Factors affecting the optimal process range of rotational molding

doi:10.19491/j.issn.1001-9278.2025.03.013

Abstract

Abstract:

In this study， linear low⁃density polyethylene （PE⁃LLD） was selected as the substrate to prepare powder materials suitable for rotational molding process through melt blending using a twin⁃screw extruder， followed by processing with a mechanical mill. By controlling the feeding amount to control the thickness of the rotational molding products， five important factors were thoroughly investigated， which included the thickness of the rotational molding product， the melt flow rate （MFR） of the rotational molding material， the particle size distribution of the powder， the amount of carbon black added， and the furnace temperature of the rotational molding equipment. A systematic analysis was conducted on the minimum peak internal air temperature （PIATP） required to eliminate the pores in the product wall during the rotational molding process， the minimum peak internal air temperature （PIATI） required to achieve a yellowing index of 0 on the inner surface of the product， the optimal process interval （BPI） for rotational molding， and the comprehensive effects of low⁃temperature drop hammer impact strength （LTIS） within this interval. The results indicate that the temperature for eliminating pores was significantly reduced with an increase in the thickness and MFR of rotational molding products， and the BPI of rotational molding was significantly widened. Meanwhile， LTIS was improved with an increase in the thickness. A decrease in the particle size of powder material led to an increase in PIATP but a decrease in PIATI， narrowing the BPI range during rotational molding. The effect of carbon black on the range of PIATP， PIATI， and BPI was less. Moreover， the matrix LTIS slightly increased with an increase in the addition amount of carbon black. The increase of the furnace temperature of the rotational molding equipment resulted in a slow increase in PIATP but significant increase in PIATI， consequently expanding the range of rotational molding BPI.

Key words: rotational molding, the optimal process range for rotational molding, porosity, yellowing index, low temperature drop hammer impact strength, influence factor

CLC Number:

TQ325.1⁺2

CHEN Yeru, GUO Deyu, WEN Yuan. Factors affecting the optimal process range of rotational molding[J]. China Plastics, 2025, 39(3): 71-76.

Figures/Tables 9

样品编号	DFDA7042 质量分数/%	DNDA8320 质量分数/%	MFR/ g·（10 min）^-1
1^#	100	0	2.0
2^#	60	40	4.4
3^#	45	55	6.2
4^#	35	65	8.0
5^#	30	70	10.3
6^#	10	90	15.3

Tab.1. Mass fractions of various components in different MFR composite materials

Fig.1. Image of Cross Sectional Pores

Fig.2. The effect of product thickness on the optimal process range of PIATP， PIATI， and rotational molding

Fig.3. The effect of product thickness on low⁃temperature drop weight impact strength

Fig.4. The effect of melt flow rate on the optimal processing range of PIATP， PIATI， and rotational molding

粉体粒径/μm

PIATP/

℃

PIATI/

℃

滚塑最佳

工艺区间/℃

低温落锤

冲击强度/J·mm^-1

Tab.2. The effect of powder particle size distribution on the optimal process range of PIATP， PIATI， and rotational molding， as well as on low⁃temperature ductile⁃brittle transition impact strength

Fig.5. The effect of carbon black content on the optimal processing range of PIATP， PIATI， and rotational molding

Fig.6. The effect of carbon black content on low temperature ductile⁃brittle transition impact strength

滚塑设备炉温/℃	PIATP/℃	PEHT/s	PIATI/℃	滚塑最佳工艺区间/℃	YIHT/s	低温落锤冲击强度/J·mm^-1
260.0	225.0	1 110	239.4	14.4	1 284	27.2
270.0	230.1	1 032	247.2	17.1	1 080	27.7
280.0	231.4	942	252.3	20.9	1 062	28.9
290.0	234.2	888	256.2	22.0	1 026	27.9

Tab.3. The effect of rotational molding equipment oven temperature on the optimal process range and low⁃temperature Izod impact strength of PIATP， PIATI， and rotational molding

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