Polylactide Acid Research Articles

Antimicrobial behavior, low-stress mechanical properties, and comfort of knitted fabrics made from poly (hydroxybutyrate-co-hydroxyvalerate)/polylactide acid filaments and cotton yarns

This article presents a systematic investigation of the knitted fabrics made from various blends of intrinsically antimicrobial poly (hydroxybutyrate-co-hydroxyvalerate)/polylactide acid filaments and cotton staple fibers. The effects of blend yarn, fabric structures, and distributions of fibers on antimicrobial properties of resultant yarns and knitted fabrics were studied. The relationships among fiber distribution, blend ratio, and anti-microbial properties were experimentally determined for three blend yarns made by sirofil, wrap-spun, and core-spun spinning technologies. The fabrics made from the sirofil-spun and wrap-spun yarns show better anti-microbial effects against Staphylococcus aureus, Klebsiella pneumoniae, and Candida albicans than those of the core-spun yarns, according to the standard AATCC100-2012 Antibacterial Finishes on Textile Materials (American Association of Textile Chemists and Colorists, 2012). An alternative blending method of co-knitting of the pure poly (hydroxybutyrate-co-hydroxyvalerate)/polylactide acid yarns and cotton yarns achieved excellent antimicrobial effects. Furthermore, a wearing trial of underwear made from the blended knitted fabrics was conducted in a nursing home. The wearing comfort of the garments, low-stress mechanical and surface properties of fabrics were evaluated objectively by the Kawabata Evaluation System of Fabric (KESF) system and subjectively by a questionnaire survey to users.

Spectra-structure correlations in NIR region of polymers from quantum chemical calculations. The cases of aromatic ring, C=O, C≡N and C-Cl functionalities

Near-infrared (NIR) spectroscopy is a valued analytical tool in various applications involving polymers. However, complex nature of NIR spectra imposes difficulties in their direct interpretation. Here, anharmonic quantum chemical calculations are used to simulate NIR spectra of nine polymers; acrylonitrile butadiene styrene (ABS), ethylene–vinyl acetate (EVAC), polycarbonate (PC), polyethylene terephthalate (PET), polylactide or polylactic acid (PLA), polymethylmethacrylate (PMMA), polyoxymethylene (POM), polystyrene (PS) and polyvinylchloride (PVC). The generalized spectra-structure correlations are derived for these systems with focus given to the manifestation in NIR spectra of aromatic ring, C=O, C≡N and C-Cl functionalities. It is concluded that the nature of NIR polymer bands is only moderately sensitive to the remote chemical neighborhood. The majority of NIR absorption of polymers originates from binary combination bands, while the first overtones are meaningful only in ca. 6200–5500 cm−1 region. The contribution of the overtone bands is relatively higher for the polymers bearing aromatic rings because of higher intensity of C-H stretching overtones. Highly characteristic combination bands of the modes localized in aromatic ring (ring deformation and CH stretching) are relatively independent on the remaining structure of the polymer. The combination bands originating from C=O group are more sensitive to the chemical neighborhood in near proximity, forming a useful fingerprint for a specific polymer. In contrast, the vibrational bands of C≡N functionality are far less useful in NIR region than in infrared (IR) region. With aid of the calculated absorption bands, structural specificity of NIR spectroscopy of polymers can be markedly improved.

Waste office paper filled polylactic acid composite filaments for 3D printing

Developing 3D printable waste paper based biocomposites is a potentially greener alternative to traditional waste paper recycling methods. In this paper, waste office paper (WOP) filled polylactide acid (PLA) biocomposites were prepared as filaments for Fused Filament Fabrication (FFF). The morphology, rheology, thermal properties, and physical properties of PLA-WOP composites were investigated. Results revealed that the addition of WOP improved the composites’ melt flow abilities. The Tg and Tm of composites remained similar to the neat PLA. However, tensile strengths of the prints decreased with the increase of WOP content, which could be attributed to the heterogeneous dispersion and aggregation caused by the abundance of WOP in the system. When 5% WOP was used, the elongation at break increased in comparison with pure PLA specimens. Nonetheless, when the WOP content was increased to 15%, the elongation at break decreased. To improve the mechanical properties of the prints, a silane coupling agent (γ-methacryloxypropyltrimethoxylsilane, KH570) was used to modify WOP granules. The mechanical properties were clearly enhanced post KH570 treatment. Furthermore, FTIR analyses demonstrated that the hydrogen bonding improved interfacial adhesion between WOP fillers and the PLA matrix. Thermal decomposition showed that the PLA-WOP composites had virtually no degradation below 260 °C, indicating that the composite filaments are safe for indoor 3D printing.

3D-printing on textiles \u2013 an investigation on adhesion properties of the produced composite materials

The actual paper is related to adhesive properties of 3D objects printed on cotton textile fabrics. For practical applications of 3D prints in the textile sector, the adhesion of the printed object on the textile substrate is an important issue. In the current study, two different types of polymers are printed on cotton – polylactide acid (PLA) and polyamide 6.6 (Nylon). Altogether six cotton fabrics differing in structure, weight and thickness are evaluated. Also, the effect of washing and enzymatic desizing is investigated. For printing parameters, best results are gained for elevated process temperatures, intermediate printing speed and low Z-distance between printing head and substrate. Also, a textile treatment by washing and desizing can improve the adhesion of an afterwards applied 3D print. The presented results are quite useful for future developments of 3D printing applications on textile substrates, e.g. to implement new decorative features or protective functions.

Cruciate Ligament Cell Sheets Can Be Rapidly Produced on Thermoresponsive poly(glycidyl ether) Coating and Successfully Used for Colonization of Embroidered Scaffolds.

Anterior cruciate ligament (ACL) cell sheets combined with biomechanically competent scaffolds might facilitate ACL tissue engineering. Since thermoresponsive polymers allow a rapid enzyme-free detachment of cell sheets, we evaluated the applicability of a thermoresponsive poly(glycidyl ether) (PGE) coating for cruciate ligamentocyte sheet formation and its influence on ligamentocyte phenotype during sheet-mediated colonization of embroidered scaffolds. Ligamentocytes were seeded on surfaces either coated with PGE or without coating. Detached ligamentocyte sheets were cultured separately or wrapped around an embroidered scaffold made of polylactide acid (PLA) and poly(lactic-co-ε-caprolactone) (P(LA-CL)) threads functionalized by gas-phase fluorination and with collagen foam. Ligamentocyte viability, protein and gene expression were determined in sheets detached from surfaces with or without PGE coating, scaffolds seeded with sheets from PGE-coated plates and the respective monolayers. Stable and vital ligamentocyte sheets could be produced within 24 h with both surfaces, but more rapidly with PGE coating. PGE did not affect ligamentocyte phenotype. Scaffolds could be colonized with sheets associated with high cell survival, stable gene expression of ligament-related type I collagen, decorin, tenascin C and Mohawk after 14 d and extracellular matrix (ECM) deposition. PGE coating facilitates ligamentocyte sheet formation, and sheets colonizing the scaffolds displayed a ligament-related phenotype.

�Green Carbon� from Algae for Automotive Applications

Due to the continuous decrease in the level of oil resource, nowadays researchers from all fields are concerned with the creation of new bio plastics with special properties. The present work presents a series of such properties, which become achievable when reinforcing organic fibre materials obtained by reactive extrusion of thermoplastic Polyurethan (TPU) with Polylactid-Acid (PLA) in a twin-screw extruder and covalently linked into PLA-TPU-Blends, through the innovative one-step process technology, using the IMC Krauss Maffei injection moulding compounder, at the IKT University of Stuttgart. The elongation at break of PLA-TPU-Blends and the impact strength could be increased without significant reduction of strength and stiffness. A balanced relation between improved impact strength and reduced stiffness can be achieved by varying of the blend components. By using the partially biobased Polyurethane and natural fibres, a biobased content of more than 90% could be achieved. More and more advanced technologies allow the manufacture of components with reinforcements made of glass fibres, natural or carbon fibres obtained from polypropylene or Lignin. Due to their low specific weight compared to glass, carbon fibres are preferred for lightweight structures in the automotive or aeronautics industries. Green Carbon fibres, made in innovative ways from acrylonitrile resulting in the production of Bio-Diesel from algae, can successfully replace the conventional carbon fibres of Polypropylene, having identical properties. Fibre reinforcement aims to improve mechanical strength and impact resistance and increases the dimensional stability under heat of the composite. This feasibility study shows a method to realize fibre-reinforced materials using Green Carbon fibres with remarkable stability and rigidity similar or better than aluminum and steel for lightweight constructions.

Electrospinning of small diameter vascular grafts with preferential fiber directions and comparison of their mechanical behavior with native rat aortas

Conventional electrospun small diameter vascular grafts have a random fiber orientation. In order to achieve mechanical characteristics similar to a native blood vessel, a controllable fiber orientation is of interest. In this study the electrospinning jet was directly controlled by means of an auxiliary, changeable electrostatic field, so that the fibers could be deposited in adjustable orientations. Prostheses with circumferentially, axially, fenestrated and randomly aligned fibers were electrospun on Ø2mm mandrels out of a thermoplastic polyurethane (PUR) and a polylactid acid (PLLA). The impact of the materials and the various preferential fiber orientations on the resulting biomechanics was investigated and compared with that of the native rat aorta in quasistatic and dynamic hoop tensile tests. The test protocol included 3000 dynamic loading cycles in the physiological blood pressure range and ended with a quasistatic tensile test. Any orientation of the fibers in a particular direction resulted in a significant reduction in scaffold porosity for both materials. The standard randomly oriented PUR grafts showed the highest compliance of 29.7 ± 5.5 [%/100 mmHg] and were thus closest to the compliance of the rat aortas, which was 37.2 ± 6.5 [%/100 mmHg]. The maximum tensile force was increased at least 6 times compared to randomly spun grafts by orienting the fibers in the circumferential direction. During the 3000 loading cycles, creeping of the native rat aorta was below 1% whereas the electrospun grafts showed creeping up to 2.4 ± 1.2%. Although the preferred fiber orientations were only partially visible in the scanning electron micrographs, the mechanical effects were evident. The investigations suggest a multi-layer wall structure of the vascular prosthesis, since none of the preferred fiber directions and the materials used could imitate the typical j-shaped mechanical characteristics of the rat aorta.

Antifouling performance of copper-containing fused filament fabrication (FFF) 3-D printing polymer filaments for marine applications

3-D printing allows for rapid prototyping and manufacture of components in a cost effective and timely manner, becoming a popular technology for oceanographic and maritime engineering applications. However, 3-D printed components are at risk of accumulating marine biofouling. This study examined the antifouling (AF) performance of three Cu-containing 3-D printing polymer filaments for potential marine use. The amount of Cu present in each filament was the primary determinant of AF performance. The lowest Cu-content (30%) filament recording 29% biofouling cover after 1 month and near 100% cover after 3 months. These AF results were comparable to polylactide acid (PLA) and acrylonitrile butadiene styrene (ABS) polymer filament controls. The medium (50%) Cu-content filament remained largely free of biofouling until 3 months (where 48% coverage was observed), after which fouling cover increased to 100% by ∼12 months. The highest Cu-content (80%) filament remained free of all macrofouling for the entire 24 months of the experiment.

Highly luminescent and electrically conductive hybrid material

We proposed a highly luminescent and electrically conducting polymer composite material based on polylactide acid (PLA) polymer filled with reduced graphene oxide (RGO) or graphene oxide (GO) nanoplatelets covered by organic Eu(III) complexes tris-dibenzoylmethane mono-1,10-phenanthroline europium(III) [Eu(DBM)3Phen]. No Eu(DBM)3Phen luminescence quenching by RGO and GO nanoplatelets has been observed in emission decay. Partial luminescence intensity decrease is caused by graphene nanoplatelets absorption. Conductivity of the composite film is increased by more than five orders of magnitude as compared to the pure polymer. The proposed material is suitable for 3D printing technology and wide applications in optoelectronics.

Security of 3D-printed polylactide acid piece sterilization in the operating room: a sterility test.

3D-printing technology has become very popular the last 10years, and their advantages have been widely proved. However, its safety in the operating room after sterilization has not been evaluated. Thus, the use of 3D printing is still questioned. The aim of this work is to evaluate the security of polylactic acid (PLA) to print surgical models after its sterilization. One hundred and eighty-six PLA plates and 6 negative controls without microorganisms were seeded. After 10days of culture, the PLA plates were randomized into three groups: A, B, and C. Group A underwent a sterilization process using an autoclave program at 134°C. Group B was seeded in different culture media and group C was used to make crystal violet stains on the biofilms formed on the PLA. Mechanical properties of PLA after autoclave sterilization including, the breaking load, deformation and breaking load per surface were calculated. Hundred percent of the group B showed monomicrobial growth. Stains performed on group C PLA showed biofilms in all PLA pieces. After sterilization, no pathogen growth was observed in group A during the culture observation period showing 100% sterilization effectiveness. A filling percentage of 5% obtained a breaking load of 6.36MPa, and its elastic limit occurred after an elongation of 167.4%. A 10% infill was mechanically safe. Autoclave sterilization of PLA-printed pieces is safe for the patient and mechanically strong for the surgeon. This is the first 3D-printing protocol described and evaluated to implement 3D-printing technology safely in the operating room. This is the first 3D-printing protocol described to print and sterilize 3D biomodels using an autoclave showing its biological safety and its mechanical resistance.

Relative Influence of Plastic Debris Size and Shape, Chemical Composition and Phytoplankton-Bacteria Interactions in Driving Seawater Plastisphere Abundance, Diversity and Activity.

The thin film of life that inhabits all plastics in the oceans, so-called “plastisphere,” has multiple effects on the fate and impacts of plastic in the marine environment. Here, we aimed to evaluate the relative influence of the plastic size, shape, chemical composition, and environmental changes such as a phytoplankton bloom in shaping the plastisphere abundance, diversity and activity. Polyethylene (PE) and polylactide acid (PLA) together with glass controls in the forms of meso-debris (18 mm diameter) and large-microplastics (LMP; 3 mm diameter), as well as small-microplastics (SMP) of 100 μm diameter with spherical or irregular shapes were immerged in seawater during 2 months. Results of bacterial abundance (confocal microscopy) and diversity (16S rRNA Illumina sequencing) indicated that the three classical biofilm colonization phases (primo-colonization after 3 days; growing phase after 10 days; maturation phase after 30 days) were not influenced by the size and the shape of the materials, even when a diatom bloom (Pseudo-nitzschia sp.) occurred after the first month of incubation. However, plastic size and shape had an effect on bacterial activity (3H leucine incorporation). Bacterial communities associated with the material of 100 μm size fraction showed the highest activity compared to all other material sizes. A mature biofilm developed within 30 days on all material types, with higher bacterial abundance on the plastics compared to glass, and distinct bacterial assemblages were detected on each material type. The diatom bloom event had a great impact on the plastisphere of all materials, resulting in a drastic change in diversity and activity. Our results showed that the plastic size and shape had relatively low influence on the plastisphere abundance, diversity, and activity, as compared to the plastic composition or the presence of a phytoplankton bloom.

Influence of coatings on degradation and osseointegration of open porous Mg scaffolds in vivo

Degradable bone substitutes like Mg-based alloys are promising due to their good osseointegration and biocompatibility. The objective of this study was to investigate the influence of additional coatings on the degradation behavior, osseointegration and gas release of 128 open porous scaffolds (Ø 4 mm, length 5 mm) of the magnesium alloy LAE442 (4 wt% Li, 4 wt% Al, 2 wt% rare earths). Along a base layer of MgF2 polylactide acid (PLA) or calcium phosphate (CaP) were applied. While the resorbable PLA was supposed to delay the magnesium degradation, the CaP should form a nutrient depot for growing bone. The control group consisted of 32 β-tricalcium phosphate (TCP) scaffolds. The scaffolds were inserted into the greater trochanter of 80 adult female ZiKa rabbits. X-ray and in vivo μCT scans were performed postoperatively at regular intervals of 6, 12, 24, 36 weeks. Gas accumulation, scaffold degradation and osseointegration were evaluated. In comparison, PLA-coated scaffolds degraded slightly slower, but had a significantly greater amount of gas in the medullary canal at weeks 2 and 4 compared to CaP-coated scaffolds. CaP-coated scaffolds showed better values for drill hole closure and a significantly higher number of bone-scaffold contacts from week 12 to 36 compared to PLA. Furthermore, CaP-coated scaffolds showed higher bone volume and more new formed bone trabeculae than PLA-coated scaffolds. In total, an additional coating with CaP seemed to be promising in improving the degradation resistance and osseointegration, when using biodegradable bone substitutes.

Experimental and computational investigation of polylactic acid/silver‐NP nanocomposite with antimicrobial activity prepared by plasma in liquid

AbstractIn this study, an underwater impulse discharge initiated in an aqueous suspension of a polylactide acid between silver rods is applied to produce silver nanoparticles (AgNPs) and create a polymer nanocomposite. The spectral and energy characteristics of the discharge are obtained. The composites are characterized by methods of scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, and thermogravimetric analysis. Investigation of the formation of the composite of polylactic acid (PLA) with AgNP has been performed using the molecular dynamics method. The PLA/AgNPs composite films were effective against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Candida albicans, and thus may find future application in the food packaging area.

Quasi-static compression behaviour of interlocking core structures made of flax fibre reinforced polylactic acid composite

Natural fibres have been gaining a lot of attention for its use in various of fields. It has a potential to replace synthetic fibre due to their availability from renewable natural resources, high specific strength and modulus, low cost, light weight and biodegradability. This paper investigates tensile and quasi static compression properties of flax reinforced polylactide acid (flax/PLA) composites. Initially, the effect of variation of manufacturing temperature on tensile properties of flax PLA composites was examined at three different temperatures of 170, 180 and 190 °C a pressing times of 5, 10 and 15 min were considered. Then a range of double cell walls interlocking square core structures were manufactured using hot press machine and later fabricated through a simple slotting technique. Next, the sandwich structures were tested under quasi-static compression loading with a crosshead displacement rate of 2 mm/min to evaluate their compression properties. The study revealed that that flax/PLA composites manufactured at a temperature of 180℃ and pressed for 5 min. gave the highest value of strength, whereas a temperature of 190℃, pressed for 15 min. is the lowest. Furthermore, results showed that sandwich structures with double cell walls exhibited better strength and energy absorption capacity by approximately 80 and 86% respectively than those offered by ingle cell wall cores as reported in the literatures.

Development of Bionanocomposites Based on Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)/PolylActide Blends Reinforced with Cloisite 30B.

In the present study, poly(3-hydroxybuturate-co-3-hydroxyvalerate) (PHBV) and plasticized polylactide acid (PLA) blends were processed by melt extrusion with different weight ratio (up to 20 wt.% of PHBV). Bionanocomposites were obtained through the incorporation of an organomodified montmorillonite (C30B) at 3 wt.%. The main features of the processing and physico-chemical characterization of films and injected samples were assessed and the influence of the components on the chemical, thermal and mechanical properties of the bionanocomposites was investigated. The results indicated that plasticized PLA/PHBV/C30B bionanocomposites present optimal mechanical properties for sanitary applications. Moreover, plasticized PLA/PHBV could lead to finely tuned biomaterials able to form electrospun nanofibers.

Effect of nanoclay on mechanical and morphological properties of poly(lactide) acid (PLA) and polypropylene (PP) blends

The aim of this study is to blend the poly(lactide) acid (PLA) and polypropylene (PP) with a fixed ratio of PLA to PP, 75 to 25% by weight using the twin screw extruder. A 3 wt% MAgPP was added into the polymer blends as a compatibilizer. Organo-nanoclay of montmorillonite (OMMT), were added in the amounts of 1, 3, 5 and 7 wt% in polymer blends to improve the mechanical, thermal and morphological properties of the nanocomposites. The resulting polymer nanocomposites were evaluated by using universal testing machine, Izod impact test, thermogravimetric analyzer (TGA) and scanning electron microscope (SEM). The nanocomposites with 1 wt% nanoclay showed the highest tensile strength results which is 49.53 MPa. The Izod impact strength was increased up to 39.2% for 3 wt% of nanoclay. The tensile strain increased about 9.4% after addition of 1 wt% of nanoclay as compared with PLA/PP blend without nanoclay. Overall tensile strain results show that there were slightly changes was observed as increasing the nanoclay content from 3 to 5 and 7 wt%. TGA results showed that the degradation temperature was improved by the addition of 5 wt% of nanoclay in PLA/PP blend. The brittle fractured surface was observed under SEM analysis when 5 wt% nanoclay used. In general, mechanical properties reduced as the nanoclay content increased.

Chemical degradation of 3D printed products

This template describes the behavior of products created with additive 3D printing technology. The tested material used to produce the samples was polyactide acid (PLA). PLA is one of the most favourite material for 3D printing. This polylactide acid contains a metal additive. The standard dog-bone shaped samples reinforced with internal ribs arranged in a grid with 20% of the internal volume of the rib-filled sample were tested for tensile strength. The samples were subjected to different types of chemical degradation prior to the test. As a degradation agent, there was used an organic solvents. The result of the research is the effect of the degradation factor on the mechan-ical properties of these samples and possible use in practice, specifically in technology.

The effectiveness of fiber-reinforced natural composites compared to the elastomer materials produced from nonrenewable resources in vibration transmission suppression

In this work, a number of tests were carried out to evaluate the effectiveness of the vibro-acoustic behavior composite consisting of a biodegradable polymer matrix (polylactid acid) and a filler in the form of natural flax fibers, with a moisture content of 2.03% after drying in 80°C for 4 h. To improve material dampening properties, polylactid acid was plasticized with polyethylene glycol 400 and triethyl citrate. The flax fiber content of the composite was 10, 20, and 30 wt%. Mechanical properties at bending and tensile were performed. For the measurement of vibro-acoustic suppression effectiveness, composite samples have been made to enable installation in the measurement system. The measuring system consisted of an unbalanced axial electric motor, resting on a steel frame placed on vibration suppressor. For comparison, the commercial grade vibration suppressor was used. In order to evaluate the vibration damping of the system by vibration suppressor, vibration engine frame vibration was forced by acceleration of the engine’s rotational speed to specific frequencies. It has been proven that the type of the plasticizer used in the composite changes the vibro-acoustic suppression parameter. Also, the length and the weight percentage of the fibers result in lower material damping values.

Modification of Poly Lactid Acid (PLA)/Chitosan with cinnamon essential oil for antibacterial applications

The active packaging material used for the manufacture of food packaging that has antimicrobial properties. The purpose of this research is to inhibit the growth of microorganisms on food surfaces, to improve nutritional quality and to extend the shelf life of food and reduce the environmental impact of packaging. The preparation is done Cinnamon essential oil (CEO) is a natural antimicrobial being investigated for food packaging as a substitute for synthetic chemicals due to consumer concerns over food safety. In this study, lactic acid poly (PLA) and chitosan were successfully modified with essential oil (CEO) at concentrations (1.5%, 2%, 2.5%, and 3% v/v) that formed composite fibres with using a simple electrospinning method. The morphology of the composite fibres can be seen from PLA / CS-CEO-2.5 showing good stability of the CEO so that the antimicrobial activity is increased compared to other blends. PLA / CS-CEO fibre shows a high level of long-term inactivation against Escherichia coli and Staphylococcus aureus due to the CEO’s ongoing release, indicating that advanced PLA / CS-CEO fibres have great potential for active food packaging applications.

Combination of poly lactid acid zinc oxide nanocomposite for antimicrobial packaging application

Many food packages (plastic wrappers) today cannot be broken down by the environment. therefore, it is necessary to add natural substances that can make the food package decompose and be resistant to contamination with bacteria. Poly lactic acid (PLA) is one of the natural polymers produced by several bacteria that grow in crops rich in carbohydrates (such as sugar beets, corn and others). This research aims to insert ZnO nanoparticles and chitosan into a plastic layer of PLA (poly lactic acid) which can improve the antibacterial properties of the resulting packaging. The method used in making PLA-ZnO-chitosan Nano composite is the precipitation method and the heating method. PLA-ZnO Nano composites were obtained by varying ZnO nanoparticles 0.5% by weight, 2% by weight, and 3.5% by weight. The results obtained in SEM images show that nanoparticles are homogeneously distributed on the plastic surface. Antimicrobial tests show nanocomposites work effectively in deactivating E. coli and S. aureus. where it was found that E. coli was more susceptible to this type of nanocomposite, where there was a reduction of 3.4 logs to 3.5% ZnO loading in the PLA layer.