Partially crystalline copolymers

Practical interest in high-molecular-weight poly (propylene oxide) centers in its potential use as an elastomer (19). Copolymerization of propylene oxide with allyl glycidyl ether gives a copolymer with double bonds suitable for sulfur vulcanization. Table IV shows the properties of elastomers made with a copolymer prepared with a zinc hexacyano-ferrate-acetone-zinc chloride complex. Also shown are the properties of elastomers made from partially crystalline copolymers prepared with zinc diethyl-water catalyst. Of particular interest are the lower room-... 

Keywords Partially crystalline copolymers Structure and morphology via SANS ... 

In most ionomers, it is customary to fully convert to the metal salt form but, in some instances, particularly for ionomers based on a partially crystalline homopolymer, a partial degree of conversion may provide the best mechanical properties. For example, as shown in Fig. 4, a significant increase in modulus occurs with increasing percent conversion for both Na and Ca salts of a poly(-ethylene-co-methacrylic acid) ionomer and in both cases, at a partial conversion of 30-50%, a maximum value, some 5-6 times higher than that of the acid copolymer, is obtained and this is followed by a subsequent decrease in the property [12]. The tensile strength of these ionomers also increases significantly with increasing conversion but values tend to level off at about 60% conversion. 

For partially crystalline ionomers, such as those based on copolymers of ethylene and methacrylic acid, even time or aging at room temperature can have an effect on mechanical properties. For example, upon aging at 23°C, the modulus of the acid form of the copolymer increased 28%, while in the ionomer form, the increase ranged up to 130%, with the specific gain in modulus depending on the degree of conversion and on the counterion that was present [17]. 

In a partially crystalline homopolymer, nylon 6, property enhancement has been achieved by blending with a poly(ethylene-co-acrylic acid) or its salt form ionomer [24]. Both additives proved to be effective impact modifiers for nylon 6. For the blends of the acid copolymer with nylon 6, maximum impact performance was obtained by addition of about 10 wt% of the modifier and the impact strength was further enhanced by increasing the acrylic acid content from 3.5 to 6%. However, blends prepared using the salt form ionomer (Sur-lyn 9950-Zn salt) instead of the acid, led to the highest impact strength, with the least reduction in tensile... 

Block copolymers consisting of a smectic SCLCP-block and a partially crystalline apolar block were synthesized via ROMP of IV-n with cyclooctene and initiator 1 or 2 [63]. The block copolymers also formed smectic liquid crystalline mesophases and showed lamellar phase-separation. 

Partially crystalline behavior at low temperature (endothermic melting peaks in DSC at approximate -50 °C) is observed for weakly crosslinked siloxane particles and the corresponding graft copolymers. 

Furthermore, monomers from which crystalline homopolymer can be produced, such as high-density polyethylene and polypropylene, can be copolymerized to produce resins with controllably reduced crystallinity and thus greater transparency. The ethylene/propylene copolymers may range from partially crystalline plastics to amorphous elastomers. 

Thus, each individual phase i contributes to the birefringence according to its volume fraction (f>i and birefringence Am. These different phases can, for example, be the amorphous and crystalline phases of partially crystalline polymers, aggregates in block copolymers, fillers, or plasticized regions. 

We have seen (in Chapter 2) that both of the homopotymers potyetltylene (PE) and polypropylene (PP) are partially crystalline. The glass transitions of the amorphous fraction of PE is -12(TC and of PP —19°C Thus the glass transitions of the copolymers are eiqiected to be in the range -120°C up to -19°C the glass transitions of the copolymers of commercial interest lie in the range —S0°C to -S8°C. In this range of composition there is no ciystallinity. 

Copolymer of tetrafluoroethylene and perfluorinated co-components Partially crystalline 14.5... 

McGrath, Robeson, and Matzner investigated block copolymers and homopolymer-copolymer blends of bisphenol-A polysulfone and nylon-6 (7). They found improved ESCR as the content of the crystalline nylon-6 block increased. Similarly, Viswanathan, al. prepared random block copolymers of bisphenol-A pFTysulfone and the partially crystalline hydroquinone polysulfone (8). ESCR improved markedly as the hydroquinone content increased. However, while the copolymers "as made" are semicrystalline, the compression molded specimens used for ESCR studies are amorphous. Hence, recrystallization from the melt was quite slow. The improvement of ESCR is attributed to solvent-induced crystallization of the surface layers, which was presumed to restrict diffusion of the liquid into the bulk. 

Examples of polymers that have a piezoactive response are poled poly(vinylidene fluoride) (PVDF) (151) and its copolymers with trifluo-roethylene co(VDF-TrFE) (152), and the family of odd nylons (153) (see Piezoelectric Polymers). These are partially crystalline materials in which the crystalline regions have a permanent electric dipole moment. These polymers show ferroelectric switching behavior indicating that after poling they have a net... 

E/NB copolymers can be obtained as random amorphous materials with high TgS or as alternating, partially crystalline materials with high TmS. Amorphous copolymers have short blocks of norbornene units (dyads or triads), which account for their high TgS and excellent optical properties. All norbornene homo- and copolymers made by single site catalysts are characterized by narrow molecular weight distributions, which make technical processing easier. The first commercial norbornene copolymer products are already available. 

The period under review, January 1977 to December 1978, has seen much activity in the study of polymer crystallization and the properties of partially crystalline polymers. This partly reflects the impact of new and sophisticated developments in conventional spectroscopic techniques, and also developments in synthesis, fractionation, and characterization of polymers and copolymers. The subject is in a state of flux but many of today s apparent diiflculties and inconsistencies will be reconciled by the impact of these various and different techniques. Any attempt to achieve a definitive formulation is premature instead an attempt has been made to highlight some of the controversies which have engaged most interests in this period, supplying some background information to explain the difficulties in each case. 

Pomerantz et al. [49] showed that the molecular weight of this polymer, which was prepared from the chemical oxidation of an equimolar mixture of both monomers, is very high A/w = 4.42 x 10 and A/ = 1.59 x 10. Based on X-ray diffraction measurements. Fell and his co-workers [83] found a correlation between structure and composition of these copolymers. According to them, the samples are partially crystalline with structures intermediate between those of both homopolymers. In the crystalline area, stacks of thiophene chains, equally spaced by the side-chains, form a lamellar structure, and the distance between adjacent stacks varies linearly with the concentration of octylthiophene units in the copolymer. 

PREPARATIONS OF BLOCK COPOLYMERS BY CHEMICAL REACTIONS ON LAMELLAS OF PARTIALLY CRYSTALLINE FLEXIBLE POLYMERS... 

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