与共聚尼龙(PA-54)在双螺杆挤出机中反应共混制得的改性共聚尼龙(MCOPA)与高密度聚乙烯(HDPE)通过层状共混工艺制备高阻隔性中空吹塑瓶。研究表明,吹塑工艺对阻隔瓶的阻隔性能具有很大的影响。     

Barrier resistance of polyethylene,polyethylene/modified polyamide,and polyethylene/blends of modified polyamide and ethylene vinyl alcohol bottles against permeation of polar and nonpolar mixed solvents

The main objective of this study is to investigate the barrier properties and mechanisms of polyethylene (PE), PE/modified polyamide (MPA), and PE/blends of MPA and ethylene vinyl alcohol copolymer (MPAEVOH) bottles against permeation of polar/nonpolar (acetone/white spirit) mixed solvents. The mixed solvent permeation resistance improves dramatically after blending MPA and MPAEVOH barrier resins in PE matrices during blow molding. By using the proper MPAEVOH compositions, the white spirit permeation rate of PE/MPAEVOH bottles at 40°C can be about 145 times slower than that of the PE bottle specimen; however, it is still 2.5 times faster than that of the PE/MPA bottles. In contrast, the rate of polar acetone solvent permeation through the PE bottle is much slower than that of white spirit and only slightly faster than that through the PE/MPA and PE/MPAEVOH bottle specimens. In contrast, the permeation rates of acetone/white spirit mixed solvents into PE/MPA bottles are at least 20–60 times faster than the summation permeation rates calculated using the simple mixing rule when the acetone contents in the mixed solvents are between 10 and 70 wt %. It is somewhat interesting that, after blending the proper amounts of EVOH in MPA, the mixed solvent permeation rates of PE/MPAEVOH bottles are dramatically reduced and are very close to the summation permeation rates calculated using the simple mixing rule when the acetone contents are in the particular “window” range. These interesting barrier properties of PE/MPA and PE/MPAEVOH bottle specimens were investigated in terms of the free volumes, barrier properties, molecular interactions in the amorphous phases of the barrier resins, and their resulting morphological structures that present in their corresponding bottles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1333–1344, 2005