scholarly journals Microstructure and Damping Property of Polyurethane Composites Hybridized with Ultraviolet Absorbents

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Jiang Chang ◽  
Bing Tian ◽  
Li Li ◽  
Yufeng Zheng
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Crystalline State ◽  
Interfacial Bonding ◽  
Damping Factor ◽  
Damping Property ◽  
Temperature Range ◽  
The Matrix ◽  
Polyurethane Composites

This article investigated the microstructure and damping property of TPU composites with different contents of ultraviolet absorbents. It can be found that the ultraviolet absorbents formed fiber-shaped precipitations in the TPU matrix. The UV-328 was randomly distributed in the matrix and exhibited a weak interfacial bonding with the matrix. In comparison, the UV-329 was well embedded in the matrix and formed a relatively better interfacial bonding and compatibility with the TPU matrix. The damping factor tanδ of both 328-composites and 329-composites had been reduced gradually with increasing content of ultraviolet absorbents at the glass transition temperature range due to the fact that the ultraviolet absorbents were in the crystalline state which decreased the volume content of the viscoelastic TPU matrix. But the tanδ increased at the temperature range of higher than the glass transition temperature, which should be related to the dominance of interfacial frictions between the ultraviolet absorbents and the matrix on the energy absorption.

Study on the Crystallization Activation Energy of Poly (L-lactic acid) Nucleated with P-tert-butylcalix[8]arene

2018 ◽  
Vol 26 (2) ◽  
pp. 169-175
Author(s):  
Yaoqi Shi ◽  
Liang Wen ◽  
Zhong Xin
Keyword(s):  
Activation Energy ◽  
Lactic Acid ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Crystallization Temperature ◽  
Nucleating Agent ◽  
Crystallization Activation Energy ◽  
Temperature Range ◽  
Chain Mobility

The crystallization activation energy (Δ E) of a polymer comprises the nucleation activation energy Δ F and the transport activation energy Δ E*. In this paper, the Δ E of poly (L-lactic acid) (PLLA) nucleated with nucleating agent p- tert-butylcalix[8]arene (tBC8) was calculated. The results showed that the Δ E of nucleated PLLA was 165.97 kJ/mol, which is higher than that of pure PLLA. The reason why Δ E of PLLA increased when incorporating nucleating agent was studied. The increment of glass transition temperature ( Tg) for nucleated PLLA revealed that the polymer chain mobility was restricted by tBC8, which was considered as the reason for the increase of Δ E*. Further, polyethylene glycol (PEG) was added to improve the chain mobility, thus eliminated the variation of the transport activation energy Δ E* caused by tBC8. Then the effect of the increment of crystallization temperature range on the increase of Δ F was also taken into consideration. It was concluded that both decreasing the mobility of chain segments and increasing the crystallization temperature range caused an increase of Δ E for PLLA/tBC8.

The Effect of Thermal History on Porcelain Expansion Behavior

1989 ◽  
Vol 68 (9) ◽  
pp. 1313-1315 ◽  
Author(s):  
C.W. Fairhurst ◽  
D.T. Hashinger ◽  
S.W. Twiggs
Keyword(s):  
Thermal Expansion ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Heating Rate ◽  
Room Temperature ◽  
Heating Rates ◽  
Thermal Expansion Data ◽  
Temperature Range ◽  
Expansion Behavior

Porcelain-fused-to-metal restorations are fired several hundred degrees above the glass-transition temperature and cooled rapidly through the glass-transition temperature range. Thermal expansion data from room temperature to above the glass-transition temperature range are important for the thermal expansion of the porcelain to be matched to the alloy. The effect of heating rate during measurement of thermal expansion was determined for NBS SRM 710 glass and four commercial opaque and body porcelain products. Thermal expansion data were obtained at heating rates of from 3 to 30°C/min after the porcelain was cooled at the same rate. By use of the Moynihan equation (where Tg systematically increases in temperature with an increase in cooling/heating rate), the glass-transition temperatures (Tg) derived from these data were shown to be related to the heating rate.

scholarly journals On the Combined Effect of Both the Reinforcement and a Waste Based Interfacial Modifier on the Matrix Glass Transition in iPP/a-PP-pPBMA/Mica Composites

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2606
Author(s):  
Jesús-María García-Martínez ◽  
Emilia P. Collar
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Atactic Polypropylene ◽  
Complex Character ◽  
The Matrix ◽  
Maleamic Acid ◽  
Interfacial Modifier ◽  
Key Parameter

This work deals with the changes of the glass transition temperature (Tg) of the polymer in polypropylene/mica composites due to the combined and synergistic effect of the reinforcement and the interfacial modifier. In our case, we studied the effect on Tg of platy mica and an interfacial modifier with p-phenylen-bis-maleamic acid (pPBMA) grafted groups onto atactic polypropylene (aPP-pPBMA). This one contains 5.0 × 10−4 g·mol−1 (15% w/w) grafted pPBMA and was previously obtained by the author’s labs by using industrial polymerization wastes (aPP). The objective of the article must be perceived as two-fold. On one hand, the determination of the changes in the glass transition temperature of the isotactic polypropylene phase (iPP) due to both the reinforcement and the agent as determined form the damp factor in DMA analysis. On the other hand, forecasting the variation of this parameter (Tg) as a function of both the interfacial agent and reinforcement content. For such purposes, and by assuming the complex character of the iPP/aPP-pPBMA/Mica system, wherein interaction between the components will define the final behaviour, a Box–Wilson experimental design considering the amount of mica particles and of interface agent as the independent variables, and the Tg as the dependent one, has been used. By taking in mind that the glass transition is a design threshold for the ultimate properties of parts based in this type of organic–inorganic hybrid materials, the final purpose of the work is the prediction and interpretation of the effect of both variables on this key parameter.

INFLUENCE OF MULTIPLE CURING ON MECHANICAL PROPERTIES OF EPOXY MATRIX AND ITS ADHESION TO FIBERS

2021 ◽  
pp. 12-19
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Mechanical Behavior ◽  
Adhesive Strength ◽  
Epoxy Matrix ◽  
Steel Wire ◽  
Curing Temperature ◽  
The Matrix

Adhesive strength of «epoxy binder-steel wire» joints and the mechanical behavior of the binder during multiple repeated curing have been investigated. It is shown that when the curing temperature is considerably higher than the glass transition temperature of the binder, the adhesive strength decreases monotonically with an increase in the number of curing cycles. In this case the mechanical properties of the matrix also decrease. Possible mechanisms of the observed changes are discussed.

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