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Itaconic acid (IA) was grafted onto polypropylene/low-density polyethylene (PP/LDPE) blends. The ratio of polymeric components was varied from 100 : 0 to 0 : 100. The effect of the variation in the ratios of the components on grafting efficiency and concomitant side processes was studied. Grafting of IA (1 wt %) was initiated by 2,5-dimethyl-2,5-di(tert-butyl peroxy)-hexane (0.3 wt %) and was carried out in an extruder reactor equipped with a dynamic mixer. An increase in the PP content of the blend led to a lower yield of the grafted product. With low concentrations of LDPE in the blend (up to 25 wt %), grafting efficiency was observed to increase, and this increase was greater in comparison with the additive rule. Between 25 and 99 wt % of LDPE in the blend, grafting efficiency rose monotonically with LDPE concentration. At or below an LDPE content of 25 wt %, the melt flow index (MFI) of [PP/LDPE]-g-IA would increase unlike with PP-g-IA systems. But a small quantity of PP (below 25 wt %) in the [PP/LDPE]-g-IA blends would result in a decreased MFI unlike with LDPE-g-IA. The dependence of swell index and melt strength on the ratio of polymeric components in [PP/LDPE]-g-IA blends also was investigated.

Static and dynamic mixers set on the Brabender plastograph were used to investigate the grafting of itaconic acid (IA) onto low-density polyethylene (LDPE) by the reactive extrusion. The initiators of free-radical reactions were monoperoxide 2,5-dimethyl-2-hydroxy-5-tert-butylperoxy-3-hexyne and diperoxide 2,5-dimethyl-2,5-di(tert-butyl peroxy)-hexane. The reaction mix contained stabilizers of phenolic type as follows: 2,6-ditertbutyl-4-methyl phenol; ester of 3,5-ditert-butyl-4-hydroxyphenyl-propanoic acid and pentaerythritol; 4-alkoxy-2-hydroxy-benzophenone; and 1,4-dihydroxybenzene. The effect of stabilizers, which follow the radical mechanism on the grafting of IA and on the crosslinking, depends on their solubility in the polymer and the monomer. The stabilizers (e.g., 1,4-dihydroxybenzene) with increased affinity toward the monomer reduce the grafting yield and inhibit crosslinking. At 0.3-0.5 wt % of the stabilizer insoluble in the monomer, the grafting yield can be increased, while inhibiting the LDPE-g-IA crosslinking, irrespective of the peroxide used. Hence, classical stabilizers can initiate grafting reactions at raised concentrations, temperatures, and application of the shearing stresses. They also help to obtain a high-grafting yield and a reduced crosslinking degree. A stabilizer, having a close affinity toward LDPE, influences the LDPE-g-IA structure. The stabilizer content of 0.5 wt % transforms the topological structure of LDPE-g-IA into uniblock. Its molecular weight distribution (MWD) may be narrow (M n /M w Ͻ 2) or broad (M n /M w Ͼ 2), depending on the concentration of the initiator used.

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