Olefinic Elastomers Research Articles

Vat photopolymerization of olefinic elastomers from sulfonated ethylene-propylene-diene monomer (EPDM) latexes

Ethylene-Propylene-Diene Monomer (EPDM) rubber is recognized for elasticity over a wide temperature range and exceptional resistance to UV light and oxidative degradation. In this study, sulfonated EPDM (sEPDM) latex serves as an innovative platform for 3D printing olefinic elastomers through vat photopolymerization (VPP). The sulfonation of EPDM and subsequent neutralization with potassium hydroxide enabled the production of water-dispersible sEPDM (K-sEPDM), yielding a stable latex with an average particle diameter of 125 nm. The inherent low viscosity of the latexes allowed the direct application of elastomeric polymers during the VPP process. The photopolymerization of a scaffold precursor composition, which consisted of n-vinylpyrrolidone (NVP) and poly(ethylene glycol) diacrylate (PEGDA) in the aqueous phase of K-sEPDM latex, solidified the latex as a particle embedded hydrogel. Post-processing for removing water from the 3D printed green body facilitated coalescence of the K-sEPDM particles throughout the scaffold network, generating a second ionically crosslinked network together with scaffold as an interpenetrating polymer network (IPN). Tensile testing demonstrated tunable elastomeric properties with an ultimate strain from 315±11–453±37 % and ultimate stress from 7.6±0.5–8.2±0.3 MPa with excellent thermal recoverability. VPP of photocurable K-sEPDM with a commercial printer showcased high-resolution printing capabilities with controllable isotropic shrinkage for the printing of olefinic elastomers.

Circular olefin copolymers made de novo from ethylene and α-olefins

Ethylene/α-olefin copolymers are produced in huge scale and widely used, but their after-use disposal has caused plastic pollution problems. Their chemical inertness made chemical re/upcycling difficult. Ideally, PE materials should be made de novo to have a circular closed-loop lifecycle. However, synthesis of circular ethylene/α-olefin copolymers, including high-volume, linear low-density PE as well as high-value olefin elastomers and block copolymers, presents a particular challenge due to difficulties in introducing branches while simultaneously installing chemical recyclability and directly using industrial ethylene and α-olefin feedstocks. Here we show that coupling of industrial coordination copolymerization of ethylene and α-olefins with a designed functionalized chain-transfer agent, followed by modular assembly of the resulting AB telechelic polyolefin building blocks by polycondensation, affords a series of ester-linked PE-based copolymers. These new materials not only retain thermomechanical properties of PE-based materials but also exhibit full chemical circularity via simple transesterification and markedly enhanced adhesion to polar surfaces.

Catalytic making of ethylene‐1‐hexene elastomers: Thermodynamic guide to process development

AbstractEthylene‐alpha olefin elastomers have versatile applications. Solution copolymerization makes them, using ethylene and alpha olefin‐rich comonomer feed and metallocene and postmetallocene precatalysts, at laboratory and industry conditions. Hence, this study models ethylene solubility in toluene‐1‐hexene and n‐hexane‐1‐hexene mixtures using VLE criterion, Peng–Robinson EoS, vdW1f mixing rule, and Shulgin's activity coefficient‐Henry's constant formalism. Levenberg–Marquardt algorithm, with initial conditions comprising quasi‐ideal K factor correlation and Tait liquid phase EoS, solved the model equations. This eliminates present cumbersome literature approach. The predicted solubilities well match the experimental values at all temperature and pressure. Ethylene solubility correlates the liquid phase fluid compressibility to the corresponding catalyst active center residential environment. This offers a new approach to investigate catalyst and copolymerization phenomena and develop ethylene‐1‐hexene elastomer process. Evaluating copolymerization and microstructural property, using ethylene solubility ignoring that in 1‐hexene, introduces significant errors. The present work corrects them and solves a long‐standing polymer reaction engineering problem.

Camphene as a Mild, Bio-Derived Porogen for Near-Ambient Processing and 3D Printing of Porous Thermoplastics.

Porous structures are ubiquitous in nature due to their advantageous mechanical and transport properties. These structures have inspired various synthetic porous polymer technologies, including lightweight structural materials and membranes. While many manufacturing processes have been developed to generate porous thermoplastics, these usually include hazardous processes, such as high pressures and temperatures, or chemical components. Furthermore, few are compatible with additive manufacturing methods, such as 3D printing. Herein, we introduce bio-derived terpene camphene as a solvent and porogen for the freeze-casting of thermoplastic parts under mild conditions. Enabled by a low melting point (50 °C), camphene is used as a solvent for melt processing camphene-polymer solutions at moderate temperatures that later undergo room-temperature crystallization to template polymer-rich domains. Due to its high vapor pressure, camphene can be sublimed directly from these biphasic structures, resulting in an interconnected microporous polymer structure. Various polymers are demonstrated to be soluble in camphene, including polystyrene, an olefinic elastomer, a polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene elastomer, a cyclic olefin copolymer, and poly(ethyl methacrylate). Porous samples of each polymer were generated from camphene mixtures via compression molding, cooling, and subsequent vacuum annealing at room temperature to remove camphene. The porosity and pore structures were dependent on solution composition, including both the polymer type and polymer loading. Across the compositions investigated, porosity decreased monotonically from 93 to 65% with increasing polymer content. In the case of polystyrene, samples with pore diameters varying from ∼20 to <5 μm were generated. Rheological measurements were conducted on a series of polystyrene-camphene solutions to understand and optimize the formulation and conditions for direct ink write 3D printing. Porous parts with complex structures were successfully printed under mild conditions. These results underscore the advantages of camphene as a sustainable, nontoxic porogen and will inform future development of porous polymer systems derived from these methods.

Structure Property Relationships in PA 6 and PP Copolymers Blended by Single and Twin Screw Extrusion

AbstractPolyamides such as polycaprolactam (PA 6) and poly(hexamethylene adipamide) (PA 6.6), are generally classified as pseudo-ductile materials. Fracture behaviour of PA can be changed by melt compounding with modified olefinic elastomers such as Ethylene-propylene copolymers (EPM and EPDMs) and nitrile rubbers (NBRs). Often, small amounts of a compatibilizer are added to the polymer blend in order to assure good dispersion, morphology stability and consistent end-use properties. Maleated polypropylene (PP-MAH) has been used as compatibilizer in blends of polyamides with polyolefins as they tend to react with amine end groups in the polyamide molecules and also interact by molecular entanglement with non-funcionalized polypropylene chains. This work was intended to optimise stiffness-toughness balance in polyamide/ polypropylene blends by reactive processing of PA 6 with polypropylene heterophase copolymers using the PP-MAH as a compatibilizer. Effects of processing conditions on the blend morphology and mechanical properties were investigated by comparing compatibilized and non-compatibilized blends prepared by single and twin screw extrusion. Such approach was intended to investigate whether blend morphology and its response to processing steps can be controlled by blend composition, changes in rheology and interfacial tension during reactive processing. Viscosity measurements by torque rheometry and particle coalescence in-situ observations were performed in order to provide additional evidence of mechanisms relating to phase morphology definition in such systems.

New catalytic systems based on fluorine-containing titanium(iv) alkoxides for the synthesis of ultrahigh-molecular-weight polyethylene and olefin elastomers

New catalytic systems based on fluorine-containing titanium(iv) alkoxides for the synthesis of ultrahigh-molecular-weight polyethylene and olefin elastomers

Nonisothermal Crystallization Kinetics of Polylactic Acid under the Influence of Polyolefin Elastomers

Crystallization kinetics of various blends of poly(lactic acid) (PLA)/polyolefin elastomer (POE) was studied through nonisothermal experimental investigations and theoretical approaches. The PLA/POE blends were prepared in a melt mixing process by using two types of POEs and compatibilizers. The rubber phases used were adopted on the basis of polyethylene (PE) and polypropylene (PP) type olefin elastomers. The effects of two kinds of compatibilizers containing ethylene vinyl acetate copolymer (EVA) and ethylene acrylic ester-glycidyl methacrylate terpolymer (EGMA) on the morphology and various parameters of crystallization of PLA were investigated using scanning electron microscopy (SEM) and differential scanning calorimeter (DSC) measurements, respectively. The morphology investigations on PLA blends containing PP based olefin elastomers showed that the introduction of EGMA compatibilizer into the matrix led to a more than 100% reduction in the size of the rubber droplets. The experimental measurements of crystallization behavior of various PLA/POE blends showed that the POEs and compatibilizers could cause a fall in the initial crystallization temperature more than 13 °C. The theoretical approaches used for studying the kinetics of crystallization of PLA in the presence of various POEs and compatibilizers indicated a decrease in the crystallinity of PLA and a 64% reduction in the activation energy compared to the neat PLA. The results suggest that the largest variation in the crystallization kinetic parameters of PLA was resulted from the PP based olefin elastomer and EGMA compatibilizer.

Comparative analysis of the properties: Microcrystalline cellulose fiber polyamide composites filled with ethylene copolymer and olefin elastomer

Polyamide 6.10 (PA) composites, reinforced with microcrystalline cellulose fibers, were prepared separately using two types of coupling agents, Exxelor VA1803 (VA) and Bondyram 7103 (BR), using extrusion followed by an injection molding process. The fiber loading was fixed to 30 wt%, whereas the coupling agent was fixed to 5 wt%. The properties of the composites were characterized by the tensile properties, impact testing, differential scanning calorimetry, dynamic thermomechanical, thermogravimetric, and X-ray diffraction analyses. The distribution of the fibers into the PA was examined by a scanning electron microscope. It was found that the VA improved the mechanical and thermomechanical properties slightly compared to BR-based samples. Overall, the structural, morphological, and thermal properties of the composites were also improved comparatively using VA.

Surgical wound coverage with platelet rich fibrin and an elastic polymer sheet

Background Platelet-rich fibrin (PRF) can be prepared from the patient's peripheral blood. It releases several signal molecules, such as PDGF, TGF-b, and VEGF, which promote tissue regeneration. It is likely that covering the surgical wound with PRF stimulates healing. However, PRF alone does not have enough mechanical strength to be sutured on the surgical wound. Aim/Hypothesis This study aims to evaluate the effect of the combination of the low speed centrifuged platelet-rich fibrin (PRF) and thin elastic polymer mesh on the surgical wound for widening keratinized mucosa around the implant at the second surgery. Material and Methods In total, 8 patients aged 40–65 (mean 50.7) years, 4 male and 4 females, were included in this study. In these patients, the width of KM around the implants at the lower jaw was less than 3 mm. Smokers and patients with systemic diseases that could interfere with the healing, were excluded from this clinical study. Under local anesthesia, a partial-thickness flap was raised from the periosteum. The vestibular flap is apically displaced and sutured to the periosteum. Immediately after peripheral blood was obtained from the patient's arm vein, the blood in the plastic tube was centrifuged at low speed (283 g, 8 minutes). The upper layer was transferred and combined with a thermoplastic olefin elastomer (TPO) thin mesh in the flat glass container. The combined material of PRF and the mesh was placed on the wound dehiscence and sutured. The combined material was removed together with other stitches at 10–14 days after the surgery. The surgical site was observed and photographed up to 6 weeks. Results The combined material of PRF and TPO mesh was easily placed and sutured on the surgical wound. The application of the combined material to the surgical wound was clinically effective, increasing the width of keratinized mucosa around the implants in all the cases. Notably, the patients did not feel any distinct pain after the surgery. The average length of KM of all patients is 6.17 mm. Conclusion and Clinical Implications The combined material of PRF and TPO mesh is useful for surgical wound coverage. TPO protects the wound and stabilizes the PRF around implants. PRF is contributed to angiogenesis by participating in cell-cell cross talk and expressing various signaling molecules. PRF and TPO combination shows a synergistic effect. TPO can be clinically useful for soft tissue healing. However, further studies are necessary to figure out the effect on TPO on peri-implant biology.

Mechanical performance of thermoplastic olefin composites reinforced with coir and sisal natural fibers: Influence of surface pretreatment

In this research, composites based on thermoplastic olefin (TPO) elastomers reinforced with natural fibers were developed, having had very interesting results, aiming toward an application in the automotive industry, for manufacturing car interior components. For the first time, sisal and coir fibers were used as reinforcement of TPO composites. The best‐performing samples have had a successfully reduced maximum elongation and improved both maximum stress and Young's modulus values. Different compositions were studied regarding several parameters: type of fiber (coir or sisal treated and nontreated), coupling agent presence (maleic anhydride grafted polypropylene [MAPP]) and fiber content. Overall, the presence of fibers has had a clear positive impact on the composites' mechanical properties, enhanced by the presence of MAPP, mostly when using 4% (w/w) of fiber content. The fibers' surface treatment was especially important in this work, enabling the evaluation of the fibers' alkali treatment's influence in the final mechanical properties of the composites. The treatment successfully removed some of the most hydrophobic constituents of the natural fibers, like lignin, improving the possibility of a better adhesion of the fibers to the matrix. Finally, the mechanical properties of the composites were evaluated, and it was concluded that the alkali pretreatment had a very positive effect on several of them, aided by the presence of MAPP. POLYM. COMPOS., 40:3472–3481, 2019. © 2019 Society of Plastics Engineers

Stability of 10 mg/mL cefuroxime solution for intracameral injection in commonly used polypropylene syringes and new ready-to-use cyclic olefin copolymer sterile vials using the LC-UV stability-indicating method

Context: Injecting intracameral cefuroxime has been found beneficial in reducing the risk of postoperative endophthalmitis but its use has been limited through a lack of approved marketing and of ready-to-use single-units as well as the problem of aseptic compounding.Objective: Our aim was to assess a new automated primary packaging system which should ensure a higher level of sterility, thanks to its closed, sterile, ready-to-use polymer vial called “Crystal® vial”. The chemical stability of a 10 mg/mL cefuroxime solution was compared in 1 mL Crystal® vials and 1 mL Luer-lock polypropylene syringes (actual reference) to eliminate any potential and specific interactions with its cyclic olefin copolymer (COC) body and elastomer stopper.Methods: Cefuroxime solution was introduced into vials and syringes and stored at −20 °C, +5 °C and +25°C/60% Relative Humidity. Cefuroxime concentration and the relative amount of the main degradation product (descarbamoyl-cefuroxime) were both determined by an HPLC/UV method indicating stability. Solutions were considered steady if the concentration remained at over 90% of the initial value. In the adapted storage conditions, the evolution of osmolality, pH and sterility was assessed.Results: Stability profiles were identical between vials and syringes in all storage and temperature conditions. The solution was stable (cefuroxime concentration, pH and osmolality) and still sterile for 365 days at −20°C. The concentration fell below 90% after 21 days at +5 °C and after 16 h at +25°C/60%s relative humidity.Conclusions: The COC and thermoplastic elastomer of the vials had no impact on the degradation process confirming its possible use for a ready-to-use cefuroxime solution single-unit dose.

Effect of maleic anhydride modified olefinic elastomer and plastomer on impact properties of PBT

Poly(butylene terephthalate), a polyolefinic elastomer (POE) Engage™ 8150 and polyolefinic plastomer (POP) Affinity™ 1900 were melt blended in a co-rotating twin screw extruder. Compositions having POE, POE-g-MAH, POP and POP-g-MAH up to 15 % wt with PBT were studied. The blends were characterized for mechanical, thermal and rheological properties as well as for morphological characteristics. The mechanical properties like tensile strength, flexural strength of PBT/POE, PBT/POE-g-MAH, PBT/POP and PBT/POP-g-MAH were slightly lower than that of virgin PBT. Impact strength increased with increase in the percentage of POE, POE-g-MAH, POP and POP-g-MAH in PBT. Maleic anhydride modified olefinic elastomer showed better enhancement in impact strength as compare to maleic anhydride modified plastomer. Rheological characterization has showed an increase in shear viscosity due to the addition of elastomers as well as modified elastomers in PBT. This reveals that rheological properties also corroborate to the improvement of impact strength.

Thermal and rheological behavior of reactive blends from metallocene olefin elastomers and polypropylene

Reactive blends of metallocene polyolefin elastomers (POE)/polypropylene (PP) with 60/40 composition were prepared with an organic peroxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, and a bis-azide derivative, diphenyloxid-4,4'-bis(sulfonylazide) (BSA). Ethylene-1-butene (EB) and ethylene-1-octene (EO) copolymers and elastomeric polypropylene (ePP) were used as the elastomeric phase. The effect of elastomeric phase on the thermal, rheological, morphological and mechanical properties of the thermoplastic vulcanizates (TPVs) or dynamic vulcanizates were studied. All TPVs depicted pseudoplastic behavior and blends cured with azide curative showed higher viscosities. The TPVs showed both dispersed and continuous phase morphology that depends on the elastomeric phase type revealing a limited degree of compatibility between PP and the elastomers EO or EB. On the other hand, the TPV PP/ePP showed a uniform morphology suggesting an improved compatibility. Substantial changes observed in physical properties were explained on the basis of blends' morphology and dynamic vulcanization. The results confirm that the mechanical properties are more influenced by the elastomeric phase than by the curative agent. This study revealed a broad new range of opportunities for POE-based TPVs.

Morphology, mechanical, thermal and rheological behavior of microcellular injection molded TPO-clay nanocomposites prepared by kneader

Thermoplastic olefin elastomers (TPO)/montmorillonite (MMT) nanocomposites prepared by kneader was used in this study. The organoclay TPO nanocomposites were then injection molded by conventional and microcellular methods. Nitrogen was used as the blowing agent. The effect of organoclay content on the mechanical/thermal/rheological properties of the TPO-clay nanocomposites was investigated. The results showed that the mechanical properties (tensile, impact, and wear resistance) increased as the clay content increased. Cell size decreased as the clay loading increased. The addition of MMT into TPO also improved the thermal stability of the TPO/clay nanocomposites. The XRD results showed that the nanocomposites having an intercalated layered structure. Rheological results showed the viscosity is clay loading dependent and shear thinning effect takes place at high shear rate.

Effect of SEPS as a novel compatibilizer on the properties and morphology of PP/PC/POE blends

AbstractA novel macromolecular compatibilizer, styrene‐ethylene‐propylene‐styrene (SEPS) with high content of styrene, was investigated for the purpose of improving the compatibility of PP (polypropylene)/PC (polycarbonate)/POE (ethylene‐octene copolymer) blends. SEPS shows a remarkable compatibilizing effect since it has a particular structure with the EP‐compatible aliphatic segments, which is well miscible with the nonpolar PP and olefinic elastomer POE domains, and S‐chain segments which exhibit strong affinity with PC because of the similar molecular structure. Its compatibilizing effect was examined in terms of the mechanical, morphological, and thermal properties. The compatibilized PP‐based blends represent remarkable improvement in impact strength and balanced tensile strength. When 5 wt % SEPS was added to PP/PC/POE blends (20 wt % POE), the impact strength of the blends was enhanced from 24 to 43 kJ/m2 without obvious drop in the tensile strength. Their morphologies show a decreasing and much more homogeneous size of dispersed PC and POE particles through addition of SEPS, and the fracture surface morphologies change from irregular mosaic to the mix of mosaic and striation, and finally the regularly distant striation. The special morphology structure that resulted from the effect of the compatibilizer could be a key for enhancement of toughness and balanced rigidity of the blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

New technology expands olefin elastomers potential

The Dow Chemical Company has introduced Infuse Olefin Block Copolymers (OBCs), claimed as a breakthrough in olefin elastomers.

Recyclability of a layered silicate–thermoplastic olefin elastomer nanocomposite

A multiple-pass study was undertaken with a layered silicate–thermoplastic olefin elastomer (TPO) nanocomposite to study the impact of processing history on the properties of the material. A set of 10 passes were completed through a co-rotating intermeshing twin-screw extruder with samples collected to monitor changes in the composite. The microstructure of the nanocomposite was characterized using TEM, XRD, FT-IR, steady and complex shear rheology, and mechanical testing. With progressive passes through the extruder, the TPO nanocomposite experienced both delamination of the organoclay as well as thermo-oxidative degradation. The onset and extent of degradation were found to be unaffected by the presence of the organoclay species in the polymer, though, inclusion of a maleated compatibilizer led to increased chain scission. The generated carbonyl groups along the polymer chain as a result of oxidation were speculated to have a significant effect on the developing percolating network of clay within the material and on the final rheological properties of the composite. Despite the occurrence of degradation in the nanocomposite during recycling, its rheological and mechanical properties remained significantly higher than those of the unfilled resin.

Flow marks in injection molding of polypropylene and ethylene–propylene elastomer blends: Analysis of morphology and rheology

AbstractThis paper reports an investigation of asynchronous flow marks on the surface of injection molded parts and short shots made from two different blends of polypropylene and ethylene–propylene random copolymer elastomers. Flow marks were observed on the surface with both blends; the spatial frequency of flow marks on the surface was greater in the blend B1, which also exhibited a greater contrast between the surface regions. The same blend was distinctly faster in the linear viscoelastic tests of shear creep recovery and shear viscosity growth. The degree of contrast between the flow‐mark regions and the out‐of‐flow‐mark regions was examined with a detailed analysis of SEM micrographs of the surface regions as well as the near wall regions from short shots. This revealed that the dispersed phase was highly stretched to cylindrical strands in the glossy surface regions of both blends and retracted in the dull regions to different extents in the two cases. A comparison of the particle size distributions and aspect ratio distributions in different regions established that rapid retraction of the suspended elastomer phase was the dominant cause of changes in particle shape between surface regions. Nonlinear shear creep and creep recovery curves of the two elastomer components showed that at a time of 1 s, the fractional strain recovery of the elastomer in B1 was much higher than that of the elastomer in B2. Hence, the nonlinear elastic recovery of the elastomer phase at short times is an important factor in flow mark formation with blends of polypropylene and olefinic elastomers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 423–434, 2005

DuPont Dow Elastomers Being Dissolved

The $1.2 billion-per-year DuPont Dow Elastomers joint venture will soon be no more. Dow Chemical is exercising its option to pull the Engage olefin elastomer, Nordel hydrocarbon rubber, and Tyrin c...

The Adhesion Properties of a Thermoplastic Olefin Elastomer Grafted with Maleic Anhydride Under Nitrogen Plasma

The attenuated total reflection infrared spectroscopy (ATR), the lap shear test, and the contact angle measurement are used to analyze adhesion properties of the thermoplastic olefin elastomer (TPO) after plasma exposure. TPO is dip-coated with maleic anhydride (MA) that mixed with benzophenone (BP), benzoyl peroxide, and azobisisobutyronitrile initiators before exposed to nitrogen plasma. The amounts of grafted MA, the lap shear strength (LSS), and the surface energy depend on the plasma exposure time and the type of initiator applied. An increase in plasma exposure results in the increase of the total surface energy and the polar groups, but a decrease in the LSS of the grafted TPO. The MA grafted greatly improves the LSS of TPO and the specimen prepared with BP initiator has the greatest LSS after plasma exposure. It is also confirmed that the nature of the grafted layer could have a significant effect on the adhesion strength.