scholarly journals The Effect of Mold Conditions on Heat Resistance of Injection-Molded Stereocomplex Polylactide-b-polyethylene Glycol-b-Polylactide Bioplastic

2021 ◽  
Vol 58 (3) ◽  
pp. 11-22
Author(s):  
Yodthong Baimark ◽  
Wuttipong Rungseesantivanon ◽  
Natcha Prakymoramas
Keyword(s):  
Polyethylene Glycol ◽  
Heat Resistance ◽  
Softening Temperature ◽  
Mold Temperature ◽  
Mechanical Analysis ◽  
Cooling Time ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Injection Molded ◽  
Good Heat

The effect of mold conditions was investigated in terms of mold temperature (30oC and 90oC) and cooling time (30 s and 60 s) on the heat resistance of injection-molded bars for stereocomplex polylactide-b-polyethylene glycol-b-polylactide (scPLA-PEG-PLA). Comparative study was performed for poly(L-lactide) (PLLA) and PLLA-b-PEG-b-PLLA (PLLA-PEG-PLLA). scPLA-PEG-PLA was 90/10 (w/w) PLLA-PEG-PLLA/poly(D-lactide) blend. scPLA-PEG-PLA exhibited the easiest crystallization upon cooling scan as shown by differential scanning calorimetry (DSC). Higher mold-temperature and longer cooling-time induced higher degree of crystallinity as assessed by X-ray diffractometry (XRD) except for PLLA bars. The heat resistance of both PLLA-PEG-PLLA and scPLA-PEG-PLA bars was improved with increased mold-temperature and cooling-time as shown by dynamic mechanical analysis (DMA), vicat softening temperature (VST) and heat distortion-resistance tests except for PLLA bars. In conclusion, the heat resistance of injection-molded bars prepared at 90˚C mold temperature was in the order scPLA-PEG-PLA ] PLLA-PEG-PLLA ] PLLA. The results suggested that flexible PLLA-PEG-PLLA and scPLA-PEG-PLA with high degrees of crystallinity were successfully obtained by injection molding for use as good heat-resistant bioplastic products.

scholarly journals Post-Processing Time Dependence of Shrinkage and Mechanical Properties of Injection-Molded Polypropylene

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 22
Author(s):  
Artur Kościuszko ◽  
Dawid Marciniak ◽  
Dariusz Sykutera
Keyword(s):  
Mechanical Properties ◽  
Impact Strength ◽  
Injection Molding ◽  
Accelerated Aging ◽  
Mold Temperature ◽  
Degree Of Crystallinity ◽  
Injection Mold ◽  
Secondary Crystallization ◽  
Scanning Calorimetry ◽  
Injection Molded

Dimensions of the injection-molded semi-crystalline materials (polymeric products) decrease with the time that elapses from their formation. The post-molding shrinkage is an effect of secondary crystallization; the increase in the degree of polymer crystallinity leads to an increase in stiffness and decrease in impact strength of the polymer material. The aim of this study was to assess the changes in the values of post-molding shrinkage of polypropylene produced by injection molding at two different temperatures of the mold (20 °C and 80 °C), and conditioned for 504 h at 23 °C. Subsequently, the samples were annealed for 24 h at 140 °C in order to conduct their accelerated aging. The results of shrinkage tests were related to the changes of mechanical properties that accompany the secondary crystallization. The degree of crystallinity of the conditioned samples was determined by means of density measurements and differential scanning calorimetry. It was found that the changes in the length of the moldings that took place after removal from the injection mold were accompanied by an increase of 20% in the modulus of elasticity, regardless of the conditions under which the samples were made. The differences in the shrinkage and mechanical properties of the samples resulting from mold temperature, as determined by tensile test, were removed by annealing. However, the samples made at two different injection mold temperature values still significantly differed in impact strength, the values of which were clearly higher for the annealed samples compared to the results determined for the samples immediately after the injection molding.

scholarly journals Preparation and Characterization of Talc Filled Thermoplastic Polyurethane/Polypropylene Blends

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Emi Govorčin Bajsić ◽  
Vesna Rek ◽  
Ivana Ćosić
Keyword(s):  
Thermal Properties ◽  
Thermoplastic Polyurethane ◽  
Mechanical Analysis ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Polypropylene Blends ◽  
Pp Blends ◽  
The Degree Of Crystallinity ◽  
Better Than

The effect of the addition of talc on the morphology and thermal properties of blends of thermoplastic polyurethane (TPU) and polypropylene (PP) was investigated. The blends of TPU and PP are incompatible because of large differences in polarities between the nonpolar crystalline PP and polar TPU and high interfacial tensions. The interaction between TPU and PP can be improved by using talc as reinforcing filler. The morphology was observed by means of scanning electron microscopy (SEM). The thermal properties of the neat polymers and unfilled and talc filled TPU/PP blends were studied by using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The addition of talc in TPU/PP blends improved miscibility in all investigated TPU/T/PP blends. The DSC results for talc filled TPU/PP blends show that the degree of crystallinity increased, which is due to the nucleating effect induced by talc particles. The reason for the increased storage modulus of blends with the incorporation of talc is due to the improved interface between polymers and filler. According to TGA results, the addition of talc enhanced thermal stability. The homogeneity of the talc filled TPU/PP blends is better than unfilled TPU/PP blends.

scholarly journals Formation of Polyethylene Glycol Particles Using a Low-Temperature Supercritical Assisted Atomization Process

Molecules ◽  
2019 ◽  
Vol 24 (12) ◽  
pp. 2235
Author(s):  
Hsien-Tsung Wu ◽  
Hong-Ming Tsai ◽  
Tsung-Hsuan Li
Keyword(s):  
Carbon Dioxide ◽  
Molecular Weight ◽  
Polyethylene Glycol ◽  
Low Temperature ◽  
Flow Rate ◽  
Fine Particles ◽  
Volumetric Flow Rate ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Rate Ratios

Polyethylene glycol (PEG) particles were prepared using low-temperature supercritical assisted atomization (LTSAA) with carbon dioxide as the spraying medium or the co-solute and acetone as the solvent. The effects of several key factors on the particle size were investigated. These factors included the concentration of the PEG solution, precipitator temperature, saturator temperature, ratio of the volumetric flow rate of carbon dioxide to the PEG solution, and the molecular weight of PEG. Spherical and non-aggregated PEG particles, with a mean size of 1.7–3.2 µm, were obtained in this study. The optimal conditions to produce fine particles were found to be a low concentration of the PEG solution, a low precipitator temperature, and low molecular weight of the PEG. The phase behavior of the solution mixture in the saturator presented a qualitative relationship. At the optimized volumetric flow rate ratios, the composition of CO2 in the feed streams was near the bubble points of the saturator temperatures. X-ray and differential scanning calorimetry analyses indicated that LTSAA-treated PEG had a reduced degree of crystallinity, which could be modulated via the precipitator temperature. PEG microparticles prepared by a LTSAA process would be promising carriers for drug-controlled formulations of PEG-drug composite particles.

Phase Behavior and Properties of Polyurethane-PVC Blends and Fibers

1999 ◽  
Vol 72 (4) ◽  
pp. 587-601 ◽  
Author(s):  
Zoran S. Petrović ◽  
Ivan Javni ◽  
Jonathan Shull ◽  
Alan Waddon
Keyword(s):  
Thermomechanical Analysis ◽  
Mechanical Analysis ◽  
Degree Of Crystallinity ◽  
Polyurethane Elastomer ◽  
Scanning Calorimetry ◽  
Polyester Urethane ◽  
Elastomeric Matrix ◽  
Low Concentrations ◽  
Rigid Poly ◽  
High Degree

Abstract A polyester urethane elastomer is blended with rigid poly(vinyl chloride) (PVC) and the miscibility of the components studied over the entire range of compositions. The polyurethane elastomer was a block copolymer with a low degree of crystallinity, while PVC was practically amorphous. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA) methods showed that polyester urethanes were partially miscible with PVC since two distinct glass transitions, which changed with the change of concentration of components, were observed. Although the PVC content was varied from 0–100%, the aim of the work was to examine if PVC at low concentrations would form fibrils in the urethane matrix and act as a reinforcing agent for the polyurethane elastomer. The morphology of the blends was studied by scanning electron microscopy and x-ray scattering. The blends were then spun into fibers to force the dispersed phase to elongate and form fibrils (draw ratio was about 100). A high degree of miscibility is obtained at low concentration of either of the components. The PVC phase in fibers spun from the blends have higher glass-transition temperature (Tg) than in isotropic blends, presumably due to increased orientation. No fibrillation of the rigid phase in the elastomeric matrix could be observed. The fibers displayed higher strengths but lower elongation at break than the isotropic blends of the same composition. Intermeshing morphology (at about 50/50 concentration) gave the lowest strengths.

scholarly journals Influence of the Lignin Content on the Properties of Poly(Lactic Acid)/lignin-Containing Cellulose Nanofibrils Composite Films

Polymers ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1013 ◽  
Author(s):  
Xuan Wang ◽  
Yuan Jia ◽  
Zhen Liu ◽  
Jiaojiao Miao
Keyword(s):  
Lactic Acid ◽  
Lignin Content ◽  
Cellulose Nanofibrils ◽  
Composite Films ◽  
Tensile Tests ◽  
Nucleating Agent ◽  
Mechanical Analysis ◽  
Degree Of Crystallinity ◽  
Poly Lactic Acid ◽  
Scanning Calorimetry

Poly(lactic acid) (PLA)/lignin-containing cellulose nanofibrils (L-CNFs) composite films with different lignin contents were produced bythe solution casting method. The effect of the lignin content on the mechanical, thermal, and crystallinity properties, and PLA/LCNFs interfacial adhesion wereinvestigated by tensile tests, thermogravimetric analysis, differential scanning calorimetry (DSC), dynamic mechanical analysis, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The tensile strength and modulus of the PLA/9-LCNFs (9 wt % lignin LCNFs) composites are 37% and 61% higher than those of pure PLA, respectively. The glass transition temperature (Tg) decreases from 61.2 for pure PLA to 52.6 °C for the PLA/14-LCNFs (14 wt % lignin LCNFs) composite, and the composites have higher thermal stability below 380 °C than pure PLA. The DSC results indicate that the LCNFs, containing different lignin contents, act as a nucleating agent to increase the degree of crystallinity of PLA. The effect of the LCNFs lignin content on the PLA/LCNFs compatibility/adhesion was confirmed by the FTIR, SEM, and Tg results. Increasing the LCNFs lignin content increases the storage modulus of the PLA/LCNFs composites to a maximum for the PLA/9-LCNFs composite. This study shows that the lignin content has a considerable effect on the strength and flexibility of PLA/LCNFs composites.

scholarly journals Preparation of Biodegradable Polyethylene Glycol Dimethacrylate Hydrogels via Thiol-ene Chemistry

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1339 ◽  
Author(s):  
Gavin Burke ◽  
Zhi Cao ◽  
Declan M. Devine ◽  
Ian Major
Keyword(s):  
Polyethylene Glycol ◽  
Monomer Concentration ◽  
Mechanical Analysis ◽  
Glycol Dimethacrylate ◽  
Unconfined Compression ◽  
Scanning Calorimetry ◽  
Drug Delivery Vehicles ◽  
Degradation Rates ◽  
Delivery Vehicles ◽  
Cell Carriers

Through the control of the molecular weight, water content and monomer concentration, polyethylene glycol dimethacrylate (PEGDMA) based hydrogels have been adapted for numerous applications, including as structural scaffolds, drug delivery vehicles and cell carriers. However, due to the low biodegradability rates, the use of PEGDMA in tissue engineering has been limited. Thiol-based monomers have been shown to improve the degradation rates of several PEG-based hydrogels, though their impact on several material properties has not been as well defined. In this work, several mercaptopropianoates, as well as mercaptoacetates, were mixed with PEGDMA and copolymerized. Following an initial polymerization check, it was determined that mercaptoacetate-based thiol monomers did not polymerize in the presence of PEGDMA, whereas mercaptopropionates were more successful. The wettability, and the compressive and tensile strength, in addition to the thermal properties, were determined for successfully copolymerized samples via a combination of differential scanning calorimetry, dynamic mechanical analysis, unconfined compression, and goniometry. Further study determined that dipentaerythritol hexa(3–mercaptopropionate) (DiPETMP) successfully enhanced the biodegradability of PEGDMA.

Thermal, morphological and mechanical properties of composites based on polyamide 6 with cellulose, silica and their hybrids from rice husk

2020 ◽  
pp. 002199832097829
Author(s):  
Renato P Melo ◽  
Marcelo P da Rosa ◽  
Paulo H Beck ◽  
Lucas GP Tienne ◽  
Maria de Fátima V Marques
Keyword(s):  
Mechanical Properties ◽  
Rice Husk ◽  
Natural Fibers ◽  
Polyamide 6 ◽  
Mechanical Analysis ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Cellulosic Fibers ◽  
The One ◽  
Properties Of Composites

The use of cellulosic fibers from different natural sources as fillers in polymer matrices to improve their properties has been extensively studied in the last years. It is mainly due to the vast availability of natural fibers as well as their biodegradability. The purpose of this present work was to extract cellulose, silica, and cellulose-silica fillers – these last called “hybrids” – from rice husk through delignification and subsequent oxidation and, then, prepare composites with polyamide 6 and improve mainly its thermal-mechanical properties. The content of 10 wt.% of fillers was inserted in PA 6 matrix. Infrared spectroscopy pointed the main characteristic peaks of cellulose and silica of hybrids, as thermogravimetric analysis showed high thermal stability of fillers, allowing their incorporation in PA-6 matrix by extrusion method. Thermo dynamic-mechanical analysis showed, in a general overview, a significant improvement of mechanical properties of composites, as elastic modulus, compared with neat polyamide-6, mainly the one with 2.5 wt% of silica and 7.5% of cellulose. This last also showed increasing of degree of crystallinity, measured by differential scanning calorimetry, showing the extraction efficiency of fillers from rice husk as well as the potential application of composites as structural components in automotive parts.

Study on the Mechanism of the Soybean Adhesive Improved by Micro/Nano Fibrils and the Bond Strength of the Poplar Plywood with it

2012 ◽  
Vol 174-177 ◽  
pp. 1152-1158
Author(s):  
Cong Liu ◽  
Yang Zhang ◽  
Wen Ding Li
Keyword(s):  
Differential Scanning Calorimetry ◽  
Bond Strength ◽  
Heat Resistance ◽  
Dynamic Mechanical Analysis ◽  
Bonding Strength ◽  
Mechanical Analysis ◽  
Scanning Calorimetry ◽  
Dynamic Mechanical

The micro/nano fibrils was used to modify the soybean glue, which was used as the adhesive of poplar plywood. The poplar plywood bond strength were evaluated. To explain the improvement in mechanism, Differential Scanning Calorimetry(DSC) and Dynamic Mechanical Analysis apparatus(DMA) were applied to analyze the influence of poplar macro/nano fibrils on soybean glue. The test of bonding strength results show that the bond strength of poplar plywood was enhanced as micro/nano poplar fibrils was added. And the DMA figures of soybean glue illustrate that poplar macro/nano fibrils has improved the deformation resistence of soybean glue plywood and the heat resistance of soybean glue.

scholarly journals Effect of polyethylene glycol mixtures as ointment base on the physicochemical properties of Lavsan atraumatic wound dressings

2019 ◽  
Vol 14 (5) ◽  
pp. 71-78
Author(s):  
A. A. Korolchuk ◽  
E. S. Zhavoronok ◽  
O. A. Legonkova ◽  
S. A. Kedik
Keyword(s):  
Polyethylene Glycol ◽  
Flow Behavior ◽  
Wound Dressings ◽  
Degree Of Crystallinity ◽  
Polyethylene Glycols ◽  
Dynamic Mode ◽  
Scanning Calorimetry ◽  
Rotational Viscometer ◽  
Molecular Weights ◽  
Ointment Base

Objectives. Modern atraumatic wound dressings are based on polyethylene terephthalate, or Lavsan, which is shaped to form threads. The aim of the study was to determine the reasons for Lavsan woven nets’ hardening and becoming more trauma-prone during storage, and to find ways of eliminating these effects.Methods. We used differential scanning calorimetry, performed on a NETZSCH DSС 204 F1 Phoenix device, in a dynamic mode with a temperature range from 20 to 300 °C in argon flow to determine phase states, glass transition temperatures, and melting temperatures of Lavsan fibers (including those treated with polyethylene glycol mixtures). We performed rheoviscometry studies on a Brookfield DV2TLV rotational viscometer, with a SC4-16 thermostatic control unit, at the following temperatures: 25, 36.6, 40, 45, 50, and 55 °C, with shear rates ranging from 120 to 200 s–1 to determine dynamic viscosity and investigate the mixing characteristics of polyethylene glycols with different molecular weights.Results. We have established that samples of Lavsan woven nets, stored long-term in laboratory conditions (up to 2, 3, and 16 years), are in the crystalline state with a high degree of crystallinity. Upon heating these nets to 300 °C, it is possible to reduce the degree of crystallinity by 19–32%, but it does not completely eliminate the effect. Polyethylene glycols and their mixtures which exhibit non-Newtonian flow behavior and are used as an ointment base, have a significant effect on Lavsan’s crystallinity. We have determined that the optimal ratio of polyethylene glycols for the modification of Lavsan nets is PEG-400:PEG-1500 = 80:20 wt %. Upon storing Lavsan woven nets in this mixture at room temperature, the Lavsan’s crystallinity is greatly reduced, and upon heating the system, the crystallinity practically disappears.Conclusions. The effect of polyethylene glycol mixtures (the base for therapeutic ointments) with various molecular weights on the phase organization of Lavsan has been evaluated. As a result of this study, we can offer a new approach to reduce the injuring effect of synthetic (Lavsan) bases of atraumatic wound dressings.

scholarly journals From disposal to sustainable development: technological potential of poly(lactic acid) (PLA) blends with 3D filament waste

2020 ◽  
Vol 9 (12) ◽  
pp. e13291210767
Author(s):  
Wellerson Salomão Diniz Marinho ◽  
Carlos Bruno Barreto Luna ◽  
Edcleide Maria Araújo ◽  
Carlos Heitor de Andrade Lustosa ◽  
Celso Rosendo Bezerra Filho ◽  
...  
Keyword(s):  
Sustainable Development ◽  
Softening Temperature ◽  
Nucleating Agent ◽  
Degree Of Crystallinity ◽  
Poly Lactic Acid ◽  
Continuous Growth ◽  
Technological Potential ◽  
Twin Screw ◽  
Injection Molded ◽  
The Degree Of Crystallinity

Additive manufacturing is growing rapidly in the automotive, medical, and aerospace industries as an option for the manufacturing of products. However, there is a continuous growth in the amount of waste generated by 3D filaments, thus, the reuse practice becomes important, since it brings environmental and economic gains. The present research evaluated the mechanical, thermal, thermomechanical and rheological properties of PLA/PLAr blends containing post-consumption 3D filament. The blends were prepared in a co-rotational twin screw extruder and, subsequently, the extruded granules were injection molded. As the PLAr content in the blends (PLA/PLAr) increased, there was a reduction in viscosity, indicating an improvement in manufacturability. The PLA/PLAr blend (75/25 % wt.) increased the degree of crystallinity compared to neat PLA, indicating that PLAr acted as a nucleating agent. As a consequence, the PLA/PLAr blend (75/25 % wt.) showed performance comparable to neat PLA in thermal stability, elastic modulus, tensile strength, Shore D hardness, impact strength, heat deflection temperature (HDT) and Vicat softening temperature. The reuse of post-consumption 3D filament PLA is feasible for the development of materials with good properties. In addition, value is added to the post-consumption material and there is a contribution to sustainable development.

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