The Preparation And Properties Of PEEK/modified CaCO₃ Whiskers By SHPAEK Composites

Poly（ether ether ketone）（PEEK） is a kind of high performance polymers with outstanding mechanical property, remarkable electrical behavior, excellent thermal and chemical stability, which is widely used in military industry and civil engineering. With the widely application of PEEK, the drawback of this resin should not be ignored. Firstly, the cost issue limits its large-scale application. The price of engineering plastics is generally dozens of times that of universal plastics. Then the PEEK itself doesn’t show much advantage in some specificity, which can’t satisfy the rigorous demands in certain field. Hence much more attentions have been drawn on the research of its composites, in which proper fillers are applied for combining resin to obtain better performance. For example, graphite can endow PEEK composites with friction behavior, rare earth oxide can enhance the PEEK composites’ radiation shielding performance, while the addition of carbon fiber and whiskers improves the mechanical properties of the composites. Among them the whisker is a kind of highly oriented fiber of micro size with high strength and modulus, a low price additionally, which could be regarded as an ideal composites’ reinforcement.There are several problems in the preparation and processing of composites:The chemical composition and physical-chemical properties of fillers and matrix are different, how to make the fillers disperse into the matrix homogeneously with a strong interface adhesion strength is of both far-reaching significance and plenty of challenges.As for materials, the easiness for processing is a very significant standard. For example, PEEK usually starts to melt at a relatively high temperature of 340 °C and owns a fine flow when it comes to 370 °C. With the addition of carbon fibers and whiskers, the processing temperature needs to be improved further. Although, the viscosity of the composites still maintain at a high level which set a burden to the torque rheometer that not only hinder well-functioning manufacture but also shorten the lifetime of processing equipment. It seems like a good choice that adding modifying agent into composites which could reduce its melting viscosity at the processing temperature range. Therefore, hyperbranched polymers have captured increasing scientific attentions.Sulfonated hyperbranched polymers own a well-known highly branched three-dimensional structure. The hyperbranched structure can provide disentanglement among the molecule chains and promote their movement, giving rise to the decrease of polymers’ melting viscosity and the refining of its flowability during processing. Accordingly, together with the advantage of low manufacture cost, simple process craft and easy industrialization, hyperbranched polymer could be used as an effective viscosity regulator for PEEK based composites.Hence, we synthesized sulfonated hyperbranched polymer and used it to modify calcium carbonate whiskers. The FTIR spectrum demonstrated that the SHPAEK modifier had been grafted onto the surface of CaCO₃ whiskers successfully with an interaction between –SO3H and CaCO₃. Then together with PEEK, we prepared CaCO₃ whiskers/PEEK composites through melting blending.It could be seen that the modulus and strength of the composites with CaCO₃ whiskers were enhanced compared with the pure PEEK. At the same fillers content, the modulus and strength of the composites with modified CaCO₃ whiskers were higher than that of the composites with unmodified CaCO₃ whiskers. The SHPAEK modifier had the similar molecule structure with matrix resin and –SO3 groups existed interaction with CaCO₃ that made filler-matrix combine closely to each other.The addition of pure CaCO₃ whiskers into the composites caused a higher melting viscosity than pure PEEK. Whereas, composites containing SHPAEK displayed an anticipated decrease in viscosity at the same modifier and filler content. Such a situation was mainly attributed to the hyperbranched structure of SHPAEK because of the disentanglement among the molecule chains and a well dispersity of filler, which can also benefit the rheological behavior for avoiding aggregation and agglomeration.It seemed that the addition of whiskers restricted the mobility of polymer chains and slowed down the crystalline velocity. Composites with whiskers modified by SHPAEK appeared better performance on crystallization capacity referring to Xc values. However, the unique hyperbranched structure decreased the entanglement of polymer chains and accelerated the configuration and accumulation of molecular chains during crystal process.In conclusion, the CaCO₃/PEEK composites is a kind of high performance composites with outstanding mechanical property, excellent thermal stability, light weight and low cost. The novel modifier SHPAEK effectively improves the dispersion of CaCO₃ whiskers in the matrix resin and enhances the adhesion between two phases. It also decreases the melting viscosity of composites at the processing temperature range and increases the stability under a relatively high temperature at the same time, which are all conformed to our expectation.