Orientation temperature

The double-bubble process may be used to produce biaxiaHy oriented film, primarily polypropylene. In this process the first bubble formation is similar to the conventional blown film, except that the bubble is not coUapsed. Rather it is reheated to the orientation temperature and blown and drawn further in a second stage. It is then coUapsed, sUt, and wound. This process is generally limited to a final film thickness of less than 24 p.m. 

The stress—relaxation process is governed by a number of different molecular motions. To resolve them, the thermally stimulated creep (TSCr) method was developed, which consists of the following steps. (/) The specimen is subjected to a given stress at a temperature T for a time /, both chosen to allow complete orientation of the mobile units that one wishes to consider. (2) The temperature is then lowered to Tq T, where any molecular motion is completely hindered then the stress is removed. (3) The specimen is subsequendy heated at a controlled rate. The mobile units reorient according to the available relaxation modes. The strain, its time derivative, and the temperature are recorded versus time. By mnning a series of experiments at different orientation temperatures and plotting the time derivative of the strain rate observed on heating versus the temperature, various relaxational processes are revealed as peaks (243). 

On the other hand, some limitations are present in the proposed formalism. For instance, all the solute polarization is assumed to be electronic in nature. Orientational (temperature dependent) effects are not introduced in the present formulation of solvation effects. However, this limitation allowed us to adopt a simple linear response model for the representation of the induced electronic polarization through the polarization of an electron... 

Fig. 23a, b. ENDOR with circularly polarized rf fields (CP-ENDOR). Single crystal ENDOR spectra of Cu(bipyam)2 (C104)2 diluted into Zn(bipyam)2(C104)2 arbitrary orientation, temperature 20 K. a) Conventional ENDOR spectrum (linearly polarized rf field), b) CP-ENDOR spectrum applied rf field right hand rotating. The spectrum is dominated by the eight nitrogen transitions with msAN > 0. (From Ref. 104)... 

The first of the four characteristic currents to J4 has a prominent position. It indicates the crossover from a charge supply limited reaction to a kmetically and mass transfer limited reaction. This crossover is accompanied by pronounced changes in charge state, chemical dissolution reaction, dissolution valence, pore formation and anodic oxide formation. Therefore its dependence on other parameters, such as crystal orientation, temperature or H F concentration deserves further investigation. In the literature Jt is usually termed /crl JPS or JPSL. In the following the symbol JPS will be used. 

Systematic studies of growth rates on experimental parameters, including seed orientation, temperature, (OH) , pressure (or % fill) and temperature difference between dissolving and growth zone have been conducted.(19) The growth was described by a simple rate equation ... 

Method Nitrogen Orientation Temperature Dominant Remarks Ref... 

With orientation, the thickness is reduced and the surface area enlarged. If film is longitudinally stretched, its thickness and width are reduced in the same ratio. If lateral/transverse contraction is prevented, stretching reduces the thickness only. Orientation temperature is normally 60 to... 

The optimum stretching heat for amorphous plastics (PVC, etc.) is usually just above its glass transition temperature (Tg Chapter 1). Generally the orientation temperature is 60 to 75% between the Tg and Tm (melt temperature). For crystalline plastics (PE, PET, etc.) generally it is below the Tg. Stretching can take place in-line or off-line with or without tenter frames using the appropriate temperature-pull rates as the plastic travels first through a series of heated rolls. For unidirectional orientation just the rolls are used. 

Lowering the Km value of a fuel-oxidizing enzyme is one of the many challenges faced when utilizing natural wild-type enzymes for EFC applications. Other issues, depending on the intended application, include enzyme immobilization and orientation, temperature and pH stability, salt inhibition, and substrate specificity. 

The conditions of carbonization have impact on properties of carbon fibers and their price. The least expensive carbon fibers manufactured Ifom PAN are produced by rapid heating under tension from the initial orientation temperature of 300°C to 1000°C. This process produces low modulus fibers. High strength fibers... 

Oriented films are usually coated with a heat sealant which seals at a temperature below the orientation temperature, otherwise the film will shrink in the heat seal zone, crystallise and possibly become distorted (cockle) and brittle. Oriented films can be heat set by special treatments. 

In the case of both EVAL EP-E105 and SOARNOL D resins, attempts to uniaxially orient to 2.5X were unsuccessful, as the films split and cracked upon drawing. Reducing the stretch rate and increasing the orientation temperature yielded no significant effect. As such, biaxial orientation of these two EVOH films was not attempted. 

For successful orientation, the preform must be brought to a temperature within its orientation temperature range, below its crystalline melting point but above its Tg. For PET this temperature range is 88 to 116°C, forPVC 99 to 116°C, and forPP 104 to 127°C. The temperature and amount of stretching affect the degree of orientation obtained. The cuial ratio is the ratio of the length of the stretched part... 

The preferred orientation temperature for 3GN and 3GN-rich copolymers and blends is 90-135°C. The preferred orientation temperature for PET is 90-115°C, thus allowing 3GN to be biaxially oriented under optimum thermal stretching conditions for PET. 

On the other hand, PEN has a significantly higher glass transition temperature of 113-125°C for unstretched films, and 140°C for fully oriented films and requires higher orientation temperatures, of about 120-150°C. 

PLASTIC MELT TEMPERATURE STRETCH ORIENTATION TEMPERATURE MAXIMUM STRETCH RATIO... 

In this chapter, the fracture of WPCs as particle-filled polymer composites was elaborated. The characterization of particulate polymer composites fracture behavior and the influencing factors such as particle size as well as orientation, temperature, and loading were discussed. The fracture observation using special setup was described and the diverse numerical methods to analyze the fracture of such composites were reviewed. Finally the finite element simulation of the fracture for WPG specimen with real geometrical model was conducted and the agreement of results compared to the experimental ones was demonstrated. 

There are controversies regarding the slip systems in MoSi2. Mitchel et al. [38] did not find 1/2 (331) dislocations in deformed single crystals and they stated that the presence of such dislocations are either unstable or they occur under special conditions of orientation, temperature and stress state. 

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