Reactive Blending Of Poly Research Articles

Highly toughened poly(ʟ-lactide) by poly(ᴅ-lactide)-containing crosslinked polyurethane shows excellent malleability, flexibility and shape memory property

The brittle nature of poly(ʟ-lactide) (PLLA) limits its extensive application. In the present work, PLLA was toughened by crosslinked polyurethane (CPU), which was formed by reactive blending of poly(ε-caprolactone) (PCL), poly(d-lactide) (PDLA), hexamethylene diisocyanate (HDI) and glycerol. PCL segments in the network acted as soft segments while PDLA segments served as hard segments to form stereocomplex (SC) crystallites as physical crosslinking points. The disappearing peak at 2270 cm−1 and the emerging absorption peak appeared at 1530 cm−1 in the FTIR spectrum proved the formation of the network in the modified PLLA. The melt-quenched specimens containing the network showed significant increase in elongation at break, and the CPU80/18/2 blend showed a maximum value of 428.6%. Tensile-fractured surfaces of all the blends exhibited fibril-like morphologies because of the matrix shear yielding caused by large deformation. And the crystallization rate could be accelerated because of the PDLA chains in the sample comparing to the CPU80/20 without PDLA. Interestingly, when SC crystallites could be formed after annealing of the melt-quenched specimens at 110 °C for 1h, CPU80/18/2 still owned a maximum value of 152.8% of elongation at break. It was found that the CPU phase was presented as continuous phase in the material. Due to the compatibility, the added PDLA chains were distributed in the interface of CPU and PLLA phase, which provided additional interfacial adhesion, improved the stress transmission and endowed the material with enhanced toughness. The CPU80/18/2 sample also showed the malleability, flexibility and shape memory capacity, implying great application potential as biodegradable green composites.

Reactive blending of bisphenol-A polycarbonate with isosorbide-based polycarbonates: Effect of chain flexibility and compatibility

In this study the effect of flexible 1,4-cyclohexanedimethanol (CHDM) units on the reactive blending of poly(isosorbide-co-CHDM carbonate) (IcC-PC) with bisphenol-A polycarbonate (BPA-PC) was investigated and the contributions of chain flexibility and compatibility to transesterification were clarified. FTIR analysis revealed the presence of specific interactions between the CHDM segments of IcC-PC and the carbonyl group and phenyl rings of BPA-PC, leading to thermodynamic miscibility of the polymer blends when the CHDM content was higher than 50 mol% in IcC-PC. Addition of organotin catalysts during melt blending triggered transesterification between IcC-PC and BPA-PC, transforming the opaque blends into transparent alloys with a single Tg when the transesterification ratio reached a critical value. It was found that the reactivity of isosorbide (ISB) segments was higher than that of CHDM segments. The increase in the CHDM/ISB ratio first accelerated and then slowed down the transesterification, demonstrating that, despite of the low reactivity of the CHDM segments, the enhanced chain flexibility and compatibility were effective for promoting transesterification. Anyway, copolymerization of CHDM with ISB improved the compatibility of IcC-PC with BPA-PC, reduced the critical transesterification ratio for transparency, and remarkably shortened the blending time essential for the large-scale fabrication of transparent ISB-based polycarbonate alloys by twin-screw reactive extrusion.

Improvements in morphology, mechanical and thermal properties of films produced by reactive blending of poly(lactic acid)/natural rubber latex with dicumyl peroxide

The effect of dicumyl peroxide (DCP) as a free-radical cross-linking agent on the morphology, thermal and mechanical properties, and gas permeation of blown films prepared by reactive blending of poly(lactic acid) (PLA) and natural rubber latex was investigated. In comparison to the blown films without DCP, SEM micrographs revealed that the amount of debonded rubber domains from the cryofractured surface reduced considerably. This was when DCP at 0.003 phr was incorporated and the free radicals from thermally decomposed DCP reacted with PLA and NR chains, generating PLA–NR copolymers and cross-linked NR as confirmed by FTIR spectra. These PLA–NR copolymers acted as compatibilizers, which increased the strength at the PLA/NR interfaces, leading to the improvement in tensile strength, elongation at break, tensile toughness, impact strength, and tear strength. Although DCP did not influence the cold crystallization of PLA, TGA thermograms showed that thermal stability slightly increased owing to the enhanced interfacial adhesion. However, the addition of DCP at 0.005 and 0.010 phr resulted in a high content of cross-linked NR gel, by consuming the free radicals instead in copolymer formation. Therefore, the compatibilization efficiency was significantly reduced and the mechanical properties of reactive PLA/NR blown films finally dropped. Also, this poor interfacial adhesion facilitated the microvoid formation at the polymer–rubber interface as a result of mechanical stretching upon the film blowing process, increasing the permeation of water vapor and oxygen molecules. According to our study, it can be summarized that to optimize the morphology, mechanical properties, and gas permeation property of the free radical-assisted reactive blends, it is of great concern to carefully balance reactive compatibilizer formation and gel formation by adjusting the DCP content.

Reactive Blending of Poly(l‐lactide) and Chemically‐Modified Starch Grafted with a Maleic Anhydride‐Methyl Methacrylate Copolymer

SummaryBlends of poly(l‐lactide) (PLL) and chemically‐modified native cassava starch (CMS) have been prepared by melt mixing and then fabricated into thin films for property testing. The CMS was prepared by copolymerizing maleic anhydride and methyl methacrylate in solution in dimethyl sulfoxide in the presence of the dissolved starch. The objective was for the poly(maleic anhydride‐co‐methyl methacrylate), P(MAH‐co‐MMA), copolymer formed to then graft onto the starch via the reaction between its anhydride groups and the hydroxyl groups of the starch. The rationale behind this chemical modification was to improve the compatibility of the starch particles with the PLL matrix via intermolecular transesterification reactions during melt blending. As a result, the enhanced interfacial adhesion between the PLL and the CMS would lead to an improvement in mechanical properties such as tensile strength and toughness compared to the PLL blended with the unmodified native starch. This paper describes some of the results from this work.

Thermoplastic elastomer by reactive blending of poly(butylene succinate) with ethylene-propylene-diene terpolymer and ethylene-1-butene rubbers

Poly(butylene succinate) (PBS) was melt blended with maleic anhydride–grafted ethylene-propylene-diene terpolymer (EPDM-MAH) and maleic anhydride–grafted ethylene-1-butene copolymer (EB-MAH) to obtain thermoplastic elastomers (TPEs) containing a biodegradable polyester. PBS/EB-MAH blend showed lower modulus and excellent strain recovery compared to PBS/EPDM-MAH blend due to the smaller rubber particle size. Tensile strength of PBS/EPDM-MAH blend was found to be significantly improved by annealing because of the increased interfacial reaction between PBS matrix phase and EPDM dispersed phase and the increased cross-linking in EPDM. As the result, it was found that the annealing process is effective for the improvement of the mechanical properties of PBS/MAH-grafted rubber blends.

Preparation and characterisation of blends of poly(ethylene oxide) and functionalised epoxidised natural rubber

Blending of polymers has been a popular technique for making new materials with improved properties or processability. The synergistic properties in the blends are related to the miscibility of the components when there are significant interactions between the constituents. This paper reports the preparation of reactive blends of poly(ethylene oxide) (PEO) and acetic acid-modified epoxidised natural rubber (ENR50, which contains 50% of the isoprene units converted to epoxide groups) by solution casting. The carboxylic acid modification of ENR50 was carried out by reacting the ENR50 dissolved in toluene with excess acetic acid at 100°C. Ring-opening of epoxide group by acetic acid has led to an increase in the Tg. The effects of blend ratio of the acetic acid-modified ENR50 and PEO on the thermal properties were studied. The initial ENR50 has a Tg of −29°C and the acetic acid-modified ENR50 has led to a new Tg of 10°C. FTIR results showed that there was no chemical reaction between the acetic acid-modified ENR50 and PEO in the blends. This is in agreement with the DSC results where two distinct Tgs were observed in the blends.

Reactive blending of poly(butylene succinate) and poly(triethylene succinate): characterization of the copolymers obtained

AbstractPoly[butylene‐co‐(triethylene succinate)] block copolymers (PBSPTES), prepared by reactive blending of the parent homopolymers (PBS and PTES) in the presence of Ti(OBu)4, were analysed by nuclear magnetic resonance (NMR), wide angle X‐ray diffraction, thermogravimetric analysis and differential scanning calorimetry techniques, in order to investigate the effects of the transesterification reactions on the molecular structure and thermal properties. 1H‐NMR analysis evidenced the formation of copolymers whose degree of randomness increased with mixing time. After melt quenching, all the copolymers were found to be semicrystalline with the exception of a random copolymer. The results obtained indicated that the block size has a fundamental role in determining the rate of crystallization and therefore the phase behavior of the block copolymers. Copyright © 2012 Society of Chemical Industry

Reactive Blends of Poly(butylene adipate-co-terephthalate) and Thermoplastic Starch

The blend of poly(butylene adipate-co-terephthalate) (PBAT) and thermoplastic starch (TPS) are a promising way to get a new class of bio-compostible plastic, balance the cost effective issue and good mechanical properties. Blends of both polymers are immiscible in nature. Therefore, to make the blend to be more compatible, some block-copolymer compatibilizer can be introduced. Reactive blend is one of effective ways to create such compatibilization at the interface. The objective of this work was to study the reactive blends of PBAT/TPS in comparison to the physical blend. The reactive blends were prepared in both an internal mixer and a twin-screw extruder. For reactive blends in twin-screw extruder, PBAT, starch, glycerol and reactive agent were all pre-mixed and blended in an extruder on one step process. The weight ratio of PBAT:TPS (starch + glycerol) was fixed at 60:40. The reactive agent maleic anhydride (MA) and peroxide (Luperox® 101) were used at very low level 0-0.1 phr. The mechanical properties, morphology and flows property of blends were characterized using tensile machine, scanning electron microscope (SEM) and melt flow indexer (MFI). The internal mixer torque showed a decrease in a final torque value of TPS when MA being added, confirming the chain scsision reaction of TPS. The finer morphogy and better mechanical properties were obtained in the reactive blend with 0.1 phr of MA and 0.1 phr of peroxide.

Effects of reactive blending temperature on impact toughness of poly(lactic acid) ternary blends

Reactive blending of poly(lactic acid) (PLA) with an ethylene/n-butyl acrylate/glycidyl methacrylate terpolymer elastomer (EBA-GMA) and a zinc ionomer of ethylene/methacrylic acid copolymer (EMAA-Zn) was performed at various temperatures using a twin screw extruder. Notched Izod impact strength, dynamic mechanical properties and morphological structure of the resulting blends were studied. A sharp brittle–ductile transition (BDT) of the resulting blends occurred when the blending temperature increased to 195∼210 °C and the EBA-GMA/EMAA-Zn ratio was equal to or large than 1. The influences of blending temperature on interfacial compatibilization and croslinking of the elastomer were also studied. Supertough PLA ternary blends were achieved by this reactive approach.

Super‐ductile PBT alloy with excellent heat resistance

AbstractA super‐ductile PBT alloy with excellent heat resistance was successfully fabricated by reactive blending of poly(butylene terephthalate) (PBT) with poly(ethylene‐co‐glycidyl methacrylate) together with linear low density polyethylene (LLDPE) and hydrogenated styrene‐butadiene‐styrene block copolymer (SEBS). It possesses a unique tensile stress–strain curve with no yielding point and large elongation at break, moreover, the alloy did not show serious deterioration of the mechanical properties by high temperature annealing at 150°C for 96 h. The structure‐properties relationship is discussed on the basis of transmission electron microscopy, differential scanning calorimetry, dynamic mechanical analysis, and wide‐angle X‐ray diffraction analysis. The outstanding ductile nature seems to come from the negative pressure effect of LLDPE (or LLDPE/SEBS) particles that dilates the PBT ligament matrix to enhance the local segment motions. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.

Glassy‐Crystalline Nanostructured Polymers Via Reactive Blending

AbstractNanostructured glassy‐crystalline blends were obtained by reactive blending of poly(methyl methacrylate) (PMMA), or of poly(methyl methacrylate)‐b‐poly‐(n‐butyl acrylate)‐b‐poly(methyl methacrylate) (MBM) triblock copolymer, with polyamide‐6 (PA). The PMMA chain, or block, contains a low fraction of glutaric anhydride units which are strongly reactive toward the terminal amino group of PA. Under the blending conditions the grafting reaction is very efficient leading to a high fraction of graft copolymer. When the PA is short, Mn = 2500, nanostructured blends are obtained with both PMMA and MBM while for longer PA, Mn = 15000, nanostructures form only with the triblock MBM copolymer. The intrinsic property of MBM to self‐organize in lamellar‐like morphology seems to favour the nanostructure formation in the final blend. The resulting materials exhibit unique properties such as transparency, creep resistance and solvent resistance.

Reactive blending of poly(L‐lactic acid) with poly(ethylene‐co‐vinyl alcohol)

AbstractPoly(L‐lactic acid) (PLLA) was blended with poly(ethylene‐co‐vinyl alcohol) (EVOH) in the presence of an esterification catalyst to induce reaction between the hydroxyl groups of EVOH and the terminal carboxylic group of PLLA. Nascent low‐molecular‐weight PLLA, obtained from a direct condensation polymerization of L‐lactic acid in bulk state, was used for the blending. Domain size of the PLLA phase in the graft copolymer was much smaller than that corresponding to a PLLA/EVOH simple blend. The mechanical properties of the graft copolymer were far superior to those of the simple blend, and the graft copolymer exhibited excellent mechanical properties even though the biodegradable fraction substantially exceeded the percolation level. The grafted PLLA reduced the crystallization rate of the EVOH moiety. Melting peak temperature (Tm) of the PLLA phase was not observed until the content of PLLA in the graft reaction medium went over 60 wt %. The modified Sturm test results demonstrated that biodegradation of EVOH‐g‐PLLA took place more slowly than that of an EVOH/PLLA simple blend, indicating that the chemically bound PLLA moiety was less susceptible to microbial attack than PLLA in the simple blend. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 886–890, 2005

Crosslinking of epoxy-polysiloxane system by reactive blending

The epoxy-polysiloxane network was prepared by reactive blending of poly[(3-aminopropyl)methylsiloxane] (PAMS) containing pendant amino groups and diglycidyl ether of Bisphenol A (DGEBA). The initially immiscible blend is compatibilized during the reaction and crosslinked. Network formation, dynamics of the system and evolution of morphology were determined by dynamic mechanical analysis and light scattering techniques. The grafting epoxy-amine reaction involves a high extent of cyclization resulting in a high fraction of the sol in the networks. Dynamic light scattering data analysis reveals fast and slow relaxation modes of reacting species in the pregel and one single mode in the post-gel state. The network with a stoichiometric composition shows the most homogeneous morphology with a single glass transition temperature. On the contrary, the networks with excess of PAMS are strongly phase-separated exhibiting the unreacted PAMS-rich phase, PAMS phase partly grafted with epoxide and PAMS-DGEBA crosslinked phase.

Is It Possible to Extend the Coleman−Fox Method for Polymer Sequence Determination by NMR to Copolycondensates?

A new theory is presented for the interpretation of NMR spectra of copolycondensates, with special attention to those obtained by melt mixing of two macromolecular chains (reactive blending). The repeat unit is split into two parts, referred to as half-monomers. The present theory gives a highly accurate description of the changes in the sequence distribution during the reactive blending reaction, since the effect of the first and second neighbors along the macromolecular backbone (half-monomer penultimate effect) is explicitly considered. The theoretical predictions are compared with experimental data taken from the literature and, more specifically, NMR data concerning five copolymer systems, namely, a copolymer obtained by reactive blending of poly(ethylene terephthalate) and poly(ethylene adipate), an almost alternating copolymer with units of ether-sulfone and ether-ketone, a copolymer derived from 6-methyl-2,5-morpholinedione, and two copolymers obtained by reactive blending of poly(butylene terephthalate) with poly(bisphenolA carbonate) and Nylon6, respectively.

Mass spectra of copolymers which display compositional drifts or sequence constraints

The spectral features appearing in mass spectra of random and block copolymers which display a drift in composition are discussed along with features appearing in mass spectra of terpolymers and tetrapolymers with sequence constraints. It is shown that previous models cannot account for these features. A new model is presented and a compact equation is derived which yields MS intensities. The prediction of the model is compared with some literature data, namely mass spectrometric data concerning a block copolymer sample containing units of α-methyl styrene and of methylmethacrylate which display a strong drift in composition, the molar fraction of methylmethacrylate units changing from 0.99 to 0.80 when passing from short to long macromolecular chains. The agreement between theory and experiment is good. A hyperbranched polymer obtained by condensing 4,4′-bis[p(acetoxy)phenyl] valeric acid (referred to as diphenolic acid, DPA) was then considered. The polymer turned out to be a copolymer with regular DPA units and modified DPA units (possessing a phenol group). The molar fraction of regular DPA units changes from 0.80 to 0.95 when passing from low masses to high masses. Copolymers with sequence constraints are considered, such as ABC copolymers in which AA cannot be found along the chain or ABCD copolymers in which A cannot follow A, B cannot follow B, etc. The novel method is applied to an exactly alternating copolymer with units of styrene (St) and maleic anhydride (MAH). The St-MAH sample turned out to be a complex mixture and the presence of a small amount of units of maleic acid (MAC) is detected. The abundance of MAC, estimated by the chain statistical method, is 5%. The method is applied to the copolymer obtained by reactive blending of poly(butylene terephthalate) and poly(bisphenolA carbonate). In this case, the theoretical spectra are generated and spectral features are discussed.

Reactive blending of poly(ethylene terephthalate)(pet)/ poly(ethylene 2,6‐naphthalate)(pen). I: Effect of mixing conditions on chain structure

AbstractReactive blending of poly(ethylene terephthalate)/poly(ethylene naphthalene 2,6dicarboxylate) with addition of 2,2'‐bis(1,3‐oxazoline) (BOZ) has been studied under various mixing conditions for the different compositions. The transesterification level, the sequence length of both PET and PEN short blocks, and the degree of randomness were estimated using1H NMR. The results indicate that both mixing time and temperature are the primary factors controlling the transesterification, while the chain extender BOZ can significantly accelerate the transesterification between PET and PEN at 275°C. The composition also, to some extent, influences the transerification level as the mixing time is increased. As a consequence of transesterification proceeding, the sequence structures of the reactive blends are also markedly changed, which corresponds to a transfer from an initial block structure to a multiblock structure with higher randomness. The change in the microstructure of the reactive blends has also been analyzed by a Bernoullian statistics model. The effect of the BOZ on the intrinsic viscosity of the reactive blends is discussed.

Relationship between miscibility and chemical structures in reactive blending of poly(bisphenol A carbonate) and poly(ethylene terephthalate)

Commercial poly(bisphenol A carbonate) (PC) and poly(ethylene terephthalate) (PET) were directly melt mixed without adding any catalyst. The changes of miscibility and chemical structures during reactive blending were detected by high-field nuclear magnetic resonance spectroscopy and differential scanning calorimetry, respectively. It was found that transesterification significantly improved the miscibility between PC and PET. About 5% reaction extent was sufficient to change the blend system from initial immiscibility to miscibility. The single glass transition temperature of the miscible product did not change with further increasing extent of reaction. However, excessive exchange reaction caused severe decarboxylation and thus introduced a number of aromatic–aliphatic ether moieties into the products. As a result of the homogenization, both exchange and decarboxylation reactions were subsequently speeded up. The quantitative analysis provided a possibility to design the resultant chemical structures while producing miscible PC/PET alloy.

Reactive blending of poly (dimethylsiloxane) with nylon 6 and poly (styrene):Effect of reactivity on morphology

AbstractReactive compatibilization was used to control and stabilize 20–30wt% poly(dimethylsioxane) (PDMS) dispersions in nylon 6 (PA) and poly(styrene) (PS), respectively. The effect of the type of reation (amine (NH2)/anhydride (An), NH2/ epoxy(E) and carboxylic acid (COOH)/E) on the morphology was studied with electron microscopy. PS and PDMS have mutual solvents thus it was possible to use gel permeation chromatography (GPC) to determine the concentration of block copolymer in PS/PDMS blends. Reactive blending of PA6 with difunctional PDMS‐(AN)2 did not decrease the PDMS particle size compared to the non‐reactive blend (∼10μm). Particle size decreaeased significantly to about 0.5 μm when PA6 was blended with a PDMS containing about 4 random An groups along the chain. For the PS/PDMS blends, GPC revealed that the NH2/An reaction formed about 3% block copolymer and produced stable PDMS particles ∼ 0.4 μm. No reaction was detected for the PS‐NH2/PDMS‐E blend and the morphology was coarse and unstable. Also, PS‐NH2/PDMS‐An reactivity was lower compared to other systems such as PS/ poly (isoprene) and PS/poly(methaacrylte) using the same reaction. This was attributed to the relatively thinner PS/PDMS interface dueto the high PS/PDMs immiscibility.

Reactive blending of poly(ethylene terephthalate) with a liquid crystalline copolyester and polyhydroxyether

Poly(ethylene terephthalate) modified with a dianhydride (PET–anhydride) was melt-blended with a liquid crystalline copolyester (Vectra A) in the presence of a small amount of a liquid crystalline polyhydroxyether. The mechanical properties of a blend consisting of PET–anhydride/Vectra A/polyhydroxyether were drastically improved compared to blends without polyhydroxyether or without anhydride. Melt-spun fibers of PET–anhydride/Vectra A/polyhydroxyether in a 80/20/0.75 weight ratio displayed a much higher tensile modulus (17 GPa) and tensile strength (214 MPa) than did a 80/20 PET–anhydride/Vectra A blend (4 GPa and 60 MPa, respectively). A similar increase in modulus and strength was found for a 90/10/0.75 relative to a 90/10 blend. The tensile moduli of the blends can well be described by the Tsai–Halpin equation. A better fibril formation was observed, which was attributed to an improved viscosity ratio. Reactions between the various functional groups during melt processing were indicated by viscosity measurements. The polyhydroxyether may act as a reactive compatibilizer which improves the interfacial adhesion, chemically and/or physically. WAXD recordings of both blends showed a crystalline and highly oriented Vectra phase. The PET phase was unoriented and amorphous in a PET/Vectra blend and semicrystalline and weakly oriented in a PET/Vectra/polyhydroxyether blend. Postdrawing of the various blend fibers to λ = 4 increased the modulus by about 40% and the tensile strength by more than 100%, mainly through orientation of the PET phase. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1107–1123, 1999

Reactive blending of poly(ethylene terephthalate) with a liquid crystalline copolyester and polyhydroxyether

Poly(ethylene terephthalate) modified with a dianhydride (PET–anhydride) was melt-blended with a liquid crystalline copolyester (Vectra A) in the presence of a small amount of a liquid crystalline polyhydroxyether. The mechanical properties of a blend consisting of PET–anhydride/Vectra A/polyhydroxyether were drastically improved compared to blends without polyhydroxyether or without anhydride. Melt-spun fibers of PET–anhydride/Vectra A/polyhydroxyether in a 80/20/0.75 weight ratio displayed a much higher tensile modulus (17 GPa) and tensile strength (214 MPa) than did a 80/20 PET–anhydride/Vectra A blend (4 GPa and 60 MPa, respectively). A similar increase in modulus and strength was found for a 90/10/0.75 relative to a 90/10 blend. The tensile moduli of the blends can well be described by the Tsai–Halpin equation. A better fibril formation was observed, which was attributed to an improved viscosity ratio. Reactions between the various functional groups during melt processing were indicated by viscosity measurements. The polyhydroxyether may act as a reactive compatibilizer which improves the interfacial adhesion, chemically and/or physically. WAXD recordings of both blends showed a crystalline and highly oriented Vectra phase. The PET phase was unoriented and amorphous in a PET/Vectra blend and semicrystalline and weakly oriented in a PET/Vectra/polyhydroxyether blend. Postdrawing of the various blend fibers to λ = 4 increased the modulus by about 40% and the tensile strength by more than 100%, mainly through orientation of the PET phase. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1107–1123, 1999