The Preparation And Characterization Of HDPE/E-TMB

High Density Polyethylene (HDPE) have been widely used as general plastics. It is a new approach for developing new engineering plastics to make HDPE vise in engineering fields. But toughness of HDPE could not be satisfied. In order to meet the demands of engineering fields , it is necessary to toughen HDPE.In the recent years many researches have made a lot of study on the toughening HDPE. In contrast with other methods, toughening effects are the best when using elastomer as toughening agents. But toughnees often evidently improves with rigidity (Tensile Yield Stress, TYS; Flexural Modulus, FM) decreasing sharply. It is a difficult problem to make rigidity do not decreases to a large degree with toughnees improving remarkably.The reasons for decreasing of rigidity could be summarized as follows: (l)The compatibility between HDPE and elastomer is badly because HDPE tend to crystalline. (2)Elastomer as the dispersed phase are not crosslinked in moderation. The molecule chains are easy to surge under the action of outside force. (3)In order to improving toughness to a large degree, the mass content of elastmer must be increased. So the component of low rigidity is too much.Based on the theory of elastomer toughened plastics and the law of the influence which factors act on toughening effects, We design a kind of structure: the HDPE is as the continuous phase and the crosslinked elastomer as the dispersed phase. Two phases are connected with through the polymer bridge. The dispersed phase have a typical cellular structure(salami structure).We choose elastomers as toughening agents. A series of high desity polyethylene engineering plastics having higher rigidity and highly improved toughness were prepared through thermal mechanical blending HDPE with E toughening master batch (E-TMB) synthesized from HDPE as matrix resin. ethylene-propylene elastomer(M) and(or) butadiene-styrene elastomer(N) as toughening agents. The chemical structure and morphology of E-TMBs, and themechanical and rheological properties, morphology and crystallization behavior of the HDPE/E-TMBs were characterized by using fraction extraction, TEM, DSC, TG. PLM techniques as well as an electronic universal testing machine and a rheometer etc.From the experiment data, it was found that:(1) The structure of E-TMBs and HDPE/E-TMB is uniform with that we designed in advance. HDPE/E-TMB show much better NIIS, maintained much higher TYS and FM compared with simply blended samples (HDPE/elastomer).(2) The MFR of E-TMB is lower than that of simply blended samples, but it is still in the range of MFR fitting for preparing HDPE/E-TMB.(3) when using E-TMB with H:T=56:44,M/N=80/20, anti-crosslinking agent and bridge agent is 1.9% and 12%, and when elastomer content of HDPE/E-TMB is 8%, the 2200JHDPE/E-TMB shows excellent balanced mechanical properties: Notched Izod impact strength is 8.5 times of that of HDPE, TYS and FM is 87% and 70% of that of HDPE. when using E-TMB with H:T=64:36,M/N=0/100, anti-crosslinking agent and bridge agent is 1.9% and 12%, and when elastomer content of HDPE/E-TMB is 8%, the 5000SHDPE/E-TMB shows excellent balanced mechanical properties: Notched Izod impact strength is 76.6 KJ/m2, TYS and FM is 98% and 82% of that of HDPE.(4) When elastomer content in 2911 HDPE/E-TMB is 10%, a brittle-ductile transition occurred in toughened HDPE. This transition occurred in 2200JHDPE/E-TMB when elastomer content in toughened HDPE is 5%. However. This transition don't occurred in toughened 5000SHDPE .(5) The MFR of HDPE/E-TMB was lower than that of HDPE/elastomer, but it was still in the range of MFR fitting for injection and extrusion molding. Under ordinary sheer flow conditions, the HDPE/E-TMB melt showed a pseudo-plastic feature. The linear relationship between η a and T of the HDPE/ E-TMB melts was similar to In η a and 1/T. The HDPE/ E-TMB melt could be expressed by η a = A + KT, by which the physical nature of the temperature coefficient of apparent viscosity would be more specific.(6) The elastomer have a double influence on the crystallization of HDPE. When elastomer content is lower, The crystallization temperature is higher than that of HDPE because of nucleated heterogeneously. The crystal size was remarkably reduced. When elastomer content is higher, The crystallization temperature is higher than that of HDPE because of impeditive effect.