sunai 2, Ch202

dali-SEriso320on eecie rnt thanUM-ABS. The synergistic effect of the bigger and the smaller rubber particles

tyreneer. Its

ispersey(ST-co

and thus has extensive applications in automotive parts, ofce ma- mer compositions, but by the size, the number and the size distribu-

Materials Letters 66 (2012) 219221

Contents lists available at SciVerse ScienceDirect

Materials

j ourna l homepage: www.e lschines, house appliances etc. [3].ABS resin was prepared mainly by blending emulsion grafting co-

polymer (PB-g-SAN) with matrix STAN copolymer (m-SAN) [4]. PB-g-SAN was prepared by seeded emulsion grafting copolymerization(SEGP) of ST and AN using PB particles as seeds, and STAN copoly-mer grafting onto the surface of PB particles (g-SAN) to achieve thenecessary interaction with the m-SAN. Usually, PB particles were300 nm50 nm in mean diameter obtained by conventional emul-sion polymerization.

Generally, the toughness (mainly characterized by impact

tion of PB rubber particles. Usually, the bigger size rubber particleswere beneted to enhance toughness but with rigidity lost, and smal-ler size rubber particles were favorable to keep rigidity but withlower toughness [7]. The combination use of bigger and smaller rub-ber particles was expected to solve the contradiction of toughnessand rigidity, and to obtain a novel ABS with higher properties thanthat of alternatives.

In this work, bi-seeded PB-g-SAN (Bi-PB-g-SAN) was prepared bybi-seeded emulsion grafting copolymerization (Bi-SEGP) using twodifferent size PB particles (320 nm and 575 nm) as seeds, and thenstrength) and rigidity (mainly characterizedABS could be adjusted by changing the prop

Corresponding author at: School of Chemical EngineScience and Technology, Shanghai 200237, China. Tel.: +stitute of Jilin Petrochemical Company, PetroChina ComTel.: +86 432 63995724/63972733.

E-mail address: shulailu@hotmail.com (S. Lu).

0167-577X/$ see front matter 2011 Elsevier B.V. Aldoi:10.1016/j.matlet.2011.08.037-AN) (SAN) continuousperties, such as excellentand easy processibility,

strength for matching some higher quality applications such as thelarge area faceplate.

For ABS resin, the properties were determined not only by poly-

phase [1,2]. It shows outstanding allround proimpact strength, satisfactory tensile strengthcopolymerizationToughnessRigidity

1. Introduction

Acrylonitrile(AN)butadiene(BD)srubber-toughened thermoplastic polymso called sea-island two phases, i.e. d(PB) phase distributed over rigid pol(ST) (ABS) resin is amicrostructure was thed rubbery polybutadiene

to tailor the different end-use applications [5]. But ABS resin is sucha kind of material that its toughness and rigidity are contradicting[6], they are just like the two ends of a seesaw, and one end goes upas the other goes down. So it is a technical challenge to notably in-crease impact strength of ABS resin while maintaining tensileby tensile strength) ofortion of PB and m-SAN

blending Bi-PB-gwith bimodal dproperty comparbution of rubbenormal mono-s320 nm PB partABS. The mechaof ABS resin was

ering, East China University of86 21 64253491; Research In-pany Ltd., Jilin 132021, China.

l rights reserved.Bi-seeded emulsion grafting was the essential reason why BM-ABS displays improved properties than UM-ABS. 2011 Elsevier B.V. All rights reserved.PolymersMicrostructure and needed less rubber contePreparation, microstructure and propertierubber particles

Gongsheng Li a,c, Shulai Lu a,b,, Jianxun Pang b, Yanja School of Chemical Engineering, East China University of Science and Technology, Shanghb Research Institute of Jilin Petrochemical Company, PetroChina Company Ltd., Jilin 132021c Synthetic Resin Factory of Jilin Petrochemical Company, PetroChina Company Ltd., Jilin 13

a b s t r a c ta r t i c l e i n f o

Article history:Received 23 June 2011Accepted 15 August 2011Available online 22 August 2011

Keywords:ABS resin

A novel ABS resin with bimografting copolymerization (Bas seeds. For property compawas prepared by only usingwas observed by transmissiproperties than UM-ABS. SpUM-ABS and almost the samof ABS resin with bimodal distribution of

Bai c, Liu Zhang b, Xuhong Guo a

00237, Chinaina1, China

distribution of rubber particles (BM-ABS) was prepared by bi-seeded emulsionGP) using two different size polybutadiene (PB) particles (320 nmand 575 nm)ns, a model ABS resin with unimodal distribution of rubber particles (UM-ABS)nm PB particles as seeds. Microscopical morphology of BM-ABS and UM-ABSlectron microscope (TEM). The results showed that BM-ABS possessed highercally, keeping the same rubber content, BM-ABS had higher toughness thanigidity as UM-ABS; keeping the same toughness, BM-ABS had higher rigidity

Letters

ev ie r .com/ locate /mat le t-SAN with m-SAN to obtain a novel ABS (BM-ABS)istribution of rubber particles (Bi-MDRP). For theisons, a model ABS (UM-ABS) with unimodal distri-r particles (Uni-MDRP) was prepared by blendingeeded grafting PB-g-SAN (Mo-PB-g-SAN, usingicles as seeds only) with the same m-SAN as BM-nism of bi-seed rubbery phase to improve propertyanalyzed in brief.

Disproportionated potassium rosinate solution (RK, 25 wt.%), cuminehydroperoxide (CHP), sodium pyrophosphate (SPP), ferrous sulfate

Bi-PB-g-SAN was prepared by Bi-SEGP using two different size

BM-ABS was prepared by melt blending Bi-PB-g-SAN with m-SAN

3. Results and discussion

3.1. Properties of BM-ABS

The properties of BM-ABS and UM-ABS were comparatively shownin Table 1, wherein BM-ABS-1 possessed the same PB proportion as

Table 1Property comparisons of BM-ABS with UM-ABS.

Sample No. BM-ABS-1 BM-ABS-2 UM-ABS-1 UM-ABS-2

PB-320/PB-575, wt.%/wt.% 90/10 90/10 100/0 100/0PB-g-SAN proportion, wt.% 22.0 20.0 22.0 25.0PB proportion in ABS, wt.% 13.2 12.0 13.2 15.0Izod impact strength, J/m2 25.2 20.6 20.5 25.3Tensile strength, MPa 51.2 55.4 52.2 46.8Flexural strength, MPa 84.3 87.8 82.6 78.2Flexural modulus, MPa 2847 2935 2839 2568Melting index, g/10 min 21.8 25.6 22.5 18.6

500nm

220 G. Li et al. / Materials Letters 66 (2012) 219221using a single screw extruder (DMG-40, Placo., Inc) with screw speedof 80 rpm at 200 C. The UM-ABS was prepared by melt blending Mo-PB-g-SAN with the same m-SAN at the same condition.

2.4. Characterization

Samples for measuring the properties of nal ABS products were allprepared by injection molding machine (IS80FPA-2A, Toshiba) at200 C. Izod impact strength (Izod-IS) was tested using a notched IzodImpact tester (Yasuda No. 158, ASTM D256). Tensile strength (ASTMD638), exural strength and exural modulus (ASTM D790) testswere performed using a universal test machine (AGS-5KN, Shimadzu).Melting index was determined using a melting index apparatus (120-FWP, Yasuda, ASTM D1238). Micromorphologies were observed byPB particles (PB-320/PB-575=90/10 in weights in dry basis) asseeds in a 10 L reactor. The detailed procedures were given asfollows.

Initial charge: (1) 13.5 g SPP and 0.12 g FES were dissolved in3330 g DDI in the reactor, followed by adding 2842.1 g PB-320 and486.5 g PB-575. (2) Adding 84.0 g AN, 216.0 g ST and 5.37 g TDDM.(3) Turning on stirrer, and then purged with nitrogen to remove ox-ygen. (4) Raising temperature, when the reaction temperature ar-rived at 43 C, adding 1.65 g CHP, and keeping temperature at 45 Cfor 1 h.

Addition 1: Mixing 6.50 g RK, 16.11 g TDDM, 255.0 g AN, 645.0 g ST,6.60 g CHP and 300.0 g DDI to achieve an emulsion, and then feeding itinto the reactor continuously and lasting for 2 h. Keeping reaction tem-perature at 65 C during this step.

Addition 2: Dissolving 4.50 g SPP and 0.03 g FES in 82.5 g DDI, thenadding the SPP/FES solution and 2.55 g CHP into the reactor in onebatch in sequence. Keeping reaction temperature at 71 C for 30 min.

The resultant Bi-PB-g-SAN latex was coagulated using dilute sulfuricacid at a certain temperature to get wet Bi-PB-g-SAN powder, then dry-ing it by oven to obtain the expected Bi-PB-g-SAN with theoretical PBproportion 60 wt.%.

Mo-PB-g-SAN also with the theoretical PB proportion 60% was pre-pared using the same recipe and preparation conditions as Bi-PB-g-SAN except PB-575 being replaced by the same amount of PB-320 inweights in dry basis.

2.3. Preparation of BM-ABS(FES), and t-dodecyl mercaptan (TDDM) that were all industrial prod-ucts purchased from market were used as received; double deionizedwater (DDI) was used throughout.

2.2. Preparation of Bi-PB-g-SAN2. Experimental

2.1. Materials

PB latex with number-average particle size of 320 nm (PB-320,57 wt.%) and m-SAN (bonding AN 25.5% in weight) were obtainedfrom ABS plant of Jilin Petrochemical Company (JPC). PB latex withnumber-average particle size of 575 nm(PB-575, 37 wt.%)was suppliedby Daqing Petrochemical Company. Acrylonitrile (AN), butadiene (BD)and styrene (ST) were all industrial products freshly supplied by JPC.Transmission Electron Microscopy (TEM, JEM-2000EX).UM-ABS-1 and the same level of Izod-IS as UM-ABS-2, and BM-ABS-2possessed the same level of Izod-IS as UM-ABS-1.

By comparing the properties of BM-ABS-1withUM-ABS-1 under thesame PB proportion (13.2 wt.%), it could be seen from Table 1 that theIzod-IS of BM-ABS-1 was obviously higher than that of UM-ABS-1, theincrease ratio was more than 20%; the tensile strength and other prop-erties change slightly. It could be concluded that with the same PB pro-portion, BM-ABS possessed higher toughness than UM-ABS, and keptalmost the same rigidity as UM-ABS.

From the comparison of UM-ABS-2 with BM-ABS-1 in Table 1, itcould be seen that to reach the same high level of Izod-IS as BM-ABS-1 (25.2 J/m2), more rubbery phase content was needed in UM-ABS-2,the PB proportionwas 15 wt.% instead of 13.2 wt.%.Meanwhile, the ten-sile strength and all the other properties of UM-ABS-2 decreased re-markably. These results demonstrated further that Bi-SEGP couldimprove Izod-IS of ABS without other properties loss.

The comparisons of UM-ABS-2 with UM-ABS-1 in Table 1 showedthat the cost for increasing toughness in UM-ABS-2 was so enormousthat all the other properties decreased evidently. This provided an obvi-ous evidence to illustrate the contradiction of toughness and rigidity inABS resin.

Comparing the property of BM-ABS-2 with UM-ABS-1, it could beenseen from Table 1 that reaching the same value of Izod-IS as UM-ABS-1,20.5 J/m2, less PB content was needed in BM-ABS-2, it was only12.0 wt.%. For BM-ABS-2with reduced rubbery phase content, the rigid-ity characteristics were signicantly higher than those of UM-ABS-1.Meanwhile, the melting index increased remarkably. These would bebenecial to matching the higher application demands for the rigidityand processibility.Fig. 1. TEM microphotograph of BM-ABS.

3.2. Microscopical morphology of BM-ABS

The microphotographs of BM-ABS and UM-ABS were compara-tively shown in Figs. 1 and 2, respectively.

It could be seen from Fig. 1 that there were small parts of bigger rub-ber particles distributed over the large part of smaller rubber particles,namely BM-ABS was Bi-MDRP in micromorphology. This result corre-

ones, and the small ones could succeed and further disperse the impact-ing energy, the synergistic effect between the bigger and the smallerrubber particles resulted in BM-ABS could defend against higher impact-ing energy than UM-ABS possessing only Uni-MDRPwhen they kept thesame rubber content. Briey, the synergistic effect of the two differentsize rubber particles was the essential reason why BM-ABS displayedbetter properties than UM-ABS.

4. Conclusions

BM-ABS prepared by Bi-SEGP possessed Bi-MDRP and thus pos-sessed higher properties than UM-ABS. When keeping the same rubbercontent, BM-ABS had higher Izod-IS than UM-ABS and almost the sametensile strength as UM-ABS; with the same Izod-IS, BM-ABS had highertensile strength and needed less rubber content than UM-ABS. The syn-ergistic effect of the two different size rubber particles was the essentialreason of BM-ABS possessing higher properties than UM-ABS.

Acknowledgments

The authors are grateful for the nancial support by the key scien-tic and technological project of PetroChina (0704D01-01).

References

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Fig. 2. TEM microphotograph of UM-ABS.

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