Vol. 33, No. 3, 91-100 (2020) DOI: http://dx.doi.org/10.7234/composres.2020.33.3.091 ISSN 2288-2103(Print), ISSN 2288-2111(Online) Review 폴리페닐렌설파이드 (PPS) 복합소재제조및응용 최민식 *, ** 이정록 * 류성우 ** 구본철 * Fabrication and Applications of Polyphenylene Sulfide (PPS) Composites: A Short Review Minsik Choi*, **, Jungrok Lee*, Seongwoo Ryu**, Bon-Cheol Ku* ABSTRACT: Polyphenylene sulfide (PPS) is a semi-crystalline engineering thermoplastic resin that has outstanding thermal stability, mechanical strength, inherent flame retardancy, chemical resistance, and electrical properties. Due to these outstanding properties, it is preferred as a matrix for composite materials. Many studies have been conducted to produce composites with carbon fibers and glass fibers to improve mechanical properties and provide functionality of PPS. In this review paper, we report a brief introduction to the fabrication and applications of PPS composites with carbon nanotubes, graphene, carbon fibers, and glass fibers. 초록 : 폴리페닐렌설파이드 (PPS) 는반결정성엔지니어링열가소성수지로뛰어난열안정성, 우수한기계적강도, 고유의난연성및내화학성, 전기적특성을갖고있다. 이러한우수한특성으로인해 PPS 는복합체의매트릭스로선호되고있다. PPS 의기계적물성을향상시키며기능성부여를위해탄소섬유나유리섬유와같은필러를이용한복합화연구가진행되어오고있다. 본총설논문에서는 PPS 와탄소나노튜브, 그래핀, 탄소섬유, 유리섬유등과의복합체제조및응용에대한연구를소개하고자한다. Key Words: 폴리페닐렌설파이드 (PPS), 기계적물성 (Mechanical properties), 전기전도도 (Electrical conductivity), 열전도도 (Thermal conductivity), 탄소나노튜브 (Carbon nanotube), 그래핀 (Graphene), 탄소섬유 (Carbon fiber), 유리섬유 (Glass fiber) 1. 서론 PPS는황과벤젠고리가순차적으로결합된반결정성열가소성엔지니어링플라스틱이다. PPS는 1973년 Phillips Petroleum사에서상업화생산이시작된수지로유리전이온도 (T g ) 는 85 o C이며, 용융온도는 (Tm) 는 280 o C인고내열성플라스틱이다. 대표적인물성은 Table 1과같이내화학성, 내용제성이우수하고높은치수안정성및난연성을 보인다 [1]. 또한, PPS 수지는연속사용가능한온도가 220 도일정도로내열분해성을가지고있으며공기중에서거의 500 o C까지는무게손실이거의나타나지않는고성능플라스틱이다 [2]. 이러한장점외에 PPS 수지는결정화속도가빠르며높은결정화도를갖고있어취성이크다는단점이있지만, 다양한필러와의친화력이좋아복합체를제조할경우단점을보완및더우수한물성을구현할수있다 [3,4]. Received 16 April 2020, received in revised from 14 May 2020, accepted 18 May 2020 * Carbon Composite Materials Research Center, Korea Institute of Science and Technology * Carbon Composite Materials Research Center, Institute of Advance Composite Materials, Korea Institute of Science and Technology, Corresponding author (E-mail: cnt@kist.re.kr) ** Department of Advanced Materials Science and Engineering, The University of Suwon
92 Minsik Choi, Jungrok Lee, Seongwoo Ryu, Bon-Cheol Ku Table 1. Physical properties of PPS Physical properties Values Density (r) 1.35 g cm -3 Melting temperature (T m ) 280 o C Dielectric strength 22-28 kv mm -1 Coefficient of thermal expansion ( 10-6 / o C) 51.6 (< T g ), 97.9 (> T g ) Thermal conductivity (k) 0.22 W (m K) -1 Electrical conductivity (S cm -1 ) 1.5 10-16 S cm -1 본총설에서는, 이러한장단점을가진 PPS 합성법과 PPS 를이용한복합소재제조및응용관련연구동향을소개하고자한다. 복합소재용필러로는탄소나노튜브및그래핀과같은탄소나노물질외에탄소섬유및유리섬유를활용한결과를소개하고자한다. 이들복합소재의경우주로기계적강도, 전기적특성, 열적특성을향상시키는것이가능함을보여주었다. 또한, PPS 복합소재를이용한응용으로는대표적으로난연재, 고방열복합재, 그리고연료전지용복합분리판을보고하고자한다. 2. 본론 2.1 PPS 수지중합연구 2.1.1 용액중합 PPS는 1888년 Friedel-Crafts 반응의부산물로써처음발견되었으나분자량이낮고황함량이많은문제가있었다 [5,6]. 이후 1948년 Macallum은황, 탄산나트륨및 p- dichlorobenzene(dcb) 을 275~300 o C의밀폐된용기에서용융반응시켜열안정성이좋은페닐렌설파이드형태의고분자를합성하였다 (Fig. 1). 이중합방법은많은열을방출하는발열반응으로온도조절이힘들다는단점이있었지만이연구결과가 Dow Chemical사에이전되어본격적인 PPS 상업생산이시작되었다 [7]. 이후다양한연구가진행되었으나현재가장공업적으로사용되는방법으로는미국의 Philips Petroleum 사에서 1973년개발한 DCB와 sodium sulfide를단량체로사용하여극성용매내에서 PPS를중합하는방법이다 [8] (Fig. 2). 이방법을통해중합된 PPS(Ryton ) 는백색의고운분말형태 Fig. 3. Other PPS polymerization 로얻어지며, 높은결정화도를나타내었다. 하지만합성된 PPS는거의대부분의용매에용해되지않고, 고온에서몇가지 aromatic, chlorinated aromatic 또는 heterocyclic compound 용매에서제한된정도로용해된다. 이방법은상대적으로저렴한단량체를이용하여간단한공정을통해 PPS를얻을수있다는장점이있지만, 중합물의용해도가낮아분자량은대략 15,000-20,000 ( 고유점도 0.16) 정도로낮았으며고분자량의 PPS를얻기힘들다는단점이존재한다. 위방법외에 PPS중합으로알려진반응들은 Fig. 3에나와있는 (a) S-S 결합절단에의한 diphenyl disulfide의중합 [9,10], (b) quinone 화합물을이용한 diphenyl disulfide의산화중합 [11], (c) cyclic disulfide oligomer 중합 [12] 및 cyclic phenylene sulfide를사용한중합 [13], 3,4-dichlorobenzenethiol 을이용한 hyperbranched PPS 중합 [14,15], methyl phenyl sulfoxide의산화중합법 [16,17] 등이있다. Fig. 1. PPS polymerization by Macallum Fig. 2. PPS polymerization by Phillips Petroleum Company 2.1.2 PPS 용융중합법용액중합의경우는 Fig. 2에서처럼다량의부산물 ( 금속염 ) 이생성된다. 이때생성되는금속염은생산효율을낮추며고분자에잔존할경우수지의전기전도도를상승시키며가공기기의부식을유발하는단점이있다 [18]. 이러한단점을극복하기위해기존의용액중합의단량체인 DCB
Fabrication and Applications of Polyphenylene Sulfide (PPS) Composites: A Short Review 93 국내에서는 SK케미칼외에도 LG 화학에서 PPS 중합에대한연구개발을진행하고있으며특히나섬유용 PPS 중합및복합화연구개발을진행하고있다 [23]. Fig. 4. PPS manufacturing method by melt polymerization 대신 p-diiodobenzene(dib) 를고체황과용융하여중합하는용융중합방식이연구개발되었다. 기본합성방법은 Fig. 4 와같으며이스트만코닥이 1987년특허출원 [19,20] 을한후 2000년대중반에현 SK케미칼이이방법을응용하여상업화에적용한기술이다. 이방법에서는먼저요오드화공정에의해아릴화합물을요오드와반응시켜디요오드아릴화합물을얻고, 고체황과중합반응시켜고분자량의폴리아릴레이트 PPS 수지를제조한다. 이때요오드는중합반응중에기체상태로발생하게되는데, 이것을회수하여다시요오드화공정에사용하게된다. 이방법으로제조한고분자는용액중합법에의해합성된고분자보다분자량이높아추가후공정이필요하지않다. 또한, 중합시용매를사용하지않아친환경적이며비용도낮은장점이있다. 하지만이러한장점에도불구하고중합후남은요오드가분자상태로잔류할경우부식성이있어가공기계에문제를야기할수있으며중합시사용한고체황으로인해고분자내에이황결합 (disulfide) 이남아열적성질을저하시킬수있는문제가남아있다 [21]. 이러한단점을극복하기위한방법이 SK 케미칼에의해개발되었는데주연구내용은중합촉매및열처리 (hrea-set) 기술에있다 [22]. 중합촉매로는주로벤조티아졸 (benzothiazole) 류화합물을사용하며중합촉매로는 1,3- diiodo-4-nitrobenzene과같은니트로화합물을사용하고있다. 2.1.3 기타고분자량 PPS제조법고분자량의 PPS 수지를얻기위한방법으로는크게다음과같이세가지방법이활용되고있다 [24]. 1) PPS수지를공기중에서가열산화시키는방법, 2) 중합시삼관능기이상의가교제를첨가하여중합하는방법, 3) 산화제또는라디칼발생제로처리하는방법등이대표적인방법이다. 1) 번방법은큐어링공정이라고도알려져있으며용융된고분자를공기중에서계속하여열처리하게되면용융물의색은검정색으로변하며겔화및고화가진행되고사슬연장및가교반응이일어난다. 이렇게큐어링된고분자는분자량이증가되고가교에의한용해도가감소하나용융점도가증가하여우수한기계적특성을나타내고압축및사출성형공정이용이해지는특성이있다 [25]. 2) 번방법의경우는중합후고분자의선형성이낮아강도가낮으며섬유형고분자로는적합하지않은문제가있다. 3) 번방법의경우는점도제어가어려운문제가있다. 따라서, 위의문제를갖지않는고용융점도를갖는고분자의개발이필요한상황이다. 2.1.4 상업화된 PPS 수지생산현황 상업화된 PPS의전세계생산능력은 Table 2와같으며총 14만톤이상으로추정된다. Chevron Phillips사의 Ryton사업부는 2015년 Solvay사에합병되었으며 Toray사는한국군산에공장을증설하여생산중이다. SK 케미칼은일본의 Teijin 과합작하여 2013년 INITZ를설립하였으나현재는 SK단독으로생산중인상황이다. 전세계적으로 PPS 생산은활발 Table 2. PPS resin manufacturer and trade name Company Trade name Total capacity etc. Solvay Tosoh Ryton Susteel > 10,000 ton/yr (2005) > 7,000 ton/yr (2005) DIC Corporation DIC-PPS 20,000 ton/yr Toray Torelina 20,000 ton/yr Fortron Industries LLC Initz (SK Chemicals) DSM NHU Engineering Plastics Fortron Ecotran > 19,000 ton/yr (2005) 10,000 ton/yr In 2015, Chevron Phillips Chemical acquired Ryton PPS business PPS production mainly used in automotive applications Production of PPS is expected to increase by 3,000 ton/yr through expansion in North America The company plans to invest in Gunsan plant in Korea by 2021 to increase PPS resin production Founded in 1992, a joint venture between Celanese and Kureha Founded in 2013, SK Chemical and Teijin are joint ventures Currently, SK chemicals produces PPS alone Xytron 15,000 ton/yr A joint venture between Royal DSM and NHU, founded in 2016
94 Minsik Choi, Jungrok Lee, Seongwoo Ryu, Bon-Cheol Ku 히이루어지고있으며특히중국시장이활발히성장하고있는상황이다. 2.2 PPS Composites 제조및물성 PPS는엔지니어링열가소성플라스틱으로복합소재개발을위한우수한후보물질이다. PPS의높은내열성및내화학성, 우수한전기적특성, 낮은독성및난연성과같은우수한특성으로인해복합체의매트릭스재료로써널리선호되고있다 [2]. 고분자복합소재를제조하는방법으로는크게 1) 용액혼합법, 2) 용융컴파운딩법 3) in-situ 중합법같은세가지방법이사용되고있다. 본총설에서는 PPS 복합소재를제조하는데있어필러로써탄소나노물질인탄소나노튜브 (CNT) 와그래핀, 탄소섬유및유리섬유를첨가하여제조한복합소재에대해간략히소개하고자한다. 2.2.1 PPS-CNT composites CNT는기계적강도및전기전도도등이우수한소재로많은응용가능성이연구되고있다 [26,27]. 탄소나노튜브를고분자와복합화하는데있어탄소나노튜브의분산성은물성에큰영향을끼친다. 이와관련하여, 폴리에틸렌 (PE) 와 PPS를각각 CNT와복합화하여전자기파차단성 (Electromagnetic shielding Fig. 5. Schematic of the fabrication of the s-cnt/pps composite. Reproduced with permission [29] Efficiency) 을비교한연구가보고된바있다. PPS는 CNT- CNT 네트워크구조의연결성을증가시켜분산문제를해결함으로써 PE/ 다중벽탄소나노튜브 (MWCNT) 복합체보다우수한특성을보였다. 뿐만아니라, PPS/MWCNT의복합점도또한균일한분산으로인해더욱증가하였다. PPS 의첨가로인해 CNT의분산이향상되어다양한물성이크게향상될수있음을알수있다 [28]. 전도성고분자복합체에서분리된전도성네트워크의형성은전자기파차폐성능을위해상당히중요하다. PPS 의낮은용융점도는전도성필러와 PPS 분자사슬사이에격렬한확산을이끌어분리된전도성네트워크를형성한다. 이와관련하여소결몰딩 (sinter molding) 을통해효율적으로 PPS/CNT 복합재료를제조한연구가있다 (Fig. 5). 소결몰딩은 PPS 도메인의계면사이에서 CNT의선택적분포를제어하고, 생성된 PPS/CNT 복합재료에서분리된전도성네트워크를용이하게구축하기위해이용되었다. 해당연구에서제조한 PPS/CNT 복합재료는 72.0 S/m의매우높은전기전도도및 49.6 db의 EMI 차폐효과를나타내는것을알수있다 [29](Fig. 6). 국내에서는 LG화학, 제일모직 ( 현롯데케미칼 ), 삼양사등의여러기업에서 PPS의복합화연구를진행하고있다. LG 화학은섬유용 PPS 내에 CNT를분산시켜섬유방사후용도개발연구를진행하고있다. 과거수년간 PPS 수지의제조기술에는한계가있어분자량이작고분자량분포가넓은 PPS 수지만생산되어섬유용으로사용하기에는적합하지않았다 [22]. 분자량이작은 PPS 수지는가교반응을유도하여분자량을높이고자하였으나, 가교반응의불균일로인한섬유물성의불균일, 가교반응뿐만아니라과도한산화에의한 PPS 분지쇄의약화및절단, 다량의겔발생등으로인해섬유방사시섬유의잦은절단을야기하여생산상의문제가되고있다. LG화학은보강재로 CNT를사용하 Fig. 6. (a) EMI SE as a function of frequency (X-band) for the s-cnt/pps and r-cnt/pps composites with various CNT contents (b) Comparison of EMI SE for our s-cnt/pps composite and the reported CNT/polymer composites. the segregated CNT/PPS composite (denoted as s-cnt/pps composite. the conventional CNT/PPS composite (denoted as r-cnt/pps composite). Reproduced with permission [29]
Fabrication and Applications of Polyphenylene Sulfide (PPS) Composites: A Short Review 95 여섬유방사시팩압상승은억제하되섬유강도가향상된 PPS 섬유를제조하였다 [23]. 2.2.2 PPS-Graphene Oxide(GO) composites 그래핀은독특한 2차원구조와높은전자이동도및양자효과등의특성으로인해고분자재료와복합화하기위한많은연구들이진행되어왔다 [30-33]. 그중최근대표적인논문을소개하면다음과같다. 서울대이종찬교수팀은산화그래핀 (Graphene oxide,go) 에나일론6를기능화하여 PPS와복합화한연구를보고하였다 (Fig. 7). 나일론6는 PPS와기계적으로블렌딩되는것으로알려진지방족폴리아미드로, PPS 매트릭스에 0.03 wt% 의 nylon 6 grafted GO(NGO) 를추가하면인장강도와파단 신율이각각 32%, 30% 증가하는것을확인할수있다. 이러한결과는주사전자현미경 (SEM) 및 energy-dispersive X-ray spectroscopy(edx) 맵핑분석을통해 PPS/NGO 나노복합체의파단된표면을관찰함으로써알수있듯이 PPS 매트릭스에잘분산된 NGO에기인한것이다 [34]. 그래핀층은일반적으로반데르발스힘으로인해쉽게자기응집되기때문에중합체매트릭스에잘분산되기어렵다. Fig. 8과같이 PPS는그래핀에기능화되거나그래핀과상호작용을함으로써그래핀의분산성을향상시킬수있다. 이렇게만들어진 PPS/expanded graphite(eg) 복합체는순수 PPS와비교하여 PPS 복합체의결정성이크게증가하여높은전도성 (1.17 S/m) 및기계적강도 (1.3 GPa) 을나타냈다 [35]. Fig. 7. Synthetic routes to (a) nylon 6 grafted graphene oxide (NGO) and (b) poly(phenylene sulfide)/nylon 6 grafted graphene oxide (PPS/ NGO) nanocomposite. Reproduced with permission [34] Fig. 8. The interaction between PPS and EG. Reproduced with permission [35]
96 Minsik Choi, Jungrok Lee, Seongwoo Ryu, Bon-Cheol Ku 2.2.3 PPS-CF Composites PPS의기계적강도및취성특성을보완하기위해탄소섬유를필러로써사용한연구들이보고된바있다 [36,37]. PPS/CF 복합재료는우수한물리적특성뿐만아니라가공성도우수하기때문에고성능엔지니어링재료로간주되고있다. 이러한우수한기계적특성을가진 PPS/CF 복합재료를제조하기위해서는섬유와매트릭스사이에우수한계면접착력을필요로한다. Fig. 9에서처럼 COOH로기능화된디클로벤젠 (DCA) 을 DCB와공중합체로합성한후탄소섬유와복합화할경우변형된 PPS의기능기는탄소섬유표면의사이징제와의상호작용으로상용화제 (compatibilizer) 의역할을하게되었으며, 이는마이크로기계적물성과계면접착력을향상시키는결과를보였다 [38]. 계면전단강도는순수한 PPS/CF 복합소재에비해 10% PPS- COOH (7.5)/PPS/CF 복합소재가 36% 향상되었다. Fig. 10에서는이러한 CF와 PPS의계면특성을개선하기위해 CNT를전기영동법을통해 CF 표면에코팅한연구결과가발표되었다. 그결과, 계면전단강도 (IFSS) 는 41.7% 개선되었으며, 전기전도성은 78% 증가하였다. 해당연구에서는계면처리를통해복합체의기계적특성을개선시킬수있는가능성이있음을입증했다 [39]. 2.2.4 PPS-GF Composites PPS의취성특성을보완하기위한필러로써탄소섬유와같이많이쓰이는유리섬유 (Glass fiber,gf) 는비교적저렴한가격과우수한열적, 기계적특성으로인해많이사용되고있는충진제이다 [40,41]. 그러나, PPS/GF 복합재료의기계적특성은 PPS와 GF사이의약한계면접착력으로인해제한되며, 이러한문제를해결하기위해 PPS에아민기능기를도입한연구가보고된바있다. 아민기의도입으로인해친수성및표면반응성을나타내어, 순수한 PPS보다 GF와더잘결합함을보였다. 그로인 Fig. 9. Schematic of compatibility effect of PPS-COOH in PPS/CF composites. Reproduced with permission [38] Fig. 11. Schematic of compatibility effect of PPS-NH 2 in PPS/GF composites. Reproduced with permission [42] Fig. 10. (a) Self-manufactured electrophoresis equipment and (b) schematic of the designed and fabricated electrophoresis system to provide continuous treatment to CFs. Reproduced with permission [39
Fabrication and Applications of Polyphenylene Sulfide (PPS) Composites: A Short Review 97 Table 3. Properties of PPS and its Reinforced Composites [44] Properties Branched PPS Neat PPS 40% GF-PPS Linear PPS Neat PPS 40% GF-PPS Density (g/cm 3 ) 1.3 1.67 1.35 1.66 Tensile strength (MPa) 67 121 85 196 Elongation at break (%) 1.6 1. 3 27 2.2 Flexural strength (MPa) 98 179 142 255 Flexural modulus (GPa) 3.8 11.9 3.9 13.2 Impact strength (kj/m 2 ) - - - - Notched 2.7 6.9 1.8 9.8 Unnotched 11 24.5 95.1 47.1 Rockwell hardness (R) 123 123 100 (M) Water adsorption (wt%) <0.02 <0.05 0.02 0.015 Volume resistivity 10-16 (Ω cm) 4.5 4.5 1.6 1.6 Dielectric constant (10 3 Hz) 3.2 3.8 3.6 4.6 해, 순수 PPS/GF와비교하여인장강도, 영률, 굽힘강도및충격강도가각각 12.8%, 9.4%, 4.1% 및 13.8% 증가하는것으로보고하고있다 [42]. 상업적으로 PPS와유리섬유복합화는많이연구개발되었으며대표적인물성은 Table 3과같다. 가지형 PPS 고분자와선형 PPS 고분자의유리섬유복합소재의경우선형고분자와의복합소재물성이가지형보다우수한것으로나타났다. 2.3 PPS Composites 응용 PPS 시장은자동차, 전기전자분야가가장많은분야이며화력발전등에사용되는필터백 (filter bag) 은가장성장률이높은분야중하나로예측된다. 이외에도우주항공, 코팅등에사용되어지고있다. 본총설에서는연료전지및배터리등에사용되는분리판, 난연제품, 방열소재분야에대해간단히소개하고자한다. Table 4. DOE targets for bipolar plates [45] Characteristic Units 2020 Targets Cost $/kw net 3 Plate weight Kg/kW net 0.4 Plate H 2 permeation coefficient Std cm 3 /(sec cm 2 Pa)@ 80 o C, 3 atm, 100% RH < 1.3 10-14 Corrosion ma/cm 2 < 1 Electrical conductivity S/cm >100 Areal specific resistance Ohm cm 2 <0.01 Flexural strength MPa >25 Forming elongation % 40 PPS를통해제조된복합재는필러의적절한조성에따라양극판의중요한핵심요소인전기전도도와굴곡강도의큰향상될수있음을보였으며, 상용화된배터리의분리판에비해낮은전류밀도및높은방적전력밀도에서높은에너지효율을보여유망한후보로입증되었다. 2.3.2 Flame retardant PPS는난연성테스트결과 UL-94 V0에해당하며 Heat release capacity(hrc) 는 164 Jg -1 K -1 ), 산소한계지수 (LOI) 는 44인고성능난연소재로알려져있다. 이는상업화된아라미드소재인 Nomex나 Kevlar보다도우수한난연성이다 (Fig. 12). 이러한우수한난연성으로인해엔진의압축기, 연소기및터빈등화재위험이있는분야에서주목받고있다 [53,54]. 이러한우수한난연성을테스트하기위해비행기엔진에주로사용되고있는열경화성 Epoxy 복합재와열가소성 PPS 복합재의화재에서기계적거동을비교분석한연구 2.3.1 Bipolar plate 분리판 (Bipolar plate) 은연료전지및배터리등에있어주요구성요소중하나이다. 이러한분리판은전기전도성, 우수한기계적안정성, 내식성및전기화학적내구성을가져야한다 [44,45] (Table 4). Table 4는 DOE의 2020년목표값을나타낸것이다. 분리판은흑연및금속과같은재료와의복합화를통해연구되고있었으나 [46-49], 아직까지양극판으로사용되기위한충분한전기전도도에도달하지못했다. 이러한문제를해결하고자높은내화학성, 우수한기계적특성, 치수안정성, 고온내성, 난연성및 200 o C 미만의온도에서많은용매에대한내성을갖고있는 PPS를분리판에사용하기위한연구들이있었다 [50-52]. Fig. 12. Oxygen limit index (LOI) and heat release capacity (HRC) of commercialized polymers
98 Minsik Choi, Jungrok Lee, Seongwoo Ryu, Bon-Cheol Ku 가있다 [55]. 화재노출이후 PPS 복합재는 Epoxy 복합재보다인장특성의감소속도가훨씬느리며, 강성과강도는 Epoxy 복합재보다각각 70, 116% 더높았다. 화재노출로인한열가소성매트릭스의용융및재응고는수지의미세구조및결정도를변화시킴으로써화재후수지의기계적특성에영향을미치게되어열경화성복합재인 epoxy 복합재보다높은잔류특성을유지시켜준다. 따라서, 화재위험이있는분야에서열경화성복합재를대체할수있음을보였다. 고분자복합소재제조에있어 PPS를이용한난연섬유제조연구가발표되었다. Poly PCT(Polycyclohexane-dimethanol terephthalate)(loi 21) 를피복성분 (Sheath) 으로사용하고난연성을갖는 PPS (LOI 35) 를핵심성분 (Core) 으로사용하여섬유를제조하였다. 충분한난연성을제공하기위해적절한양의인난연제가첨가되었고 15% 첨가될때 LOI는최고약 29였다. 첨가된 PPS로인해섬유의강도가증가하고고내열성을갖게되었다 [56]. 2.3.3 고방열복합소재현대사회에사용되고있는전자기기는경량화, 소형화, 다기능화가추구되고있다. 전자소자의고집적화가될수록사용함에있어많은열이발생하게되는데, 발생되는열은기기의성능을저하시킬뿐만아니라열화의원인이되고있어방출되는열을조절하는것은중요하다. 고성능플라스틱중 PPS는열전도도가타고분자보다우수하며상온에서 0.22 W m -1 K -1 를나타내어방열용복합소재로많이연구개발되고있다 [57]. 방열복합소재용필러로는일반적으로탄소섬유, 탄소나노튜브, 팽창흑연, 그라파이트나노플레이트 (GNP) 와같은탄소재료나질화붕소 (Boron nitride, BN) 등의고열전도성세라믹필러를이용하여제조하고있다. 고열전도성무기필러소재는열전도성은우수하지만접착력이부족하고, 고분자소재는접착력은우수하나열전도성은낮기때문에이러한문제를상호보완하고자복합화가시도되고있다 [58,59]. 고열전도성무기필러로는 BN을, 열전도성고분자로는 PPS를사용하여고방열의복합소재를제조한연구가보고되었다. 마이크로미터 BN/ 나노미터 BN(m-BN/n-BN) 의하이브리드필러의적절한첨가는연전도성계수, 유전상수, 유전손실탄젠트값및열안정성모두향상시켰다. 그러나너무많은양의첨가 (>30 vol%) 는오히려물성의저하를가져왔는데, 무기필러의입자크기및함량이고분자의결정화도에영향을끼치고고분자의경우결정상에서의열전달이상대적으로용이하기때문에이러한결정화도가증가함에따라열전도성계수가증가하게된다. 본연구에서는 PPS 수지에 60% 무게비까지 (m-bn/n-bn; 2:1 질량비 ) 필러를첨가하여 2.638 W m -1 K -1 까지 9배이상으로열전도도를향상시킬수있었다 [60]. 3. 결론 (PPS 복합소재의전망 ) 본총설논문에서는 PPS의특성및여러가지합성방법들, 그리고다양한복합체제조방법및응용에대해소개하였다. PPS는그자체의열적안정성, 내화학성, 난연성, 전기절연성등이매우우수하여복합소재에다양한활용가능성이있는수지이다. 이러한 PPS 수지에탄소섬유, 유리섬유외에탄소나노물질과같은필러를단독또는복합적으로사용함으로써기계적강도, 전기전도, 열전도도, 난연성등을향상시킨연구결과들을소개하였다. 이렇게제조된 PPS 복합재료는고강도경량복합소재응용분야뿐만아니라방열, 난연, 내화학성, 고전도성등의기능성복합소재로의응용이유망할것으로보여진다. 향후친환경저가 PPS 합성공정을이용한대량생산이이루어질경우시장의확대및응용범위가확장될것으로예측된다. 후 기 본연구는한국과학기술연구원 (KIST) 개방형연구사업 (ORP) 와과기정통부의재원으로연구재단의나노소재기술개발사업연구과제 (2016M3A7B4900120) 로수행된것이며지원에대해진심으로감사드립니다. REFERENCES 1. Ashok, S.R., Kailash, R.N., and Sandeep, A.W., Polyphenylene Sulfide (PPS): State of the Art and Applications, Reviews in Chemical Engineering, Vol. 29, No. 6, 2013, pp. 471-489. 2. Silvestre, C., Di Pace, E., Napolitano, R., Pirozzi, B., and Cesario, G., Crystallization, Morphology, and Thermal Behavior of Poly(p-phenylene sulfide), Journal of Polymer Science: Part B: Polymer Physics, Vol. 39, 2001, pp. 415-424. 3. Lhymn, C., and Bozolla, J., Friction and Wear of Fiber Reinforced pps Composites, Polymers for Advanced Technologies, Vol. 7, 1987, pp. 451-461. 4. Schoch, K.F. Jr., Chance, J.F., and Pfeiffer, K.E., Sulfur Trioxide-doped Poly(phenylene sulfide), Macromolecules, Vol. 18, 1985, pp. 2389-2394. 5. Friedel, C., and Crafts, J.M., On a New General Method of Synthesis of Aromatic Combinations (second dissertation), Annales de chimie et de physique, Vol. 14, 1888, pp. 433-472. 6. Genvresse, M.P., Bulletin de la Société Chimique de France, Vol. 3, No. 17, 1897, p. 599. 7. Macallum, A.D., A Dry Synthesis of Aromatic Sulfides; Phenylene Sulfide Resins, The Journal of Organic Chemistry, Vol. 13, 1948, pp. 154-159. 8. Edmonds Jr., J.T., and Hill Jr., H.W., U. S. Patent, 3,354,129, 1967. 9. Tsuchida, E., Yamamoto, K., Nishide, H., Yoshida, S., and Jikei, M., Polymerization of Diphenyl Disulfide by the S-S Bond Cleavage with a Lewis Acid: A Novel Preparation Route to
Fabrication and Applications of Polyphenylene Sulfide (PPS) Composites: A Short Review 99 Poly(p-phenylene sulfide), Macromolecules, Vol. 23, 1990, pp. 2101-2106. 10. Tsuchida, E., Yamamoto, K., Nishide, H., and Yoshida, S., Poly(p-phenylene sulfide)-yielding Polymerization of Diphenyl Disulfide by S-S Bond Cleavage with a Lewis Acid, Macromolecules, Vol. 20, 1987, pp. 2030-2031. 11. Tsuchida, E., Yamamoto, K., Jikei, M., and Nishide, H., Oxidative Polymerization of Diphenyl Disulfides with Quinones: Formation of Ultrapure Poly(p-phenylene sulfide)s, Macromolecules, Vol. 23, 1990, pp. 930-934. 12. Ding, Y., and Hay, A.S., Novel Synthesis of Poly(p-phenylene sulfide) from Cyclic Disulfide Oligomers, Macromolecules, Vol. 29, 1996, pp. 4811-4812. 13. Zimmerman, D.A., Koenig, J.L., and H. Ishida, Polymerization of Poly(p-phenylene sulfide) from a Cyclic Precursor, Polymer, Vol. 37, 1996, pp. 3111-3116. 14. Jikei, M., Hu, Z., Kakimoto, M., and Imai, Y., Synthesis of Hyperbranched Poly(phenylene sulfide) via a Poly(sulfonium cation) Precursor, Macromolecules, Vol. 29, 1996, pp. 1062-1064. 15. Mellace, A., Hanson, J.E., and Griepenburg, J., Hyperbranched Poly(phenylene sulfide) and Poly(phenylene sulfone), Chemistry of Materials, Vol. 17, 2005, pp. 1812-1817. 16. Tsuchida, E., Shouji, E., and Yamamoto, K., Synthesis of Highmolecular-weight Poly(phenylene sulfide) by Oxidative Polymerization via Poly(sulfonium cation) from Methyl Phenyl Sulfoxide, Macromolecules, Vol. 26, 1993, pp. 7144-7148. 17. Tsuchida, E., Suzuki, F., Shouji, E., and Yamamoto, K., Synthesis of Poly(phenylene sulfide) by O 2 Oxidative Polymerization of Methyl Phenyl Sulfide, Macromolecules, Vol. 27, 1994, pp. 1057-1060. 18. Lee, Y.R., Cha, I.H., and Cho, J.S., Manufacturing Prcess for Poly(arylene sulfide), KR Patent, 10-1183780, 2012. 19. Rule, M., David, R.F., Joseph, J.W., and Jerry, S.F., Copoly (Arylene Sulfidex-disulfide), US Patent, 4,786,713, 1988. 20. Rule, M., Donald, W.L., Thomas Jr., H.L., and Gerald, C.T., Processes for Preparing Iodinated Aromatic Compounds, US Petent, 4,746,758, 1988. 21. Shin, Y.J., Kim, S.G., Lim, J.B., Cho, J.S., and Cha, I.H., Process for Preparing Polyarylene Sulfide having Lower Content of Isolated Iodine, KR Patent, 10-1712273, 2017. 22. Lee, Y.R., Cha, I.H., Shin, Y.J., and Cho, J.S., Polyarylene Sulfide Resin with Excellent Luminosity and Preparation Method Thereof, US Patent, 8,957,182, 2015. 23. Gu, J.W., Du, J.J., Dang, J., Geng, W.C., Hu, S.H., and Zhang, Q.Y., Thermal Conductivities, Mechanical and Thermal Properties of Graphite Nanoplatelets/polyphenylene Sulfide Composites, RSC Advances, Vol. 4, 2014, pp. 22101-22105. 24. Kim, J.C., and Kim, Y.H., Development Status and Use of PPS Fiber, Fiber Technology and Industry, Vol. 11, No. 4, 2007, pp. 271-278. 25. Seymour, R.B., and Kirshenbaum, G.S. (Ed.), High Performance Polymers: Their Origin and Development, Elsevier Sci. Pub. Co., NY, 1986, pp. 135-148. 26. Sobia, I., Muhammad, S., Ayesha, K., Sedra, T.M., Jaweria, A., and Iram, B., A Review Featuring Fabrication, Properties and Applications of Carbon Nanotubes (CNTs) Reinforced Polymer and Epoxy Nanocomposites, Nature, Vol. 358, 1992, pp. 220-222. 27. Michele, T.B., and Yurii, K.G., Recent Advances in Research on Carbon Nanotube-Polymer Composites, Advanced Materials, Vol. 22, 2010, pp. 1672-1688. 28. Han, M.S., Lee, Y.K., Lee, H.S., Yun, C.H., and Kim, W.N., Electrical, Morphological and Rheological Properties of Carbon Nanotube Composites with Polyethylene and Poly(phenylene sulfide) by Melt Mixing, Chemical Engineering Science, Vol. 64, 2009, pp. 4649-4656. 29. Zhang, X.P., Jia, L.C., Zhang, G., Yan, D.X., and Li, Z.M., A Highly Efficient and Heat-resistant Electromagnetic Interference Shielding Carbon Nanotube-poly(phenylene sulfide) Composite via Sinter Molding, Journal of Materials Chemistry C, Vol. 6, 2018, pp. 10760. 30. Lee, J.H., Choi, K.D., Lee, S.H., and Kim, J.S., PPS Resin Composition and Method for Preparing PPS Fibers, KR Patent, 10-1584849, 2016. 31. Chae, B.J., Kim, D.H., Jeong, I.S., Hahn, J.R., and Ku, B.C., Electrical and Thermal Properties of Poly(p-phenylene sulfide) Reduced Graphite Oxide Nanocomposites, Carbon Letters, Vol. 13, No. 4, 2012, pp. 221-225. 32. Zhao, Y.F., Xiao, M., Wang, S.J., Ge, X.C., and Meng, Y.Z., Preparation and Properties of Electrically Conductive PPS/ expanded Graphite Nanocomposites, Composite Science and Technology, Vol. 67, 2007, pp. 2528-2534. 33. Park, O.K., Lee, S.H., Ku, B.C., and Lee, J.H., A Review of Graphene-based Polymer Nanocomposites, Polymer Science and Technology, Vol. 22, No. 5, 2011, pp. 467-473. 34. Jung, K.H., Kim, H.J., Kim, M.H., and Lee, J.C., Preparation of Poly(phenylene sulfide)/nylon 6 Grafted Graphene Oxide Nanocomposites with Enhanced Mechanical and Thermal Properties, Macromolecular Research, Vol. 28, 2020, pp. 241-248. 35. Zhang, M., Wang, H., Li, Z., and Cheng, B., Exfoliated Graphite as a Filler to Improve Poly(phenylene sulfide) Electrical Conductivity and Mechanical Properties, RSC Advances, Vol. 5, 2015, pp. 13840. 36. Zhang, K., Zhang, G., Liu, B., Wang, X., Long, S., and Yang, J., Effect of Aminated Polyphenylene Sulfide on the Mechanical Properties of Short Carbon Fiber Reinforced Polyphenylene Sulfide Composites, Composites Science and Technology, Vol. 98, 2014, pp. 57-63. 37. Durmaz, B.U., and Aytac, A., Characterization of Carbon Fiber-reinforced Poly(phenylene sulfide) Composites Prepared with Various Compatibilizers, Journal of Composite Materials, Vol. 54, No. 1, 2020, pp. 89-100. 38. Ren, H.H., Xu, D.X., Yan, G.M., Zhang, G., Wang, X.J., Long, S.R., and Yang, J., Effect of Carboxylic Polyphenylene Sulfide on the Micromechanical Properties of Polyphenylene Sulfide/ carbon Fiber Composites, Composites Science and Technology, Vol. 146, 2017, pp. 65-72. 39. Park, M., Park, J.H., Yang, B.J., Cho, J.H., Kim, S.Y., and Jung,
100 Minsik Choi, Jungrok Lee, Seongwoo Ryu, Bon-Cheol Ku I.H., Enhanced Interfacial, Electrical, and Flexural Properties of Polyphenylene Sulfide Composites Filled with Carbon Fibers Modified by Electrophoretic Surface Deposition of Multiwalled Carbon Nanotubes, Composites Part A, Vol. 109, 2018, pp. 124-130. 40. Zuo, P., Benevides, R.C., Laribi, M.A., Fitoussi, J., Shirinbayan, M., Bakir, F., and Tcharkhtchi, A., Multi-scale Analysis of the Effect of Loading Conditions on Monotonic and Fatigue Behavior of a Glass Fiber Reinforced Polyphenylene Sulfide (PPS) Composite, Composites Part B, Vol. 145, 2018, pp. 173-181. 41. Zhao, L., Yu, Y., Huang, H., Yin, X., Peng, J., Sun, J., Huang, L., Tang, Y., and Wang, L., High-performance Polyphenylene Sulfide Composites with Ultra-high Content of Glass Fiber Fabrics, Composites Part B, Vol. 174, 2019, pp. 106790 42. Ren, H.H., Xu, D.X., Yu, T., Yang, J.C., Zhang, G., Wang, X.J., and Yang, J., Effect of Polyphenylene Sulfide Containing Amino Unit on Thermal and Mechanical Properties of Polyphenylene Sulfide/glass Fiber Composites, Journal of Applied Polymer Science, Vol. 135, No. 6, 2018, pp. 45804. 43. Borzacchiello, A., Autiello, M.S., Russo, L., and Nicolais, L., Wiley Encyclopedia of Composites, John Wiley & Sons, Inc., 2012. 44. Haddadi-Asl, V., Kazacos, M., and Skyllas-Kazacos, M., Carbon-polymer Composite Electrodes for Redox Cells, Journal of Applied Polymer Science, Vol. 57, 1995, pp. 1455-1463. 45. Hassan, N.U., Tunaboylu, B., and Soydan, A.M., A Competitive Design and Material Consideration for Fabrication of Polymer Electrolyte Membrane Fuel Cell Bipolar Plates, Designs, Vol. 3, No. 1, 2019, pp. 13. 46. Song, L.N., Xiao, M., and Meng, Y.Z., Electrically Conductive Nanocomposites of Aromatic Polydisulfide/expanded Graphite, Composites Science and Technology, Vol. 66, 2006, pp. 2156-2162. 47. Dhakate, S.R., Sharma, S., Borah, M., Mathur, R.B., and Dhami, T.L., Development and Characterization of Expanded Graphite-based Nanocomposite as Bipolar Plate for Polymer Electrolyte Membrane Fuel Cells (PEMFCs), Energy & Fuels, Vol. 22, 2008, pp. 3329-3334. 48. Lee, J.H., Jang, Y.K., Hong, C.E., Kim, N.H., Li, P., and Lee, H.K., Effect of Carbon Fillers on Properties of Polymer Composite Bipolar Plates of Fuel Cells, Journal of Power Sources, Vol. 193, 2009, pp. 523-529. 49. Chunhui, S., Mu, P., and Runzhang, Y., The Effect of Particle Size Gradation of Conductive Fillers on the Conductivity and the Flexural Strength of Composite Bipolar Plate, International Journal of Hydrogen Energy, Vol. 33, 2008, pp. 1035-1039. 50. Caglar, B., Fischer, P., Kauranen, P., Karttunen, M., and Elsner, P., Development of Carbon Nanotube and Graphite Filled Polyphenylene Sulfide Based Bipolar Plates for All-vanadium Redox Flow Batteries, Journal of Power Sources, Vol. 256, 2014, pp. 88-95. 51. Kim, N.H., Kuila, T., Kim, K.M., Nah, S.H., and Lee, J.H., Material Selection Windows for Hybrid Carbons/poly(phenylene sulfide) Composite for Bipolar Plates of Fuel Cell, Polymer Testing, Vol. 31, No. 4, 2012, pp. 537-545. 52. Park, H.J., Woo, J.S., and Park, S.Y., Poly(phenylene sulfide)- graphite Composites for Bipolar Plates with Preferred Morphological Orientation, The Korean Journal of Chemical Engineering, Vol. 36, No. 12, 2019, pp. 2133-2142. 53. Muzzy, J.D., and Kays, A.O., Thermoplastic vs Thermosetting Structural Composites, Polymer Composites, Vol. 5, No. 3, 1984, pp. 169-72. 54. Sorathia, U., Beck, C., and Dapp, T., Residual Strength of Composites during and after Fire Exposure, Journal of Fire Sciences, Vol. 11, 1993, pp. 255-270. 55. Benoit, V., Cédric, L., and Alexis, C., Post Fire Behavior of Carbon Fibers Polyphenylene Sulfide- and Epoxy-based Laminates for Aeronautical Applications: A Comparative Study, Materials and design, Vol. 63, 2014, pp. 56-68. 56. Lim, J.C., Park, Y.W., and Kim, H.C., Study on Manufacturing PCT/PPS Flame Retardant Fiber by Sheath/Core Conjugate Spinning, Fibers and Polymers, Vol. 21, No. 3, 2020, pp. 498-504. 57. Park, S.Y., Kim, H.M., Kim, S.Y., and Youn, J.R., Synergistic Improvement of Thermal Conductivity of Thermoplastic Composites with Mixed Boron Nitride and Multi-walled Carbon Nanotube Fillers, Carbon, Vol. 50, 2012, pp. 4830-4838. 58. Pernot, G., Stoffel, M., Savic, I., Pezzoli, F., Chen, P., Savelli, G., Jacquot, A., Schumann, J., Denker, U., Mönch, I., Deneke, Ch., Schmidt, O.G., Rampnoux, J.M., Wang, S., Plissonnier, M., Rastelli, A., Dilhaire, S., and Mingo, N., Precise Control of Thermal Conductivity at the Nanoscale through Individual Phonon-scattering Barriers, Nature Materials, Vol. 9, 2010, pp. 491-495. 59. Shaikh, S., Lafdi, K., and Silverman, E., The Effect of a CNT Interface on the Thermal Resistance of Contacting Surfaces, Carbon, Vol. 45, No. 4, 2007, pp. 695-703. 60. Gu, J., Guo, Y., Yang, X., Liang, C., Geng, W., Tang, L., Li, N., and Zhang, Q., Synergistic Improvement of Thermal Conductivities of Polyphenylene Sulfide Composites Filled with Boron Nitride Hybrid Fillers, Composites: Part A, Vol. 95, 2017, pp. 267-273.