Copolyimides containing internal acetylene units as a high-performance polyimide molecular composite

1995 ◽  
Vol 7 (3) ◽  
pp. 357-369 ◽  
Author(s):  
Tsutomu Takeichi ◽  
Noriko Miyaguchi ◽  
Rikio Yokota
Keyword(s):  
High Performance ◽  
Cold Drawing ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Crosslinking Reaction ◽  
High Modulus ◽  
Polyimide Films ◽  
Dsc Measurements ◽  
Biphenyltetracarboxylic Dianhydride ◽  
Internal Acetylene

Random and block copolyimides made of biphenyltetracarboxylic dianhydride (BPDA) and 3,3'-diaminodiphenylacetylene (intA), p-phenylenediamine (PDA), and 4,4'-oxydianiline (ODA) were prepared. Random copolyimides were prepared by adding BPDA into an N-methylpyrrolidone (NMP) solution of diamine mixtures, followed by thermal imidization. The ratio of PDA and intA or ODA was 7:3. Block copolyimides were prepared by the reaction of amine-terminated BPDA/PDA units and anhydride-terminated BPDA/intA (or ODA) units. The ratio of PDA and intA or ODA was also set at 7:3. For the polyimides containing internal acetylene units, exotherms appeared on DSC measurements starting from 320C, which shows that crosslinking is occurring. Cold-drawing of polyamide acid films gave polyimide films with a higher modulus. High-temperature treatment to induce crossblinking did not lower the high modulus afforded by the cold-drawing. Crosslinking afforded a higher Tr, and a higher modulus at higher temperatures. Laminate processing was performed at 400C with a pressure of 100kgcm"2. The copolyimides containing internal acetylene units gave laminate films whose interfaces are strongly bonded through the crosslinking reaction. It was confirmed that the laminate films maintained the high modulus afforded by crosslinking.

scholarly journals Influence of Rapid Heat Treatment on the Shrinkage and Strength of High-Performance Concrete

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4102
Author(s):  
Jan Stindt ◽  
Patrick Forman ◽  
Peter Mark
Keyword(s):  
Heat Treatment ◽  
High Performance ◽  
High Performance Concrete ◽  
Treatment Time ◽  
Precast Concrete ◽  
Concrete Strength ◽  
Shrinkage Strain ◽  
Temperature Treatment ◽  
Production Flow ◽  
Steel Fibres

Resource-efficient precast concrete elements can be produced using high-performance concrete (HPC). A heat treatment accelerates hardening and thus enables early stripping. To minimise damages to the concrete structure, treatment time and temperature are regulated. This leads to temperature treatment times of more than 24 h, what seems too long for quick serial production (flow production) of HPC. To overcome this shortcoming and to accelerate production speed, the heat treatment is started here immediately after concreting. This in turn influences the shrinkage behaviour and the concrete strength. Therefore, shrinkage is investigated on prisms made from HPC with and without steel fibres, as well as on short beams with reinforcement ratios of 1.8% and 3.1%. Furthermore, the flexural and compressive strengths of the prisms are measured directly after heating and later on after 28 d. The specimens are heat-treated between 1 and 24 h at 80 °C and a relative humidity of 60%. Specimens without heating serve for reference. The results show that the shrinkage strain is pronouncedly reduced with increasing temperature duration and rebar ratio. Moreover, the compressive and flexural strength decrease with decreasing temperature duration, whereby the loss of strength can be compensated by adding steel fibres.

An experimental study on the fracture behaviors of marble specimens subjected to high temperature treatment

2020 ◽  
Vol 225 ◽  
pp. 106862 ◽  
Author(s):  
Qingzhen Guo ◽  
Haijian Su ◽  
Jiawei Liu ◽  
Qian Yin ◽  
Hongwen Jing ◽  
...  
Keyword(s):  
Experimental Study ◽  
High Temperature ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Fracture Behaviors

scholarly journals Systemic Infection by Fusarium verticillioides in Maize Plants Grown Under Three Temperature Regimes

Plant Disease ◽  
2008 ◽  
Vol 92 (12) ◽  
pp. 1695-1700 ◽  
Author(s):  
A. Murillo-Williams ◽  
G. P. Munkvold
Keyword(s):  
High Temperature ◽  
Environmental Factors ◽  
Fusarium Verticillioides ◽  
Systemic Infection ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Kernel Infection ◽  
Temperature Regimes ◽  
Maize Plants ◽  
Systemic Development

Fusarium verticillioides causes seedling decay, stalk rot, ear rot, and mycotoxin contamination (primarily fumonisins) in maize. Systemic infection of maize plants by F. verticillioides can lead to kernel infection, but the frequency of this phenomenon has varied widely among experiments. Variation in the incidence of systemic infection has been attributed to environmental factors. In order to better understand the influence of environment, we investigated the effect of temperature on systemic development of F. verticillioides during vegetative and reproductive stages of plant development. Maize seeds were inoculated with a green fluorescent protein-expressing strain of F. verticillioides, and grown in growth chambers under three different temperature regimes. In the vegetative-stage and reproductive-stage experiments, plants were evaluated at tasseling (VT stage), and at physiological maturity (R6 stage), respectively. Independently of the temperature treatment, F. verticillioides was reisolated from nearly 100% of belowground plant tissues. Frequency of reisolation of the inoculated strain declined acropetally in aboveground internodes at all temperature regimes. At VT, the high-temperature treatment had the highest systemic development of F. verticillioides in aboveground tissues. At R6, incidence of systemic infection was greater at both the high- and low-temperature regimes than at the average-temperature regime. F. verticillioides was isolated from higher internodes in plants at R6, compared to stage VT. The seed-inoculated strain was recovered from kernels of mature plants, although incidence of kernel infection did not differ significantly among treatments. During the vegetative growth stages, temperature had a significant effect on systemic development of F. verticillioides in stalks. At R6, the fungus reached higher internodes in the high-temperature treatment, but temperature did not have an effect on the incidence of kernels (either symptomatic or asymptomatic) or ear peduncles infected with the inoculated strain. These results support the role of high temperatures in promoting systemic infection of maize by F. verticillioides, but plant-to-seed transmission may be limited by other environmental factors that interact with temperature during the reproductive stages.

Properties of maraging steels after high-temperature treatment

1981 ◽  
Vol 23 (4) ◽  
pp. 265-267
Author(s):  
O. V. Abramov ◽  
A. I. Il'in ◽  
V. M. Kardonskii
Keyword(s):  
High Temperature ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Maraging Steels
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