Presence Of Copolymer Research Articles

Effects of poly(methyl methacrylate‐co‐n‐butyl acrylate) on the properties and processing behavior of poly(vinyl chloride)

AbstractRandom copolymers of methyl methacrylate/n‐butyl acrylate with a BA content of 0–50% and M̄v = 0.16–4.04 × 106 were synthesized and evaluated as a processing aid (PA) for poly(vinyl chloride) (PVC). Their effects on the processability and properties of PVC were investigated with respect to the composition, molecular weight, and the amount of the copolymer added. It was found that the fusion rate of PVC could be improved (i) by increasing the amount of the copolymer used, (ii) by increasing the butyl acrylate content in the copolymer, and (iii) by lowering the molecular weight of the copolymer. The effect of molecular weight, composition, and amount of copolymer on the ultimate mechanical properties of PVC was investigated. The presence of copolymer did not affect the impact strength. However, the tensile strength and elongation at break were improved, particularly at high temperature (125°C). It was also found that the “plate out” phenomenon of PVC could be significantly reduced in the presence of the processing aid.

THE EFFECT OF POLYMERS HAVING ULTRAVIOLET ABSORPTIVE GROUPS ON PHOTOFADING RATE OF ACRIDINE ORANGE N

The photofading of Acridine Orange N in dioxane-ethanol mixture has been studied in the presence of copolymers having 2-hydroxybenzophenone (HBP) group as a ultraviolet absorptive group on the polymer side-chain, 2-hydroxy-4-(3-methacryloxy-2-hydroxypropoxy)-benzophenone (BPMA) homopolymer, polystyrene (PSt), polymethyl methacrylate (PMMA) and 2-hydroxy-4-methoxybenzophenone (HMBP).PSB was obtained by copolymerization of styrene (St) with BPMA, and PMB also obtained by copolymerization of methyl methacrylate with BPMA. PSB contained St unit (main-chain) and HBP unit (8.9_??_14.2%), and PMB contained MMA unit (main-chain) and HBP unit (3.7_??_7.2%), while BPMA homopolymer (PBPMA) contained 100% HBP unit.The results of photofading of Acridine Orange N in the solutions containing these polymers or DHBP are summarised as follows. PSB, PMB, PBPMA and HMBP played roles of retarder on the photofading rate of the dye, with the effects in the following order: PSB>PBPMA>HMBP>PMB.A slight retardation effect was also observed with PSt, while PMMA acted as an accelerator. From these results it is reasonably concluded that the differences in the dye protective behaviors for light between PSB and PMB must be associated with the structural features, in particular, in the main-chain of these polymers.The fading of the dye was more marked with light in the wavelength region of 300_??_400nm than in the wavelengths >400nm, and the retarding action of HBP group was remarkably observed with 300_??_400nm light.Stern-Volmer plot (see Fig. 5) showed that HBP group acts as quenchers in the case of the low concentration of these additives.

The solvent effect on radical copolymerization of ethylene with vinyl acetate

The copolymerization of ethylene with vinyl acetate under 25 MPa pressure at 383°K has been studied in different solvents. The constants for chain transfer to the solvent were determined for the entire range being studied. It was shown that the solvent concentration in the reaction mixture has a substantial effect on the copolymerization rate and copolymer yield. The overall copolymerization rate was determined in different solvents. The effect of the solvent on the mechanism of chain termination was studied. The order of reaction was determined in respect of initiator concentration for three solvents. It was shown that the reaction system under the conditions of study, in presence of copolymer, is a heterophase one.

Radical polymerization of methacrylic acid in the presence of copolymers of 4-vinylpyridine in methanol

Random copolymers of 4-vinylpyridine (4VP) with styrene and with acrylamide were effective to enhance the overall rate of radical polymerization of methacrylic acid(MA) in methanol. The rate maximum did not occur at the equimolar ratio of 4VP unit/MA but it depended on the copolymer composition.

Hydrolysis of dextrin in the presence of block copolymer of vinyl alcohol and styrenesulfonic acid

AbstractA block copolymer of vinyl alcohol and styrenesulfonic acid was prepared by a two‐step polymerization and subsequent modification, and its catalytic activity on the hydrolysis of dextrin was investigated. The hydrolysis rate in the presence of the copolymer containing more vinyl alcohol‐repeating units was found to follow Michaelis–Menten‐type kinetics, whereas that in the presence of a copolymer containing fewer vinyl alcohol units proceeded according to ordinary second‐order kinetics. The process of complex formation for the former system was characterized by pronounced decreases in enthalpy and entropy, although the enthalpy and the entropy of activation for the decomposition of the complex to product was comparable to that of a sulfuric acid‐catalyzed system. The maximum rate enhancement obtained in the present experiment was approximately fivefold on the basis of the reaction in the presence of sulfuric acid at 65°C. The results were compared with those obtained in the presence of a random copolymer catalyst, previously reported.

Kinetics of the deactivation of propagation centres during the copolymerization of ethylene and propylene in the presence of non-equilibrium catalysts based on vanadium oxychloride

The copolymerization of ethylene and propylene in the presence of “non-equilibrium” catalyst systems was investigated. The copolymerization of the monomers proceeds on propagation centres of a single type which are subject to deactivation simultaneously through bimolecular and monomolecular laws with the former greatly predominating. The proposed new equations describe the kinetic regularities of ethylene-propylene copolymerization in presence of non-equilibrium catalysts based on VOCl 3 and organoaluminium compounds.

Radical reactions initiated by chelate complexes of transition metals. III. Grafting of polymers containing halogen atoms

AbstractPolymerization of styrene is initiated by bis‐(–)ephedrine copper(II) chelate in presence of halopolymers and telomers containing terminal halogen atoms. The rate of polymerization at constant concentration of the chelate depends on the specific halopolymer used and its concentration i.e. on the concentration of halogen atoms in the polymerization system. It is suggested that initiation results from interaction of the chelate with the halogen atoms of the halopolymer leading to formation of reactive centres at the halopolymer. These centres are able to give rise to formation of graft and block copolymers in presence of suitable vinyl monomers.