Isotactic polypropylene/polymethylmethacrylate blends: Effects of addition of propylene-graft-methylmethacrylate copolymer

Abstract

ABSTRACT:A novel graft copolymer of unsaturated propylene with methyl methacrylate (uPP-g-PMMA) was added to binary blends of isotactic polypropylene (iPP) and atactic poly(methyl methacrylate) (aPMMA) with a view to using such a copolymer as a compatibilizer for iPP/aPMMA materials. Optical microscopy (OM), scanning electron microscopy, wide angle X-ray scattering (WAXS), and small angle X-ray scattering (SAXS) techniques showed that, contrary to expectation, the uPP-g-PMMA addition does not provide iPP/ aPMMA compatibilized materials, irrespective of composition. As a matter of fact the degree of dispersion of the minor component achieved following the addition of uPP-g-PMMA copolymer remained quite comparable to that exhibited by binary blends of iPP and aPMMA with no relevant evidence of adhesion or interconnection between the phases. On the other hand the crystalline texture was deeply modified by the copolymer presence. With increasing uPP-g-PMMA content (w/w) the iPP spherulites were found to become more open and coarse and the dimensions and number per unit area of the amorphous interspherulitic contact regions were found to increase. According to such OM results the copolymer uncrystallizable sequences were assumed to be mainly located in interfibrillar and interspherulitic amorphous contact regions. SAXS analysis demonstrated that the phase structure developed in the iPP/aPMMA/uPP-g-PMMA blends is characterized by values of the long period increasing linearly with increasing copolymer content (w/w). Assuming a two phase model for the iPP spherulite fibrillae, constituted of alternating parallel crystalline lamellae and amorphous layers, the lamellar structure of the iPP phase in the ternary blends is characterized by crystalline lamellar thickness (L c ) and an interlamellar amorphous layer (L a ) higher than that shown by plain iPP and L c and L a values both increased with increasing uPP-g-PMMA content (w/w). Such SAXS results have been accounted for by assuming that a cocrystallization phenomenon between propylenic sequences of the uPP-g-PMMA copolymer and iPP occurs. The development of the iPP lamellar structure in the iPP/aPMMA/uPP-g-PMMA blends was thus modeled hypothesizing that during such a cocrystallization process copolymer PMMA chains with comparatively lower molecular mass remain entrapped into the iPP interlamellar amorphous layer forming their own domains. Moreover, evidence of strong correlations between the crystallization process of the uPP-g-PMMA copolymer and the iPP crystallization process was shown also by differential scanning calorimetry and WAXS experiments.

On the Controversial Fitting of Susceptibility Curves of Ferromagnetic CuII Cubanes: Insights from Theoretical Calculations

“…For ternary blends containing crystalline components, the crystalline segments of the block copolymer can cocrystallize with their respective crystalline homopolymers 58. For PLLA/LDPE/PE‐ b ‐PLLA ternary blends, the PLLA and PE segments of the block copolymer were crystallizable and allowed cocrystallization with their corresponding homopolymer phase at the interface.…”

Reactive melt modification of polyethylene by ethyl acrylate/acrylic acid copolymers: rheology, morphology and thermal behavior

“…Due to low compatibility of polyolefins with other polar polymers, it is proven to use block or graft polymers as compatibilizer to enhance the interfacial adhesion and improve the properties [12][13][14]. The graft copolymers suggest advantages to enhance the interfacial adhesion by localizing at the interface and reducing interfacial tension in heterogeneous polymer blends [15]. There are a limited available numbers of reports concerning the poly (acrylate/methacrylate) grafted polyolefins for compatibilizing poly (acrylate/ methacrylate)/polyolefin blends [11].…”

Morphology, crystallization, and thermal behavior of isotactic polypropylene/polymethylmethacrylate blends: Effects of the addition of a graft copolymer of propylene with methylmethacrylate

“…A novel graft copolymer of unsaturated propylene with methylmethacrylate (uPP‐ g ‐PMMA) was added to binary blends of isotactic polypropylene (iPP) and atactic polymethylmethacrylate (aPMMA) to assess whether such a copolymer can be used for compatibilizing iPP/aPMMA materials. In previous work1 dealing with solution‐cast samples, it was shown that, contrary to expectation, the uPP‐ g ‐PMMA addition does not provide iPP/aPMMA compatibilized materials irrespective of composition, even though the crystalline texture of the iPP matrix was strongly modified. As a matter of fact, the degree of dispersion of the minor component achieved, following the addition of uPP‐g‐PMMA copolymer, remained comparable to that exhibited by binary blends of iPP and aPMMA with no relevant evidence of adhesion or interconnection between the phases.…”