A new method for producing high melt strength polypropylene with reactive extrusion

Abstract

A high-melt-strength polypropylene (HMSPP) was prepared using a twin-screw reactive extruder from a commercial isotactic polypropylene through two stages, first, maleic anhydride is grafted to polypropylene to obtain a maleic anhydride-grafted polypropylene (PP-g-MA), and then the grafted polymer is reacted with epoxy to extend the branched chain. Fourier transformed infrared spectroscopy indicated that maleic anhydride was grafted on polypropylene and reacted with epoxy. Melt flow rate and sag resistance test showed that the melt strength of the HMSPP improved considerably. Differential scanning calorimetry test showed that the long chain branches (LCBs) act as a nucleating agent in the crystallization of the HMSPP, which leads to a high crystallization temperature and crystallinity. Furthermore, the LCB efficiency of the HMSPP can also be calculated by analyzing its rheological property.

Improving melt strength of polypropylene by minimal branching and blending

“…PPg is actually a commercial polymer in itself that has many applications, mainly as a coupling agent . The most frequently used functionalizing agent for synthesizing PPg is maleic anhydride (MA) . MA reacts with the macroradicals generated by an organic peroxide in a process that involves grafting of anhydride groups (AG) as well as transfer, scission and termination by disproportionation reactions.…”

Effect of fullerene C60 on the melt grafting reaction between multifunctional monomer and polypropylene

“…Commercial isotactic PP is not fit for the process where extensional flows are dominant, such as foaming, blowing, and extrusion coating, due to the absence of strain hardening. 8 Adding 1.2 wt % TMPTA, 0.1 wt % DHBP, and only 0.1 wt % C 60 (Sample 12T01C010D) could lead to formation of a small amount of long chain branched structure, and therefore, the sag did not influence the elongational tests. are presented in Figure 11.…”

Influence of different functionality degree grafting monomers on polypropylene melt radical branching reaction and their structure

“…Some researches proposed that a small quantity of long‐chain branches (LCBs) in PP could reinforce the MS obviously, which is owing to the augment of entanglements among the macromolecule chains . In addition, long‐chain–branched polypropylene (LCBPP) exhibits obviously strain hardening behavior in the MS .…”

“…Due to the inductive effect of methyl, the tertiary carbon atoms in PP own a great reactivity, which makes PP more vulnerable to be oxidized and thus then results in β ‐scission under the action of heat or high‐energy rays. Therefore, the method of melt radical branching reaction, as a simple and effective way, is widely applied to prepare LCBPP . Nonetheless, this reaction process must be controlled strictly because of the complexity of free radical reaction, which mainly included coupled reaction among PP chains and degradation caused by β ‐scission …”