Copolymer Poly Ethylene Research Articles

Interfacing Multistage Mass Spectrometry with Liquid Chromatography or Ion Mobility Separation for Synthetic Polymer Analysis

Synthetic polymers are naturally mixtures of homologs, even in pure form. More complexity is introduced by the presence of different comonomers, end groups and/or macromolecular architectures. The analysis of such systems is substantially facilitated by interfacing mass spectrometry (MS), which disperses based on mass, with an additional level of separation involving either interactive liquid chromatography (LC) or ion mobility (IM) spectrometry, both of which are readily coupled online with electrospray ionization and MS detection. IM-MS separates in the gas phase, post-ionization and, therefore, is ideally suitable for labile and reactive polymers. Its usefulness is illustrated with the characterization of non-covalent siloxane-saccharide complexes, metallosupramolecular assemblies and an air- and moisture-sensitive inorganic polymer, poly(dichlorophosphazene). Conversely, LC-MS which separates in solution phase, before ionization, is most effective for the analysis of polymeric mixtures whose components differ in polarity. Interactive LC conditions can be optimized to disperse by the content of hydrophobic units, as is demonstrated for amphiphilic polyether copolymers and sugar-based nonionic surfactant blends. Both LC-MS and IM-MS can be extended into a third dimension by tandem mass spectrometry (MS(2)) studies on select oligomers, in order to obtain insight into individual end groups and isomeric architectures, comonomer sequences and degree of substitution, for example, by hydrophobic functionalities.

Crystallization Elution Fractionation and Thermal Gradient Interaction Chromatography. Techniques Comparison

AbstractSummary: The chemical composition distribution has been shown to be the most critical and discriminating parameter in understanding the performance of industrial polyolefins with non homogeneous comonomer incorporation. The chemical composition distribution is being analyzed by well known techniques such as temperature rising elution fractionation, TREF, crystallization analysis fractionation, CRYSTAF and crystallization elution fractionation, CEF. These techniques separate according to crystallizability and provide a powerful and predictable separation of components based on the presence of branches, irregularities or tacticity differences, independently of the molar mass. TREF, CRYSTAF and CEF can not be used, however, for the separation of more amorphous resins, and may not always provide the best solution for complex multi‐component resins due to the existence of some co‐crystallization. The application of high temperature interactive HPLC to polyolefins opened a new route to characterize these types of polymers. The use of solvent gradient HPLC for separation of polyethylene and polypropylene and the developments in HPLC on carbon based columns extended further the application of high temperature HPLC in polyolefins. A new approach has been developed recently using the carbon based column but replacing solvent gradient by a thermal gradient which facilitates the analysis of polyethylene copolymers and provides a powerful tool for the analysis of elastomers. Thermal gradient interaction chromatography (TGIC) is being compared with TREF and CEF with the analysis of model samples. The advantages/disadvantages of each technique are being investigated and discussed. The combination of TGIC and TREF/CEF provides an extended range of separation of polyolefins.

Morphological Changes of Linear, Branched Polyethylenes and their Blends during Crystallization and Subsequent Melting by Synchrotron SAXS and DSC

AbstractSummary: The crystalline structure and phase morphology of linear, branched polyethylenes and their blends during crystallization and subsequent melting were investigated, using a combination of differential scanning calorimetry (DSC), and synchrotron small angle X‐ray scattering (SAXS). A linear polyethylene (PE1) with weight‐average molecular weight (Mw) of 114 000 g/mol, and two branched polyethylene copolymers, containing 4.8 mol% (PE4) and 15.3 mol% (PE10) hexane, with molecular weights of 93 000 g/mol and 46 000 g/mol were used as pure samples. Two blends, PE1‐4 and PE1‐10, each with a weight ratio of 50/50, were prepared by solution blending. Our results indicate that in PE4 a phase separation within the branched component itself occurred, forming a broad distribution of lamellar thicknesses during the crystallization process. PE10 on the other hand did hardly crystallize because of the high degree of branching. Co‐crystallization of both components took place in blend PE1‐4 and liquid‐liquid phase separation occurred in the melt of PE1‐10. Morphological parameters were determined by using Bragg's law and the correlation function, respectively. The detected semicrystalline morphology can be well described by the lamellar insertion mode where thin lamellae develop between thicker primary lamellae. During subsequent heating, lamellae melted in the reversed sequence of their formation. The evolution of the structural parameters as a function of temperature revealed that surface melting began at first, and then the complete melting of stacks occurred until the final melting temperature was reached.

Preparation of extract-loaded nanocapsules from Onopordon leptolepis DC.

Sesquiterpenes have antifungal, antibacterial, and anesthetic properties. It is also thought that they prevent migraines and can be used as antibiotics and to treat malaria, but there are very few in-depth testing results available to support these claims. Nanocapsules coated by medicinal plants have many applications in drug manufacturing. Medicinal plants can be loaded on nanocapsules with the polyester triblock copolymer polyethylene glycol–polybutylene adipate–polyethylene glycol (PEG–PBA–PEG) as the shell and olive oil as the core by a process known as the polymer deposition solvent evaporation method. It has been shown that the size of nanocapsules depends on a variety of factors, such as the ratio of polymer to oil, concentration of polymers, and concentration of plant extract. In this research we attempted to prepare nanocapsules by emulsification of a mixture of onopordopicrin extracted from Onopordon leptolepis DC., polymer, acetone, and olive oil in aqueous phase without using surfactant. The nanocapsules were characterized by scanning electron microscopy and zeta potential sizer.

이핵 CGC의 구조적인 특성과 에틸렌/1-헥센의 공중합 거동과의 관계

Para-xylene의 기본 구조로 연결된 4개의 이핵 CGC를 활용하여 에틸렌과 1-헥센의 공중합특성을 조사하여 중합촉매의 구조적인 특징이 중합에 미치는 영향을 조사하였다. 4가지의 이핵 constrained geometry catalyst(CGC) 중에서 3가지는 모두 para-xylene 다리로 연결되어 있으나 벤젠고리 부분에 각각 다른 치환체가 결합된 것으로서 치 환체는 수소(Catalyst 1), isopropyl(Catalyst 2), n-hexyl(Cataylst 3)이고, n-octyl(Catalyst 4)인 화합물이었 다. 이핵 메탈로센 4가지와 Dow 촉매를 사용하여 에틸렌과 1-헥센을 공중합시켜 다른 치환체를 가진 다리리간드의 구 조적인 특성변화가 촉매의 중합특성과 이로부터 생성되는 공중합체의 특성에 미치는 영향을 조사하였다. 실험 결과 다 리리간드의 특성에 따라 분명한 경향성과 차이점이 발견되었다. 중합활성은 치환체의 크기가 가장 작은 수소에서 가장 높았으며, isopropyl에서 가장 낮았으며 그 차이는 최대 3배 이상이었다. 반면 분자량은 치환체가 isopropyl인 촉매에서 생성된 공중합체가 가장 컸고, n-hexyl과 1-octyl 치환체 화합물에서 가장 작은 분자량의 공중합체가 생성되었으며 그 차이는 6배에 달하였다. 이핵 CGC의 공중합 특성은 치환체가 긴 알킬기인 n-hexyl 및 1-octyl 화합물이 가장 우수하여 동일한 조건에서 1-헥센을 가장 많이 함유하여 40% 이상의 1-헥센을 포함하는 에틸렌 공중합체를 제조할 수 있었다. 이러한 연구 결과는 촉매구조 변화에 의한 고분자 미세구조 조절이라는 고분자 합성의 가장 어려운 부분 이 xylene 다리를 가진 이핵 CGC의 치환체를 조절함으로써 가능함을 보여주는 결과이다.

Cavitation‐induced rupture in high‐density polyethylene copolymers

AbstractUsing cylindrical specimens with short gauge length, bulk cavitation is successfully generated in high‐density polyethylene copolymers (HDPE) under tensile loading. The bulk cavitation is generated without the presence of sharp notch, and therefore, crack growth is not involved in the rupture process. The bulk cavitation is investigated in two types of HDPE that have different molecular characteristics. Test results indicate that bulk cavitation can be introduced in both the types of HDPE, for which the loading level is most easily identified using plots of true axial stress versus stroke. The main difference in the rupture process occurs during the postcavitation stretch. Using specimens of sufficiently long gauge length, constitutive equations for the HDPEs are determined and applied to finite element modeling of specimens with short gauge length. The results show that the hydrostatic stress level in specimens of short gauge length is about twice as high as that in specimens of long gauge length, supporting the conclusion on bulk cavitation from rubber testing. For HDPE, this study shows that the rise of hydrostatic stress level leads to the suppression of necking, to allow the bulk cavitation to dominate the deformation process. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

Solid-State Structure and Crystallization in Double-Crystalline Diblock Copolymers of Linear Polyethylene and Hydrogenated Polynorbornene

Double-crystalline diblock copolymers of linear polyethylene (LPE) and hydrogenated polynorbornene (hPN) are synthesized, and their crystallization behavior and morphology are examined using small-angle (SAXS) and wide-angle X-ray scattering (WAXS). In symmetric hPN/LPE diblocks with molecular weights above 50 kg/mol, the hPN block has previously been shown to crystallize first and set the solid-state microstructure. Two-dimensional WAXS on hand-drawn fiber specimens reveals that the LPE crystals formed in confinement stack orthogonally to the hPN crystals. By adjusting total molecular weight, the order of block crystallization may be reversed, even while holding the block length ratio fixed. At a diblock molecular weight of 20 kg/mol, simultaneous time-resolved SAXS/WAXS reveals that the LPE block crystallizes first, even when LPE is the minority component, and restricts hPN to crystallize between the LPE lamellae. The relative orientation of the LPE and hPN crystals in the lower molecular weight diblocks is examined by modeling changes in the SAXS primary peak intensity on cooling two diblocks through the hPN crystal–crystal transition, where hPN densifies as it adopts a rotationally ordered crystal structure. Only a perpendicular stacking of hPN and LPE crystals consistently yields the large reduction in primary SAXS peak intensity observed for both diblocks. Thus, even though the templating block switches from hPN to LPE as the diblock molecular weight is reduced, the orthogonal stacking motif is retained for both high- and low-molecular-weight copolymers.

Kinetics Modeling and Mechanism of Organic Matter Absorption in Functional Fiber Based on Butyl Methacrylate-Hydroxyethyl Methacrylate Copolymer and Low Density Polyethylene

Functional fiber based on butyl methacrylate-hydroxyethyl methacrylate copolymer and low density polyethylene was prepared via the method of gelation-spinning, and then the kinetics model and mechanism of organic matter absorption into the functional fiber were investigated. The results show that a lot of microvoids are constructed within the cross section of the functional fiber, but the microvoids do not make a significant contribution to the absorption of organic matter. The functional fiber can absorb toluene at a quick rate, while it can absorb trichloroethylene and chloroform at a relatively slower rate. The swelling capability of the blend fiber in selected organic matter is weaker than the one of butyl methacrylate-hydroxyethyl methacrylate copolymer fiber, and the swelling behavior is controlled by stress relaxation in the amorphous portion of the polymer blend network. Furthermore, second-order kinetics model is more suitable for describing the process of organic matter absorption than first-order kinetics model.

Effect of Interfacial Modifiers on Physical Properties and Flammability Properties of PE/Wood Composites

The ternary-monomer graft copolymers of polyethylene (GPE) were used as interfacial modifiers for recycled polyethylene (rPE)/wood flour (WF) composites. How the interfacial modifiers and WF processing methods affected the mechanical properties, thermal stability and flammability properties of the composites were investigated. Results show that the steam-braising on WF could increase the mechanical properties of the composites. The interfacial modifiers were excellent compatilizers for the rPE/WF composites that significantly increased the mechanical properties of the composites. Wood flour acted as charring agent during the combustion of the composites to improve the flame retardancy of PE/wood flour composites. Due to the improved interface compatibility between rPE and WF by GPE, the rPE/WF composites maintained excellent mechanical properties and flame retardancy even at higher filler content.

Hot-melt adhesives

A hot melt adhesive based on a functionalized metallocene polyethylene copolymer finds use in packaging applications where high heat resistance, as well as good cold tolerance, is required.

Characterization of ethylene‐propylene copolymers with high‐temperature gradient adsorption liquid chromatography and CRYSTAF

AbstractBlends of linear polyethylene (PE) and isotactic polypropylene (iPP) with different average molar masses and a series of ethylene‐propylene (EP) copolymers with different chemical composition as well as blends of PE, Ipp, and EP copolymers were separated using a carbon‐column packing (Hypercarb®) and gradients of 1‐decanol or 2‐ethyl‐1‐hexanol → 1,2,4‐trichlorobenzene (TCB). The separation is based on full adsorption of linear PE on the carbon sorbent at temperature 160°C. However, iPP is not adsorbed and elutes in size exclusion mode. The random EP copolymers have been adsorbed in the column packing and separated according to their average chemical composition after application of the gradient starting with alcohol and ending with pure TCB. The elution volumes of the copolymers depended linearly on the average concentration of ethylene in the copolymers. The HPLC elution profiles were correlated with the CRYSTAF elution profiles. In contrast to CRYSTAF, fully amorphous polyolefin samples were separated with the high‐temperature adsorption liquid chromatography. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Influence of colloidal structure of polymer mixes on adhesion strength of polyolefin compositions

Mixtures of low-density polyethylene and ethylene-vinyl acetate (EVA) copolymer are studied. It is shown that the adhesion value is defined by the polymer that forms a dispersion medium in the adhesive compositions and the type of fracture depends on the competing influence of the physical and mechanical parameters and the reduced acidity parameter of the polymer, which forms a continuous phase.

Synthesis, characterization and use of polymer‐supported phase transfer catalyst in organic reactions

AbstractA polymer‐supported (PS) phase transfer catalyst, polyethylene‐g‐quaternary ammonium salt (PE‐g‐QN+), is prepared through a three‐step graft copolymerization of maleic anhydride (MAn) onto polyethylene (PE) by photochemical method using 1% benzophenone (Bz) as photosensitizer. Post grafted acid hydrolysis of polyethylene‐g‐maleic anhydride (PE‐g‐MAn) results in the preparation of PE‐g‐succinic acid which on further treatment with tetrabutylammonium bromide (TBAB) under basic conditions in tetrahydrofuran (THF) gives PE‐g‐QN+. Optimum conditions pertaining to maximum percentage of grafting have been evaluated as a function of concentration of maleic anhydride, amount of photosensitizer, and time of reaction. Maximum percentage of grafting (25%) was obtained using 3.57 mol of MAn and 0.5 mL of 1% Bz in 120 min. The PE and graft copolymers, PE‐g‐MAn, and PE‐g‐QN+ were characterized by FTIR Spectroscopy and thermogravimetric analysis (TGA). The ionic nature of quaternary ammonium salt, PE‐g‐QN+ has also been confirmed by conductance measurements. PE‐g‐QN+ reagent have been used successfully for polymerization, amidation, and esterification reactions. The products obtained were characterized by FTIR and H1NMR spectral methods. The reagent was reused for the further reactions and it was observed that the polymeric reagent polymerize, amidate, and esterificate the compounds successfully but with little lower product yield. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Properties of mesoporous aluminosilicates prepared with nonionic surfactants

Mesoporous aluminosilicates with specific surface area up to 1030 m2/g and pore diameters from 33 to 43 A were obtained using hexadecylamine and block copolymers of polyethylene and polypropylene oxides as structural directing agents. The synthesized materials were tested in catalytic cracking of hydrotreated vacuum gas oil at 500°C.

Improved SEC-FTIR method for the characterization of multimodal high-density polyethylenes

A size-exclusion chromatography-Fourier transform infrared spectroscopy (SEC-FTIR) method for the analysis of high-density polyethylene copolymers was developed, providing superior resolution for the determination of short-chain branching as a function of time and improved repeatability by hardware adaptation and processing optimization. SEC-FTIR for characterization of polyolefins is a compromising technique. Best resolution in terms of molecular weight and molecular weight distribution requires a very low sample solution concentration in size-exclusion chromatography while best results from online infrared (IR) spectroscopy require as high concentrations as possible. The signal-to-noise ratio at the IR detector could be increased significantly after application of a bandpass filter instead of a steel mesh attenuator and furthermore influences of system instabilities could be decreased by changes in data processing. Reliable short-chain branching information in the high molecular weight section in respect to accuracy and repeatability with better chromatographic resolution could be achieved.

Property and Structure of Novel Absorptive Fiber Prepared by Blending Butyl Methacrylate-Hydroxyethyl Methacrylate Copolymer with Low Density Polyethylene

A novel absorptive fiber based on butyl methacrylate (BMA)-hydroxyethyl methacrylate (HEMA) copolymer and low density polyethylene (LDPE) was prepared by the method of gelation-spinning in twin screw extruding machine, swelling behavior, thermal behavior, crystallization behavior and nonisothermal crystallization kinetics were investigated, finally, the morphology structure for the cross-section was observed by SEM. The results show that the saturated absorbency for the blend fiber gradually decreases with increasing mass fraction of LDPE in mixture ratio from 10 wt% to 30 wt%. The results analyzed by DSC and WAXD show that crystallization and melting behaviors for the blend fiber are similar to those for pure LDPE fiber, and the crystallinity for the blend fiber decreases with decreasing mass fraction of LDPE. The results observed by SEM show that the cross-section for BMA-HEMA copolymer fiber shows a mono-phase structure with many cavities, as mass fraction of LDPE increases from 10 wt% to 30 wt%, the morphology structure with one continuous phase is transformed into another structure with two continuous phases, and the number of the cavities in the cross-section decreases, finally, the cross-section for LDPE fiber again shows a mono-phase structure without any cavities.

Effects of Carbon Black Content on Microwave Absorbing and Mechanical Properties of Linear Low Density Polyethylene/Ethylene-Octene Copolymer/Calcium Carbonate Composites

Calcium carbonate (CC) and carbon black (CB) filled composites based on linear low density polyethylene (LLDPE) and ethylene-octene copolymer (POE) were prepared by means of melt blending. The microwave absorbing performances were measured using the arch method and the electromagnetic parameters of composites were determined by transmission/reflection method. The structure and surface morphology were observed using transmission electron microscopy (TEM). LLDPE/POE/CC/CB composites show excellent microwave absorption ability. The dielectric loss from the filler CB is responsible for the microwave absorption of polymer composites. CB can effectively improve the mechanical properties of LLDPE/POE/CC composites.

Synthesis and self-assembly of miktoarm star copolymers of (polyethylene)2−(polystyrene)2

We report on the synthesis and self-assembly of a novel well-defined miktoarm star copolymer of (polyethylene)2−(polystyrene)2, (PE)2−(PS)2, with two linear crystalline PE segments and two PS segments as the building blocks based on chain shuttling ethylene polymerization (CSEP), click reaction and atom transfer radical polymerization (ATRP). Initially, alkynyl-terminated PE (PE–) was synthesized via the esterification of pentynoic acid with hydroxyl-terminated PE (PE−OH), which was prepared using CSEP with 2,6-bis[1-(2,6-dimethylphenyl) imino ethyl] pyridine iron (II) dichloride/methylaluminoxane/diethyl zinc and subsequent in situ oxidation with oxygen. (PE)2−(OH)2 was then obtained by the click reaction of PE– with diazido and dihydroxyl containing coupling agent. The two hydroxyl groups in (PE)2−(OH)2 were then converted into bromisobutyrate by esterification. At last, the (PE)2−(PS)2 miktoarm star copolymers were synthesized by ATRP of styrene initiated from (PE)2−Br2 macroinitiator. All the intermediates and final products were characterized by 1H NMR and gel permeation chromatography (GPC). The self-assembly behavior was studied by dynamic light scattering (DLS) and atomic force microscopy (AFM). The crystallization of the (PE)2−(PS)2 miktoarm star copolymers was studied by differential scanning calorimetry (DSC).

Dynamic mechanical analysis and biomineralization of hyaluronan–polyethylene copolymers for potential use in osteochondral defect repair

Treatment options for damaged articular cartilage are limited due to its lack of vasculature and its unique viscoelastic properties. This study was the first to fabricate a hyaluronan (HA)–polyethylene copolymer for potential use in the replacement of articular cartilage and repair of osteochondral defects. Amphiphilic graft copolymers consisting of HA and high-density polyethylene (HA–co-HDPE) were fabricated with 10, 28 and 50wt.% HA. Dynamic mechanical analysis was used to assess the effect of varying constituent weight ratios on the viscoelastic properties of HA–co-HDPE materials. The storage moduli of HA–co-HDPE copolymers ranged from 2.4 to 15.0MPa at physiological loading frequencies. The viscoelastic properties of the HA–co-HDPE materials were significantly affected by varying the wt.% of HA and/or crosslinking of the HA constituent. Cytotoxicity and the ability of the materials to support mineralization were evaluated in the presence of bone marrow stromal cells. HA–co-HDPE materials were non-cytotoxic, and calcium and phosphorus were present on the surface of the HA–co-HDPE materials 2weeks after osteogenic differentiation of the bone marrow stromal cells. This study is the first to measure the viscoelastic properties and osseocompatibility of HA–co-HDPE for potential use in orthopedic applications.

Preparation of Exfoliated Polyethylene/Clay Nanocomposites at High Clay Content

The polyethylene/montmorillonite (PE/MMT) nanocomposites were prepared by melt blending the organic MMT with the ternary-monomer graft copolymers of polyethylene (GPE) which were prepared by solid phase grafting maleic anhydride, methyl methacrylate and butyl acrylate onto PE. Fourier transform infrared spectroscopy was used to characterize the structure of GPE. X-ray diffraction patterns and transmission electron microscopy were used to characterize the morphology of GPE/MMT nanocomposites. Results showed that GPE was an outstanding polymeric material to prepare an exfoliated polymer/layered silicates nanocomposites due to the high polarity of GPE and high graft degree. Most layered silicates still maintain the exfoliated and well dispersed state even at 40 phr OMMT content. The exfoliation of layered silicates was attributed to the well intercalation and easy wetting of the grafted oligomers.