Influence of Processing Parameters on Wall Thickness and Properties of Water⁃assisted Co⁃injection Molding Pipes of Polypropylene/Polyamide 6 Blends

doi:10.19491/j.issn.1001-9278.2021.11.012

Abstract

Abstract:

Based on the custom-designed experimental platform of water-assisted co?injection molding， a series of injection-molded pipes were obtained from an orthogonal experiment. The influence of processing parameters on the wall thickness， tensile properties and crystallization of each layer of the pipes were investigate. The results indicated that the outer wall thickness of the pipes decreased with an increase in the outer melt temperature， water injection pressure， inner melt injection pressure， and mold temperature but increased with an increases in melt injection delay time and water injection delay time. Their inner wall thickness increased with an increase in water injection delay time and inner melt injection pressure but decreased with an increase in water injection pressure and mold temperature. The pipes also presented a decrease in tensile strength of decreases with an increase in outer melt temperature， and however， their tensile strength increased with an increase in melt injection delay time and water injection delay time. The processing parameters generated direct influences on the residual wall thickness and the cooling process of the pipes， affecting the crystallinity of each phase and pipe performance accordingly.

Key words: blend, water assisted co-injection molding, residual wall thickness, tensile strength, crystallinity

CLC Number:

TQ 320.66

YUAN Zhihuan, KUANG Tangqing, LAI Jiamei, LIU Hesheng, XU Pan. Influence of Processing Parameters on Wall Thickness and Properties of Water⁃assisted Co⁃injection Molding Pipes of Polypropylene/Polyamide 6 Blends[J]. China Plastics, 2021, 35(11): 77-83.

Figures/Tables 10

水平	因素
水平	A	B	C	D	E	F
1	220（A₁）	1（B₁）	1（C₁）	6（D₁）	6（E₁）	25（F₁）
2	230（A₂）	3（B₂）	4（C₂）	7（D₂）	7（E₂）	40（F₂）
3	240（A₃）	5（B₃）	7（C₃）	8（D₃）	8（E₃）	55（F₃）
4	250（A₄）	7（B₄）	10（C₄）	9（D₄）	9（E₄）	70（F₄）
5	260（A₅）	9（B₅）	13（C₅）	10（D₅）	10（E₅）	85（F₅）

Tab.1. Influence factors and their levels

Fig.1. Measurement locations along the flow direction

Fig.2. Measurement locations of cross section

Fig.3. Specimen for DSC analysis

实验编号	因素						结果
实验编号	A	B	C	D	E	F	内层壁厚/mm	外层壁厚/mm	最大拉伸载荷/N	拉伸强度/MPa
1	A₁	B₁	C₁	D₁	E₁	F₁	0.90	2.34	3 677.33	28.35
2	A₁	B₂	C₂	D₂	E₂	F₂	1.08	2.16	4 474.84	34.43
3	A₁	B₃	C₃	D₃	E₃	F₃	1.11	2.23	4 529.64	34.11
4	A₁	B₄	C₄	D₄	E₄	F₄	1.05	2.25	4 156.99	31.55
5	A₁	B₅	C₅	D₅	E₅	F₅	1.24	2.19	4 896.48	36.13
6	A₂	B₁	C₂	D₃	E₄	F₅	0.62	2.21	3 867.67	33.01
7	A₂	B₂	C₃	D₄	E₅	F₁	1.27	2.14	4 270.63	31.64
8	A₂	B₃	C₄	D₅	E₁	F₂	1.00	2.46	4 680.32	34.35
9	A₂	B₄	C₅	D₁	E₂	F₃	1.26	2.45	4 635.77	32.35
10	A₂	B₅	C₁	D₂	E₃	F₄	1.18	2.07	4 239.00	32.58
11	A₃	B₁	C₃	D₅	E₂	F₄	0.90	2.00	3 767.89	31.54
12	A₃	B₂	C₄	D₁	E₃	F₅	1.25	2.09	4 150.07	31.22
13	A₃	B₃	C₅	D₂	E₄	F₁	1.32	2.28	4 566.39	32.58
14	A₃	B₄	C₁	D₃	E₅	F₂	1.05	1.78	4 208.53	35.98
15	A₃	B₅	C₂	D₄	E₁	F₃	0.82	2.26	4 196.64	33.58
16	A₄	B₁	C₄	D₂	E₅	F₃	1.13	1.75	3 975.61	33.47
17	A₄	B₂	C₅	D₃	E₁	F₄	0.94	2.15	4 173.42	33.29
18	A₄	B₃	C₁	D₄	E₂	F₅	0.90	1.84	3 198.68	28.04
19	A₄	B₄	C₂	D₅	E₃	F₁	0.99	2.04	3 802.66	30.80
20	A₄	B₅	C₃	D₁	E₄	F₂	1.18	2.23	3 930.77	29.12
21	A₅	B₁	C₅	D₄	E₃	F₂	1.10	2.00	3 461.48	27.56
22	A₅	B₂	C₁	D₅	E₄	F₃	0.97	1.65	2 674.58	24.27
23	A₅	B₃	C₂	D₁	E₅	F₄	1.22	1.92	3 727.16	29.37
24	A₅	B₄	C₃	D₂	E₁	F₅	1.08	2.09	3 863.85	30.24
25	A₅	B₅	C₄	D₃	E₂	F₁	1.06	2.12	4 414.04	34.45

Tab.2. Experiment scheme and results of RWTs and tensile strength

因素		A	B	C	D	E	F
外层壁厚	$K -$ ₁	2.23	2.06	1.94	2.21	2.26	2.18
	$K -$ ₂	2.27	2.04	2.12	2.07	2.11	2.13
	$K -$ ₃	2.08	2.15	2.14	2.10	2.09	2.07
	$K -$ ₅	2.00	2.12	2.13	2.10	2.12	2.08
	$K -$ ₆	1.96	2.17	2.21	2.07	1.96	2.08
	R	0.31	0.13	0.27	0.14	0.30	0.11
内层壁厚	$K -$ ₁	1.08	0.93	1.00	1.16	0.95	1.11
	$K -$ ₂	1.07	1.10	0.95	1.16	1.04	1.08
	$K -$ ₃	1.07	1.11	1.11	0.96	1.13	1.06
	$K -$ ₄	1.03	1.09	1.10	1.03	1.03	1.06
	$K -$ ₅	1.09	1.10	1.17	1.02	1.18	1.02
	R	0.06	0.18	0.22	0.20	0.23	0.09

因素		A	B	C	D	E	F
外层壁厚	$K -$ ₁	2.23	2.06	1.94	2.21	2.26	2.18
	$K -$ ₂	2.27	2.04	2.12	2.07	2.11	2.13
	$K -$ ₃	2.08	2.15	2.14	2.10	2.09	2.07
	$K -$ ₅	2.00	2.12	2.13	2.10	2.12	2.08
	$K -$ ₆	1.96	2.17	2.21	2.07	1.96	2.08
	R	0.31	0.13	0.27	0.14	0.30	0.11
内层壁厚	$K -$ ₁	1.08	0.93	1.00	1.16	0.95	1.11
	$K -$ ₂	1.07	1.10	0.95	1.16	1.04	1.08
	$K -$ ₃	1.07	1.11	1.11	0.96	1.13	1.06
	$K -$ ₄	1.03	1.09	1.10	1.03	1.03	1.06
	$K -$ ₅	1.09	1.10	1.17	1.02	1.18	1.02
	R	0.06	0.18	0.22	0.20	0.23	0.09

Tab.3. Range analysis of RWTs

Fig.4. Effects of processing parameters on the RWTs of WACIM pipe

项目	A	B	C	D	E	F
$K -$ ₁	32.91	30.79	29.84	30.08	31.96	31.56
$K -$ ₂	32.79	30.97	32.24	32.66	32.16	32.29
$K -$ ₃	32.98	31.69	31.33	34.17	31.25	31.56
$K -$ ₄	30.94	32.18	33.01	30.47	30.11	31.67
$K -$ ₅	29.18	33.17	32.38	31.42	33.32	31.73
R	3.80	2.38	3.17	4.09	3.21	0.73

项目	A	B	C	D	E	F
$K -$ ₁	32.91	30.79	29.84	30.08	31.96	31.56
$K -$ ₂	32.79	30.97	32.24	32.66	32.16	32.29
$K -$ ₃	32.98	31.69	31.33	34.17	31.25	31.56
$K -$ ₄	30.94	32.18	33.01	30.47	30.11	31.67
$K -$ ₅	29.18	33.17	32.38	31.42	33.32	31.73
R	3.80	2.38	3.17	4.09	3.21	0.73

Tab.4. Range analysis of tensile strength

Fig.5. Effects of processing parameters on the tensile strength of WACIM pipe

试样	成型条件	位置		结晶度/%
试样	成型条件	位置		PP	PA6
拉伸强度最大试样（5号）	外层熔体温度220 ℃、模具温度85 ℃	外层	I	14.80	2.26
			II	11.36	1.83
			III	7.27	0.4
		内层	IV	5.27	-
			V	15.13	-
			VI	11.06	-
拉伸强度最小试样（22号）	外层熔体温度260 ℃、模具温度55 ℃	外层	I	8.66	1.09
			II	8.20	1.76
			III	11.09	0.21
		内层	IV	16.81	-
			V	18.71	-
			VI	11.08	-

Tab.5. Forming conditions and crystallinity distribution of the samples with maximum and minimum tensile strength

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