Scanning Rheometer

Abstract

The present disclosure relates to a filament stretching rheometer for measuring rheological and/or mechanical properties of a sample, comprising: a pair of opposed surfaces for holding the sample therebetween; an actuator configured to provide a controlled axial displacement of at least one of said opposed surfaces; and a sample scanning unit for measuring a diameter of said sample, the sample scanning unit configured for measuring said sample diameter at an axial position controlled independently of the dis placement of the opposed surfaces, the sample scanning unit configured for being positioned at a starting point before said controlled axial displacement, wherein the starting point is selected from a position where a minimum diameter of the said sample is determined by said sample scanning unit.

Claims

1. A filament stretching rheometer for measuring rheological and/or mechanical properties of a sample, comprising: a pair of opposed surfaces for holding the sample therebetween; an actuator configured to provide a controlled axial displacement of at least one of said opposed surfaces; and a sample scanning unit for measuring a diameter of said sample, wherein the sample scanning unit is configured to select a starting point which corresponds to the axial position of the minimum diameter of the sample.

2. The filament stretching rheometer according to claim 1, further comprising a feedback controller configured to control the actuator based on input from the sample scanning unit.

3. The filament stretching rheometer according to any of the preceding claims, wherein the sample scanning unit is configured for measuring said sample diameter at an axial position which is controlled independently of the displacement of the opposed surfaces.

4. The filament stretching rheometer according to any of the preceding claims, wherein said sample scanning unit is configured for obtaining a diameter profile of the sample.

5. The filament stretching rheometer according to any of the preceding claims, wherein said sample scanning unit is configured to determine the minimum diameter of the sample before, during, and/or after said controlled axial surface displacement.

6. The filament stretching rheometer according to any of the preceding claims, wherein said sample scanning unit is configured for moving independently of the axial displacement of the opposed surface(s).

7. The filament stretching rheometer according to any of the preceding claims, wherein said scanning unit is configured for axial movement parallel to the displacement of said opposed surface(s).

8. The filament stretching rheometer according to any of the preceding claims, wherein said sample scanning unit comprises one or more movable/rotatable mirrors.

9. The filament stretching rheometer according to any of the preceding claims, further comprising force and/or stress determining means, such as a force and/or pressure transducer, for measuring the force and/or pressure exerted on at least one of said opposed surfaces.

10. The filament stretching rheometer according to claim 8, wherein said feedback controller is configured to control the actuator based on said force and/or pressure.

11. The filament stretching rheometer according to any of the preceding claims 2 to 10, wherein said feedback controller is configured to provide a displacement of the opposed surfaces such that the minimum diameter of the sample increases or decreases exponentially during test.

12. The filament stretching rheometer according to any of the preceding claims 2 to 11, wherein said feedback controller is configured to provide a displacement of the opposed surfaces such that force per unit area exerted on the sample is constant during test.

13. The filament stretching rheometer according to any of the preceding claims, further comprising an environmentally controlled chamber surrounding the sample.

14. The filament stretching rheometer according to any of the preceding claims, wherein the time for reducing the temperature, T, of said gas inside the chamber from 150 C.<T<300 C. to 25 C.<T150 C. is less than 5 seconds, less than 4 seconds, less than 3 second, less than 2 seconds or less than 1 second.

15. The filament stretching rheometer according to any of the preceding claims, wherein said environmentally controlled chamber is configured to be removed from said sample in order to expose said sample to ambient conditions.

16. The filament stretching rheometer according to any of the preceding claims, further comprising a data processor configured to determine rheological and/or mechanical properties of a sample based on measurements of sample diameter and force, pressure and/or stress exerted on the sample during test.

17. An environmentally controlled chamber for a filament stretching rheometer, comprising an insolating surface configured to be placed around a sample, and such that said surface can be removed from said sample by displacing said surface, thereby exposing said sample to ambient conditions.

18. The environmentally controlled chamber according to claim 17, wherein said filament stretching rheometer is a rheometer according to claims 1-16.

19. The environmentally controlled chamber according to claim 17-18, wherein said chamber is configured for controlling ambient temperature, ambient gas composition, flow rate of ambient gas, ambient humidity and/or ambient pressure of gas inside the chamber.

20. The environmentally controlled chamber according to claim 17-19, wherein said chamber is configured for reducing the temperature, T, of said gas inside the chamber from 150 C.<T<300 C. to 25 C.<T150 C.

21. The environmentally controlled chamber according to claim 17-20, wherein the time for reducing the temperature, T, of said gas inside the chamber from 150 C.<T<300 C. to 25 C.<T150 C. is less than 5 seconds, less than 4 seconds, less than 3 second, less than 2 seconds or less than 1 second.

22. A method for controlling a filament stretching rheometer, comprising the steps of: stretching a sample between two opposed surfaces such that said sample is fixed in an initial state, and said two opposed surfaces are in fixed positions; measuring a plurality of diameters of said sample in said initial state in a plurality of positions between said opposed surfaces in said fixed positions with a moving sample scanning unit, thereby moving said sample scanning unit independently of said two opposed surfaces; determining a minimum diameter from said plurality of diameters; and selecting a starting point of said moving sample scanning unit for a measurement from said minimum diameter.

23. The method according to claim 22, wherein said filament stretching rheometer is a rheometer according to claims 1-16.

24. The method according to claims 22-23, further comprising the steps of: positioning said moving sample scanning unit at said starting point; moving said two opposed surfaces towards or away from each other, such that said sample scanning unit moves dependently of said two opposed surfaces from said starting point; and measuring the diameter of said sample during movement of said two opposed surfaces.

Description

DESCRIPTION OF FIGURES

[0027] FIG. 1 shows a schematic illustration of one embodiment of the scanning rheometer according to the present disclosure, from a view as follows: a) side-view, b) opposite side-view, and c) front-view.

[0028] FIG. 2 shows a schematic illustration of one embodiment of the scanning rheometer according to the present disclosure from a front view.

[0029] FIG. 3 shows a schematic illustration of one embodiment of the scanning rheometer according to the present disclosure from a side view.

[0030] FIG. 4 shows a schematic illustration of one embodiment of the scanning rheometer according to the present disclosure from a front view.

[0031] FIG. 5 shows a schematic illustration of one embodiment of the scanning rheometer according to the present disclosure from a side view.

DETAILED DESCRIPTION OF THE INVENTION

[0032] The present disclosure relates to a filament stretching rheometer for measuring rheological and/or mechanical properties of a sample.

[0033] Referring to FIG. 1, there is a motor 101 with a moving plate 102 connected to a light source 104 and a detector 105 via arms 103 and 107 and crossbar connector 106, a second motor 111 with a moving plate 112 connected to a top surface 114 via connector 113, a bottom surface 122 connected to a force/pressure transducer 121, and a housing 132 that surround the top surface 114, bottom surface 122 and sample 10 and controls environmental conditions of sample via controller 131.

[0034] Opposed Surfaces

[0035] The two opposed surfaces, top 114 and bottom 122, create opposed surfaces, for which the sample 10 is suspended. The opposing surfaces may be surfaces on a pair of opposed plates or rods and be constructed of any material. Furthermore, the material comprising the surfaces may be roughened, polished, or chemically coated to promote adhesion of the sample to the surfaces. The shape of the opposing surfaces may be square, circular, rectangular, elliptical, or 3-dimensional structures, e.g. spherical or conical, or any 3-dimensional structures. The size of the opposed surfaces may be a wide range depending upon the application, materials, and the embodiment of the invention.

[0036] The shapes and sizes of the opposing surfaces need not be the same and may be any combination of shape and size. The preferred orientation of the surfaces may be parallel to each other, but need not be, and depending on application, the surfaces may have other orientations. The two surfaces, top 114 and bottom 122, may be interchangeable.

[0037] Sample

[0038] The sample may be melts and solids. Typical samples may be Polystyrene, Polymethylmethacrylate, Polyethylene, Polycarbonate, Polypropylene, Polylsoprene, and/or Polybutylacrylate. All samples may have a glass transition temperature and/or a melting temperature. One purpose of the present disclosure is to measure some properties below the glass transition temperature and/or melting temperature of the samples after it has been stretched.

[0039] The size of the sample depends on how the sample is stretched. Accordingly, the size and shape of the sample suspended between the two surfaces depends on the size, shape, separation, trajectory of separation, and orientation of the two opposed surfaces.

[0040] Sample Scanning Unit

[0041] In one embodiment of the present disclosure, the sample scanning unit is configured for moving independently of the axial displacement of the opposed surface(s). It is because of this configuration, that the sample scanning unit may be able to determine the minimum diameter of the sample before, during, and/or after said controlled axial surface displacement.

[0042] As previously described, the sample scanning unit may be configured to determine the minimum diameter of the sample before, during, and/or after said controlled axial surface displacement. Accordingly, the scanning unit may be configured for operation before, during and/or after the displacement of said opposed surface(s).

[0043] In one embodiment of the present disclosure, the sample scanning unit comprises a laser micrometer. The laser micrometer typically comprises a light emitting unit such as a laser or a light emitting diode (LED) and an imaging unit. The light may be passed through a diffusion unit and a collimator lens before it is irradiated on the sample. The image of a shadow created by the sample may be projected on the imaging unit such as a CCD or CMOS detector, typically via a tele-centric optical system. Based on the received light output from the recording unit, the dimensions of the sample may be determined. One advantage of using a laser micrometer is that it is fast because it may use low-complexity image processing algorithms, such as edge detection, to determine the diameter. An advantage of using a tele-centric optical system is that it may produce images of the same size regardless of shift in image and/or object planes.

[0044] In another embodiment of the present disclosure, the sample scanning unit comprises an imaging unit. In this regard, there may be no need for a light emitting unit, a diffusion unit and/or a collimator lens. Furthermore, there may be no need for a tele-centric optical system, and a non-telecentric lens may thus be used instead. An advantage of using an imaging unit with a non-telecentric lens is its low cost.

[0045] In a preferred embodiment of the present disclosure, the scanning unit is configured for axial movement parallel to the displacement of said opposed surface(s). In this way, the distance is always the same from the scanning unit and to the sample. Hence, in the case when the scanning unit comprises an imaging unit, i.e. without a tele-centric lens, there may be no need to change focus and the imaging unit may thus need no autofocus. Accordingly, the device may be configured for fast determination of the diameter of the sample, and thus for fast determination of the minimum diameter of the sample.

[0046] The scanning unit may however not necessarily need to be configured for axial movement parallel to the displacement of said opposed surface(s). The movement may be at any given angle and even perpendicular to the displacement of said opposed surface(s). In case of a non-telecentric lens being used, a projection error may need to be considered, such that the diameter of the sample may be correctly determined. In case of a tele-centric lens being used, the produced images may be of the same size regardless of the shift in object planes, and therefore there may be no projection errors, implying that a tele-centric lens may be preferred in such configurations.

[0047] In another embodiment of the present invention, the sample scanning unit comprises one or more movable/rotatable mirrors. For example, a rotatable mirror may be placed at a position between the sample and the imaging unit. The rotatable mirror may be configured to rotate such that it scans the sample before, during and/or after said controlled axial surface displacement. The one or more movable/rotatable mirrors may be any type of mirrors, in particular planar mirrors, curved mirrors, and/or reflective materials such as gratings. Furthermore, the one or more movable/rotatable mirrors may be micro mirror systems and arrays thereof, in particular micro-electro-mechanical systems (MEMS). One advantage of using micro mirrors is that they are light weight and may be moved relatively fast in comparison to for example a large mirror or in comparison to translating a scanning unit.

[0048] Feedback Controller

[0049] In one embodiment of the present disclosure, the filament stretching rheometer further comprises force and/or stress determining means, such as a force and/or pressure transducer, for measuring the force and/or pressure exerted on at least one of said opposed surfaces. In this way, a desired pressure and/or force is able to be obtained.

[0050] Accordingly, the feedback controller may be configured to control the actuator based on said force and/or pressure.

[0051] In one embodiment of the present disclosure, the feedback controller is configured to provide a displacement of the opposed surfaces such that the minimum diameter of the sample increases or decreases exponentially during test. In this way, the strain rate may be kept constant.

[0052] In tests, where for example a constant strain rate may not be required, the feedback controller may be configured to provide a displacement of the opposed surfaces such that the minimum diameter of the sample increases or decreases non-exponentially during test.

[0053] In some embodiments of the present disclosure, the feedback controller is configured to provide a displacement of the opposed surfaces such that the force per unit area exerted on the sample is constant during test. In this way, the stress may be kept constant.

[0054] Various parameters of the measurements may be set depending on the desired rheological or mechanical properties that need to be determined. Also combinations and/or series of parameters may be set depending on the desired rheological or mechanical properties that need to be determined. For example, a constant strain may be followed by a constant strain-rate and/or constant stress.

[0055] Motors and Processors

[0056] In one embodiment of the present disclosure, the filament stretching rheometer further comprises separate motors for powering the actuator and the sample scanning unit, respectively. In this way, the actuators and sample scanning unit may be able to move independently of each other.

[0057] In another embodiment of the present disclosure, the filament stretching rheometer further comprises a data processor configured to determine rheological and/or mechanical properties of a sample based on measurements of sample diameter and force, pressure and/or stress exerted on the sample during test.

[0058] Environmentally Controlled Chamber

[0059] In one embodiment of the present disclosure, the filament stretching rheometer further comprises an environmentally controlled chamber surrounding the sample. This may be advantageous in that various tests may be performed for well-defined environments. The environmentally controlled chamber may be controlled by an environmental controller such as a temperature controller with heating and/or cooling elements, humidity controller, pressure controller, and/or inert gas flow rate controller. Regardless of the controller, the controller may be configured for monitoring and adjusting the power in order to reach and maintain a desired environment such as a well-defined temperature, flow rate, humidity and/or pressure.

[0060] In relation to the second aspect of the present invention, relating to an environmentally controlled chamber, specifically to an environmentally controlled chamber for a filament stretching rheometer, wherein the filament stretching rheometer may be a rheometer as described herein.

[0061] Accordingly, the environmentally controlled chamber may be configured for controlling ambient temperature, ambient gas composition, flow rate of ambient gas, ambient humidity and/or ambient pressure of gas inside the chamber.

[0062] In a preferred embodiment of the present disclosure, the environmentally controlled chamber is configured for reducing the temperature, T, of said gas inside the chamber from 150 C.<T<300 C. to 25 C.<T150 C. In such configuration, it may be possible to expose a sample to a temperature above its melting point and/or its glass transition temperature and go below its melting point and/or its glass transition temperature. For example, among the previously described samples, Polystyrene has a glass transition temperature of approximately 100 C., Polymethyl methacrylate has a glass transition temperature of approximately 130 C., Polyethylene has a melting temperature of 110 C., Polycarbonate has a glass transition temperature of approximately 145 C., and Polypropylene has a melting temperature of approximately 165 C.

[0063] In order to perform quenching tests, it is desired that the temperature is able to rapidly go below the glass transition temperature and/or melting temperature of the sample. Accordingly, the time for reducing the temperature, T, of said gas inside the chamber from 150 C.<T<300 C. to 25 C.<T150 C. may be less than 5 seconds, less than 4 seconds, less than 3 second, less than 2 seconds or less than 1 second. The control of the temperature may be facilitated by heaters and coolers. The heaters may consist of induction heating devices, convection heating devices, and/or thermoelectric heating devices. The coolers may comprise thermoelectric cooling devices, refrigerator devices, and/or circulation of cold gas, e.g. air, nitrogen, liquid, and/or oxygen.

[0064] Preferably, the environmentally controlled chamber may be configured to be removed from the sample in order to expose said sample to ambient conditions. Preferably, the chamber may be removed from the sample in less than 5 seconds, less than 4 seconds, less than 3 second, less than 2 seconds or less than 1 second. In this way, it may be possible to rapidly reduce the temperature of the sample.

[0065] Referring to FIG. 2, the housing 132 is the environmentally controlled chamber. In the illustrated example, the environmentally controlled chamber 132 surrounds the top surface, the bottom surface and the sample. A light source 104 and a detector 105 are configured to measure the diameter of the sample through an optical access 141 in the housing 132 (as seen in FIG. 3).

[0066] The optical access 141 is shown in FIG. 3, where the environmentally controlled chamber is shown from the side. From this perspective, the motor 101 and the one arm 103 to move the light source 104 or the detector 105 can be seen. A second motor 111 to move the surface(s) holding the sample is also to be seen. In the illustrated example, the environmentally controlled chamber 132 is closed, such that it surrounds the top surface, the bottom surface and the sample.

[0067] Referring to FIG. 4, the environmentally controlled chamber 132 is removed from the sample in order to expose the sample to ambient conditions. A top surface and 114 and bottom surface 122 are shown together with a stretched sample 10.

[0068] In FIG. 5, the environmentally controlled chamber 132 is shown from the side, where it can be seen that it is removed from the sample in order to expose the sample to ambient conditions.

[0069] Controlling the Rheometer

[0070] According to the third aspect of the present invention, relating to a method for controlling a filament stretching rheometer, the rheometer may be a rheometer as described herein.

[0071] In one embodiment of the present invention, the method further comprising the steps of: positioning said moving sample scanning unit at said starting point, moving said two opposed surfaces towards or away from each other, such that said sample scanning unit moves dependently of said two opposed surfaces from said starting point; and measuring the diameter of said sample during movement of said two opposed surfaces. Dependently being e.g. maintaining a fixed relationship of the axial positions of the sample scanning unit and the two opposed surfaces.

[0072] Further Details of the Invention

[0073] The invention will now be described in further details with reference to the following items: [0074] 1. A filament stretching rheometer for measuring rheological and/or mechanical properties of a sample, comprising: [0075] a pair of opposed surfaces for holding the sample therebetween, [0076] an actuator configured to provide a controlled axial displacement of at least one of said opposed surfaces, and [0077] a sample scanning unit for measuring a diameter of said sample, the sample scanning unit configured for measuring said sample diameter at an axial position controlled independently of the displacement of the opposed surfaces. [0078] 2. The filament stretching rheometer according to item 1, further comprising a feedback controller configured to control the actuator based on input from the sample scanning unit. [0079] 3. The filament stretching rheometer according to any of the preceding items, wherein said sample scanning unit is configured for obtaining a diameter profile of the sample. [0080] 4. The filament stretching rheometer according to any of the preceding items, wherein said sample scanning unit is configured to determine the minimum diameter of the sample before, during, and/or after said controlled axial surface displacement. [0081] 5. The filament stretching rheometer according to any of the preceding items, wherein said sample scanning unit is configured for moving independently of the axial displacement of the opposed surface(s). [0082] 6. The filament stretching rheometer according to any of the preceding items, wherein said scanning unit is configured for axial movement parallel to the displacement of said opposed surface(s). [0083] 7. The filament stretching rheometer according to any of the preceding items, wherein said scanning unit is configured for operation before, during and/or after the displacement of said opposed surface(s). [0084] 8. The filament stretching rheometer according to any of the preceding items, wherein said sample scanning unit comprises a laser micrometer. [0085] 9. The filament stretching rheometer according to any of the preceding items, wherein said sample scanning unit comprises an imaging device. [0086] 10. The filament stretching rheometer according to any of the preceding items, wherein said sample scanning unit comprises one or more movable/rotatable mirrors. [0087] 11. The filament stretching rheometer according to any of the preceding items, further comprising force and/or stress determining means, such as a force and/or pressure transducer, for measuring the force and/or pressure exerted on at least one of said opposed surfaces. [0088] 12. The filament stretching rheometer according to item 11, wherein said feedback controller is configured to control the actuator based on said force and/or pressure. [0089] 13. The filament stretching rheometer according to any of the preceding items 2 to 12, wherein said feedback controller is configured to provide a displacement of the opposed surfaces such that the minimum diameter of the sample increases or decreases exponentially during test. [0090] 14. The filament stretching rheometer according to any of the preceding items 2 to 12, wherein said feedback controller is configured to provide a displacement of the opposed surfaces such that the minimum diameter of the sample increases or decreases non-exponentially during test. [0091] 15. The filament stretching rheometer according to any of the preceding items 2 to 13, wherein said feedback controller is configured to provide a displacement of the opposed surfaces such that force per unit area exerted on the sample is constant during test. [0092] 16. The filament stretching rheometer according to any of the preceding items, further comprising an environmentally controlled chamber surrounding the sample. [0093] 17. The filament stretching rheometer according to any of the preceding items, wherein said environmentally controlled chamber is configured for controlling ambient temperature, ambient gas composition, flow rate of ambient gas, ambient humidity and/or ambient pressure of gas inside the chamber. [0094] 18. The filament stretching rheometer according to any of the preceding items, wherein said environmentally controlled chamber is configured for reducing the temperature, T, of said gas inside the chamber from 150 C.<T<300 C. to 25 C.<T150 C. [0095] 19. The filament stretching rheometer according to any of the preceding items, wherein the time for reducing the temperature, T, of said gas inside the chamber from 150 C.<T<300 C. to 25 C.<T150 C. is less than 5 seconds, less than 4 seconds, less than 3 second, less than 2 seconds or less than 1 second. [0096] 20. The filament stretching rheometer according to any of the preceding items, wherein said environmentally controlled chamber is configured to be removed from said sample in order to expose said sample to ambient conditions. [0097] 21. The filament stretching rheometer according to any of the preceding items, further comprising separate motors for powering the actuator and the sample scanning unit, respectively. [0098] 22. The filament stretching rheometer according to any of the preceding items, further comprising a data processor configured to determine rheological and/or mechanical properties of a sample based on measurements of sample diameter and force, pressure and/or stress exerted on the sample during test.