Effect of water absorption on physical properties of high nitrile barrier polymers

Water absorption studies were made on a series of high nitrile barrier polymers, as a function of polymer composition, rubber content, temperature, orientation and relative humidity. Results indicate that absorbed water has a great influence on both mechanical and thermal properties of the polymer. Absorbed water in high nitrile polymers causes a large decrease in the glass transition temperature and yield stress. These effects are found to depend on polymer composition, amount of absorbed water, and degree of orientation. The significance of these results is discussed in relation to end-use properties of the polymer.     

Thermal degradation of high nitrile barrier polymers

Effects of absorbed moisture on degradation behavior of high nitrile barrier polymers were monitored using thermogravimetric analysis techniques. Non-modified and 10 percent rubber modified samples were heated isothermally at nitrile processing temperatures (200°C to 240°C) in air and nitrogen environments. Degradation was evaluated in terms of weight loss as a function of heating time and sample coloration. It was determined that complete removal of moisture, as well as high moisture concentration, contribute to increased degradation at the temperatures evaluated. Moisture levels in the range of 0.15 to 0.5 percent were found to minimize degradation. Heating environment, time, temperature, and rubber modification were also found to influence thermal stability.     

Synthesis of biodegradable and flexible,polylactic acid based,thermoplastic polyurethane with high gas barrier properties

Polylactic acid (PLA) has the beneficial properties of good mechanical strength, biodegradability and biocompatibility, and these properties make it suitable for use as an environmentally friendly packaging material. However, its use has been limited by its brittleness and poor stability. In this work, we successfully developed an efficient synthesis scheme to improve the mechanical properties, flexibility and gas barrier properties of PLA‐based polymers. Four different PLA‐based thermoplastic polyurethane (PLAPU) polymers were synthesized through the reaction of PLA diol with hexamethylene diisocyanate, followed by chain extension with polycaprolactone (PCL) diol. The relative compositions of the hard PLA and the soft PCL diols in the PLAPU polymers were controlled systematically to optimize the physical properties of the polymers. For example, increasing the content of PCL resulted in higher molecular weight PLAPU polymers that had increased tensile strengths and elongations at break, but their moduli were decreased. At the optimized PLA:PCL ratio of 1:3, the PLAPU polymer had an excellent elongation at break of 1053% with a relatively high Young's modulus of 51.8 MPa. In addition, the gas barrier properties of the PLAPUs were significantly enhanced depending on the molecular weight and PCL content of the polymers. To demonstrate the feasibility of using PLAPU polymers for biodegradable packaging materials, hydrolytic degradation tests were performed in phosphate buffer solution, and the PLAPU polymers were degraded gradually at rates that depended on the content of PCL in the polymers. This optimized PLAPU polymer exhibited excellent flexibility and gas barrier property, as well as high elongation, demonstrating its potential utility as packaging materials. © 2013 Society of Chemical Industry     

Preparation and properties of gas barrier resin/rubber nanolaminated composites

An extremely high gas barrier resin was highly oriented and uniformly distributed in a rubber matrix layer by layer by the micro‐layer coextrusion technology and a special composite laminating device. The resulting composite had excellent gas barrier properties because of its alternating multilayer structure. Experimental tire samples were prepared and tested for high‐speed, endurance, and pressure performance. The results showed that because the barrier resin was evenly dispersed in the rubber matrix, the tire inner liner made of the composite showed excellent fatigue resistance and gas barrier performance. POLYM. ENG. SCI., 55:190–195, 2015. © 2014 Society of Plastics Engineers     

Prediction of mechanical properties of polymers. Tensile strength of glass-reinforced plastics

Tensile strength data at high and low rates of loading were obtained for a glass-reinforced polyester and a glass-reinforced epoxy. Analysis of the data by a rate method indicated that such a method may be used to predict behavior of polymers from limited test data.     

Prediction of mechanical properties of polymers. Tensile strength of several thermoplastics

Tensile strength data for five thermoplastics [polycarbonate, phenoxy, poly(methyl methacrylate), polyethylene, and ethyl cellulose] are analyzed according to a modified rate equation. The agreement of the test results with the behavior described by the equation is excellent. Treatment of this type may be used to predict behavior of polymers from limited test data.     

Synthesis and properties of poly(ferrocenylsilane) high polymers

Ring-opening polymerization of strained, ring-tilted cyclic ferrocenylsilanes has recently provided access to the first examples of high molecular weight poly(ferrocenylsilanes) [1], which possess backbones of alternating ferrocenyl groups and silicon atoms. In this paper we provide an overview of the progress to date on the synthesis and properties of these unusual polymers.Presented at the XXVIth Silicon Symposium, Indiana University-Purdue University at Indianapolis, March 26–27, 1993.     

Phase transitions,relaxations, and properties of high polymers

Starting with a nondefective bundle of macromolecules (the ideal crystal) one gets a low-defective bundle (the real crystal) by introduction of stable defects (kinks, torsional defects, jogs and folds) which are compatible with the intra- and intermolecular potential. The cooperative statistical treatment of this bundle reveals – under a certain condition – a first order transition, connected with a jump in defect-concentrations. This transition corresponds in most cases to the melting of the polymer, in some polymers (e. g. trans-polybutadiene) it splits up into a solid state transition (large kinkblocks without torsions) and the melt transition (small kinkblocks, torsional defects, jogs and folds). In the case of polyethylene the bundle model has been shown to explain quantitatively the transition data (T_m, ΔH_m, ΔV_m) as well as the expansion coefficient and the compressibility of the melt together with their dependence on static pressure. The calculated short-range order also is in accordance with the X-ray and electron diffraction data. By introduction of cooperatively arranged gauche-areas (for planar molecules) the meander model is established which guarantees the isotropy of the melt. Assuming the bundle diameter (calculated to about 50 Å which is in the range of the observed superstructure in amorphous polymers) to be constant during crystallization a lamellae-structure results in which the meander thickness is determined by the crystallization temperature. This two phase meander model is in accordance with the experiment and implies the key to the understanding of molecular motions in polymers. This will be shown by a quantitative molecular interpretation of the relaxation processes (secondary, main and crystalline relaxation) in a polymer as well as of its deformation behaviour (paraelasticity, plasticity).     

Effect of organoclay on the gas barrier properties of natural rubber nanocomposites

Natural rubber nanocomposites have been prepared with organically modified montmorillonite clay. The nanocomposites have been characterized by X‐ray diffractometry and transmission electron microscopy. The gas‐barrier properties of the nanocomposites have been studied for three different gases viz., oxygen, nitrogen, and CO₂ gases. The natural rubber–organoclay composites exhibit outstanding gas‐barrier properties compared to the neat rubber. Various models have been applied to predict the decrease in permeability in nanocomposites. All other models except Bharadwaj model give low values of calculated aspect ratio. Dynamic mechanical analysis has been carried out to investigate the role of the constrained region on the permeability of the nanocomposites. The permeability decrease of the organoclay nanocomposites is found to have good qualitative correlation with the volume of the constrained region. POLYM. COMPOS.,, 2012. © 2012 Society of Plastics Engineers     

A gelatin/PLA-b-PEG film of excellent gas barrier and mechanical properties

A polylactic acid-polyethylene glycol block copolymer (PLA-b-PEG) was used as an additive to prepare gelatin/PLA-b-PEG blend films for the first time. The PEG molecule block enhanced the compatibility of the PLA molecule block with gelatin, which greatly improved the excellent mechanical and gas barrier properties of the gelatin film. The film contained 5 wt% PLA-b-PEG possessed the highest tensile strength and the highest elastic modulus. When the PLA-b-PEG content further increased to 20 wt%, the tensile strength, elastic modulus and elongation at the break of the blend film were all higher than pure gelatin film, suggesting that the gelatin/PLA-b-PEG blend film was pliable and tough. The blend film possessed not only excellent oxygen barrier property, but also a much-improved water barrier property. The degradation rate of the blend film was elongated controllably by regulating the content of the PLA-b-PEG copolymer. The blend film showed great potential in the application of food packaging.     

Hydrophobic polymers as barrier dispersion coatings

The aim of this study was to evaluate the properties of polymer dispersions prepared from hydrophobic monomers as barrier coatings. These dispersions were produced using a new emulsion polymerization process involving cyclodextrin as a phase‐transport catalyst. Conventional emulsion polymerization techniques are not applicable due to the low water solubility of the monomers, such as lauryl and stearyl (meth)‐acrylates. The experimental polymers showed improvements in water and water vapor barriers, as a result of the incorporation of hydrophobic monomers. The barrier properties could be further improved with functional groups, crosslinking, and chain‐regulating agents, as well as fillers. Grease and water barriers were strongly affected by pinholes, and functional monomers appeared to be effective in enhancing the grease barrier property. Particle morphology, glass transition temperature, and drying affected the performance of these dispersions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1958–1962, 2006     

Transparent,flexible, and high‐strength regenerated cellulose/saponite nanocomposite films with high gas barrier properties

Regenerated cellulose‐saponite nanocomposite films were prepared from LiOH/urea solutions, and exhibited high optical transparency and flexibility. The saponite platelets formed intercalated nanolayered structures in the composites. The longitudinal directions of both the cellulose II crystallites and the saponite platelets were preferentially oriented parallel to the film surface in the composites. The good nanodispersibility and high orientation of the saponite platelets in the composite films resulted in high mechanical strength, high Young's modulus, and good thermal dimensional stabilities, and gas barrier properties in the composites, compared with a reference cellulose film. Moreover, the tensile strength and Young's modulus of the composite film reached 241 MPa and 7.7 GPa, respectively, when a simple drawing process was applied to the wet composite film; this is probably owing to the improvement in the orientation of the cellulose II crystallites and saponite platelets in the composites. The composite films also showed high toughness and ductility. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3168–3174, 2013     

EVOH nanocomposite films with enhanced barrier properties under high humidity conditions

To improve the oxygen and water vapor barrier properties of ethylene vinyl alcohol, EVOH/EFG nanocomposite films under high humidity conditions, we successfully prepared highly exfoliated graphite (EFG) containing a monolayer or a few layers of graphene via rapid heating treatment and ultrasonication as confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), elemental analysis (EA), and nitrogen adsorption–desorption analysis. Six different EVOH/EFG nanocomposite films containing as‐prepared EFG were prepared via a solvent blend method and their physical and barrier properties at different relative humidities were investigated as a function of EFG content. Depending on the EFG content, oxygen transmission rate (OTR) decreased from 3.7 to 0.1 cc/m²/day at dry condition, and the difference in OTR between dry condition and humid condition decreased from 6.5 to 2.3 cc/m²/day. Barrier properties of the EVOH/EFG nanocomposite films were strongly dependent on their chemical structure and morphology. Crystallinity, tortuous path length, and hydrophobicity of EVOH/EFG nanocomposite films were enhanced by the addition of EFG. However, the thermal stability and glass transition temperature of the nanocomposite films were not improved by incorporation of EFG due to the weak interaction between EVOH and EFG. To maximize the performance of EVOH/EFG nanocomposite films, the compatibility of the polymer matrix and fillers needs to be improved. POLYM. COMPOS., 35:644–654, 2014. © 2013 Society of Plastics Engineers     

Renewable eugenol-based functional polymers with self-healing and high temperature resistance properties

A novel small molecule 1,3-bis(eugenyl) glycerol diether is synthesized from renewable eugenol and epichlorohydrin in 60% total yield, and its structure is confirmed by ¹H–NMR spectrum. Then, this small molecule is utilized to prepare oligomer, linear polymer and the corresponding crosslinked polymer (denoted as P ₂ ) by using thiol-ene and thiol-oxidation reactions. The polymer P ₂ can form brown film on a glass substrate and can be easily put off from the substrate. Mechanical properties of P ₂ show that tensile strength value is about 6 MPa, with elongation at break of around 300%. Glass transition temperature (Tg) of P ₂ is ?2.76 °C, meaning that P ₂ is at rubber state. There are hydroxyl groups in the prepared linear polymer, which further reacts with 1,6-hexanediisocyanate (HDI) to form polyurethane P ₄ with crosslinked structures. Compared with P ₂ , the polyurethane P ₄ forms yellow film on a glass substrate. But the film of P ₄ is not so flexible as that of P ₂ , presumably because of relatively higher Tg (5.85 °C) of P ₄ than P ₂ . Due to the existence of dynamic disulfide bonds as well as hydrogen bonds in both P ₂ and P ₄ , these thermoset resins show repeatable self-healing behavior stimulated by UV irradiation. Furthermore, the polyurethane P ₄ exhibits ultrahigh temperature resistance performance, with Td₅?=?375 °C and Td₁₀?=?1000 °C according to TGA curve. This work is expected to expand research and potential applications of the renewable resource eugenol in preparation of smart materials.     

高阻隔PVDC材料的加工及应用现状

介绍了PVDC材料的基本特性,PVDC粉末树脂的挤出吹塑工艺和PVDC乳胶的涂布工艺,PVDC涂布产品的性能及卫生安全性,PVDC产品在食品包装、药品包装、薄膜方面的应用,以及PVDC产品的发展历史与前景。     

Filled polymers with high nanoparticles concentration—Synthesis and properties

High refractive index optical compositions based on polymer matrices filled with high concentrations of ZnS nanoparticles were developed. These materials have good optical properties and processability like usual polymers, and they are suitable for factory scale use. At 25 vol % ZnS nanoparticles concentration an increase in refractive index up to 0.25 in 150 um transparent film was obtained. A process was develope for formation of polymeric compositions consisting of polymer filled with high concentrations of inorganic crystalline nanoparticles. Effects connected to high concentration of nanoparticles in the polymer were discussed. Optical properties of these materials were investigated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The excellent gas barrier properties and unique mechanical properties of poly(propylene carbonate)/organo-montmorillonite nanocomposites

Intercalated nanocomposites comprised of poly(propylene carbonate) (PPC) and organo-montmorillonite (OMMT) were prepared via a direct melt blending method. The morphological, thermal, rheological, mechanical, and gas barrier properties of composites were carried out in detail. Results of XRD, TEM, and SEM revealed that OMMT dispersed homogeneously in the polymer matrix, and were intercalated by PPC macromolecules. Compared with neat PPC, the PPC/OMMT nanocomposites showed an enhancement in the 5 wt% weight loss temperature (T _?5%) by near 20 °C with 3 phr OMMT concentration. With the percolation threshold formed, the rheological properties of composites translated from a liquid-like behavior to a solid-like one. Interestingly, PPC/OMMT nanocomposites revealed a concurrent improvement in the modulus, yield strength, and toughness with the addition of homogeneously dispersed clay. The oxygen permeability of well-dispersed PPC/OMMT nanocomposites reduced significantly compared with that of neat PPC. Consequently, this convenient and effective method, which facilitates to prepare PPC/OMMT nanocomposites with superior mechanical properties and excellent gas barrier performances, can be considered to broaden the application of PPC.     

Methods to determine solubility parameters of polymers at high temperature using inverse gas chromatography

Experimental values of Flory–Huggins parameters, χ, between polymers and probes, are frequently used to determine the solubility parameters of the polymers by the method of DiPaola–Baranyi and Guillet. The solubility parameters of probes were usually estimated by using heat of vaporization. When χ is measured at a temperature near the critical temperature of the probes and used to determine the solubility parameter of polymers, the departure of enthalpy of the probe vapor from the ideal gas state should be considered. This study discussed the method to make the correction and its effect on the determination solubility parameter of polymers. Without correction in the vapor phase enthalpy, the solubility parameters of the probes and polymer tend to be underestimated and the error increases when the critical temperature is approaching. Analytical expressions for the effect of correction on the solubility parameter of probes and parameters of polymers were derived. By use of probes with a range of solubility parameters on both sides of the solubility parameter of polymers, the correlation between parameters of polymers was shown to be reduced. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1547–1555, 2004     

Enhancing polymer/graphene oxide gas barrier film properties by introducing new crystals

A transparent, gas barrier film comprised of poly(vinyl alcohol) (PVA) and graphene oxide (GO) is synthesized through combined methods of solution blending and isothermal recrystallization. The recrystallized PVA/GO film with only 0.07 vol% GO gives an O₂ transmission rate <0.005 cc m⁻² day⁻¹ and an O₂ permeability <5.0 × 10⁻²⁰ cm³ cm cm⁻² Pa⁻¹ s⁻¹; hence, it is far superior to other blend polymer/inorganic composites. The excellent O₂ barrier properties are attributed to a unique hybrid of PVA crystals and GO sheets. PVA crystals form around the GO during isothermal recrystallization, indicating that a GO sheet can act as a nucleating agent. The newly formed PVA crystals fill in the spaces between the GO sheets, and together they become ultra-large impermeable regions, which can prevent the passage of O₂. The hybrid film has potential applications in flexible electronics, pharmaceuticals, and food packaging.