陶友季,章自壽,麥堪成

(1.中山大學化學與化學化學工程學院//教育部聚合物基復合材料及功能材料重點實驗室,新型聚合物材料設計合成與應用廣東省高校重點實驗室,廣東廣州510275; 2.中國電器科學研究院工業(yè)產品環(huán)境適應性國家重點實驗室,廣東廣州510663)

PP/回收PET共混物的動態(tài)流變行為＊

陶友季1,2,章自壽1,麥堪成1

(1.中山大學化學與化學化學工程學院//教育部聚合物基復合材料及功能材料重點實驗室,新型聚合物材料設計合成與應用廣東省高校重點實驗室,廣東廣州510275; 2.中國電器科學研究院工業(yè)產品環(huán)境適應性國家重點實驗室,廣東廣州510663)

為了研究回收PET對PP流變行為的影響,用雙螺桿擠出機制備了PP/回收PET和增容PP/回收PET共混物,研究了回收PET用量、不同相容劑對PP/回收PET共混物的動態(tài)流變行為的影響。結果表明,PP/回收PET共混物的復數(shù)黏度隨回收PET含量增加而降低,具有明顯的剪切變稀特性。PP-g-MA提高回收PET復數(shù)黏度,但PP-g-G MA降低共混物的復數(shù)黏度,表明回收PET與PP-g-MA的化學作用較PP-g-G MA強。PP-g-MA提高PP/回收PET共混物的動態(tài)彈性模量,但PP-g-G MA使共混物的動態(tài)彈性模量和動態(tài)黏性模量降低。PP-g-MA加入使PP/回收PET共混物tanδ降低,但PP-g-MA用量過高,tanδ反而提高;PP-g-G MA使共混物的tanδ提高,歸結于相容劑的增容和增塑作用。

回收PET;聚丙烯;復數(shù)黏度;動態(tài)彈性模量;力學損耗

PET廣泛地用于吹料瓶,大量使用導致許多廢棄PET產生。由于PET為工程塑料,具有比聚烯烴高的強度和模量,用回收PET與聚烯烴共混可望提高聚烯烴的力學性能和降低成本,而且是廢棄PET回收利用的重要方法。然而,PET和PP作為結晶性聚合物,其熔點、熔體黏度不同。為得到良好性能的PP/回收PET共混物,回收PET對PP的加工特性和流變行為有待于研究。

PP/PET共混物流變行為已有研究。Hausnerova等[1-2]研究了未增容和PP-g-MA增容PP/PET共混物的穩(wěn)態(tài)流變和動態(tài)流變行為,觀察到共混物在不同溫度下剪切黏度受PET含量影響而呈現(xiàn)不同的流變行為。在265℃,剪切黏度隨PET含量增加而降低;在245℃,剪切黏度隨PET含量增加而提高,具有粒子填充體系的流變行為特征,PP-g-MA增容提高共混物的剪切黏度和黏彈性。Chiu等[3]也發(fā)現(xiàn)POE-g-MA增容可提高PP/PET共混物的剪切黏度,SEBS-g-MA和SEBS-g-G MA等增容提高PP/PET共混物的熔體黏度[4]。但Cheung等[5]發(fā)現(xiàn)相容劑Epolene E-43(馬來酸酐改性PP)使PP/PET共混物的剪切黏度降低,剪切變稀特性變得不明顯。

近幾年用回收PET制備高分子共混物已有研究[6-10]。雖然PP/回收PET共混物的力學性能與其加工特性有關,但PP/回收PET共混物的動態(tài)流變行為至今未見有報道。本文在PP/回收PET共混物結晶行為與熔融特性研究[11-13]基礎上,為深入了解PP/回收PET共混物的加工特性,本文研究了不同回收PET用量、相容劑及其含量等對PP/回收PET共混物的動態(tài)流變行為的影響。

1 實驗部分

1.1 樣品的制備

PP:牌號EPS30R,MFI=3.4 g/10 min(230℃,2.16 kg),新疆獨山子石化公司產品;r-PET為回收瓶料;PP-g-MA和PP-g-G MA為廣州鹿山化工材料有限公司產品,接枝率分別為1.0%和1.1%。原材料真空干燥后,SJSH-Z-35型雙螺桿擠出機制備共混物,Y-350型立式注塑機制備標準樣條。

1.2 流變性能測試

樣品的動態(tài)流變行為采用先進流變擴展系統(tǒng)(ARES)測試,采用平行板夾具,平行板間距為1 mm,測試溫度為260℃,頻率掃描采用從低頻到高頻的方式,頻率范圍200～0.08 rad·s-1,應變固定為5%。

2 結果與討論

2.1 動態(tài)復數(shù)黏度與組成的關系

圖1是未增容PP/回收PET共混物的動態(tài)復數(shù)黏度(η＊)與頻率(ω)的對數(shù)關系曲線。PP和PP/回收PET共混物的復數(shù)黏度都隨著剪切頻率增大而減少,具有明顯的剪切變稀特性?；厥誔ET的復數(shù)黏度明顯低于PP和PP/回收PET共混物,并且隨剪切頻率變化不大。PP/回收PET共混物的復數(shù)黏度隨回收PET含量增加而降低。但在低頻區(qū),回收PET加入使PP復數(shù)黏度提高,表明回收PET與PP分子鏈存在相互纏結作用。但在高頻區(qū), PP/回收PET共混物復數(shù)黏度低于PP,表明回收PET加入有利于PP熔體黏度降低。

圖1 PP/回收PET共混物的η＊與ω的對數(shù)關系曲線Fig.1 Relationship ofη＊withωfor PP/r-PET blends

為了研究相容劑對PP/回收PET共混物流變行為的影響,本文先研究相容劑/回收PET共混物的流變行為。圖2是回收PET與PP-g-MA、PP-g-G MA共混物的η＊-ω關系曲線?？梢?在低頻區(qū)PP-g-MA或PP-g-G MA加入提高回收PET復數(shù)黏度,尤其PP-g-MA;認為PP-g-MA與回收PET作用生成大分子接枝物PP-g-PET,提高了回收PET的復數(shù)黏度。但在高頻區(qū)相反,尤其PP-g-G MA。回收PET/PP-g-MA共混物出現(xiàn)轉變的頻率高于回收PET/PP-g-G MA共混物,也表明回收PET與PP-g-MA間的化學作用較PP-g-G MA的強[11-13]。

圖3是PP-g-MA和PP-g-G MA增容PP/回收PET共混物的η＊-ω關系曲線。不同用量PP-g-MA的加入對共混物復數(shù)黏度影響不大,但PP-g-G MA加入降低了共混物的復數(shù)黏度,且隨PP-g-G MA含量增加而降低。由圖4可見,當PP-g-MA的分量為2 phr時,共混物在各頻率下的復數(shù)黏度都提高,歸結于PP-g-MA與回收PET的化學作用生成大分子接枝物PP-g-PET的影響。PP-g-MA用量繼續(xù)增加,共混物的復數(shù)黏度下降,歸結于過多的PP-g-MA起到增塑作用。

圖4 增容PP/回收PET共混物在不同ω的η＊與PP-g-MA含量的關系曲線Fig.4 Relationship ofη＊with PP-g-MA content for P/r-PET blends compatibilized with PP-g-MA at differentω

圖5是具有相同回收PET/相容劑質量比的增容共混物的η＊-ω關系曲線。同樣可見,在低頻區(qū),PP-g-MA增容共混物具有高的復數(shù)黏度;在高頻區(qū),相反。而PP-g-G MA增容共混物復數(shù)黏度隨PP-g-G MA用量增加而降低。

圖5 在相同回收PET/相容劑下PP-g-MA(a)和PP-g-G MA(b)增容PP/回收PET共混物的η＊與ω的關系曲線Fig.5 Relationship ofη＊withωfor(a)PP-g-MA and (b)PP-g-G MA compatibilized PP/r-PET blendswith the same r-PET/compatibilizerweight ratios

2.2 動態(tài)模量與組成的關系

圖6是PP/回收PET共混物的動態(tài)彈性模量(G′)、動態(tài)黏性模量(G″)與ω關系曲線。共混物的G′高于PP和回收PET,但隨組成比變化不大,歸結于回收PET與PP分子鏈存在相互纏結作用[14]。回收PET增加,PP的G″降低,與回收PET的G″和熔體黏度低有關。

圖6 PP/回收PET共混物的G′、G″與ω關系曲線Fig.6 Relationship ofG′,G″withωfor PP/r-PET blends

圖7是PP-g-MA增容PP/回收PET共混物的G′、G″與ω關系曲線。加入PP-g-MA可提高低頻區(qū)的G′,但對高頻區(qū)G′無明顯影響。認為PP-g-MA與回收PET作用生成大分子接枝物PP-g-PET,增強界面黏結,導致G′提高[15-16]。表明回收PET加入可以提高PP的動態(tài)彈性模量。但在整個剪切頻率范圍內,PP-g-MA對G″基本無影響。

圖7 PP-g-MA增容PP/回收PET共混物的G′、G″與ω關系曲線Fig.7 Relationship ofG′,G″withωfor PP/r-PET 80/20 blends compatibilized with PP-g-MA.

圖8是PP-g-G MA增容PP/回收PET共混物的G′、G″與ω關系曲線。加入PP-g-G MA使w(PP/r-PET)/w(PP/r-G MA)為80/20的共混物的G′和G″降低,并且G′和G″隨PP-g-G MA含量增加而降低,這與PP-g-MA增容體系明顯不同。反映PP-g-G MA與r-PET的化學作用比PP-g-MA與r-PET的弱,G′和G″的降低歸結于PP-g-G MA的增塑作用。

圖8 PP-g-G MA增容PP/回收PET共混物的G′、G″與ω關系曲線Fig.8 Relationship ofG′,G″withωfor PP/r-PET 80/20 blends compatibilized with PP-g-G MA.

2.3 力學損耗與組成的關系

力學損耗tanδ=G″/G′的大小與大分子鏈段運動能力有關。圖9是共混物的tanδ與ω關系曲線?？梢?PP/回收PET共混物在低頻區(qū)的tanδ隨回收PET含量增加而減少,與共混物G′較高有關。PP-g-MA增容使PP/回收PET共混物低頻區(qū)tanδ降低,表明共混物中鏈段運動變得困難;但PP-g-MA用量過高,tanδ反而提高。這與PP-g-MA的化學增容和增塑雙重作用有關,增容降低tanδ,增塑提高tanδ。PP-g-G MA與回收PET化學反應相對較弱,PP-g-G MA加入使共混物的tanδ增加。

3 結 論

圖9 增容PP/回收PET(質量比為80/20)共混物的tanδ與ω關系曲線Fig.9 Relationship of tanδwithωfor (a)PP/r-PET 80/20 blends and their blends compatibilized with(b)PP-g-MA and(c)PP-g-G MA

(1)PP/回收PET共混物的復數(shù)黏度隨回收PET含量增加而降低,具有明顯的剪切變稀特性。(2)PP-g-MA提高回收PET復數(shù)黏度,但PP-g-G MA降低共混物的復數(shù)黏度,表明回收PET與PP-g-MA的化學作用較PP-g-G MA強。(3)PP-g-MA提高PP/回收PET共混物的動態(tài)彈性模量,但PP-g-G MA使共混物的動態(tài)彈性模量和動態(tài)黏性模量降低。(4)PP-g-MA加入使PP/回收PET共混物tanδ降低,但PP-g-MA用量過高,tanδ反而提高; PP-g-G MA使共混物的tanδ提高,歸結于相容劑的增容和增塑作用。

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Dynam ic Rheological Behaviours of Polypropylene/ Recycled Poly(ethylene terephthalate)Blends

TAO Youji1,2,ZHANG Zishou1,MA I Kancheng1
(1.Materials Science Institute,PCFM Lab,DSAPM Lab,School of Chemistry and Chemical Engineering,Sun Yat-sen University,Guangzhou 510275,China; 2.State Key Laboratory of EnvironmentalAdaptability for Industrial Products, China National Electric Apparatus Research Institute,Guangzhou 510663,China)

In order to investigate the effect of recycled PET(r-PET)on the dynamic rheological behaviour of PP,blends of PP/r-PET and compatibilized blends were prepared on a twin-screw extruder. Effects of compatibilizers and r-PET contents on the dynamic rheological behaviour of PP blendswere investigated.The results showed that the complex viscosity of PP/r-PET blends decreased with increasing the content of r-PET.Addition of PP-g-MA increases the complex viscosity of PET.However,addition of PP-g-G MA decreased the complex viscosity of PET.It indicated that chemical interaction of r-PET with PP-g-MA was higher than thatwith PP-g-G MA.Addition of PP-g-MA increased the dynamic elastic modulus of PP/r-PET blends.However,addition of PP-g-G MA decreased the dynamic elastic modulus and dynamic viscous modulus of PP/r-PET blends.Addition of PP-g-MA decreased the mechanical loss of PP/r-PET blends.However,the mechanical loss of PP/r-PET blends increased at high content of PP-g-MA.Addition of PP-g-G MA increased the mechanical loss of PP/r-PET blends.Itwas explained by the plasticization and compatibilization of PP-g-MA

recycled PET;polypropylene;complex viscosity;dynamic elastic modulus;mechanical loss

O631.2

A

0529-6579(2010)01-0062-05

2009-05-04

廣東省自然科學重點基金資助項目(06104925);廣東省科技計劃資助項目(2008A010500003);中國電器科學研究院工業(yè)產品環(huán)境適應性國家重點實驗室基金項目

陶友季(1981年生),男,博士;通訊作者:麥堪成;E-mail:ces mkc@mail.sysu.edu.cn