CN107063889A - Creep stretching device and its experimental method associated with a kind of scattering of and X-ray - Google Patents

Abstract

The invention provides a creep stretching device combined with X-ray scattering and an experimental method thereof. The device adopts the synchronous drive of Yaskawa servo motor as the power source, and at the same time uses the torque limiter to keep the output torque constant to achieve creep stretching. The device is equipped with a torque sensor and an angle sensor to simultaneously measure the rheological information of the creep process and monitor the stability of the device's operating state. The tensile mechanism adopts a hollow detachable separate roller, which reduces the moment of inertia of the mechanism, increases the line speed at the same speed, and can provide a variety of installation modes to meet the testing requirements of different sample strengths and categories. A forced nitrogen flow is used to ensure a uniform temperature in the sample chamber and to prevent thermal degradation of the sample at high temperatures. The invention has the advantages of easy disassembly and installation, is very suitable for use in conjunction with a synchrotron radiation experiment line station, and provides more favorable conditions for characterizing rheological and phase transition behaviors in the crystallization process induced by a flow field.

Description

A Creep Tensile Apparatus Combined with X-ray Scattering and Its Experimental Method

technical field

The invention relates to the technical field of using synchrotron radiation X-ray scattering to study the coupling relationship between polymer structure evolution and different external field parameters, in particular to a creep stretching device combined with X-ray scattering and an experimental method thereof.

Background technique

The study of flow field-induced crystallization of polymer materials has important guiding significance for the processing of polymer materials. Under industrial production and material service conditions, different external field parameters, including strain, strain rate and stress, will affect the final structure and performance of processed products. Based on these factors, it is of great significance to study the mechanism of different external field parameters on the structure evolution of flow field induced crystallization. The common basic idea of this research is to apply a flow field to the material under set temperature, pressure and other conditions, and use different optical characterization methods to analyze the structure and performance characteristics of different scales. In the stretching process, the strain rate is generally controlled to be constant, and different strains are stretched. Due to the unique long-chain structure of polymer materials, most of the research pays more attention to the relaxation mechanical behavior and structure of different micro-scale structures. evolution. However, in many studies, especially those focusing on phase transitions under non-equilibrium conditions, stress actually plays a larger role. Therefore, the creep tension that keeps the tensile stress constant is of great significance for this study.

At the same time, for the study of the structural transformation in the stretching process, the most suitable methods are various in-situ optical detection methods. In particular, ultrafast X-ray scattering is sensitive to various stable and metastable ordered structures in polymer crystalline materials, and can be used to study the structure type, content, morphology, and structural transformation rate and kinetics of ultrafast structural transitions. Commonly used X-ray scattering methods are mainly small-angle and wide-angle X-ray scattering. By adjusting the distance from the sample to the detection and combining the information scale of the material structure, the structure of different spatial scales of the material can be tracked respectively.

In order to conduct in-situ research on the relationship between different external field parameters and structural transformation during the stretching process of polymer materials, the experimental device must meet the following conditions: 1. The stress, strain rate and strain can be controlled separately and the switching of different control modes can be realized. 2. According to the characteristics of different detection materials, the coupling of linear velocity and stress is adjusted under the condition of constant power source power. 3. Portable and easy to carry, the installation size is small, and it is convenient to be used in conjunction with the synchrotron radiation source. 4. There is a light hole for scattered light to pass through, and at the same time, it must ensure that the temperature of the sample is controllable.

Contents of the invention

The object of the present invention is to provide a creep stretching device used in combination with X-ray scattering and its experimental method. The stretching device has the characteristics of easy disassembly and installation, and is convenient to be used in conjunction with synchrotron radiation X-ray in-situ experiment technology; it can control the strain, strain rate and stress separately; the stretching method is uniaxial roller stretching, which can be used in Guaranteed constant stretching speed and strain rate under the same stretching mode; accurate sample temperature control; large range of stress and strain rate controllable, and can be conveniently adjusted and replaced without disassembling the device; with multi-channel real-time data acquisition Features. Morphological and structural information of polymer materials such as crystallinity, orientation degree and rheological information (stress, strain change) can be obtained, and the relationship between external field parameters and structural evolution can be obtained.

The technical solution adopted in the present invention is: a creep stretching device combined with X-ray scattering, including a high-precision servo motor, a motion controller, a constant force output control, a torque sensor, an angle sensor and a hollow-separated roller clamp , the sample is a polymer film sample, where:

The high-precision servo motor is stretched through the control of the motion controller, and the high-precision servo motor and constant force output control are used to control and switch the operating mode. At the same time, the hollow separated roller clamp is used to increase the stretching speed at the same motor speed. Increase the strain rate. During the stretching process, the torque sensor and angle sensor track the change of stress and strain to characterize the rheological behavior. The stretching temperature is precisely controlled by a dual-channel temperature controller. Two thermal resistors are set in the sample heating chamber to detect The temperature information is fed back to the temperature controller, and the temperature controller automatically adjusts the working state to achieve the purpose of precise temperature control; the introduction of nitrogen can ensure the uniform temperature of the film.

Among them, the device can realize three different operating modes, namely:

①The high-precision servo motor runs continuously, and the constant force output control is used for torque control to realize creep stretching;

②The constant force output control is locked, and the strain and strain rate controllable stretching is performed by using a high-precision servo motor;

③Creep stretching is performed first, and then the high-precision servo motor is positioned at a specific strain, and the constant force output control is locked in reverse, and the evolution process of the creep-induced microstructure in the relaxation stage is observed.

Among them, the coupling control of constant force output control and high-precision servo motor can separately control the stress and strain in the stretching process; at the same time, using X-ray ultra-high time-resolved in-situ characterization technology, the stretching/creep process The structural information under the flow field is tracked to study its phase transition theory and scientific issues related to actual production and processing.

The present invention also provides a creep stretching experiment method combined with X-ray scattering, using the above-mentioned creep stretching device, combined with synchrotron radiation wide-angle X-ray scattering and small-angle X-ray scattering experimental techniques, to study flow in situ The phase transition characteristics of field-induced polymer crystallization and the action mechanism of different external field parameters.

The main experimental steps when the device is used in conjunction with X-ray experimental technology are:

Step (1), connect the motor driver with the high-precision servo motor and the motion controller, connect the sensor with the acquisition system, use the temperature controller to control the temperature of the heating rod, and then turn on the power;

Step (2), setting constant force output control parameters,

Step (3), clamping the polymer film sample;

Step (4), setting the stretching temperature of the polymer film sample, and turning on the X-ray light source when the polymer film sample reaches the set temperature;

Step (5), control the high-precision servo motor to start continuous rotation, and perform stretching in the set stretching mode;

In step (6), during the stretching process, the tensile force, the strain change and the structural evolution of the polymer film sample after stretching are simultaneously recorded. By implementing different stretching rates, stretching ratios or stretching stresses on different polymer samples, systematically study the influence of molecular parameters and external field parameters on the crystallization structure and dynamics, and couple these data to obtain the polymer melt under the flow field The relationship between phase transition behavior and rheological behavior.

Among them, the device can realize precise temperature control of thin film samples, and can achieve surface temperature uniformity of polymer samples through nitrogen flow.

Among them, while controlling the rotation of the motor, the changes in the internal stress and strain of the sample can be collected, and the influence of different samples and different external field parameters on the structural transformation process during the flow field-induced crystallization process can be obtained.

Among them, the device can be used in conjunction with synchrotron radiation X-ray experimental technology to track the evolution of thin film structures in situ.

Compared with the commonly used stretching device, the present invention mainly has the following innovations:

1. The device of the present invention is easy to disassemble and install, and is convenient to be used in conjunction with the synchrotron radiation X-ray experimental technique.

2. The stretching rate, stretching ratio and stretching force of the present invention are continuously adjustable, and the control is precise;

3. The present invention switches between different stretching modes through the coupling control of high-precision servo motors and constant force output controls, and studies the mechanism of action of different types of external field parameters.

4. The stretching method of the present invention is uniaxial hollow roller stretching, which increases the linear speed and reduces the moment of inertia at the same motor speed; the separate fixture is easy to replace and can be adjusted according to different samples;

5. The present invention has a large range of controllable tension and tension speed, and has the characteristics of multi-channel real-time data acquisition and the like.

6. The present invention can obtain the morphological structure information of polymer materials such as crystallinity, orientation degree and rheological information (strain, stress change), and obtain the relationship between different external field parameters and microstructure evolution.

7. The application prospect of the present invention: 1) Combined with synchrotron radiation X-ray scattering experiment technology, systematically study the mechanism of action of different processing parameters to regulate product performance during the processing of polymer materials; 2) Study the microstructure in flow field induced crystallization The corresponding relationship between the transformation process and the external action parameters explains the phase transition theory in non-equilibrium physics.

In summary, the present invention can study the structural evolution behavior of different polymer materials under different stretching temperatures and different types of stretching modes, and study the mechanism of different types of external field parameters on the structural evolution during flow field induced crystallization. The relationship between the external field parameters and the phase transition structure and properties can be obtained by coupling the crystallinity, crystal form, orientation degree of the thin film sample obtained by X-ray scattering with the tensile mechanical data. It is used in the laboratory to simulate the actual film stretching processing conditions and reveal the scientific problems of film industrial processing.

Description of drawings

Fig. 1 is a schematic structural view of the creep stretching device used in conjunction with X-ray scattering according to the present invention, wherein: 1 is a high-precision servo motor, 2 is a motion controller, 3 is a constant force output control, 4 is a torque sensor, 5 is an angle sensor, 6 is a hollow separation roller fixture, and 7 is a polymer film sample;

Fig. 2 is the schematic diagram of the hollow split roller clamp of the present invention;

Fig. 3 is the rheological data obtained in the present invention, including strain and stress information;

Fig. 4 is the strain, the stress curve in the mode 3 experiment;

Figure 5 is a wide-angle X-ray scattering diagram of stretch-induced natural rubber crystallization at different strain rates;

Figure 6 is the quantitative data of the structure evolution during the creep-relaxation process.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and examples.

Referring to accompanying drawing 1, a creep stretching device used in conjunction with X-ray scattering, the creep stretching device includes a high-precision servo motor 1, a motion controller 2, a constant force output control 3, a torque sensor 4, and an angle sensor 5 and a hollow-separated roller clamp 6, wherein the sample is a polymer film sample 7, and the high-precision servo motor 1 is controlled by a motion controller 2 for stretching. Utilize the high-precision servo motor 1 and the constant force output control 3 to control and switch the operation mode. At the same time, the hollow split roller clamp 6 is used to increase the stretching speed at the same motor speed so as to increase the strain rate. During the stretching process, the torque sensor 4 and the angle sensor 5 track the changes of stress and strain to characterize the rheological behavior. The stretching temperature is precisely controlled by a dual-channel temperature controller. Two thermal resistors are set in the sample heating chamber, and the detected temperature information is fed back to the temperature controller. The temperature controller automatically adjusts the working state to achieve the purpose of precise temperature control; the introduction of nitrogen It can ensure the uniformity of film temperature.

The creep stretching device can realize three different operating modes, namely:

1. The high-precision servo motor 1 runs continuously, and the constant force output control 3 is used for torque control to realize creep stretching;

2. The constant force output control 3 is locked, and the high-precision servo motor 1 is used to perform constant strain rate stretching with controllable strain and strain rate;

3. Firstly, creep stretching is carried out, and then the high-precision servo motor 1 is positioned at a specific strain, and the constant force output control 3 is reversely locked to observe the evolution process of the creep-induced microstructure in the relaxation stage.

Among them, under the condition of high-speed stretching, by assembling different types of hollow rollers and fixtures, as shown in Figure 2, the maximum rotational speed and maximum stress of the system can be coupled and controlled to meet the test requirements for samples with different performances. Use motor power. At the same time, it can collect the changes of stress and strain during the stretching process, and study the phase transition characteristics of flow field-induced crystallization and the physical mechanism of external field parameters. The roller is designed to be detachable, and the two parts are respectively connected to the transmission shaft. During the experiment, the device can be replaced according to different experimental requirements without disassembling the device. According to the design of the device space, the distance between the rollers needs to be 9 mm to ensure the passage of X-rays, so the controllable range of the diameter of the rollers is 8 to 26 mm, the maximum speed of the motor is 3000 rpm, and the maximum torque value of the constant force output control 0.5 Nm, sample thickness 0.5 mm, width 5 mm. According to the above parameters, by the formula:

Linear speed = rotational speed x roller circumference x 2

It can be calculated that the device can achieve a maximum speed of 8.16 m/s and a maximum stress of 25 MPa.

The device uses a dual-channel temperature controller to control the working state of the heating rod to control the temperature of the sample, and the temperature probe has a feedback function. By adjusting the PID parameters to precisely control the cavity temperature and heating and cooling rate.

Experimental example:

Wide-angle X-ray scattering in situ investigation of the effect of ultrafast stretching rates on stretch-induced crystallization of natural rubber.

Purpose:

Natural rubber can crystallize under stretching conditions. In stretch-induced natural rubber crystallization, it is generally believed that the crystallization behavior of rubber has a clear correspondence with strain, without considering the effects of rubber relaxation and crystallization kinetics. Moreover, because the traditional stretching device can only control constant strain rate stretching and the stretching speed is limited, it cannot reflect the relationship between natural rubber crystallization kinetics and different flow field parameters well. In this experiment, using a creep tension device, combined with ultrafast X-ray wide-angle and small-angle detection experimental techniques, we were able to observe the multi-scale effects of different external field parameters on the crystallization and crystallization kinetics of natural rubber.

experiment procedure:

The natural rubber raw material is Indonesia No. 1 smoked sheet rubber, which is pressed with a flat vulcanizer after mixing with sulfur. The sample size is 0.4*5*45 mm. X-ray wide-angle scattering tracks the evolution of sample morphology before and after stretching, and torque and angle sensors record stress and strain changes during stretching, respectively. Combining the tensile force and sample morphology, the phase transition and rheological information of natural rubber crystallization induced by different tensile conditions can be obtained. In this example, the aforementioned operation modes 2 and 3 are used to study the evolution of stress-induced crystallization and structural relaxation under creep conditions.

Experimental results:

Fig. 3 is the rheological data obtained under different creep stresses obtained in the present invention, that is, the variation of strain in the creep process with time; under high stress creep, it is observed that the sample strain increases gradually, showing an obvious creep phenomenon; It can be seen from the enlarged picture of Figure b that the sample needs a certain stabilization time to start the creep process. At the lowest experimental value of 3.8 MPa, it can be found that the longest stabilization time is about 0.2 seconds. Compared with the experiment time of tens of seconds, the effect of creep stabilization time can be ignored in the data analysis process.

Figure 4 is the rheological curve for mode 3 operation. Under the stress of 9.6 MPa, the creep is performed for 20 seconds, and then the relaxation process is performed. Typical creep and relaxation curves can be observed in the figure, that is, the stress remains constant during the creep process and the strain increases; the strain remains constant and the stress decreases during the relaxation process.

Figure 5 is the WAXS and SAXS two-dimensional diagrams of the initial creep process. It can be seen from the figure that a weak orientation signal begins to appear in SAXS at 0.06 seconds, and the crystal signal can only be seen in WAXS at 0.18 seconds. The crystal signal is highly oriented, which indicates the presence of an amorphous pre-ordered structure from 0.06 s to 0.18 s. After 6 seconds, the shape of the signal no longer changes significantly, only the intensity changes.

Figure 6 is the peak intensity and crystallinity curves of the creep-relaxation process. From 20 seconds onwards, that is, the relaxation process, the crystal facet strength and crystallinity begin to decrease. This shows that under the condition of constant strain, the decrease of stress will lead to the decrease of crystallinity.

Experimental results:

Using the creep tension device combined with X-ray scattering, the experiment successfully observed the structural information and crystallization kinetics of natural rubber under different conditions. From rheological data and X-ray structure evolution, the following two conclusions can be drawn:

1) During the crystallization process of natural rubber, there is an amorphous pre-ordered structure.

2) The stress itself can affect the crystallization behavior. A drop in stress during relaxation leads to a drop in crystallinity.

The parts not described in detail in the present invention belong to the well-known technology in the art.

Although the illustrative specific embodiments of the present invention have been described above, so that those skilled in the art can understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, As long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are included in the protection list.

Claims (9)

1. creep stretching device associated with a kind of scattering of and X-ray, it is characterised in that：Including high-precision servo motor (1), motion Controller (2), constant force output control (3), torque sensor (4), angular transducer (5) and hollow separating roller collet chuck tool (6), Sample is macromolecule membrane sample (7), wherein：

High-precision servo motor (1) is stretched by motion controller (2) control, utilizes high-precision servo motor (1) and perseverance Power output control (3) control and running mode switching, meanwhile, have (6) using hollow separating roller collet chuck, turn in identical motor Speed is lower to be improved draw speed to improve in strain rate, drawing process, torque sensor (4) and angular transducer (5) tracking The change of stress and strain, characterizes rheological behavior, and draft temperature is accurately controlled by binary channels temperature controller, sample heating chamber Two thermal resistances are set, and the temperature information of detection feeds back to temperature controller, temperature controller automatically adjust working condition with up to To the purpose of accurate temperature controlling；Being passed through for nitrogen ensure that the uniform of film temperature.

2. creep stretching device associated with a kind of and X-ray scattering as claimed in claim 1, it is characterised in that：The device can To realize three kinds of different operational modes, it is respectively：

1. high-precision servo motor (1) is continuously run, and exporting control (3) using constant force carries out moment of torsion control, realizes that creep is stretched；

2. constant force output control (3) is locked, and strain and strain rate controlled stretching are carried out using high-precision servo motor (1)；

3. creep stretching is carried out first, is positioned afterwards by high-precision servo motor (1) in specific strain, constant force output control (3) It is reversely locked, the evolutionary process of the generation microstructure that observation creep is induced in relaxation stage.

3. creep stretching device associated with a kind of and X-ray scattering as claimed in claim 1, it is characterised in that：Constant force is exported The coupling control of control (3) and high-precision servo motor (1), can respectively be controlled to the stress and strain in drawing process System；Meanwhile, using X-ray ultrahigh time resolution in-situ characterization technology, the structural information under stretching/creep process field of flow is entered Line trace, studies its phase transformation theory and the problem in science related to actual production processing.

4. creep stretching experiment method associated with a kind of scattering of and X-ray, using the creep stretching device described in claim 1, It is combined with synchrotron radiation WAXS wide angle X ray scattering and small angle X ray scattering experimental technique, the induction of on-spot study different type field of flow The relation of structure evolution behavior and processing characteristics in crystallization process；It is characterized in that：When the device is combined with X-ray experimental technique Main experimental procedure is：

Step (1), motor driver is connected with high-precision servo motor (1) and motion controller (2) respectively, sensor is with adopting Collecting system is connected, temperature in use controller control heating rod temperature, is then turned on power supply；

Step (2), setting constant force output control (3) parameter,

Step (3), clamping macromolecule membrane sample (7)；

Step (4), setting macromolecule membrane sample (7) draft temperature, when macromolecule membrane sample (7) reaches design temperature, Open X-ray source；

Step (5), control high-precision servo motor (1) start continuous rotation, are stretched under the stretch mode of setting；

Macromolecule membrane sample (7) structure evolution after recording stress, strain variation in step (6), drawing process simultaneously and stretching, By implementing different stretch speed, draw ratio or tensile stress, system research molecular parameter and outfield to different macromolecule samples Parameter is on crystalline texture and dynamic (dynamical) influence, and these data are coupled together the phase transformation row for obtaining macromolecule melt under flow field For the relation with rheological behaviour.

5. creep stretching experiment method associated with a kind of and X-ray scattering as claimed in claim 4, it is characterised in that：Utilize The coupling of high-precision servo motor and constant force output control is installed and controlled, and realizes the assay format of three kinds of different stretch patterns, Different rheological parameters and structural parameters in Study on Crystallization are induced field of flow to be tracked.

6. creep stretching experiment method associated with a kind of and X-ray scattering as claimed in claim 4, it is characterised in that：Pass through Using dismountable separate type hollow roller drum fixture, reduce rotary inertia, improve draw speed；It is easy to disassemble, in sample cavity It can be installed and be changed, different test stresses, strain rate scope achieved by adjusting apparatus meet different materials Testing requirement, and can be coupled with the strength of materials and phase change conditions.

7. creep stretching experiment method associated with a kind of and X-ray scattering as claimed in claim 4, it is characterised in that：Can be with The accurate temperature controlling to film sample is realized, and film sample surface temperature uniformity can be realized.

8. creep stretching experiment method associated with a kind of and X-ray scattering as claimed in claim 4, it is characterised in that：Can be with Recording materials internal strain and stress information during high-speed stretch, become while characterizing structural material internal structure using x-ray Change, obtain the multi-Scale Data of material phase transformation.

9. creep stretching experiment method associated with a kind of and X-ray scattering as claimed in claim 4, it is characterised in that：Device It can be combined with synchrotron radiation X-ray experimental technique, in-situ tracking material structure develops.