Presence Of Chain Extender Research Articles

Upcycling of post-industrial starch-based thermoplastics and their talc-filled sustainable biocomposites for single-use plastic alternative

This study utilized post-industrial wheat starch (biological macromolecule) for the development of poly(butylene adipate-co-terephthalate) (PBAT) based thermoplastic starch blend (TPS) and biocomposite films. PBAT (70 wt%) was blended with plasticized post-industrial wheat starch (PPWS) (30 wt%) and reinforced with talc master batch (MB) (25 wt%) using a two-step process, consisting of compounding the blend for pellet preparation, followed by the cast film extrusion at 160 °C. The effect of the chain extender was analyzed at compounding temperatures of 160 and 180 °C for talc-based composites. The incorporation of talc MB has increased the thermal stability of the biocomposites due to the nucleating effect of talc. Moreover, tensile strength and Young's modulus increased by about 5 and 517 %, respectively as compared with the TPS blend film without talc MB. Thermal, rheological, and morphological analyses confirmed that the use of talc in the presence of chain extender at a processing temperature of 160 °C has resulted in an enhanced dispersion of talc and chain entanglement with PBAT and PPWS than PBAT/PPWS blend and PBAT/PPWS/Talc composite films. On the other hand, at 180 °C, the talc-containing biocomposite with chain extender tended to form PPWS agglomerates, thereby weakening its material properties.

Synthesis of Poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) Bioplastic with Bio-based Isosorbide Diester

In situ chain-extended poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) (PLLA-PEG-PLLA) block copolymers synthesized by ring-opening polymerization of L-lactide in the presence of chain extender were more flexible than PLLA. However, flexibility of PLLA-PEG-PLLA requires further improvement to broaden its applications. Herein, plasticization of PLLA-PEG-PLLA with an isosorbide diester bio-based plasticizer (5-20 %wt) is described. PLLA/isosorbide diester blends were also prepared for comparison. The blends prepared via melt blending revealed that isosorbide diester showed good phase compatibility with both the PLLA and PLLA-PEG-PLLA. The addition of isosorbide diester significantly enhanced plastic deformation of cryo-fracture surfaces for PLLA-PEG-PLLA-based blends whereas the plastic deformation was started at 20 %wt isosorbide diester for PLLA-based blends. Crystallization properties and thermal stability of PLLA-PEG-PLLA greatly improved after the addition of isosorbide diester but did not increase the thermal stability for PLLA-based blends. The strains at break of the PLLA-PEG-PLLA-based blends containing 5 %wt, 10 %wt and 20 %wt isosorbide diester were 89.9%, 145.3% and 110.5%, respectively: these were higher than the pure PLLA-PEG-PLLA (59.8%). The plastic deformation, thermal stability and strain at break of the PLLA-PEG-PLLA-based blends increased greatly with content of isosorbide diester, reaching a maximum at 10 %wt isosorbide diester. Therefore, isosorbide diester is promising as a bio-based plasticizer for PLLA-PEG-PLLA to produce highly flexible PLLA-based bioplastics.

Improvement in Crystallization and Toughness of Poly(L-lactide) by Melt Blending with Poly(L-lactide)-b-polyethylene glycol-b-poly(L-lactide) in the Presence of Chain Extender

Improvement in Crystallization and Toughness of Poly(L-lactide) by Melt Blending with Poly(L-lactide)-b-polyethylene glycol-b-poly(L-lactide) in the Presence of Chain Extender

Synthesis of flexible poly(l-lactide)-b-polyethylene glycol-b-poly(l-lactide) bioplastics by ring-opening polymerization in the presence of chain extender

Abstract Poly(l-lactide)-b-polyethylene glycol-b-poly(l-lactide) (PLLA-PEG-PLLA) is found to be more flexible than PLLA due to the flexibility of PEG middle blocks. Melt flow and mechanical properties of PLLA-PEG-PLLA were improved through post melt blending with a chain extender (CE). In this work, in situ chain-extended PLLA-PEG-PLLAs were synthesized by ring-opening polymerization in the presence of Joncryl® CE. The influence of CE content (1.0, 2.0, and 4.0 phr) on the gel content, melt flow index (MFI), thermal properties, and mechanical properties of the obtained in situ chain-extended PLLA-PEG-PLLAs was investigated. The gel content of in situ chain-extended PLLA-PEG-PLLA increased while the MFI and degree of crystallinity significantly decreased with increasing CE content. The in situ chain-extended PLLA-PEG-PLLA with 1.0 phr CE showed the best tensile properties. The extensibility of in situ chain-extended PLLA-PEG-PLLA films decreased when the CE contents were higher than 1.0 phr. These in situ chain-extended PLLA-PEG-PLLA films can be used as highly flexible bioplastics.

Toughening of Poly(L-lactide) with Blends of Poly(ε-caprolactone-co-L-lactide) in the Presence of Chain Extender.

A poly(ε-caprolactone-co-L-lactide) copolyester was synthesized and employed to toughen poly(L-lactide) (PLLA) by reactive melt blending in the presence of an epoxy-based chain extender. The effects of chain extension reaction and copolyester content on properties of PLLA-based blends were studied. The chain extension reaction reduced crystallinity and melt flow index of PLLA/copolyester blends. Meanwhile the copolyester blending improved the crystallinities of the chain-extended PLLA up to 20 wt% copolyester. The phase compatibility between PLLA matrix and dispersed copolyester phases was enhanced by the chain extension reaction. The impact strength of chain-extended PLLA increased with the contents of copolyester and chain extender.

Tensile and Impact Properties of Recycled Poly(Ethylene Terephthalate) and Polycarbonate Composites Reinforced with Silane Treated Hollow Glass Microspheres

Recycled poly (ethylene terephthalate) or R-PET is conventionally melt blended with polycarbonate with the presence of chain extender in order to produce polymer blend that provides good mechanical properties and cost effectiveness. This research was carried out to improve properties of such a blend by compounding them with silane treated hollow glass microspheres (HGMs), which mixing procedure was emphasized how it could affect mechanical properties. R-PET/PC/HGM composites of a fixed composition were melt compounded with three different mixing procedures. It was found that the compounding HGMs with PC and then R-PET obtained the most rigidity specimens than the all-in-one compounding or the compounding HGMs with R-PET and then PC. Silane treated HGMs were well distributed in the polymer matrix presenting good interfacial adhesion. However, the notched impact strength of all composites were inspected to be in the same range.

Improvement of compatibility and mechanical properties of the poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) blends and films by reactive extrusion with chain extender

Biodegradable poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) (PLA/PBAT) blends and films were prepared by melt blending and blowing films technique in the presence of chain extender. The Joncryl ADR‐4370F (ADR) was used as the chain extender. The effect of ADR on the mechanical properties, rheological behavior, morphology, and thermal behavior of PLA/PBAT blends was investigated. The mechanical properties were markedly improved by incorporation of 0.15 phr ADR, for example, the elongation at break increased from 23.5% to 410.3% and the notched Izod impact strength increased from 7.5 to 33.4 KJ/m2 for the PLA/PBAT/ADR blends. The elongation at break increased from 17.7% to 264.6% and the tensile strength increased from 28.0 to 40.7 MPa for the PLA/PBAT/ADR films in the transverse direction. The tensile strength and tear strength of the films increased from 28.0 to 40.7 MPa and from 135.5 to 163.8 kN/m in the machine direction, respectively. Morphological observation through scanning electron microscopy revealed that the compatibility of the PLA/PBAT blends was greatly enhanced by the incorporation of ADR. The interfacial adhesion was improved between PLA phase and PBAT phase. These findings contributed new knowledge to the additives area and gave important implications for manufacturing biodegradable polymer packaging material. POLYM. ENG. SCI., 58:1868–1878, 2018. © 2017 Society of Plastics Engineers

Investigating the effect of multi-functional chain extenders on PLA/PEG copolymer properties

Biodegradable copolymers polylactic acid-co-poly ethylene glycol (PLA-co-PEG) were synthesized at a specific volume ratio (PLA/PEG) (80/20) using direct melt polycondensation without solvent. The effects of an oligomeric chain extender (CE) on the mechanical, molecular weight, thermal stability, and degradation were evaluated. The copolymers were tailored by introducing classes of CE contents (0.25, 0.5, 0.075, 1.0, 1.25, and 1.5wt%) (styrene- glycidyl acrylate copolymer). Apparently, the mechanical properties of copolymers were enhanced in the presence of CE. A long chain branch structure has led to a slight improvement of tensile strength to reach 70MPa at CE 1.25%, compared with 60MPa for neat PLA. A significant increase of 17% was observed for the elongation at break of copolymers after addition of CE 1.25%. In addition, the impact strength increased to 7.9KJ/m2 in the ranges of CE 1–1.25%. Melt flow index dramatically reduces with the addition of CE contents. Gas Permeation Chromatography (GPC) showed that the addition of CE 1.25% has resulted in increasing the PLA molecular weight to 132.569kDa with a broad molecular weight distribution, MWD (2.066), and bimodal distribution. Differential Scanning Calorimetric (DSC) results revealed that the chain extension process improved glass transition temperature (Tg) 62°C, melting temperature (Tm) 161°C, and crystallinity (X%) 34.9% as a result of CE 1.25%. Thermal gravimetric analyses (TGA) results indicated that the CEs have a positive effect on the enhancement of thermal stability. Moreover, Scanning Electron Microscopic (SEM) showed that the compatibility and interfacial adhesion between the PLA and PEG chains were enhanced in the existence of the CE contents. The weight loss of the copolymer during 30days of degradation time was 28%, while the weight loss of CE 1.5% was only 3% during the same time interval.

An evaluation of the mechanical and adhesion properties of a hydroxyl-terminated polybutadiene (HTPB)-based adhesive including different kinds of chain extenders

The effects of 1,5-pentanediol (PDO) and N, N-Bis (hydroxyethyl) aniline (ISL) chain extenders on the mechanical and adhesion properties of the polyurethane adhesives based on hydroxyl-terminated polybutadiene were studied. Results showed that both chain extenders (ISL and PDO) improved the adhesion properties of the polyurethane on the aluminum substrate. The peel test modulus increased significantly in the presence of both chain extenders. The increase was more pronounced using PDO chain extender (the one with aromatic side group). A decrease in contact angle and an increase in work of adhesion were obtained by addition of chain extenders to the polyurethane. The glass transition temperature of the PU did not change significantly in the presence of chain extenders. However, the cross-linking density and toughness of the polyurethane increased significantly by addition of the chain extenders. Results showed that chain extender without side chain (PDO) improved the adhesion as well as the mechanical properties of the polyurethane much greater than the one with aromatic side ring.

Foaming of Polylactide in the Presence of Chain Extender

An experimental study on the influence of chain extender (CE) on the properties and foamability of two grades of polylactide (PLA) has been carried out. The influence of CE on the polymer crystallinity and viscoelastic properties that are critical during the foaming process was investigated. After addition of CE an increase in the viscosity and the cold crystallization temperature of PLA was observed. Selection of PLA grade has been correlated with a structure of the polymer. The cellular structure of PLA was obtained during extrusion process using the chemical blowing agent. The addition of 1.0 and 1.5 % CE caused fine cellular structure and low density (0.7 g/dm3) of foamed PLA.

Effect of Chain-Extenders on the Properties and Hydrolytic Degradation Behavior of the Poly(lactide)/ Poly(butylene adipate-co-terephthalate) Blends

Biodegradable poly(lactide)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends were prepared by reactive blending in the presence of chain-extenders. Two chain-extenders with multi-epoxy groups were studied. The effect of chain-extenders on the morphology, mechanical properties, thermal behavior, and hydrolytic degradation of the blends was investigated. The compatibility between the PLA and PBAT was significantly improved by in situ formation of PLA-co-PBAT copolymers in the presence of the chain-extenders, results in an enhanced ductility of the blends, e.g., the elongation at break was increased to 500% without any decrease in the tensile strength. The differential scanning calorimeter (DSC) results reveal that cold crystallization of PLA was enhanced due to heterogeneous nucleation effect of the in situ compatibilized PBAT domains. As known before, PLA is sensitive to hydrolysis and in the presence of PBAT and the chain-extenders, the hydrolytic degradation of the blend was evident. A three-stage hydrolysis mechanism for the system is proposed based on a study of weight loss and molecular weight reduction of the samples and the pH variation of the degradation medium.

Crystallization behavior and morphology of polylactide and PLA/clay nanocomposites in the presence of chain extenders

AbstractThe effect of clay and chain extender on the nonisothermal, isothermal crystallization kinetics, and morphology of polylactide (PLA) was investigated in this study. PLA and PLA‐based nanocomposites containing 2 wt% organoclay were prepared via melt compounding. Three commercially available chain extenders were used: polycarbodiimide (PCDI), tris(nonylphenyl) phosphite (TNPP), and Joncryl ADR4368F. The nanoclay particles were found to act as nucleating agents. Chain extender incorporation, however, had diverse effects on both crystallization rate and degree of crystallinity. Nonisothermal DSC results revealed that the addition of PCDI increased the cold‐crystallization temperature (Tc) from 106 to 114°C, reduced the degree of crystallinity from 6.3 to 5.3%, and resulted in the formation of bimodal melting peaks in PLA. On the other hand, the reduction of chain ends in the presence of TNPP resulted in a significant increase of the crystallization rate and degree of crystallinity from 6.3 to 15.2%. In the case of Joncryl, its incorporation led to the formation of a long‐chain branching structure, which disrupted the chain packing. Therefore, the degree of crystallinity (from 6.3 to 1.6%) and the rate of crystallization decreased, while Tc was increased from 106 to 122°C in the presence of Joncryl. POLYM. ENG. SCI., 2013. © Society of Plastics Engineers

Chain extension of poly (ethylene terephthalate) by reactive extrusion with secondary stabilizer

Poly(ethylene tereftalate) (PET) is a polymer highly susceptible to the hydrolytic reactions that occur during applications and mainly in thermomechanical processing. These reactions lead to the decrease of molecular weight of the polymer, limiting the recycling number of the material. The reactive extrusion of the PET in presence of chain extenders is an alternative to recover mechanical and rheological properties that were depreciated by the polymer degradation. In this study, PET wastes from nonwoven fabrics production were extruded in presence of the secondary stabilizer Irgafos 126 (IRG) on variable concentrations. The results showed that Irgafos 126 increased molecular weight, decreased crystallinity and changed processing behavior of the PET, similarly to the effects produced by the well-known chain extender pyromellitic dianhydride (PMDA), showing that the secondary stabilizer Irgafos 126 can also act as a chain extender for the PET.

Polyurethane Microcellular Elastomers. 3. Effect of Chain Extenders and Blowing Agent on the Foam Formation Kinetics

The influence of (Methylene glycol, ethylene glycol, 1, 4 butanediol as well as of water on the height and rate of rise and temperature during the foaming process of microcellular elastomers used in RIM technology has been studied. The presence of chain extenders in the foaming process leads to an increased mass reactivity of the system. Up to a certain water concentration, the chain extender process is predominant. At higher H 2 O concentrations the blowing reaction is the more significant process.