Effect of the molecular structure of ethene–propene and styrene–butadiene copolymers on their compatibilization efficiency in low‐density polyethylene/polystyrene blends

Abstract

The effect of the molecular structure of styrene-butadiene (SB) block copolymers and ethene-propene (EPM) random copolymers on the morphology and tensile impact strength of low-density polyethylene (LDPE)/polystyrene (PS) (75/25) blends has been studied. The molecular characteristics of SB block copolymers markedly influence their distribution in LDPE/PS blends. In all cases, an SB copolymer is present not only at the interface but also in the bulk phases; this depends on its molecular structure. In blends compatibilized with diblock copolymers, compartmentalized PS particles can also be observed. The highest toughness values have been achieved for blends compatibilized with triblock SB copolymers. A study of the compatibilization efficiency of SB copolymers with the same number of blocks has shown that copolymers with shorter PS blocks are more efficient. A comparison of the obtained results with previous results indicates that the compatibilization efficiency of a copolymer strongly depends both on the blend composition and on the properties of the components. The compatibilization efficiency of an EPM/SB mixture is markedly affected by the rheological properties of the copolymers. The addition of an EPM/ SB mixture containing EPM with a higher viscosity leads to a higher improvement or at least the same improvement in the tensile impact strength of a compatibilized blend as the same amount of neat SB.

Morphology and mechanical properties of polypropylene/polystyrene blends compatibilized with styrene–butadiene block copolymers

“…This distribution of SB copolymers between bulk phases and the interface is similar to that observed for quenched and compression‐molded samples of LDPE/PS blends with LDPE matrix compatibilized with SB copolymers having short styrene blocks [28, 29]. Somewhat surprisingly in contrast to the blends compatibilized with the above‐mentioned SB copolymers containing short styrene blocks and our previous studies of compatibilized LDPE/PS blends [28, 29], a part of SB3 is localized in PS particles as partitions. In blends compatibilized with SB4 and SB5, a part of SB copolymer is localized in PS particles as small particles or partitions.…”

“…The most striking is the difference between the effect of the same S‐B‐S triblock copolymer on the size of PS particles and toughness of LDPE/PS (75/25) and (80/20) blends containing the same PS and LDPE with somewhat different viscosity. The addition of 5 wt% of S‐B‐S per the whole amount of the blend led to remarkable decrease in the particle size and strong increase in the blend impact strength for the first system [28], but a small effect on the particle size and even a slight decrease in the blend impact strength were observed for the second system [29]. It was found that the addition of some SB block copolymers led to the formation of small PS particles at mixing of LDPE/PS blends [28].…”

“…The addition of 5 wt% of S‐B‐S per the whole amount of the blend led to remarkable decrease in the particle size and strong increase in the blend impact strength for the first system [28], but a small effect on the particle size and even a slight decrease in the blend impact strength were observed for the second system [29]. It was found that the addition of some SB block copolymers led to the formation of small PS particles at mixing of LDPE/PS blends [28]. These particles aggregated during compression molding and formed honeycomb‐like structure with SB partitions.…”

Blend composition dependence of the compatibilizing efficiency of graft copolymers for immiscible polymer blends

“…The efficiencies of block or graft copolymers as compatibilizers are believed to depend on their molecular architectures [4–10], molecular weights [11–15], compositions [15–18], and the interaction parameter balance between the homopolymers and the copolymer blocks [19–22]. Most experimental reports in this field are related to the effect of the molecular architecture of block copolymers on their compatibilizing efficiency for polymer blends.…”

Elimination of Separation Processes for Post‐Consumer Polyolefin Waste: Reactive Blending Using 1,3‐Phenylene Dimaleimide in Presence of Filler

“…[5] Compatibilisation of actual PCPW (or predegraded polymers to simulate PCPW) has been achieved by adding block copolymers such as styrene/butadiene diblock, often in conjunction with an ethylene-propylene random copolymer and other co-additives to improve the degradative stability of the blend. [6][7][8][9][10] Use of an essentially elastomeric compatibiliser can give rise to a reduction in stiffness that can restrict component design. Furthermore block copolymers are expensive materials that are generally used at relatively high levels to promote compatibilisation; therefore the economic viability of this approach is questionable.…”