Effect of poly(methyl methacrylate) molecular weight on its ternary polymer blends micro– structure using x–ray computed tomography - Hoa T. Nguyen

Journal of Science and Technology 55 (1B) (2017) 169–173 EFFECT OF POLY(METHYL METHACRYLATE) MOLECULAR WEIGHT ON ITS TERNARY POLYMER BLENDS MICRO– STRUCTURE USING X–RAY COMPUTED TOMOGRAPHY Hoa T. Nguyen1, 2, *, Yukihiro Nishikawa3 1Faculty of Materials Technology, HCMUT–VNUHCM 268 Ly Thuong Kiet Street, Ward 14, District 10, Ho Chi Minh City, Vietnam 2Key Laboratory of Materials Technology, HCMUT–VNUHCM 268 Ly Thuong Kiet Street, Ward 14, District 10, Ho Chi Minh City, Vietnam 3Department of Macromolecular Science & Engineering, Kyoto Institute of Technology Matsugasaki, Sakyo–ku, Kyoto 606–8585, Japan *Email: nthhoa@hcmut.edu.vn Received: 30 December 2016; Accepted for publication: 3 March 2017 ABSTRACT A high–contrast X–ray computed tomography (XCT) applied to the ternary polymer blends of poly(methyl methacrylate) (PMMA), polypropylene (PP) and polyamide 12 (PA12), we investigated micro–structure three–dimensional (3D) images of blends with gradually increasing of molecular weight (Mw) of PMMA. The 1:1:1 mixture of PMMA/PP/PA12 were prepared by mixing on an internal mixer at 200 °C, then annealing at 200 °C under compressor of 5 MPa in order to restore the crystalline structure of polymer blends. After that, blends were compressed molding and cooled by water. Finally, they were stored in the vacuum oven at the same annealing temperature before taking XCT and then rendering to 3D images. Changing various methods of annealing time, we could observe vary 3D internal structure clearly of these blends. We also conclude the effect between Mw of PMMA and the morphologies of these ternary polymer blends. Keywords: X–ray computed tomography, three–dimensional micro–structure image, ternary polymer blends. 1. INTRODUCTION X–ray computed tomography is known as a CT scan, and it is widely used in medicine to reveal internal hard tissue structures. The same technique can be used to reveal the internal three–dimensional structure and component distribution within materials. Three–dimensional imaging data are available by scanning an X–ray beam in two dimensions across a specimen while rotating about a single axis to include three dimensions in the final image. The X–ray image shows components distributed within the specimen, and cross sections or slices made Effect of poly(methyl methacrylate) molecular weight on its ternary polymer blends micro– 170 through any plane give the distribution of components within that plane. Contrast in the images is reliant on a change in electron density about atoms within the material. CT scanning is a nondestructive test to map the volume distribution of components in a material. Images are processed to provide surface rendering, volume rendering, or image segmentation [1]. Until 2010, more than 500 XCT–installations for industrial and scientific applications in Europe. There are two major application areas of XCT in science and industry: non–destructive testing of materials and dimensional measurement (metrology). XCT is able to measure internal or hidden structures completely without destroying the specimen. Determination of the three–dimensional (3D) distribution of heterogeneities and structures is of primary concern in the field of materials characterization and quality control. XCT provides statistically significant estimates of volume fractions of heterogeneities in materials depending on the spatial and contrast resolution [2]. Multiphase blends consisting of two or more incompatible polymers have achieved major economic importance in the plastics industry. The most widespread examples are impact modified thermoplastics where a rubber is micro dispersed in a glassy polymer matrix. Some materials are reported to have co–continuous phases of different thermoplastics. Most commercial materials have two phases and are formed from two main polymers with minor amounts of a third, compatibilizing polymer, typically a graft or block copolymer [3]. Polymer blends with in homogeneities 10 – 0.1 micrometer, the methods that observing morphology is electron microscopy: SEM, TEM [4]. Besides that, various polymer blend systems have been investigated by using high contrast XCT. The contrasts of various polymers were surveyed and found that many kinds of polymers can be distinguished under XCT. Then, the phase separation structures can be clearly visualized in 3D without any staining [5]. X–ray CT for polymer science with advantages: no staining, high contrast and quick operation. Recently, high–contrast X–ray CT has been optimized for use with polymeric materials and several observations of the polymer blends have been reported. Its spatial resolution is ~ 3 μm at present [6]. Contrasts of the polymer materials under a high contrast X–ray computerized tomography (XCT) are comprehensively investigated. We developed a high contrast XCT, and demonstrated its capabilities to polymer systems, such as polymer blends. Then we got a hypothesis that the pixel values of the cross–sectional image obtained by XCT agree with the X–ray absorption coefficient at 15 KeV. This hypothesis is intensively examined by using various polymers. Consequently, we propose an empirical criterion that 0.1 cm–1 difference in the X–ray absorption coefficients at 15 KeV is necessary to distinguish the polymers under XCT. This criterion is also confirmed in the polymer blend systems [2]. It is now commercially available from Beamsense Co. Ltd. [2, 4, 7]. In this paper, blends of PMMA/PP/PA12 1/1/1 were prepared to get 3D micro–structure images with various molecular weight of PMMA. As mentioned in previous studies [5, 8], three types of polymers with distinct colors together while being photographed 3D microstructure XCT. 2. MATERIALS AND METHODS PP used was Novatec ® MA1B M26831 with a weight–average molecular weight (Mw) of 25×104. Nylon 12 (PA12) is in semi–crystalline state, industrial grade. PMMA is in amorphous state with Mw in the range of 15,000–70,000, density of 1.18 g/cm3. Both PA12 and PMMA were purchased from JPC – Japan Polychem Corporation. All chemicals were used as received without further purification. The three polymer components were melt–blended at 200 °C with 1/1/1 weight fraction in a twin screw mixer (IMC-16C, Imoto Industry, Co. Ltd., Japan). Then the mixture was melt– pre air va an Po of we im En int 1 tra pro aft vie Th an ric in rec res am mo PA ssed and an environmen cuum condit Table 1 Blends 1 Blends 2 Blends 5 Blends 3 Blends 4 Blends 6 The samp d then subje lymer Mech Technology re acquired age (at Lab gineering – ervals. At ea s, and they nsmission i jection algo The use m er creating a ws. Users a e cross–sect d Figure 3; w h–phase is w the introduc onstructed i pectively. B ount of the o When we lecular weig 12 phase nealed at 20 t in order to ion at –0.1 M . Component PP PA x x x x x x le was cut i cted to X–ra anics – Depa . The X–ray using a char oratory of P Kyoto Inst ch rotation were avera mages were rithm. ulti planar three dime re able to ch ional image hile MPR hite, PA12 tion, the X–r mage, they y surveying xygen and n use the high ht of PMM than PP wa 0 °C for sur develop the Pa, 70 °C. s of ternary p –12 PMM 15k x 1 x x x x x nto the cylin y CT (FLEX rtment of M generator t ge–coupled olymer Me itute of Tec angle, four t ged to pro reconstruc Figure 3. RESU reformatting nsional volu ange the la of the PP/P mode ones a rich–phase i ay absorptio suggest that the pixel in itrogen sign er Mw of P A again be s evident. P vey hours ( phase separ olymer blend A PMMA 35k 2 drical roun -M863-CT, acromolecu ube was ope device (CC chanics – D hnology), t ransmission vide a total ted into a 1. Experimen LTS AND (MPR) rec me. The M yout, view m A12/PMMA re Figure 2 s light gray, n of the ma PMMA has tensities ov ificantly inc MMA into 7 doubled. Ho P is now s Ho 0–8 hours) i ation structu s PMMA/PP/ PMMA 70k 5 d shape of 2 Beamsense lar Science a rated at 40 D) with a C epartment he sample images were exposure 3D image u tal procedure DISCUSSI onstructs tw PR mode al odes and th obtained by and Figure and PP rich– terial corresp larger X–ra er various p rease the pix 0,000, this wever, the i pherical par a T. Nguyen n the vacuum re. After tha PA12 1:1:1 in PMMA 98k PM 1 3 0 × 2 mm ( Co. Ltd., Jap nd Engineer kV, and the sI scintillato of Macromo was rotated taken with time of 4 s sing a stan . ON o–dimension lows to view e viewing a X–ray CT 3A. Inside t phase is dar onds to the y absorbanc olymers, it el intensity trend has no ncreased siz ticles no lar , Yukihiro N condition t, they were experiments MA 20k PMM 540 4 6 diameter of an) at Labo ing – Kyoto transmissio r. To constr lecular Sci over 180° the exposur . The obtai dard filtere al views of the image ngles in MP is shown in he structure k gray. As d pixel intens e than PA 1 is concluded in our XCT. t changed th e of the PM ger in size ishikawa 171 or in the stored in . A k 20 mm), ratory of Institute n images uct a 3D ence and at 0.25° e time of ned 720 d back– a series in three R view. Figure 2 , PMMA iscussed ity in the 2 and PP that the ough the MA and than the Eff 17 con den an F PA als ob Af inc str dim com sph dis exp con res blo for A A ect of poly(m 2 tinuous pha sity of mol d images 3D igure 2. Cros With low 12 phases c o low visco servation of ter 8 hours, rease annea ucture. Any ensional c puter simu erical shape tributed tog lained by t stitute the ult, they for ck phase (P m. Figure ethyl metha ses of PMM ecular bond structure Fi s–sectional im Mw of PMM an separate sity so it tre morphology the micro s ling time, of phases ar ross–section lations [3]. forward an ether into c he increasin major challe m many mix MMA and 3. Cross–sect crylate) mol A and PA s correspond gure 3, pred age of PP/PA A (15,000) more clearl nds to be a is from 4 tructure of p PP phase is e not contin s. This kin In Figure d there are ontinuous p g of the mel nge of cont ed block un PA 12) with ional image an ecular weigh 12. This phe ing to mole iction was il 12/PMMA b in Figure 2 y into a big continuous hours to 6 h olymer blen more stab uous and the d of ternar 2A with Mw many differ hases with t viscosity o inuity which clearly. Alon PP compo d 3D X–CT PMMA = 70 B t on its terna nomenon is cular weigh lustrated viv lends , Mw o B, after hea phase each phase. The s ours, theref ds is absolu le that it co interfaces t y phase str of PMMA ent particle smaller siz f the PMM will be di g with that, nent will ca image of PP/P ,000. ry polymer understood t increase. T idly. f PMMA = 35 ting treatme other. PMM uitable anne or we can s tely fixed. uld dispers end to be fla uctures wa = 35,000 sizes. While e than PP A in the mix ffused by ph the surface use phase P A12/PMMA blends micro as an increa hrough pho ,000 (A); 15, nt the PP ph A has low aling time f ee big phase It could be e inside the t, or straigh s predicted , PP phases PA 12 and sphere. Thi ture. Then ase of PA tension of th P spherical blends, Mw – se in the tographs 000 (B). ases and Mw and or better clearly. when we micro– t in two– only in become PMMA s can be it cannot 12. As a is mixed particles of Hoa T. Nguyen, Yukihiro Nishikawa 173 Through changing patterns molecular weight, the annealing time allows most clearly observed structures blends are from 4–8 hours. This result coincides with the statement at the beginning of this discussion. Thereby we could realize the role of the annealing process parameters through time and environmental conditions affect the steady recovery of micro– structures of polymer blends. In volume segmentation, components from the image are separated based on a threshold so that the remainder of the image is omitted [1]. 4. CONCLUSIONS Research about the molecular–weight dependance on blends polymer X–CT images, we have demonstrated visually the dependance of PMMA molecular–weight (3 types of Mw) in blends PMMA/PA12/PP 1/1/1 using 3D X–CT microstructure analyzing system; and how about the phase structure of a ternary blends with 3D images. Learn how about the preparation of sample affect to XCT 3D images: mixing, compressing annealing and cooling, vacuum storage, 3D image reconstruct and analysis procedures. We demonstrated the advantage of the high– contrast X–ray CT by applying it to the ternary polymer blends. Since XCT gives the three– dimensional images of the object including its internal structure, XCT is a powerful research tool in polymer science. Acknowledgements. 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