scholarly journals Soft, Formstable (Co)Polyester Blend Elastomers

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1472
Author(s):  
Axel T. Neffe ◽  
Victor Izraylit ◽  
Paul J. Hommes-Schattmann ◽  
Andreas Lendlein
Keyword(s):  
Crystallization Rate ◽  
Thermoplastic Elastomers ◽  
Sequence Length ◽  
Copolymer Composition ◽  
Medical Applications ◽  
Sequence Structure ◽  
Average Molar Mass ◽  
Elongation At Break ◽  
Polymer Systems ◽  
High Elongation

High crystallization rate and thermomechanical stability make polylactide stereocomplexes effective nanosized physical netpoints. Here, we address the need for soft, form-stable degradable elastomers for medical applications by designing such blends from (co)polyesters, whose mechanical properties are ruled by their nanodimensional architecture and which are applied as single components in implants. By careful controlling of the copolymer composition and sequence structure of poly[(L-lactide)-co-(ε-caprolactone)], it is possible to prepare hyperelastic polymer blends formed through stereocomplexation by adding poly(D-lactide) (PDLA). Low glass transition temperature Tg ≤ 0 °C of the mixed amorphous phase contributes to the low Young’s modulus E. The formation of stereocomplexes is shown in DSC by melting transitions Tm > 190 °C and in WAXS by distinct scattering maxima at 2θ = 12° and 21°. Tensile testing demonstrated that the blends are soft (E = 12–80 MPa) and show an excellent hyperelastic recovery Rrec = 66–85% while having high elongation at break εb up to >1000%. These properties of the blends are attained only when the copolymer has 56–62 wt% lactide content, a weight average molar mass >140 kg·mol−1, and number average lactide sequence length ≥4.8, while the blend is formed with a content of 5–10 wt% of PDLA. The devised strategy to identify a suitable copolymer for stereocomplexation and blend formation is transferable to further polymer systems and will support the development of thermoplastic elastomers suitable for medical applications.

Elastomeric Polycarbonate Block Copolymers

1965 ◽  
Vol 38 (2) ◽  
pp. 431-449
Author(s):  
Eugene P. Goldberg
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Bisphenol A ◽  
Flexural Modulus ◽  
Softening Temperature ◽  
Thermoplastic Elastomers ◽  
Partial Replacement ◽  
Initial Increase ◽  
Copolymer Composition ◽  
Moderate Degree

Abstract Polycarbonate block copolymers were prepared by phosgenating pyridine solutions of polyether glycol-bisphenol-A mixtures. Copolycarbonates derived from poly(oxyethylene) glycols (Carbowaxes) were studied in detail for property-structure effects as a function of glycol molecular weight (1000–20,000) and copolymer composition (5–70 weight per cent or 0.3–10.0 mole per cent of a 4000 molecular weight glycol). Remarkable strength (>7000 psi) and snappy elasticity (>90 per cent immediate recovery) were observed at poly(oxyethylene) block concentrations greater than 3 mole per cent. These thermoplastic elastomers also exhibited high softening temperatures (>180° C) and tensile elongations up to about 700 per cent. Both Tg and softening temperature varied linearly with comonomer mole ratio over the composition range studied, with Tg displaying much greater polyether concentration sensitivity. It is suggested that the observed property effects result to a large extent from the variation in poly(bisphenol-A carbonate) block length that accompanies the changing of copolymer composition. An initial increase in flexural modulus (stiffness) was observed at low polyether concentrations (0–1 mole per cent). This phenomenon is considered to be related to similar modulus effects found in plasticized rigid thermoplastics at low plasticizer concentrations. A moderate degree of molecular order, due to bisphenol carbonate segments rather than the normally crystalline polyether, was detected by x-ray analysis. Elastomeric carbonate-carboxylate tetrapolymers were also prepared by partial replacement of carbonate with isophthalate, terephthalate or adipate linkages in polyether-bisphenol systems. The dramatic softening temperature depression observed in this class of polymers is attributed to the disruption of long bisphenol carbonate block sequences that exist in the simpler polyether glycol-bisphenol carbonate copolymers.

scholarly journals Elastomeric polyethylenes accessible via ethylene homo-polymerization using an unsymmetrical α-diimino-nickel catalyst

2017 ◽  
Vol 8 (18) ◽  
pp. 2785-2795 ◽  
Author(s):  
Xinxin Wang ◽  
Linlin Fan ◽  
Yanping Ma ◽  
Cun-Yue Guo ◽  
Gregory A. Solan ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Nickel Catalyst ◽  
Elastic Recovery ◽  
Nickel Catalysts ◽  
High Thermal Stability ◽  
Elongation At Break ◽  
New Family ◽  
High Elongation

Elastomeric polyethylenes, with good elastic recovery and high elongation at break, have been prepared using a new family of unsymmetrical α-diimino-nickel catalysts that display high activities and high thermal stability.

scholarly journals Maleic Anhydride-Grafted Isotactic Polybutene-1 and Modified Polyamide 6

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 872 ◽  
Author(s):  
Yongxian Zhao ◽  
Chen Ma ◽  
Shijie Cheng ◽  
Wei Xu ◽  
Yuejuan Du ◽  
...  
Keyword(s):  
Maleic Anhydride ◽  
Crystallization Rate ◽  
Polyamide 6 ◽  
Melt Flow Rate ◽  
Elongation At Break ◽  
Melt Grafting ◽  
Relative Molecular Weight ◽  
Two Phases ◽  
Optimized Conditions ◽  
Dsc Curves

Maleic anhydride (MAH)–divinyl benzene (DVB) multi-monomer melt-grafting onto isotactic polybutene-1 (iPB-1) was carried out in a torque rheometer. The effects of dicumyl peroxide (DCP), MAH, and DVB concentrations, and temperature, on the reaction, were investigated. The optimized conditions were 170 °C, DVB/MAH = 4:6 (mass ratio). DVB as a comonomer enhanced the grafting degree (Gd) and grafting efficiency (Ge) of iPB-g-MAH better than styrene. The initiator DCP had little effect on Gd as its concentration over 0.2 phr, but the grafts’ melt flow rate (MFR) increased significantly, and relative molecular weight decreased remarkably with increased DCP concentration. With increasing Gd, the contact angle of grafts with water decreased, and there was a larger crystallization rate. The study of iPB-1 and iPB-g-MAH (Gd = 1.5%)-modified polyamide 6 (PA6) showed that iPB-g-MAH had an obviously toughening effect on PA6. With increasing iPB-g-MAH concentration, the blends of impact strength and elongation at break increased obviously, tensile strength decreased slightly, and MFR decreased prominently, which greatly slowed the processing degradation of PA6. The properties of iPB-1/PA6 blends deteriorated. Both DSC curves and SEM micrographs confirmed that PA6/iPB-g-MAH blends had much better compatibility than PA6/iPB. The reason was that the anhydride group in iPB-g-MAH reacted with amide group in PA6 to improve the compatibility between two phases, and iPB-g-MAH is an excellent modifier for PA6.

scholarly journals Ultra-high molecular weight elastomeric polyethylene using an electronically and sterically enhanced nickel catalyst

2017 ◽  
Vol 8 (41) ◽  
pp. 6416-6430 ◽  
Author(s):  
Qaiser Mahmood ◽  
Yanning Zeng ◽  
Erlin Yue ◽  
Gregory A. Solan ◽  
Tongling Liang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
High Molecular Weight ◽  
Nickel Catalyst ◽  
High Tensile Strength ◽  
Elongation At Break ◽  
Highly Active ◽  
High Elongation ◽  
Ultra High Molecular Weight ◽  
Shape Fixity

Highly active para-t-Bu-containing 1,2-bis(imino)acenaphthene-Ni(ii) catalysts are disclosed which afford hyper-branched PEs with Mw's up to 3.1 × 106 g mol−1; high tensile strength, excellent shape fixity as well as high elongation at break are a feature.

scholarly journals Insertions and deletions in the RNA sequence–structure map

2021 ◽  
Vol 18 (183) ◽  
Author(s):  
Nora S. Martin ◽  
Sebastian E. Ahnert
Keyword(s):  
Structural Changes ◽  
Structural Effect ◽  
Neutral Evolution ◽  
Sequence Length ◽  
Sequence Structure ◽  
Rna Sequences ◽  
Genetic Changes ◽  
Insertions And Deletions ◽  
Phenotypic Robustness ◽  
Nucleotide Insertions

Genotype–phenotype maps link genetic changes to their fitness effect and are thus an essential component of evolutionary models. The map between RNA sequences and their secondary structures is a key example and has applications in functional RNA evolution. For this map, the structural effect of substitutions is well understood, but models usually assume a constant sequence length and do not consider insertions or deletions. Here, we expand the sequence–structure map to include single nucleotide insertions and deletions by using the RNAshapes concept. To quantify the structural effect of insertions and deletions, we generalize existing definitions for robustness and non-neutral mutation probabilities. We find striking similarities between substitutions, deletions and insertions: robustness to substitutions is correlated with robustness to insertions and, for most structures, to deletions. In addition, frequent structural changes after substitutions also tend to be common for insertions and deletions. This is consistent with the connection between energetically suboptimal folds and possible structural transitions. The similarities observed hold both for genotypic and phenotypic robustness and mutation probabilities, i.e. for individual sequences and for averages over sequences with the same structure. Our results could have implications for the rate of neutral and non-neutral evolution.

scholarly journals Functionalizable coaxial PLLA/PDLA nanofibers with stereocomplexes at the internal interface

2021 ◽  
Author(s):  
Axel T. Neffe ◽  
Quanchao Zhang ◽  
Paul J. Hommes-Schattmann ◽  
Weiwei Wang ◽  
Xun Xu ◽  
...  
Keyword(s):  
Tensile Tests ◽  
Cell Adherence ◽  
Average Molar Mass ◽  
Internal Interface ◽  
Elongation At Break ◽  
Physiological Conditions ◽  
Young’S Moduli ◽  
Relaxation Effects ◽  
Lower Elongation ◽  
Coaxial Fibers

AbstractMultifunctionality of electrospun polylactic acid (PLA) nonwovens was generated by the morphological design of nanofibers. Coaxial fibers with a lower number average molar mass Mn PLLA core and a higher Mn PDLA shell form PDLA–PLLA stereocrystals at the interface, induced by annealing. In tensile tests under physiological conditions, the core–shell fibers with higher crystallinity (22% compared to 11–14%) had lower Young’s moduli E (9 ± 1 MPa) and lower elongation at break εb (26 ± 3%) than PDLA alone (E = 31 ± 9 MPa, εb = 80 ± 5%), which can be attributed to simultaneous crystallization and relaxation effects. Gelatin incorporated in the PDLA phase was presented on the outer surface providing a biointerface putatively favorable for cell adherence. Gelatin incorporation did not influence the crystallization behavior but slightly lowered Tg (60 → 54 °C). Employing exclusively polymers established in the clinic, multifunctionality was generated by design. Graphic abstract

scholarly journals Corn starch reactive blending with latex from natural rubber using Na+ ions augmented carboxymethyl cellulose as a crosslinking agent

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Noppol Leksawasdi ◽  
Thanongsak Chaiyaso ◽  
Pornchai Rachtanapun ◽  
Sarinthip Thanakkasaranee ◽  
Pensak Jantrawut ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Carboxymethyl Cellulose ◽  
Corn Starch ◽  
Crosslinking Agent ◽  
Medical Applications ◽  
Reactive Blending ◽  
Swelling Properties ◽  
Elongation At Break ◽  
Na Ions

AbstractA mixture of corn starch and glycerol plasticizer (CSG) was blended with latex natural rubber (LNR) and carboxymethyl cellulose (CMC). The addition of 10 phr of CMC improved the Young’s modulus (6.7 MPa), tensile strength (8 MPa), and elongation at break (80%) of the CSG/LNR blend. The morphology of the CSG/LNR/CMC blends showed a uniform distribution of LNR particles (1–3 µm) in the CSG matrix. The addition of CMC enhanced the swelling ability and water droplet contact angle of the blends owing to the swelling properties, interfacial crosslinking, and amphiphilic structure of CMC. Fourier transform infrared spectroscopy confirmed the reaction between the C=C bond of LNR and the carboxyl groups (–COO−) of CMC, in which the Na+ ions in CMC acted as a catalyst. Notably, the mechanical properties of the CSG/LNR/CMC blend were improved owing to the miscibility of CSG/CMC and the CMC/LNR interfacial reaction. The CSG/LNR/CMC biodegradable polymer with high mechanical properties and interfacial tension can be used for packaging, agriculture, and medical applications.

Boosting the elongation potential of paper by mechanical refining and additives

TAPPI Journal ◽  
2018 ◽  
Vol 17 (09) ◽  
pp. 489-498 ◽  
Author(s):  
Anders Strand ◽  
Jarmo Kouko ◽  
Antti Oksanen ◽  
Kristian Salminen ◽  
Annika Ketola ◽  
...  
Keyword(s):  
Guar Gum ◽  
Two Dimensional ◽  
Paper Properties ◽  
Elongation At Break ◽  
Tensile Stiffness ◽  
Tensile Index ◽  
Mechanical Refining ◽  
High Elongation ◽  
Pulp Treatment ◽  
The Web

The procedures used in restraining the web during drying will severely affect paper properties. In this work, the main differences between restrained drying and unrestrained drying on paper properties were identified. The mechanical properties of paper were studied as a function of low-consistency mechanical refining energy; wet-end additions of carboxymethyl cellulose (CMC) with cationic starches; as well as spray addition of alginate, chitosan, and cationic guar gum. After restrained drying, the tensile index and tensile stiffness increased with increasing refining energy, but the elongation at break was severely limited. After unrestrained drying, the elongation at break increased linearly with increasing refining energy. However, unrestrained drying also resulted in significantly lower tensile index and tensile stiffness values. After restrained drying, the largest increases in tensile index and stiffness were obtained by sequential wet-end addition of CMC and cationic starches. Certain combinations could mitigate all of the decrease in tensile index from unrestrained drying, while maintaining the distinctively high elongation potential of the paper. Wet-end addition of CMC and cationic starches could mitigate some of the decrease in tensile stiffness, but not completely. Spray addition of alginate, chitosan, or cationic guar gum increased the tensile index after both restrained and unrestrained drying. Spray addition of alginate resulted in significant increases in elongation at break and two-dimensional formability of the handsheets after unrestrained drying. After restrained drying, the tensile stiffness increased after spray addition of all of the different polysaccharides. After unrestrained drying, however, stiffness was unaffected by all of the tested polysaccharide spray additions. The same pulp treatment/additives will increase either stiffness or stretch, depending on the drying technique, but both properties could not be maximized simultaneously.

Low Stress, High Resolution Photosensitive Polyimide Based on a BPDA/PDA/6FDAm Copolymer

1993 ◽  
Vol 323 ◽  
Author(s):  
Marie Angelopoulos ◽  
Jeff Gelorme ◽  
Sally Swanson ◽  
Jeff Labadie
Keyword(s):  
High Resolution ◽  
Physical Properties ◽  
Thick Film ◽  
High Performance ◽  
Elongation At Break ◽  
Optically Transparent ◽  
High Elongation

AbstractA novel series of BPDA/PDA/6FDAm polyimide copolymers have been developed. These materials are more flexible, soluble, and more optically transparent than the homopolymer BPDA/PDA. A negative acting PSPI has been developed based on one of these copolymers. This PSPI exhibits high resolution. 6 μm lines can be delineated in a 19 μm thick film. In addition, the PSPI exhibits high performance mechanical/physical properties such as a low CTE, low stress, and high elongation at break.

Ultrafine Wollastonite Reinforced Polypropylene/Ethylene Propylene Diene Rubber Thermoplastic Elastomers

2012 ◽  
Vol 488-489 ◽  
pp. 945-949 ◽  
Author(s):  
Saowaroj Chuayjuljit ◽  
Thatisorn Karnjanamayul
Keyword(s):  
Thermal Stability ◽  
Tensile Strength ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Thermoplastic Elastomers ◽  
Dependent Manner ◽  
Elongation At Break ◽  
Ethylene Propylene ◽  
Ethylene Propylene Diene Rubber ◽  
Diene Rubber

In this study, tensile properties, thermal stability and morphology of polypropylene/ethylene propylene diene rubber/wollastonite (PP/EPDM/wollastonite) thermoplastic elastomer composites were tested and evaluated as a function of their compositions in comparison with PP/EPDM blends and native PP. PP was melt mixed with two loadings of EPDM (20 and 30% (w/w)) and for the composites each of these with three loadings of wollastonite (10, 20 and 30 parts by weight per hundred of the PP/EPDM resin) on a twin screw extruder and then injection molded. Both PP/EPDM blends provided a higher elongation at break but a lower tensile strength and Young’s modulus as compared with those of the neat PP. However, the addition of wollastonite microparticles (particle size of 1200 mesh) into the blends increased the Young’s modulus in a dose-dependent manner with increasing wollastonite loadings, whilst the tensile strength and elongation at break were decreased. Moreover, the thermal stability was improved by the presence of either EPDM or wollastonite in the PP matrix.

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