scholarly journals The Role of the Mechanical, Structural, and Thermal Properties of Poly(l-lactide-co-glycolide-co-trimethylene carbonate) in the Development of Rods with Aripiprazole

Polymers ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 3556
Author(s):  
Artur Turek ◽  
Jakub Rech ◽  
Aleksandra Borecka ◽  
Justyna Wilińska ◽  
Magdalena Kobielarz ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Weight Loss ◽  
Thermal Properties ◽  
Pore Formation ◽  
Tensile Tests ◽  
Mechanical Tests ◽  
Lag Phase ◽  
Trimethylene Carbonate ◽  
Hot Melt

In this work, we aimed to determine the role of the mechanical, structural, and thermal properties of poly(l-lactide-co-glycolide-co-trimethylene carbonate) (P(l-LA:GA:TMC)) with shape memory in the formulation of implantable and biodegradable rods with aripiprazole (ARP). Hot melt extrusion (HME) and electron beam (EB) irradiation were applied in the formulation process of blank rods and rods with ARP. Rod degradation was carried out in a PBS solution. HPLC; NMR; DSC; compression and tensile tests; molecular weight (Mn); water uptake (WU); and weight loss (WL) analyses; and SEM were used in this study. HME and EB irradiation did not influence the structure of ARP. The mechanical tests indicated that the rods may be safely implanted using a pre-filled syringe. During degradation, no unfavorable changes in terpolymer content were observed. A decrease in the glass transition temperature and the Mn, and an increase in the WU and the WL were revealed. The loading of ARP and EB irradiation induced earlier pore formation and more intense WU and WL changes. ARP was released in a tri-phasic model with the lag phase; therefore, the proposed formulation may be administered as a delayed-release system. EB irradiation was found to accelerate ARP release.

Effects of Molecular Weight of Chitosan on the Biodegradability and Thermal Properties of Polybutylene Succinate/Chitosan Composites

2018 ◽  
Vol 775 ◽  
pp. 26-31
Author(s):  
Sukantika Manatsittipan ◽  
Kamonthip Kuttiyawong ◽  
Kazuo Ito ◽  
Sunan Tiptipakorn
Keyword(s):  
Molecular Weight ◽  
Weight Loss ◽  
Thermal Properties ◽  
Water Absorption ◽  
Melting Temperature ◽  
Microbial Degradation ◽  
Decomposition Temperature ◽  
Molecular Weights ◽  
Significant Difference ◽  
Polybutylene Succinate

In this study, the biodegradability and thermal properties the composites of polybutylene succinate (PBS) and chitosan of different molecular weights (Mn = 104,105, and 106 Da) were prepared at chitosan contents of 0-10 wt%. After 10 days of microbial degradation, the results show that the amount of holes from degradation was increased with either decreasing Mn or increasing chitosan contents. However, the size of holes was increased with increasing Mn and chitosan contents. The results from Differential Scanning Calorimeter (DSC) present that the melting temperature (Tm) of PBS was decreased with increasing chitosan contents. Moreover, there was no significant difference between Tm of the composites with different Mn of chitosan. From the TGA thermograms, the decomposition temperature at 10% weight loss (Td10) was decreased with increasing chitosan contents. Moreover, the water absorption of PBS/chitosan composites was increased with increasing Mn and content of chitosan.

scholarly journals 1,3-Dioxolan-4-Ones as Promising Monomers for Aliphatic Polyesters: Metal-Free, in Bulk Preparation of PLA

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2396
Author(s):  
Stefano Gazzotti ◽  
Marco Aldo Ortenzi ◽  
Hermes Farina ◽  
Alessandra Silvani
Keyword(s):  
Molecular Weight ◽  
Thermal Properties ◽  
Acid Catalyst ◽  
Monomer Conversion ◽  
Reaction Conditions ◽  
Aliphatic Polyesters ◽  
Metal Free ◽  
Weight Growth ◽  
Double Activation

The first example of solvent-free, organocatalyzed, polymerization of 1,3-dioxolan-4-ones, used as easily accessible monomers for the synthesis of polylactic acid (PLA), is described here. An optimization of reaction conditions was carried out, with p-toluensulfonic acid emerging as the most efficient Brønsted acid catalyst. The reactivity of the monomers in the tested conditions was studied following the monomer conversion by 1H NMR and the molecular weight growth by SEC analysis. A double activation polymerization mechanism was proposed, pointing out the key role of the acid catalyst. The formation of acetal bridges was demonstrated, to different extents depending on the nature of the aldehyde or ketone employed for lactic acid protection. The polymer shows complete retention of stereochemistry, as well as good thermal properties and good polydispersity, albeit modest molecular weight.

scholarly journals Structure, processing and performance of ultra-high molecular weight polyethylene (IUPAC Technical Report). Part 3: deformation, wear and fracture

2020 ◽  
Vol 92 (9) ◽  
pp. 1503-1519
Author(s):  
Clive Bucknall ◽  
Volker Altstädt ◽  
Dietmar Auhl ◽  
Paul Buckley ◽  
Dirk Dijkstra ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Tensile Tests ◽  
Mechanical Tests ◽  
Dominant Factor ◽  
Stress Strain ◽  
Entanglement Density ◽  
Wide Range ◽  
And Performance ◽  
Ultra High Molecular Weight

AbstractThree grades of polyethylene, with weight-average relative molar masses, ${\bar{M}}_{\text{W}}$, of approximately 0.6 × 106, 5 × 106, and 9 × 106, were supplied as compression mouldings by a leading manufacturer of ultra-high molecular weight polyethylene (UHMWPE). They were code-named PE06, PE5, and PE9, respectively. Specimens cut from these mouldings were subjected to a wide range of mechanical tests at 23 °C. In tensile tests, deformation was initially elastic and dominated by crystallinity, which was highest in PE06. Beyond the yield point, entanglement density became the dominant factor, and at 40 % strain, the rising stress–strain curves for PE5 and PE9 crossed the falling PE06 curve. Fracture occurred at strains above 150 %. Differences in stress–strain behaviour between PE5 and PE9 were relatively small. A similar pattern of behaviour was observed in wear tests; wear resistance showed a marked increase when ${\bar{M}}_{\text{W}}$ was raised from 0.6 × 106 to 5 × 106, but there was no further increase when it was raised to 9 × 106. It is concluded that the unexpected similarity in behaviour between PE5 and PE9 was due to incomplete consolidation during moulding, which led to deficiencies in entanglement at grain boundaries; they were clearly visible on the surfaces of both tensile and wear specimens. Fatigue crack growth in 10 mm thick specimens was so severely affected by inadequate consolidation that it forms the basis for a separate report – Part 4 in this series.

The Effect of Matrix Stiffness on the Mechanical Properties of the Composite Reinforced with Multi-Wall Carbon Nanotube

2010 ◽  
Vol 297-301 ◽  
pp. 450-455
Author(s):  
Shiuh Chuan Her ◽  
Shun Wen Yeh
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Stiffness Matrix ◽  
Great Influence ◽  
Tensile Tests ◽  
Mechanical Tests ◽  
Matrix Stiffness ◽  
Mixture Ratio ◽  
Multi Wall Carbon Nanotubes

Carbon nanotubes have shown the superior mechanical, electrical and thermal properties. These outstanding properties as well as a high aspect ratio and low density make carbon nanotubes an ideal reinforcement to develop superior nanocomposites. Mechanical tests indicated that the reinforcement role of carbon nanotubes is affected by the stiffness matrix. It is well known that the degree of cure of the epoxy has great influence on their mechanical properties. In this investigation, the matrix stiffness is controlled by changing the mixture ratio between the epoxy and hardener. Two different contents (1% wt. and 2% wt.) of the multi-wall carbon nanotubes in the epoxy are proposed in this work. Tensile tests are conducted to determine the mechanical properties of the nanocomposites, including the Young’s modulus, yield stress, tensile strength and fracture strain. Experimental results show that the mechanical properties are increasing with the increase of the addition of multi-wall carbon nanotubes. The reinforcement role of the multi-wall carbon nanotubes is decreasing while increasing the stiffness matrix.

scholarly journals The degradation of poly(trimethylene carbonate) implants: The role of molecular weight and enzymes

2015 ◽  
Vol 122 ◽  
pp. 77-87 ◽  
Author(s):  
Liqun Yang ◽  
Jianxin Li ◽  
Wei Zhang ◽  
Ying Jin ◽  
Jinzhe Zhang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Trimethylene Carbonate

scholarly journals Degradability of Polyurethanes and Their Blends with Polylactide, Chitosan and Starch

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1202
Author(s):  
Joanna Brzeska ◽  
Agnieszka Tercjak ◽  
Wanda Sikorska ◽  
Barbara Mendrek ◽  
Marek Kowalczuk ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Weight Loss ◽  
Thermal Properties ◽  
Surface Morphology ◽  
Chemical Modification ◽  
Chemical Structure ◽  
Environmentally Friendly ◽  
Degradation Process ◽  
Cross Linking ◽  
Weight Changes

One of the methods of making traditional polymers more environmentally friendly is to modify them with natural materials or their biodegradable, synthetic equivalents. It was assumed that blends with polylactide (PLA), polysaccharides: chitosan (Ch) and starch (St) of branched polyurethane (PUR) based on synthetic poly([R,S]-3-hydroxybutyrate) (R,S-PHB) would degrade faster in the processes of hydrolysis and oxidation than pure PUR. For the sake of simplicity in the publication, all three modifiers: commercial PLA, Ch created by chemical modification of chitin and St are called bioadditives. The samples were incubated in a hydrolytic and oxidizing environment for 36 weeks and 11 weeks, respectively. The degradation process was assessed by observation of the chemical structure as well as the change in the mass of the samples, their molecular weight, surface morphology and thermal properties. It was found that the PUR samples with the highest amount of R,S-PHB and the lowest amount of polycaprolactone triol (PCLtriol) were degraded the most. Moreover, blending with St had the greatest impact on the susceptibility to degradation of PUR. However, the rate of weight loss of the samples was low, and after 36 weeks of incubation in the hydrolytic solution, it did not exceed 7% by weight. The weight loss of Ch and PLA blends was even smaller. However, a significant reduction in molecular weight, changes in morphology and changes in thermal properties indicated that the degradation of the samples should occur quickly after this time. Therefore, when using these polyurethanes and their blends, it should be taken into account that they should decompose slowly in their initial life. In summary, this process can be modified by changing the amount of R,S-PHB, the degree of cross-linking, and the type and amount of second blend component added (bioadditives).

The Formation of Intermediate Product I in a Purified System The Role of Factor IX or of its Precursor and of a Hageman Factor-PTA Fraction

1961 ◽  
Vol 6 (02) ◽  
pp. 224-234 ◽  
Author(s):  
E. T Yin ◽  
F Duckert
Keyword(s):  
Intermediate Product ◽  
Factor Ix ◽  
Assay Method ◽  
Lag Phase ◽  
Factor X ◽  
Haemophilia B ◽  
Hageman Factor ◽  
One Stage ◽  
The One

Summary1. The role of two clot promoting fractions isolated from either plasma or serum is studied in a purified system for the generation of intermediate product I in which the serum is replaced by factor X and the investigated fractions.2. Optimal generation of intermediate product I is possible in the purified system utilizing fractions devoid of factor IX one-stage activity. Prothrombin and thrombin are not necessary in this system.3. The fraction containing factor IX or its precursor, no measurable activity by the one-stage assay method, controls the yield of intermediate product I. No similar fraction can be isolated from haemophilia B plasma or serum.4. The Hageman factor — PTA fraction shortens the lag phase of intermediate product I formation and has no influence on the yield. This fraction can also be prepared from haemophilia B plasma or serum.

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