Because of their excellent mechanical strength and good electrical and thermal properties [
1,
2,
3], carbon nanomaterials such as carbon black, carbon nanotubes, and graphene have been intensely investigated with respect to industrial applications in aircraft and vehicles [
4,
5,
6,
7,
8,
9,
10]. Among these materials, graphene is often used as a filler in composites to improve both electromagnetic interference (EMI) shielding and the mechanical, electrical, and thermal properties. Graphene is a plate-like two-dimensional (2D) material with nanoscale thickness and microscale width. Because of its high aspect ratio, using it as a filler can create electrical and thermal networks [
11]. Based on these properties, graphene-polymer composites have been prepared for various applications, such as conductive composite films or heating units [
7,
8]. In addition, 2D graphene networks in polymer composites can efficiently prevent un-wanted electromagnetic waves and are therefore promising as next-generation EMI shielding materials.
However, carbon-based nanomaterials are easily aggregated because of the strong Van der Waals forces that bind them. To fabricate the ideal graphene composite, a uniform dispersion method is required to distribute the filler homogenously in the polymer matrix. The conventional method used is the ultra-sonication technique [
12,
13,
14,
15,
16,
17,
18], where the filler is dispersed by ultrasonic waves. However, over time, the dispersed fillers seem to re-aggregate because of the attractive forces between them. To solve this problem, dispersants are used to stabilize dispersions; however, the dispersant causes deterioration of the electrical properties of the composite by damaging the filler surface. In addition, when the viscosity of the solution containing the fillers increases, the sonication method does not work. Therefore, other dispersion methods have been developed, such as the three-roll milling method, which uses mechanical forces [
1,
19]. This method does not require the use of a solvent and dispersant. Three-roll milling enables the homogenous dispersion of high contents of filler, regardless of viscosity. Therefore, well-dispersed composites can be prepared that can be suitable for many applications, such as heating units, micro-patterning heaters, flexible EMI shielding materials, and de-icing systems [
20,
21,
22].
Conductive polymer composites offer some merits as EMI shielding materials. These include the low weight of the materials, corrosion resistance, and flexibility [
23,
24,
25,
26,
27]. The flexibility of the composite is maintained by polymers such as epoxy and silicone elastomers. Carbon nanomaterials show excellent EMI shielding performances [
28,
29,
30]; among carbon fillers, graphene has been extensively studied as a shielding material because of its unique 2D structure. Furthermore, these fillers have chemical stability and high conductivity, with a high aspect ratio.
Table 1 shows the EMI shielding properties of graphene composites with various polymers. In previous works, graphene composites have been shown to have high EMI shielding effectiveness (SE) and flexibility [
20,
24,
31,
32,
33]. For example, the EMI SE values of graphene-based composites with various polymers such as epoxy, polyetherimide (PEI), polymethylmethacrylate (PMMA), and polyurethane (PU) were 21 dB, 44 dB, 25 dB, and 16 dB, respectively [
23,
25,
26,
27]. Furthermore, a graphene polyvinylidene fluoride (PVDF) composite containing 7 wt% graphene showed EMI SE values of 20 dB in the 1–8 GHz frequency range and 25 dB in the 8–12 GHz range [
24]. Moreover, a flexible graphene thin film had an SE of 20 dB at frequencies of 8–12 GHz [
31]. Furthermore, graphene composites have superior EMI shielding properties compared with those of metal composites [
26,
33,
34]. Carbon nanomaterial-based heating units have been developed by many researchers [
35,
36,
37,
38]. These heaters can be heated efficiently by Joule heating. Electric Joule heating is facilitated by phonons colliding with electrons from an applied electric field [
39,
40,
41], as a result of which an electro-thermal response is generated. Conductive composites containing fillers such as carbon nanotube (CNT) and graphene are particularly efficient for this process because of their high electrical conductivities. Among these composites, graphene composite-based heating units have been extensively studied [
41,
42]. With respect to the selection of the polymer, a conductive composite can be made suitable for flexible heating units by exploiting the flexibility of the polymer matrix. At the same time, the rate of heating of the composite is high because of the outstanding electrical and thermal conductivity of graphene [
43]. Graphene composites are used in various applications, such as curved heaters, patterned heaters, and de-icing units, because of their flexibility and rapid heating capability [
22,
41].
In this paper, we describe the fabrication of graphene polydimethylsiloxane (G-PDMS) composite films using a three-roll mill process. We measured the electrical properties of the composites while varying the filler content. Furthermore, EMI shielding and electrical heating performances were evaluated. We confirmed the possibility of application of the composites for EMI shielding and de-icing units, based on these properties. The composite shows outstanding EMI shielding and de-icing performance as a result of the homogeneous distribution of the filler. Thus, we show that graphene composite films can be applied in electric vehicles and in the aviation industry, where both EMI shielding and de-icing properties are simultaneously required.