scholarly journals Polylactide (PLA) and Its Blends with Poly(butylene succinate) (PBS): A Brief Review

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1193 ◽  
Author(s):  
Shen Su ◽  
Rodion Kopitzky ◽  
Sengül Tolga ◽  
Stephan Kabasci
Keyword(s):  
Material Properties ◽  
Chemical Structure ◽  
Building Blocks ◽  
Processing Parameters ◽  
International Standards ◽  
Butylene Succinate ◽  
Reactive Compatibilization ◽  
Application Potential ◽  
Specific Material

Polylactide (PLA), poly(butylene succinate) (PBS) and blends thereof have been researched in the last two decades due to their commercial availability and the upcoming requirements for using bio-based chemical building blocks. Blends consisting of PLA and PBS offer specific material properties. However, their thermodynamically favored biphasic composition often restricts their applications. Many approaches have been taken to achieve better compatibility for tailored and improved material properties. This review focuses on the modification of PLA/PBS blends in the timeframe from 2007 to early 2019. Firstly, neat polymers of PLA and PBS are introduced in respect of their origin, their chemical structure, thermal and mechanical properties. Secondly, recent studies for improving blend properties are reviewed mainly under the focus of the toughness modification using methods including simple blending, plasticization, reactive compatibilization, and copolymerization. Thirdly, we follow up by reviewing the effect of PBS addition, stereocomplexation, nucleation, and processing parameters on the crystallization of PLA. Next, the biodegradation and disintegration of PLA/PBS blends are summarized regarding the European and International Standards, influencing factors, and degradation mechanisms. Furthermore, the recycling and application potential of the blends are outlined.

scholarly journals Wine By-Products as Raw Materials for the Production of Biopolymers and of Natural Reinforcing Fillers: A Critical Review

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 381
Author(s):  
Alessandro Nanni ◽  
Mariafederica Parisi ◽  
Martino Colonna
Keyword(s):  
Critical Review ◽  
Raw Materials ◽  
Green Revolution ◽  
Building Blocks ◽  
Poly Lactic Acid ◽  
Butylene Succinate ◽  
Reinforcing Fillers ◽  
Plastic Industry ◽  
Review Reports ◽  
By Products

The plastic industry is today facing a green revolution; however, biopolymers, produced in low amounts, expensive, and food competitive do not represent an efficient solution. The use of wine waste as second-generation feedstock for the synthesis of polymer building blocks or as reinforcing fillers could represent a solution to reduce biopolymer costs and to boost the biopolymer presence in the market. The present critical review reports the state of the art of the scientific studies concerning the use of wine by-products as substrate for the synthesis of polymer building blocks and as reinforcing fillers for polymers. The review has been mainly focused on the most used bio-based and biodegradable polymers present in the market (i.e., poly(lactic acid), poly(butylene succinate), and poly(hydroxyalkanoates)). The results present in the literature have been reviewed and elaborated in order to suggest new possibilities of development based on the chemical and physical characteristics of wine by-products.

scholarly journals Electrochemically Produced Copolymers of Pyrrole and Its Derivatives: A Plentitude of Material Properties Using “Simple” Heterocyclic Co-Monomers

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 281
Author(s):  
Tomasz Jarosz ◽  
Przemyslaw Ledwon
Keyword(s):  
Biological Activity ◽  
Material Properties ◽  
Building Block ◽  
Conjugated Polymer ◽  
Chemical Structure ◽  
Heterocyclic System ◽  
Repeat Unit ◽  
Polymeric Materials ◽  
Pyrrole Derivatives ◽  
Pyrrole Monomer

Polypyrrole is a classical, well-known conjugated polymer that is produced from a simple heterocyclic system. Numerous pyrrole derivatives exhibit biological activity, and the repeat unit is a common building block present in the chemical structure of many polymeric materials, finding wide application, primarily in optoelectronics and sensing. In this work, we focus on the variety of copolymers and their material properties that can be produced electrochemically, even though all these systems are obtained from mixtures of the “simple” pyrrole monomer and its derivatives with different conjugated and non-conjugated species.

scholarly journals Implementation of an Antimicrobial Stewardship Program in Five Colombian Hospitals in 2018

2020 ◽  
Vol 41 (S1) ◽  
pp. s273-s273
Author(s):  
Christian Pallares ◽  
María Virginia Villegas Botero
Keyword(s):  
Infection Control ◽  
Antimicrobial Stewardship ◽  
Control Strategies ◽  
Education And Training ◽  
Public Hospitals ◽  
International Standards ◽  
International Consensus ◽  
Stewardship Program ◽  
And Training

Background: More than 50% of antibiotics used in hospitals are unnecessary or inappropriate. The antimicrobial stewardship programs (ASPs) are coordinated efforts to promote the rational and effective use of antibiotics including appropriate selection, dosage, administration, and duration of therapy. When an ASP integrates infection control strategies, it is possible to decrease the transmission of multidrug-resistant pathogens. Methods: In 2018, 5 Colombian hospitals were selected to implement an ASP. Private and public hospitals from different cities were included in the study, ranging from 200 to 700 beds. Our team, consisting of an infectious disease and hospital epidemiologist, visited each hospital to establish the baseline of their ASP program, to define the ASP outcomes according to each hospital’s needs, and to set goals for ASP outcomes in the following 6–12 months. Follow-up was scheduled every 2 months through Skype video conference. The baseline diagnosis or preintervention evaluation was done using a tool adapted from previous reports (ie, international consensus and The Joint Commission international standards). Documentation related to ASPs, such as microbiological profiles, antimicrobial guidelines (AMG) and indicators for the adherence to them as well as antimicrobial resistance (AMR) prevention through protocols, were written and/or updated. Prevention and infection control requirements and protocols were also updated, and cleaning and antiseptic policies were created. Training in rational use of antibiotic, infection control and prevention, and cleaning and disinfection were carried out with the healthcare workers in each institution. Results: Before the intervention, the development of the ASP according to the tool was 27% (range, 5%–47%). The lowest institutional scores were the item related to ASP feedback and reports (11% on average), followed by education and training (14%), defined ASP responsibilities (23%), ASP function according to priorities (26%), and AMR surveillance (27%). After the intervention, the ASP development increased to 57% (range, 39%–81%) in the hospitals. The highest scores achieved were for education and training (90%), surveillance (75%), and the activities of the infection control committee (70%). The items that made the greatest contribution to ASP development were the individual antibiogram, including the bacteria resistance profile, and the development of the AMG based on the local epidemiology in each hospital. Conclusions: The implementation of an ASP should include training and education as well as defining outcomes according to the hospital’s needs. Once the strategy is implemented, follow-up is key to achieving the goals.Funding: NoneDisclosures: None

Abstract 562: Human Carotid Atherosclerosis Plaque Progression and Vessel Material Stiffness at Follow Up Had Positive Correlation: An in vivo Vessel Stiffness MRI Follow Up Study

2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Qingyu Wang ◽  
Dalin Tang ◽  
Gador Canton ◽  
Jian Guo ◽  
Xiaoya Guo ◽  
...  
Keyword(s):  
Negative Correlation ◽  
Material Properties ◽  
Stretch Ratio ◽  
Patient Specific ◽  
Plaque Progression ◽  
Material Stiffness ◽  
Variation Rate ◽  
Vessel Material

It is hypothesized that artery stiffness may be associated with plaque progression. However, in vivo vessel material stiffness follow-up data is lacking in the literature. In vivo 3D multi-contrast and Cine magnetic resonance imaging (MRI) carotid plaque data were acquired from 8 patients with follow-up (18 months) with written informed consent obtained. Cine MRI and 3D thin-layer models were used to determine parameter values of the Mooney-Rivlin models for the 81slices from 16 plaques (2 scans/patient) using our established iterative procedures. Effective Young’s Modulus (YM) values for stretch ratio [1.0,1.3] were calculated for each slice for analysis. Stress-stretch ratio curves from Mooney-Rivlin models for the 16 plaques and 81 slices are given in Fig. 1. Average YM value of the 81 slices was 411kPa. Slice YM values varied from 70 kPa (softest) to 1284 kPa (stiffest), a 1734% difference. Average slice YM values by vessel varied from 109 kPa (softest) to 922 kPa (stiffest), a 746% difference. Location-wise, the maximum slice YM variation rate within a vessel was 306% (139 kPa vs. 564 kPa). Average slice YM variation rate within a vessel for the 16 vessels was 134%. Average variation of YM values from baseline (T1) to follow up (T2) for all patients was 61.0%. The range of the variation of YM values was [-28.4%, 215%]. For progression study, YM increase (YMI=YM T2 -TM T1 ) showed negative correlation with plaque progression measured by wall thickness increase (WTI), (r= -0.6802, p=0.0634). YM T2 showed strong negative correlation with WTI (r= -0.7764, p=0.0235). Correlation between YM T1 and WTI was not significant (r= -0.4353, p= 0.2811). Conclusion In vivo carotid vessel material properties have large variations from patient to patient, along the vessel segment within a patient, and from baseline to follow up. Use of patient-specific, location specific and time-specific material properties could potentially improve the accuracy of model stress/strain calculations.

Effects of infill patterns on the strength and stiffness of 3D printed topologically optimized geometries

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Nadim S. Hmeidat ◽  
Bailey Brown ◽  
Xiu Jia ◽  
Natasha Vermaak ◽  
Brett Compton
Keyword(s):  
Material Properties ◽  
Failure Modes ◽  
Mechanical Anisotropy ◽  
Failure Behavior ◽  
Fused Filament Fabrication ◽  
Content Type ◽  
Orthotropic Composite ◽  
Material Extrusion ◽  
Specific Material ◽  
Strength And Stiffness

Purpose Mechanical anisotropy associated with material extrusion additive manufacturing (AM) complicates the design of complex structures. This study aims to focus on investigating the effects of design choices offered by material extrusion AM – namely, the choice of infill pattern – on the structural performance and optimality of a given optimized topology. Elucidation of these effects provides evidence that using design tools that incorporate anisotropic behavior is necessary for designing truly optimal structures for manufacturing via AM. Design/methodology/approach A benchmark topology optimization (TO) problem was solved for compliance minimization of a thick beam in three-point bending and the resulting geometry was printed using fused filament fabrication. The optimized geometry was printed using a variety of infill patterns and the strength, stiffness and failure behavior were analyzed and compared. The bending tests were accompanied by corresponding elastic finite element analyzes (FEA) in ABAQUS. The FEA used the material properties obtained during tensile and shear testing to define orthotropic composite plies and simulate individual printed layers in the physical specimens. Findings Experiments showed that stiffness varied by as much as 22% and failure load varied by as much as 426% between structures printed with different infill patterns. The observed failure modes were also highly dependent on infill patterns with failure propagating along with printed interfaces for all infill patterns that were consistent between layers. Elastic FEA using orthotropic composite plies was found to accurately predict the stiffness of printed structures, but a simple maximum stress failure criterion was not sufficient to predict strength. Despite this, FE stress contours proved beneficial in identifying the locations of failure in printed structures. Originality/value This study quantifies the effects of infill patterns in printed structures using a classic TO geometry. The results presented to establish a benchmark that can be used to guide the development of emerging manufacturing-oriented TO protocols that incorporate directionally-dependent, process-specific material properties.

PREDICTION OF PEEK RESIN PROPERTIES FOR PROCESSING MODELING USING MOLECULAR DYNAMICS

2021 ◽  
Author(s):  
KHATEREH KASHMARI ◽  
PRATHAMESH DESHPANDE ◽  
SAGAR PATIL ◽  
SAGAR SHAH ◽  
MARIANNA MAIARU ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Residual Stresses ◽  
Crystallization Kinetics ◽  
Material Properties ◽  
Elevated Temperatures ◽  
Processing Parameters ◽  
Thermomechanical Properties ◽  
Volumetric Shrinkage ◽  
Processing Temperature ◽  
Wide Range

Polymer Matrix Composites (PMCs) have been the subject of many recent studies due to their outstanding characteristics. For the processing of PMCs, a wide range of elevated temperatures is typically applied to the material, leading to the development of internal residual stresses during the final cool-down step. These residual stresses may lead to net shape deformations or internal damage. Also, volumetric shrinkage, and thus additional residual stresses, could be created during crystallization of the semi-crystalline thermoplastic matrix. Furthermore, the thermomechanical properties of semi-crystalline polymers are susceptible to the crystallinity content, which is tightly controlled by the processing parameters (processing temperature, temperature holding time) and material properties (melting and crystallization temperatures). Hence, it is vital to have a precise understanding of crystallization kinetics and its impact on the final component's performance to accurately predict induced residual stresses during the processing of these materials. To enable multi-scale process modeling of thermoplastic composites, molecular-level material properties must be determined for a wide range of crystallinity levels. In this study, the thermomechanical properties and volumetric shrinkage of the thermoplastic Poly Ether Ether Ketone (PEEK) resin are predicted as a function of crystallinity content and temperature using molecular dynamics (MD) modeling. Using crystallization-kinetics models, the thermo-mechanical properties are directly related to processing time and temperature. This research can ultimately predict the residual stress evolution in PEEK composites as a function of processing parameters.

scholarly journals 3D Printed Chromophoric Sensors

Chemosensors ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 317
Author(s):  
Zachary Brounstein ◽  
Jarrod Ronquillo ◽  
Andrea Labouriau
Keyword(s):  
Thermal Stability ◽  
3D Printing ◽  
Material Properties ◽  
Chemical Structure ◽  
Elevated Temperatures ◽  
Advanced Manufacturing ◽  
Color Changes ◽  
Printed Sensors ◽  
3D Printed ◽  
Manufacturing Techniques

Eight chromophoric indicators are incorporated into Sylgard 184 to develop sensors that are fabricated either by traditional methods such as casting or by more advanced manufacturing techniques such as 3D printing. The sensors exhibit specific color changes when exposed to acidic species, basic species, or elevated temperatures. Additionally, material properties are investigated to assess the chemical structure, Shore A Hardness, and thermal stability. Comparisons between the casted and 3D printed sensors show that the sensing devices fabricated with the advanced manufacturing technique are more efficient because the color changes are more easily detected.

scholarly journals Olfactory ensheathing cell transplantation for chronic spinal cord injury: A long-term follow-up study

2021 ◽  
Vol 9 (2) ◽  
pp. 94-105
Author(s):  
Naifeng Kuang ◽  
Xiaoyu Wang ◽  
Yuexia Chen ◽  
Guifeng Liu ◽  
Fan’e Kong ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Autonomic Function ◽  
Spinal Injury ◽  
International Standards ◽  
Olfactory Ensheathing Cell ◽  
Cord Injury ◽  
Long Term Follow Up

Spinal cord injury is a serious disabling condition. Transplantation of olfactory ensheathing cells (OECs) is one of the most promising treatments for spinal cord injury (SCI). Thirty-nine patients with chronic SCI received OEC transplantation and completed long-term follow-up, with a minimum follow-up of 7 years. We assessed sensorimotor function with the American Spinal Injury Association (ASIA) Impairment Scale (AIS) and autonomic nervous function by the International Standards to document remaining Autonomic Function after Spinal Cord Injury (ISAFSCI), and sympathetic skin responses (SSR). The scores of each group were significantly higher after OECs transplantation than before treatment. SSR latencies were shorter and response amplitudes increased after treatment. Long-term follow-up showed further improvement only in motor function and autonomic function compared with 3 months postoperatively. No complications occurred in any patient during long-term follow-up. The results indicate that the transplantation of OECs in spinal cord restored function without serious side effects.

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