Dynamic mechanical properties of polystyrene‐co‐styrenesulfonic acid copolymers neutralized with aliphatic diamines

In this article, we reported the effects of the addition of various aliphatic diamines (ADAs) on the dynamic mechanical properties of poly(styrene‐co‐styrenesulfonic acid) copolymers. It was found that the ionic modulus decreased with increasing chain length of ADAs but increased for the ADA12‐containing ionomers. Upon the neutralization of the copolymers with ADAs, a minor change in the size and position of the matrix loss tangent peak was observed. However, the position of the cluster loss tangent peaks shifted to lower temperatures, and the shift rate depended on the chain length of ADAs. Thus, it was suggested that the ADAs acted mainly as preferential plasticizer for the cluster regions. In addition, the effect of the amount of ADA on the difference between the matrix and cluster temperatures of the ionomers was strongest than that of the type of ADA or ion content. The X‐ray peak of ADA12 suggested that the ADA12 acted both as plasticizer and as filler. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and properties of ethylene/styrene copolymers produced by metallocene catalysts

Ethylene/styrene copolymers were synthesized under constant polymerization conditions using six different metallocene catalysts activated with methylaluminoxane. For all the catalysts used, the activity and molecular weight of the copolymers produced decreased with the amount of styrene in the reactor feed, but the styrene content of the copolymers increased. Catalysts with carbon bridges and bulky ligands gave rise to copolymers with higher styrene content. As a result of the increased styrene content of the copolymer, the melting temperature decreased. This effect was ascribed to a decrease in the crystallinity of the copolymers. It was also found that lamellar thickness could be significantly diminished by the incorporation of comonomers. The copolymers showed a broad spectrum of mechanical properties as a function of the comonomer ratio. At low styrene contents, they behaved like typical semicrystalline thermoplastics, and at higher styrene contents, they exhibited the properties typical of elastomers. Of the catalysts tested, [rac‐ethylenebis(4,5,6,7‐tetrahydro‐1‐indenyl)]zirconium dichloride emerged as the most promising for the production of ethylene/styrene copolymers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3420–3429, 2006     

Influence of comonomer incorporation on morphology and thermal and mechanical properties of blends based upon isotactic metallocene–polypropene and random ethene/1‐butene copolymers

Blends of isotactic polypropene (i‐PP) with random ethene/1‐butene (EB) copolymers containing 10, 24, 48, 58, 62, 82, and 90 wt % 1‐butene were prepared in order to examine the influence of the EB molecular architecture on the morphology development as well as on the thermal and mechanical properties. Compatibility between i‐PP and EB increased with increasing 1‐butene content in EB to afford single‐phase blends at a 1‐butene content exceeding 82 wt %. The morphology was investigated using AFM and TEM. Improved compatibility accounted for enhanced EB dispersion and interfacial adhesion. Highly flexible as well as stiff blends with improved toughness were obtained. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 838–848, 1999     

Thermal and dynamic mechanical behavior of ethylene/norbornene copolymers with medium norbornene contents

A range of ethylene/norbornene copolymers were synthesized using the commercially available rac‐Et(Ind)₂ZrCl₂ metallocene catalyst. A large window of norbornene contents, between 30 and 55 mol % was used to facilitate the interpretation of the results. The polymers were characterized by means of wide‐angle X‐ray scattering, differential scanning calorimetry, and dynamic mechanical thermal analysis. The X‐ray diffractograms showed two amorphous halos, the low‐angle one increasing in the intensity with norbornene content. Calorimetric and dynamic mechanical results led to a linear relation between the glass transition temperature and the norbornene content. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2159–2165, 2001     

Carbon/carbon composites derived from poly(ethylene oxide)‐modified novolac‐type phenolic resin: Microstructure and physical,and morphological properties

A poly(ethylene oxide) (PEO) novolac‐type phenolic resin blend was prepared by the physical blending method. The modified novolac‐type phenolic resin with various PEO contents was used as a matrix precursor to fabricate carbon/carbon composites. The effect of the PEO/phenolic resin mixing ratio on the change of the density and of the porosity was studied. The flexural strength and interlaminar shear strength of the PEO/phenolic resin blend‐derived carbon/carbon composites were also investigated. The results show that the density of the PEO/phenolic resin blend‐derived carbon/carbon composites decreases with the PEO content. The X‐ray diffraction and Raman spectra studies showed that the carbon fiber in the samples will affect the growth of the ordered carbon structure. From SEM morphological observation, it is shown that the fracture surface of specimens is smooth. Also, there is less fiber pull‐out and fiber breakage on the fracture surface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1609–1619, 2002; DOI 10.1002/app.10407     

The influence of thermal treatment and processing on the structure and morphology of poly(propylene‐ran‐1‐butene) copolymers

New poly(propylene‐ran‐1‐butene) copolymers were analyzed to study the influence of different processing techniques on their structure and morphology. Wide‐angle X‐ray diffraction allowed determination of the percentage of the γ form and the crystallinity in the samples and also the influence of the percentage of 1‐butene on the cell parameters. Furthermore, it was possible to appraise the contributions of different stacks of lamellae to the small‐angle X‐ray diffraction patterns. © 2001 Society of Chemical Industry     

Characteristics of diether‐ and phthalate‐based Ziegler‐Natta catalysts for copolymerization of propylene and ethylene and terpolymerization of propylene,ethylene, and 1‐butene

Copolymerization of propylene and ethylene and terpolymerization of propylene, ethylene, and 1‐butene were carried out to compare the characteristics of diether‐ and phthalate‐based Ziegler‐Natta catalysts in a reaction system of pilot scale. The ethylene incorporation with the diether‐based catalyst was higher but the 1‐butene incorporation was lower compared with those of the phthalate‐based catalyst. In the case of copolymers from the diether‐based catalyst, melting behavior, determined through differential scanning calorimetry (DSC), showed a distinct shoulder peak and lots of nuclei were formed during crystallization. The diether‐based catalyst led to polymers having blockier ethylene sequences compared with those of the phthalate‐based catalyst; the highly crystallizable fraction (HIS) containing blockier ethylene sequences was produced with the diether‐based catalyst. These results seem to be the result of regio‐irregular characteristics of the diether‐based catalyst. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 851‐859, 2013     

Effect of annealing temperature on phase composition and tensile properties in isotactic poly(1‐butene)

The influence of annealing temperature on the kinetics of polymorphic changes and mechanical properties within the time in isotactic poly(1‐butene) (PB‐1) has been investigated by wide‐angle X‐ray scattering and tensile testing. Extruded tapes of PB‐1 have been exposed to several annealing temperatures: ?22, +5, +22, +40 and +60°C. The evolution of content of Phase I for various annealing temperatures upon time shows predominantly S‐shaped trend. Annealing temperature considerably affects the overall rate of transformation in PB‐1. On the other hand, the resulting mechanical properties are solely controlled by the polymorphic composition. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of ABA triblock and novel multiblock copolymers from ethylene glycol,L‐lactide,and ϵ‐caprolactone

Three types of copolymers were synthesized and characterized. First, triblock ABA copolymers [where A is a homopolymer of ?‐caprolactone and B is poly(ethylene glycol)] were prepared by the ring‐opening polymerization of poly(ethylene glycol) with ?‐caprolactone in the presence of stannous octoate (Sn(Oct)₂). The spectral, thermal, and mechanical properties of one sample of these copolymers were studied, and it was discovered that these types of copolymers were more hydrophilic, possessed lower melting points, and had superior mechanical properties (greater toughness) than poly(?‐caprolactone). Second, triblock ABA copolymers [where A is a homopolymer of L ‐lactide and B is poly(ethylene glycol)] were prepared by the ring‐opening polymerization of poly(ethylene glycol) with L ‐lactide in the presence of Sn(Oct)₂. The mechanical properties of these copolymers were studied, and it was found that they were tougher and softer than poly(L ‐lactide). Third, novel ABA triblock copolymers [where A is a copolymer of ?‐caprolactone and L ‐lactide and B is poly(ethylene glycol)] were prepared, and ¹H‐NMR and ¹³C‐NMR spectra of these copolymers indicated a microblock structure for the two end blocks. The stress–strain behavior revealed low yields and high toughness for these copolymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2072–2081, 2002     

Synthesis,thermal, and dynamic mechanical properties of 1,3‐bis(diphenylsilyl)‐2,2,4,4‐tetraphenylcyclodisilazane‐containing polydimethylsiloxanes

New and effective approaches to the synthesis of 1,3‐bis(diphenylsilyl)‐2,2,4,4‐tetraphenylcyclodisilazane‐containing polydimethylsiloxanes ( P1 and P2 ) were developed. P1 was obtained by polycondensation of cyclodisilazane lithium salt and chloroterminated polydimethylsiloxane. P2 was produced by hydrosilylation of vinyl‐terminated cyclodisilazane and hydrogen‐terminated polydimethylsiloxane. The polycondensation completed quickly at room temperature, while the hydrosilylation was facile and did not require cumbersome air‐sensitive operations. P1 and P2 were characterized by Fourier transform infrared, nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis (TGA), and isothermal gravimetric analysis (IGA). TGA revealed the outstanding thermal properties of P1 and P2 with 5% weight loss temperatures (T_d5) higher than 450°C. IGA proved their better thermal stability at 450°C for 800 min, compared to polydimethyldiphenylsiloxane. Dynamic mechanical analysis showed that silicone rubbers made from cyclodisilazane‐containing polydimethylsiloxanes could have a maximum tan δ value as high as 1.13 and had good prospects for damping material applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polypropylene/polyethylene blends as models for high‐impact propylene‐ethylene copolymers,part 2: Relation between composition and mechanical performance

The relation between composition and mechanical performance of a series of binary polyolefin blends was studied in this article. A fractionation of these model compounds with temperature rising elution fractionation (TREF) was applied to study the possibility to fractionate industrially relevant heterophasic polyolefin systems. The separation quality according to molecular structures or chemical composition was found to be good for most of the systems, but especially the separation of ethylene‐propylene random copolymer and high density polyethylene by TREF turned out to be difficult if not impossible. An extensive mechanical characterisation including the determination of brittle‐to‐ductile transition curves showed significant effects of modifier type and amount. Toughness effects can be related primarily to the modulus differences between modifier and matrix. Compatibility and particle size only have a secondary influence, but must be considered for a detailed interpretation of the mechanics of the investigated systems. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Blends of high density polyethylene and ethylene/1‐octene copolymers: Structure and properties

The morphology formation in the blends comprising a high density polyethylene (HDPE) and selected ethylene/1‐octene copolymers (EOCs) was studied with variation of blend compositions using atomic force microscopy (AFM). The binary HDPE/EOC blends studied showed well phase‐separated structures (macrophase separation) in consistence with individual melting and crystallization behavior of the blend components. For the blends comprising low 1‐octene content copolymers, the lamellar stacks of one of the phases were found to exist side by side with that of the another phase giving rise to leaflet vein‐like appearance. The formation of large HDPE lamellae particularly longer than in the pure state has been explained by considering the different melting points of the blend components. The study of strain induced structural changes in an HDPE/EOC blend revealed that at large strains, the extensive stretching of the soft EOC phase is accompanied by buckling of HDPE lamellar stack along the strain axis and subsequent microfibrils formation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1887–1893, 2007     

Crystallinity morphology and dynamic mechanical characteristics of PBT polymer and glass fiber‐reinforced composites

The crystalline morphologies of PBT (poly butylene terephthalate) and its glass fiber reinforced composite systems were investigated in a thin‐film form by polarized optical microscopy and wide‐angle X‐ray diffraction. Three different types of PBT morphology were identified in the Maltese cross pattern: 45° cross pattern (usual type) by solvent crystallization, 90° cross pattern (unusual type) by melt crystallization at low crystallization temperature, and mixed type by melt crystallization at crystallization temperatures higher than 160°C. The glass fibers increased the number density of spherulites and decreased the size of crystallites acting as crystallization nucleation sites without exhibiting trans‐crystallinity at the vicinity of the glass fiber surfaces. Finally, the storage modulus was analyzed by using a dual‐phase continuity model describing the modulus by the power‐law sum of the amorphous‐ and crystalline‐phase moduli. The crystalline‐phase modulus was extracted out from the PBT polymer and composite systems containing different amount of crystallinity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 478–488, 2002     

Structure and properties of polyimide‐g‐nylon 6 and nylon 6‐b‐polyimide‐b‐nylon 6 copolymers

Polyimide‐g‐nylon 6 copolymers were prepared by the polymerization of phenyl 3,5‐diaminobenzoate with several diamines and dianhydrides with a one‐step method. The polyimides containing pendant ester moieties were then used as activators for the anionic polymerization of molten ε‐caprolactam. Nylon 6‐b‐polyimide‐b‐nylon 6 copolymers were prepared by the use of phenyl 4‐aminobenzoate as an end‐capping agent in the preparation of a series of imide oligomers. The oligomers were then used to activate the anionic polymerization of ε‐caprolactam. In both the graft and copolymer syntheses, the phenyl ester groups reacted quickly with caprolactam anions at 120°C to generate N‐acyllactam moieties, which activated the anionic polymerization. All the block copolymers had higher moduli and tensile strengths than those of nylon 6. However, their elongations at break were much lower. The graft copolymers based on 2,2′‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride and 2,2′‐bis[4‐(4‐aminophenoxy)phenyl]propane displayed elongations comparable to that of nylon 6 and the highest moduli and tensile strengths of all the copolymers. The thermal stability, moisture resistance, and impact strength were dramatically increased by the incorporation of only 5 wt % polyimide into both the graft and block copolymers. The graft and block copolymers also exhibited improved melt processability. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 300–308, 2006     

Morphology and mechanical properties of binary blends of polypropylene with statistical and block ethylene‐octene copolymers

In the present work, statistical (EOCs) and block (OBCs) ethylene‐octene copolymers, with similar densities and crystallinities, were used as impact modifiers of isotactic polypropylene (iPP), and the toughening effects of these two types of elastomers were compared. The viscosity curves of EOCs were similar to those of OBCs with equivalent melt flow rate (MFR), enabling a comparison of the viscosity ratio and elastomer type as independent variables. No distinct differences on the crystal forms and crystal perfection of iPP matrix in various blends were observed by thermal analysis. Morphological examination showed that OBCs form smaller dispersed domains than EOCs with similar MFRs. The flexural modulus, yield stress, stress and strain at break showed the same variation tendency for all the investigated polypropylene/elastomer blends. However, the room temperature Izod impact toughness of iPP/OBC blend was higher than that of iPP/EOC blend containing elastomer with the similar MFRs. The experimental results indicated that the compatibility of iPP/OBCs was much higher than that of iPP/EOCs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Quantification of shish–kebab and β‐crystal on the mechanical properties of polypropylene

The oriented “shish–kebab” structure and β‐crystal can enhance the mechanical properties of polypropylene products. In this regard, equipment and β‐nucleation agents have been developed or modified to form shish–kebab and β‐crystal. However, the effect of shish–kebab/β‐crystal proportion on the mechanical properties of polypropylene remains unclear. The answer is crucial but remains a challenge because of the difficulty in manipulating the shish–kebab proportion. In this work, we used a self‐made multiflow vibrate‐injection molding, which can provide a controllable shear flow, to produce samples with different shear‐layer thicknesses. The shish–kebab proportion was represented by R, which is the thickness ratio of the shear layer to that of the whole sample. Results showed that the tensile strength exponentially increased, whereas the elongation at break exponentially decreased, with R. The impact strength remained constant with R, indicating that the shish–kebab and β‐crystal possessed similar toughening effects. This work proposes a schematic to interpret the strengthening mechanism involved and presents a method of establishing and controlling the mechanical properties of polypropylene samples by using shish–kebab structures and β‐crystals. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45052.     

Segmented organosiloxane copolymers: 2 Thermal and mechanical properties of siloxane—urea copolymers

The structure-property behaviour of new siloxane-urea containing segmented copolymers has been investigated. Amino-propyl terminated poly(dimethylsiloxane) oligomers of from 900–3660 M_n were reacted with various diisocynates to form segmented copolymers with urea linkages. The length of the hard segments in these copolymers corresponds approximately to the length of the diisocynate unit employed. A number of mechanical and thermal properties were investigated for these phase separated materials. It was found that the performance of these copolymers was effected by varying the hard segment type and/or content and that high strength necessitates a microphase texture. The two phase nature of these copolymers was verified by dynamic mechanical, thermal and SAXS studies. The phase separation was found to occur in these copolymers even with 6% hard segment by weight. In conclusion, these materials displayed a behaviour similar to the segmented polyurethanes and were found to be superior to the unfilled silicone elastomers.     

Linking morphology changes to barrier properties of polymeric packaging for microwave‐assisted thermal sterilized food

It is a priority to develop polymeric packaging that can withstand microwave‐assisted thermal sterilization (MATS) and maintain the quality of low‐acid foods during long‐term storage. In this study, we explored changes in the morphology of pouch films with two multi‐layer structures. The films are based on barrier layers of metal oxide‐coated poly(ethylene terephthalate) (PET) (film A) and ethylene vinyl alcohol (EVOH) (film B). A 8‐oz model food in pouches was processed with MATS (F₀ = 9.0 min) and stored at 23, 35 and 45 °C for up to 12 months. Findings reveal that the oxygen barrier of film A was influenced by the coating and crystallinity of PET. The oxygen barrier of film B was primarily affected by the moisture content of the EVOH polymer. Results also show that changes in barrier properties depended on storage temperature. Recrystallization in polymer might be an important morphological change that occurs during storages. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45481.     

Effect of annealing time and molecular weight on melt memory of random ethylene 1‐butene copolymers

The effects of annealing time and molecular weight on the strong melt memory effect observed in random ethylene 1‐alkene copolymers are analyzed in a series of model ethylene 1‐butene copolymers with 2.2 mol% branches. Melt memory is associated with molten clusters of ethylene sequences from the initial crystals that remain in close proximity and are unable to diffuse quickly to the randomized melt state, thus increasing the recrystallization rate. Melt memory persists even for greater than 1000 min annealing indicating a long‐lived nature of the clusters that only fully dissolve at melt temperatures above a critical value (>160 °C). Below the critical melt temperature, molecular weight and annealing temperature have a strong influence on the slow kinetics of melt memory. For the copolymers analyzed, slow dissolution of clusters is experimentally observed only for M_w < 50 000 g mol^?1. More stable clusters that survive higher annealing temperatures display slower dissolution rates than clusters remaining at lower temperatures. The threshold crystallinity level to enable melt memory (X_c,threshold) decreases with increasing molecular weight and decreasing annealing temperature similarly to the variation of the chain diffusivity in the melt. The process leading to melt memory is thermally activated as the variation of X_c,threshold with temperature follows Arrhenius behavior with high activation energy (ca 108 kJ mol^?1) that is independent of molecular weight. © 2018 Society of Chemical Industry