蠶絲纖維增強聚乳酸體系中柱晶的形成及其結(jié)構(gòu)分析
發(fā)布時間：2018-08-31 17:13
【摘要】：聚乳酸(PLA)具有較好的機械性能、生物相容性以及可降解性,應(yīng)用于生物醫(yī)療和包裝領(lǐng)域。由于PLA的結(jié)晶速率慢,傳統(tǒng)工藝條件下得到的制品多為非晶結(jié)構(gòu),導(dǎo)致其呈脆性大,耐熱性不佳,因此極大的限制了PLA的應(yīng)用。對于纖維增強的聚合物基復(fù)合材料,纖維改性是改善PLA結(jié)晶性能,提高制品結(jié)晶度的有效方法。本課題選天然蠶絲(SF)作為增強材料,利用碳酸鈉溶液對蠶繭脫膠,得到蠶絲纖維(絲素纖維),利用溶液法制備PLA薄膜,將單根蠶絲纖維放置于兩PLA薄膜之間,制成“三明治”結(jié)構(gòu)的試樣,研究了等溫溫度和牽引速率對SF/PLA界面結(jié)晶形貌的影響。首先,利用偏光顯微鏡(POM)研究了等溫過程中柱晶(或球晶)的結(jié)晶行為和晶體形貌,分析了等溫溫度、SF牽引速率以及牽引時間對晶體形貌的影響;其次,利用顯微紅外光譜(FTIR)對柱晶的晶體類型、結(jié)晶度及取向度進行了表征;最后,考察了小含量(5 wt%)的聚氧化乙烯(PEO)對PLA結(jié)晶行為的影響,主要內(nèi)容簡述如下:(1)等溫溫度在100-130℃之間,牽引速率為0時,SF表面無法誘導(dǎo)PLA結(jié)晶。溫度較低時(120℃),由于過冷度較大,PLA基體的成核很快,較小的球晶迅速充滿POM觀測區(qū)域,很難觀察SF對PLA結(jié)晶行為的影響,本實驗表明120-130℃是研究SF誘導(dǎo)PLA結(jié)晶行為的理想溫度區(qū)間。(2)利用POM研究了牽引速率對SF/PLA界面結(jié)晶行為的影響,發(fā)現(xiàn)牽引速率不同,PLA在SF表面上的結(jié)晶形貌不同。牽引速率較小時,SF表面上形成“串形球晶”結(jié)構(gòu),牽引速率增大,“串形球晶”轉(zhuǎn)變?yōu)橹ЫY(jié)構(gòu),牽引速率過大時,蠶絲纖維發(fā)生斷裂。無論是形成“串形球晶”還是柱晶,其結(jié)晶誘導(dǎo)時間都隨牽引速率的提高而縮短,成核速率、最終晶核密度則隨牽引速率的提高而增大。等溫溫度為120℃時,生成“串形球晶”的臨界牽引速率為5μm/s,形成柱晶的臨界牽引速率為40μm/s,蠶絲纖維在牽引過程中發(fā)生斷裂的牽引速率為150μm/s,而130℃條件下的三個臨界速率分別為10、50和250μm/s。相同牽引速率下,120℃等溫時,PLA的結(jié)晶誘導(dǎo)時間更短,成核速率更大,最終晶核密度更高。(3)以牽引時間為變量,固定牽引速率為40μm/s,研究牽引時間對界面結(jié)晶形貌的影響,發(fā)現(xiàn)牽引時間與牽引速率具有類似的效果,延長牽引時間,PLA在SF表面的結(jié)晶形貌由“串形球晶”變成柱晶結(jié)構(gòu),即成核密度隨牽引時間的延長而增加,與130℃相比,120℃條件下,PLA在SF表面的成核密度更高,成核速率更快。(4)利用FTIR分析牽引速率對PLA柱晶的晶型、結(jié)晶度和取向度的影響,發(fā)現(xiàn)牽引速率不能改變PLA的晶體類型,柱晶均為α晶體結(jié)構(gòu)。120℃條件下,隨著牽引速率提高,柱晶的結(jié)晶度提高,取向度增加。130℃條件下的實驗結(jié)果與120℃基本一致,不同之處在于,牽引速率超過臨界值時(100μm/s),柱晶的結(jié)晶度和取向度分別趨于固定值。(5)探究小含量的聚氧化乙烯(PEO)對SF/PLA復(fù)合體系結(jié)晶行為的影響,發(fā)現(xiàn)PEO加入后,開始在SF表面生成“串形球晶”和柱晶的臨界牽引速率均提高,此外,PEO還明顯提高了PLA的晶體生長速率。
[Abstract]:Polylactic acid (PLA) has good mechanical properties, biocompatibility and biodegradability, and is widely used in biomedical and packaging fields. Due to the slow crystallization rate of PLA, the products obtained under traditional process conditions are mostly amorphous structure, resulting in its brittleness and poor heat resistance, which greatly limits the application of PLA. Fiber modification is an effective method to improve the crystallinity and crystallinity of PLA. In this paper, natural silk (SF) was selected as reinforcing material, cocoon was degummed with sodium carbonate solution, and silk fiber (fibroin fiber) was obtained. PLA film was prepared by solution method, and single silk fiber was placed between two PLA films to make "SF" as reinforcing material. The effects of isothermal temperature and traction rate on the crystal morphology of SF/PLA interface were studied. First, the crystallization behavior and morphology of columnar (or spherulite) crystals were studied by polarizing microscope (POM), and the effects of isothermal temperature, SF traction rate and traction time on the crystal morphology were analyzed. Microscopic infrared spectroscopy (FTIR) was used to characterize the crystal type, crystallinity and orientation of the columnar crystals. Finally, the effect of polyethylene oxide (PEO) with small content (5 wt%) on the crystallization behavior of PLA was investigated. The main contents were summarized as follows: (1) SF surface could not induce the crystallization of PLA when the isothermal temperature was between 100 -130, and the traction rate was 0. It is difficult to observe the effect of SF on the crystallization behavior of PLA because of the large degree of undercooling and the rapid nucleation of PLA matrix and the small spherulite filling the POM observation region. The experiment shows that 120-130 C is the ideal temperature range for studying the crystallization behavior of PLA induced by SF. (2) The influence of the traction rate on the crystallization behavior of SF/PLA interface was studied by POM. When the traction rate is low, the "string spherulite" structure is formed on the SF surface, and the "string spherulite" is transformed into columnar structure. When the traction rate is too high, the silk fibers break down. Whether the "string spherulite" or columnar crystal is formed, the induction time of crystallization varies with the traction time. The critical traction rate for the formation of string spherulites is 5 micron/s, the critical traction rate for the formation of columnar crystals is 40 micron/s, and the traction rate for the breakage of silk fibers during traction is 150 micron/s and 130 micron/s respectively. At the same traction rate, the induction time of PLA crystallization is shorter, the nucleation rate is higher, and the final nucleation density is higher at 120 C. 3. The influence of traction time on the interfacial crystallization morphology is studied by taking the traction time as variable and the fixed traction rate as 40_ micron / s. The nucleation density of PLA on SF surface increased with the extension of traction time. Compared with 130 C, the nucleation density of PLA on SF surface was higher and the nucleation rate was faster at 120 C. (4) FTIR was used to analyze the effect of traction rate on PLA columnar crystal. It was found that the traction rate could not change the crystal type of PLA, and the columnar crystals were all alpha crystals. At 120 C, the crystallinity and orientation of columnar crystals increased with the increase of traction rate. The experimental results at 130 C were basically the same as those at 120 C. The difference was that the traction rate exceeded the critical value. The crystallinity and orientation of the columnar crystals tend to be fixed at 100 micron/s. (5) The effect of small content of polyethylene oxide (PEO) on the crystallization behavior of SF/PLA composite system was investigated. It was found that the critical traction rate of string spherulites and columnar crystals on SF surface increased with the addition of PEO. Rate.
【學(xué)位授予單位】：鄭州大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O633.14;O631.13
本文編號：2215637
[Abstract]:Polylactic acid (PLA) has good mechanical properties, biocompatibility and biodegradability, and is widely used in biomedical and packaging fields. Due to the slow crystallization rate of PLA, the products obtained under traditional process conditions are mostly amorphous structure, resulting in its brittleness and poor heat resistance, which greatly limits the application of PLA. Fiber modification is an effective method to improve the crystallinity and crystallinity of PLA. In this paper, natural silk (SF) was selected as reinforcing material, cocoon was degummed with sodium carbonate solution, and silk fiber (fibroin fiber) was obtained. PLA film was prepared by solution method, and single silk fiber was placed between two PLA films to make "SF" as reinforcing material. The effects of isothermal temperature and traction rate on the crystal morphology of SF/PLA interface were studied. First, the crystallization behavior and morphology of columnar (or spherulite) crystals were studied by polarizing microscope (POM), and the effects of isothermal temperature, SF traction rate and traction time on the crystal morphology were analyzed. Microscopic infrared spectroscopy (FTIR) was used to characterize the crystal type, crystallinity and orientation of the columnar crystals. Finally, the effect of polyethylene oxide (PEO) with small content (5 wt%) on the crystallization behavior of PLA was investigated. The main contents were summarized as follows: (1) SF surface could not induce the crystallization of PLA when the isothermal temperature was between 100 -130, and the traction rate was 0. It is difficult to observe the effect of SF on the crystallization behavior of PLA because of the large degree of undercooling and the rapid nucleation of PLA matrix and the small spherulite filling the POM observation region. The experiment shows that 120-130 C is the ideal temperature range for studying the crystallization behavior of PLA induced by SF. (2) The influence of the traction rate on the crystallization behavior of SF/PLA interface was studied by POM. When the traction rate is low, the "string spherulite" structure is formed on the SF surface, and the "string spherulite" is transformed into columnar structure. When the traction rate is too high, the silk fibers break down. Whether the "string spherulite" or columnar crystal is formed, the induction time of crystallization varies with the traction time. The critical traction rate for the formation of string spherulites is 5 micron/s, the critical traction rate for the formation of columnar crystals is 40 micron/s, and the traction rate for the breakage of silk fibers during traction is 150 micron/s and 130 micron/s respectively. At the same traction rate, the induction time of PLA crystallization is shorter, the nucleation rate is higher, and the final nucleation density is higher at 120 C. 3. The influence of traction time on the interfacial crystallization morphology is studied by taking the traction time as variable and the fixed traction rate as 40_ micron / s. The nucleation density of PLA on SF surface increased with the extension of traction time. Compared with 130 C, the nucleation density of PLA on SF surface was higher and the nucleation rate was faster at 120 C. (4) FTIR was used to analyze the effect of traction rate on PLA columnar crystal. It was found that the traction rate could not change the crystal type of PLA, and the columnar crystals were all alpha crystals. At 120 C, the crystallinity and orientation of columnar crystals increased with the increase of traction rate. The experimental results at 130 C were basically the same as those at 120 C. The difference was that the traction rate exceeded the critical value. The crystallinity and orientation of the columnar crystals tend to be fixed at 100 micron/s. (5) The effect of small content of polyethylene oxide (PEO) on the crystallization behavior of SF/PLA composite system was investigated. It was found that the critical traction rate of string spherulites and columnar crystals on SF surface increased with the addition of PEO. Rate.
【學(xué)位授予單位】：鄭州大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O633.14;O631.13
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