scholarly journals Thermal properties of radiolytically synthesized PVA/Ag nanocomposites

2007 ◽  
Vol 61 (3) ◽  
pp. 129-134 ◽  
Author(s):  
Aleksandra Krkljes ◽  
Zorica Kacarevic-Popovic
Keyword(s):  
Thermal Properties ◽  
Heating Rate ◽  
Melting Temperature ◽  
Melting Behavior ◽  
Melting Peak ◽  
Degree Of Crystallinity ◽  
High Heating Rate ◽  
Half Time ◽  
The Degree Of Crystallinity ◽  
Peak Melting Temperature

The radiolytic method was used to synthesize two types of nanocomposites with silver, PVA/Ag by film casting and PVA hydrogel/Ag nanocomposites. This method is particularly suitable for generating metal nanoparticles in solution. The radiolytic species (solvated electrons and secondary radicals) exhibit strong reducing properties such that metal ions are reduced at each encounter. Metal atoms then tend to grow into larger clusters. It was found that solid or swollen polymers are able to stabilize small crystallites against spontaneous growth via aggregation. Using differential scanning calorimetry (DSC), the melting behavior and kinetics of the PVA/Ag nanocomposites were investigated and compared to those of pure PVA. The melting as well as crystallization behavior of polymers is crucial because it governs the thermal properties, impact resistance and stress strain properties. Understanding the melting behavior is significant not only to tailor the properties of nanocomposites but to investigate the interactions between the constituents. The DSC curves of pure PVA and prepared nanocomposites show only one melting peak between 175 and 230?C, indicating that the melting behavior of these two systems are analogous. In both cases, with increasing heating rate, the melting peak shifts to a higher temperature, but with increasing Ag content the peak melting temperature is lower. When specimens are heated at high heating rate, the motion of PVA molecular chains cannot follow the heating temperature on time due to the influence of heat hysteresis, which leads to a higher peak melting temperature. When Ag nanoparticles are added they increase the heat transfer among the PVA molecular chains decreasing the melting temperature. The Ag content is a major factor affecting the degree of crystallinity. It was observed that at low nanofiller content, up to the 0.5 wt%, the degree of crystallinity of the nanocomposites increased, while at a higher content the crystallization was retarded. The half time of melting is non-linearly dependent on the amount of nanofiller. In the range from 0.25 to 1 wt% Ag it slightly increases, because at a low Ag content the nanoparticles act as a heterogeneous nucleation agent during the crystallization process. For large amounts of nanofiller, the half time of melting is markedly higher than for pure PVA. At a higher Ag content, the nanoparticles act as a barrier that restricts the thermal motion of PVA molecular chains and the half time of complete melting increases. The significantly lower melting activation energy of the nanocomposites with high amount of nanofiller compared to pure PVA, calculated by the Kissinger method, indicated that nanoparticles reduced the heat barrier for the melting process. .

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.

Regenerated cellulose fibers from waste bagasse using ionic liquid

2011 ◽  
Vol 81 (18) ◽  
pp. 1949-1958 ◽  
Author(s):  
Wei Jiang ◽  
Liangfeng Sun ◽  
Ayou Hao ◽  
Jonathan Yan Chen
Keyword(s):  
Ionic Liquid ◽  
Thermal Properties ◽  
Cellulose Fibers ◽  
Degree Of Crystallinity ◽  
Coagulation Bath ◽  
Regenerated Cellulose ◽  
Wood Fibers ◽  
Liquid Residue ◽  
Regenerated Fibers ◽  
The Degree Of Crystallinity

Regenerated cellulose fibers from bagasse and wood were produced under various processing conditions using the ionic liquid 1-butyl-3-methylimidazolium chloride (BMIMCl) as a solvent. Two different ionic liquid solutions were prepared with 6 wt% of bagasse cellulose and 6 wt% of wood cellulose. The solutions were extruded with a dry-jet and wet-spinning method using water as a coagulation bath. A thermogravimetric analyzer (TGA) was used to measure the thermal properties of these regenerated fibers. Dynamic mechanical analysis (DMA) was used to determine the thermal mechanical property of the regenerated cellulose fibers and wide-angle X-ray diffraction (WAXD) was used to measure the degree of crystallinity, as well as the degree of crystal orientation for those experimental fibers. To evaluate the quantity of ionic liquid residue in the regenerated fibers, the instrumental methods of FT-IR and mass spectrometry were applied to test the residues of BMIMCl in the regenerated fibers. Research results indicated increases in the degree of crystallinity and storage modulus under a higher fiber drawing speed. Both regenerated bagasse film and regenerated wood film had similar thermal properties. However, the regenerated bagasse fibers showed a higher degree of crystallinity, and higher tenacity than the regenerated wood fibers obtained under the same condition. The study also revealed that water treatment would be helpful for eliminating the ionic liquid residue in the regenerated fibers.

scholarly journals LMPP Effects on Morphology, Crystallization, Thermal and Mechanical Properties of iPP/LMPP Blend Fibres

2018 ◽  
Vol 26 (2(128)) ◽  
pp. 26-31 ◽  
Author(s):  
Munir Hussain ◽  
Feichao Zhu ◽  
Feichao Zhu ◽  
Bin Yu ◽  
Bin Yu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Properties ◽  
Elastic Modulus ◽  
Isotactic Polypropylene ◽  
Degree Of Crystallinity ◽  
Thermal And Mechanical Properties ◽  
Elongation At Break ◽  
Breaking Elongation ◽  
Low Modulus ◽  
The Degree Of Crystallinity

The thermal properties and morphological characterisation of isotactic polypropylene (iPP) homopolymer and its blends with low molecular low modulus polypropylene (LMPP) were studied. Firstly blends were prepared with variant LMPP contents, and their properties were characterised using SEM, DSC, XRD, and DMA. Later the mechanical properties of iPP/LMPP blend fibres were investigated. SEM results showed that the iPP/LMPP blends produced smoother surfaces when the LMPP content was increased, as well as the miscibility. All the Tg values with different LMPP percentages were in-between pure iPP and LMPP. The XRD results indicated the LMPP percentage decreased along with the degree of crystallinity of the iPP/LMPP blends (5% to 15%), which increased and then decreased as compared to pure iPP. The elongation at break increased when the LMPP content increased, with the maximum breaking elongation of the LMPP 25% blend reaching 12.95%, which showed great stretch-ability, whereas the elastic modulus of iPP/LMPP blends decreased.

scholarly journals Effect of PVA-co-MMA Copolymer on the Physical, Mechanical, and Thermal Properties of Tropical Wood Materials

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Md. Saiful Islam ◽  
Sinin Hamdan ◽  
Mansor B. Ahmad ◽  
Mahbub Hasan ◽  
Azman Hassan ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Sem Analysis ◽  
Degree Of Crystallinity ◽  
Mechanical And Thermal Properties ◽  
X Ray Diffraction ◽  
Electron Microscopic ◽  
Tropical Wood ◽  
Wood Polymer ◽  
Wood Polymer Composites ◽  
The Degree Of Crystallinity

The present study demonstrates the effect of copolymer on the physical, mechanical, and thermal properties of tropical wood and wood polymer composites (WPCs). Mixed monomers of methyl methacrylate (MMA) and polyvinyl alcohol (PVA) were effectively impregnated into the cellular structure of several types of tropical wood, which then underwent a catalyst-thermal process to polymerize and form WPC. The manufacturing of WPC was confirmed through Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopic (SEM) analysis. The SEM observation showed that polymer converted from monomers filled up wood cell cavities and tightly interacted with wood matrix. The X-ray diffraction results reveal that the degree of crystallinity was significantly improved upon impregnation with PVA-co-MMA copolymer. The modulus of elasticity (MOE) and compressive modulus were found to be significantly higher after treatment with MMA/PVA indicating improvement of mechanical properties of the wood samples. In addition, the modified WPC had lower water absorption compared to their corresponding raw samples. It is interesting to note that thermogravimetric (TGA) analysis shows an extensive improvement in thermal properties of WPC.

scholarly journals Studies of properties of polypropylene/halloysite composites

2011 ◽  
Vol 13 (3) ◽  
pp. 61-65 ◽  
Author(s):  
Agnieszka Szczygielska ◽  
Jacek Kijeński
Keyword(s):  
Mechanical Properties ◽  
Thermal Properties ◽  
Polymer Composites ◽  
Degree Of Crystallinity ◽  
Mechanical And Thermal Properties ◽  
Thermal And Mechanical Properties ◽  
Polypropylene Composites ◽  
Modification Method ◽  
The Degree Of Crystallinity

Studies of properties of polypropylene/halloysite compositesThe results of the studies on the synthesis, mechanical and thermal properties of polypropylene composites with various amount of halloysite filler are presented. Halloysite (HNT) belongs to the silica type characterized by a two-layer 1:1 structure. This work was aimed to develop a method for the modification of halloysite in its prime use as a filler for polypropylene by extrusion. The composites contain 1, 3, 5 and 7 wt.% of HNT. The degree of crystallinity of the composites decrease with increasing halloysite content. The results confirm the expectations that composites of interesting physicochemical, mechanical and thermal properties can be obtained. The mechanical properties studied show that the filler modification method used leads to the synthesis of polymer composites of improved thermal and mechanical properties.

The Effect of Curing on the Thermomechanical Properties of BPDA-PDA Polyimide Thin Films

1993 ◽  
Vol 323 ◽  
Author(s):  
J. Leu ◽  
Y. S. Kang ◽  
H. C. Liou ◽  
P. S. Ho
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Mechanical Strength ◽  
Heating Rate ◽  
Thermomechanical Properties ◽  
Degree Of Crystallinity ◽  
High Heating Rate ◽  
Molecular Order ◽  
Chain Orientation ◽  
High Heating

AbstractThe effect of the heating rate during curing on the thermal expansivity and mechanical properties of poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) polyimide thin films has been investigated in the range from 3 to 40 μm, which is commonly used for packaging application. Structural characterization was carried out using birefringence and wide-angle x-ray diffraction (WAXD) techniques. The morphology and packing order are found to be strongly influenced by the heating rate and, to a lesser extent, by the film thickness. The themomechanical properties of the polyimide films show an overall variation consistent with the changes in the molecular packing, thus demonstrating a close structure-property correlation. For slow-cure films, the variation of the molecular order is almost independent of film thickness. In contrast, the molecular order for the fast-cured films strongly depends on the thickness. The in-plane chain orientation decreases, but crystallinity increases with increasing film thickness. The heating rate gives rise to an opposite effect on the morphology for thin (∼ 5 μm) and thick films (∼ 38 μm). For thin films, high heating rate yields a high degree of crystallinity and in-plane chain orientation of the polymeric chains, leading to low thermal expansion coefficient (TEC) and high mechanical strength. In contrast, high heating rate for the thicker film gives a low in-plane chain orientation, leading to high TEC and low mechanical strength. The close correlation between morphology and the thermomechanical properties such as Young's modulus, stress-strain relationship, and lateral TEC is demonstrated.

scholarly journals Crystallization and Melting Behavior of Biodegradable Poly(L-lactic acid)/Talc Composites

2012 ◽  
Vol 9 (3) ◽  
pp. 1569-1574 ◽  
Author(s):  
Yan-Hua Cai
Keyword(s):  
Lactic Acid ◽  
Heating Rate ◽  
Isothermal Crystallization ◽  
Crystallization Rate ◽  
Melting Behavior ◽  
Melting Peak ◽  
Melt Crystallization ◽  
Biodegradable Poly ◽  
Crystallization And Melting Behavior ◽  
Double Melting Peak

Crystallization and melting behavior of Poly(L-lactic acid)(PLLA)/Talc composites with different talc content were investigated in detail. The addition of talc can increase the overall crystallization rate of PLLA, 5%talc makes the melt-crystallization peak temperature of PLLA increase from 96.28 °C to 105.22 °C, and the crystallization enthalpy increases from 1.379 J•g-1to 28.99 J•g-1. The melting behavior of PLLA/5%talc composites at a different heating rate during non-isothermal crystallization at different cooling rate shows that heating rate can affect the melting behavior of PLLA, with increasing of heating rate, the double melting peak degenerates to single melting peak. Melting behavior after isothermal crystallization and after cold isothermal crystallization and hot isothermal crystallization indicates that the double-melting peak of PLLA/5%talc composites results from melting-recrystallization.

scholarly journals Effects of ZnO crystals synthesized in presence of CMI biopolymer on PHBV properties

2017 ◽  
Vol 89 (1) ◽  
pp. 89-96
Author(s):  
Tugce Bekat ◽  
Mualla Oner
Keyword(s):  
Melting Temperature ◽  
Chemical Precipitation ◽  
Particle Dispersion ◽  
Degree Of Crystallinity ◽  
Precipitation Method ◽  
Elongation At Break ◽  
Zno Particles ◽  
The Degree Of Crystallinity ◽  
Extrusion Method ◽  
Lateral Axis

AbstractRod-shaped ZnO crystals were synthesized by chemical precipitation method from aqueous solution. Carboxymethyl inulin (CMI) was used as an additive in ZnO synthesis reaction, and particles with differing sizes and structures were obtained. CMI hindered crystal growth in the length axis of the rods, while growth on the lateral axis was not suppressed. ZnO crystals synthesized with varying CMI concentrations were incorporated into PHBV (3-polyhydroxybutyrate-co-3-hydroxyvalerate) matrix and the effect of the particles on thermal and mechanical properties of the polymer were investigated. Considerably good particle dispersion was obtained in the polymer matrix by melt-extrusion method. ZnO particles did not seem to affect main crystal structure, melting temperature and crystallization temperature of PHBV, whereas they had a retarding effect on crystallization. The addition of ZnO particles into PHBV increased elongation at break and toughness values, along with the decrease in the degree of crystallinity. Tensile strength was also increased without a significant change on the stiffness. Thermal degradation temperatures were observed to slightly decrease with ZnO addition compared to neat PHB; however, degradation peak temperature was still considerably above the melting temperature of the polymer.

scholarly journals Physical Properties of Biodegradable Poly(L-lactide) Induced by N, N -Bis(Benzoyl) 1, 3-Cyclohexanedicarboxylic Acid Dihydrazide as Crystallinity Additive

2021 ◽  
Vol 58 (2) ◽  
pp. 48-59
Author(s):  
Li-Sha Zhao ◽  
Ting Deng ◽  
Jun Qiao ◽  
Yan-Hua Cai
Keyword(s):  
Cooling Rate ◽  
Heating Rate ◽  
Melting Temperature ◽  
Crystallization Process ◽  
Melting Behavior ◽  
Cold Crystallization ◽  
Light Transmittance ◽  
Melt Crystallization ◽  
Crystallization Peak ◽  
Crystallization Ability

This work is aimed at synthesizing an organic compound N, N -bis(benzoyl) 1,3-cyclohexane-dicarboxylic acid dihydrazide (CABH) to focus on its effect on the non-isothermal crystallization of poly(L-lactide) (PLLA), meanwhile the melting behavior, thermal decomposition process and optical property of PLLA/CABH samples in different CABH concentrations were also investigated. It was found that CABH acted as efficient heterogeneous nucleating agent for inducing PLLA�s crystallization through comparative analysis of melt-crystallization process of the virgin PLLA with PLLA/CABH samples, and a high amount of CABH played a much more significant role in promoting PLLA�s crystallization. Additionally, the melt-crystallization processes also showed that both the cooling rate and the final melting temperature affected the crystallization behavior of PLLA, an increase of cooling rate could weaken the crystallization ability of PLLA/CABH samples, and the final melting temperature of 180�C made PLLA/CABH exhibit the best crystallization ability. For the cold-crystallization process, the cold-crystallization peak became flatter and shifted toward the lower temperature with increasing of CABH concentration, but an increase of heating rate could prevent the cold-crystallization peak from moving to low temperature because of the thermal inertia. The melting behaviors of PLLA/CABH depended on the previous crystallization and heating rate in heating, and the difference in melting behavior of PLLA/CABH samples effectively reflected the nucleation role of CABH, as well as the double melting peaks behavior of PLLA/CABH was thought to due to the melting-recrystallization. The introduction of CABH led to a drop in light transmittance, moreover, this negative effect were more obvious with an increase of CABH loading. In contrast, the fluidity of PLLA was significantly enhanced due to the existence of CABH.

Thermal properties and product distribution from pyrolysis at high heating rate of Naomaohu coal

Fuel ◽  
2021 ◽  
Vol 292 ◽  
pp. 120238
Author(s):  
Tianju Chen ◽  
Ke Zhang ◽  
Mo Zheng ◽  
Shuangxia Yang ◽  
Dominic Yellezuome ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Heating Rate ◽  
Product Distribution ◽  
High Heating Rate ◽  
High Heating
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