The Studies On Thermally Reversible Covalent Crosslinking Of Chlorine-Containing Polymers And Preprations Of Thermoplastic Elastomers Bsaed Them

It is well known that thermoplastic elastomer(TPE) can be easily processing by means of the processing methods of general plastic materials. Therefore, TPEs have been developed fast in the past decades. However, compared with thermosetting rubbers, most TPEs still have many disadvantages, for example, low mechanical properties, great creep deformation, low heat resistant, due to their crosslinked linkage and sites are based on physical or ionic crosslinkage. To find a new kind of crosslinking reaction method in order to improve their performance is a very important research title. By using the thermal reversibility between cyclopentadiene and di-cyclopentadiene was one of the effecting way, which can form C - C covalent crosslinking bonds as in traditional vulcanized rubber.In this paper, the thermally reversible crosslinking reaction and the properties of synthesized TPE based on the reactions of chlorine containing polymers such as PVC , chlorined polyethylene (CPE ) , epichlorohydrin rubber(CER) and acrylic rubber(ACM) with salts of dicyclopenladienyl dicarboxylate crosslinking agents were studied. All the results are showed as follows:(1) Cyclopentadienyl sodium(CPDNa) was prepared successfully via reaction CPD with NaOH instead of Na, and the effects on CPDNa's yield were studied in detail, so the optimum reaction conditions were achieved. DCPD(COOH)2 was synthesized via the reaction of CC>2(gas) with CPDNa contrast to the method using solid COi- The effects on the product's yield and purity were also discussed. The salt derivatives of DCPD(COOH)2 was obtained by the reaction of DCPD(COOH)2 with KOH, NaOH, NH4C1 and metal oxides. The methods for fined crosslinker and the masterbatch of crosslinking agent were put forward.(2)The crosslinking reaction of PVC with DCPD(COOH)2 derivatives was studied by melting reaction, compression mold, and injection mold. The relations between the amount of the agent and crosslinking degree, mechanical property, heat resistent,thermal stability and pyrofluxibility were studied in detail. The results indicted that the crosslinking speed and degree of PVC with crosslinking agent can be prompted via ammonium catalyst, and polyethylene glycol was an excellent accelerator to this crosslinking reaction. The crosslinking products not only processed improved property and thermally reversible property, but can be reformed more than three times. The thermally reversible covalent bonded PVC-TPE with high performance soft PVC were obtained.(3) Potassium salt of dicyclopentadienyl dicarboxylate (DCPD(COOK)2 ) was applied to CPE as crosslinking agent and a crosslinked product with 81.79% gel content was obtained in solution reaction. The effects of kinds of CPE , catalysts and their dosage , temperature, reaction time and the dosage of crosslinking agent on the gel content were studied. It was proved by IR that the gel was generated through esterification between the chlorine-carbon of CPE and the carboxylic salt groups of the crosslinking agent. It was also important that the addition of phase transformation catalyst in CPE system. The crosslinked CPE exhibited thermally reversible behavior due to the dimmer (dicyclopentadiene) /monomer (cyclopentadidne) conversion of -DCPD- moieties via reversible Diels-Alder cycloaddition; The TRTPE's, based on CPE , mechanical properties such as tensile strength and elongation were closed to that of thermosetting CPE cured with normal vulcanizator. The TRTPE of CPE could be reformed for three times and the mechanical properties after reformation kept unchanged. .(4)The DCPD(COOK)2 was also used in ACM mixed system. The results showed that the new TPE with thermally reversible covalent bond were also obtained ,the gained TPE can be reformed for three times and its mechanical properties after reformmation kept uncharged. Therefore a industrialized method with few equipment and simple procedure was developed.In a word, all the studies in this paper established a new crosslinking method to improve the PVC's property and to prepare a new class...