摘 要:針對(duì)超高分子量聚乙烯(UHMWPE)纖維熔點(diǎn)低、易蠕變的缺點(diǎn),以復(fù)合材料熱壓加工環(huán)境為測(cè)試條件,通過(guò)分析不同熱壓溫度和熱壓時(shí)間下的力學(xué)穩(wěn)定性能,研究UHMWPE纖維的耐高溫性能。采用差示掃描量熱儀、熱重分析儀、掃描電子顯微鏡、X射線衍射儀、紅外吸收光譜分析儀和力學(xué)性能測(cè)試儀等儀器設(shè)備,表征并分析了UHMWPE纖維的力學(xué)性能、熱穩(wěn)定性能和微觀結(jié)構(gòu)。結(jié)果表明:熱壓溫度及時(shí)間對(duì)UHMWPE纖維性能有著重要的影響。在150 ℃及以下熱壓處理時(shí),纖維力學(xué)性能隨著熱壓時(shí)間的增加而變化不大;在160 ℃及以上熱壓處理時(shí),長(zhǎng)時(shí)間的熱處理導(dǎo)致纖維力學(xué)性能下降明顯,在160 ℃處理40 s時(shí)絲束斷裂強(qiáng)力為153 N,強(qiáng)力損失為46.50%;當(dāng)熱壓溫度大于纖維熔點(diǎn)時(shí),纖維強(qiáng)力出現(xiàn)急速下降,在170 ℃熱壓處理10 s時(shí)強(qiáng)力下降到了121 N,強(qiáng)力損失達(dá)到了57.80%。研究結(jié)果可為UHMWPE纖維復(fù)合材料的加工及應(yīng)用提供參考。
關(guān)鍵詞:超高分子量聚乙烯纖維;熱穩(wěn)定性能;斷裂強(qiáng)力;斷裂伸長(zhǎng);高性能纖維
中圖分類號(hào):TS102.6
文獻(xiàn)標(biāo)志碼:A
文章編號(hào):1009-265X(2024)03-0053-08
收稿日期:20230817
網(wǎng)絡(luò)出版日期:20231025
作者簡(jiǎn)介:薛淑云(1980—),女,江蘇徐州人,工程師,主要從事為功能高分子材料方面的研究。
通信作者:葉偉,E-mail:yewei@ntu.edu.cn
超高分子量聚乙烯(UHMWPE)纖維具有低密度、高強(qiáng)度、耐低溫、耐紫外線輻射和耐化學(xué)腐蝕等良好的物理化學(xué)性能,以及突出的抗沖擊、抗切割等優(yōu)異的使用性能[1-2],是除碳纖維、芳綸等纖維材料之外又一種重要的可規(guī)?;a(chǎn)的高性能纖維材料[3]。UHMWPE纖維已經(jīng)廣泛應(yīng)用于防彈防機(jī)械傷害用品、纜繩和漁網(wǎng)等產(chǎn)品中[4-7]。UHMWPE纖維有著熔點(diǎn)低、易蠕變等缺陷,相對(duì)于芳綸和碳纖維, UHMWPE纖維的耐熱溫度更低[8-9]。然而一些高性能纖維增強(qiáng)復(fù)合材料在加工過(guò)程中需要進(jìn)行高溫?zé)釅簭?fù)合,這對(duì)UHMWPE纖維在高溫下的可加工性提出了要求。
國(guó)內(nèi)外圍繞UHMWPE纖維的熱穩(wěn)定性能開展了較多的研究,主要集中在3個(gè)方面:一是紡絲生產(chǎn)過(guò)程中的溫度對(duì)UHMWPE纖維成型后性能影響的研究,紡絲工藝中溫度基本控制在200~260 ℃之間[10-12];二是針對(duì)UHMWPE纖維復(fù)合制備工藝中溫度對(duì)復(fù)合材料性能影響的研究,其中短切纖維增強(qiáng)樹脂復(fù)合材料及多層織物復(fù)合方面的研究較多,在這些研究中溫度主要集中在145 ℃及以下[13-15];三是針對(duì)應(yīng)用環(huán)境中的溫度對(duì)于UHMWPE纖維性能影響研究,由于UHMWPE纖維的耐高溫性能較差,開展研究所涉及的溫度基本集中在纖維材料熔融溫度及以下[16-17]。這些研究對(duì)于分析UHMWPE纖維的熱力學(xué)性能具有重要的意義。最近幾年的研究顯示,UHMWPE纖維與熱塑性聚氨酯、聚氯乙烯等樹脂復(fù)合,制備出了重量輕、強(qiáng)度高的輕質(zhì)高強(qiáng)膜材[18-19]。但是在熱壓復(fù)合加工中UHMWPE纖維要承受短時(shí)間的高溫?zé)釅汗に?,這些工藝的加工環(huán)境溫度較高,達(dá)到或超過(guò)材料的熔點(diǎn),而對(duì)于熱加工工藝中的短暫高溫對(duì)纖維結(jié)構(gòu)及力學(xué)性能影響的研究未見報(bào)道。
為研究UHMWPE纖維在復(fù)合材料制備中的耐高溫性能,本文以復(fù)合材料熱壓加工環(huán)境為條件,利用成型溫度及成型時(shí)間的改變來(lái)考察UHMWPE纖維結(jié)構(gòu)、表面形貌及力學(xué)性能等在高溫中的變化趨勢(shì),確定了適用于UHMWPE纖維加工的溫度及時(shí)間范圍,為纖維材料復(fù)合加工工藝的確定提供參考。
1 實(shí) 驗(yàn)
1.1 材料與儀器
材料:UHMWPE纖維絲束(88.9 tex,江蘇鏘尼瑪新材料股份有限公司)。
儀器:NHG-500B 型熱熔黏合機(jī)(上海佳田制造有限公司); Rigaku Ultima IV型X射線衍射儀(日本理學(xué));JSM-6510 型掃描電子顯微鏡(日本電子公司);Nicolet iS5型傅里葉紅外光譜儀(美國(guó)賽默飛公司); Q250型熱重分析儀(美國(guó)TA公司);5969系列電子萬(wàn)能材料試驗(yàn)機(jī)(美國(guó)英斯特朗公司)。
1.2 樣品制備
選用88.9 tex的UHMWPE纖維絲束,采用熱熔黏合機(jī)對(duì)絲束進(jìn)行熱壓處理,熱壓工藝分別為:在130、140、150、160、165、170 ℃和180 ℃溫度下分別熱壓10 s,壓力為1.5 MPa,試樣編號(hào)分別為"130-10、140-10、150-10、160-10、165-10、170-10和180-10;在140、150、160 ℃和165 ℃下分別熱壓20、30、40、50 s和60 s,壓力為1. 5 MPa,試樣編號(hào)分別為140-20、140-30、140-40、140-50、140-60、150-20、150-30、150-40、150-50、150-60、160-20、160-30、160-40、160-50、160-60、165-20、165-30、165-40、165-50和165-60。
1.3 性能測(cè)試
纖維結(jié)構(gòu)測(cè)試(XRD):采用X射線衍射儀進(jìn)行物相分析,測(cè)試為Cu靶Ka射線(λ=0.15418 nm),管電壓為40 kV,管電流為200 mA,掃描范圍為"10°~50°,掃描速率為12 (°)min,步長(zhǎng)為0.02°。
形貌表征(SEM):采用掃描電子顯微鏡觀察活化前后纖維的表面形貌和微觀結(jié)構(gòu),放大倍數(shù)分別為500倍和1000倍,電壓為5 kV。
紅外光譜吸收測(cè)試:采用傅立葉紅外光譜儀測(cè)試?yán)w維紅外光譜吸收特征,室溫下對(duì)樣品進(jìn)行測(cè)試,掃描范圍600~4000 cm-1。
熱學(xué)性能測(cè)試:采用熱重分析儀進(jìn)行差示掃描量熱法(DSC)和微商熱重法(DTG)分析,其中:DSC測(cè)試氣氛為N2,溫度范圍30~200 ℃,升溫速率為10 ℃min;DTG 測(cè)試氣氛分別為空氣和N2,溫度范圍30~800 ℃,升溫速率為10 ℃min。
力學(xué)性能測(cè)試:采用電子萬(wàn)能材料試驗(yàn)機(jī),根據(jù)GBT 19975—2005《高強(qiáng)化纖長(zhǎng)絲拉伸性能試驗(yàn)方法》測(cè)試熱處理前后UHMWPE絲束斷裂強(qiáng)力。并按照以下公式進(jìn)行計(jì)算斷裂強(qiáng)力損失率:
r%=F1-F2F1×100,
式中:r為斷裂強(qiáng)力損失率,F(xiàn)1為原樣UHMWPE纖維絲束斷裂強(qiáng)力,F(xiàn)2為經(jīng)過(guò)熱壓處理后UHMWPE纖維絲束斷裂強(qiáng)力。
2 結(jié)果與討論
2.1 纖維熱性能分析
圖1和圖2分別為未經(jīng)過(guò)熱壓處理的UHMWPE纖維的DSC和TGA測(cè)試曲線。從圖1可以看出:UHMWPE纖維在127 ℃時(shí)熱流開始急速下降,在169 ℃后熱流開始趨于穩(wěn)定,可見纖維最高熔點(diǎn)為169 ℃。從圖2可以看出:在N2的氣氛中UHMWPE纖維在420 ℃時(shí)熱分解速度加快,在506.9 ℃時(shí)纖維完全分解;當(dāng)在空氣氣氛中進(jìn)行熱分解測(cè)試時(shí),由于有氧氣等氣體的存在,纖維在329 ℃就開始加快分解。
2.2 纖維表面形貌分析
圖3和圖4為UHMWPE 纖維及絲束經(jīng)過(guò)熱壓處理前后的表面形貌圖。從圖3可以看出:經(jīng)過(guò)160 ℃處理時(shí),纖維表面未發(fā)生明顯的變化,當(dāng)處理溫度上升到170 ℃及以上時(shí),纖維表面有熔融現(xiàn)象,導(dǎo)致纖維間的黏合。同時(shí),UHMWPE 纖維經(jīng)過(guò)170 ℃熱處理時(shí)紗線中纖維之間開始黏合并產(chǎn)生了卷曲,當(dāng)熱處理溫度升高到180 ℃時(shí),黏合和卷曲的現(xiàn)象更為嚴(yán)重。這是因?yàn)閁HMWPE 纖維的熔融溫度較低,當(dāng)熱加工溫度超過(guò)熔融溫度時(shí),極易對(duì)纖維造成損傷,從而影響纖維的形貌及使用性能。
2.3 纖維結(jié)構(gòu)分析
圖5為UHMWPE 纖維熱處理前后的XRD圖譜,在20.56°、21.78°和24.13°處出現(xiàn)的衍射峰為UHMWPE纖維的典型衍射峰[20]。從圖5(a)中可以看出:當(dāng)熱處理時(shí)間一定時(shí),隨著熱處理溫度的升高,XRD分析曲線中衍射峰的高度和寬度總體趨于變低和變寬,這是由于UHMWPE纖維材料耐高溫性能較差,在高溫中纖維內(nèi)部的結(jié)晶區(qū)容易遭到破壞,以及材料分子鏈的熱運(yùn)動(dòng)加劇導(dǎo)致了分子鏈的斷裂和分解[16]。圖5(b)中,當(dāng)熱處理溫度較高時(shí),熱處理時(shí)間的增加會(huì)破壞UHMWPE纖維的晶體結(jié)構(gòu)。
2.4 紅外吸收光譜分析
圖6為UHMWPE 纖維熱處理前后紅外吸收光譜圖。在715、733、1460、1473、2848 cm-1和2915 cm-1處出現(xiàn)了紅外吸收峰,部分文獻(xiàn)中分析了纖維的結(jié)晶度對(duì)UHMWPE 纖維紅外吸收峰的位置及強(qiáng)度的影響,結(jié)晶度的差異導(dǎo)致纖維材料的紅外吸收峰位移,因此纖維制備工藝的差異對(duì)UHMWPE纖維的紅外吸收峰有一定的影響[21-22]。其中在715 cm-1和733 cm-1處分別是纖維結(jié)晶區(qū)內(nèi)CH2的平面搖擺和面內(nèi)搖擺振動(dòng)吸收峰;在1460 cm-1和1473 cm-1 處是纖維結(jié)晶區(qū)內(nèi)CH2對(duì)稱變形振動(dòng)吸收峰;在2848 cm-1和2915 cm-1處是纖維結(jié)晶區(qū)內(nèi)CH2伸縮振動(dòng)吸收峰[23]。在經(jīng)過(guò)不同條件的熱處理后,UHMWPE 纖維內(nèi)部結(jié)晶結(jié)構(gòu)發(fā)生了一定程度的改變,因此不同試樣的紅外吸收峰強(qiáng)度也發(fā)生了變化。
2.5 力學(xué)性能分析
圖7為UHMWPE 纖維絲束經(jīng)過(guò)不同條件下熱處理后的斷裂強(qiáng)力變化曲線。從圖7(a)中可以看出:試樣分別在130、140、150、160 ℃和165 ℃溫度下處理10 s時(shí),UHMWPE 纖維絲束的斷裂強(qiáng)力變化不大,原樣強(qiáng)力為286 N,經(jīng)過(guò)165 ℃處理10 s后強(qiáng)力下降到262 N,強(qiáng)力損失為8.49%;當(dāng)熱處理溫度上升到170 ℃及以上時(shí),斷裂強(qiáng)力出現(xiàn)了急速下降,熱處理溫度為170 ℃時(shí)強(qiáng)力下降到了120 N,強(qiáng)力損失為57.80%;當(dāng)溫度上升到180 ℃時(shí)強(qiáng)力已經(jīng)降到了56.60 N,強(qiáng)力損失達(dá)到了80.20%。同時(shí),在圖4的絲束形貌圖中觀察到在170 ℃熱壓處理時(shí)絲束已經(jīng)開始了收縮卷曲,逐漸失去了使用性能,試樣UHMWPE纖維的最高熱熔溫度為169 ℃,因此熱加工溫度超過(guò)169 ℃時(shí)對(duì)纖維極易造成損傷,從而影響材料的各項(xiàng)性能。從圖7(b)中可以看出:在150 ℃及以下時(shí),隨著熱處理溫度的升高和處理時(shí)間的增加,絲束的斷裂強(qiáng)力變化小,纖維力學(xué)性能損傷??;在150 ℃溫度下處理50 s絲束強(qiáng)力反而有所上升,這可能是UHMWPE纖維在紡絲完成后還存在著部分結(jié)晶傾向,這些傾向往往都集中在結(jié)晶核的表面,當(dāng)UHMWPE纖維在經(jīng)受熱壓復(fù)合時(shí)纖維內(nèi)部晶核表面排列有序的鏈段向中心靠攏,促進(jìn)了這些分子的結(jié)晶,同時(shí)也會(huì)彌補(bǔ)部分有缺陷的晶體[17];當(dāng)熱處理溫度達(dá)到了"160 ℃"及以上時(shí),處理時(shí)間對(duì)于UHMWPE纖維絲束的力學(xué)性能影響較大,在160 ℃時(shí)熱處理時(shí)間超過(guò)30 s后纖維斷裂強(qiáng)力下降迅速,處理40 s時(shí)絲束斷裂強(qiáng)力為153 N,強(qiáng)力損失為46.50%;當(dāng)熱處理溫度為165 ℃,熱處理時(shí)間超過(guò)20 s后,纖維斷裂強(qiáng)力就開始了迅速下降,處理30 s時(shí)絲束強(qiáng)力為163 N,強(qiáng)力損失為43%??梢缘贸鰺崽幚頊囟群蜔崽幚頃r(shí)間對(duì)于UHMWPE纖維的斷裂強(qiáng)力損失都有著重要的影響作用。
圖8為UHMWPE 絲束經(jīng)過(guò)熱處理后的斷裂伸長(zhǎng)率變化曲線。圖8(a)中,當(dāng)熱處理溫度低于170 ℃,絲束的斷裂伸長(zhǎng)率維持在4%左右;當(dāng)熱處理溫度大于170 ℃,絲束的斷裂伸長(zhǎng)率急劇變大,由165 ℃時(shí)的3.88%上升到180 ℃時(shí)的6.73%。圖8(b)中當(dāng)熱處理溫度較低時(shí),絲束的斷裂伸長(zhǎng)率隨著處理時(shí)間的變化基本保持穩(wěn)定,熱處理溫度升高到160 ℃及以上時(shí),斷裂伸長(zhǎng)率隨著熱處理時(shí)間的增加而變大;在160 ℃下熱處理30 s后絲束斷裂伸長(zhǎng)率為3.71%,而處理60 s后就增加到了1320%;在165 ℃下處理20 s后絲束斷裂伸長(zhǎng)率為5.34%,而處理60 s后伸長(zhǎng)率達(dá)到了21.10%??梢缘贸霎?dāng)UHMWPE 絲束經(jīng)過(guò)熱處理時(shí),隨著熱處理溫度和時(shí)間的增加,斷裂強(qiáng)力降低,而斷裂伸長(zhǎng)率升高,這是熱處理過(guò)程中的高溫破壞了UHMWPE纖維的結(jié)晶區(qū)以及鏈段結(jié)構(gòu),影響了纖維的各項(xiàng)力學(xué)性能[16]。因此,UHMWPE纖維在熱加工工藝中需要考慮到溫度和時(shí)間的因素。
3 結(jié) 論
本文通過(guò)對(duì)UHMWPE纖維力學(xué)性能隨熱加工溫度和時(shí)間變化的分析,研究了熱壓溫度和熱壓時(shí)間對(duì)纖維結(jié)構(gòu)、表面形貌結(jié)構(gòu)、絲束力學(xué)性能等的影響,得到以下結(jié)論:
a)UHMWPE纖維的最高熔點(diǎn)為169 ℃;在超過(guò)纖維最高熔點(diǎn)的溫度進(jìn)行熱加工時(shí),即使在很短的時(shí)間內(nèi)都會(huì)導(dǎo)致纖維表面融化并使纖維間產(chǎn)生黏結(jié)卷曲現(xiàn)象。
b)在UHMWPE纖維的高熔點(diǎn)處及以上的溫度進(jìn)行加工時(shí),熱壓溫度及時(shí)間對(duì)纖維力學(xué)性能影響較大。在160 ℃處理40 s時(shí)強(qiáng)力損失了4650%,在165 ℃處理30 s時(shí)強(qiáng)力損失達(dá)到了43%;當(dāng)熱處理溫度上升到170 ℃及以上時(shí),斷裂強(qiáng)力出現(xiàn)了急速下降,在170 ℃處理10 s時(shí)強(qiáng)力損失了57.80%,在180 ℃處理10 s時(shí)強(qiáng)力損失達(dá)到了80.20%。
c)UHMWPE 纖維絲束經(jīng)過(guò)160 ℃及以上熱壓處理時(shí),隨著熱壓溫度和時(shí)間的增加,斷裂強(qiáng)力降低,而斷裂伸長(zhǎng)率升高。在165 ℃下處理20 s后絲束斷裂伸長(zhǎng)率為5.34%,而處理60 s后伸長(zhǎng)率達(dá)到了21.10%。
UHMWPE纖維對(duì)于加工環(huán)境中的溫度有著嚴(yán)格的要求,本文研究所探索的熱壓溫度及時(shí)間對(duì)于材料性能的影響為UHMWPE纖維在復(fù)合材料中的應(yīng)用提供了有效的參考。
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High-temperature resistance of ultra-high molecular weight polyethylene fibers
XUE Shuyun1, YE Wei2, WANG Zheng3, XIA Pingyuan4, GUAN Yongyin5
(1.Yangzhou Sparkle Industrial Co., Ltd., Yangzhou 225200, China; 2.National amp; Local Joint Engineering Research Center
of Technical Fiber Composites for Safety and Protection, Nantong University, Nantong 226019, China; 3.Institute of Defense
Engineering, Academy of Military Sciences, PLA, Beijing 100036, China; 4.Jiangsu Zhengdao OceanTechnology Co., Ltd.,
Nantong 226300, China; 5.Xinfengming Group Huzhou Zhongshi Technology Co., Ltd., Huzhou 313000, China)
Abstract:
Due to the unique structural characteristics of ultra-high molecular weight polyethylene (UHMWPE) fibers, fiber materials possess several excellent properties including lightweight, high strength, low temperature resistance, resistance to UV radiation, chemical corrosion resistance, high energy absorption, low dielectric constant, high electromagnetic wave transmittance, low friction coefficient, and outstanding performance in terms of impact resistance and cut resistance. The melting point of UHMWPE fibers"is higher than that of ordinary polyethylene fibers at 134 ℃. However, compared to other high-performance fibers such as aramid and carbon fibers, UHMWPE fibers have poor high-temperature resistance, which limits their application range. Currently, research on the thermal stability of UHMWPE fibers in both domestic and international contexts mainly focuses on fiber spinning, low-temperature composites, and application environments. These studies are of importance in analyzing the thermodynamic properties of UHMWPE fibers. Recent studies have shown that UHMWPE fibers can be composite with thermoplastic polyurethane, polyvinyl chloride, and other resins to produce lightweight and high-strength membrane materials. However, in the process of hot-pressing composite processing, UHMWPE fibers need to withstand short-term high-temperature and high-pressure conditions. The processing environment temperature in these processes is high, reaching or exceeding the melting point of the material. As for the impact of transient high temperature in the thermal processing process on fiber structure and mechanical properties, no research reports have been found.
In response to the shortcomings of low melting point and easy creep of UHMWPE fibers, the mechanical stability performance of UHMWPE fibers under different hot-pressing temperatures and times was studied under the testing conditions of composite material hot-pressing processing environment. Through instruments such as differential scanning calorimeter, thermogravimetric analyzer, scanning electron microscope, X-ray diffractometer, Fourier transform infrared spectrometer and mechanical performance tester, the thermal stability performance and microstructure of UHMWPE fibers were characterized and analyzed. The results showed that the hot-pressing temperature and time had a significant impact on the performance of UHMWPE fibers. Under hot-pressing treatment of 150 ℃ or below, the mechanical properties of UHMWPE fibers changed little with the increase of hot-pressing time; under hot-pressing treatment of 160 ℃ or above, the long-term heat treatment led to a significant decrease in the mechanical properties of UHMWPE fibers. When the yarns were treated at 160 ℃ for 40 s, the breaking strength was 153 N, and the strength loss was 46.50%. When the hot-pressing temperature was higher than the melting point of the fibers, their strength dropped rapidly. When they were treated at 170 ℃ for 10 s, the strength dropped to 121 N, and the strength loss reached 57.80%.
The research on the effects of molding temperature and molding time during the processing of UHMWPE fibers on fiber structure, surface morphology, and mechanical properties has clarified that the temperature and time during the composite processing have a significant impact on the performance of UHMWPE fibers. Suitable composite processing techniques can promote the application of UHMWPE fibers in various fields. The research findings provide necessary references for determining the composite processing technology of UHMWPE fiber materials.
Keywords:
UHMWPE fiber; thermal stability; breaking strength; elongation at break; high-performance fiber