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A new concept for the controlled chain‐extension of lignin has been developed. A mixture of trioxane as formaldehyde source, resorcinol as chain extender, and lignin allows to prepare high molecular weight precursor fibers by melt‐spinning, which can be spun on a semitechnical scale. Chain extension with resorcinol bridged by methylene groups is achieved during the stabilization process of the precursor fiber. After carbonization, carbon fibers (CFs) with an average diameter of 18 µm show an average tensile strength of 0.78 GPa and a Young's modulus of 106 GPa. A maximum tensile strength of 2.44 GPa and a Young's modulus of 294 GPa are reached with fibers 9.7 µm in diameter. [ABSTRACT FROM AUTHOR]

Poly (butylene adipate-co-terephthalate) (PBAT) foam is a green and promising candidate to replace traditional oil-based polymer foam in the fields of buffer packaging, sporting goods and biomedicine, because of its admirable toughness, good resilience properties and excellent biodegradability. Herein, a novel methodology using the combination of autoclave foaming and vacuum foaming was reported to prepare chain-extended PBAT (CPBAT)/graphene nanosheets (GNPs) microcellular foams with high volume expansion ratio (VER). Compared with that prepared by single autoclave foaming, PBAT microcellular foams prepared by the combination of autoclave foaming and vacuum foaming possessed a higher VER up to 7.60, which had an increase of 324.58%. GNPs were used for the achievement of the filling modification of PBAT, which increased the cell density and compression properties of PBAT foams. When GNPs content were 2 phr, the compressive strength of CPBAT/GNPs2 foam reached 0.82 MPa. Above all, this research will provide a new facile approach to prepare biodegradable microcellular polymer foams with high VER. [ABSTRACT FROM AUTHOR]

In this work, a one-step reactive extrusion method was adopted to improve comprehensive properties of poly(butylene adipate-co-terephthalate) (PBAT) by melt blending with two chain extenders, including polycarbodiimide (PCDI) and multi-functional epoxy polymer (ADR). Their influences on rheological behaviors, aging properties, and thermal stability of PBAT were explored, and the detailed mechanisms were also discussed. It was found that the terminal carboxyl content of PBAT decreased with addition of PCDI and ADR. When 1.0 wt% PCDI was added, the terminal carboxyl content deceased by 70.3%. This indicated that the reaction between the two chain extenders and the terminal hydroxyl and carboxyl groups of PBAT enhanced to perform the chain extension, which increased the molecular weight, storage modulus, loss modulus, and complex viscosity of PBAT, and different relaxation processes were observed for different samples by Han and Cole–Cole plots. Damp-heat aging resistance measurements showed correlation with terminal carboxyl content in PBAT. And reducing the terminal carboxyl content in PBAT was shown to increase hydrolytic stability. For PBAT with 1.0 wt% PCDI blend, the tensile strength and elongation at break retention were above 70%. In addition, the thermal stability of PBAT was also improved due to the chain extension in the blends, which retarded degradation. The analysis results indicated that the comprehensive performance of modified PBAT was the best when 1.0 wt% PCDI was added. [ABSTRACT FROM AUTHOR]

Roller chain drives are frequently applied in a variety of machinery for mechanical motion and power transmission. The roller engagement location on the sprocket tooth contour and the resulted contact behavior is governed by the wear of components and pretension of the chain. Therefore, the influence of extension of chain resulted from wear and pretension of chain on contact behavior was investigated numerically using explicit dynamics module of ABAQUS software. The contact angles evaluated from the numerical simulation were assessed relative to those obtained from the basic rigid body analytical formulation. The chain elongation of 3% increased the maximum contact force up to 52% during engagement with the driver sprocket. The contact force raised to 400% when the pretension in the chain drive was increased from 200 to 1000 N, leaving the force distribution pattern unaltered. The optimal design of a steel sprocket is realized through equivalent static finite element contact analysis of a sprocket engaged with 3% extended roller chain. The dynamic finite element analysis in conjunction with topology optimization reduced the weight of the sprocket by 24%. [ABSTRACT FROM AUTHOR]

The widespread utilization of nonrenewable fossil-based polymers has led to significant environmental damage. Bio-based Poly(lactic acid) (PLA) has garnered substantial academic and industrial interest in the last two decades due to its advantageous characteristics for food packaging applications. Nonetheless, the improper disposal of PLA continues to contribute to the plastic waste problem. PLA recycling mainly involves thermal processes, facing challenges due to PLA's limited stability. This study aims to enhance PLA's molecular weight and melt viscosity by using chain extenders to increase its degree of branching. A modular chain extender capable of thermally forming highly reactive ketene intermediates is employed to react with PLA's hydroxyl and carboxyl end groups in a single step. For this purpose, copolymers of styrene and 2,2,5-trimethyl-5-(4-vinylbenzyl)-1,3-dioxane-4,6-dione were synthesized using free radical polymerization and characterized through 1H-NMR, TGA, and DSC analyses. The chemical interaction between these chain extenders and molten PLA was also explored, resulting in increased PLA molecular weight and higher melting temperature (Tm), reaching 155.1 for PLA_2.5CE2. Additionally, the branching introduced through this process led to a notable increase in the UV absorption of PLA, suggesting potential applications in the packaging industry. The chemical tunability of this functional ketene-based chain extender holds promise for tailoring PLA's structure for diverse applications, further advancing its sustainability and utility. [ABSTRACT FROM AUTHOR]

Poly(butylene adipate-co-terephthalate) (PBAT) foam is regarded as one of the ideal alternatives to petroleum-based polymer foams in view of its advantages of lightweight, high elasticity, biodegradability and biocompatibility, while the problem of shrinkage after foaming has seriously limited its application in industry. In this paper, the no-shrinkage chain-extend PBAT-glycerin monostearate (GMS) foams with ultra-high volume expansion ratio (VER) were prepared by scCO2-assisted molten foaming method. The chain extension reaction between PBAT and chain extender (CE) were investigated by torque curves, gel fraction and FTIR measurements. Comparing with torqued PBAT, the storage modulus of CE-PBAT2 specimen increased 3 orders of magnitude and their crystallization temperature rose from 72.5 to 87.2 ℃. Furthermore, the addition of GMS was beneficial to enhance the dimensional stability of CE-PBAT foams. When 2 phr CE and 2.5 phr GMS were incorporated into PBAT, CEPBAT-GMS2.5 foam attained ultra-high VER of 25.38 times, resilience ratio of 87% with no-shrinkage, which revealed admirable compression and resilience properties. In conclusion, this study provided a feasible new method for improving the VER and dimensional stability of PBAT foams. [ABSTRACT FROM AUTHOR]

PGA is currently getting great attention as a potential biodegradable polymer due to its biodegradability, high gas barrier, and high thermal stability; however, its low processability and brittleness are key factors to be overcome for various applications. The purpose of this study was to investigate the feasibility of poly(glycolic acid) (PGA) as a packaging material for a bio-based poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) blend with improved properties. The optimized PLA/PBAT blend composition was determined with balanced mechanical properties along with microstructural observation. The PGA was first modified with a chain extender to improve its processability, and then it was introduced to PLA/PBAT blends with various compositions via the melt processing method. The melt strength of PGA was found to be improved about 90% with the addition of 0.5 phr of chain extender, achieving better processability. The Young's modulus and tensile strength of the PLA/PBAT/mPGA blend showed no statistically significant differences, which is an interesting finding as compared to other ternary blend system. For barrier properties, the O2 and H2O permeabilities showed no statistically significant difference among ternary blends except the PLA/PBAT blend, but H2O permeability showed a decrease tendency with a value of about 27% as compared to the PLA/PBAT blend. In addition, the morphological observation was also performed to assess the structure-properties relationship in the multi-phase blends system. [ABSTRACT FROM AUTHOR]

Poly(ethylene terephthalate) (PET) is a widely used thermoplastic polymer with exceptional properties, making it a cornerstone in various industries. However, the extensive global demand for PET, particularly in the packaging sector, has led to significant ecological concerns due to inadequate recycling rates. This paper explores the potential of Meldrum's acid-based chain extenders as a solution to enhance PET recycling. Initially, 2,2,5-trimethyl-5-(4-vinylbenzyl)-1,3-dioxane-4,6-dione (St-MA) was synthesized, and its homopolymers were produced through free radical polymerization and characterized through 1H NMR, FTIR and TGA analyses. Dynamic interactions between recycled PET (rPET) and the synthesized chain extender (HP) in an extrusion environment was further explored, resulting in higher Tg and Tc for rPET when 0.5 wt% of HP was added as a reactive chain extender. The chemical tunability of this functional ketene-based chain extender holds promise to enhance PET recycling practices. The continuous evolution of regulatory frameworks and environmental concerns may prompt the exploration of novel approaches, such as tailored Meldrum's acid-bearing chain extenders, which might have the potential to reduce the ecological consequences associated with post-consumer PET waste. [ABSTRACT FROM AUTHOR]

As a completely degradable material, poly(glycolic acid) (PGA) has excellent rigidity, barrier properties, degradability and biocompatibility. However, the inherent brittleness and easily hydrolysable characteristics limit its widespread application. Herein, we introduced chain extension ADR to modify PGA to ameliorate these defects. The results showed that ADR could react with PGA to form "comb‐like" and "cross‐linked" chain extension structures resulting in the improvement of complex viscosity and formation of gel. Because of the chain entanglement of chain extension structures, the toughness of modified PGA was improved (which was verified by the impact strength value of 4.3 kJ/m2 that was about 126% of virgin PGA) without sacrificing its rigidity. Furthermore, the hydrolysis results indicated that the representative PGA/1.0ADR had better hydrolysis stability, it had more complete morphology and slower degradation rate than virgin PGA in the 17‐day hydrolysis experiment. Apart from better toughness and hydrolysis stability, there was also improvements in crystallization performance, the sample PGA/1.0ADR endowed with higher crystallization peak temperature (2.3°C higher than virgin PGA) and lower crystallization activation energy. In short, this work prepared a kind of modified PGA with rigidity toughness balance and better hydrolysis stability, which could expand the application range of PGA‐based materials. [ABSTRACT FROM AUTHOR]

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract The thermo-mechanical degradation of PET during extrusion was studied in the transient state. Active agents, water, causing hydrolysis by chain scission and pyromellitic dianhydride PMDA, causing chain extension, were added to the extrusion flow as pulses. They change the PET molecular weight, affecting its the melt flow elasticity, which was followed in-line by a rheo-optical detector set in an instrumented slit-die, measuring synchronously, pressure drop and flow birefringence ( Δ n 12). The effect of the extrusion shearing level, set by 90º kneading blocks with different lengths, was also quantified. The results, as of residence time distribution curves, show the degree of thermo-mechanical degradation as hydrolysis and chain extension for each pulse type and concentration. Thus, assuming collinearity and full birefringence orientation along the melt flow the first normal stress difference N 1 can be monitored in-line.

Long carbon chain thermoplastic polyamide elastomer (TPAE) with PA1212 as hard segment and polytetrahydrofuran as soft segment was synthesized successfully. Subsequently, thermoplastic polyurethane (TPU) incorporated to compensate for the high cost of TPAE and improved the foaming performance, in which a chain extender (ADR) was applied to enhance melt strength and interfacial compatibility simultaneously. The effect of ADR content on the mechanical, thermal, rheological, and foaming properties of TPAE/TPU composites were investigated in detail. It was found that the composite foams showed a more perfect cell structure, high cell density, and increased expansion ratio because of the enhanced melt strength and interfacial compatibility, when ADR was incorporated. With the increase of ADR content, the cell size and expansion ratio of the composite foams with TPU content of 30% showed a trend of first increasing and the following decreasing. The cell size reached a maximum value when the content of ADR was 2%, which was 25.81 μm. Consequently, the obtained TPAE/TPU composite foams showed an outstanding compressive modulus and resilient performance to broaden its application in footwear industry. [ABSTRACT FROM AUTHOR]

Functional crosslinked hydrogels were prepared from 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA). The acid monomer was incorporated both via copolymerization and chain extension of a branching, reversible addition–fragmentation chain-transfer agent incorporated into the crosslinked polymer gel. The hydrogels were intolerant to high levels of acidic copolymerization as the acrylic acid weakened the ethylene glycol dimethacrylate (EGDMA) crosslinked network. Hydrogels made from HEMA, EGDMA and a branching RAFT agent provide the network with loose-chain end functionality that can be retained for subsequent chain extension. Traditional methods of surface functionalization have the downside of potentially creating a high volume of homopolymerization in the solution. Branching RAFT comonomers act as versatile anchor sites by which additional polymerization chain extension reactions can be carried out. Acrylic acid grafted onto HEMA–EGDMA hydrogels showed higher mechanical strength than the equivalent statistical copolymer networks and was shown to have functionality as an electrostatic binder of cationic flocculants. [ABSTRACT FROM AUTHOR]

The preparation of biodegradable polymer foams with a stable high volume-expansion ratio (VER) is challenging. For example, poly (butylene adipate-co-terephthalate) (PBAT) foams have a low melt strength and high shrinkage. In this study, polylactic acid (PLA), which has a high VER and crystallinity, was added to PBAT to reduce shrinkage during the supercritical molded-bead foaming process. The epoxy chain extender ADR4368 was used both as a chain extender and a compatibilizer to mitigate the linear chain structure and incompatibility and improve the foamability of PBAT. The branched-chain structure increased the energy-storage modulus (G') and complex viscosity (η*), which are the key factors for the growth of cells, by 1–2 orders of magnitude. Subsequently, we innovatively used the CO2 and N2 composite gas method. The foam-shrinkage performance was further inhibited; the final foam had a VER of 23.39 and a stable cell was obtained. Finally, after steam forming, the results showed that the mechanical strength of the PBAT/PLA blended composite foam was considerably improved by the addition of PLA. The compressive strength (50%), bending strength, and fracture load by bending reached 270.23 kPa, 0.36 MPa, and 23.32 N, respectively. This study provides a potential strategy for the development of PBAT-based foam packaging materials with stable cell structure, high VER, and excellent mechanical strength. [ABSTRACT FROM AUTHOR]

In this work, photoinduced thiol‐epoxy click reaction for side‐chain functionalization, chain‐extension, grafting, and cross‐linking of polymers prepared by atom transfer radical polymerization by using 1,5‐diazabicyclo[5.4.0]undec‐5‐ene thioxanthone acetate (Tx‐DBU) as a photo base generator (PBG) is described. Irradiation of Tx‐DBU at 365 nm leads to the generation of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) in neutral form as a super base. DBU is capable of abstracting protons from thiols and thus formed thiolates are excellent nucleophiles that exhibit high affinity toward electrophiles such as epoxide rings. Appropriately selected thiols are successfully used for the desired reactions. The precursors and resulting polymers are characterized using 1H‐NMR, Fourier transform infrared, gel permeation chromatography, and differential scanning calorimetry measurements. This study shows that the use PBGs can further be extended to the synthesis of various complex macromolecular structures by the described post modification processes. [ABSTRACT FROM AUTHOR]

The comprehensive balance of the mechanical, interfacial, and environmental requirements of waterborne polyurethane (WPU) has proved challenging, but crucial in the specific application as the binder for high-performance polymer fiber composites. In this work, a multi-step chain extension (MCE) method was demonstrated using three kinds of small extenders and one kind of macro-chain extender (CE) for different chain extension steps. One dihydroxyl blocked small molecular urea (1,3-dimethylolurea, DMU) was applied as one of the CEs and, through the hybrid macrodiol/diamine systems of polyether, polyester, and polysiloxane, the WPU was developed by the step-by-step optimization on each chain extending reaction via the characterization on the H-bonding association, microphase separation, and mechanical properties. The best performance was achieved when the ratio of polyether/polyester was controlled at 6:4, while 2% of DMU and 1% of polysiloxane diamine was incorporated in the third and fourth chain extension steps, respectively. Under the condition, the WPU exhibited not only excellent tensile strength of 30 MPa, elongation of break of about 1300%, and hydrophobicity indicated by the water contact angle of 98°, but also effective interfacial adhesion to para-aramid fabrics. The peeling strength of the joint based on the polysiloxane incorporated WPU after four steps of chain extension was 430% higher than that prepared through only two steps of chain extension. Moreover, about 44% of the peeling strength was sustained after the joint had been boiling for 40 min in water, suggesting the potential application for high-performance fabric composites. [ABSTRACT FROM AUTHOR]

Medium-chain carboxylic acids (MCCAs) show great promise as commercial chemicals due to their high energy density, significant product value, and wide range of applications. The production of MCCAs from waste biomass through coupling chain extension with anaerobic fermentation represents a new and innovative approach to biomass utilization. This review provides an overview of the principles of MCCAs production through coupled chain extension and anaerobic fermentation, as well as the extracellular electron transfer pathways and microbiological effects involved. Emphasis is placed on the mechanisms, limitations, and microbial interactions in MCCAs production, elucidating metabolic pathways, potential influencing factors, and the cooperative and competitive relationships among various microorganisms. Additionally, this paper delves into a novel technology for the bio-electrocatalytic generation of MCCAs, which promotes electron transfer through the use of different three-dimensional electrodes, various electrical stimulation methods, and hydrogen-assisted approaches. The insights and conclusions from previous studies, as well as the identification of existing challenges, will be valuable for the further development of high-product-selectivity strategies and environmentally friendly treatments. [Display omitted] • The extracellular electron transfer pathway of producing MCCAs is summarized. • A new technique of bioelectrocatalytic generation of MCFAs is introduced. • MCFA provides a new research direction for the energisation of waste resources. • Highlighting several strategies for efficient MCFA extraction. [ABSTRACT FROM AUTHOR]

The effect of adding maleinized low-molecular-mass polybutadiene rubber on the structure and mechanical properties of polyamide 6 and its composites with the initial and organophilized montmorillonite was studied. The composites were prepared by compounding in a melt in a two-worm extruder. Specimens for the studies were prepared by pressure casting. The structure and properties of the composites were studied by differential scanning calorimetry, X-ray diffraction analysis, dynamic mechanical analysis, and mechanical tests. Modification of the polyamide by adding maleinized rubber increases the strength, the tensile and bending elastic moduli, the extension stress, and the relative elongation at break. Structural changes are manifested in a decrease in the melt flow index by 2 orders of magnitude and in the mechanical loss tangent at temperatures exceeding the glass transition point. These changes suggest an increase in the molecular mass of the polymer. When montmorillonite and maleinized rubber are added jointly, the character of changes in the rheological and strength characteristics of the nanocomposites is similar to that observed in modification of unfilled polyamide 6. According to the data of X-ray diffraction analysis and scanning electron microscopy, in processing of melts of the modified composites the degrees of the clay exfoliation and of the clay particle orientation increase. This ensures an additional increase in the bending elastic modulus and bending strength compared to the corresponding tensile characteristics due to predominantly normal orientation of clay particles relative to the bending stress. [ABSTRACT FROM AUTHOR]

The structure, morphology, fracture toughness and flaw sensitivity length scale of chain-extended poly(butylene succinate) with various pre-stretch ratios were studied. PBS modification adopted from a multifunctional, commercially available chain-extension containing nine epoxy groups (ADR9) as the first step chain extension and hydroxyl addition modified dioxazoline (BOZ) as the second step. Time-temperature superposition (TTS) studies show that the viscosity increased sharply and the degree of molecular branching increased. Fourier transform infrared spectroscopy (FT-IR) confirm successful chain extension reactions. The orientation of the polymer in the pre-stretch state is such that spherulites deformation along the stretching direction was observed by polarized light optical microscopy (PLOM). The fracture toughness of sample (λfix = 5) is Γ ≈ 106 J m-2 and its critical flaw sensitivity length scale is Γ/Wc ≈ 0.01 m, approximately 5 times higher than PBS without chain-extension (Γ ≈ 2 × 105 J m-2 and Γ/Wc ≈ 0.002 m, respectively). The notch sensitivity of chain-extended PBS is significantly reduced, which is due to the orientation of spherulites more effectively preventing crack propagation. The principle can be generalized to other high toughness material systems. [ABSTRACT FROM AUTHOR]

Polyphenylene sulfide (PPS) is a type of thermoplastic that has high thermal and mechanical performances and extensive applications. Before processing, pre‐curing is required to improve its processability and mechanical properties. Here, effects of curing temperature (245 and 260°C) and time (10, 30, 60, and 120 min) on structure and thermal‐mechanical behavior of PPS were studied through melt flow index (MFI), rheology, Fourier‐transform infrared spectroscopy, and thermal‐mechanical characterizations. The MFI was decreased from ~700 g/10 min to less than 100 g/10 min (315°C/5.0 kg) after 60 min of curing at two different temperatures, greatly improving the processability of PPS in melt extrusion and injection molding processes. The functional groups remained unchanged after curing, due to the main reactions of chain extension and scission that occurred. For the PPS cured both at 245 and 260°C, the samples cured for 10 min displayed the highest degree of crystallinity and heat deflection temperature but had the lowest glass transition temperatures. The coefficient of linear expansion of PPS cured at 260°C showed anisotropy on flow and normal directions, which greatly differed from the PPS cured at 245°C. This study promotes an improved understanding of the curing process for solid PPS. [ABSTRACT FROM AUTHOR]

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.

Aqueous Polyurethane Dispersions (APUD) have been at the epicenter of the coating industry & research, devising greener solutions to modern coating problems. The formulation of APUDs involves many components namely, polyols, isocyanates, chain extenders, and ionic centers which enable the Polyurethane to be dispersed in water. This reduces the dependence on solvent-based coatings, providing a better and eco-friendly replacement for existing systems. Advantages like ambient temperature curing and excellent adhesion further reinforce the case for APUD. This review encompasses the synergistic effect of said components while painting a vivid picture of how they would affect the final properties of the coating.

Functional crosslinked hydrogels were prepared from 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA). The acid monomer was incorporated both via copolymerization and chain extension of a branching, reversible addition–fragmentation chain-transfer agent incorporated into the crosslinked polymer gel. The hydrogels were intolerant to high levels of acidic copolymerization as the acrylic acid weakened the ethylene glycol dimethacrylate (EGDMA) crosslinked network. Hydrogels made from HEMA, EGDMA and a branching RAFT agent provide the network with loose-chain end functionality that can be retained for subsequent chain extension. Traditional methods of surface functionalization have the downside of potentially creating a high volume of homopolymerization in the solution. Branching RAFT comonomers act as versatile anchor sites by which additional polymerization chain extension reactions can be carried out. Acrylic acid grafted onto HEMA–EGDMA hydrogels showed higher mechanical strength than the equivalent statistical copolymer networks and was shown to have functionality as an electrostatic binder of cationic flocculants.

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As an important biodegradable polymer, how to achieve stable cell morphology and high cell density in the foam of poly(butylene adipate-co-terephthalate) (PBAT) is challenging due to its low mechanical and melt strength. To address this issue, an innovative methyl methacrylate-co-glycidyl methacrylate (MG) copolymer was designed and used as a chain extender due to its strong affinity with carbon dioxide (CO 2) during the supercritical CO 2 foaming process. The branching reaction between the carboxyl end groups of PBAT and the epoxy groups in MG enhanced the molecular weight, melt strength, and mechanical properties of PBAT. Therefore, the introduction of MG resulted in a reduced cell size, higher cell density, stronger compression stress for the foamed PBAT. The results prove that the MG copolymer is an effective chain extender for PBAT, which is beneficial to improve the foaming process and properties of PBAT for its application as package cushioning material. [Display omitted] • MG chain extenders extend the PBAT molecular chain with little or no crosslinking. • MG copolymers exhibit an affinity for CO2, rendering the foaming process very favorable. • The cell density of PBAT/MG6 foam is enhanced to 6.1 ×107 cells/cm3 and the retention rate of CO 2 is nearly doubled. [ABSTRACT FROM AUTHOR]

In this research work, both natural weathering and artificial weathering processes were carried out to investigate the effects of multi-functional epoxy chain extender (Joncryl ADR 4370) content on the degradation and the mechanical properties and molecular weight of poly(butylene adipate-co-terephthalate) (PBAT). The carboxyl end-groups of PBAT decreased significantly with an increase in ADR content from 0 to 1.5 wt%. Similarly, the molecular weight of PBAT initially increased and then decreased because of the formation of a crosslinked network structure under the influence of excessive chain extenders. The main degradation mechanism of PBAT during the natural and artificial weathering process is photo-degradation and hydrolyzation. The degradation rate of PBAT increased with increasing content of chain extender, as hydroxyl groups facilitate the water attack on the ester bonds of PBAT. In contrast, the higher content of chain extender presented the lower loss velocity of the tensile strength. This is mainly because the more ADR content, the more crosslinking network structures will be formed during the melting extrusion which can slow down the decrease of tensile strength. Hence, it is indicated that the crosslinking structure has more effect on tensile strength than that of hydrolysis effect during degradation. According to the analysis and study on the performance changes of PBAT/ADR materials under the conditions of long-term natural weathering (360d) and artificial weathering (600 h), this work provides theoretical guidance to produce PBAT mulching films with excellent performance.

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Copyright of Journal of Tiangong University is the property of Journal of Tianjin Polytechnic University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The demand for processing recycled acrylonitrile‐butadiene‐styrene copolymer plastics (R‐ABS) grows fast. Herein, epoxidized styrene‐butadiene‐styrene (ESBS) with reactive groups including polybutadiene (PB) phase, epoxidized polybutadiene (EPB) phase and polystyrene phase is prepared by modifying SBS with an in situ peroxyformic acid method. Both chain extension and phase interface reparation of R‐ABS are successfully reported by simple melt blending. Compared with R‐ABS, when ESBS content is 15 wt%, the average molecular weight (Mw) of the ESBS/R‐ABS is increased from 118.01 to 612.51 kDa. The particle size of the dispersed phase is decreased obviously. The compatibility between these two phases became better. The average notch impact strength of R‐ABS is 5.72 kJ m−2. When the ESBS content is 15 wt%, the average notch impact strength of ESBS/R‐ABS reaches 13.90 kJ m−2, which is increased by 143% compared with that of R‐ABS. The notch impact strength of ESBS/R‐ABS is close to that of virgin ABS. The reported high‐value usage of R‐ABS has a great potential for industrial‐scale applications. [ABSTRACT FROM AUTHOR]

Copyright of Journal of East China University of Science & Technology is the property of Journal of East China University of Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Halogen exchange in atom transfer radical polymerization (ATRP) is an efficient way to chain‐extend from a less active macroinitiator (MI) to a more active monomer. This has been previously achieved by using CuCl/L in the equimolar amount to Pn−Br MI in the chain extension step. However, this approach cannot be effectively applied in systems based on regeneration of activators (ARGET ATRP), since they operate with ppm amounts of catalysts. Herein, a catalytic halogen exchange procedure is reported using a catalytic amount of Cu in miniemulsion ARGET ATRP to chain‐extend from a less active poly(n‐butyl acrylate) (PBA) MI to a more active methyl methacrylate (MMA) monomer. Influence of different reagents on the initiation efficiency and dispersity is studied. Addition of 0.1 m NaCl or tetraethylammonium chloride to ATRP of MMA initiated by methyl 2‐bromopropionate leads to high initiation efficiency and polymers with low dispersity. The optimized conditions are then employed in chain extension of PBA MI with MMA to prepare diblock and triblock copolymers. [ABSTRACT FROM AUTHOR]

In this article, a facile and efficient isothermal crystallization induction method was proposed to fabricate microcellular poly(butylene succinate) (PBS) foams with supercritical CO2. The good regularity of PE chain segments and high reactive epoxy groups in ethylene‐glycidyl methacrylate copolymer (PE‐g‐GMA) serving as a chain extender were employed to improve the crystallization behaviors, viscoelasticity, and foaming behaviors of PBS through chain extension reaction. The effect of PE‐g‐GMA content on the thermal properties, rheological performances, and cellular morphology of various PBS samples was investigated systematically. When the PE‐g‐GMA content switched from 7.5 to 10 wt %, an interesting transition from fine cells to microcells was observed in PBS/PE‐g‐GMA foams. Microcellular PBS foam modified by 10 wt % PE‐g‐GMA was successfully prepared at the foaming temperature of 87 °C and the induction time of 7 min, in which its cell size and cell density could reach 6.63 ± 1.93 μm and 3.75 × 109 cells cm−3, respectively. The formation of abundant but tiny spherocrystals in chain extended PBS samples made a considerable contribution for preparing microcellular PBS foams. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48850. [ABSTRACT FROM AUTHOR]

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The brittleness of poly(L-lactide) (PLLA) bioplastic is the main disadvantage for practical applications. Herein, we report the synthesis of high-molecular-weight PLLA- b -poly(ethylene glycol)- b -PLLA (PLLA-PEG-PLLA) block copolymers by ring-opening polymerization of LLA. The highly flexible PLLA-PEG-PLLAs were prepared by reactive melt blending with an epoxy-based chain extender formed as long-chain branched structures. The effects of PEG block length and content of chain extender were investigated. The results showed that the chain extension reaction reduced crystallinities of the PLLA-PEG-PLLAs. All the chain-extended PLLA-PEG-PLLA films had no phase separation. The lower crystallinities of PLLA-PEG-PLLA films obtained with higher contents of chain extender enhanced the film drawability. The longer PEG block length resulted in higher strain at break and lower stress at the break of PLLA-PEG-PLLA films. These chain-extended PLLA-PEG-PLLAs have potential for use as highly flexible bioplastics. [ABSTRACT FROM AUTHOR]

Most polymers used in coatings are thermosetting resins because of their good adhension, protective capability, thermal and mechanical properties. Prepolymerization is a common procedure in the application of thermosetting resins, in order to adapt the specific processing condition, processing equipment or to achieve desired performance. However, the effects of prepolymerization on the curing behavior, chemical structure and properties of the resultant resins haven't been systematically studied. Among various thermosetting resins used as coatings, benzoxazine is a relatively new member, but it is being intensively studied due to its good processability, adhesive strength, low water absorption, as well as good anticorrosive property. Hence, in this work, 1,3-benzoxazine, a kind of high-performance thermosetting resin, was used as an example to probe the influence of prepolymerization. The chemical structure variation was characterized, the curing activity and the rheological behavior were investigated, and the thermal, mechanical and dielectric properties of the resultant polymers were also studied. It was found that the content of benzoxazine groups decreased while the molecular weight and the melt viscosity increased with prelonged prepolymerization time, which may release more active phenolic hydroxyls that could promote the curing of benzoxazine, but also caused worse molecular moveability. The glass transition temperature, initial decomposition temperature and char yield of most polymers decreased consequently, with few exceptions. However, the mechanical property was improved, as suggested by higher tensile strength and elongation at break value after prepolymerization. [Display omitted] • 1,3-benzoxazine was used as an example to probe the influence of prepolymerization; • Prepolymerization led to consumption of functional groups, increased molecular weight and higher melt viscosity; • Prepolymerization led to lower crosslinking density; • Prepolymerization led to lower glass transition temperature; • Prepolymerization led to higher mechanical strength. [ABSTRACT FROM AUTHOR]

In recent years, poly(lactic acid) (PLA) foams have drawn considerable attention worldwide due to their environmental friendliness and excellent biocompatibility. However, it was a big challenge to prepare PLA foams with high volume expansion ratio owing to their poor crystallization properties and melt strength. In this work, the random copolymer of ethylene and glycidyl methacrylate as an efficient chain extender (CE) was chosen and employed to improve the crystallization behaviors and foamability of PLA. The chain extension reaction between PLA and CE was proved by torque curves, Fourier transform infrared spectra, gel fraction, and intrinsic viscosity measurements. Differential scanning calorimetry results and polarized optical microscope images showed that the crystallinity and spherocrystal number of various PLA samples increased notably as well as their spherocrystal size decreased with the CE content increasing. The viscoelasticity of various PLA samples was improved by the increment in the CE content. Various PLA samples were foamed by a batch foaming method at different foaming temperature with supercritical CO2 to research the influence of crystallization behaviors and/or rheological properties on the foaming behaviors of PLA. At the high foaming temperature, the cell density and volume expansion ratio (VER) of various PLA foams were affected by rheological properties significantly and their highest VER could reach to 42.41 ± 0.01 times. At the low foaming temperature, the cellular morphology of various PLA foams was improved notably, due to the increased melt strength induced by the cooling and the generation of crystallization region. [ABSTRACT FROM AUTHOR]

Currently, the fabrication of microcellular semi-crystalline polymer foams using supercritical CO 2 as a blowing agent had attracted worldwide interest. In this paper, a novel and facile isothermal crystallization induction method was proposed to prepare biodegradable microcellular semi-crystalline poly (butylene succinate) (PBS) foams by supercritical CO 2. In order to improve melt viscoelasticity and increase cell nucleation number, chain extender (CE) and polyhedral oligomeric silsesquioxane (POSS) were introduced into PBS through melt blending method. Differential scanning calorimetry results showed that with the addition of CE and POSS, the crystallization temperature of various PBS samples increased and their crystallinity kept unchanged almost. Compared with those of pure PBS, the complex viscosity and storage modulus of chain extended PBS (CPBS), PBS/POSS and CPBS/POSS increased. The effect of chain extension, POSS addition and induction time on the foaming performance of various PBS samples was studied systematically. Microcellular CPBS/POSS foam was successfully fabricated at the induction time of 18 min and foaming temperature of 90 °C, in which the cell size and volume expansion ratio could reach 6.80 ± 1.21 μm and 7.48 ± 0.03 times, respectively. Finally, the formation mechanism of various PBS foams by isothermal crystallization induction method was presented and the thermal conductivity of various PBS foams was investigated. • A novel and facile isothermal crystallization-induced method was proposed to prepare microcellular PBS foams. • Chain extender and POSS were added into PBS to improve melt viscoelasticity and generate abundant but tiny spherocrystals. • Microcellular CPBS/POSS foam was fabricated successfully at the induction time of 18 min and foaming temperature of 90 °C. • With the induction time increasing, a transition from ordinary cells to microcells could be observed in CPBS/POSS foam. • The foaming mechanism for forming microcells in various PBS foams was proposed and explained by schematic diagram. [ABSTRACT FROM AUTHOR]

Isothermal and nonisothermal crystallization kinetics of poly(l -lactide) and its nanocomposites with different multiwalled carbon nanotubes (i.e., pristine and functionalized) were investigated. The effects of chain extension and nanofiller content on the crystallization kinetics were also explored. The Avrami analysis was applied as a useful tool for the study of isothermal crystallization kinetics, which was also supported by optical microscopy observations. In addition, in nonisothermal crystallization process, the Avrami and Mo methodologies were used to study the crystallization kinetics as well as the evaluation of activation energy from isoconversional methods. The activation energy was always negative for the process driven by the secondary nucleation. Great differences were found between the studied samples, but activation energy values indicated a favored crystallization (i.e., less negative energies) when functionalized multiwalled carbon nanotubes were added at a concentration of 0.2 wt%. Cold crystallization was also influenced by the multiwalled carbon nanotube content due to the nucleating effect and the existence of geometrical constrictions that limited the size of crystalline domains. Small-angle X-ray scattering studies showed that the size of crystal lamellae after cold crystallization could vary by a magnitude of 3 nm depending on the way as the sample was previously cooled (i.e., by the presence of incipient crystalline domains). [ABSTRACT FROM AUTHOR]

Thermal stability of dithiobenzoate- (DB) and trithiocarbonate- (TC) terminated poly(methyl methacrylate) (PMMA) synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization is systematically studied under dynamic heating and prolonged isothermal treatment at 100–180 °C. It is demonstrated that in the presence of functional end-groups the onset of mass loss can be shifted relative to conventional PMMA, either toward higher (PMMA-DB) or lower (PMMA-TC) temperatures. Irrespective of the polymer molar mass, a loss of PMMA chain-end functionality clearly manifests itself upon 24 h of isothermal treatment at 120 °C for DB end-groups and already at 100 °C for TC ones. At 120 °C (for PMMA-TC) and 140 °C (for PMMA-DB) the ability of both polymers to serve as macromolecular RAFT agents in the chain extension processes ceases almost completely. The kinetics of functional end-groups elimination depends on their chemical nature. In the case of DB-groups, the reaction is of the first order, whereas TC-groups containing two C S bonds demonstrate more complex degradation kinetics. We propose a two-step mechanism of TC-group elimination, which enables interpretation of the observed experimental data. • Thermal degradation of RAFT-based PMMA starts from end-groups. • Chemical nature of end-groups determines their elimination kinetics. • Thermal stability of RAFT-based PMMA is independent of its molar mass. • Dithiobenzoate-terminated PMMA totally loses end-functionality after 24 h annealing at 140°C. • Trithiocarbonate-terminated PMMA loses its functionality after 24 h annealing at 120°C. [ABSTRACT FROM AUTHOR]

We report the synthesis of high‐molecular‐weight linear polyisobutylenes (PIBs) and PIB networks from low‐molecular‐weight PIB by thiol‐ene click chemistry. Thus, liquid allyl‐telechelic PIB was reacted with small di‐ and tri‐thiols, and the thiolated intermediates chain‐extended by UV‐ or thermally induced free radical initiation to linear and crosslinked products. PIB networks were also prepared by crosslinking SH‐telechelic PIB with a small triallyl compound. Linear products were characterized by 1H NMR spectroscopy and GPC, and networks by FTIR spectroscopy, extractables, swelling, and permanent set. The effect of reaction conditions (nature of thiol chain extender, concentration of photo‐ and thermal initiators, UV radiation time, and reagent concentrations) on chain extension and crosslinking was investigated. Under well‐defined conditions high‐molecular‐weight PIBs and tight PIB networks were prepared. Thiol‐ene click chemistry provides novel thiolated PIB derivatives and is a useful strategy for the convenient preparation of high‐molecular‐weight rubbery PIBs and tight PIB networks from low‐molecular‐weight PIB precursors. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 [ABSTRACT FROM AUTHOR]

Abstract Chain extenders having different structures such as: alternating copolymer of ethylene and maleic anhydride (EMA), multi-functional epoxy-based oligomeric chain extender (EPO), polyester wax with reactive caprolactam groups (CW) and dimeric 2,4-toluene diisocyanate (DTDI), were melt compounded with recycled polyamide6 (rPA6) in various amounts via a twin screw extruder. DTDI, which is generally used for polyurethane applications, was used as a chain extender for rPA6 for the first time. In order to evaluate the effects of chain extender's structural differences on the chain extension behavior of the resulting materials, differential scanning calorimetry (DSC) measurements, heat deflection temperature (HDT) measurements, vicat softening temperature (VST) measurements, relative viscosity measurements and mechanical tests including tensile and impact tests were performed. The results showed that mechanical properties were improved by all chain extenders, however the highest improvement was achieved with EMA. The addition of EMA increased relative viscosity by 41%, HDT 12.4%, elongation at break by 6.3 times and impact strength by 26%. DTDI showed 22% increase in relative viscosity, 10% increase in HDT, 23% increase in impact strength and it also increased elongation at break by 6.1 times, making it a very good chain extender candidate for rPA6. Highlights • Four different types of chain extenders were compared to improve recycled PA6 (rPA6). • The viscosity increased 41% with 1 wt% alternating ethylene-maleic anhydride copolymer (EMA). • Chain extenders were found to improve heat deflection temperature of rPA6. • The highest improvement in impact strength of rPA6 was achieved with EMA. • Dimeric 2,4-toluene diisocyanate demonstrated as a viable option for rPA6. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new method to prepare covalently colored polyurethane latex was developed based on polymerization of dye monomers. • Water-soluble dye monomers were prepared from commercial reactive dyes with facile synthetic procedure. • The conversion rate of dye monomers relied on the relative ratio between isocyanate and dye monomers. Abstract In this work, a new method for facile synthesis of covalently colored polyurethane latex was developed. A series of blue dye monomers were synthesized via one-step reaction of a reactive dye and amino compounds, and then employed as chain extenders to react with polyurethane prepolymer in the emulsification process to prepare the covalently colored polyurethane latexes. The chemical structures and the properties of dye monomers and the corresponding polymers were investigated, and the UV–Vis spectra of covalently colored polyurethane featured fairly consistent with dye monomers with maximum absorption wavelength at 620 nm and 580 nm, since the chemical structure of chromophore maintained unchanged. The conversion of dye monomer reached more than 92% with 1.0 wt% dye content, whereas the conversion decreased with the increase of the dye amount and the adding time. Compared with the noncovalently latex film, the light fastness of the covalently colored latex film was greatly promoted due to the chemical bonding of chromophores with polymer matrix. [ABSTRACT FROM AUTHOR]

In-situ reactive extrusion of PET flakes with MDI. [Display omitted] • PET flakes modified with MDI to promote chain extension. • Process performed using in-situ reactive extrusion as a recycling approach. • Physical properties of the recycled PET were much improved over traditional methods. • The method can be applied in food packaging and other industrial applications. To improve recycled PET (r PET) properties, polyethylene terephthalate (PET) flakes were modified with different ratios of 4,4′-methylene diphenyl diisocyanate (MDI) as a chain extender (CE) using in-situ reactive extrusion. Intrinsic viscosity (IV), chemical bonding, thermal properties, and morphology, which strongly depended on MDI content, were investigated. New amide bonds, an indicator of chemical bonds between PET and MDI, were confirmed in the range 1505–1520 cm−1 by FTIR. Additionally, IV values of r PET with MDI (r PET-Ms) increased from 0.42 to 1.08 dL/g. Furthermore, crystallinity and oxygen barrier properties decreased with increasing MDI content. This may have been caused by hindered crystallization from increased random segments with the addition of MDI. There was lower overall migration than the stipulated overall migration limit (OML) in food simulants. These results suggest that in-situ reactive extrusion modification of PET flakes using MDI can provide value-added upcycled PET as an alternative to virgin PET (v PET). [ABSTRACT FROM AUTHOR]