Mica Reinforced PP

The presence of mineral reinforcements such as talc or mica, as foreign solid particles embedded into a polypropylene matrix, usually induces a nucleation effect. A signihcant increase in the crystalline content of the polymer is evidenced if compared with the neat polymer when processed at the same setup conditions that are necessary to ensure a good accommodation of the solid particles into the amorphous phase of the polymer in order to obtain a material with a good mechanical performance (27). The comparison between PP/mica and PP/talc composites in terms of their mechanical behavior under dynamic conditions in the solid state agrees with the morphological features derived from their chemical structures of both minerals (28). 

Silica (silicon dioxide) particles, synthetic or natural based, have commonly been used in various polymer systems. Silica has a low coefficient of thermal expansion and high stiffness, translating into increased modulus of the compounded polymer. However, silica filler particles are not flake or plate like as talc or mica particles are, and typically have low aspect ratios. This means that unless the particles are very small, a silica filler addition provides a relatively low surface area for contacting the polymer, and thus it reinforces the resin system less than platy fillers. Researchers have also noted that mica-filled PP, for instance, contains fewer voids than silica-filled PP, which helps explain the higher strengths of mica compounds at 20% filler loadings. This tendency to form voids or cavities increases as silica filler content increases [7-20, 7-21). 

Kaolin is used only in small quantities in PR The anisotropic particle geometry of wollastonite and mica reinforces the pol)uner. The latter is applied more extensively in USA and Canada due to the closer location of mining facilities. Barite-filled PP has excellent vibration damping properties due to the high density of this filler. Wood flour filled PP is occasionally applied in the automotive industry for the preparation of door panels. Water absorption of this filler creates problems in processing and application. The most important characteristics of mineral fillers are collected in Table 2. 

Interaction with the matrix (untreated calcium carbonate in PE decreases tensile strength but after phosphate modification tensile strength is increased glass beads may decrease or increase tensile strength depending on their interfacial adhesion mica and talc give a similar effect in PP polyamide fiber does not reinforce natural rubber because of its lack of interaction)... 

Strength [Nishiyama etal., 1990,1991] that can be further improved by addition of a TPE [Nishiyama and Nakakita, 1991]. PPS/PEST blends were also compatibilized by addition of a PPS-PEST copolymer [Suenaga and Ishikuwa, 1991]. The alloys could be reinforced with GE, talc, mica, wollastonite or clay [Gary, 1993]. 

In PP compoimds (which is the main use of mica in TP reinforcement), the mechanical and thermal properties are considerably enhanced by modifying the PP with a maleic anhydride compatibilizer, which improves adhesion. Test results suggest that the improvement continues with increasing amounts of maleic anhydride. 

Filler/reinforcement in PP ASTM standard None Kenaf Jute Talc CaCOj Glass Mica... 

All of the specimens exhibited the same or similar relative storage mod-uH at temperatures below Tg (10 °C). In the temperature range above Tg up to around 100 °C, specimens using mica exhibited a higher reinforcement effect. The relative storage modulus of the PPCN (PP+1001C8-Mt) using mica was twice that of MA2 at 80 °C. 

---