Study on Modification and Foaming Properties of PP Through PETA/St Double‑Monomer Reactive Extrusion

doi:10.19491/j.issn.1001-9278.2020.07.001

Abstract

Abstract:

A series of long?chain branched PP compounds were prepared by double?monomer reactive extrusion of conventional isotactic polypropylene with pentaerythriol triacrylate (PETA) and Styrene (St), their faomability was characterized with FTIR, DSC and rheology tests, and their foam structure was observed with SEM. The results indicated that for the modified PP samples without crosslinking structure, the PP compound with 2 wt% of PETA and 3 wt% of St exhibited the optimum comprehensive performance. Meanwhile, the PP compounds showed a different strain hardening behaviors because of the different branching structure. The batch melt foaming experiment was conducted to evaluate the melt foamability of PP compounds with CO₂ as the foaming agent. It was found that the PP compounds with a long branching structure had a better melt foamability, and the the PP samples showed a foaming window temperature of 25 ℃ after grafted with PETA/St double monomers. The resulting PP foams achieved a maximum expansion ratio of 33, an average diameter of 36 μm, and a cell density of 3.17×10⁸ cells/cm³.

Key words: long branching sturcture, modified polypropylene, rheology property, foaming

CLC Number:

TQ325.1⁺4

Tianhao GUO, Yiquan LU, Tao LIU, Ling ZHAO. Study on Modification and Foaming Properties of PP Through PETA/St Double‑Monomer Reactive Extrusion[J]. China Plastics, 2020, 34(7): 1-9.

Figures/Tables 13

样品编号	原料添加量
样品编号	DCP	PETA	St	抗氧剂1010
PP1	—	—	—	—
PP2	0.2	2	—	0.1
PP3	0.2	—	3	0.1
PP4	0.2	2	3	0.1

Tab.1. Experimental formulation of the modified PP

Fig.1. Possible molecular reaction mechanism

Fig.2. FTIR spectra of the iPP and modified samples

Fig.3. MWD curves of iPP and modified PP samples

样品	MFR/ g·(10 min)^-1	M_w/ kg·mol^-1	M_n/ kg·mol^-1	M_W/M_n	η₀/Pa·s
PP1	3.493	403.75	69.03	5.85	2 800
PP2	3.191	436.12	65.98	6.61	5 040
PP3	2.015	460.63	74.61	6.17	40 509
PP4	1.672	485.42	90.23	5.38	66 812

Tab.2. Physical parameters of iPP and modified PP samples

Fig.4. Melting and crystallation curves of the iPP and modified PP samples

样品	T_m/℃	T_c,onset/ ℃	T_c/℃	ΔH_f/ J·g^-1	X_c/%	k′	t_1/2/min	n	R²
PP1	167.0	125	112.0	72.12	34.51	0.85	1.38	3.83	0.982 6
PP2	165.5	132	122.0	65.98	31.57	0.93	0.97	3.16	0.995 0
PP3	166.5	130	119.5	64.07	30.66	0.91	0.98	3.50	0.998 2
PP4	166.0	136	128.0	63.29	30.28	0.99	0.88	2.76	0.995 6

Tab.3. DSC parameters of iPP and modified PP samples

Fig.5. Rheological behavior of the iPP and modified PP samples

Fig.6. Cole?cole plot, Han plot and relaxation time spectra of the iPP and modified PP samples

Fig.7. Elongational viscosity of the iPP and modified PP samples

Fig.8. SEM images of iPP and modified PP foams at 145 ℃ and CO2 pressure of 15 MPa

Fig.9. SEM images of PP?g?PETA/St foams at 15 MPa CO2 and different temperature

Fig.10. Characterization of PP?g?PETA/St foams at 15 MPa CO2 and different temperatures

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