Summary thesis in Chemistry: Study on some environmentally friendly polymer materials and application on preparing plant nursery

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The research using some advanced, environmentally friendly materials such as water-absorbing polymers and soil-binding polymers in potting medium is also a new direction to improve water retention. The study of manufacturing polybags with different degradation time combined with the use of SAP and PAM in substrates of pots to improve some features of the current nursery.

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Nội dung Text: Summary thesis in Chemistry: Study on some environmentally friendly polymer materials and application on preparing plant nursery

MINISTERY OF EDUCATION VIETNAM ACADEMY OF AND TRAINING SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY ------------- NGUYEN THI THUC STUDY ON SOME ENVIRONMENTALLY FRIENDLY POLYMER MATERIALS AND APPLICATIONS ON PREPARING PLANT NURSERY Scientific Field: Organic Chemistry Classification Code: 944 01 14 DISSERTATION SUMMARY HA NOI - 2020
dissertation was completed at: Institute of Chemistry Vietnam Academy of Science and Technology Scientific Supervisors: 1. Dr. Trịnh Đức Công Institute of Chemistry - Vietnam Academy of Science and Technology 2. Prof. Dr. Nguyen Van Khoi Institute of Chemistry - Vietnam Academy of Science and Technology 1st Reviewer: ........................................................................... ................................................................................. ................................................................................. 2nd Reviewer: .......................................................................... ................................................................................. ................................................................................. 3rd Reviewer:........................................................................... ................................................................................. ................................................................................. The dissertation will be defended at Graduate University of Science And Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay District, Ha Noi City. At ….. hour….. date….. month …..2020 The dissertation can be found in National Library of Vietnam and the library of Graduate University of Science And Technology, Vietnam Academy of Science and Technology.
1 INTRODUCTION 1. Background Nowadays, waste polyethylene plastic (PE) has been posing serious environmental pollution problems and damaging ecosystems. PE usually does not decompose and therefore persists as waste in the environment for a very long time, causing harm to human health. Due to the advantages of cost as well as simple processing method, plastic films made from polyethylene (PE) are being used very popular in many fields such as packaging, covering and processing create nursery nurseries in agriculture. In Vietnam, plants nursery for fruit trees and forestry trees is increasing, almost seedlings are grown in polybags. The nursery is a tree growing environment and contains the necessary nutrition to provide the plant with its first growth and development stage. The composition and characteristics of nursery pots play a decisive role in the quantity, quality of seedlings and saves planting. Self-destructing polybags made from recycled polyethylene and additives promoting oxidation are a new research direction that contributes to reducing environmental pollution. At the same time, the use of this nursery bag brings a high economic significance, saving the tearing costs. In addition, the research using some advanced, environmentally friendly materials such as water-absorbing polymers and soil-binding polymers in potting medium is also a new direction to improve water retention. Increasing the amount of moisture available in the root zone, keeping nutrients, preventing the process of washing away nutrients in the soil and linking soil particles, helping not to break the nursery when transporting to the planting or growing plants. , reduce watering times, save labor and improve the quality of seedlings. For the above reasons, we propose the dissertation: ““Study on some environmentally friendly polymer materials and application on preparing plant nursery” 2. Objectives of the dissertation -Research on the degradation process of PE films containing prooxidant additives and recycled polyethylene. After that, preparing plant polybags with different time of degradation. - Study on properties of substrates of pots when containing superabsorbent water polymer and polyacrylamides - Evaluating the applicability of environmentally friendly plant nurserys for some plants. 3. Main contents of the thesis -Research on the degradation process of PE films under accelerated
2 conditions (thermal oxidation and photo-oxidation), natural weathering. After that, preparing plant polybags with different time of degradation. - Study on retain moisture ability of AMS-1 and the soil structural strength ability of PAM. These materials used to improve some features of the substrates. -Aplication environmentally friendly plant nursery for Acacia auriculiformis, Pinus caribaea and Eucalyptus 4. Structure of the thesis The dissertation has 128 pages, including the Preface, Chapter 1: Overview, Chapter 2: Experiment, Chapter 3: Results and discussions, Chapter 4: Conclusions, Pubblications, with 51 images, 25 tables and 97 references DISSERTATION CONTENTS CHAPTER 1. LITERATURE REVIEW The literature review has presented an overview of the characteristics and structure of plant nursery including 2 main components: polybags and substrates. Advantages and disadvantages of the current plant nursery, the research situation in the country and the world about plant nurserys. Now, the world has been many studies on manufacturing degradable polybags but have not been any studies on manufacturing polybags with different degradation time. - Polybags based on polyethylene is a new research direction that contributes to reducing environmental pollution. At the same time, polybags brings a high economic significance, save planting. - SAP and PAM are advanced materials, environmentally friendly materials with good features for soil improvement and can be used for plant nursery. Therefore, the study of manufacturing polybags with different degradation time combined with the use of SAP and PAM in substrates of pots to improve some features of the current nursery. CHAPTER 2. EXPERIMENTS 2.1. Materials and equipments 2.1.1. Materials Recycled PE resins grade 1, low density polyethylene LDPE 260 GG, dark carbon HAF N330, pro-oxidant additives Mn(II) stearate, Fe(III) stearate and Co(II) stearate,, process additives PPA-3MB910, Urease fertilisers,
3 phosphate fertilisers, NPK fertilisers, superabsorbent water polymer (AMS-1), polyacrylamide (PAM). 2.1.2. Equipments Plastic SJ-35 Single Screw Extruder, twin screw extruder Bao Pin, Supermix BP-HS100, Brabender Plasto Graph EC plus 3, INSTRON 5980 mechanical measuring device, UV-260 accelerated weathering tester, Thermo Nicolet Nexus 670 Fourier Transform Infrared Spectroscopy, SM-6510LV and JEOL 6490 scanning electron microscope, thickness measuring instrument Mitutoyo IP67, Scientech scales, readability 0,001 (g), oven and laboratory equipments. 2.2. Methods 2.2.1. Film preparation Sample mixing: rPE and LDPE plastic were cleaned and dried at 700C for 3 hours, then weighed quantitatively according to rPE/LDPE ratios and content of PPA. The material mixture is sealed on Brabender Plasto Graph EC plus 3 at the temperature of 1500C, the mixing speed 35 rpm, the mixing time 3 minutes. Pressing the sample into sheets: The product after being taken from the mixing chamber of the Brabender is transferred to the hot press at 1450C, the pressure is 15 Mpa in 4 minutes. During the pressing process, adjust the compression limit so that the final sample has a thickness of about 1 mm. Remove the sampling mold and stabilize the sample for 24 h before testing. These films were made by extrusion blowing using a SJ-35 extruder with a 35 mm screw of L/D 28:1, Screw area temperatures: 154, 176, 167, 168 and 165oC. - Effect of rPE /LDPE ratios: Evaluation of physical properties và SEM scanning electron microscope. of rPE/LDPE plastic at ratios: 0/100, 75/25, 80/20, 85/15, 90/10, 95/5 and 100/0. - Effect of PPA process additives at ratios: 0%, 1%, 2%, 3% and 4% through torque, mechanical properties, FTIR infrared spectrum and SEM scanning electron microscope. - The PE films were carried out thermo- and photo-oxidatives and natural weathering process to evaluate the degradation degree. 2.2.2. Study on retain moisture ability of AMS-1 and the soil structural strength ability of PAM on substrates. The content of AMS-1 and PAM in substrates of pots as follows: ĐC: do not contain AMS-1 and PAM materials. AMS1: 0,8g/kg substrates
4 PAM: 2 mg/kg substrates AMS1 + PAM: 0,8g AMS-1 + 2mg PAM (on a kilogam substrates) Growing medium (GT1) composing of hilly: alluvium period 2:1 ratio. AMS-1 is soaked in water for 30 minutes to achieve maximum water absorption and then mixed with potting soil. PAM is completely dissolved in water and applied directly into the potting medium. At that time, the moisture content of the potting medium is about 70%. - The moisture capacity of AMS-1 has been assessed through soil permeability, moisture and the swelling ability in different salt solutions. - The soil structural strength ability of PAM is shown through sedimentation speed, bind soil particles, retain nutrients ability - The properties of the materials when using AMS-1 and PAM are evaluated through: soil adhesion, maximum moisture content and porosity of potting medium. 2.2.3. Aplication environmentally friendly plant nursery for Acacia auriculiformis, Pinus caribaea and Eucalyptus. - Type of plant: Acacia auriculiformis, Pinus caribaea and Eucalyptus. - Location: Dao Duc Plant Breeding Science and Technology Center. * Acacia auriculiformis tree: - PE-Keo : Polyetylene polybags + substrates (soil) - TH-Keo: 6-8 months self destroying polybags + substrates (0,8g AMS-1/ kg substrates và 2mg PAM/kg substrates) * Pinus caribaea tree - PE-Thong: Polyetylene polybags + substrates (soil) - TH-Thong: 9-11 months self destroying polybags + substrates (0,8g AMS-1/ kg substrates và 2mg PAM/kg substrates) * Eucalyptu tree - PE-BĐ: Polyetylene polybags + substrates (soil) - TH-BĐ: 11-14 months self destroying polybags + substrates (0,8g AMS-1/ kg substrates và 2mg PAM/kg substrates) Evaluate to retain moisture, soil binding ability of substrates and the self- destruction of the polybags. Number of watering times (times), rate of life plants (%), Rate of reaching garden standard trees (%), tensile strength (MPa), elongation (%), heights growth (cm), diameters root (cm), heights root (cm). CHAPTER 3. RESULTS AND DISCUSSIONS 3.1. Effect of ratio of prooxidant additives on the degradation of polyethylene films (PE)
5 The mechanical properties of films are shown in table 3.1: Table 3.1: The mechanical properties of rPE / LDPE materials Content of materials (v/v) Tensile strength Samples Elongation (%) rPE LDPE (MPa) PE0 0 100 24, 67 641,54 PE1 75 25 22,95 622,24 PE2 80 20 21,92 585,15 PE3 85 15 20,47 555,12 PE4 90 10 18,74 528,31 PE5 95 5 16,06 421,53 PE6 100 0 15,03 411,23 The mechanical properties of the base resin complexes decrease when increasing rPE contents. Thus, increasing the content of rPE, the properties of the rPE/LDPE combination gradually decrease because rPE has undergone the manufacturing process, creating the decomposition process of rPE that happened FTIR spectrum in Figure 3.1. Comparison FTIR spectrum of LDPE and rPE shows that there is a presence of carbonyl functional group on FTIR spectrum of rPE at pic 1714.30 cm-1 while LDPE spectrum does not appear in this functional group. However, the peak strength of 1714.30 cm-1 is very small due to the type of recycled plastic. Figure 3.1: FTIR-spectroscopy of LDPE and rPE grade 1 In addition, The changes in the surface morphology of PE1, PE2, PE3 and PE4 are presented in Figure 3.2. Figures 3.2: SEM micrographs of PE1, PE2, PE3 và PE4 Figure 3.2 is shown that the distribution of the constituents in the sample (PE1, PE2, PE3) is uniform while that of the PE4 sample has begun to appear
6 uneven, clumping. It proves that samples PE1, PE2, PE3 have better compatibility than samples of PE4. This is consistent with the explanation of the decrease in tensile strength of the composite resin composites. 3.2. Effect of PPA process additives to rPE/LDPE properties The impact of process additives PE3A0 (0%), PE3A1 (1%), PE3A2 (2%), PE3A3 (3%), PE3A4 (4%) are assessed through torque, gloss, mechanical properties and SEM. Research results of process additives on torque are shown in Figure 3.2. 60 PE3A0 Momen xoắn (Nm) 50 PE3A1 40 PE3A2 30 PE3A3 20 PE3A4 10 0 0 1 2 3 4 5 Thời gian (phút) Figures 3.2: Effect of process additives to torque Figure 3.2 shows that when using process additives, the torque of the sample decreases compared to the sample without using PPA. Due to the PPA covering the surface of the shaft to form a buffer to reduce friction between the shaft and the plastic flow thus reducing torque. When increasing the content of PPA from 1% to 2%, the stabilizing time gradually decreases from 2 minutes to 1.5 minutes. Therefore, with content of PPA 2%, it is suitable. Research to effect of PPA additives on the films gloss when are shown in the following figure: PE3A4 PE3A3 PE3A2 PE3A1 PE3A0 76 78 80 82 84 86 88 Độ Bóng Figures 3.3: Films gloss with different PPA contents Figure 3.3, it was found that the sample using PPA resulted in 4% more gloss than the sample without using. Thus, during PPA has worked to improve the gloss of the product [86]. This is explained by the fact that during the PPA
7 reduces friction between the shaft and the plastic, so that the flow of plastic does not have much difference between the velocity at the center and the edge so minimizing the formation of folds thus increase the surface smoothness and increase the gloss of the product [97]. Tensile strength and elongation at break of the films samples are shown in Table 3.2 below. Table 3.2: Mechanical properties of films containg different PPA contens Samples Tensile strength (MPa) Elongation (%) PE3A0 19,87 555,12 PE3A1 20,28 560,64 PE3A2 20,67 567,82 PE3A3 20,19 553,34 PE3A4 19,65 552,11 The results shown that PPA content does not affect the mechanical properties of materials. When increasing the content of PPA from 0% to 2%, the tensile strength and elongation at break increase and when PPA content from 2% to 4%, the tensile strength and elongation at break decrease. However, the increase and decrease of physical properties of the material is not much. This can be explained by the fact that PPA are polar so they are not compatible with PE to form a very small dispersion phase in the main polymer phase [89]. The SEM of PE3A0 and PE3A2 samples are shown in Figure 3.4. PE3A0 PE3A2 Figures 3.4: SEM micrographs of PE3A0 và PE3A2 samples PE3A2 samples containg PPA content 2% for smooth and uniform film surface than PE3A0 samples. This can be explained by the addition of PPA reduce friction between the shaft and the plastic, so the flow of plastic does not have much difference between the velocity in the center and the boundary so minimizing the formation of folds. 3.3. Effect of prooxidant additive mixture content on the degradation of polyethylene films rPE- oxo The mechanical properties of films contaning prooxidant additive mixture are shown in Table 3.3 below:
8 Table 3.3: Mechanical properties of films contaning prooxidant additive mixture * Prooxidant additive Tensile strength Elongation Samples mixture (%) (MPa) (%) PE3A2Ox0 0 20,67 567,82 PE3A2Ox02 0,02 20,42 558,42 PE3A2Ox04 0,04 20,34 554,65 PE3A2Ox06 0,06 20,22 553,02 PE3A2Ox08 0,08 20,14 552,14 Table 3.3 shows that the mechanical properties of rPE-oxo samples decrease when increasing the content of oxidation additive mixture, but due to the content of the mixture of oxidation promotion additives in the small rPE- oxo membrane, leading to the Physical properties reversed in little samples. 3.3.1. Thermo-oxidation of rPE-oxo films Elongation at break and tensile strength of of PE3A2Ox0, PE3A2Ox02, PE3A2Ox04, PE3A2Ox06 and PE3A2Ox08 films with anh without prooxidation additives during thermal oxidation are shown in Figure 3.5 below: 30 PE3A2Ox0 600 PE3A2Ox0 Độ dãn dài khi đứt Độ bền kéo đứt PE3A2Ox02 500 PE3A2Ox02 PE3A2Ox04 PE3A2Ox04 20 PE3A2Ox06 400 (Mpa) PE3A2Ox06 300 (%) 10 200 100 0 0 0 18 36 54 72 90 0 Thời18 36hủy oxy54hóa nhiệt gian phân 72(giờ) 90 Thời gian phân hủy oxy hóa nhiệt (giờ) Figures 3.5: Changes in elongation and tensile strength of rPE-oxo films Results showed that the tensile strength and elongation at break of all samples decreased with the test time. The samples PE3A2Ox02, PE3A2Ox04, PE3A2Ox06 and PE3A2Ox08 are considered to self-destruct respectively after 90 hours, 72 hours, 54 hours and 36 hours of thermal oxidation. FTIR spectras of films before and after thermal treatment were shown in Figure 3.6 below: Figures 3.6: FTIR spectra of rPE-oxo films after thermal oxidation
9 Figure 3.6 showed that an increase in absorption in the carbonyl region was recorded with time in the samples thermally aged containing pro- oxidants. The plot of 1640 - 1850 cm-1 range of carbonyl groups, as determined by the overlapping bands corresponding to acids (1710 - 1715 cm-1), ketones (1714 cm-1), aldehydes (1725 cm-1), ethers (1735 cm-1) and lactones (1780 cm-1) was observed. Figure 3.7 show changes in the carbonyl index of rPE-oxo films with and without pro-oxidant additives during thermal oxidation. 6 PE3A2Ox0 PE3A2Ox02 Chỉ số CI 5 PE3A2Ox04 4 PE3A2Ox06 3 PE3A2Ox08 2 1 0 0 18 36 54 72 90 Thời gian oxy hóa nhiệt ( giờ) Figures 3.7: Carbonyl index of rPE-oxo films after thermal oxidation Oxidation of PE films leads to the accumulation of carbonyl groups. As the oxidation time increases, the oxygen absorption level and the rate of intermediate products formation increases resulting in rapidly increasing carbonyl group concentration. After 90 hours of oxidation, the CI of PE3A2Ox0, PE3A2Ox02, PE3A2Ox04, PE3A2Ox06 and PE3A2Ox08 samples were 0.65; 4.21; 4.52; 5.02 and 5.22, respectively. The changes in the surface morphology of thermally degraded PE3A2Ox0, PE3A2Ox02 and PE3A2Ox08 films are shown in Fig. 3.8. PE3A2Ox0bđ PE3A2Ox0 after 90h PE3A2Ox02 after 90h PE3A2Ox08 after 36h Figures 3.8: SEM micrographs of PE3A2Ox0bđ, PE3A2Ox02 and PE3A2Ox08 after thermal oxidation SEM images of PE3A2Ox02 and PE3A2Ox08 membrane samples containing oxidation-accelerating additives show that the surface is destroyed, developing into tears and grooves due to the catalytic activity of the oxidation- enhancing additives under the impact. of heat. The surface destruction causes different material zones to appear on the surface. SEM images also show that
10 the defect rate on the membrane surface is directly proportional to the amount of additives in the membrane. 3.3.2. Photo-oxidation of rPE-oxo films A decrease in elongation at break and tensile strength of PE films during photo-oxidative degradation is shown in Figure 3.9. 25 PE3A2Ox0 600 PE3A2Ox0 PE3A2Ox02 PE3A2Ox02 Độ bền kéo đứt (Mpa) Độ dãn dài khi đứt (%) PE3A2Ox04 PE3A2Ox04 20 PE3A2Ox06 PE3A2Ox06 PE3A2Ox08 400 PE3A2Ox08 15 10 200 5 0 0 0 6 12 18 24 30 0 6 12 18 24 30 Thời gian thử nghiệm (ngày) Thời gian thử nghiệm (ngày) Figures 3.9: Mechanical properties of films after 30 day photo-oxidation Results showed that the tensile strength and elongation at break of the samples decreased with increasing oxidation time. Elongation at break is commonly used to monitor degradation process rather than other mechanical properties. The film is considered to be capable of degradation when the elongation at break is ≤ 5% according to ASTM D5510 và ASTM D 3826 standard. Therefore, samples PE3A2Ox08, PE3A2Ox06, PE3A2Ox04 and PE3A2Ox02 are considered to be self-destruct after 12 days, 18 days, 24 days and 30days photo-oxidation. FTIR spectrum of PE3A2Ox0, PE3A2Ox02, PE3A2Ox04, PE3A2Ox06 and PE3A2Ox08 film samples after 30 days of photo-oxidation are shown in Figure 3.10: Figures 3.10: FTIR spectra of films after photo-oxidation The results show that peaks in the range of 1700 - 1800 cm-1 are typical for the carbonyl group. Absorption peaks in this range indicate the presence of various oxidizing products such as: aldehydes or esters (1733 cm-1), carboxylic acid (1700 cm-1), γ-lactones (1780 cm-1) [94]. The changes in the surface morphology of the sample after photo-
11 oxidation is shown in Figure 3.11. PE3A2Ox0 bđ PE3A2Ox0 after 30 days PE3A2Ox04 after 24 days PE3A2Ox08 after 12 days Figures 3.11: SEM micrographs of films PE3A2Ox0 bđ, PE3A2Ox0, PE3A2Ox04 và PE3A2Ox08 after photo-oxidation The results showed that PE3A2Ox02, PE3A2Ox04, PE3A2Ox06, PE3A2Ox08 samples after 30, 24, 18 and 12 days of moist heat photochemical oxidation test showed signs of surface destruction phenomenon. PE3A2Ox0 sample after 30 days of surface testing is still relatively smooth, without defects. Samples of PE3A2Ox04 and PE3A2Ox08 appear to have a clear phase separation on the material areas and the damage level increases markedly when increasing the content of oxidation promotion additives in the membrane. 3.3.3. Natural weathering process The changes elongation at break and tensile strength of PE films during Natural weathering process is shown in Figure 3.12. 30 PE3A2Ox0 600 PE3A2Ox0 Độ bền kéo đứt (Mpa) PE3A2Ox02 PE3A2Ox02 Độ dãn dài khi đứt (%) PE3A2Ox04 PE3A2Ox04 20 PE3A2Ox06 400 PE3A2Ox06 PE3A2Ox08 10 200 0 0 0 3 6 9 12 15 0 3 6 9 12 15 Thời gian (Tháng) Thời gian (Tháng) Figures 3.12: Mechanical properties of films on Natural weathering process The results showed that with the PE3A2Ox0 sample after 15 months of exposure, the tensile strength of the sample maintained above 60% of the original value. For samples containing oxidation promotion additives, the tensile strength decreases with increasing the exposure time and the rate of reduction of tensile strength is proportional to the additive content. As such, PE08 samples are considered to self-destruct after 6 months, samples PE3A2Ox06, PE3A2Ox04 and PE3A2Ox02 are considered to be degradable after 9, 12 and 15 months, respectively
12 FTIR spectrum of PE3A2Ox0, PE3A2Ox02, PE3A2Ox04, PE3A2Ox06 and PE3A2Ox08 film samples after 15 months Natural weathering process are shown in Figure 3.13. Figures 3.13: FTIR spectrum of rPE – oxo film after 15 months Natural weathering process Peaks in the range of 1700 - 1800 cm-1 are typical for the carbonyl group. Absorption peaks in this range indicate the presence of various oxidizing products such as: aldehydes or esters (1733 cm-1), carboxylic acid (1700 cm-1), γ-lactones (1780 cm-1) [95], the intensity of the peak increases with time of exposure. In addition, the presence of weak peak intensity of 1641 cm-1 peak characterized by valence oscillation of vinyl group (C = C) [96]. Figure 3.14 show changes in the carbonyl index of rPE-oxo films after Natural weathering process. 4,5 PE3A2Ox0 4 PE3A2Ox02 3,5 PE3A2Ox04 3 Chỉ số CI PE3A2Ox06 2,5 PE3A2Ox08 2 1,5 1 0,5 0 0 1 2 3 4 5 6 Thời gian (tháng) Figures 3.14: Carbonyl index of rPE-oxo after Natural weather process. The results showed that PE3A2Ox0 sample has a very small CI value. The samples containing additives promoting oxidation, the CI value increased sharply after 6 months of natural exposure. The carbonyl index increases proportional to the amount of oxidation promotion additives in the sample. The changes in the surface morphology of PE3A2Ox0 bđ, PE3A2Ox0, PE3A2Ox02 and PE3A2Ox08 sample s after Natural weathering process are
13 shown in Figure 3.15.: PE3A2Ox0 bđ PE3A2Ox0 PE3A2Ox02 PE3A2Ox08 Figures 3.15: SEM micrographs of films PE3A2Ox0 bđ, PE3A2Ox0, PE3A2Ox02 và PE3A2Ox08 after Natural weathering process The results showed that compared with PE3A2Ox0 bđ sample, the surface of PE3A2Ox0 samples was least affected, the surface was relatively smooth with few defects, while the surfaces of samples PE3A2Ox02 and PE3A2Ox08 were destroyed, no longer Smooth that appear defects and cracks on the material surface. 3.4. The degradability of PE films containing prooxidant additives in natural conditions 3.4.1. The degradability of rPE- oxo films containing prooxidant additives in soil The percentage weight loss of rPE- oxo films containing pro-oxidant additives after burying in soil is shown in Table 3.4. Table 3.4: Weight loss of rPE- oxo films after burying in soil (%) Times Weight loss of rPE- oxo films after burying in soil (%) (Months) PE3A2Ox02 PE3A2Ox04 PE3A2Ox06 PE3A2Ox08 1 10,72 12,09 12,86 13,45 2 11,39 12,12 21,46 36,72 3 14,14 20,48 33,09 68,56 4 21,43 31,21 41,23 84,23 5 29,18 48,44 52,11 92,54 6 39,21 63,74 70,87 - The weight loss of PE films containing pro-oxidant additives was much more than the control film. After 6 months, the weight loss of PE3A2Ox02, PE3A2Ox04 và PE3A2Ox06 films were 56,21% và 63,74% and 70,87%. respectively. Particularly PE3A2Ox08 film after 5 months buried in the soil has decreased by 92.54% of weight and after five months, no pieces of this film were recovered in the soil. The FTIR spectra of PE3A2Ox08 film after burying 5 months in soil is shown in Figure 3.16.
14 75 70 65 60 778.93 533.72 55 472.80 1576.71 50 2659.81 1294.48 1627.19 1100.56 45 1178.19 1372.46 1030.51 %T 40 3377.66 1413.28 35 724.57 30 25 1712.17 1464.60 20 2852.13 15 2912.50 10 5 4000 3000 2000 1000 Wavenumbers (cm-1) Figures 3.16: FTIR of PE3A2Ox08 film after burying for 5 months in soil The results showed that after burying in the soil, there appeared specific areas possibly due to the oxidized polymer circuits decomposed by microorganisms in the soil, this result is quite consistent with the announcement of E. Chiellini. et al. [48]. First, there appears a 3377 cm-1 peak characteristic for the –O-H bond, a peak of 1712.17 cm-1 is typical for the carbonyl group, a broader peak range than thermal oxidative decomposition and moist heat photos. SEM images of PE3A2Ox02 and PE3A2Ox08 samples after burying in soil are shown in Figure 3.17. PE3A2Ox02 PE3A2Ox08 Figures 3.17: SEM image of film surface after soil burial SEM image shows that the surface of PE3A2Ox08 films have changed strongly, appeared holes and craters. The surface of the polymer after biological attack was physically weak and readly disintegrated under mild pressure [97]. 3.4.2. The degradability of rPE- oxo films containing prooxidant additives in activated sludge The percentage weight loss of rPE- oxo films containing pro-oxidant additives after burying in activated sludge is shown in Table 3.5. Bảng 3.5: Weight loss of rPE- oxo films after burying in activated sludge (%) Months PE3A2Ox02 PE3A2Ox04 PE3A2Ox06 PE3A2Ox08 1 12,36 14,77 16,03 19,05 2 19,03 25,14 34,42 48,16 3 25,67 34,62 44,71 77,53
15 4 31,84 46,09 50,94 91,03 5 40,56 57,56 60,02 - 6 51,21 70,84 89,13 - After 6 months, the weight loss in samples PE3A2Ox02, PE3A2Ox04, PE3A2Ox06 were 51.21%, respectively; 70.84%; 89.13%. The PE3A2Ox08 sample lost almost completely mass after 5 months of immersion in activated sludge. Thus, after the degradation process, the membrane samples with large molecular weight, hydrophobic cleavage were divided into shorter circuits with small molecular weight and hydrophilic functional groups helped microorganisms. The material is more accessible to hydrolyze and consume these segments. The decomposition ability in activated sludge of PE3A2Ox08 sample was adopted by FTIR infrared spectrum and shown in Figure 3.18. 95.5 95.0 795.97 94.5 94.0 93.5 717.92 93.0 877.04 92.5 1712.79 92.0 91.5 1627.37 533.70 %T 91.0 415.33 90.5 464.66 90.0 89.5 89.0 88.5 1425.28 2850.13 88.0 3430.00 87.5 1030.50 2921.32 87.0 86.5 86.0 400 0 300 0 200 0 100 0 W av enu mber s ( c m- 1) Figure 3.18: FTIR of PE3A2Ox08 film after burying for 4 months in activated sludge Similar to when buried in the soil, after 4 months of soaking in activated sludge, the absorption band intensity in the range of 1700-1740cm-1 increases sharply and increases more than when buried in the soil. There is also a peak at 1627cm-1 that is specific to the –C = C– link and a peak at 3430cm-1 that is specific to the –O – H link. The 1030 cm-1 pic signal is specific to a broader and stronger ester group than is buried in the soil. SEM images of PE3A2Ox02 and PE3A2Ox08 samples after burying in activated sludge are shown in Figure 3.19. PE3A2Ox02 PE3A2Ox08 Figures 3.19: SEM image of film surface after burying in activated sludge
16 In both samples, it was found that the sample surface has decomposition, the surface structure has a clear phase separation, appearing different areas of materials. 3.5. Study on preparing self destroying polybags 3.5.1. Materials Based on the results of the research in section 3.1 to 3.4, rPE/LDPE resin composites were selected with the ratio 85/15, PPA content of 2% and the content of oxidation promotion additives from 0.02% to 0.08%. Materials are shown in Table 3.6. Tables 3.6: Materials for preparing self destroying polybags Unit:10 kg/batch Self destroying polybags Materials 6 months 9 months 12 months 15 months (TH6) (TH9) (TH12) (TH15) LDPE 1,4538 1,4541 1,4544 1,4547 rPE 8,2382 8,2399 8,2416 8,2433 prooxidant 0,008 0,006 0,004 0,002 additives PPA 0,2 0,2 0,2 0,2 C HAF N330 0,1 0,1 0,1 0,1 Total 10 10 10 10 + Effect of screw speed on film thickness: The thickness of the film is adjusted by changing the screw speed, fixed parameters: Traction speed of 850 rpm, inlet temperature of 1700C. The results are presented in table 3.7. Tables 3.7: Effect of screw speed on film thickness TT screw speed (rpm) film thickness (μm) 1 25 25± 6,4 2 27 35 ± 5,3 3 29 52 ± 4,6 4 31 68 ± 4,7 The results showed that when increasing the screw speed, the thickness of the film increased, whereas the speed of screw reduction, the film thickness decreased. With a film thickness of 35μm, the impact surface of the film is 27 rpm. Therefore, selecting screw speed of 27rpm is a fixed technology specification for further studies. + Effect of drag speed on film thickness The films blowing process has fixed the following technology
17 parameters: Screw speed 27 rpm, inlet temperature of 1700C. Traction speed is changed from 700 to 950 rpm. Results are presented in table 3.8. Tables 3.8: Effect of drag speed on film thickness TT drag speed (rpm) film thickness (μm) 1 700 50 ± 4,9 2 750 45 ± 5,2 3 800 41 ± 6,1 4 850 35 ± 3,8 5 900 30 ± 4,7 6 950 25 ± 4,6 Results showed that when increasing the drag speed, the film thickness decreased. Products elected nursery on the market today usually have a film thickness of 30-40µm. Therefore, choosing 850 rpm is a technology specification. + Effect of temperature on the properties of films The film blowing process is carried out at fixed technology parameters: 850rpm, screw speed 27rpm. Temperature is changed from 1550C to 2100C. mechanical properties of films is presented in table 3.9. Tables 3.9: Effect of temperature on the properties of films Temperature region(oC) Properties Machining Tensile Elongation mode 1 2 3 4 5 strength (%) (MPa) Mode 1 155 160 165 170 170 17,21 540,41 Mode 2 175 180 185 190 190 20,55 559,25 Mode 3 195 200 205 210 210 20,34 569,28 The results show that changing the temperature from mode 1 to mode 2 increases the mechanical properties of the membrane, because increasing the temperature above 1700C will increase the ability to mix the plastic particles, the long crystallization time makes streamlined molecular circuits. In contrast, when the initial temperature falls below 1700C, the time is short, the shape is poor. 3.6. Study on the effect of AMS-1 and PAM on the properties of the substrates 3.6.1. Effect of AMS-1 to retain moisture ability of substrates. Permeability is determined by the wetting capacity of the soil. Permeability and retain moisture ability of substrates when using AMS-1 shown in Figure 3.20 and Figure 3.21 below:
18 500 100 ĐC xử lý AMS1 Tính thấm của đất 400 Độ ẩm đất (%) 80 (mm/10 phút) 300 60 40 200 20 100 0 0 0 20 40 60 80 100 Xử lý AMS1 ĐC Thời gian (ngày) Figures 3.20: Permeability of substrates Figures 3.21: Retain moisture ability of substrates Permeability of substrates using AMS-1 is outstanding due to expand ability and pore of materials. AMS-1 increases retain moisture ability. During the 100days experiment, the amount of moisture in the soil with AMS-1 was greater than that in the control soil. From Figure 3.20 is shown that, using AMS-1 for better permeability than DC. Due to AMS- synthesized from sodium polyacrylate belongs to the hydrophilic polymer groups. There are two important groups found on the AMS-1 polymer chain: –Na+ and COO- hydrophilic groups. When introduced into water, there is an interaction between polymers and solvents, which is the hydration caused by the –COO- and Na+ groups to attract polarized water molecules [55-57]. Figures 3.22: Water absorption process of AMS-1 3.6.2. Study on stabilize structure ability of PAM Sedimentation speed of soil particles are shown in Figure 3.23 below: 6 Lượng cặn sa lắng (g/100ml) 5 xử lý PAM ĐC 4 3 2 1 0 0 10 20 30 40 50 Thời gian sa lắng (giây) Figures 3.23: Ability to remove suspended sediments over time