The Study On The Performance Of The Composites Of PE/PP

The Ultra-high modulus PE(UHMPE) is a high performance fiber, namely the third after carbon fiber and Metamax fiber. It not only has the highest specific-modulus and specific-strengths in the present high performance fibers, but also has preponderant advantages, such as, good abrasion resistance, impact resistance, chemicals resistance, bio-confluent, thermal behaviors, water rejection and light specific gravity. Therefore, the UHMPE fiber and its composites are going to have wide application foreground, including living of people, military affairs, medical treatments, physical trainings, earthworks and so on. Because PE, the raw material, is easy to get, if it is produced largely, the operating costs must be reduced. In a word, the composites, which are reinforced by the UHMPE fibers, have up-and-coming competitors in many fields.This paper studied the tensile strength performances and the thermal behaviors for the two kinds of composites (LDPE/UHMPE and PP/UHMPE). The relations between the performances and the surface crystallization and the relations between the mechanical performances of the enforced composites and the moulding parameters (temperature, time, pressure) and their interactions would be found by test and analysis.Based on the preparation experimentations, the unilateral fiber enforced composites of LDPE(matrix material)/UHMPE(enforced fiber)and PP(matrix material)/UHMPE(enforced fiber) are manufactured. L27(33) and L16(215) orthogonal designs which are corresponding with the composites of the LDPE/UHMPE and the PP/UHMPE are applied in the experimentations. By testing the longitudinal and transverse tensile strengths of the experiment samples, these data are analyzed by analysis of variance method in the orthogonal arrays. The effect between themechanical performance of the enforced composites and the moulding parameters (temperature, time, pressure) and their interactions are also analyzed in this paper. The thermal behaviors of the composites are studied through the Differential Scanning Calorimetry (DSC) and the Dynamic Mechanical Analysis (DMA) test. The microcosmic configuration of the samples on cross-section are shown in the pictures of the SEM .Based on the experimentations tests and analysis, the conclusions are as fellows:1 For the composites of LDPE/UHMPE, the influences of the moulding parameters and their interactions on the transverse tensile strengths performances are not remarkable. For the longitudinal tensile strengths performances, they are affected highly remarkably by the moulding temperature, then are the interactions between moulding temperature and moulding pressure, the last are the interactions between moulding temperature and moulding time.2. For the composites of PP/UHMPE, it is remarkable that the influences of the interactions between moulding temperature and moulding pressure on the transverse tensile strengths performances. The interactions between moulding temperature and moulding time have also a highly remarkable influence on the longitudinal tensile strengths performance. Correspondingly, it is more obvious that the longitudinal tensile strengths performances are affected by the moulding parameters than transverse ones.3. By comparing the composites of LDPE/UHMPE with the composites of PP/UHMPE, the former has the better processing performances and the latter is limited in the scope of the moulding parameter.4. There is the symbiotic crystal structure to be found in the twocomposites. By analyzing two composites, the conclusions can be obtained. That is, there are some relations between the forming of the symbiotic crystal structure and the moulding parameters. Within the certain temperature range, when the moulding temperature is more close to the middle point of the melting point of the based material and enforced fiber, the possibility of forming the symbiotic crystal is higher and its proportion in the composites is higher. There are som...