Multidimensional high‐temperature liquid chromatography: A new technique to characterize the chemical heterogeneity of Ziegler‐Natta‐based bimodal HDPE

High temperature two‐dimensional liquid chromatography (HT 2D‐LC) was recently introduced as a new technique to analyze the heterogeneities with regard to composition and molar mass present in model blends of polyolefins and various olefin copolymers. The method uses graphite as stationary phase and solvent gradients of 1‐decanol → 1,2,4‐trichlorobenzene as mobile phase for the compositional separation. With the aim to maximize the chromatographic resolution, the influence of the separation's temperature in the first dimension was evaluated: approaching the θ‐temperature of polyethylene (PE) in 1‐decanol selectively enhances the retention of higher molar mass PE standards while that of the lower molar mass ones is hardly affected. A bimodal ethylene/1‐butene copolymer and its temperature rising elution fraction (TREF) fractions were separated by HT 2D‐LC. For the first time, both axes of the contour plot were calibrated with regard to chemical composition and molar mass, respectively. Prefractionation of the bulk sample by TREF enhances the detectability of separated components of the 2D separation. The influence of the separation temperature, that is, working around the θ‐temperature of PE in 1‐decanol, can be used to enhance the chromatographic resolution of the 2D chromatography. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structural determination of ethylene‐propylene‐diene rubber (EPDM) containing high degree of controlled long‐chain branching

This work highlights an attempt to characterize the degree and nature of long‐chain branching (LCB) in an unknown sample of ethylene‐propylene‐diene rubber (EPDM). Two EPDM rubbers selected for this study were comparable in comonomer compositions but significantly different with respect to molar mass and the presence of LCB. Both rubbers contained 5‐ethylidene‐2‐norbornene (ENB) as diene. Solution cast films of pure EPDM samples were used for different characterization techniques. ¹H‐NMR, and ¹³C‐NMR were used for assessing the comonomer ratios and LCB. Size exclusion chromatography (SEC) equipped with triple detector system was used to determine the molar mass (both absolute and relative) and polydispersity index (PDI). Presence of branching was also detected using sec‐viscometry. Rheological analysis has also been used for characterizing LCB. Finally, on the basis of the experimental findings and the available theories, an attempt was made to identify the chemical nature and degree of LCB. This study reveals the possibility of detailed characterization of molecular architecture of EPDM containing LCB by comparing with an essentially linear EPDM in light of an existing theory. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Use of gradient,critical, and two‐dimensional chromatography in the analysis of styrene‐ and methyl methacrylate‐grafted epoxidized natural rubber

The growing number of heterogeneous polymeric species that are being synthesized places increasing demands on existing analytical techniques. Although size‐exclusion chromatography (SEC) has established itself as a powerful analytical tool, it has its limits when complex polymers, e.g., graft copolymers, must be analyzed. In this case, complementary techniques such as gradient HPLC and liquid chromatography at critical conditions (LCCC) are more favorable. The present study describes the synthesis and analysis of methyl methacrylate‐ and styrene‐grafted epoxidized natural rubber by different chromatographic techniques. The grafting efficiency was evaluated by gradient HPLC under normal and reversed phase conditions. Methyl methacrylate‐grafted ENR50 was further analyzed by LCCC, where separation of the rubber and grafted rubber occurred according to chemical composition but was independent of the molar mass of the methyl methacrylate homopolymers. This was followed by the combination of LCCC and SEC, where separation was achieved in two dimensions. Relevant deductions were made of both the chemical composition distribution and the molar mass distribution of the functional groups of methyl methacrylate‐grafted ENR50. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2530–2538, 2003     

化学改性三元乙丙橡胶在聚合物中的应用研究概况

综述了三元乙丙橡胶(EPDM)的化学改性概况,将化学改性的EPDM主要分为卤化、磺化以及反应性接枝改性三类;介绍了化学改性EPDM在塑料中的应用以及其与二烯类橡胶共硫化的研究现状,总结了化学改性EPDM的发展方向.     

Surface segregation of polyethylene in low‐density polyethylene/ethylene–propylene–diene rubber blends: Aspects of component structure

Aspects of the molecular weight and its distribution, the branching of low‐density polyethylene (LDPE), and the molecular composition of the ethylene–propylene–diene rubber (EPDM) matrix are presented in this article in terms of their influence on the surface segregation of polyethylene (PE) in elastomer/plastomer blends. All of the PEs studied, despite different weight‐average molecular weights and degrees of branching, segregated to the surface of the LDPE/EPDM blends. Atomic force microscopy pictures demonstrated defective crystalline structures on the surface of the blends, which together with a decrease in the degrees of their bulk crystallinity and a simultaneous increase in their melting temperatures, pointed to a low molecular weight and a defective fraction of PE taking part in the surface segregation. The extent of segregation depended on the molecular structure of the EPDM matrix, which determined the miscibility of the components on a segmental level. The higher the ethylene monomer content in EPDM was, the lower was the PE content in the surface layer of the blends. The composition and structure of the surface layer was responsible for its lower hardness in comparison with the bulk of the blends studied. The surface gradient of the mechanical properties depended on the physicochemical characteristics of the components and the blend composition, which created the possibility of tailoring the LDPE/EPDM blends to dedicated applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 625–633, 2006     

Synthesis and properties of high oil‐absorbent 4‐tert‐butylstyrene‐EPDM‐divinylbenzene graft terpolymer

The graft crosslinking polymerization of 4‐tert‐butylstyrene (tBS) and divinylbenzene (DVB) onto ethylene–propylene–diene (EPDM) was carried out in toluene by using benzoyl peroxide (BPO) as an initiator. The synthesized graft terpolymer, tBS‐EPDM‐DVB (PBED), was extracted with tetrahydrofuran (THF) into gel (called as PBED I) and sol, and then they were identified by infrared (IR) spectroscopy. The effects of solvent amount, molar ratio of DVB to tBS, EPDM content, initiator concentration, reaction temperature, and reaction time on the graft crosslinking polymerization were examined. Among them, solvent amount and molar ratio of DVB to tBS were the important factors for this reaction system. Maximum oil absorbency of PBED I was 84.0 g/g but its oil‐absorption kinetic rate was very low. Sol PBED can be reused as oil absorbent (named as PBED II) through photocrosslinking by ultraviolet light irradiation. Although the oil absorbencies of PBED II were lower than those of PBED I in most cases, their oil absorption kinetic rates were higher than oil absorbencies of PBED I. The highest value of oil absorbency of PBED II was 56.0 g/g. The thermal stability of PBED I was studied by TGA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2119–2129, 2002     

Thermal stability and aging characteristics of (natural rubber)/(waste ethylene‐propylene‐diene monomer terpolymer) blends

Comparative studies of the thermogravimetric analysis and thermo‐oxidative aging of (natural rubber)/(waste ethylene‐propylene‐diene monomer terpolymer) (NR/W‐EPDM) and (natural rubber)/(ethylene‐propylene‐diene monomer terpolymer) (NR/EPDM) blends were carried out. The blends were prepared at five different blend ratios (90/10, 80/20, 70/30, 60/40, and 50/50) on a two‐roll mill. As the pure EPDM or W‐EPDM content in the blends increased, their thermal stability also increased. The thermo‐oxidative aging of these blends was done at 100°C for 48 h. Afterwards, the NR/EPDM blends exhibited better retention of properties than the NR/W‐EPDM blends. Crosslink density measurements of the blends after thermal aging indicated that higher crosslink density was obtained from a higher content of EPDM or W‐EPDM, a result which might be due to the high rate of radical termination leading to crosslinks in the bulk of the polymer. J. VINYL ADDIT. TECHNOL., 20:99–107, 2014. © 2014 Society of Plastics Engineers     

Study on morphology of ternary polymer blends. II. Effect of composition

The composition effect on morphology of polypropylene/ethylene–propylene–diene terpolymer/polyethylene (PP/EPDM/PE) and polypropylene/ethylene–propylene–diene terpolymer/polystyrene (PP/EPDM/PS) ternary blends has been investigated. In all of the blends, polypropylene as the major phase was blended with two minor phases, that is, EPDM and PE or PS. From morphological studies using the SEM technique a core–shell morphology for PP/EPDM/PE and separated dispersed morphology for PP/EPDM/PS were observed. These results were found to be in agreement with the theoretical predictions. The composition of components affected only the size of dispersed phases and had no appreciable effect on the type of morphology. The size of each dispersed phase, whether it forms core or shell or disperses separately in matrix, can be related directly to its composition in the blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1138–1146, 2001     

三元乙丙橡胶的研究及应用进展和市场新动态

阐述了乙丙橡胶(主要是三元乙丙橡胶(EPDM)和三元乙丙橡胶/聚丙烯(EPDM/PP))在国内外的发展、应用和消费近况,重点介绍国内近期的研究成果,并对EPDM/PP在汽车工业等领域应用概况和市场前景作了分析。     

Synthesis of high rubber styrene–EPDM–acrylonitrile graft copolymer and its toughening effect on SAN

High rubber styrene–EPDM–acrylonitrile (AES) was prepared by the graft copolymerization of styrene (St) and acrylonitrile (AN) onto ethylene–propylene–diene terpolymer (EPDM) in n‐heptane/toluene cosolvent using benzoyl peroxide as an initiator. The effects of reaction conditions, such as reaction temperature, initiator concentration, EPDM content, the solvent component, and reaction time, on the graft copolymerization are discussed. In addition, according to the research on mechanical properties of the SAN/AES blend, a remarkable toughening effect of AES on SAN resin was found. By means of scanning electron microscopy, the toughening mechanism is proposed to be crazing initiation from rubber particles and shear deformation of SAN matrix. Uniform dispersion of rubber particles, as shown by transmission electron microscopy, is attributed to the good compatibility of SAN and AES. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 416–423, 2004     

New degradable polyesters from deoxycholic acid and oligo(ethylene glycol)s

A new class of polyesters was prepared by polycondensation of a bile acid, deoxycholic acid, and an oligo(ethylene glycol) (OEG) with molar mass ranging from 100 to 1500. The chemical structure and composition of the polyesters were confirmed by ¹H‐NMR, Fourier transform infrared spectroscopy and HPLC analysis. Polyester molar masses measured by gel permeation chromatography were between 5000 and 20 000. Thermal stability and glass transition temperature decreased with increasing length of OEG. Hydrolytic degradation was also enhanced by the presence of longer chain OEG. Polyesters obtained from OEG with molar mass ≥ 1000 were water soluble, semicrystalline and thermosensitive. As a function of the OEG length used for their preparation, the new polyesters can be useful for biomedical or industrial applications. © 2012 Society of Chemical Industry     

Synergic flame retardancy mechanism of montmorillonite in the nano-sized hydroxyl aluminum oxalate/LDPE/EPDM system

Nano-sized hydroxyl aluminum oxalate (nano-HAO) and montmorillonite (MMT) were mixed into low density polyethylene (LDPE)/ethylene propylene diene rubber (EPDM) system via melt compounding method. By means of LOI and UL94 horizontal burning tests, MMT and nano-HAO together exhibited better performance on flame-retarding LDPE/EPDM composites than how they performed individually, which proved that there existed a synergistic effect between MMT and nano-HAO on flame retardancy. Furthermore, through the analysis of Fourier transform IR spectra (FTIR), scanning electron microscope (SEM), and the thermogravimetric and differential thermal analysis (TG-DTA), the mechanism of the synergistic flame retardance was proposed as when MMT was added into nano-HAO/LDPE/EPDM composites, a laminated structure formed in the char layer and thus the transmission speeds of heat, oxygen, flammable mass and vapor were adjusted. So the process of combustion was retarded owing to lack of oxygen and heat.     

Positron annihilation and differential scanning calorimetric study of poly(trimethylene terephthalate)/EPDM blends

The blends of poly(trimethylene terephthalate) (PTT) and ethylene propylene diene monomer (EPDM) with different composition have been studied by positron lifetime technique (PLT) and differential scanning calorimetric (DSC) measurements. The DSC results for the blends of 50/50 and 40/60 show clear two glass transition temperatures indicating two-phase system. No melting point depression was observed for the blend system, which strongly supports the incompatibility. From the positron results an increase in free volume hole size and its concentration has been observed with the increase in EPDM content of the blend which indicates further that there is coalescence of free volumes of EPDM with the PTT to some extent and phase separation behavior continues. Another interesting aspect is that the relative fractional free volume exhibits neither negative nor positive deviation from the log additivity rule. It agrees well with the log additivity rule. The interchain interaction parameter evaluated from these results show some complex behavior. XRD results show the decrease in crystallinity of the blend with the increase in fractional free volume with the increase in concentration of EPDM.     

次磷酸铝协效MCA阻燃三元乙丙橡胶的研究

以三聚氰胺氰尿酸盐（MCA）为阻燃剂、二乙基次膦酸铝（ADP）和次磷酸铝（PAH）为阻燃协效剂,制备了无卤阻燃三元乙丙橡胶（EPDM）材料,并研究了其阻燃性能和力学性能。结果表明,当阻燃剂MCA用量为76份、ADP用量为14份、PAH用量为10份时,EPDM垂直燃烧级别达到FV-0,氧指数为30%,拉伸强度为6.7 MPa,拉断伸长率为330%。     

Influence of the rubbery phase on the crystallinity and thermomechanical properties of poly(3‐hydroxybutyrate)/elastomer blends

Poly(3‐hydroxybutyrate) (PHB) is a very promising biopolymer. In order to improve its processability and decrease its brittleness, PHB/elastomer blends can be prepared. In the work reported, the effect of the addition of a rubbery phase, i.e. ethylene–propylene–diene terpolymer (EPDM) or poly(vinyl butyral) (PVB), on the properties of PHB was studied. The effects of rubber type and of changing the PHB/elastomer blend processing method on the crystallinity and physical properties of the blends were also investigated. For blends based on PHB, the main role of EPDM is its nucleating effect evidenced by a decrease of crystallization temperature and an increase of crystallinity with increasing EPDM content regardless of the processing route. While EPDM has a weak effect on PHB glass transition temperature, PVB induces a marked decrease of this temperature thank to its plasticizer that swells the PHB amorphous phase. A promising solution to improve the mechanical properties of PHB seems to be the melt‐processing of PHB with both plasticizer and EPDM. In fact, the plasticizer is more efficient than the elastomer in decreasing the PHB glass transition temperature and, because of the nucleating effect of EPDM, the decrease of the PHB modulus due to the plasticizer can be counterbalanced. Copyright © 2010 Society of Chemical Industry     

Syntheses and properties of N‐vinylpyrrolidione‐g‐EPDM and its modified polymer

The graft copolymerizations of N‐vinylpyrrolidione(NVP) onto ethylene–propylene–diene terpolymer (EPDM) were carried out with benzoyl peroxide (BPO) as an initiator in toluene. The synthesized EPDM‐g‐NVP (ENVP) was characterized by infrared (IR) spectroscopy and gel permeation chromatography (GPC). The effects of initiator and monomer concentrations, reaction time, and temperature were investigated in the graft copolymerization. The highest graft efficiency was obtained at 0.04 mol of NVP, 2 g of EPDM, 2 wt % of BPO and 80°C for 72 h. Modified ENVP (MENVP) was obtained by the reaction of ENVP and KOH in MeOH. Properties of EPDM, ENVP, and MENVP were investigated by a thermogravimetric analyzer (TGA), an instron tensile tester, a Fade‐O‐Meter, and a UV spectrophotometer. Tensile strength and light resistance of ENVP were better than those of MENVP. The dyeability of polymers was increased in following order: MENVP > ENVP > EPDM. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1177–1184, 1999     

Unlubricated rolling and sliding wear against steel of carbon‐black‐reinforced and in situ cured polyurethane containing ethylene/propylene/diene rubber compounds

The dry rolling and sliding friction and wear of ethylene/propylene/diene rubber containing carbon black and in situ cured polyurethane (EPDM+PUR_CB) were studied. For rolling and sliding tests against steel counterparts, different experimental conditions and tribotests were selected. The apparent network properties and phase structures of the rubbers were derived from dynamic mechanical thermal analysis and atomic force microscopy results. It was concluded that in EPDM+PUR_CB, both rubber phases, present in a 1 : 1 ratio, were continuous (interpenetrating network). The coefficient of friction (COF), specific wear rate (W_s), and heat development during the tribotests were determined. The carbon black and polyurethane contents did not much influence the COF in rolling wear tests. W_s of the ethylene/propylene/diene rubber containing carbon black went through a minimum as a function of the carbon black content. W_s of the EPDM+PUR_CB compounds decreased monotonously with an increasing amount of carbon black. The incorporation of polyurethane into the ethylene/propylene/diene rubber compounds decreased the resistance to rolling wear markedly. With carbon black filling of the ethylene/propylene/diene rubber–polyurethane compound, the COF and W_s increased and dramatically decreased, respectively, under sliding wear. The wear mechanisms were inspected with scanning electron microscopy and discussed as a function of recipe modifications and changes in the testing conditions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Theory of chromatography of complex cyclic polymers: eight-shaped and daisy-like macromolecules

A theory of chromatography of eight-shaped, trefoil-shaped and daisy-like polymers is developed. For a model of an ideal chain in a slit-like pore exact equations and a number of approximate formulae for the distribution coefficient K of these polymers are derived. All modes of chromatography of complex macrocycles of arbitrary molar mass in both narrow and wide pores are covered by the theory. It is shown that complex macrocycles always elute after linear polymers and rings of the same contour length. The effective chromatographic radius of eight-shaped and daisy-like macromolecules, which determines retention in size-exclusion chromatography are calculated. The increase in the retention with molar mass is predicted for all types of macrocycles at the critical interaction condition. Non-monotonous molar mass dependences of K are found at pre-critical interaction. We simulate separation of complex cyclic polymers from linear and ring precursors, discuss possibilities to separate symmetric and asymmetric eights, and speculates on the use of chromatography for separating knotted and unknotted polymer rings. According to the theory, the chromatography under the critical and pre-critical interaction conditions is expected to be especially efficient in these and similar problems. Boundary conditions for the theory and its applicability to real systems are discussed.     

Field-flow fractionation: New and exciting perspectives in polymer analysis

The development of advanced polymeric materials requires state-of-the-art synthesis and molecular characterization protocols. Only the precise knowledge of molecular structure–property correlations allows achieving optimum performance properties of novel materials. The analysis of the molecular composition of a complex polymeric material requires the determination of its molar mass, chemical composition, functionality and molecular topology among other (less important) parameters.A number of column-based fractionation methods, including size exclusion chromatography (SEC) and high performance interaction chromatography (HPLC) are the standard techniques for the analysis of complex polymers. These methods work well as long as the molar mass is not too high and/or the macromolecules do not exhibit undesired interactions with the stationary phase (column). Certain polymers form large aggregates or other entities (micelles, liposomes) in solution that typically cannot be analyzed by column-based fractionation methods.One alternative for the fractionation of such complex materials is field-flow fractionation (FFF), an open-channel technique which does not use a stationary phase. In FFF, all problems related to the stationary phase such as undesired adsorption, shear degradation of large macromolecules, co-elution of linear and branched macromolecules, can be avoided. Different sub-techniques of FFF render the fractionation of complex polymer systems according to molecular size, chemical composition or molecular topology.In this review article, most recent developments of FFF in polymer analysis are addressed. Natural and synthetic polymers, polyolefins and polymeric nanocomposites are embraced. The most important FFF sub-techniques in polymer analysis include asymmetric flow field-flow fractionation (AF4) and thermal field-flow fractionation (ThFFF). Major developments in these very topics since 2008 are critically discussed following a previous review article that summarized earlier work (see Prog. Polym. Sci. 2009; 34: 351–68). The potentials and limitations of the different FFF sub-techniques for polymer analysis are elaborated and most recent methods of hyphenating FFF with other techniques are highlighted.     

Compatibilizer‐induced microstructural changes in poly(trimethylene terephthalate)/EPDM blends studied by the positron annihilation lifetime technique and differential scanning calorimetry

Blends of poly(trimethylene terephthalate) (PTT) and ethylene propylene diene monomer (EPDM) with and without the compatibilizer poly (EPM‐graft‐MA) were investigated by positron annihilation lifetime spectroscopy (PALS) and differential scanning calorimetric (DSC) measurements. The DSC results for the blend with 50/50 composition revealed two glass transition temperatures, indicating a two‐phase system. In the presence of compatibilizer, the two glass transition temperatures shifts towards each other, suggesting an increased interaction between the blend components. The PALS results for the blends without compatibilizer showed an increase in free volume hole size and concentration with increasing EPDM content in the blend, suggesting the coalescence of free volumes of EPDM with the PTT to some extent, but the phase‐separation behaviour continued. The free volume of these blends exhibited positive deviation from the known free volume linear additivity rule. However, poly(EPM‐graft‐MA) compatibilized blends of PTT/EPDM had a noticeable decrease in the free volume parameters, which was clearly due to the compatibilizing effect through increased interaction between blend components. Copyright © 2005 Society of Chemical Industry